As of this writing, three objects have been discovered that have passed through our solar system coming from interstellar space.
1I/’Oumuamua Discovery Date: 2017-10-19 Perihelion Date: 2017-09-09 (40 days after perihelion) Perihelion Distance: 0.26 AU Incoming and Outgoing Speed: 26.4 km/s Dimensions: approximately 115 m × 111 m × 19 m, or 230 m × 35m × 35m Object Type: asteroid?
2I/Borisov Discovery Date: 2019-08-29 Perihelion Date: 2019-12-08 (101 days before perihelion) Perihelion Distance: 2.01 AU Incoming and Outgoing Speed: 32.3 km/s Diameter: 400 m – 1000 m Object Type: comet
3I/Atlas Discovery Date: 2025-07-01 Perihelion Date: 2025-10-29 (120 days before perihelion) Perihelion Distance: 1.36 AU Incoming and Outgoing Speed: 58.0 km/s Diameter: 320 m – 5,600 m (most likely 520 m – 748 m) Object Type: comet
Here are charts showing the direction from which each object entered our solar system, and the direction towards which each object is leaving our solar system.
1I/’Oumuamua came in from the direction of the constellation Lyra1I/’Oumuamua is exiting in a direction inside the Square of Pegasus2I/Borisov came in from the direction of the constellation Cassiopeia2I/Borisov is exiting in the direction of the southern constellation Telescopium3I/Atlas came in from the direction of the constellation Sagittarius3I/Atlas is exiting in the direction of the constellation Gemini
It is perhaps not surprising that 1I/’Oumuamua had the greatest deflection angle of the three interstellar objects. It came quite close to the Sun (0.26 AU, well inside the orbit of Mercury) and had the lowest incoming speed (26.4 km/s).
3I/Atlas, on the other hand, had the greatest incoming speed by far (58.0 km/s), so it was deflected by only 18.7° from a straight-line trajectory (angular separation 180° and deflection angle 0°).
A massive foreground object such as a galaxy or a galaxy cluster (including, of course, dark matter) can brighten and magnify a distant object. This is called gravitational lensing. Light from the distant object radiates out in all directions, but the massive foreground object bends some of these light rays towards the observer that normally would have continued on in a different direction, as shown in the illustration above.
The image we see is brighter because more light rays are directed our way. The image we see is also magnified because the gravitational lens gives the distant object a larger angular size, making it appear to be much closer to us. Again, the illustration above will help you understand why these effects occur.
Of course, unless the foreground object is a star or black hole or some other small spherical object with a reasonably uniform mass distribution, the gravitational lens effect will be complex and distorted, as illustrated below.
Gravitational lenses produce different shaped images depending on the shape of the lensing body. If the lens is spherical then the image appears as an Einstein ring (in other words as a ring of light) (top); if the lens is elongated then the image is an Einstein cross (it appears split into four distinct images) (middle), and if the lens is a galaxy cluster, then arcs and arclets (banana-shaped images) of light are formed (bottom). Credit: European Space Agency
There can be certain locations in a gravitational lens where light from a small region in the background becomes enormously magnified by a factor of up to 10,000 times. These regions are called caustics. Though the concept of a caustic is a bit difficult to describe or illustrate, here is a video of optical caustics caused by a laser pointer shining through a plastic disc with a lumpy surface.
There are three stable (non-radioactive) isotopes of the element oxygen:
16O has 8 protons and 8 neutrons
17O has 8 protons and 9 neutrons
18O has 8 protons and 10 neutrons
All the oxygen in our solar system was forged in stars that existed before the birth of our Sun. The fusion processes that create oxygen from lighter elements require both high temperature and pressure. These conditions exist deep within a star. Different isotopes are created. A nucleus of an atom containing 8 protons identifies it as an oxygen atom, but it is the number of neutrons in the nucleus that determines which isotope it is. Not all isotopes are created in equal abundance.
When the solar system was forming, the oxygen in the “solar nebula” no doubt originally came from various progenitors. A supernova here or there, a planetary nebula somewhere else, and so on. As the solar nebula collapsed to form the Sun and planets, the relative abundance of oxygen to the other elements may or may not have been different in different parts of the solar nebula. Similarly, the relative abundances of the three stable isotopes of oxygen may also have been different in different parts of the solar nebula.
