Keith Bechtol at UW Space Place

We are so very fortunate here in southern Wisconsin to have evening public lectures the 2nd Tuesday every month of the year at the University of Wisconsin Space Place, expertly organized by Jim Lattis. On Tuesday, November 12th, Clif Cavanaugh (retired physics and astronomy professor at the UW in Richland Center) and I made the trek (as we often do) from Spring Green-Dodgeville to the Space Place in Madison. This month, we were treated to an excellent presentation by Keith Bechtol, an Observational Cosmologist in the Physics Department at UW-Madison. His topic was The Big Picture: Science with Astronomical Surveys. Keith is an early career scientist with a bright future. His presentation was outstanding.

I’d like to share with you some of the highlights.

Before the talk, which is mostly about the Large Synoptic Survey Telescope (LSST), currently under construction in Chile and expected to see first light in 2020, I asked Keith about whether LSST would be renamed the Vera Rubin Telescope as was announced at AAS 234 in St. Louis this past summer. As it turns out, Keith has been a vocal advocate for naming LSST after Vera Rubin, though no final decision has yet been made.

Before I get into notes from the talk, I wanted to share with you the definition of the word synoptic in case you are not familiar with that word. The Oxford English Dictionary defines the word synoptic as “furnishing a general view of some subject; spec. depicting or dealing with weather conditions over a large area at the same point in time.” But rather than the traditional meteorological definition, here we are referring to a wide-field survey of the entire night sky visible from Cerro Pachón in Chile, latitude 30˚ S.

Keith first talked about how astronomical imaging is currently advancing along two fronts. The first is high-resolution imaging, as recently illustrated with first image of the event horizon of a black hole from the Event Horizon Telescope, where an amazing resolution of around 25 microarcseconds was achieved.

In general, the larger the telescope aperture, the smaller the field of view.

The Hubble Space Telescope’s Ultra Deep Field is only 3.1 arcminutes square

A survey telescope, on the other hand, must be designed to cover a much larger area of the sky for each image.

Not only can a survey telescope detect “anything that changes” in the night sky, but it also allows us to probe the large-scale structure of our universe. Three still-mysterious entities that are known to affect this large-scale structure are dark energy, dark matter, and neutrinos. Keith indicates that “these names are placeholders for physics we don’t yet fully understand.”

Dark energy, which is responsible for driving galaxies apart at an accelerating rate, is unusual in that it maintains a constant density as the universe expands. And its density is very low.

Supernovae are a very useful tool to probe the dark-energy-induced accelerating expansion of the universe, but in any particular galaxy they are exceedingly rare, so by monitoring large areas of the sky (ideally, the entire sky), we can discover supernovae frequently.

The mass distribution of our universe subtly affects the alignment and shapes of distant galaxies through a phenomenon known as weak gravitational lensing. Understanding these distortions and correlations requires a statistical approach looking at many galaxies across large swaths of sky.

Closer to home, small galaxies that have come too close our Milky Way galaxy are pulled apart into stellar streams that require a “big picture” approach to discover and map. The dark matter distribution in our Milky Way galaxy plays an important role in shaping these stellar streams—our galaxy contains about ten times as much dark matter as normal matter.

With wide-field surveys, not only do we need to cover large areas of sky, but we also want to be able to see the faintest and most distant objects. That latter property is referred to as “going deeper”.

The LSST will provide a dramatic increase in light gathering power over previous survey instruments. The total number of photons collected by a survey instrument per unit time is known as the étendue, a French word, and it is the field of view (in square degrees) × the effective aperture (in m2) × the quantum efficiency (unitless fraction). The units of étendue are thus m2deg2. Note that the vertical axis in the graph below is logarithmic, so the LSST will have a significantly higher étendue than previous survey instruments.

The largest monolithic mirrors in the world are fabricated at the Steward Observatory Mirror Lab at the University of Arizona in Tucson. The largest mirrors that can be produced there are 8.4 meters, and LSST has one of them.

Remember the Yerkes Observatory 40-inch refractor, completed in 1897? It has held the record as the largest lens ever used in an astronomical telescope. Until now. A 61.8-inch lens (L-1) and a 47.2-inch (L-2) have been fabricated for use in the LSST camera.

L-1, the largest lens ever produced, is the front lens of the LSST camera

LSST will utilize a camera that is about the size of a car. It is the largest camera ever built for astronomy.

