Nearest Exoplanets

There are 33 confirmed exoplanets within 15 light years of our solar system, with more certainly on the way as a number of unconfirmed exoplanets are under ongoing investigation.

Here’s a table of all known planets within 15 light years of the Sun, including the eight planets of our own solar system for comparison.

Click the link below for a more convenient view of the entire table in a separate tab.

Planet mass and radius are given in terms of Earth’s mass and radius. The reason the radius of all the exoplanets listed here is “unknown” is because all of these planets have been detected using the radial velocity and/or astrometric method. Only the transit method provides a reliable way to measure an exoplanet’s size, but the nearest stars that host transiting exoplanets are 21.3 ly and 22.4 ly distant (HD 219134 and LTT 1445, respectively). Our limit here is 15 ly.

A side note about transiting exoplanets. In order for us to see an exoplanet transiting its host star, the exoplanet’s orbital plane has to be fortuitously aligned quite close to our line of sight. Since even these nearest stars are very far away in comparison to the size of our solar system, we are stuck with the line of sight we have. What percentage of all exoplanets out there might we detect using the transit method? That depends, of course, on the orientation of the exoplanet’s orbital plane but also the size of the star (and the planet if it is large) and the distance of the exoplanet from that star. Roughly, only about 1 in 200 exoplanets or about 0.5% can be detected using the transit method.

Luminosity is the host star’s luminosity in terms of our Sun’s luminosity. Bolometric luminosity is used where available; otherwise, optical luminosity is used.

The average distance of the planet from the star is calculated from the semi-major axis and the orbital eccentricity. We then calculate the incident stellar flux using the average distance of the planet from the star and the luminosity of the star, normalized to what the Earth receives (0.9997 and not 1.oooo because the Earth, on average, is more than 1 AU from the Sun). The relevant equation is:

\frac{\textrm{L}}{\bar{\textrm{d}}^{2}}\cdot\phi_{\oplus }

where L is the luminosity of the star in terms of the Sun’s luminosity
   and d-bar is the average distance of the planet from the star in AU
   and Φ is the incident stellar flux at Earth’s average distance from the Sun
             in proportional units of solar luminosities per AU2

This calculation, of course, makes no assumptions about the albedo of the planet nor whatever atmosphere the planet may or may not have. It is simply a calculation of stellar radiation per unit area received at the planet’s distance from the star.

Here’s an example from the table. Mercury, on average, receives 6.4 times as much energy per unit area as does the Earth, whereas Neptune receives only 0.0011 as much as the Earth.

Some Key Takeaways

  • The most luminous star that is known to host exoplanets within 15 light years of our solar system, Epsilon Eridani, is only 32% as bright as the Sun.
  • Eight of these exoplanets receive an amount of energy from their star that is comparable to what the Earth receives from the Sun: Gliese 1061 d (0.56), Proxima Centauri b (0.66), Gliese 687 b (0.78), Luyten’s Star b (1.05), Teegarden’s Star b (1.07), Wolf 1061 c (1.37), Gliese 1061 c (1.40), and Ross 128 b (1.42).
  • The most massive of these exoplanets is Epsilon Eridani b, weighing in at 311 earth-masses, comparable to Jupiter in our own solar system (318).

I’d like to conclude by noting that I will do my best to keep this table up-to-date, but if you see something that needs changing before I do, by all means post a comment here and I will make the correction or addition.

Kakistocracy and Trump

From the ever-impressive Oxford English Dictionary:

kakistocracy – The government of a state by the worst citizens.

The OED cites the first known use of the word kakistocracy back in 1644:
“mad kinde of Kakistocracy”

And in 1876:
“Is ours a government of the people, by the people, for the people, or a Kakistocracy rather, for the benefit of knaves at the cost of fools?”

And in 1879:
“The..régime is at once a plutocracy and a kakistocracy.”


In preparing for a course on Gustav Holst I will be teaching this summer, I recently came across a curious phrase in a letter written by Gustav’s great-uncle Theodore von Holst on October 13, 1832:

“They told us that Costa of the Opera gave a Concert there with Vigano, Tamburini, Donzelli, Grisi and other Trumps, but none of the Brightonian Nobs would patronise it…”

Again turning to the OED, I found the following:

trump – To deceive, cheat
Citations of this transitive verb are given for 1487-1631.

trump – A thing of small value, a trifle
Cited use of this noun is in 1513

trump – To give forth a trumpet-like sound; spec. to break wind audibly (slang or colloquial)
Citations of this intransitive verb are given for c. 1425 – 1845

Minor Planets Named After Their Discoverers

To the best of my knowledge, only 18 minor planets have been named after their discoverers. While the discoverer has first naming rights, they cannot name a minor planet after themselves, though they can (and sometimes do) name a minor planet after a spouse, parent, or child.

