Turnkey System for Occultations

Finally, a turnkey system is available for recording stellar occultations by asteroids and trans-Neptunian objects (TNOs)! All you need besides the kit is a telescope and a PC. A big thank you to Ted Blank and IOTA for putting this together!

Occultation Recording Kit

  • Highly sensitive RunCam Night Eagle Astro Edition video camera
  • 0.5x focal reducer & adapters to attach camera to 1¼-inch eyepiece holder
  • IOTA VTI (Video Time Inserter) V3
  • StarTech SVID2USB23 USB video capture device
  • Instruction manual
  • Cost: $518

http://occultations.org/observing/recommended-equipment/iota-vti/

We need more observers in the Midwest (everywhere, really) to give us more chords across the asteroids and TNOs, thus increasing the scientific value of the observations. Right now, we are desperately in need of observers in Iowa (where I lived for many years and will always be home to me), and we have precious few active observers in Wisconsin (yours truly), Minnesota (Steve Messner), and Illinois (Bob Dunford, Aart Olsen, Randy Trank).

If you have an interest in pursuing this interesting and rewarding speciality that gives you the opportunity to make a valuable scientific contribution, feel free to post a comment here and I’ll be happy to help!

Lost in Math: A Book Review

I recently finished reading a thought-provoking book by theoretical physicist Sabine Hossenfelder, Lost in Math: How Beauty Leads Physics Astray. Hossenfelder writes in an engaging and accessible style, and I hope you will enjoy reading this book as much as I did. Do we have a crisis in physics and cosmology? You be the judge. She presents convincing arguments.

The basic premise of Hossenfelder’s book is that when theoretical physicists and cosmologists lack empirical data to validate their theories, they have to rely on other approaches—”beauty”, “symmetry”, “simplicity”, “naturalness“, “elegance”—mathematics. Just because these approaches have been remarkably successful in the past is no guarantee they will lead to further progress.

One structural element that contributes to the book’s appeal is Hossenfelder’s interviews with prominent theoretical physicists and cosmologists: Gian Francesco Giudice, Michael Krämer, Gordon Kane, Keith Olive, Nima Arkani-Hamed, Steven Weinberg, Chad Orzel, Frank Wilczek, Garrett Lisi, Joseph Polchinski, Xiao-Gang Wen, Katie Mack, George Ellis, and Doyne Farmer. And, throughout the book, she quotes many other physicists, past and present, as well. This is a well-researched book by an expert in the field.

I also like her “In Brief” summaries of key points at the end of each chapter. And her occasional self-deprecating, brief, soliloquies, which I find reassuring. This book is never about the care and feeding of the author’s ego, but rather giving voice to largely unspoken fears that theoretical physics is stagnating. And an academic environment hell-bent on preserving the status quo isn’t helping matters, either.

Anthropic Principle

Do we live in a universe fine-tuned for life? If so, is it the only possible universe that would support life? Recent work indicates that there may be more than one set of parameters that could lead to a life-supporting universe.

Beauty is in the Eye of the Beholder

Is our sense of what is “beautiful” a reliable guide to gaining a deeper understanding of nature? Or does it sometimes lead us astray? We know from history that it does.

In the past, symmetries have been very useful. Past and present, they are considered beautiful

When we don’t have data to guide our theory development, aesthetic criteria are used. Caveat emptor.

Experiment and Theory

Traditionally, experiment and observation have driven theory. Now, increasingly, theory drives experiment, and the experiments are getting more difficult, more expensive, and more time consuming to do—if they can be done at all.

Inflation

The rapid expansion of the universe at the time of the Big Bang is known as cosmic inflation, or, simply, inflation. Though there is some evidence to support inflation, that evidence is not yet compelling.

Mathematics

Mathematics creates a logically consistent universe all its own. Some of it can actually be used to describe our physical universe. What math is the right math?

Math is very useful for describing nature, but is math itself “real”, or is it just a useful tool? This is an ancient question.

