Tag: IAU

Recent arXiv:astro-ph Picks: December 2024

Here are some recent submissions on astro-ph that I found to be especially interesting. Text excerpts below are quoted directly from the articles. My comments are in italics.

Short-Term Evolution and Risks of Debris Cloud Stemming from Collisions in Geostationary Orbit
https://arxiv.org/abs/2412.13586

The geostationary orbit is a popular orbit for communication, meteorological, and navigation satellites due to its apparent motionless. Nearly all geostationary satellites are positioned in a circular orbit with a radius of 42,164 km, making this region particularly vulnerable to space traffic accidents due to the high concentration of objects and the absence of natural debris-clearing mechanisms. The growing population in geostationary region raises concerns about the potential risks posed by fragments stemming from explosions and collisions, particularly following the breakup of Intelsat-33e, which remained operational in geostationary orbit until October 19, 2024.

A breakup event generates a large number of fragments of varying sizes. In the geostationary region, only fragments larger than 1 meter are routinely tracked by the Space Surveillance Network, as the sensitivity of ground-based sensors decreases significantly with distance. However, small, non-trackable fragments can still cause catastrophic damage to spacecraft. The collision velocity of spacecraft in geostationary orbit can reach up to 4 km/s, while micro-meteoroids may hit at speeds of up to 72 km/s.

The impact of a debris cloud is inherently global as it disperses around the entire Earth.

By 2024, over 1,000 objects have been observed near the geostationary orbit (GEO). Nearly all objects exhibit inclinations of less than 15 degrees, with the majority having inclinations of less than 1 degree. Once a fragmentation event occurs, the GEO objects will be exposed to considerable risks, as they are densely clustered along a single ring above the Equator.

More about Intelsat 33e and its breakup:
https://en.wikipedia.org/wiki/Intelsat_33e

Sun-like stars produce superflares roughly once per century
https://arxiv.org/abs/2412.12265

Stellar superflares are energetic outbursts of electromagnetic radiation, similar to solar flares but releasing more energy, up to 1036 erg on main sequence stars. It is unknown whether the Sun can generate superflares, and if so, how often they might occur. We used photometry from the Kepler space observatory to investigate superflares on other stars with Sun-like fundamental parameters. We identified 2889 superflares on 2527 Sun-like stars, out of 56450 observed. This detection rate indicates that superflares with energies >1034 erg occur roughly once per century on stars with Sun-like temperature and variability. The resulting stellar superflare frequency-energy distribution is consistent with an extrapolation of the Sun’s flare distribution to higher energies, so we suggest that both are generated by the same physical mechanism.

Solar flares are sudden local bursts of bright electromagnetic emission from the Sun, which release a large amount of energy within a short interval of time. The increase in short-wavelength solar radiation during flares influences the Earth’s upper atmosphere and ionosphere, sometimes causing radio blackouts and ionosphere density changes. Solar flares are frequently accompanied by the expulsion of large volumes of plasma, known as coronal mass ejections (CMEs), which accelerate charged particles to high energies. When these solar energetic particles (SEPs) reach Earth, they cause radiation hazards to spacecraft, aircraft and humans. Extreme SEP events can produce isotopes, called cosmogenic isotopes, which form when high-energy particles interact with the Earth’s atmosphere. These isotopes are then recorded in natural archives, such as tree rings and ice cores. The total amount of energy released by each flare varies by many orders of magnitude, as determined by a complex interplay between the physical mechanisms of particle acceleration and plasma heating in the Sun’s
atmosphere.

Solar flares have been observed for less than two centuries. Although thousands of them have been detected and measured, only about a dozen are known to have exceeded a bolometric (integrated over all wavelengths) energy of 1032 erg. Among them was the Carrington Event on 1 September 1859, which was accompanied by a CME that had the strongest recorded impact on Earth. Modern estimates of the Carrington Event’s total bolometric energy are 4 × 1032 to 6 × 1032 erg.

It is unknown whether the Sun can unleash flares with even higher energies, often referred to as superflares, and if so, how frequently that could happen. The period of direct solar observations is too short to reach any firm conclusions. There are two indirect methods to investigate the potential for more intense flares on the Sun. One method uses extreme SEP events recorded in cosmogenic isotope data, which have been used to quantify the occurrence rate of strong CMEs reaching Earth over the past few millennia. There are five confirmed (and three candidate) extreme SEP events that are known to have occurred in the last 10,000 yr, implying a mean occurrence rate of ∼ 10−3 yr−1. However, the relationship between SEPs and flares is poorly understood, especially for the stronger events.

A second method is to study superflares on stars similar to the Sun. If the properties of the observed stars sufficiently match the Sun, the superflare occurrence rate on those stars can be used to estimate the rate on the Sun.

We found that Sun-like stars produce superflares with bolometric energies > 1034 erg roughly once per century. That is more than an order of magnitude more energetic than any solar flare recorded during the space age, about sixty years. Between 1996 and 2012 twelve solar flares had bolometric energies > 1032 erg, but none were > 1033 erg. The most powerful solar flare recorded occurred on 28 October 2003, with an estimated bolometric energy of 7 × 1032 erg, which exceeds estimates for the Carrington Event (4 × 1032 to 6 × 1032 erg).

We cannot exclude the possibility that there is an inherent difference between flaring and non-flaring stars that was not accounted for by our selection criteria. If so, the flaring stars in the Kepler observations would not be representative of the Sun. Approximately 30% of flaring stars are known to have a binary companion. Flares in those systems might originate on the companion star or be triggered by tidal interactions. If instead our sample of Sun-like stars is representative of the Sun’s future behavior, it is substantially more likely to produce a superflare than was previously thought.

More about the Carrington Event:
https://en.wikipedia.org/wiki/Carrington_Event

ChronoFlow: A Data-Driven Model for Gyrochronology
https://arxiv.org/abs/2412.12244

Gyrochronology is a technique for constraining stellar ages using rotation periods, which change over a star’s main sequence lifetime due to magnetic braking. This technique shows promise for main sequence FGKM stars, where other methods are imprecise. However, models have historically struggled to capture the observed rotational dispersion in stellar populations. To properly understand this complexity, we have assembled the largest standardized data catalog of rotators in open clusters to date, consisting of ~7,400 stars across 30 open clusters/associations spanning ages of 1.5 Myr to 4 Gyr.

Stars in open clusters are all about the same age, so this is highly useful in training models that use stellar rotation periods to determine stellar age.
https://en.wikipedia.org/wiki/Gyrochronology

On The Lunar Origin of Near-Earth Asteroid 2024 PT5
https://arxiv.org/abs/2412.10264

The Near-Earth Asteroid (NEA) 2024 PT5 is on an Earth-like orbit which remained in Earth’s immediate vicinity for several months at the end of 2024. PT5’s orbit is challenging to populate with asteroids originating from the Main Belt and is more commonly associated with rocket bodies mistakenly identified as natural objects or with debris ejected from impacts on the Moon. We obtained visible and near-infrared reflectance spectra of PT5 with the Lowell Discovery Telescope and NASA Infrared Telescope Facility on 2024 August 16. The combined reflectance spectrum matches lunar samples but does not match any known asteroid types—it is pyroxene-rich while asteroids of comparable spectral redness are olivine-rich. Moreover, the amount of solar radiation pressure observed on the PT5 trajectory is orders of magnitude lower than what would be expected for an artificial object. We therefore conclude that 2024 PT5 is ejecta from an impact on the Moon, thus making PT5 the second NEA suggested to be sourced from the surface of the Moon. While one object might be an outlier, two suggest that there is an underlying population to be characterized. Long-term predictions of the position of 2024 PT5 are challenging due to the slow Earth encounters characteristic of objects in these orbits. A population of near-Earth objects which are sourced by the Moon would be important to characterize for understanding how impacts work on our nearest neighbor and for identifying the source regions of asteroids and meteorites from this under-studied population of objects on very Earth-like orbits.

Perhaps the most significant conclusion to finding a second near-Earth object with an apparently Moon-like surface composition is the realization of lunar ejecta as a genuine population of objects. The Quasi-Satellite Kamo‘oalewa has a slightly redder spectrum than 2024 PT5, but the higher quality of our data at longer wavelengths (the Quasi-Satellite was significantly dimmer, so only photometry was obtained beyond ≈ 1.25μm) makes a discussion of how different the two spectra are only qualitative. At the very least, the two lunar NEOs do not look identical. Sharkey et al. (2021) argued that the red spectrum of Kamo‘oalewa was partially due to space weathering – an exposure time of a few million years was likely sufficient to explain its surface properties and was similar to its approximate dynamical lifetime and even the age of the crater that Jiao et al. (2024) suggested it came from, Giordano Bruno. If correct, perhaps 2024 PT5 has a somewhat younger surface than the larger Kamo‘oalewa. In any case, PT5 is smaller than Kamo‘oalewa and thus the craters that are energetic enough to produce an object its size are more common – a more recent ejection age, and thus a ‘younger’ surface might be preferred from that argument as well. (Granted, smaller fragments would be more common than larger ones in cratering events of any size as well.) Further work to study these two objects and to find more lunar-like NEOs will be needed to ascertain the origin of these differences and how they can be related to the circumstances of their creation. At any rate, the smaller size of PT5 means that we are approaching being able to study the impactors and outcomes from the kinds of small impacts seen regularly by the Lunar Reconaissance Orbiter.

For more information about 2024 PT5 and Kamo‘oalewa:
https://en.wikipedia.org/wiki/2024_PT5
https://en.wikipedia.org/wiki/469219_Kamo%CA%BBoalewa

Call to Protect the Dark and Quiet Sky from Harmful Interference by Satellite Constellations
https://arxiv.org/abs/2412.08244

The growing number of satellite constellations in low Earth orbit (LEO) enhances global communications and Earth observation, and support of space commerce is a high priority of many governments. At the same time, the proliferation of satellites in LEO has negative effects on astronomical observations and research, and the preservation of the dark and quiet sky. These satellite constellations reflect sunlight onto optical telescopes, and their radio emission impacts radio observatories, jeopardising our access to essential scientific discoveries through astronomy. The changing visual appearance of the sky also impacts our cultural heritage and environment. Both ground-based observatories and space-based telescopes in LEO are affected, and there are no places on Earth that can escape the effects of satellite constellations given their global nature. The minimally disturbed dark and radio-quiet sky1 is crucial for conducting fundamental research in astronomy and important public services such as planetary defence, technology development, and high-precision geolocation.

Some aspects of satellite deployment and operation are regulated by States and intergovernmental organisations. While regulatory agencies in some States have started to require operators to coordinate with their national astronomy agencies over impacts, mitigation of the impact of space objects on astronomical activities is not sufficiently regulated.

1We refer to the radio-quiet sky as simply the ‘quiet sky’

To address this issue, the CPS [International Astronomical Union (IAU) Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (CPS)] urges States and the international community to:

1) Safeguard access to the dark and quiet sky and prevent catastrophic
loss of high quality observations.

2) Increase financial support for astronomy to offset and compensate the impacts on observatory operations and implement mitigation measures at observatories and in software.

3) Encourage and support satellite operators and industry to collaborate with the astronomy community to develop, share and adopt best practices in interference mitigation, leading to widely adopted standards and guidelines.

4) Provide incentive measures for the space industry to develop the required technology to minimise negative impacts. Support the establishment of test labs for brightness and basic research into alternate less reflective materials
and reduction of unwanted radiation in the radio regime for spacecraft manufacturing.