The LSST camera will produce 3.2 gigapixel images. You would need to cover about half a basketball court with 4K TV screens to display the image at full resolution.

An image will be produced every 15 seconds throughout the night, every clear night, and each patch of sky will be reimaged every three nights. That is a HUGE amount of data! ~10 Tb of data each night. Fiber optical cable will transport the data from Cerro Pachón to the National Center for Supercomputing Applications in Urbana, Illinois, where it will be prepared for immediate use and made publicly available to any interested researcher. The amount of data is so large that no one will be downloading raw data to their local computer. They will instead be logging in to the supercomputer and all processing of the data will be done there, using open source software packages.

There are many data processing challenges with LSST data needing to be solved. Airplane, satellite, and meteor trails will need to be carefully removed. Many images will be so densely packed with overlapping objects that special care will be needed separating the various objects.

One LSST slide that Keith presented showed “Solar System Objects: ~ 6 million” and that piqued my interest, given my ongoing research program of observing stellar occultations by asteroids and trans-Neptunian objects for IOTA. Currently, if you endeavor to observe the highest probability occultation events from a fixed observatory location each night, you will be lucky to record one positive event for every ten negative events (no occultation). The reason for this is that our knowledge of the orbital elements of the small bodies of the solar system is not yet precise enough to accurately predict where stellar occultation events will occur. Gaia DR3, scheduled for the latter half of 2021, should significantly improve the precision of small body orbits, and even though LSST does not have nearly the astrometric precision of Gaia, it will provide many valuable astrometric data points over time that can be used to refine orbital elements. Moreover, it is expected that LSST will discover—with its much larger aperture than Gaia—at least 10 times the number of asteroids and trans-Neptunian objects that are currently known.

During the question and answer period after the lecture, I asked Keith what effect the gigantic increase in the number of satellites in Earth orbit will have on LSST operations (global broadband internet services provided by organizations like SpaceX with its Starlink constellation). He stated that this definitely presents a data processing challenge that they are still working on.

An earlier version of Keith’s presentation can be found here. All images in this article except the first (OED) come from Keith’s presentation and have not been altered in any way.

References

Bechtol, Keith, “The Big Picture: Science with Astronomical Surveys” (lecture, University of Wisconsin Space Place, Madison, November 12, 2019).

Bechtol, Ellen & Keith, “The Big Picture: Science and Public Outreach with Astronomical Surveys” (lecture, Wednesday Night at the Lab, University of Wisconsin, Madison, April 17, 2019; University Place, Corporation for Public Broadcasting, PBS Wisconsin).

Jones, R. L., Jurić, M., & Ivezić, Ž. 2016, in IAU Symposium, Vol. 318, Asteroids: New Observations, New Models, ed. S. R. Chesley, A. Morbidelli, R. Jedicke, & D. Farnocchia, 282–292. https://arxiv.org/abs/1511.03199 .

Oxford English Dictionary Online, accessed November 17, 2019, https://www.oed.com/ .

Remembering Comet Holmes

Twelve years ago today, Comet Holmes (17P) brightened from magnitude 16.5 to 2.6, forming a right triangle with Mirfak (α Persei) and δ Persei, opposite to Algol. Here is what I wrote in The Sky This Week at that time.


TSTW 10/25/07

Comet Holmes Bursts on the Scene!

Who ever said astronomy isn’t exciting? Sure, much of what we observe in the cosmos seems predictable and unchanging—but then something unexpected happens and we are scrambling to get a front-row seat and our lives are thrown into an exhilarating tizzy for a few hours or days. Whether it be an unexpected auroral display, a meteor fireball, a nova, supernova, or comet, the result is the same: it is exciting to be an astronomer, to be attuned to a universe that existed long before we were born and that will be here long after we are gone. That, to me, is comforting.

Very early Wednesday, October 24, a 16th-magnitude short-period comet presently in Perseus by the name of Holmes brightened about 14 magnitudes from 16.5 to 2.6 in little more than 12 hours: a brightness increase of 363,000 times! While such a cometary outburst was unexpected, it is not unprecedented. From time to time, solar heating (greatest when a comet is near perihelion) must cause pressure to build up inside a comet as subsurface ices volatilize. Eventually, the pressure builds up until it explodes through the surface of the comet, spewing gas and dust into space and exposing fresh material to solar radiation. Sometimes, this process is so violent that the comet breaks into multiple fragments.