Memorable Quotations

“I went into physics because I don’t understand human behavior.” (p. 2)

“If a thousand people read a book, they read a thousand different books. But if a thousand people read an equation, they read the same equation.” (p. 9)

“In our search for new ideas, beauty plays many roles. It’s a guide, a reward, a motivation. It is also a systematic bias.” (p. 10)

On artificial intelligence: “Being unintuitive shouldn’t be held against a theory. Like lack of aesthetic appeal, it is a hurdle to progress. Maybe this one isn’t a hurdle we can overcome. Maybe we’re stuck in the foundations of physics because we’ve reached the limits of what humans can comprehend. Maybe it’s time to pass the torch.” (p. 132)

“The current organization of academia encourages scientists to join already dominant research programs and discourages any critique of one’s own research area.” (p. 170)

Multiverse

The idea that our universe of just one of a great many universes is presently the most controversial idea in physics.

Particles and Interactions

What is truly interesting is not the particles themselves, but the interactions between particles.

Philosophy

Physicists and astrophysicists are sloppy philosophers and could stand to benefit from a better understanding of the philosophical assumptions and implications of their work.

Physics isn’t Math

Sure, physics contains a lot of math, but that math has traditionally been well-grounded in observational science. Is math driving physics more than experiment and observation today?

Quantum Mechanics

Nobody really understands quantum mechanics. Everybody’s amazed but no one is happy. It works splendidly well. The quantum world is weird. Waves and particles don’t really exist, but everything (perhaps even the universe itself) is describable by a probabilistic “wave function” that has properties of both and yet is neither. Then there’s the many-worlds interpretation of quantum mechanics, and quantum entanglement

Science and the Scientific Method

In areas of physics where experiments are too difficult, expensive, or impossible to do, some physicists seem to be abandoning the scientific method as the central pillar of scientific inquiry. Faith in beauty, faith in mathematics, faith in naturalness, faith in symmetry. How is this any different than religion?

If scientists can evaluate a theory using other criteria than that theory’s ability to describe observation, how is that science?

Stagnation

Some areas of physics haven’t seen any new data for decades. In such an environment, theories can and do run amok.

Standard Model (of particle physics)

Ugly, contrived, ad hoc, baroque, overly flexible, unfinished, too many unexplained parameters. These are some of the words used to describe the standard model of particle physics. And, yet, the standard model describes the elementary particles we see in nature and their interactions with extraordinary exactitude.

String Theory

String theory dates back at least to the 1970s, and its origins go back to the 1940s. To date, there is still no experimental evidence to support it. String theory is not able to predict basic features of the standard model. That’s a problem.

Triple Threat: Crises in Physics, Astrophysics, and Cosmology?

Physics: Sure, the Large Hadron Collider (LHC) at CERN gave us the Higgs boson, but little else. No new physics. No supersymmetry particles. Embarrassments like the diphoton anomaly. Do we need a bigger collider? Perhaps. Do we need new ideas? Likely.

Astrophysics: We’ve spent decades trying to understand what dark matter is, to no avail. No dark matter particles have been found.

Cosmology: We have no testable idea as to what dark energy is. Plenty of theories, though.


See Hossenfelder’s recent comments on the LHC and dark matter in her op-ed, “The Uncertain Future of Particle Physics” in the January 23, 2019 issue of The New York Times.


The book concludes with three appendices:

  • Appendix A: The Standard Model Particles
  • Appendix B: The Trouble with Naturalness
  • Appendix C: What You Can Do To Help

Hossenfelder gives some excellent practical advice in Appendix C. This appendix is divided into three sections of action items:

  • As a scientist
  • As a higher ed administrator, science policy maker, journal editor, or representative of a funding body
  • As a science writer or member of the public

I’m really glad she wrote this book. As an insider, it takes courage to criticize the status quo.

References
Hossenfelder, S., Lost in Math: How Beauty Leads Physics Astray, Basic Books, New York (2018).
Hossenfelder, Sabine. “The Uncertain Future of Particle Physics.” The New York Times 23 Jan 2019. https://www.nytimes.com/2019/01/23/opinion/particle-physics-large-hadron-collider.html.

Zodiacal Light 2019

In this year of 2019, the best dates and times for observing the zodiacal light are listed below. The sky must be very clear with little or no light pollution. The specific times listed are for Dodgeville, Wisconsin.