When we measure the relative amounts of the three oxygen isotopes in a terrestrial rock, ocean water, moon rocks, or the solar wind, it may tell us where the oxygen in those materials came from. It may also tell us something about the “life experiences” of the oxygen since the solar system formed. For example, water molecules containing 16O are more likely to evaporate than those water molecules containing the heavier isotopes 17O or 18O. Thus, ground water in the middle of a continent has a higher abundance of 16O than does water in the ocean.
When we look at the solar system today, we find significant differences in the relative abundances of the oxygen isotopes depending on where the material came from. On Earth, 99.75% of the oxygen atoms are of the 16O variety, 0.04% are 17O, and 0.21% are 18O, on average. We see very similar oxygen abundance ratios in moon rocks, indicating perhaps a common origin, but the oxygen abundance ratios in meteorites and solar wind particles are significantly different from this. For example, if you plot the 17O/16O ratio vs. the 18O/16O ratio for a bunch of terrestrial rocks, you get pretty much a straight line. Moon rocks fall along the same line. The calcium-aluminum-rich inclusions (CAI) and iron-magnesium-silicon chondrules in meteorites also form a straight line on this plot, but it has a distinctly different slope.
The solar wind samples collected by the Genesis spacecraft yielded abundances that fall along the same line as the CAIs and chondrules. Mars rocks fall on a line that parallels the Earth-Moon line, but is shifted upwards, indicating that for a given abundance of 18O, the Mars rocks will have a relatively higher abundance of 17O.
If you have a neighbor with a dusk-to-dawn insecurity light or a glare bomb that happens to be turned on while you’re engaged in astronomical pursuits, I have come up with a solution.
In the photo above, you will see a Uline 6 × 6′ Welding Screen Shade 8 (H-4610S8). The Shade 8 black vinyl tarp is almost opaque1 and does not have an objectionable odor, so you can store it in the house when not in use. I also ordered the optional set of four swivel casters from Uline (H-5388) so that the frame can easily be moved around by one person. One of these swivel casters is shown in the photo below.
I store the frame outdoors against the house under the patio roof. The canopy weight plates and frame’s minimal wind loading profile ensures that the frame will stay in place even in high winds. Once I roll the frame to the needed location to block the offending light, I use the canopy weight plates to keep the frame from moving while I am observing.
DSG Canopy Weight Plates from Dick’s Sporting Goods come as a set of four, and each one weighs 7.5 lbs. These keep the frame from moving during storage and when in use to block a neighbor’s light.
Since I wanted an easy way to hang the vinyl tarp on the frame and then remove it for storage inside after my observing session, I used four S-hooks from Ace Hardware. I used heavy-duty slip joint pliers to squeeze together the wide part of the S-hook that goes over the top of the frame so that it can’t come off of the frame. See the photo below.
To keep the S-hooks from sliding down off of the top of the frame, I made a couple of stops using Snake Wrap as shown in the photo below.
In addition to using the four S-hooks to hang the tarp, I also use a shoelace through the grommet nearest the top on each side to keep the tarp fully extended during light to moderate winds, as shown below.
In the final two photos, you see how the tarp moves as the wind blows against it. Allowing the lower part of the tarp to move when the wind blows reduces the wind loading on the light-blocking curtain.
Only a tiny amount of light gets through the Uline Shade 8 black vinyl tarp (i.e. you can see where the light is on the other side of the tarp if you look right at it). If the light you are trying to block is extremely bright and you require a completely opaque tarp, if you can’t find a suitable 6 × 6′ tarp with at least four grommets on each side, I’d recommend purchasing a 5′ 6″ × 7′ 6″ Heavy Duty Reflective All-Purpose Weather-Resistant 9 mil Tarp from Harbor Freight. You’ll want to fold the long side at the bottom and hook the flap to the rest of the tarp using cable ties through the grommets so the length doesn’t exceed 6 ft. ↩︎
We humans love to name things, and that extends to the heavens as well. The International Astronomical Union (IAU) has a working group and several task groups whose responsibility it is to approve the official names of topographic features of the planets, satellites, and minor objects in our solar system. Current members are listed here:
IAU Working Group and Task Group Members
You’ll find more information, search functionality, and alphabetical (alpha-beta-ical) lists of features at https://planetarynames.wr.usgs.gov/.
Incidentally, you might notice that many craters on Mercury are named after composers. Since many of the craters on the Moon are named after scientists, in fairness it was decided that many of the craters of Mercury (ostensibly similar to the Moon) should be named after composers, artists, writers, and others who have contributed to the arts and humanities. So there you have it!