Of course, many minor planet discoverers have minor planets named after them, but almost always these are discoveries by someone else who decides to name one of “their” minor planets after the other discoverer.

In the rare situation when someone decides (and has the authority) to name a discoverer’s minor planet after the discoverer, it is almost always a posthumous honor. Comet discoveries, on the other hand, are automatically named after their discoverer(s).

I have reader Rafael to thank for letting me know that Eugène Delporte does indeed have an asteroid he discovered named after him (see comments after Eugène Delporte and the Constellation Jigsaw) and this got me wondering if there were other examples. I wrote a SAS program to do some fuzzy matching between asteroid name and asteroid discoverer, and came up with the following list. Let me know if there are any others I missed, and I will include them here.

792 Metcalfia
Discovered 1907 Mar 20 by Joel Hastings Metcalf (1866-1925) at Taunton, Massachusetts.

989 Schwassmannia
Discovered 1922 Nov 18 by Arnold Schwassmann (1870-1964) at Bergedorf, Germany.

1074 Beljawskya
Discovered 1925 Jan 26 by Sergey Ivanovich Belyavskij (1883-1953) at Simeïs, Crimea.

1111 Reinmuthia
Discovered 1927 Feb 11 by Karl Reinmuth (1892-1979) at Heidelberg, Germany.

1274 Delportia
Discovered 1932 Nov 28 by Eugène J. Delporte (1882-1955) at Uccle, Belgium.

1596 Itzigsohn
Discovered 1951 Mar 8 by Miguel Itzigsohn (1908–1978) at La Plata, Argentina.

1648 Shajna
Discovered 1935 Sep 5 by Pelageya Fedorovna Shajn (1894-1956) at Simeïs, Crimea.

1655 Comas Solá
Discovered 1929 Nov 28 by José Comas Solá (1868-1937) at Barcelona, Spain.

1666 van Gent
Discovered 1930 Jul 22 by Hendrik van Gent (1899-1947) at Johannesburg, South Africa.

1777 Gehrels
Discovered 1960 Sep 24 by C. J. van Houten, I. van Houten-Groeneveld, and Tom Gehrels (1925-2011) at Palomar Mountain, California.

1927 Suvanto
Discovered 1936 Mar 18 by Rafael Suvanto (1909-1940) at Turku, Finland.

2044 Wirt
Discovered 1950 Nov 8 by Carl A. Wirtanen (1910-1990) at Mount Hamilton, California.

2246 Bowell
Discovered 1979 Dec 14 by Edward L. G. Bowell (1943-2023) at Anderson Mesa, Arizona.

3019 Kulin
Discovered 1940 Jan 7 by György Kulin (1905-1989) at Budapest, Hungary.

5540 Smirnova
Discovered 1971 Aug 30 by Tamara Mikhajlovna Smirnova (1935-2001) at Nauchnyj, Crimea.

5900 Jensen
Discovered 1986 Oct 3 by Poul B. Jensen (?-) at Brorfelde, Denmark.

19911 Rigaux
Discovered 1933 Mar 26 by Fernand Rigaux (1905-1962) at Uccle, Belgium.

96747 Crespodasilva
Discovered 1999 Aug 16 by Lucy d’Escoffier Crespo da Silva (1978-2000) at Westford, Massachusetts.

Incidentally, here are the three most prolific minor planet discoverers that still have an unnamed minor planet discovery that could be named after them. There are, of course, many others who deserve this honor.

Eleanor F. Helin (1932-2009)
Even though 3267 Glo is named after her nickname “Glo”, why not designate one of her discoveries as Helin or Eleanor Helin or Eleanorhelin? There are many still available, beginning with 5131 (1990 BG).

Carolyn Shoemaker (1929-2021)
Though 4446 Carolyn is named after her, why not designate one of her discoveries as Carolyn Shoemaker or Carolynshoemaker? There are many still available, beginning with 48576 (1994 NN2).

Gary Hug (1950-)
There are many still available, including 32165 (1998 FS92).

Classical Music Timeline: 2020s

This is one of a series of postings of important classical music dates, from the 17th century to the present. Included are the date and location of the birth and death of composers, and the premiere date and location of the first public performance of works. When the premiere date and location is unknown, the date or year of completion of the work is given. Though reasonably comprehensive, this is a subjective list, so the choice of composers and works is mine. If you find any errors, or if you can offer a premiere date and location for a work where only the completion date or year is listed, please post a comment here.