2019BeginEndDirection
Tue. Jan. 226:39 p.m.7:03 p.m.West
Wed. Jan. 236:40 p.m.7:40 p.m.West
Thu. Jan. 246:41 p.m.7:41 p.m.West
Fri. Jan. 256:42 p.m.7:42 p.m.West
Sat. Jan. 266:43 p.m.7:43 p.m.West
Sun. Jan. 276:44 p.m.7:44 p.m.West
Mon. Jan. 286:45 p.m.7:45 p.m.West
Tue. Jan. 296:46 p.m.7:46 p.m.West
Wed. Jan. 306:48 p.m.7:48 p.m.West
Thu. Jan. 316:49 p.m.7:49 p.m.West
Fri. Feb. 16:50 p.m.7:50 p.m.West
Sat. Feb. 26:51 p.m.7:51 p.m.West
Sun. Feb. 36:52 p.m.7:52 p.m.West
Mon. Feb. 46:53 p.m.7:53 p.m.West
Tue. Feb. 56:55 p.m.7:55 p.m.West
Wed. Feb. 67:09 p.m.7:56 p.m.West
Thu. Feb. 217:14 p.m.8:14 p.m.West
Fri. Feb. 227:15 p.m.8:15 p.m.West
Sat. Feb. 237:16 p.m.8:16 p.m.West
Sun. Feb. 247:17 p.m.8:17 p.m.West
Mon. Feb. 257:19 p.m.8:19 p.m.West
Tue. Feb. 267:20 p.m.8:20 p.m.West
Wed. Feb. 277:21 p.m.8:21 p.m.West
Thu. Feb. 287:22 p.m.8:22 p.m.West
Fri. Mar. 17:23 p.m.8:23 p.m.West
Sat. Mar. 27:25 p.m.8:25 p.m.West
Sun. Mar. 37:26 p.m.8:26 p.m.West
Mon. Mar. 47:27 p.m.8:27 p.m.West
Tue. Mar. 57:28 p.m.8:28 p.m.West
Wed. Mar. 67:30 p.m.8:30 p.m.West
Thu. Mar. 77:31 p.m.8:31 p.m.West
Fri. Mar. 88:01 p.m.8:32 p.m.West
Fri. Mar. 228:50 p.m.9:24 p.m.West
Sat. Mar. 238:52 p.m.9:52 p.m.West
Sun. Mar. 248:53 p.m.9:53 p.m.West
Mon. Mar. 258:54 p.m.9:54 p.m.West
Tue. Mar. 268:56 p.m.9:56 p.m.West
Wed. Mar. 278:57 p.m.9:57 p.m.West
Thu. Mar. 288:59 p.m.9:59 p.m.West
Fri. Mar. 299:00 p.m.10:00 p.m.West
Sat. Mar. 309:01 p.m.10:01 p.m.West
Sun. Mar. 319:03 p.m.10:03 p.m.West
Mon. Apr. 19:04 p.m.10:04 p.m.West
Tue. Apr. 29:06 p.m.10:06 p.m.West
Wed. Apr. 39:07 p.m.10:07 p.m.West
Thu. Apr. 49:09 p.m.10:09 p.m.West
Fri. Apr. 59:10 p.m.10:10 p.m.West
Sat. Apr. 69:12 p.m.10:12 p.m.West
Sun. Apr. 710:03 p.m.10:13 p.m.West
Thu. Aug. 293:39 a.m.4:39 a.m.East
Fri. Aug. 303:40 a.m.4:40 a.m.East
Sat. Aug. 313:42 a.m.4:42 a.m.East
Sun. Sep. 13:43 a.m.4:43 a.m.East
Mon. Sep. 23:45 a.m.4:45 a.m.East
Tue. Sep. 33:46 a.m.4:46 a.m.East