5) In the longer term, establish regulations and conditions of authorization and supervision based on practical experience as well as the general provisions of international law and main principles of environmental law to codify industry best practices that mitigate the negative impacts on astronomical observations. Satellites in LEO should be designed and operated in ways that minimise adverse effects on astronomy and the dark and quiet sky.

6) Continue to support finding solutions to space sustainability issues, including the problem of increasing space debris leading to a brighter sky. Minimising the production of space debris will also benefit the field of astronomy and all sky observers worldwide.

The elephant in the room—not specifically mentioned in this report—is that countries and companies should be sharing satellite constellations as much as possible to minimize the number of satellite constellations in orbit. This is analogous to the co-location often required for terrestrial communication towers. Our current satellite constellation predicament illustrates yet another reason why we need a binding set of international laws that apply to all nations and are enforced by a global authority. The sooner we have this the better, as our cultural survival—if not our physical survival—may depend upon it.

A New Method to Derive an Empirical Lower Limit on the Mass Density of a UFO
https://arxiv.org/abs/2412.12142

I derive a lower limit on the mass of an Unidentified Flying Object (UFO) based on measurements of its speed and acceleration, as well as the infrared luminosity of the airglow around it. If the object’s radial velocity can be neglected, the mass limit is independent of distance. Measuring the distance and angular size of the object allows to infer its minimum mass density. The Galileo Project will be collecting the necessary data on millions of objects in the sky over the coming year.

Any object moving through air radiates excess heat in the form of infrared airglow luminosity, L. The airglow luminosity is a fraction of the total power dissipated by the object’s speed, v, times the frictional force of air acting on the object. The radiative efficiency depends on the specific shape of the object and the turbulence and thermodynamic conditions in the atmosphere around it. If the object accelerates, then this friction force must be smaller than the force provided by the engine which propels the object. The net force equals the object’s mass, M, times its acceleration, a.

In conclusion, one gets an unavoidable lower limit on the mass of an accelerating object. The object’s mass must be larger than the infrared luminosity from heated air around it, divided by the product of the object’s acceleration and speed.

This limit provides an elegant way to constrain the minimum mass of Unidentified Flying Objects (UFOs), also labeled as Unidentified Anomalous Phenomena (UAPs). To turn the inequality into an equality, one needs to know the detailed object shape and atmospheric conditions around the object.

The first Galileo Project Observatory at Harvard University collects data on ∼ 105 objects in the sky every month. A comprehensive description of its commissioning data on ∼ 5 × 105 objects was provided in a recent paper (Dominé et al. 2024). The data includes infrared images captured by an all-sky Dalek array of eight uncooled infrared cameras placed on half a sphere.

Within the coming month, the Galileo Project’s research team plans to employ multiple Daleks separated by a few miles, in order to measure distances to objects through the method of triangulation.

If the measured velocity and acceleration of a technological object are outside the flight characteristics and performance envelopes of drones or airplanes, then the object would be classified by the Galileo Project’s research team as an outlier. In such a case, it would be interesting to calculate the minimum mass density of the object. If the result exceeds normal solid densities, then the object would qualify as anomalous, a UAP. Infrared emission by the object would be a source of confusion, unless the object is resolved and the emission from it can be separated from the heated air around it.

All flying objects made by humans have a volume-averaged mass density ⟨ρ⟩ which is orders of magnitude below 22.6 g cm−3, the density of Osmium – which is the densest metal known on Earth. A UFO with a higher mass density than Osmium would have to carry exotic material, not found on Earth.

By summer 2025, there will be three Galileo Project observatories operating in three different states within the U.S. and collecting data on a few million objects per year. With new quantitative data on infrared luminosities, velocities and accelerations of technological objects, it would be possible to check whether there are any UFOs denser than Osmium.

I admire the author, Avi Loeb, Harvard astrophysics professor, for his creative approaches to interesting problems outside the mainstream that many of his colleagues tend to avoid. Lately, he’s been focusing a lot on technosignatures, and I imagine he has a keen interest in the recent spate of unexplained nighttime drone sightings in New Jersey and elsewhere. For more about Loeb and the Galileo Project:
https://en.wikipedia.org/wiki/Avi_Loeb
https://en.wikipedia.org/wiki/The_Galileo_Project

Beyond CCDs: Characterization of sCMOS detectors for optical astronomy
https://arxiv.org/abs/2409.16449

Modern scientific complementary metal-oxide semiconductor (sCMOS) detectors provide a highly competitive alternative to charge-coupled devices (CCDs), the latter of which have historically been dominant in optical imaging. sCMOS boast comparable performances to CCDs with faster frame rates, lower read noise, and a higher dynamic range. Furthermore, their lower production costs are shifting the industry to abandon CCD support and production in favour of CMOS, making their characterization urgent. In this work, we characterized a variety of high-end commercially available sCMOS detectors to gauge the state of this technology in the context of applications in optical astronomy. We evaluated a range of sCMOS detectors, including larger pixel models such as the Teledyne Prime 95B and the Andor Sona-11, which are similar to CCDs in pixel size and suitable for wide-field astronomy. Additionally, we assessed smaller pixel detectors like the Ximea xiJ and Andor Sona-6, which are better suited for deep-sky imaging. Furthermore, high-sensitivity quantitative sCMOS detectors such as the Hamamatsu Orca-Quest C15550-20UP, capable of resolving individual photoelectrons, were also tested. In-lab testing showed low levels of dark current, read noise, faulty pixels, and fixed pattern noise, as well as linearity levels above 98% across all detectors. The Orca-Quest had particularly low noise levels with a dark current of 0.0067±0.0003 e−/s (at −20∘C with air cooling) and a read noise of 0.37±0.09 e− using its standard readout mode. Our tests revealed that the latest generation of sCMOS detectors excels in optical imaging performance, offering a more accessible alternative to CCDs for future optical astronomy instruments.

The Hamamatsu Orca-Quest CP15550-20UP, simply called Orca-Quest, is advertised as being a quantitative CMOS detector with extremely low noise levels and photoelectron counting capabilities. It features a custom 9.4-megapixel sensor with 4.6 × 4.6 μm pixels. The Orca-Quest has two scan modes that were characterized: standard and ultra-quiet. The ultra-quiet mode has a much lower frame rate at 5 frames per second (fps) compared to the standard mode’s 120 fps, which allows for much lower read noise. Also characterized was the ‘photon number resolving’ readout mode which claims to report the integer number of incident photoelectrons based on a proprietary calibrated algorithm using the ultra-quiet scan. The Orca-Quest has a detector-imposed temperature lock at −20◦C when air-cooled. The standard and ultra-quiet modes are 16-bit, with a saturation limit of 65536 ADU while the photon number resolving mode has a saturation limit of only 200 ADU. The Orca-Quest boasts a peak quantum efficiency of 85%.

Unlike CCDs, which use a single global amplifier with a shift register, sCMOS pixels have individual readout electronics, requiring each pixel to be tested as an independent detector. Historically, this led to high fixed pattern noise in CMOS detectors, but we found negligible fixed pattern noise in almost all the detectors we analyzed pixel-wise.

Meteor Shower Calendar 2023

Here’s our meteor shower calendar for 2023.  It is sourced from the IMO’s Working List of Visual Meteor Showers (https://www.imo.net/files/meteor-shower/cal2023.pdf, Table 5, p. 25).

Each meteor shower is identified using its three-character IAU meteor shower code.  Codes are bold on the date of maximum, and one day either side of maximum.

Some additional events have been added to the calendar from Sources of Possible or Additional Activity, Table 6a, p. 27). I used the following abbreviations for the Table 6a events that do not have a standard three-character meteor code:

BA* = 2016 BA14
46P = 46P/Wirtanen

Here’s a printable PDF file of the meteor shower calendar shown below:

Meteor Calendar 2023Download

Happy meteor watching!