2023
January 18 – Clytus Gottwald (1925-2023) died in Ditzingen, Germany

August 3 – Carl Davis (1936-2023) died in Oxford, England

August 19 – Gloria Coates (1933-2023) died in Munich, Germany

2024
January 16 – Peter Schickele (1935-2024) died in Bearsville, New York

2010s

2030s→

The Mysterious Case of 55 Herculis

55 Her (near 54 Her, shown above) was visible as late as 1782, but by 1791 it had disappeared
(Click on the image above for a larger view.)

I was fascinated to read the letter from Oleksiy V. Arkhypov (Kharkiv, Ukraine) in the February 2025 issue of Sky & Telescope, p. 6, where he describes a 5th-magnitude star in the constellation Hercules that has apparently disappeared. John Flamsteed (1646-1719) had recorded the star at the end of the 17th century. Flamsteed listed the brighter stars in each constellation in order of right ascension at the time, but did not number them. That task fell to Joseph Jérôme de Lalande (1732–1807) who assigned what we now know as the “Flamsteed numbers” to each of the stars in Flamsteed’s catalogue. Two adjacent stars in Hercules in Flamsteed’s catalogue were given the designations 54 Her and 55 Her.

William Herschel (1738-1822) observed both stars on October 10, 1781 (and had noted that they were both red in color) and again on April 11, 1782, but on May 24, 1791 (and afterwards), only 54 Her was visible. Apparently, 55 Her disappeared from sight between 1782 and 1791, and it hasn’t been seen since.

In Herschel’s own words:

On the Disappearance of the 55th Herculis.

Among the changes that happen in the sidereal heavens we enumerate the loss of stars; but, notwithstanding the real destruction of an heavenly body may not be impossible, we have some reasons to think that the disappearance of a star is probably owing to causes which are of the same nature with those that act upon periodical stars, when they occasion their temporary occultations. This subject, however, being of great extent and consequence, we shall not enter into it at present, but only relate a recent instance of the kind.

Two stars of the 5th magnitude, whose places we find inserted in all our best catalogues, were to be seen in the neck of Hercules. They are the 54th and 55th of Flamsteed’s, in that constellation. In the year 1781, the 10th of October, I examined them both, and marked down their colour, red. The 11th of April, 1782, I looked at them again, and noted my having seen them distinctly, with a power of 460; and that they were single stars.

The 24th of last May, I missed one of the two, and examining the spot again the 25th, and many times afterwards, found that one of them was not to be seen. The situation of the stars is such that, not having fixed instruments, I could not well determine which of the two was the lost one. I therefore requested the favour of my much esteemed friend, the astronomer royal, to ascertain the remaining star ; and it appears from Dr. Maskelyne’s answer to my letter, that the 55th Herculis is the one which we have lost.

The coordinates for 54 Her are:
α2000 = 16h 55m 22s, δ2000 = +18° 26′ 00″

Classical Music Timeline: 2010s

This is one of a series of postings of important classical music dates, from the 17th century to the present. Included are the date and location of the birth and death of composers, and the premiere date and location of the first public performance of works. When the premiere date and location is unknown, the date or year of completion of the work is given. Though reasonably comprehensive, this is a subjective list, so the choice of composers and works is mine. If you find any errors, or if you can offer a premiere date and location for a work where only the completion date or year is listed, please post a comment here.

2010
April 22 – Double Concerto for Violin, Cello, and Orchestra by Philip Glass (1937-) was first performed in The Hague, South Holland, Netherlands

November 2 – Rudolf Barshai (1924-2010) died in Basel, Switzerland

2011
Alma Deutscher (2005-) completed Piano Sonata in E-flat Major

Amanda Harberg (1973-) completed Concerto for Viola and Orchestra

December 15 – Krasimir Kyurkchiyski (1936-2011) died in Sofia, Bulgaria

2016
May 5 – Isao Tomita (1932-2016) died in Tokyo, Japan

July 27 – Einojuhani Rautavaara (1929-2016) died in Helsinki, Finland

2017
January 21 – Veljo Tormis (1930-2017) died in Tallinn, Estonia

2018
Alma Deutscher (2005-) completed I Think of You, for piano

Alma Deutscher (2005-) completed In Memoriam (from Piano Concerto, 2nd movement: Adagio), for piano

2019
Alma Deutscher (2005-) completed Impromptu in C minor, “The Chase”, for piano

Alma Deutscher (2005-) completed Siren Sounds Waltz, for piano

Alma Deutscher (2005-) completed Sixty Minutes Polka, for piano

Alma Deutscher (2005-) completed The Lonely Pine-Tree, for piano

Alma Deutscher (2005-) completed “The Star of Hope” (from the opera Cinderella), for piano

Alma Deutscher (2005-) completed “When the Day Falls Into Darkness” (from the opera Cinderella), for piano

February 17 – Deux Sérénades, for violin and orchestra, by Einojuhani Rautavaara (1929-2016) was first performed in Paris, France

February 20 – Dominick Argento (1927-2019) died in Minneapolis, Minnesota

May 10 – “Inferno” (Part 1 of Dante) by Thomas Adès (1971-) was first performed in Los Angeles, California

2000s

2020s

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 −20C 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 −20C 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.