Wed. Sep. 43:48 a.m.4:48 a.m.East
Thu. Sep. 53:49 a.m.4:49 a.m.East
Fri. Sep. 63:50 a.m.4:50 a.m.East
Sat. Sep. 73:52 a.m.4:52 a.m.East
Sun. Sep. 83:53 a.m.4:53 a.m.East
Mon. Sep. 93:55 a.m.4:55 a.m.East
Tue. Sep. 103:56 a.m.4:56 a.m.East
Wed. Sep. 113:57 a.m.4:57 a.m.East
Thu. Sep. 124:52 a.m.4:59 a.m.East
Fri. Sep. 275:11 a.m.5:18 a.m.East
Sat. Sep. 284:19 a.m.5:19 a.m.East
Sun. Sep. 294:20 a.m.5:20 a.m.East
Mon. Sep. 304:21 a.m.5:21 a.m.East
Tue. Oct. 14:23 a.m.5:23 a.m.East
Wed. Oct. 24:24 a.m.5:24 a.m.East
Thu. Oct. 34:25 a.m.5:25 a.m.East
Fri. Oct. 44:26 a.m.5:26 a.m.East
Sat. Oct. 54:27 a.m.5:27 a.m.East
Sun. Oct. 64:29 a.m.5:29 a.m.East
Mon. Oct. 74:30 a.m.5:30 a.m.East
Tue. Oct. 84:31 a.m.5:31 a.m.East
Wed. Oct. 94:32 a.m.5:32 a.m.East
Thu. Oct. 104:33 a.m.5:33 a.m.East
Fri. Oct. 114:43 a.m.5:34 a.m.East
Sat. Oct. 264:51 a.m.5:19 a.m.East
Sun. Oct. 274:53 a.m.5:53 a.m.East
Mon. Oct. 284:54 a.m.5:54 a.m.East
Tue. Oct. 294:55 a.m.5:55 a.m.East
Wed. Oct. 304:56 a.m.5:56 a.m.East
Thu. Oct. 314:57 a.m.5:57 a.m.East
Fri. Nov. 14:58 a.m.5:58 a.m.East
Sat. Nov. 24:59 a.m.5:59 a.m.East
Sun. Nov. 34:01 a.m.5:01 a.m.East
Mon. Nov. 44:02 a.m.5:02 a.m.East
Tue. Nov. 54:03 a.m.5:03 a.m.East
Wed. Nov. 64:04 a.m.5:04 a.m.East
Thu. Nov. 74:05 a.m.5:05 a.m.East
Fri. Nov. 84:06 a.m.5:06 a.m.East
Sat. Nov. 94:07 a.m.5:07 a.m.East
Sun. Nov. 104:34 a.m.5:08 a.m.East
Sun. Nov. 244:23 a.m.4:27 a.m.East
Mon. Nov. 254:24 a.m.5:24 a.m.East
Tue. Nov. 264:25 a.m.5:25 a.m.East
Wed. Nov. 274:26 a.m.5:26 a.m.East
Thu. Nov. 284:27 a.m.5:27 a.m.East
Fri. Nov. 294:28 a.m.5:28 a.m.East
Sat. Nov. 304:29 a.m.5:29 a.m.East
Sun. Dec. 14:30 a.m.5:30 a.m.East
Mon. Dec. 24:31 a.m.5:31 a.m.East
Tue. Dec. 34:32 a.m.5:32 a.m.East
Wed. Dec. 44:33 a.m.5:33 a.m.East
Thu. Dec. 54:34 a.m.5:34 a.m.East
Fri. Dec. 64:35 a.m.5:35 a.m.East
Sat. Dec. 74:35 a.m.5:35 a.m.East
Sun. Dec. 84:36 a.m.5:36 a.m.East
Mon. Dec. 94:37 a.m.5:37 a.m.East
Tue. Dec. 105:29 a.m.5:38 a.m.East