January 2023
SUN MON TUE WED THU FRI SAT
1
QUA COM		 2
QUA COM		 3
QUA COM		 4
QUA COM		 5
QUA COM		 6
QUA COM		 7
QUA COM
8
QUA COM		 9
QUA COM KCA		 10
QUA COM GUM KCA		 11
QUA COM GUM KCA		 12
QUA COM GUM		 13
COM GUM		 14
COM GUM
15
COM GUM		 16
COM GUM		 17
COM GUM		 18
COM GUM		 19
COM GUM		 20
COM GUM		 21
COM GUM
22
COM GUM		 23
COM		 24
COM		 25
COM		 26
COM		 27
COM		 28
COM
29
COM		 30
COM		 31
COM ACE		        
February 2023
SUN MON TUE WED THU FRI SAT
      1
COM ACE		 2
COM ACE		 3
COM ACE		 4
COM ACE
5
ACE		 6
ACE		 7
ACE		 8
ACE		 9
ACE		 10
ACE		 11
ACE
12
ACE		 13
ACE		 14
ACE		 15
ACE		 16
ACE		 17
ACE		 18
ACE
19
ACE		 20
ACE		 21 22 23 24 25
GNO
26
GNO		 27
GNO		 28
GNO		        
March 2023
SUN MON TUE WED THU FRI SAT
      1
GNO		 2
GNO		 3
GNO		 4
GNO
5
GNO		 6
GNO		 7
GNO		 8
GNO		 9
GNO		 10
GNO		 11
GNO
12
GNO		 13
GNO		 14
GNO		 15
GNO		 16
GNO		 17
GNO		 18
GNO
19
GNO		 20
BA* GNO		 21
BA* GNO		 22
BA* GNO		 23
GNO		 24
GNO		 25
GNO
26
GNO		 27
GNO		 28
GNO		 29 30 31  
April 2023
SUN MON TUE WED THU FRI SAT
            1
2 3 4 5 6 7 8
9 10 11 12 13 14
LYR		 15
PPU LYR
16
PPU LYR		 17
PPU LYR		 18
PPU LYR		 19
ETA PPU LYR		 20
ETA PPU LYR		 21
ETA PPU LYR		 22
ETA PPU LYR
23
ETA PPU LYR		 24
ETA PPU LYR		 25
ETA PPU LYR		 26
ETA PPU LYR		 27
ETA PPU LYR		 28
ETA PPU LYR		 29
ETA LYR
30
ETA LYR		            
May 2023
SUN MON TUE WED THU FRI SAT
  1
ETA		 2
ETA		 3
ELY ETA		 4
ELY ETA		 5
ELY ETA		 6
ELY ETA
7
ELY ETA		 8
ELY ETA		 9
ELY ETA		 10
ELY ETA		 11
ELY ETA		 12
ELY ETA		 13
ELY ETA
14
ARI ELY ETA		 15
ARI ETA		 16
ARI ETA		 17
ARI ETA		 18
ARI ETA		 19
ARI ETA		 20
ARI ETA
21
ARI ETA		 22
ARI ETA		 23
ARI ETA		 24
ARI ETA		 25
ARI ETA		 26
ARI ETA		 27
ARI ETA
28
ARI CAM ETA		 29
ARI CAM		 30
ARI CAM		 31
ARI		      
June 2023
SUN MON TUE WED THU FRI SAT
        1
ARI		 2
ARI		 3
ARI
4
ARI		 5
ARI		 6
ARI		 7
ARI		 8
ARI		 9
ARI		 10
ARI
11
ARI		 12
ARI		 13
ARI		 14
ARI		 15
ARI		 16
ARI		 17
ARI
18
ARI		 19
ARI		 20
ARI		 21
ARI		 22
JBO ARI		 23
JBO ARI		 24
JBO ARI
25
JBO		 26
JBO		 27
JBO		 28
JBO		 29
JBO		 30
JBO		  
July 2023
SUN MON TUE WED THU FRI SAT
            1
JBO
2
JBO		 3
CAP		 4
CAP JPE		 5
CAP JPE		 6
CAP JPE		 7
CAP JPE		 8
CAP JPE
9
CAP JPE		 10
CAP JPE		 11
CAP JPE		 12
CAP SDA JPE		 13
CAP SDA JPE		 14
CAP SDA JPE		 15
CAP SDA PAU
16
CAP SDA PAU		 17
PER CAP SDA PAU		 18
PER CAP SDA PAU		 19
PER CAP SDA PAU		 20
PER CAP SDA PAU		 21
PER CAP SDA PAU		 22
PER CAP SDA PAU
23
PER CAP SDA PAU		 24
PER CAP SDA PAU		 25
PER CAP SDA GDR PAU		 26
PER CAP SDA GDR PAU		 27
PER CAP SDA GDR PAU		 28
PER CAP SDA GDR PAU		 29
PER CAP SDA GDR
30
PER CAP SDA GDR PAU		 31
PER ERI CAP SDA GDR PAU		          
August 2023
SUN MON TUE WED THU FRI SAT
    1
PER ERI CAP SDA PAU		 2
PER ERI CAP SDA PAU		 3
KCG PER ERI CAP SDA PAU		 4
KCG PER ERI CAP SDA PAU		 5
KCG PER ERI CAP SDA PAU
6
KCG PER ERI CAP SDA PAU		 7
KCG PER ERI CAP SDA PAU		 8
KCG PER ERI CAP SDA PAU		 9
KCG PER ERI CAP SDA PAU		 10
KCG PER ERI CAP SDA PAU		 11
KCG PER ERI CAP SDA		 12
KCG PER ERI CAP SDA
13
KCG PER ERI CAP SDA		 14
KCG PER ERI CAP SDA		 15
KCG PER ERI CAP SDA		 16
KCG PER ERI SDA		 17
KCG PER ERI SDA		 18
KCG PER ERI SDA		 19
KCG PER ERI SDA
20
KCG PER SDA		 21
KCG PER SDA		 22
KCG PER SDA		 23
KCG PER SDA		 24
KCG PER		 25
KCG		 26
KCG
27
KCG		 28
AUR KCG		 29
AUR		 30
AUR		 31
AUR		    
September 2023
SUN MON TUE WED THU FRI SAT
          1
AUR		 2
AUR
3
AUR		 4
AUR		 5
SPE AUR		 6
SPE		 7
SPE		 8
SPE		 9
DSX SPE
10
DSX SPE		 11
DSX SPE		 12
DSX SPE		 13
DSX SPE		 14
DSX SPE		 15
DSX SPE		 16
DSX SPE
17
DSX SPE		 18
DSX SPE		 19
DSX SPE		 20
STA DSX SPE		 21
STA DSX SPE		 22
STA DSX		 23
STA DSX
24
STA DSX		 25
STA DSX		 26
STA DSX		 27
STA DSX		 28
STA DSX		 29
STA DSX		 30
STA DSX
October 2023
SUN MON TUE WED THU FRI SAT
1
STA DSX		 2
STA ORI DSX		 3
STA ORI DSX		 4
STA ORI DSX		 5
STA ORI OCT DSX		 6
STA ORI DRA OCT DSX		 7
STA ORI DRA OCT DSX
8
STA ORI DRA DSX		 9
STA ORI DRA DSX		 10
STA ORI DAU DRA		 11
STA ORI DAU		 12
STA ORI DAU		 13
STA ORI DAU		 14
STA ORI EGE DAU
15
STA ORI EGE DAU		 16
STA ORI EGE DAU		 17
STA ORI EGE DAU		 18
STA ORI EGE DAU		 19
STA LMI ORI EGE		 20
NTA STA LMI ORI EGE		 21
NTA STA LMI ORI EGE
22
NTA STA LMI ORI EGE		 23
NTA STA LMI ORI EGE		 24
NTA STA LMI ORI EGE		 25
NTA STA LMI ORI EGE		 26
NTA STA LMI ORI EGE		 27
NTA STA LMI ORI EGE		 28
NTA STA ORI
29
NTA STA ORI		 30
NTA STA ORI		 31
NTA STA ORI		        
November 2023
SUN MON TUE WED THU FRI SAT
      1
NTA STA ORI		 2
NTA STA ORI		 3
NTA STA ORI		 4
NTA STA ORI
5
NTA STA ORI		 6
LEO NTA STA ORI		 7
LEO NTA STA ORI		 8
LEO NTA STA		 9
LEO NTA STA		 10
LEO NTA STA		 11
LEO NTA STA
12
LEO NTA STA		 13
NOO LEO NTA STA		 14
NOO LEO NTA STA		 15
NOO AMO LEO NTA STA		 16
NOO AMO LEO NTA STA		 17
NOO AMO LEO NTA STA		 18
NOO AMO LEO NTA STA
19
NOO AMO LEO NTA STA		 20
NOO AMO LEO NTA STA		 21
NOO AMO LEO NTA		 22
NOO AMO LEO NTA		 23
NOO AMO LEO NTA		 24
NOO AMO LEO NTA		 25
NOO AMO LEO NTA
26
NOO LEO NTA		 27
NOO LEO NTA		 28
PHO NOO LEO NTA		 29
PHO NOO LEO NTA		 30
PHO NOO LEO NTA		    
December 2023
SUN MON TUE WED THU FRI SAT
          1
PUP AND PHO NOO NTA		 2
PUP AND PHO NOO NTA
3
HYD PUP AND PHO NOO NTA		 4
GEM HYD PUP PHO NOO NTA		 5
COM GEM HYD MON PUP PHO NOO NTA		 6
COM GEM HYD MON PUP PHO NOO NTA		 7
COM GEM HYD MON PUP PHO NTA		 8
COM GEM HYD MON PUP PHO NTA		 9
COM GEM HYD MON PUP PHO NTA
10
COM GEM HYD MON PUP NTA		 11
COM GEM 46P HYD MON PUP		 12
COM GEM 46P HYD MON PUP		 13
COM GEM 46P HYD MON PUP		 14
COM GEM HYD MON PUP		 15
COM GEM HYD MON PUP		 16
COM GEM HYD MON
17
COM URS GEM HYD MON		 18
COM URS GEM HYD MON		 19
COM URS GEM HYD MON		 20
COM URS GEM HYD MON		 21
COM URS		 22
COM URS		 23
COM URS
24
COM URS		 25
COM URS		 26
COM URS		 27
COM		 28
QUA COM		 29
QUA COM		 30
QUA COM
31
QUA COM		            

A Case for Ten Planets

Clyde Tombaugh (1906-1997) spent the first fifteen years of his life on a farm near Streator, Illinois, and then his family moved to a farm near Burdett, Kansas (no wonder he got interested in astronomy!), and he went to high school there. Then, on February 18, 1930, Tombaugh, a self-taught amateur astronomer and telescope maker, discovered the ninth planet in our solar system, Pluto. It had been nearly 84 years since the eighth planet, Neptune, had been discovered, in 1846. And it would be another 62 years before another trans-Neptunian object (TNO) would be discovered.

Clyde Tombaugh made his discovery using a 13-inch f/5.3 photographic refractor at the Lowell Observatory in Flagstaff, Arizona.

Clyde Tombaugh was 24 years old when he discovered Pluto. He died in 1997 at the age of 90 (almost 91). I was very fortunate to meet Prof. Tombaugh at a lecture he gave at Iowa State University in 1990. At that lecture, he told a fascinating story about the discovery of Pluto, and I remember well his comment that he felt certain that no “tenth planet” larger than Pluto exists in our solar system, because of the thorough searches he and others had done since his discovery of Pluto. But, those searches were done before the CCD revolution, and just two years later, the first TNO outside the Pluto-Charon system, 15760 Albion (1992 QB1), would be discovered by David Jewitt (1958-) and Jane Luu (1963-), although only 1/9th the size of Pluto.

Pluto is, by far, the smallest of the nine planets. At only 2,377 km across, Pluto is only 2/3 the size of our Moon! Pluto has a large moon called Charon (pronounced SHAR-on) that is 1,212 km across (over half the size of Pluto), discovered in 1978 by James Christy (1938-). Two additional moons were discovered using the Hubble Space Telescope (HST) in 2005: Hydra (50.9 × 36.1 × 30.9 km) and Nix (49.8 × 33.2 × 31.1 km). A fourth moon was discovered using HST in 2011: Kerberos (10 × 9 × 9 km). And a fifth moon, again using HST, in 2012: Styx (16 × 9 × 8 km).

Pluto has been visited by a single spacecraft. New Horizons passed 12,472 km from Pluto and 28,858 km from Charon on July 14, 2015. Then, about 3½ years later, New Horizons passed 3,538 km from 486958 Arrokoth, on January 1, 2019.

Only one other TNO comparable in size to Pluto (or larger) is known to exist. 136199 Eris and its moon Dysnomia were discovered in 2005 by Mike Brown (1965-), Chad Trujillo (1973-), and David Rabinowitz (1960-). It is currently estimated that Eris is 97.9% the size of Pluto. Not surprisingly, in 2006 Pluto was “demoted” by the IAU from planethood to dwarf planet status. (Is not a “dwarf planet” a planet? Confusing…)

My take on this is that Pluto should be considered a planet along with Eris, of course. The definition of “planet” is really rather arbitrary, so given that Pluto was discovered 75 years before Eris, and 62 years before TNO #2, I think we should (in deference to the memory of Mr. Tombaugh, mostly) define a planet as any non-satellite object orbiting the Sun that is around the size of Pluto or larger. So, by my definition, there are currently ten known planets in our solar system. Is that really too many to keep track of?

There is precedent for including history in scientific naming decisions. William Herschel (1738-1822) is thought to have coined the term “planetary nebula” in the 1780s, and though we now know they have nothing to do with planets (unless their morphology is affected by orbiting planets), we still use the term “planetary nebula” to describe them today.

In the table below, you will find the eight “classical” planets, plus the five largest TNOs, all listed in order of descending size. (The largest asteroid, Ceres, is 939 km across, and is thus smaller than the smallest of these TNOs.)

You’ll see that the next largest TNO after Eris is Haumea, and that its diameter is only 67% that of Eris.

I’ve also listed the largest satellite for each of these objects. Venus and Mercury do not have a satellite—at least not at the present time.

It is amazing to note that both Ganymede and Titan are larger than the planet Mercury! And Ganymede, Titan, the Moon, and Triton are all larger than Pluto.

Largest Objects in the Solar System

Object Diameter (km) Largest Satellite Diameter (km) Size Ratio
Jupiter 139,822 Ganymede 5,268 3.8%
Saturn 116,464 Titan 5,149 4.4%
Uranus 50,724 Titania 1,577 3.1%
Neptune 49,244 Triton 2,707 5.5%
Earth 12,742 Moon 3,475 27.3%
Venus 12,104 N/A N/A N/A
Mars 6,779 Phobos 23 0.3%
Mercury 4,879 N/A N/A N/A
Pluto 2,377 Charon 1,212 51.0%
Eris 2,326 Dysnomia 700 30.1%
Haumea 1,560 Hiʻiaka 320 20.5%
Makemake 1,430 S/2015 (136472) 175 12.2%
Gonggong 1,230 Xiangliu 200 16.3%

Should any other non-satellite objects with a diameter of at least 2,000 km be discovered in our solar system, I think we should call them planets, too.