Classical Music Timeline: 2000s

This is one of a series of postings of important classical music dates, from the 17th century to the present. Included are the date and location of the birth and death of composers, and the premiere date and location of the first public performance of works. When the premiere date and location is unknown, the date or year of completion of the work is given. Though reasonably comprehensive, this is a subjective list, so the choice of composers and works is mine. If you find any errors, or if you can offer a premiere date and location for a work where only the completion date or year is listed, please post a comment here.

2000
April 4Scenes from the Poet’s Dreams, for piano quintet, by Jennifer Higdon (1962-) was first performed in Philadelphia, Pennsylvania

April 27 – Symphony No. 8, “The Journey”, by Einojuhani Rautavaara (1929-2016) was first performed in Philadelphia, Pennsylvania

June 21 – Alan Hovhaness (1911-2000) died in Seattle, Washington

2001
April 19 – Orphée Suite [transcribed for piano by Paul Barnes (1961-)] by Philip Glass (1937-) was first performed in New York, New York

May 12 – Viola Sonata [Cello Sonata, op. 40, arranged for viola by Annette Bartholdy (1972-)] by Dmitri Shostakovich (1906-1975) received its world premiere recording

2002
July 2 – Jean-Yves Daniel-Lesur (1908-2002) died in Paris, France

September 22Light Refracted by Jennifer Higdon (1962-) was first performed in Philadelphia, Pennsylvania

2003
April 29Wild Swans, ballet by Elena Kats-Chernin (1957-) was first performed in Sydney, Australia

May 9Dreams of the Child of Light by Michael Mauldin (1947-) was first performed in Albuquerque, New Mexico

2004
Clytus Gottwald (1925-2023) completed Im Treibhaus (after Wagner), for unaccompanied chorus

July 21 – Jerry Goldsmith (1929-2004) died in Beverly Hills, California

November 12The Spirit and the Maiden, for violin, cello, and piano, by Elena Kats-Chernin (1957-) was first performed in Brisbane, Australia

2005
Valentin Silvestrov (1937-) completed Liturgical Chants, for SATB choir a cappella

January 21 – Kaljo Raid (1921-2005) died in Richmond Hill, Ontario, Canada

February 19 – Alma Deutscher (2005-) was born in Basingstoke, England

April 23 – Robert Farnon (1917-2005) died in Guernsey, Channel Islands

October – Symphony No. 1 (3rd and final version) by Einojuhani Rautavaara (1929-2016) was premiered via recording in Brussels, Belgium

December 17 – Trevor Duncan (1924-2005) died in Taunton, England

2006
Valentin Silvestrov (1937-) completed Two Christmas Lullabies, for SATB choir a cappella

Valentin Silvestrov (1937-) completed Two Sacred Songs, for SATB choir a cappella

Alla Pavlova (1952-) completed Symphony No. 5

Elisabetta Brusa (1954-) completed Merlin, Symphonic Poem

June 12 – György Ligeti (1923-2006) died in Vienna, Austria

September 23 – Malcolm Arnold (1921-2006) died in Norwich, England

2007
February 1 – Gian Carlo Menotti (1911-2007) died in Monte Carlo, Monaco

2009
April 10 – Richard Arnell (1917-2009) died in London, England

1990s

2010s

4534 Rimskij-Korsakov

On Sunday afternoon, October 13, 2024, I attended a wonderful concert by the Southern Arizona Symphony Orchestra (SASO) that included a rousing performance of Scheherazade by the Russian composer Nikolai Rimsky-Korsakov.

Early that evening, I was the first person in the world to observe the composer’s namesake asteroid 4534 Rimskij-Korsakov passing in front of a distant star and, briefly, blocking its light. As a classical music lover, that made me very happy.