The best nights to observe the zodiacal light at mid-northern latitudes occur when the ecliptic plane intersects the horizon at an angle of 60° or steeper. The dates above were chosen on that basis, with the Sun at least 18° below the horizon and the Moon below the horizon being used to calculate the times. An interval of time of one hour either before morning twilight or after evening twilight was chosen arbitrarily because it is the “best one hour” for observing the zodiacal light. The zodiacal light cone will be brightest and will reach highest above the horizon when the Sun is 18° below the horizon (astronomical twilight), but no less.

If you are interested in calculating the angle the ecliptic makes with your horizon for any date and time, you can use the following formula:

\cos I = \cos \varepsilon \sin \phi-\sin \varepsilon \cos \phi \sin \theta

where I is the angle between the ecliptic and the horizon, ε is  the obliquity of the ecliptic, φ is the latitude of the observer, and θ is the local sidereal time (the right ascension of objects on the observer's meridian at the time of observation).

Here’s a SAS program I wrote to do these calculations:

References
Meeus, J. Astronomical Algorithms. 2nd ed., Willmann-Bell, 1998, p. 99.

Total Lunar Eclipse 2019

We’ll be treated to a front-row seat for the total lunar eclipse this coming Sunday night and Monday morning, January 20/21, 2019! Here are the local circumstances for Dodgeville, Wisconsin.

Time (CST)EventAltitude
8:36:29 p.m.Penumbral Eclipse Begins40°
9:10 p.m.Penumbra first visible?46°
9:33:55 p.m.Partial Eclipse Begins50°
10:41:19 p.m.Total Eclipse Begins60°
11:12:18 p.m.Greatest Eclipse64°
11:43:18 p.m.Total Eclipse Ends66°
12:14:31 a.m.Moon crosses the celestial meridian67°
12:50:42 a.m.Partial Eclipse Ends66°
1:15 a.m.Penumbra last visible?64°
1:48:06 a.m.Penumbral Eclipse Ends60°

This is the first total lunar eclipse visible in its entirety from SW Wisconsin since September 28, 2015; the next such event won’t occur again until May 16, 2022. You’ll note in the table above, the Moon will be 64° above the horizon at mid-totality. The Moon has not been this high in our sky at mid-totality since November, 29, 1993 (66°), and it will not be this high again at mid-totality until January 21, 2048 (67°).

The first hint of shading will occur on the left (eastward-facing) edge of the Moon around 9:10 p.m. The first sliver of the full Moon enters the umbral shadow of the Earth at 9:33 p.m., so you’ll want to be watching by then. The entire Moon will be immersed in the umbral shadow of the Earth 67 minutes later at 10:41 p.m. This means that if you were anywhere on the nearside of the Moon you would see the dark Earth (except for city lights) completely covering the Sun, with a spectacular “ring of fire” all the way round the limb of the Earth refracting orangish-red light through our atmosphere—the combined light of all the world’s sunrises and sunsets at that moment.

This, of course, will continue as the Moon penetrates deeper into the umbral shadow of the Earth, reaching its closest to the center of the Earth’s shadow at mid-eclipse at 11:12 p.m.

The best place in the world to view this total lunar eclipse (assuming it is clear) will be Guantánamo Province in Cuba. Just 8 miles north of the municipality of El Salvador, Cuba, the Moon will be directly overhead at mid-eclipse.

There has been an unfortunate tendency of the mainstream media in recent years to use the term “Blood Moon” to describe a total lunar eclipse. Why must we use imagery so often associated with violence, death, and destruction in our discourse? The color of a total lunar eclipse depends upon the condition and transparency of the Earth’s atmosphere during the eclipse, and it can range from orange to coppery to red, and rarely even gray or brownish, so why not say orangish-red and leave it at that?

Direct Imaging of Exoplanets Through Occultations

Planetary orbits are randomly oriented throughout our galaxy. The probability that an exoplanet’s orbit will be fortuitously aligned to allow that exoplanet to transit across the face of its parent star depends upon the radius of the star, the radius of the planet, and the distance of the planet from the star. In general, planets orbiting close-in are more likely to be seen transiting their star then planets orbiting further out.

The equation for the probability of observing a exoplanet transit event is

p_{tra} = \left (\frac{R_{\bigstar}+R_{p}}{a} \right )\left (\frac{1}{1-e^{2}} \right )

where ptra is the transit probability, R* is the radius of the star, Rp is the radius of the planet, a is the semi-major axis of the planetary orbit, and e is the eccentricity of the planetary orbit 

Utilizing the data in the NASA Exoplanet Archive for the 1,463 confirmed exoplanets where the above data is available (and assuming e = 0 when eccentricity is unavailable), we find that the median exoplanet transit probability is 0.0542. This means that, on average, 1 out of every 18 planetary systems will be favorably aligned to allow us to observe transits. However, keep in mind that our present sample of exoplanets is heavily biased towards large exoplanets orbiting close to their parent star. Considering a hypothetical sample of Earth-sized planets orbiting 1 AU from a Sun-sized star, the transit probability drops to 0.00469, which means that we would be able to detect only about 1 out of every 213 Earth-Sun analogs using the transit method.