Comet Holmes (17P) is one of the so-called “short period” comets, meaning it orbits the Sun in less than 200 years or has been observed at more than one perihelion passage. Comet Holmes orbits the Sun every 6.9 years, ranging from just inside the main part of the asteroid belt (2.1 AU) to the orbit of Jupiter (5.2 AU). No doubt Comet Holmes’ original orbit has been substantially altered by the gravitational influence of Jupiter. Comet Holmes is presently 2.5 AU from the Sun (230 million miles) and 1.6 AU from the Earth (150 million miles), having just passed perihelion on May 4, 2007.

Comet Holmes was discovered during its last outburst, which occurred on November 6, 1892 by English amateur astronomer Edwin Holmes (1839-1919). It was observed again in 1906, but was then lost until being recovered in 1964. It has since been observed near perihelion at every return.

The recent outburst of Comet Holmes may be one for the record books. I am not aware of any other comet outburst being recorded where the comet brightened by as much as 14 magnitudes in less than a day! Fortunately, the first two nights after the outburst the sky was beautifully clear here. The first night, October 24, Comet Holmes looked like a star to the unaided eye. In binoculars, it looked like a tiny yellow or orange planetary nebula, only slightly bigger than a star, and of uniform brightness. The following night, October 25, it still looked like a star to the unaided eye, but in binoculars it was larger than the previous night. The total brightness had not diminished. In the telescope, the comet was truly spectacular, made all the more amazing considering how the comet was only 43° away from the closest full moon of the year! The round coma contained a bright off-center fan-shaped wedge with a brilliant tiny pointlike nucleus. There was definitely evidence of concentric, spiraling shells of material opening outward from the center of the coma to the outermost parts of the coma.

You have just got to get out to see this comet! And as often as possible! Here is an ephemeris for Dodgeville for the coming week.


TSTW 11/1/07

Comet Holmes (17P)

Comet Holmes slowly moves towards Mirfak this week, an impressive binocular and telescopic object in Perseus. It is easily visible to the unaided eye, too, as a small fuzzball on the Capella-side of Perseus.

Sunlight and solar wind particles are hitting the comet on the north-northeast side, and photographs show the comet is sharp edged there. The opposite, south-southwest side is ragged, with ionized gas streamers spreading out in that direction in long-exposure photographs.

Whatever tail the comet has is pretty much hidden behind it, as our viewing angle (known as the phase angle) diminishes from 15° to 13° this week. The phase angle is the Sun – Comet – Earth angle. A phase angle of 0° would mean we are looking directly down the tail (least favorable, maximum foreshortening). A phase angle of 90° would mean we are looking perpendicular to the tail (most favorable, no foreshortening).

Prime time for observing the comet is pretty much all night, with the comet transiting the celestial meridian at 2:05 a.m. CDT at the beginning of the week, and at 12:30 a.m. CST by the end of the week. Look at it every clear night, because surprising changes can and do occur. Don’t miss it! It may be a while until something like this happens again. The last time Comet Holmes went into a major outburst was 115 years ago!

Orion’s Throwing Stones!

Monday evening, October 21st, and Tuesday morning, October 22nd, will be the best time to watch the Orionid meteor shower, one of the year’s best meteor showers.

Up to two dozen meteors per hour might be seen between the hours of 3:00 a.m. and 5:00 a.m. or so— provided you can keep the 40%-lit waning crescent moon out of your field of view.

When to Watch:

10:16 p.m. Monday, October 21 through 12:19 a.m. Tuesday, October 22 (radiant rise in the ENE to moonrise)*

12:19 a.m. through 5:47 a.m. Tuesday, October 22 (moonlight will interfere; radiant will be highest in the sky at 5:18 a.m., and morning twilight begins at 5:47 a.m.)

Where to Be: In a rural area with no terrestrial lights visible that are brighter than the brightest star. Preferably no light domes (uncivil twilight) of cities or towns should be visible in the direction you will be looking.

What to Do: Dress for a temperature 20° F cooler than the actual air temperature. Bring a lawn chair and a warm sleeping bag or blankets. Try blocking the Moon with a building, hill, or trees— or use a strategically-placed black umbrella.