Meteor Shower Calendar 2022

Here’s our meteor shower calendar for 2022.  It is sourced from the IMO’s Working List of Visual Meteor Showers (https://www.imo.net/files/meteor-shower/cal2022.pdf, Table 5, p. 25).

Each meteor shower is identified using its three-character IAU meteor shower code.  Codes are bold on the date of maximum, and one day either side of maximum.

Some additional events have been added to the calendar from Sources of Possible or Additional Activity, Table 6a, p. 27). I used the following abbreviations for the Table 6a events that do not have a standard three-character meteor code:

GY2 = 2006 GY2
209 = 209P/LINEAR
CK1 = C/1852 K1

Here’s a printable PDF file of the meteor shower calendar shown below:

Meteor Calendar 2022Download

Happy meteor watching!

January 2022
SUN MON TUE WED THU FRI SAT
            1
DLM QUA
2
DLM QUA		 3
DLM QUA		 4
DLM QUA		 5
DLM QUA		 6
DLM QUA		 7
DLM QUA		 8
DLM QUA
9
DLM QUA KCA		 10
DLM QUA GUM KCA		 11
DLM QUA GUM KCA		 12
DLM QUA GUM		 13
DLM GUM		 14
DLM GUM		 15
DLM GUM
16
DLM GUM		 17
DLM GUM		 18
DLM GUM		 19
DLM GUM		 20
DLM GUM		 21
DLM GUM		 22
DLM GUM
23
DLM		 24
DLM		 25
DLM		 26
DLM		 27
DLM		 28
DLM		 29
DLM
30
DLM		 31
DLM ACE		          
February 2022
SUN MON TUE WED THU FRI SAT
    1
DLM ACE		 2
DLM ACE		 3
DLM ACE		 4
DLM ACE		 5
ACE
6
ACE		 7
ACE		 8
ACE		 9
ACE		 10
ACE		 11
ACE		 12
ACE
13
ACE		 14
ACE		 15
ACE		 16
ACE		 17
ACE		 18
ACE		 19
ACE
20
ACE		 21 22 23 24 25
GNO		 26
GNO
27
GNO		 28
GNO		          
March 2022
SUN MON TUE WED THU FRI SAT
    1
GNO		 2
GNO		 3
GNO		 4
GNO		 5
GNO
6
GNO		 7
GNO		 8
GNO		 9
GNO		 10
GNO		 11
GNO		 12
GNO
13
GNO		 14
GNO		 15
GNO		 16
GNO		 17
GNO		 18
GNO		 19
GNO
20
GNO		 21
GNO		 22
GNO		 23
GNO		 24
GNO		 25
GNO		 26
GNO
27
GNO		 28
GNO		 29 30 31    
April 2022
SUN MON TUE WED THU FRI SAT
          1 2
3 4 5 6 7 8 9
10 11 12 13 14
LYR		 15
PPU LYR		 16
PPU LYR
17
PPU LYR		 18
PPU LYR		 19
ETA PPU LYR		 20
ETA PPU LYR		 21
ETA PPU LYR		 22
ETA PPU LYR		 23
ETA PPU LYR
24
ETA PPU LYR		 25
ETA PPU LYR		 26
ETA PPU LYR		 27
ETA PPU LYR		 28
ETA PPU LYR		 29
ETA LYR		 30
ETA LYR
May 2022
SUN MON TUE WED THU FRI SAT
1
ETA		 2
ETA		 3
ELY ETA		 4
ELY ETA		 5
ELY ETA		 6
ELY ETA		 7
ELY ETA
8
ELY ETA		 9
ELY ETA		 10
ELY ETA		 11
ELY ETA		 12
ELY ETA		 13
ELY ETA		 14
GY2 ARI ELY ETA
15
GY2 ARI ETA		 16
GY2 ARI ETA		 17
ARI ETA		 18
ARI ETA		 19
ARI ETA		 20
ARI ETA		 21
ARI ETA
22
ARI ETA		 23
ARI ETA		 24
209 ARI ETA		 25
209 ARI ETA		 26
209 ARI ETA		 27
ARI ETA		 28
ARI ETA
29
ARI		 30
TAH ARI		 31
TAH ARI		        
June 2022
SUN MON TUE WED THU FRI SAT
      1
TAH ARI		 2
ARI		 3
ARI		 4
ARI
5
ARI		 6
ARI		 7
ARI		 8
ARI		 9
ARI		 10
ARI		 11
ARI
12
ARI		 13
ARI		 14
ARI		 15
ARI		 16
ARI		 17
ARI		 18
ARI
19
ARI		 20
ARI		 21
ARI		 22
JBO ARI		 23
JBO ARI		 24
JBO ARI		 25
JBO
26
JBO		 27
JBO		 28
JBO		 29
JBO		 30
JBO		    
July 2022
SUN MON TUE WED THU FRI SAT
          1
JBO		 2
JBO
3
CAP		 4
CAP JPE		 5
CAP JPE		 6
CAP JPE		 7
CAP JPE		 8
CAP JPE		 9
CAP JPE
10
CAP JPE		 11
CAP JPE		 12
CAP SDA JPE		 13
CAP SDA JPE		 14
CAP SDA JPE		 15
CAP SDA PAU		 16
CAP SDA PAU
17
PER CAP SDA PAU		 18
PER CAP SDA PAU		 19
PER CAP SDA PAU		 20
PER CAP SDA PAU		 21
PER CAP SDA PAU		 22
PER CAP SDA PAU		 23
PER CAP SDA PAU
24
PER CAP SDA PAU		 25
PER CAP SDA GDR PAU		 26
PER CAP SDA GDR PAU		 27
PER CAP SDA GDR PAU		 28
PER CAP SDA GDR PAU		 29
PER CAP SDA GDR		 30
PER CAP SDA GDR PAU
31
PER CAP SDA GDR PAU		            
August 2022
SUN MON TUE WED THU FRI SAT
  1
PER CAP SDA PAU		 2
PER CAP SDA PAU		 3
KCG PER CAP SDA PAU		 4
KCG PER CAP SDA PAU		 5
KCG PER CAP SDA PAU		 6
KCG PER CAP SDA PAU
7
KCG PER CAP SDA PAU		 8
KCG PER CAP SDA PAU		 9
KCG PER CAP SDA PAU		 10
KCG PER CAP SDA PAU		 11
KCG PER CK1 CAP SDA		 12
KCG PER CK1 CAP SDA		 13
KCG PER CK1 CAP SDA
14
KCG PER CAP SDA		 15
KCG PER CAP SDA		 16
KCG PER SDA		 17
KCG PER SDA		 18
KCG PER SDA		 19
KCG PER SDA		 20
KCG PER SDA
21
KCG PER SDA		 22
KCG PER SDA		 23
KCG PER SDA		 24
KCG PER		 25
KCG		 26 27
28
AUR		 29
AUR		 30
AUR		 31
AUR		      
September 2022
SUN MON TUE WED THU FRI SAT
        1
AUR		 2
AUR		 3
AUR
4
AUR		 5
SPE AUR		 6
SPE		 7
SPE		 8
SPE		 9
DSX SPE		 10
STA DSX SPE
11
STA DSX SPE		 12
STA DSX SPE		 13
STA DSX SPE		 14
STA DSX SPE		 15
STA DSX SPE		 16
STA DSX SPE		 17
STA DSX SPE
18
STA DSX SPE		 19
STA DSX SPE		 20
STA DSX SPE		 21
STA DSX SPE		 22
STA DSX		 23
STA DSX		 24
STA DSX
25
STA DSX		 26
STA DSX		 27
STA DSX		 28
STA DSX		 29
STA DSX		 30
STA DSX		  
October 2022
SUN MON TUE WED THU FRI SAT
            1
STA DSX
2
ORI STA DSX		 3
ORI STA DSX		 4
ORI STA DSX		 5
ORI STA OCT DSX		 6
ORI STA DRA OCT DSX		 7
ORI STA DRA OCT DSX		 8
ORI STA DRA DSX
9
ORI STA DRA DSX		 10
ORI DAU STA DRA		 11
ORI DAU STA		 12
ORI DAU STA		 13
ORI DAU STA		 14
ORI EGE DAU STA		 15
ORI EGE DAU STA
16
ORI EGE DAU STA		 17
ORI EGE DAU STA		 18
ORI EGE DAU STA		 19
LMI ORI EGE STA		 20
NTA LMI ORI EGE STA		 21
NTA LMI ORI EGE STA		 22
NTA LMI ORI EGE STA
23
NTA LMI ORI EGE STA		 24
NTA LMI ORI EGE STA		 25
NTA LMI ORI EGE STA		 26
NTA LMI ORI EGE STA		 27
NTA LMI ORI EGE STA		 28
NTA ORI STA		 29
NTA ORI STA
30
NTA ORI STA		 31
NTA ORI STA		          
November 2022
SUN MON TUE WED THU FRI SAT
    1
NTA ORI STA		 2
NTA ORI STA		 3
NTA ORI STA		 4
NTA ORI STA		 5
NTA ORI STA
6
LEO NTA ORI STA		 7
LEO NTA ORI STA		 8
LEO NTA STA		 9
LEO NTA STA		 10
LEO NTA STA		 11
LEO NTA STA		 12
LEO NTA STA
13
NOO LEO NTA STA		 14
NOO LEO NTA STA		 15
NOO AMO LEO NTA STA		 16
NOO AMO LEO NTA STA		 17
NOO AMO LEO NTA STA		 18
NOO AMO LEO NTA STA		 19
NOO AMO LEO NTA STA
20
NOO AMO LEO NTA STA		 21
NOO AMO LEO NTA		 22
NOO AMO LEO NTA		 23
NOO AMO LEO NTA		 24
NOO AMO LEO NTA		 25
NOO AMO LEO NTA		 26
NOO LEO NTA
27
NOO LEO NTA		 28
PHO NOO LEO NTA		 29
PHO NOO LEO NTA		 30
PHO NOO LEO NTA		      
December 2022
SUN MON TUE WED THU FRI SAT
        1
PUP PHO NOO NTA		 2
PUP PHO NOO NTA		 3
HYD PUP PHO NOO NTA
4
GEM HYD PUP PHO NOO NTA		 5
DLM GEM HYD MON PUP PHO NOO NTA		 6
DLM GEM HYD MON PUP PHO NOO NTA		 7
DLM GEM HYD MON PUP PHO NTA		 8
DLM GEM HYD MON PUP PHO NTA		 9
DLM GEM HYD MON PUP PHO NTA		 10
DLM GEM HYD MON PUP NTA
11
DLM GEM HYD MON PUP		 12
DLM COM GEM HYD MON PUP		 13
DLM COM GEM HYD MON PUP		 14
DLM COM GEM HYD MON PUP		 15
DLM COM GEM HYD MON PUP		 16
DLM COM GEM HYD MON		 17
DLM URS COM GEM HYD MON
18
DLM URS COM GEM HYD MON		 19
DLM URS COM GEM HYD MON		 20
DLM URS COM GEM HYD MON		 21
DLM URS COM		 22
DLM URS COM		 23
DLM URS COM		 24
DLM URS
25
DLM URS		 26
DLM URS		 27
DLM		 28
DLM QUA		 29
DLM QUA		 30
DLM QUA		 31
DLM QUA

Meteor Shower Calendar 2021

Here’s our meteor shower calendar for 2021.  It is sourced from the IMO’s Working List of Visual Meteor Showers (https://www.imo.net/files/meteor-shower/cal2021.pdf, Table 5, p. 25).