How might we detect some of the other 99.5%? My admired colleague in England, Abdul Ahad, has written a paper about his intriguing idea: “Detecting Habitable Exoplanets During Asteroidal Occultations”. Abdul’s idea in a nutshell is to image the immediate environment around nearby stars while they are being occulted by asteroids or trans-Neptunian objects (TNOs) in order to detect planets orbiting around them. While there are many challenges (infrequency of observable events, narrow shadow path on the Earth’s surface, necessarily short exposure times, and extremely faint planetary magnitudes), I believe that his idea has merit and will one day soon be used to discover and characterize exoplanets orbiting nearby stars.

Ahad notes that the apparent visual magnitude of any given exoplanet will be directly proportional to the apparent visual magnitude of its parent star, since exoplanets shine by reflected light. Not only that, Earth-sized and Earth-like planets orbiting in the habitable zone of any star would shine by reflected light of the same intrinsic brightness, regardless of the brightness of the parent star. He also notes that the nearer the star is to us, the greater will be a given exoplanet’s angular distance from the occulted star. Thus, given both of these considerations (bright parent star + nearby parent star = increased likelihood of detection), nearby bright stars such as Alpha Centauri A & B, Sirius A, Procyon A, Altair, Vega, and Fomalhaut offer the best chance of exoplanet detection using this technique.

Since an exoplanet will be easiest to detect when it is at its greatest angular distance from its parent star, we will be seeing only about 50% of its total reflected light. An Earth analog orbiting Alpha Centauri A would thus shine at visual magnitude +23.7 at 0.94″ angular distance, and for Alpha Centauri B the values would be +24.9 and 0.55″.

Other considerations include the advantage of an extremely faint occulting solar system object (making it easier to detect faint exoplanets during the occultation event), and the signal boost offered by observing in the infrared, since exoplanets will be brightest at these wavelengths.

A distant (and therefore slow-moving) TNO would be ideal, but the angular size of the TNO needs to be larger than the angular size of the occulted star. However, slow-moving objects mean that occultation events will be rare.

The best chance of making this a usable technique for exoplanet discovery would be a space-based observatory that could be positioned at the center of the predicted shadow and would be able to move along with the shadow to increase exposure times (Ahad, personal communication). It would be an interesting challenge in orbital mechanics to design the optimal base orbit for such a spacecraft. The spacecraft orbit would be adjusted to match the position and velocity of the occultation shadow for each event using an ion drive or some other electric propulsion system.

One final thought on the imaging necessary to detect exoplanets using this technique. With a traditional CCD you would need to begin and end the exoplanet imaging exposure(s) only while the parent star is being occulted. This would not be easy to do, and would require two telescopes – one for the occultation event detection and one for the exoplanet imaging. A better approach would be to use a Geiger-mode avalanche photodiode (APD). Here’s a description of the device captured in 2016 on the MIT Lincoln Labs Advanced Imager Technology website:

A Geiger-mode avalanche photodiode (APD), on the other hand, can be used to build an all-digital pixel in which the arrival of each photon triggers a discrete electrical pulse. The photons are counted digitally within the pixel circuit, and the readout process is therefore noise-free. At low light levels, there is still noise in the image because photons arrive at random times so that the number of photon detection events during an exposure time has statistical variation. This noise is known as shot noise. One advantage of a pixel that can digitally count photons is that if shot noise is the only noise source, the image quality will be the best allowed by the laws of physics. Another advantage of an array of photon counting pixels is that, because of its noiseless readout, there is no penalty associated with reading the imager out frequently. If one reads out a thousand 1-ms exposures of a static scene and digitally adds them, one gets the same image quality as a single 1-s exposure. This would not be the case with a conventional imager that adds noise each time it is read out.

References
Ahad, A., “Detecting Habitable Exoplanets During Asteroidal Occultations”, International Journal of Scientific and Innovative Mathematical Research, Vol. 6(9), 25-30 (2018).
MIT Lincoln Labs, Advanced Imager Technology, https://www.ll.mit.edu/mission/electronics/ait/single-photon-sensitive-imagers/passive-photon-counting.html. Retrieved March 17, 2016.
NASA Exoplanet Archive https://exoplanetarchive.ipac.caltech.edu.
Winn, J.N., “Exoplanet Transits and Occultations,” in Exoplanets, ed. Seager, S., University of Arizona Press, Tucson (2011).