Where to Look: Generally look towards the radiant which is between Betelgeuse and the “feet” of Gemini.

What You’ll See: Fast meteors, many leaving persistent trains.

Meteor showers occur each year when the Earth in her orbit intersects the debris trail of a comet, and the comet that causes the Orionids is very famous, indeed. Halley’s Comet!

* Times listed are for Dodgeville, Wisconsin

Radio Telescope in a Carpet

The lunar farside would be a splendid place to do radio astronomy. First, the cacophony of the Earth would be silenced by up to 2,160 miles of rock. Second, lacking an atmosphere, a radio telescope located on the lunar surface would be able to detect radio waves at frequencies that are absorbed or reflected back into space by the Earth’s ionosphere.

Radio waves below a frequency of 10 MHz (λ ≥ 30 m) cannot pass through the ionosphere to reach the Earth’s surface. The Earth’s atmosphere is variably opaque to radio waves in the frequency range of 10 MHz to 30 MHz (λ = 10 to 30 m), depending upon conditions. The Earth’s atmosphere is mostly transparent to frequencies between 30 MHz (10 m) and 22 GHz (1.4 cm).

Not surprisingly, electromagnetic radiation of a non-terrestrial origin having wavelengths longer than 10 meters has been little studied. If we look, we might discover new types of objects and phenomena.

The best part is the lunar radio telescope wouldn’t have to be a steerable parabolic dish, but instead could be a series of dipole antennas (simple metal rods or wires) imbedded into a plastic carpet that could easily be rolled out onto the lunar surface. This type of radio telescope is “steered” (pointed) electronically through phasing of the dipole elements.

Even though the ever-increasing number of lunar satellites should be communicating at wavelengths far shorter than 10 meters, care must be taken to minimize their impact (both communication and noise emissions) upon all lunar farside radio astronomy.

There’s a Meteor in My Image!

The night of August 16, 2019 UT, I was hoping to be the first person to record an occultation of a star by the asteroid 10373 MacRobert, named after Sky & Telescope senior editor Alan MacRobert. Alas, it was not to be, but I did receive a celestial consolation prize (or is that a constellation prize?) just as rare: a meteor! Here it is:

Kappa Cygnid recorded on 16 Aug 2019, 3:51:21.540 – 3:51:21.807 UT (0.267s, field size ~ 15′)

In the caption above, you’ll note that I stated this was a Kappa Cygnid meteor. How did I determine that?

The first step is to determine the direction the meteor traveled through the image. Since I have an equatorially-mounted telescope, north is always up and east is to the left, just like in the real sky. Using Bill Gray’s remarkable Guide planetarium software, which I always use when imaging at the telescope, I identified two stars (and their coordinates) very close to the path of the meteor across the field. The meteor flashed through the field so quickly that I am not able to determine whether the meteor was traveling from NNE to SSW or vice versa. But since I was imaging in Sagittarius, south of all the radiants active on that date, it is most likely that the meteor was traveling NNE to SSW. But, of course, it could have been a sporadic meteor coming from any direction, though as you will see, I think I can convincingly rule out that scenario.

The two stars very close to the meteor’s path were:

3UC 148-239423
α = 17h 56m 38.42s, δ = -16° 23′ 27.1″

3UC 147-243087
α = 17h 56m 31.96s, δ = -16° 30′ 40.0″

The right ascensions and declinations above are epoch of date.

Now, if this meteor came from a particular radiant, a great circle from the meteor shower radiant to either of the two stars (or the midpoint along the line connecting them) should be in the same direction as the direction between the two stars crossed by the meteor.

Meteor shower radiants drift from night to night as the Earth passes through the meteor stream due to its orbital motion around the Sun. We must find the radiant position for each meteor shower that was active on August 16, 2019 UT for that date.

Antihelion, South δ Aquariid, α Capricornid, and Piscis Austrinid meteor shower radiant drift
Source: International Meteor Organization, https://www.imo.net/files/meteor-shower/cal2019.pdf
Perseid meteor shower radiant drift
Source: International Meteor Organization, https://www.imo.net/files/meteor-shower/cal2020.pdf
Kappa Cygnid meteor shower radiant drift
Source: International Meteor Organization, https://www.imo.net/files/meteor-shower/cal2020.pdf

Looking at Table 6, Radiant positions during the year in α and δ, on p. 25 of the International Meteor Organization’s 2019 Meteor Shower Calendar, edited by edited Jürgen Rendtel, we find that four major meteor showers were active on August 16: the Antihelion source, which is active throughout the year (ANT), the Kappa Cygnids (KCG), the Perseids (PER), and the South Delta Aquariids (SDA). Though right ascension and declination for these radiants (presumably epoch of date) are not given specifically for August 16, we can interpolate the values given for August 15 and 20. Note that the right ascensions are given in degrees rather than in traditional hours, minutes, and seconds of time.