Each meteor shower is identified using its three-character IAU meteor shower code.  Codes are bold on the date of maximum, and one day either side of maximum.

Here’s a printable PDF file of the meteor shower calendar shown below:

Meteor Calendar 2021Download

Happy meteor watching!

January 2021
SUN MON TUE WED THU FRI SAT
          1
DLM QUA		 2
DLM QUA
3
DLM QUA		 4
DLM QUA		 5
DLM QUA		 6
DLM QUA		 7
DLM QUA		 8
DLM QUA		 9
DLM QUA
10
DLM QUA GUM		 11
DLM QUA GUM		 12
DLM QUA GUM		 13
DLM GUM		 14
DLM GUM		 15
DLM GUM		 16
DLM GUM
17
DLM GUM		 18
DLM GUM		 19
DLM GUM		 20
DLM GUM		 21
DLM GUM		 22
DLM GUM		 23
DLM
24
DLM		 25
DLM		 26
DLM		 27
DLM		 28
DLM		 29
DLM		 30
DLM
31
DLM ACE		            
February 2021
SUN MON TUE WED THU FRI SAT
  1
DLM ACE		 2
DLM ACE		 3
DLM ACE		 4
DLM ACE		 5
ACE		 6
ACE
7
ACE		 8
ACE		 9
ACE		 10
ACE		 11
ACE		 12
ACE		 13
ACE
14
ACE		 15
ACE		 16
ACE		 17
ACE		 18
ACE		 19
ACE		 20
ACE
21 22 23 24 25
GNO		 26
GNO		 27
GNO
28
GNO		            
March 2021
SUN MON TUE WED THU FRI SAT
  1
GNO		 2
GNO		 3
GNO		 4
GNO		 5
GNO		 6
GNO
7
GNO		 8
GNO		 9
GNO		 10
GNO		 11
GNO		 12
GNO		 13
GNO
14
GNO		 15
GNO		 16
GNO		 17
GNO		 18
GNO		 19
GNO		 20
GNO
21
GNO		 22
GNO		 23
GNO		 24
GNO		 25
GNO		 26
GNO		 27
GNO
28
GNO		 29 30 31      
April 2021
SUN MON TUE WED THU FRI SAT
        1 2 3
4 5 6 7 8 9 10
11 12 13 14
LYR		 15
PPU LYR		 16
PPU LYR		 17
PPU LYR
18
PPU LYR		 19
ETA PPU LYR		 20
ETA PPU LYR		 21
ETA PPU LYR		 22
ETA PPU LYR		 23
ETA PPU LYR		 24
ETA PPU LYR
25
ETA PPU LYR		 26
ETA PPU LYR		 27
ETA PPU LYR		 28
ETA PPU LYR		 29
ETA LYR		 30
ETA LYR		  
May 2021
SUN MON TUE WED THU FRI SAT
            1
ETA
2
ETA		 3
ELY ETA		 4
ELY ETA		 5
ELY ETA		 6
ELY ETA		 7
ELY ETA		 8
ELY ETA
9
ELY ETA		 10
ELY ETA		 11
ELY ETA		 12
ELY ETA		 13
ELY ETA		 14
ARI ELY ETA		 15
ARI ETA
16
ARI ETA		 17
ARI ETA		 18
ARI ETA		 19
ARI ETA		 20
ARI ETA		 21
ARI ETA		 22
ARI ETA
23
ARI ETA		 24
ARI ETA		 25
ARI ETA		 26
ARI ETA		 27
ARI ETA		 28
ARI ETA		 29
ARI
30
ARI		 31
ARI		          
June 2021
SUN MON TUE WED THU FRI SAT
    1
ARI		 2
ARI		 3
ARI		 4
ARI		 5
ARI
6
ARI		 7
ARI		 8
ARI		 9
ARI		 10
ARI		 11
ARI		 12
ARI
13
ARI		 14
ARI		 15
ARI		 16
ARI		 17
ARI		 18
ARI		 19
ARI
20
ARI		 21
ARI		 22
JBO ARI		 23
JBO ARI		 24
JBO ARI		 25
JBO		 26
JBO
27
JBO		 28
JBO		 29
JBO		 30
JBO		      
July 2021
SUN MON TUE WED THU FRI SAT
        1
JBO		 2
JBO		 3
CAP
4
CAP		 5
CAP		 6
CAP		 7
CAP		 8
CAP		 9
CAP		 10
CAP
11
CAP		 12
CAP SDA		 13
CAP SDA		 14
CAP SDA		 15
CAP SDA PAU		 16
CAP SDA PAU		 17
PER CAP SDA PAU
18
PER CAP SDA PAU		 19
PER CAP SDA PAU		 20
PER CAP SDA PAU		 21
PER CAP SDA PAU		 22
PER CAP SDA PAU		 23
PER CAP SDA PAU		 24
PER CAP SDA PAU
25
PER CAP SDA PAU		 26
PER CAP SDA PAU		 27
PER CAP SDA PAU		 28
PER CAP SDA PAU		 29
PER CAP SDA PAU		 30
PER CAP SDA PAU		 31
PER CAP SDA PAU
August 2021
SUN MON TUE WED THU FRI SAT
1
PER CAP SDA PAU		 2
PER CAP SDA PAU		 3
KCG PER CAP SDA PAU		 4
KCG PER CAP SDA PAU		 5
KCG PER CAP SDA PAU		 6
KCG PER CAP SDA PAU		 7
KCG PER CAP SDA PAU
8
KCG PER CAP SDA PAU		 9
KCG PER CAP SDA PAU		 10
KCG PER CAP SDA PAU		 11
KCG PER CAP SDA		 12
KCG PER CAP SDA		 13
KCG PER CAP SDA		 14
KCG PER CAP SDA
15
KCG PER CAP SDA		 16
KCG PER SDA		 17
KCG PER SDA		 18
KCG PER SDA		 19
KCG PER SDA		 20
KCG PER SDA		 21
KCG PER SDA
22
KCG PER SDA		 23
KCG PER SDA		 24
KCG PER		 25
KCG		 26 27 28
AUR
29
AUR		 30
AUR		 31
AUR		        
September 2021
SUN MON TUE WED THU FRI SAT
      1
AUR		 2
AUR		 3
AUR		 4
AUR
5
SPE AUR		 6
SPE		 7
SPE		 8
SPE		 9
DSX SPE		 10
STA DSX SPE		 11
STA DSX SPE
12
STA DSX SPE		 13
STA DSX SPE		 14
STA DSX SPE		 15
STA DSX SPE		 16
STA DSX SPE		 17
STA DSX SPE		 18
STA DSX SPE
19
STA DSX SPE		 20
STA DSX SPE		 21
STA DSX SPE		 22
STA DSX		 23
STA DSX		 24
STA DSX		 25
STA DSX
26
STA DSX		 27
STA DSX		 28
STA DSX		 29
STA DSX		 30
STA DSX		    
October 2021
SUN MON TUE WED THU FRI SAT
          1
STA DSX		 2
ORI STA DSX
3
ORI STA DSX		 4
ORI STA OCT DSX		 5
ORI STA OCT DSX		 6
ORI STA DRA OCT DSX		 7
ORI STA DRA DSX		 8
ORI STA DRA DSX		 9
ORI STA DRA DSX
10
ORI DAU STA DRA		 11
ORI DAU STA		 12
ORI DAU STA		 13
ORI DAU STA		 14
ORI EGE DAU STA		 15
ORI EGE DAU STA		 16
ORI EGE DAU STA
17
ORI EGE DAU STA		 18
ORI EGE DAU STA		 19
LMI ORI EGE STA		 20
NTA LMI ORI EGE STA		 21
NTA LMI ORI EGE STA		 22
NTA LMI ORI EGE STA		 23
NTA LMI ORI EGE STA
24
NTA LMI ORI EGE STA		 25
NTA LMI ORI EGE STA		 26
NTA LMI ORI EGE STA		 27
NTA LMI ORI EGE STA		 28
NTA ORI STA		 29
NTA ORI STA		 30
NTA ORI STA
31
NTA ORI STA		            
November 2021
SUN MON TUE WED THU FRI SAT
  1
NTA ORI STA		 2
NTA ORI STA		 3
NTA ORI STA		 4
NTA ORI STA		 5
NTA ORI STA		 6
LEO NTA ORI STA
7
LEO NTA ORI STA		 8
LEO NTA STA		 9
LEO NTA STA		 10
LEO NTA STA		 11
LEO NTA STA		 12
LEO NTA STA		 13
NOO LEO NTA STA
14
NOO LEO NTA STA		 15
NOO AMO LEO NTA STA		 16
NOO AMO LEO NTA STA		 17
NOO AMO LEO NTA STA		 18
NOO AMO LEO NTA STA		 19
NOO AMO LEO NTA STA		 20
NOO AMO LEO NTA STA
21
NOO AMO LEO NTA		 22
NOO AMO LEO NTA		 23
NOO AMO LEO NTA		 24
NOO AMO LEO NTA		 25
NOO AMO LEO NTA		 26
NOO LEO NTA		 27
NOO LEO NTA
28
PHO NOO LEO NTA		 29
PHO NOO LEO NTA		 30
PHO NOO LEO NTA		        
December 2021
SUN MON TUE WED THU FRI SAT
      1
PUP PHO NOO NTA		 2
PUP PHO NOO NTA		 3
HYD PUP PHO NOO NTA		 4
GEM HYD PUP PHO NOO NTA
5
DLM GEM HYD MON PUP PHO NOO NTA		 6
DLM GEM HYD MON PUP PHO NOO NTA		 7
DLM GEM HYD MON PUP PHO NTA		 8
DLM GEM HYD MON PUP PHO NTA		 9
DLM GEM HYD MON PUP PHO NTA		 10
DLM GEM HYD MON PUP NTA		 11
DLM GEM HYD MON PUP
12
DLM COM GEM HYD MON PUP		 13
DLM COM GEM HYD MON PUP		 14
DLM COM GEM HYD MON PUP		 15
DLM COM GEM HYD MON PUP		 16
DLM COM GEM HYD MON		 17
DLM URS COM GEM HYD MON		 18
DLM URS COM GEM HYD MON
19
DLM URS COM GEM HYD MON		 20
DLM URS COM GEM HYD MON		 21
DLM URS COM		 22
DLM URS COM		 23
DLM URS COM		 24
DLM URS		 25
DLM URS
26
DLM URS		 27
DLM		 28
DLM QUA		 29
DLM QUA		 30
DLM QUA		 31
DLM QUA		  

Meteor Shower Calendar 2020

Here’s our meteor shower calendar for 2020.  It is sourced from the IMO’s Working List of Visual Meteor Showers (https://www.imo.net/files/meteor-shower/cal2020.pdf, Table 5, p. 25).

Each meteor shower is identified using its three-character IAU meteor shower code.  Codes are bold on the date of maximum, and one day either side of maximum.

Here’s a printable PDF file of the meteor shower calendar shown below:

Meteor Calendar 2020Download

Happy meteor watching!