Cecilia Payne-Gaposchkin (1900-1979), as a woman, had to endure an enormous number of challenges and setbacks but her perseverance, professional dedication, and brilliance led her to become one of the important astrophysicists in the 20th century. In her 1925 Ph.D. thesis, Cecilia Payne demonstrated that stars are primarily composed of hydrogen and helium. This was highly controversial at the time, but she was eventually proved correct. In 1960, the noted astronomer Otto Struve called her 1925 thesis, Stellar Atmospheres; A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars “the most brilliant Ph.D. thesis ever written in astronomy.” Cecilia Payne-Gaposchkin would make an excellent subject for a full-length documentary as well as a biographical movie, and it is disgraceful that neither has been done yet.
I recently completed teaching a new five-week course on the English composer Gustav Holst (1874-1934). The research I did for that course plus my lifelong interest in astrophysics naturally led me to take an interest in the relationship between Cecilia Payne and Gustav Holst. Clearly from what you will see below, they had profound respect and admiration for each other.
Cecilia Payne attended St. Paul’ Girls’ School, where Gustav Holst taught, during the 1918-1919 school year. However, Holst left for war service in Salonika, Greece on October 29, 1918 and didn’t return to St. Paul’s until the 1919-1920 school year, after Payne had graduated and gone on to the University of Cambridge in Cambridge, England.
Frances Ralph Gray was the founding “high mistress” of St. Paul’s School for Girls in the Brook Green neighborhood of London…Like Cecilia, she adored music; unlike Cecilia, she had had great difficulty learning mathematics. Also unlike Cecilia, she was small in stature. She was, however, commanding in presence. Students reported that being sent to see Miss Gray “was their greatest fear.”
Frances perceived that there was something different about the seventeen-year-old girl in her office who so wanted to be admitted. Yes, Cecilia had been told to leave her current school, but not because she was disruptive or a problem learner—quite the opposite. She was a serious student who loved music and science, whose goal was to go to Cambridge. She had responded to Elizabeth Edwards and to Dorothy Daglish. If St. Paul’s had similar teachers who could recognize Cecilia’s love of learning and would take time to nurture her, surely she would be a good fit.
Years later, in a touching letter recommending Cecilia for a fellowship at Harvard, Frances wrote: “It is not my practice to admit girls who have reached the age at which Cecilia Payne was admitted [age seventeen], but I was requested to make an exception in her case by the headmistress of the School she had previously attended, who assured me that she was a girl of very unusual promise.”
Unbeknownst to Cecilia, St. Paul’s needed her as much as she needed the school. Founded just over a decade earlier by the Worshipful Company of Mercers, it prided itself on consistently outperforming other schools. The “Paulinas” were not viewed as, or trained to be, socialites; this was a serious school. The social snobbery of other private schools had no place here.
Cecilia described her move to St. Paul’s as stepping from medieval times into the modern day. Instead of chapels there were laboratories—in biology, chemistry, physics—and teachers who were specialists. Here she was not just “allowed” to study science; she was encouraged. She only attended the school for one year. But from the moment she approached the Queen Anne-style pink brick building and walked up the stone steps and through the marble and oak arched front door, she was home.1
Donovan Moore goes on now to write about Holst.
Frances Gray…made good on her professed love of music when she hired Gustav Holst. Holst was a relatively unknown trombone player when he accepted the job of director of music at St. Paul’s. Like Cecilia, he was shy and reserved, and he disdained fame. And like Cecilia, he was practiced in overcoming obstacles: neuritis in his right arm had forced him to stop playing the trombone and the piano, so he had to turn to composing.
Frances encouraged him; in fact, she worked with him, supplying the text for both a light-hearted masked dance in 1909 and a more ambitious orchestra work three years later. She had an entire music wing built in 1913, including a large soundproof room where Gustav composed on Sundays, when the school was locked up, in silence and solitude. It was in this room that he wrote his most famous work, the orchestra suite The Planets. Cecilia was among a group of students who heard it performed shortly after it was composed.2
As we shall see later through Cecilia’s own words, she must have heard some sort of run-through of The Planets at St. Paul’s. I wonder whether she was among the invited audience of about 250 people who attended the first performance of The Planets at Queen’s Hall, London, on Sunday, September 29, 1918, with Adrian Boult conducting the New Queen’s Hall Orchestra? Given that the choir for “Neptune: The Mystic” in that performance was comprised, in whole or in part, of students from St. Paul’s, it is possible she was present for the Queen’s Hall performance though perhaps unlikely given that the audience consisted of close friends and associates of Holst and many professional musicians in London.