We are now ready to plug all these numbers into a SAS program I wrote that should help us identify the likely source of the meteor in the image.

The results show us that the Kappa Cygnids are the likely source of the meteor in the image, with a radiant that is located towards the NNE (15.8˚) from the “pointer stars” in our image, at a bearing that is just 3.7˚ different from their orientation.

Space Travel Under Constant 1g Acceleration

The basic principle behind every high-thrust interplanetary space probe is to accelerate briefly and then coast, following an elliptical, parabolic, or mildly hyperbolic solar trajectory to your destination, using gravity assists whenever possible. But this is very slow.

Imagine, for a moment, that we have a spacecraft that is capable of a constant 1g (“one gee” = 9.8 m/s2) acceleration. Your spacecraft accelerates for the first half of the journey, and then decelerates for the second half of the journey to allow an extended visit at your destination. A constant 1g acceleration would afford human occupants the comfort of an earthlike gravitational environment where you would not be weightless except during very brief periods during the mission. Granted such a rocket ship would require a tremendous source of power, far beyond what today’s chemical rockets can deliver, but the day will come—perhaps even in our lifetimes—when probes and people will routinely travel the solar system in just a few days. Journeys to the stars, however, will be much more difficult.

The key to tomorrow’s space propulsion systems will be fusion and, later, matter-antimatter annihilation. The fusion of hydrogen into helium provides energy E = 0.008 mc2. This may not seem like much energy, but when today’s technological hurdles are overcome, fusion reactors will produce far more energy in a manner far safer than today’s fission reactors. Matter-antimatter annihilation, on the other hand, completely converts mass into energy in the amount given by Einstein’s famous equation E = mc2. You cannot get any more energy than this out of any conceivable on-board power or propulsion system. Of course, no system is perfect, so there will be some losses that will reduce the efficiency of even the best fusion or matter-antimatter propulsion system by a few percent.

How long would it take to travel from Earth to the Moon or any of the planets in our solar system under constant 1g acceleration for the first half of the journey and constant 1g deceleration during the second half of the journey? Using the equations below, you can calculate this easily.

Keep in mind that under a constant 1g acceleration, your velocity quickly becomes so great that you can assume a straight-line trajectory from point a to point b anywhere in our solar system.

Maximum velocity is reached at the halfway point (when you stop accelerating and begin decelerating) and is given by

The energy per unit mass needed for the trip (one way) is then given by

How much fuel will you need for the journey?

hydrogen fusion into helium gives: Efusion = 0.008 mfuel c2

matter-antimatter annihilation gives: Eanti = mfuel c2

This assumes 100% of the fuel goes into propelling the spacecraft, but of course there will be energy losses and operational energy requirements which will require a greater amount of fuel than this. Moreover, we are here calculating the amount of fuel you’ll need for each kg of payload. We would need to use calculus to determine how much additional energy will be needed to accelerate the ever changing amount of fuel as well. The journey may well be analogous to the traveler not being able to carry enough water to survive crossing the desert on foot.

Now, let’s use the equations above for a journey to the nearest stars. There are currently 58 known stars within 15 light years. The nearest is the triple star system Alpha Centauri A & B and Proxima Centauri (4.3 ly), and the farthest is LHS 292 (14.9 ly).

I predict that interstellar travel will remain impractical until we figure out a way to harness the vacuum energy of spacetime itself. If we could extract energy from the medium through which we travel, we wouldn’t need to carry fuel onboard the spacecraft.

We already do something analogous to this when we perform a gravity assist maneuver. As the illustration below shows, the spacecraft “borrows” energy by infinitesimally slowing down the much more massive Jupiter in its orbit around the Sun and transferring that energy to the tiny spacecraft so that it speeds up and changes direction. When the spacecraft leaves the gravitational sphere of influence of Jupiter, it is traveling just as fast as it did when it entered it, but now the spacecraft is farther from the Sun and moving faster than it would have otherwise.