January 2020
SUN MON TUE WED THU FRI SAT
      1
DLM QUA		 2
DLM QUA		 3
DLM QUA		 4
DLM QUA
5
DLM QUA		 6
DLM QUA		 7
DLM QUA		 8
DLM QUA		 9
DLM QUA		 10
DLM QUA GUM		 11
DLM QUA GUM
12
DLM QUA GUM		 13
DLM GUM		 14
DLM GUM		 15
DLM GUM		 16
DLM GUM		 17
DLM GUM		 18
DLM GUM
19
DLM GUM		 20
DLM GUM		 21
DLM GUM		 22
DLM GUM		 23
DLM		 24
DLM		 25
DLM
26
DLM		 27
DLM		 28
DLM		 29
DLM		 30
DLM		 31
DLM ACE		  
February 2020
SUN MON TUE WED THU FRI SAT
            1
DLM ACE
2
DLM ACE		 3
DLM ACE		 4
DLM ACE		 5
ACE		 6
ACE		 7
ACE		 8
ACE
9
ACE		 10
ACE		 11
ACE		 12
ACE		 13
ACE		 14
ACE		 15
ACE
16
ACE		 17
ACE		 18
ACE		 19
ACE		 20
ACE		 21 22
23 24 25
GNO		 26
GNO		 27
GNO		 28
GNO		  
March 2020
SUN MON TUE WED THU FRI SAT
1
GNO		 2
GNO		 3
GNO		 4
GNO		 5
GNO		 6
GNO		 7
GNO
8
GNO		 9
GNO		 10
GNO		 11
GNO		 12
GNO		 13
GNO		 14
GNO
15
GNO		 16
GNO		 17
GNO		 18
GNO		 19
GNO		 20
GNO		 21
GNO
22
GNO		 23
GNO		 24
GNO		 25
GNO		 26
GNO		 27
GNO		 28
GNO
29 30 31        
April 2020
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7 8 9 10 11
12 13 14
LYR		 15
PPU LYR		 16
PPU LYR		 17
PPU LYR		 18
PPU LYR
19
ETA PPU LYR		 20
ETA PPU LYR		 21
ETA PPU LYR		 22
ETA PPU LYR		 23
ETA PPU LYR		 24
ETA PPU LYR		 25
ETA PPU LYR
26
ETA PPU LYR		 27
ETA PPU LYR		 28
ETA PPU LYR		 29
ETA LYR		 30
ETA LYR		    
May 2020
SUN MON TUE WED THU FRI SAT
          1
ETA		 2
ETA
3
ELY ETA		 4
ELY ETA		 5
ELY ETA		 6
ELY ETA		 7
ELY ETA		 8
ELY ETA		 9
ELY ETA
10
ELY ETA		 11
ELY ETA		 12
ELY ETA		 13
ELY ETA		 14
ARI ELY ETA		 15
ARI ETA		 16
ARI ETA
17
ARI ETA		 18
ARI ETA		 19
ARI ETA		 20
ARI ETA		 21
ARI ETA		 22
ARI ETA		 23
ARI ETA
24
ARI ETA		 25
ARI ETA		 26
ARI ETA		 27
ARI ETA		 28
ARI ETA		 29
ARI		 30
ARI
31
ARI		            
June 2020
SUN MON TUE WED THU FRI SAT
  1
ARI		 2
ARI		 3
ARI		 4
ARI		 5
ARI		 6
ARI
7
ARI		 8
ARI		 9
ARI		 10
ARI		 11
ARI		 12
ARI		 13
ARI
14
ARI		 15
ARI		 16
ARI		 17
ARI		 18
ARI		 19
ARI		 20
ARI
21
ARI		 22
JBO ARI		 23
JBO ARI		 24
JBO ARI		 25
JBO		 26
JBO		 27
JBO
28
JBO		 29
JBO		 30
JBO		        
July 2020
SUN MON TUE WED THU FRI SAT
      1
JBO		 2
JBO		 3
CAP		 4
CAP
5
CAP		 6
CAP		 7
CAP		 8
CAP		 9
CAP		 10
CAP		 11
CAP
12
CAP SDA		 13
CAP SDA		 14
CAP SDA		 15
CAP SDA PAU		 16
CAP SDA PAU		 17
PER CAP SDA PAU		 18
PER CAP SDA PAU
19
PER CAP SDA PAU		 20
PER CAP SDA PAU		 21
PER CAP SDA PAU		 22
PER CAP SDA PAU		 23
PER CAP SDA PAU		 24
PER CAP SDA PAU		 25
PER CAP SDA PAU
26
PER CAP SDA PAU		 27
PER CAP SDA PAU		 28
PER CAP SDA PAU		 29
PER CAP SDA PAU		 30
PER CAP SDA PAU		 31
PER CAP SDA PAU		  
August 2020
SUN MON TUE WED THU FRI SAT
            1
PER CAP SDA PAU
2
PER CAP SDA PAU		 3
KCG PER CAP SDA PAU		 4
KCG PER CAP SDA PAU		 5
KCG PER CAP SDA PAU		 6
KCG PER CAP SDA PAU		 7
KCG PER CAP SDA PAU		 8
KCG PER CAP SDA PAU
9
KCG PER CAP SDA PAU		 10
KCG PER CAP SDA PAU		 11
KCG PER CAP SDA		 12
KCG PER CAP SDA		 13
KCG PER CAP SDA		 14
KCG PER CAP SDA		 15
KCG PER CAP SDA
16
KCG PER SDA		 17
KCG PER SDA		 18
KCG PER SDA		 19
KCG PER SDA		 20
KCG PER SDA		 21
KCG PER SDA		 22
KCG PER SDA
23
KCG PER SDA		 24
KCG PER		 25
KCG		 26 27 28
AUR		 29
AUR
30
AUR		 31
AUR		          
September 2020
SUN MON TUE WED THU FRI SAT
    1
AUR		 2
AUR		 3
AUR		 4
AUR		 5
SPE AUR
6
SPE		 7
SPE		 8
SPE		 9
DSX SPE		 10
STA DSX SPE		 11
STA DSX SPE		 12
STA DSX SPE
13
STA DSX SPE		 14
STA DSX SPE		 15
STA DSX SPE		 16
STA DSX SPE		 17
STA DSX SPE		 18
STA DSX SPE		 19
STA DSX SPE
20
STA DSX SPE		 21
STA DSX SPE		 22
STA DSX		 23
STA DSX		 24
STA DSX		 25
STA DSX		 26
STA DSX
27
STA DSX		 28
STA DSX		 29
STA DSX		 30
STA DSX		      
October 2020
SUN MON TUE WED THU FRI SAT
        1
STA DSX		 2
ORI STA DSX		 3
ORI STA DSX
4
ORI STA OCT DSX		 5
ORI STA OCT DSX		 6
ORI STA DRA OCT DSX		 7
ORI STA DRA DSX		 8
ORI STA DRA DSX		 9
ORI STA DRA DSX		 10
ORI DAU STA DRA
11
ORI DAU STA		 12
ORI DAU STA		 13
ORI DAU STA		 14
ORI EGE DAU STA		 15
ORI EGE DAU STA		 16
ORI EGE DAU STA		 17
ORI EGE DAU STA
18
ORI EGE DAU STA		 19
LMI ORI EGE STA		 20
NTA LMI ORI EGE STA		 21
NTA LMI ORI EGE STA		 22
NTA LMI ORI EGE STA		 23
NTA LMI ORI EGE STA		 24
NTA LMI ORI EGE STA
25
NTA LMI ORI EGE STA		 26
NTA LMI ORI EGE STA		 27
NTA LMI ORI EGE STA		 28
NTA ORI STA		 29
NTA ORI STA		 30
NTA ORI STA		 31
NTA ORI ST
November 2020
SUN MON TUE WED THU FRI SAT
1
NTA ORI STA		 2
NTA ORI STA		 3
NTA ORI STA		 4
NTA ORI STA		 5
NTA ORI STA		 6
LEO NTA ORI STA		 7
LEO NTA ORI STA
8
LEO NTA STA		 9
LEO NTA STA		 10
LEO NTA STA		 11
LEO NTA STA		 12
LEO NTA STA		 13
NOO LEO NTA STA		 14
NOO LEO NTA STA
15
NOO AMO LEO NTA STA		 16
NOO AMO LEO NTA STA		 17
NOO AMO LEO NTA STA		 18
NOO AMO LEO NTA STA		 19
NOO AMO LEO NTA STA		 20
NOO AMO LEO NTA STA		 21
NOO AMO LEO NTA
22
NOO AMO LEO NTA		 23
NOO AMO LEO NTA		 24
NOO AMO LEO NTA		 25
NOO AMO LEO NTA		 26
NOO LEO NTA		 27
NOO LEO NTA		 28
PHO NOO LEO NTA
29
PHO NOO LEO NTA		 30
PHO NOO LEO NTA		          
December 2020
SUN MON TUE WED THU FRI SAT
    1
PUP PHO NOO NTA		 2
PUP PHO NOO NTA		 3
HYD PUP PHO NOO NTA		 4
GEM HYD PUP PHO NOO NTA		 5
DLM GEM HYD MON PUP PHO NOO NTA
6
DLM GEM HYD MON PUP PHO NOO NTA		 7
DLM GEM HYD MON PUP PHO NTA		 8
DLM GEM HYD MON PUP PHO NTA		 9
DLM GEM HYD MON PUP PHO NTA		 10
DLM GEM HYD MON PUP NTA		 11
DLM GEM HYD MON PUP		 12
DLM COM GEM HYD MON PUP
13
DLM COM GEM HYD MON PUP		 14
DLM COM GEM HYD MON PUP		 15
DLM COM GEM HYD MON PUP		 16
DLM COM GEM HYD MON		 17
DLM URS COM GEM HYD MON		 18
DLM URS COM GEM HYD MON		 19
DLM URS COM GEM HYD MON
20
DLM URS COM GEM HYD MON		 21
DLM URS COM		 22
DLM URS COM		 23
DLM URS COM		 24
DLM URS		 25
DLM URS		 26
DLM URS
27
DLM		 28
DLM QUA		 29
DLM QUA		 30
DLM QUA		 31
DLM QUA		    

Meteor Shower Calendar 2019

Here’s our meteor shower calendar for 2019.  It is sourced from the IMO’s Working List of Visual Meteor Showers (https://www.imo.net/files/meteor-shower/cal2019.pdf, Table 5, p. 24).

Each meteor shower is identified using its three-character IAU meteor shower code.  Codes are bold on the date of maximum, and one day either side of maximum.

Here’s a printable PDF file of the meteor shower calendar shown below:

Meteor Calendar 2019Download

Happy meteor watching!