Holst was also a great teacher. For three decades—from 1905 until his death in 1934—”Gussie”, as he was known, would cast his musical spell over his students. The contemporary composer Ralph Vaughan Williams described Holst’s long tenure at St. Paul’s: “He did away with the childish sentimentality that schoolgirls were supposed to appreciate and substituted Bach and Vittoria; a splendid background for immature minds.”
Holst discerned Cecilia’s love of music. He asked her to play her violin for him, made her a member of the school’s orchestra, and taught her how to conduct. He encouraged her to become a musician but did not prevail. Cecilia instinctively felt that a career in music would control her; as a scientist, she would be in control.3
In her autobiography, Cecilia Payne-Gaposchkin writes of St. Paul’s, Holst, and music:
The school ministered to my twin loves, science and music. Here I came under the spell of Gustav Holst, or “Gussie” as we affectionately called him. Aside from my shadowy Father, and my schoolboy brother, he was the first man I ever knew. He radiated music; the organ in the great hall reverberated to the great Toccata and fugue of Bach. Here for the first time I heard The Planets (then newly composed) and took part in a performance of the Hymn of Jesus. He was like a father to us, shy, abrupt and charming. He was quick to learn of my love of music, asked me to play the violin to him, and urged me to become a musician. I played in the orchestra, and learned conducting from him, but my love of science triumphed. It seems odd to think that the only career I was ever encouraged to follow was that of a musician. As a student at Cambridge I trained and conducted a choir that won an award. One of the judges told me that my conducting had been the decisive factor, and that my future lay there. Indeed, the feelings evoked by conducting a choir or orchestra are so powerful as to be overwhelming, but I recoiled instinctively from something I felt would control me; as a scientist I should be in control of my material. Who knows whether I was right?4
St. Paul’s Girls’ School did indeed have a great hall with an organ, so one wonders how Cecilia Payne heard The Planets there. It is also interesting that she first heard The Hymn of Jesus at St. Paul’s during her 1918-1919 school year, as the first known performance was on March 10, 1920 at the Royal College of Music with Holst conducting. Though Holst began composing the work during the summer of 1917, it was apparently not completed until after he returned from war service in Salonika, Greece on June 29, 1919. Cecilia Payne must have heard an early version of the work, or a part of it that had been completed.
Following four years at the University of Cambridge, Cecilia Payne arrived in New York aboard the RMS Laconia on Thursday, September 20, 1923, and from there proceeded to Cambridge, Massachusetts to begin her work in astronomy at Harvard University. Just a few months earlier, Gustav & Isobel Holst had visited the United States from April 27 through June 12, 1923. This was Isobel Holst’s only visit to the U.S., but Gustav would make two more visits, in 1929 and again in 1932.
Gustav Holst was in the United States from April 16-27, 1929, and on the evening of Friday, April 26, 1929, Holst gave a well-received lecture at Harvard University. It seems likely that Cecilia Payne would have attended that lecture and visited with Holst, but he was only in Cambridge for a day and had to take an early morning train to New York to board the RMS Samaria for the trip back to England. I have not been able to find any evidence that indicates they saw each other during Holst’s 1929 American visit.
Nor have I found any evidence that Cecilia Payne visited Holst in England after she moved to the United States in 1923, though New York ship passenger records show she arrived in New York from Southampton, England aboard the SS Leviathan on September 21, 1925, aboard the SS Berengaria on January 3, 1929, and aboard the SS Bremen on October 7, 1931 and August 30, 1933.
Gustav Holst and Cecilia Payne did meet again in 1932, when Holst conducted the Boston Symphony Orchestra at the first of two concerts in Symphony Hall in Boston.
After the concert Holst met Mrs. Arthur Foote and Cecilia Payne, a St. Paul’s Girls’ School alumna, who was studying astronomy.5
This would have been Friday, January 22, 1932, during Holst’s final visit to America. The all-Holst concert was at 2:30 p.m. and featured St. Paul’s Suite; Prelude and Scherzo, “Hammersmith” (Boston premiere); and the Ballet from the Opera, The Perfect Fool (Boston premiere); followed by an intermission and then The Planets. Here is the concert program courtesy of the Internet Archive which includes pages from the previous program suggesting that a last-minute program change occurred substituting St. Paul’s Suite for Somerset Rhapsody (an excellent early work by Holst, by the way) and switching the order of Hammersmith and The Perfect Fool:
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Incidentally, you might notice from the program that Arthur Fiedler was a violist in the orchestra and prepared the women’s chorus for the final movement of The Planets.