Reference: https://www.daviddarling.info/encyclopedia/G/gravityassist.html

Of course, our spacecraft will be “in the middle of nowhere” traveling through interstellar space, but what if space itself has energy we can borrow?

Satellite, Meteor, and Aircraft Crossings 2019

Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but on October 4, 1957 another “species” of sky vermin made its debut: artificial satellites.  In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my ~¼° field of view.

I’ve put together a video montage of satellites I serendipitously recorded between March 31, 2019 and July 12, 2019.  Many of the satellite crossings are moving across the fields as “dashes” because of the longer integration times I need to use for some of my asteroid occultation work. A table of these events is shown below the video. The range is the distance between observer and satellite at the time of observation.

Satellites in higher orbits take longer to cross the field. When possible, I’ve included graphs of brightness as a function of time for these slower-moving satellites after each individual video and corresponding table. When you watch the videos of geostationary satellites, you are actually seeing the rotation of the Earth as the line between you and the satellite sweeps across the stars as the Earth rotates!

Uncertain of identification
A tumbler with sun glints!
A high-amplitude tumbler! Satellite is no longer operational.

I caught one meteor on 4 Jan 2019 between 5:32:57 and 5:32:59 UT. Field location was UCAC4 419-017279. I’m pretty sure the meteor was a Quadrantid!

And two aircraft crossed my field: on 7 Dec 2018 1:40:05 – 1:40:13 UT (UCAC4 563-026131) and 26 Jun 2019 5:02:07 – 5:02:10 UT (UCAC4 291-144196).

And high energy particles (natural radioactivity or cosmic rays) “zing” my CCD/CMOS detector every once in a while. Here are a few examples: 5 Jan 2019 3:46:00 – 3:46:02 UT (UCAC4 473-001074); 20 Apr 2019 3:41:46 – 3:41:47 UT (UCAC4 501-062663); 30 Jun 2019 7:37:31 – 7:37:33 (UCAC4 354-179484) and 7:47:41 – 7:46:44 (TYC 6243-00130-1).

References
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21

Asteroids: Take a Number

Italian monk, mathematician, and astronomer Giuseppe Piazzi (1746-1826) discovered an unexpected 8th magnitude object in Taurus near Mars and the Pleiades at around 8:00 p.m. on January 1, 1801 at his observatory in Palermo, Sicily. Thinking it a comet, he recorded the position of the object over several nights, until illness forced him to quit on February 11, just a few days after the object passed fairly close to Mars. By early May, the object was too close to the Sun in the western sky to observe, and Piazzi despaired of ever recovering the object. The now-famous 24-year-old German mathematician Carl Gauss (1777-1855) came to the rescue. Gauss used Piazzi’s positions to determine an orbit for Ceres (so named by Piazzi) and predicted from the scant data its future positions when it would once again be visible in the night sky. Ceres was recovered only a half-degree away from its predicted position by Hungarian astronomer Franz Xaver von Zach (1754-1832) on December 7, close to Denebola and not far from a close conjunction of the planets Jupiter and Saturn, and then confirmed after a long stretch of cloudy weather on December 31, 1801. The German amateur astronomer Heinrich Olbers (1758-1840) found Ceres at Bremen two days later on January 2, 1802. Olbers (of Olbers’ Paradox fame) discovered the second asteroid, Pallas, on March 28, 1802. Many, many more asteroids have been discovered since then. They are sequentially numbered, originally in order of their discovery date, but nowadays in order of their receiving a precise orbit determination.

Fast forward.

The names of asteroids 998 through 1002, discovered between August 6-15, 1923, have special significance.

998 Bodea – named in honor of German astronomer Johann Elert Bode (1747-1826), whose empirical relationship of the distances of the planets (Titius-Bode Law) indicated that there should be a planet between the orbits of Mars and Jupiter, touching off a massive search led by von Zach for a new planet.

999 Zachia – named in honor of Franz Xaver von Zach, who published Piazzi’s observations and recovered Ceres after Gauss’ predicted positions.

1000 Piazzia – named in honor of Giuseppe Piazzi, who discovered the first asteroid, 1 Ceres.

1001 Gaussia – named in honor of Carl Friedrich Gauss, who predicted the position of Ceres so it could be recovered.

1002 Olbersia – named in honor of Heinrich Olbers who was the second person to recover Ceres and the discoverer of the second asteroid, 2 Pallas (and 4 Vesta, by the way).