January 2019

SUN MON TUE WED THU FRI SAT
    1
DLM QUA		 2
DLM QUA		 3
DLM QUA		 4
DLM QUA		 5
DLM QUA
6
DLM QUA		 7
DLM QUA		 8
DLM QUA		 9
DLM QUA		 10
DLM QUA GUM		 11
DLM QUA GUM		 12
DLM QUA GUM
13
DLM GUM		 14
DLM GUM		 15
DLM GUM		 16
DLM GUM		 17
DLM GUM		 18
DLM GUM		 19
DLM GUM
20
DLM GUM		 21
DLM GUM		 22
DLM GUM		 23
DLM		 24
DLM		 25
DLM		 26
DLM
27
DLM		 28
DLM		 29
DLM		 30
DLM		 31
DLM ACE		    


February 2019

SUN MON TUE WED THU FRI SAT
          1
DLM ACE		 2
DLM ACE
3
DLM ACE		 4
DLM ACE		 5
ACE		 6
ACE		 7
ACE		 8
ACE		 9
ACE
10
ACE		 11
ACE		 12
ACE		 13
ACE		 14
ACE		 15
ACE		 16
ACE
17
ACE		 18
ACE		 19
ACE		 20
ACE		 21 22 23
24 25
GNO		 26
GNO		 27
GNO		 28
GNO		    


March 2019

SUN MON TUE WED THU FRI SAT
          1
GNO		 2
GNO
3
GNO		 4
GNO		 5
GNO		 6
GNO		 7
GNO		 8
GNO		 9
GNO
10
GNO		 11
GNO		 12
GNO		 13
GNO		 14
GNO		 15
GNO		 16
GNO
17
GNO		 18
GNO		 19
GNO		 20
GNO		 21
GNO		 22
GNO		 23
GNO
24
GNO		 25
GNO		 26
GNO		 27
GNO		 28
GNO		 29 30
31            


April 2019

SUN MON TUE WED THU FRI SAT
  1 2 3 4 5 6
7 8 9 10 11 12 13
14
LYR		 15
PPU LYR		 16
PPU LYR		 17
PPU LYR		 18
PPU LYR		 19
ETA PPU LYR		 20
ETA PPU LYR
21
ETA PPU LYR		 22
ETA PPU LYR		 23
ETA PPU LYR		 24
ETA PPU LYR		 25
ETA PPU LYR		 26
ETA PPU LYR		 27
ETA PPU LYR
28
ETA PPU LYR		 29
ETA LYR		 30
ETA LYR		        


May 2019

SUN MON TUE WED THU FRI SAT
      1
ETA		 2
ETA		 3
ELY ETA		 4
ELY ETA
5
ELY ETA		 6
ELY ETA		 7
ELY ETA		 8
ELY ETA		 9
ELY ETA		 10
ELY ETA		 11
ELY ETA
12
ELY ETA		 13
ELY ETA		 14
ARI ELY ETA		 15
ARI ETA		 16
ARI ETA		 17
ARI ETA		 18
ARI ETA
19
ARI ETA		 20
ARI ETA		 21
ARI ETA		 22
ARI ETA		 23
ARI ETA		 24
ARI ETA		 25
ARI ETA
26
ARI ETA		 27
ARI ETA		 28
ARI ETA		 29
ARI		 30
ARI		 31
ARI		  


June 2019

SUN MON TUE WED THU FRI SAT
            1
ARI
2
ARI		 3
ARI		 4
ARI		 5
ARI		 6
ARI		 7
ARI		 8
ARI
9
ARI		 10
ARI		 11
ARI		 12
ARI		 13
ARI		 14
ARI		 15
ARI
16
ARI		 17
ARI		 18
ARI		 19
ARI		 20
ARI		 21
ARI		 22
JBO ARI
23
JBO ARI		 24
JBO ARI		 25
JBO		 26
JBO		 27
JBO		 28
JBO		 29
JBO
30
JBO		            


July 2019

SUN MON TUE WED THU FRI SAT
  1
JBO		 2
JBO		 3
CAP		 4
CAP		 5
CAP		 6
CAP
7
CAP		 8
CAP		 9
CAP		 10
CAP		 11
CAP		 12
CAP SDA		 13
CAP SDA
14
CAP SDA		 15
CAP SDA PAU		 16
CAP SDA PAU		 17
PER CAP SDA PAU		 18
PER CAP SDA PAU		 19
PER CAP SDA PAU		 20
PER CAP SDA PAU
21
PER CAP SDA PAU		 22
PER CAP SDA PAU		 23
PER CAP SDA PAU		 24
PER CAP SDA PAU		 25
PER CAP SDA PAU		 26
PER CAP SDA PAU		 27
PER CAP SDA PAU
28
PER CAP SDA PAU		 29
PER CAP SDA PAU		 30
PER CAP SDA PAU		 31
PER CAP SDA PAU		      


August 2019

SUN MON TUE WED THU FRI SAT
        1
PER CAP SDA PAU		 2
PER CAP SDA PAU		 3
KCG PER CAP SDA PAU
4
KCG PER CAP SDA PAU		 5
KCG PER CAP SDA PAU		 6
KCG PER CAP SDA PAU		 7
KCG PER CAP SDA PAU		 8
KCG PER CAP SDA PAU		 9
KCG PER CAP SDA PAU		 10
KCG PER CAP SDA PAU
11
KCG PER CAP SDA		 12
KCG PER CAP SDA		 13
KCG PER CAP SDA		 14
KCG PER CAP SDA		 15
KCG PER CAP SDA		 16
KCG PER SDA		 17
KCG PER SDA
18
KCG PER SDA		 19
KCG PER SDA		 20
KCG PER SDA		 21
KCG PER SDA		 22
KCG PER SDA		 23
KCG PER SDA		 24
KCG PER
25
KCG		 26 27 28
AUR		 29
AUR		 30
AUR		 31
AUR


September 2019

SUN MON TUE WED THU FRI SAT
1
AUR		 2
AUR		 3
AUR		 4
AUR		 5
SPE AUR		 6
SPE		 7
SPE
8
SPE		 9
DSX SPE		 10
STA DSX SPE		 11
STA DSX SPE		 12
STA DSX SPE		 13
STA DSX SPE		 14
STA DSX SPE
15
STA DSX SPE		 16
STA DSX SPE		 17
STA DSX SPE		 18
STA DSX SPE		 19
STA DSX SPE		 20
STA DSX SPE		 21
STA DSX SPE
22
STA DSX		 23
STA DSX		 24
STA DSX		 25
STA DSX		 26
STA DSX		 27
STA DSX		 28
STA DSX
29
STA DSX		 30
STA DSX		          


October 2019

SUN MON TUE WED THU FRI SAT
    1
STA DSX		 2
ORI STA DSX		 3
ORI STA DSX		 4
ORI STA DSX		 5
ORI STA OCT DSX
6
ORI STA DRA OCT DSX		 7
ORI STA DRA OCT DSX		 8
ORI STA DRA DSX		 9
ORI STA DRA DSX		 10
ORI DAU STA DRA		 11
ORI DAU STA		 12
ORI DAU STA
13
ORI DAU STA		 14
ORI EGE DAU STA		 15
ORI EGE DAU STA		 16
ORI EGE DAU STA		 17
ORI EGE DAU STA		 18
ORI EGE DAU STA		 19
LMI ORI EGE STA
20
NTA LMI ORI EGE STA		 21
NTA LMI ORI EGE STA		 22
NTA LMI ORI EGE STA		 23
NTA LMI ORI EGE STA		 24
NTA LMI ORI EGE STA		 25
NTA LMI ORI EGE STA		 26
NTA LMI ORI EGE STA
27
NTA LMI ORI EGE STA		 28
NTA ORI STA		 29
NTA ORI STA		 30
NTA ORI STA		 31
NTA ORI STA		    


November 2019

SUN MON TUE WED THU FRI SAT
          1
NTA ORI STA		 2
NTA ORI STA
3
NTA ORI STA		 4
NTA ORI STA		 5
NTA ORI STA		 6
LEO NTA ORI STA		 7
LEO NTA ORI STA		 8
LEO NTA STA		 9
LEO NTA STA
10
LEO NTA STA		 11
LEO NTA STA		 12
LEO NTA STA		 13
NOO LEO NTA STA		 14
NOO LEO NTA STA		 15
NOO AMO LEO NTA STA		 16
NOO AMO LEO NTA STA
17
NOO AMO LEO NTA STA		 18
NOO AMO LEO NTA STA		 19
NOO AMO LEO NTA STA		 20
NOO AMO LEO NTA STA		 21
NOO AMO LEO NTA		 22
PHO NOO AMO LEO NTA		 23
PHO NOO AMO LEO NTA
24
PHO NOO AMO LEO NTA		 25
PHO NOO AMO LEO NTA		 26
PHO NOO LEO NTA		 27
PHO NOO LEO NTA		 28
PHO NOO LEO NTA		 29
PHO NOO LEO NTA		 30
PHO NOO LEO NTA


December 2019

SUN MON TUE WED THU FRI SAT
1
PUP PHO NOO NTA		 2
PUP PHO NOO NTA		 3
HYD PUP PHO NOO NTA		 4
GEM HYD PUP PHO NOO NTA		 5
DLM GEM HYD MON PUP PHO NOO NTA		 6
DLM GEM HYD MON PUP PHO NOO NTA		 7
DLM GEM HYD MON PUP PHO NTA
8
DLM GEM HYD MON PUP PHO NTA		 9
DLM GEM HYD MON PUP PHO NTA		 10
DLM GEM HYD MON PUP NTA		 11
DLM GEM HYD MON PUP		 12
DLM COM GEM HYD MON PUP		 13
DLM COM GEM HYD MON PUP		 14
DLM COM GEM HYD MON PUP
15
DLM COM GEM HYD MON PUP		 16
DLM COM GEM MON		 17
DLM URS COM GEM MON		 18
DLM URS COM MON		 19
DLM URS COM MON		 20
DLM URS COM MON		 21
DLM URS COM
22
DLM URS COM		 23
DLM URS COM		 24
DLM URS		 25
DLM URS		 26
DLM URS		 27
DLM		 28
DLM QUA
29
DLM QUA		 30
DLM QUA		 31
DLM QUA		        

Neptune, the Mystic

Many years ago I wrote a short poem while listening to the final and most otherworldly section of The Planets by Gustav Holst: Neptune, the Mystic.

Here it is:

Neptune, the Mystic from The Planets by Gustav Holst
Royal Philharmonic Orchestra, Vernon Handley
Ambrosian Chorus, John McCarthy
Alto ALC 1013
The endless poetry of space
Sends shivers across my spine,
And there upon the threshold sounds
The now distant drone of time.
Music fills the spacecraft
Starlight fills the night,
And there upon the threshold think
I wonder, was I right?
David Oesper

 

The Planets was written by Holst between 1914 and 1916, and the premiere performance was at The Queen’s Hall, London, on September 29, 1918.  Adrian Boult conducted the orchestra in a private performance for about 250 invited guests.  The Queen’s Hall was destroyed by an incendiary bomb during the London Blitz in 1941, seven years after Holst’s death in 1934.

Pluto was discovered by Clyde Tombaugh in 1930, and was considered to be the ninth planet until its controversial demotion by the IAU in 2006.  A number of composers have added a Pluto movement to The Planets (“Pluto, the Renewer” by Colin Matthews, for example), and even an improvised performance (“Pluto, the Unpredictable”) by Leonard Bernstein and the New York Philharmonic.  I remember enjoying “Pluto, the Unknown” by American composer Peter Hamlin performed by the Des Moines Symphony in 1992, but unfortunately no recording of this work exists.

Meteor Shower Calendar 2018

Here’s our meteor shower calendar for 2018.  It is sourced from the IMO’s Working List of Visual Meteor Showers (https://www.imo.net/files/meteor-shower/cal2018.pdf, Table 5, p. 25).

Each meteor shower is identified using its three-character IAU meteor shower code.  Codes are bold on the date of maximum, and one day either side of maximum.

Here’s a printable PDF file of the meteor shower calendar shown below:

Meteor Shower Calendar 2018

Happy meteor watching!