The 0.5-second occultation of the 13.6-magnitude star UCAC4 558-003434 by the asteroid
4534 Rimskij-Korsakov on 14 Oct 2024 2:23:46 UT as seen from Tucson, Arizona
using an 8-inch telescope

4534 Rimskij-Korsakov was discovered on 6 Aug 1986 by the Russian astronomer Nikolai Chernykh (1931-2004) at the Crimean Astrophysical Observatory near the small settlement of Nauchnyi on the Crimean peninsula, part of Ukraine but illegally occupied by Putin’s Russian forces since 2014.

At the time of its discovery, this asteroid received its preliminary designation 1986 PV4. As is the custom, the discoverer gets to choose a name for the asteroid if they so desire, and Nikolai Chernykh decided to name his discovery after Nikolai Rimsky-Korsakov (1844-1908). This name was approved by the IAU and published in Minor Planet Circular 23352 on 25 Apr 1994.

4534 Rimskij-Korsakov is not a large asteroid. Its average diameter is estimated to be just 9.9 miles. Had I been right on the centerline of the asteroid’s shadow, I should have seen the star disappear for about 1.2 seconds. Given that I had to use an integration time of 0.27s due the faintness of the occulted star, the 0.5-second event I recorded had only two data points in the “dip” where the 13.6 magnitude star disappeared leaving only the sky background since the asteroid’s estimated magnitude was just 17.5m. Normally, one likes to have at least three data points in the dip, but two is better than one and the event happened at exactly the predicted time.

Nikolai Rimsky-Korsakov wrote a lot of great music, and he was a master of orchestration and orchestral “colors”. Here are my favorite works. If you don’t already know them, give them a listen!

  • Capriccio espagnol
  • Le Coq d’Or, Suite  [arranged by Alexander Glazunov (1865-1936) & Maximilian Steinberg (1883-1946)]
  • Russian Easter Festival Overture
  • Scheherazade
  • Suite from The Snow Maiden
  • Symphony No. 2, “Antar”
  • The Tale of Tsar Saltan, Suite

Classical Music Timeline: 1990s

This is one of a series of postings of important classical music dates, from the 17th century to the present. Included are the date and location of the birth and death of composers, and the premiere date and location of the first public performance of works. When the premiere date and location is unknown, the date or year of completion of the work is given. Though reasonably comprehensive, this is a subjective list, so the choice of composers and works is mine. If you find any errors, or if you can offer a premiere date and location for a work where only the completion date or year is listed, please post a comment here.

1990
Gloria Coates (1933-2023) completed Symphony No. 7

March 15 – Symphony No. 1 by John Corigliano (1938-) was first performed in Chicago, Illinois

October 14 – Leonard Bernstein (1918-1990) died in New York, New York

November 10Home Alone, with film score by John Williams (1932-), was released

December 2 – Aaron Copland (1900-1990) died in Sleepy Hollow, New York

1991
Ballade in G minor, op. 24 by Edvard Grieg (1843-1907) as orchestrated by Geirr Tveitt (1908-1981) was first performed in Norheimsund, Norway

John Adams (1947-) completed Berceuse élégiaque, an arrangement for small orchestra of the work by Ferruccio Busoni (1866-1924)

June 29Liverpool Oratorio by Paul McCartney (1942-) and Carl Davis (1936-2023) was first performed in Liverpool, England

1992
April 27 – Olivier Messiaen (1908-1992) died in Paris, France

1994
December 2Thurber’s Dogs by Peter Schickele (1935-2024) was first performed in Columbus, Ohio

1995
James Moody (1907-1995) died in London, England

Jack Stamp (1954-) completed Aubrey Fanfare

Timothy Brock (1963-) completed a film score for the 1926 silent movie Faust

May 31Lintukoto (Isle of Bliss) by Einojuhani Rautavaara (1929-2016) was first performed in Lohja, Finland

September 1 – Concerto for Saxophone Quartet and Orchestra by Philip Glass (1937-) was first performed in Stockholm, Sweden

1996
Thomas Bloch [aka Johann Julius Sontag von Holt Sombach] (1962-) completed Adagio for Glass Harmonica & String Quartet (from Fantaisie Concertante) sometime after this year

1997
Dominick Argento (1927-2019) completed Reverie, Reflections on a Hymn Tune

February 21Rosewood, with film score by John Williams (1932-), was released

1998
November 11 – Clive Richardson (1909-1998) died in London, England

1999
Lera Auerbach (1973-) completed Postlude for Violin and Piano

Lera Auerbach (1973-) completed Twenty-Four Preludes for Violin and Piano, op. 46

February 23 – Ruth Gipps (1921-1999) died in Eastbourne, England

July 6 – Joaquín Rodrigo (1901-1999) died in Madrid, Spain

1980s

2000s