Fortunately, German astronomer Johann Daniel Titius (1729-1796) finally did get an asteroid named after him as well: 1998 Titius, discovered on February 24, 1938.

As of August 19, 2019, 796,422 minor planets (asteroids, trans-Neptunian objects, etc., but not including comets) have been discovered, but only 541,128 have orbits that are well-enough determined that they have been given a minor planet number. When a minor planet is first discovered, it is given a provisional designation based on the date of discovery. For example, 2019 PE3 was discovered during the first half of August 2019. After enough high-quality astrometric data has been collected to determine an accurate orbit, the minor planet is assigned a number. For example, minor planet 1996 TB1 was discovered by IOTA member George Viscome on October 5, 1996. It received a number, 35283, in 2000, and it received a name, Bradtimerson, earlier this year (2019). George submitted the name to the IAU after Brad Timerson, mentor and inspiration to many of the current crop of asteroid occultation observers, passed away on October 17, 2018. So we now have 35283 Bradtimerson.

The counts in the paragraph above show us that 67.9% of the minor planets that have been discovered have been assigned a number. Of these, only 21,922 (4.1%) have received a name.

Many asteroids have been given interesting or unusual names. Excluding the many fine individuals (real, not fictional) who have an asteroid named after them, here are a few of my favorites. There are a few here that are actually named after a person, but the minor planet name has a meaning beyond just the person’s name.

Remember, these are real places that will be visited someday. Oh, to be so lucky!

Lots of asteroids are awaiting names. Can you come up with some interesting, entertaining, or poetic ones? Give it a try, check this list or do a search here to make sure it is new, and then post a comment here and I’ll probably include your ideas in this article, giving you credit, of course. Be creative!

To get you in the spirit, here are a few names I’ve come up with:

  • Botanica
  • Distantia
  • Eternium
  • Gandalf
  • Luminaria
  • Morethanamote
  • Portentia
  • Symphonica

Have fun!

Cometary Tails

A comet’s ion/plasma/gas tail points directly away from the Sun. A comet’s dust tail deviates somewhat (and sometimes a lot) from this, falling behind the comet along its orbital path around the Sun.

For the best view of either tail, our line of sight should be perpendicular to the length of the tail. However, that seldom happens, and we are viewing the tails with some degree of foreshortening. The orientation of the gas tail is called the phase angle, and it is the Sun – comet – observer angle.

A phase angle of 0° indicates we are looking straight down the tail of the comet (maximum foreshortening) with the head being oriented closest to the observer.

A phase angle of 90° indicates that our line-of-sight to the comet is perpendicular to the Sun-comet line, so we are viewing the comet’s gas tail with no foreshortening.

A phase angle of 180° indicates that we are again looking straight down the gas tail of the comet (again, maximum foreshortening) only this time the tail is closer to the observer and the head further away. Of course, the only time this orientation could happen is when the comet is transiting the Sun, thus rendering it essentially unobservable.

Phase angles of 0 to 90° mean that the comet head is closer to the observer than the tail; angles of 90 – 180° mean that the comet’s tail is closer to the observer than the head.

Here’s a table showing the phase angle, and some other information, for currently-observable comets brighter than 15th magnitude as seen from Earth. The column labeled Elongation indicates the Sun – observer – comet angle. In other words, the angular separation between the Sun and the comet.

A comet that is farther from the Sun than the observer can never have a phase angle as great as 90°, but a comet that is closer to the Sun than the observer can. Looking at the diagram above and considering a comet in a circular orbit around the Sun (highly unlikely, I know, but bear with me) and closer to the Sun than the observer, the phase angle would be 90° when the comet is at greatest elongation.

Incidentally, comet designations that have a number followed by the letter “P” (such as 29P, 68P, and 260P) are periodic comets (more precisely described as short-period comets), defined to be comets with orbital periods of less than 200 years or that have been observed at more than one perihelion passage.

Scythia Sweet

One of the enjoyable aspects of recording asteroids passing in front of stars (we call them asteroid occultations) is the interesting names of some of the asteroids. This month, Bob Dunford, Steve Messner, and I had two double-chord events across the asteroid 1306 Scythia, discovered in this month of 1930 by Soviet astronomer Grigory Neujmin (1886-1946).