January 2018
SUN MON TUE WED THU FRI SAT
1
DLM QUA		 2
DLM QUA		 3
DLM QUA		 4
DLM QUA		 5
DLM QUA		 6
DLM QUA
7
DLM QUA		 8
DLM QUA		 9
DLM QUA		 10
DLM QUA GUM		 11
DLM QUA GUM		 12
DLM QUA GUM		 13
DLM GUM
14
DLM GUM		 15
DLM GUM		 16
DLM GUM		 17
DLM GUM		 18
DLM GUM		 19
DLM GUM		 20
DLM GUM
21
DLM GUM		 22
DLM GUM		 23
DLM		 24
DLM		 25
DLM		 26
DLM		 27
DLM
28
DLM		 29
DLM		 30
DLM		 31
DLM ACE
February 2018
SUN MON TUE WED THU FRI SAT
1
DLM ACE		 2
DLM ACE		 3
DLM ACE
4
DLM ACE		 5
ACE		 6
ACE		 7
ACE		 8
ACE		 9
ACE		 10
ACE
11
ACE		 12
ACE		 13
ACE		 14
ACE		 15
ACE		 16
ACE		 17
ACE
18
ACE		 19
ACE		 20
ACE		 21 22 23 24
25
GNO		 26
GNO		 27
GNO		 28
GNO
March 2018
SUN MON TUE WED THU FRI SAT
1
GNO		 2
GNO		 3
GNO
4
GNO		 5
GNO		 6
GNO		 7
GNO		 8
GNO		 9
GNO		 10
GNO
11
GNO		 12
GNO		 13
GNO		 14
GNO		 15
GNO		 16
GNO		 17
GNO
18
GNO		 19
GNO		 20
GNO		 21
GNO		 22
GNO		 23
GNO		 24
GNO
25
GNO		 26
GNO		 27
GNO		 28
GNO		 29 30 31
April 2018
SUN MON TUE WED THU FRI SAT
1 2 3 4 5 6 7
8 9 10 11 12 13 14
LYR
15
PPU LYR		 16
PPU LYR		 17
PPU LYR		 18
PPU LYR		 19
ETA PPU LYR		 20
ETA PPU LYR		 21
ETA PPU LYR
22
ETA PPU LYR		 23
ETA PPU LYR		 24
ETA PPU LYR		 25
ETA PPU LYR		 26
ETA PPU LYR		 27
ETA PPU LYR		 28
ETA PPU LYR
29
ETA LYR		 30
ETA LYR
May 2018
SUN MON TUE WED THU FRI SAT
1
ETA		 2
ETA		 3
ELY ETA		 4
ELY ETA		 5
ELY ETA
6
ELY ETA		 7
ELY ETA		 8
ELY ETA		 9
ELY ETA		 10
ELY ETA		 11
ELY ETA		 12
ELY ETA
13
ELY ETA		 14
ARI ELY ETA		 15
ARI ETA		 16
ARI ETA		 17
ARI ETA		 18
ARI ETA		 19
ARI ETA
20
ARI ETA		 21
ARI ETA		 22
ARI ETA		 23
ARI ETA		 24
ARI ETA		 25
ARI ETA		 26
ARI ETA
27
ARI ETA		 28
ARI ETA		 29
ARI		 30
ARI		 31
ARI
June 2018
SUN MON TUE WED THU FRI SAT
1
ARI		 2
ARI
3
ARI		 4
ARI		 5
ARI		 6
ARI		 7
ARI		 8
ARI		 9
ARI
10
ARI		 11
ARI		 12
ARI		 13
ARI		 14
ARI		 15
ARI		 16
ARI
17
ARI		 18
ARI		 19
ARI		 20
ARI		 21
ARI		 22
JBO ARI		 23
JBO ARI
24
JBO ARI		 25
JBO		 26
JBO		 27
JBO		 28
JBO		 29
JBO		 30
JBO
July 2018
SUN MON TUE WED THU FRI SAT
1
JBO		 2
JBO		 3
CAP		 4
CAP		 5
CAP		 6
CAP		 7
CAP
8
CAP		 9
CAP		 10
CAP		 11
CAP		 12
CAP SDA		 13
CAP SDA		 14
CAP SDA
15
CAP SDA PAU		 16
CAP SDA PAU		 17
PER CAP SDA PAU		 18
PER CAP SDA PAU		 19
PER CAP SDA PAU		 20
PER CAP SDA PAU		 21
PER CAP SDA PAU
22
PER CAP SDA PAU		 23
PER CAP SDA PAU		 24
PER CAP SDA PAU		 25
PER CAP SDA PAU		 26
PER CAP SDA PAU		 27
PER CAP SDA PAU		 28
PER CAP SDA PAU
29
PER CAP SDA PAU		 30
PER CAP SDA PAU		 31
PER CAP SDA PAU
August 2018
SUN MON TUE WED THU FRI SAT
1
PER CAP SDA PAU		 2
PER CAP SDA PAU		 3
KCG PER CAP SDA PAU		 4
KCG PER CAP SDA PAU
5
KCG PER CAP SDA PAU		 6
KCG PER CAP SDA PAU		 7
KCG PER CAP SDA PAU		 8
KCG PER CAP SDA PAU		 9
KCG PER CAP SDA PAU		 10
KCG PER CAP SDA PAU		 11
KCG PER CAP SDA
12
KCG PER CAP SDA		 13
KCG PER CAP SDA		 14
KCG PER CAP SDA		 15
KCG PER CAP SDA		 16
KCG PER SDA		 17
KCG PER SDA		 18
KCG PER SDA
19
KCG PER SDA		 20
KCG PER SDA		 21
KCG PER SDA		 22
KCG PER SDA		 23
KCG PER SDA		 24
KCG PER		 25
KCG
26 27 28
AUR		 29
AUR		 30
AUR		 31
AUR
September 2018
SUN MON TUE WED THU FRI SAT
1
AUR
2
AUR		 3
AUR		 4
AUR		 5
SPE AUR		 6
SPE		 7
SPE		 8
SPE
9
DSX SPE		 10
STA DSX SPE		 11
STA DSX SPE		 12
STA DSX SPE		 13
STA DSX SPE		 14
STA DSX SPE		 15
STA DSX SPE
16
STA DSX SPE		 17
STA DSX SPE		 18
STA DSX SPE		 19
STA DSX SPE		 20
STA DSX SPE		 21
STA DSX SPE		 22
STA DSX
23
STA DSX		 24
STA DSX		 25
STA DSX		 26
STA DSX		 27
STA DSX		 28
STA DSX		 29
STA DSX
30
STA DSX
October 2018
SUN MON TUE WED THU FRI SAT
1
STA DSX		 2
ORI STA DSX		 3
ORI STA DSX		 4
ORI STA DSX		 5
ORI STA OCT DSX		 6
ORI STA DRA OCT DSX
7
ORI STA DRA OCT DSX		 8
ORI STA DRA DSX		 9
ORI STA DRA DSX		 10
ORI DAU STA DRA		 11
ORI DAU STA		 12
ORI DAU STA		 13
ORI DAU STA
14
ORI EGE DAU STA		 15
ORI EGE DAU STA		 16
ORI EGE DAU STA		 17
ORI EGE DAU STA		 18
ORI EGE DAU STA		 19
LMI ORI EGE STA		 20
NTA LMI ORI EGE STA
21
NTA LMI ORI EGE STA		 22
NTA LMI ORI EGE STA		 23
NTA LMI ORI EGE STA		 24
NTA LMI ORI EGE STA		 25
NTA LMI ORI EGE STA		 26
NTA LMI ORI EGE STA		 27
NTA LMI ORI EGE STA
28
NTA ORI STA		 29
NTA ORI STA		 30
NTA ORI STA		 31
NTA ORI STA
November 2018
SUN MON TUE WED THU FRI SAT
1
NTA ORI STA		 2
NTA ORI STA		 3
NTA ORI STA
4
NTA ORI STA		 5
NTA ORI STA		 6
LEO NTA ORI STA		 7
LEO NTA ORI STA		 8
LEO NTA STA		 9
LEO NTA STA		 10
LEO NTA STA
11
LEO NTA STA		 12
LEO NTA STA		 13
NOO LEO NTA STA		 14
NOO LEO NTA STA		 15
NOO AMO LEO NTA STA		 16
NOO AMO LEO NTA STA		 17
NOO AMO LEO NTA STA
18
NOO AMO LEO NTA STA		 19
NOO AMO LEO NTA STA		 20
NOO AMO LEO NTA STA		 21
NOO AMO LEO NTA		 22
NOO AMO LEO NTA		 23
NOO AMO LEO NTA		 24
NOO AMO LEO NTA
25
NOO AMO LEO NTA		 26
NOO LEO NTA		 27
NOO LEO NTA		 28
PHO NOO LEO NTA		 29
PHO NOO LEO NTA		 30
PHO NOO LEO NTA
December 2018
SUN MON TUE WED THU FRI SAT
1
PUP PHO NOO NTA
2
PUP PHO NOO NTA		 3
HYD PUP PHO NOO NTA		 4
GEM HYD PUP PHO NOO NTA		 5
DLM GEM HYD MON PUP PHO NOO NTA		 6
DLM GEM HYD MON PUP PHO NOO NTA		 7
DLM GEM HYD MON PUP PHO NTA		 8
DLM GEM HYD MON PUP PHO NTA
9
DLM GEM HYD MON PUP PHO NTA		 10
DLM GEM HYD MON PUP NTA		 11
DLM GEM HYD MON PUP		 12
DLM COM GEM HYD MON PUP		 13
DLM COM GEM HYD MON PUP		 14
DLM COM GEM HYD MON PUP		 15
DLM COM GEM HYD MON PUP
16
DLM COM GEM MON		 17
DLM URS COM GEM MON		 18
DLM URS COM MON		 19
DLM URS COM MON		 20
DLM URS COM MON		 21
DLM URS COM		 22
DLM URS COM
23
DLM URS COM		 24
DLM URS		 25
DLM URS		 26
DLM URS		 27
DLM		 28
DLM QUA		 29
DLM QUA
30
DLM QUA		 31
DLM QUA

Eugène Delporte and the Constellation Jigsaw

Belgian astronomer Eugène Joseph Delporte (1882-1955) discovered 66 asteroids from 1925 to 1942, but he is best remembered for determining the official boundaries of the 88 constellations, work he completed in 1928 and published in 1930.  The constellation boundaries have remained unchanged since then.

The International Astronomical Union (IAU), founded, incidentally, in Brussels, Belgium in 1919, established the number of constellations at 88—the same number, coincidentally, as the keys on a piano—in 1922 under the guidance of American astronomer Henry Norris Russell (1877-1957).  The IAU officially adopted Delporte’s constellation boundaries in 1928.

All the constellation boundaries lie along lines of constant right ascension and declination—as they existed in the year 1875. Why 1875 and not 1900, 1925, or 1930? American astronomer Benjamin Gould (1824-1896) had already drawn up southern constellation boundaries for epoch 1875, and Delporte built upon Gould’s earlier work.

As the direction of the Earth’s polar axis slowly changes due to precession, the constellation boundaries gradually tilt so that they no longer fall upon lines of constant right ascension and declination. Eventually, the tilt of the constellation boundaries will become large enough that the boundaries will probably be redefined to line up with the equatorial coordinate grid for some future epoch. When that happens, some borderline stars will move into an adjacent constellation. Even now, every year some stars change constellations because proper motion causes them to move across a constellation boundary. For faint stars, this happens frequently, but for bright stars such a constellation switch is exceedingly rare.