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:

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
       

Comet 46P/Wirtanen

Comet 46P/Wirtanen, 15 Dec 2018 6:54:21 – 6:59:21 UT, Dodgeville, WI (Photo by David Oesper)

Carl A. Wirtenen (1910-1990) was born in Kenosha, Wisconsin and nearly 71 years ago he discovered a comet on a photographic plate while doing a stellar proper motion survey at the Lick Observatory in California.

Comet 46P/Wirtanen orbits the Sun once every 5.44 years at a distance ranging from 1.06 AU at perihelion to 5.13 AU at aphelion.

Carl Wirtanen discovered five comets, but 46P/Wirtanen is the only one that is not a long-period comet. The others are C/1947 O1, C/1948 N1, C/1948 T1, and C/1956 F1-A.

Comet 46P/Wirtanen reached perihelion on Wednesday, December 12 at 4:38 p.m. CST, and made its closest approach to the Earth since its discovery (7.2 million miles) on Sunday, December 16 at 7:05 a.m. CST. It will not pass this close to Earth again until sometime after the year 2197.

The photo above was taken just 30 hours before Comet 46P/ Wirtanen made its closest approach to Earth. I used a digital SLR camera with 300mm telephoto lens piggybacked on the telescope I use for asteroid occultations. I was able to manually guide on the comet’s nucleus which was easily visible as a “fuzzy” star using a sensitive video camera imaging through the telescope. Comet 46P/Wirtanen’s nucleus is estimated to have diameter of just 3,900 ft., and it rotates once every 8.9 hours.

In the three-image sequence below you can definitely see the comet’s motion relative to the background stars.

Comet 46P/Wirtanen, 15 Dec 2018 6:38:17-6:41:18, 6:45:23 – 6:49:24, and 6:54:21 – 6:59:21 UT

How do you pronounce “Wirtanen”? See here.

NASA News Releases

I receive dozens of emails each day, and chances are you do, too.  But one email list I think you should seriously consider subscribing to is the NASA News Releases.  There have been 115 news releases and 185 media advisories issued so far this year, so that averages to about one email a day.  The quality of these news releases is consistently high—they are far better written and information rich than most of what clutters up our inboxes or what you’ll find on a typical internet news site.

Take, for example, the two news releases that were issued on December 10:

RELEASE 18-114
NASA’s Newly Arrived OSIRIS-REx Spacecraft Already Discovers Water on Asteroid

RELEASE 18-115
NASA’s Voyager 2 Probe Enters Interstellar Space

Subscribing is easy:

NASA news releases and other information are available automatically by sending an e-mail message with the subject line subscribe to hqnews-request@newsletters.nasa.gov. 
To unsubscribe from the list, send an e-mail message with the subject line unsubscribe to hqnews-request@newsletters.nasa.gov.

Exoplanets with Deep Transits

The list above shows the 35 stars presently known to dip in brightness by 0.02 magnitudes or more due to a transiting exoplanet.

The change in the star’s magnitude during transit is given by

\Delta m = 2.5\log_{10}\left ( 1+\delta \right )

where Δm is the drop in magnitude, and δ is the transit depth

The time between transits for these exoplanets ranges between 0.79 and 5.72 days, with a median period of 2.24 days.  You can generate your own ephemeris for any of these transiting exoplanets at:

https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TransitView/nph-visibletbls?dataset=transits

The transit duration for these exoplanets ranges between 1.08 and 3.11 hours, with a median duration of 2.11 hours.

The exoplanets with the deepest transits, HATS-6 b at 0.035 magnitudes and Kepler-45 b at 0.034 magnitudes, cross stars that are 15.2 and 16.9 magnitude, respectively, so these events might be out of reach for most amateur photometrists.  The only other star hosting a transiting exoplanet with a Δm ≥ 0.03m is Tycho 5165-481-1 in Aquila (WASP-80 b) which at visual magnitude 11.9 is a better candidate for smaller instruments.  The brightest star on our list (by far) is HD 189733 in Vulpecula, magnitude 7.7, with a drop in brightness that is almost as good at 0.026 magnitudes.

References
Fakhouri, O. (2018). Exoplanet Orbit Database | Exoplanet Data Explorer. [online] Exoplanets.org. Available at: http://exoplanets.org/ [Accessed 11 Dec. 2018].