The name 1306 Scythia immediately brought to mind a favorite piece of music, the Scythian Suite—surely one of the most unusual and otherworldly compositions by Sergei Prokofiev, or anyone else for that matter.

A quick look at the entry for 1306 Scythia in the 5th edition of Dictionary of Minor Planet Names by Lutz D. Schmadel (1942-2016) quickly confirmed my suspicion that the subject matter of both asteroid and musical composition is the same.

Named for the country of the ancient Scythians comprising parts of Europe and Asia now in the U.S.S.R. in regions north of the Black sea and east of the Aral sea.

In the wee hours of Friday, July 12, Bob Dunford in Illinois and I in Wisconsin observed only the second asteroid occultation of 1306 Scythia (and the first since 2014). The predicted path is shown below.

Predicted shadow path of the asteroid 1306 Scythia from the star Tycho 5189-597-1 (UCAC4 414-136241) on 12 July 2019 UT.

Bob, who was observing at Naperville, observed a 4.3-second dip in brightness as the asteroid covered the star between 8:23:46.203 and 8:23:50.531 UT, and I, observing at Dodgeville, observed a 1.3-second event between 8:24:01.783 and 8:24:03.054. Our light curves are shown below.

Bob Dunford’s light curve of the 1306 Scythia / Tycho 5189-597-1 event of 12 July 2019 UT, using a 14-inch telescope.
David Oesper’s light curve of the 1306 Scythia / Tycho 5189-597-1 event of 12 July 2019 UT, using a 12-inch telescope.

Here’s a map showing our observing locations relative to the predicted path.

1306 Scythia / Tycho 5189-597-1 event of 12 July 2019 UT – Predicted Path and Observer Locations

Here’s the profile showing the chords across the asteroid.

1306 Scythia / Tycho 5189-597-1 event of 12 July 2019 UT – Asteroid Profile and Chords

Just four days later, both Bob Dunford and I had a high probability event of the same asteroid passing in front of a different star, and this time we were joined by Steve Messner. Bob and Steve both got positives! Unfortunately, I was clouded out.

Predicted shadow path of the asteroid 1306 Scythia from the star TYC 5188-573-1 on 16 July 2019 UT.
1306 Scythia / Tycho 5188-573-1 event of 16 July 2019 UT – Predicted Path and Observer Locations
1306 Scythia / Tycho 5188-573-1 event of 16 July 2019 UT – Asteroid Profile and Chords

Sergei Prokofiev (1891-1953) wrote the Scythian Suite in 1915 when he was 24 years of age. Even at that young age, Prokofiev already showed great talent and originality.

Sergei Prokofiev, circa 1918

Here are some excerpts of the Scythian Suite performed by the Minnesota Orchestra conducted by Stanisław Skrowaczewski. This is a 1983 recording (Vox Box CD3X 3016). The movement descriptions are based on those given in Wikipedia.

1st movement: Invocation to Veles and Ala – barbaric and colorful music describing the Scythians’ invocation of the sun.

Some of the music you’ve heard in the original “Star Trek” certainly was inspired by this.
Alien landscape music
Alien landscape music #2

2nd movement: The Alien God and the Dance of the Evil Spirits – as the Scythians make a sacrifice to Ala, daughter of Veles, the Alien God performs a violent dance surrounded by seven monsters.

Best to observe this nasty dance from a distance…
This certainly reminds me of Dmitri Shostakovich, but he was only 9 years old at the time and just beginning to compose!

3rd movement: Night – the Alien God harms Ala; the Moon Maidens descend to console her.

This beautiful movement of many moods begins peacefully, then moves to a section of descending lines that might remind you of “The Planets” by Gustav Holst, but this was being written at the exact same time as the Scythian Suite! Next the music takes an ominous turn, and then returns to a little night music, but more a travel through interstellar or intergalactic space rather than a terrestrial night.

4th movement: The Glorious Departure of Lolli and the Cortège of the Sun – Lolli, the hero, comes to save Ala; the Sun God assists him in defeating the Alien God. They are victorious, and the suite ends with a musical picture of the sunrise.

Here, now, the conclusion of this remarkable work.

Prokofiev’s Scythian Suite. There is nothing else like it in the orchestral repertoire!