I met one ex Paulina at Harvard—Cecilia Payne who is doing research in astronomy.6
This is from a letter that Holst began on Tuesday, January 26, 1932 to his daughter Imogen.
He also spent some time with ex-Paulina Cecilia Payne, meeting her for lunch one day and for dinner at her place on another. This was followed by her lecture on a subject of great interest to him, the Zodiac.7
This was after Holst returned to Harvard from his four-day trip to Montreal and New York, and before his lecture at the Library of Congress in Washington, D.C., thus sometime between Tuesday, March 15 and Saturday, March 26, 1932.
Holst’s train from Ann Arbor arrived at Boston’s South Station at 11:15 a.m. on Saturday, May 21st. The next two days were spent packing and writing letters. He met with the Davisons the following morning and had dinner with Cecilia Payne at the Faculty Club that same evening.8
This dinner with Cecilia Payne would have been the evening of Sunday, May 22, 1932.
Later that same evening, Cecilia Payne drove Holst over to the observatory to view Jupiter and a star cluster. Holst enjoyed her company and visited with her again the day of his Boston departure.9
The observatory visit would have been on Tuesday, May 24. I’m guessing that the star cluster they observed after Jupiter would have been M13 in Hercules, which that evening was high in the eastern sky. Holst’s last visit with Cecilia Payne was on Thursday, May 26, 1932. Later that day, he left Boston by boat for New York where he boarded the SS Europa the following day to return to England. This was the last time Holst and Payne saw each other.
Cecilia Payne first met Russian-born astrophysicist Sergei Gaposchkin at the Astronomische Gesellschaft (Astronomical Society) meeting in Göttingen, Germany, on August 4, 1933. She helped him emigrate to the United States, and they were married on March 5, 1934. Less than three months later, Gustav Holst would be dead.
Moore, Donovan. 2020. What Stars Are Made of: The Life of Cecilia Payne-Gaposchkin. London, England: Harvard University Press, pp. 34-35. ↩︎
Haramundanis, Katherine. 1984. Cecilia Payne-Gaposchkin: An Autobiography and Other Recollections. Cambridge, England: Cambridge University Press, p. 108. ↩︎
Mitchell, Jon C. 2001. A Comprehensive Biography of Composer Gustav Holst, with Correspondence and Diary Excerpts: Including His American Years. New York, NY: Edwin Mellen Press, p. 442. ↩︎
Shadow path of UCAC4 379-071051 during its occultation by asteroid 2392 Jonathan Murray on April 18, 2025 UT
On April 18, 2025 UT, I observed an occultation of the 11.9-magnitude star (mv) UCAC4 379-071051 in the constellation Libra by the 17.7-magnitude asteroid (mv , at the time of observation) 2392 Jonathan Murray.
As you can see in the light curve below, I observed a two-dip event. Since the magnitude drops are unequal, that rules out an asteroid satellite.
2392 Jonathan Murray apparently covered up the brighter component of a heretofore unknown double star (either binary or optical), followed by a brief interlude before the fainter component was covered up.
The magnitude drop when the fainter star was occulted was 0.44. When the brighter star was occulted, the magnitude drop only goes down as far as the limiting magnitude of my sky in the images, which was around 14th magnitude (Tucson is not as dark as it once was). Using the magnitude drop when the fainter component was being covered by the asteroid (the only reliable magnitude drop we have), and knowing the magnitudes of the two components must sum to 11.9 magnitude, we can calculate that the magnitude of the two components are:
Primary Component (1st star occulted): 12.34
Secondary Component (2nd star occulted): 13.09
Occultation analysis expert Dave Gault (Australia) used my light curve and knowledge of the asteroid’s size and motion (and all the other factors that need to be considered) to provide the following preliminary double star solutions (there was not enough information for a single solution):
Double Star Solution #1 Separation = 36.9 mas Position Angle = 103.6°
Double Star Solution #2 Separation = 37.0 mas Position Angle = 113.8°
These two solutions are quite close to one another. Averaging the two separations, we get 36.95 milliarcseconds. Gaia DR3 indicates that the parallax of this star is 1.323 milliarcseconds. That’s a distance of almost 756 parsecs or 2,500 light years. At that distance, these two stars have an apparent separation (in the plane of the sky, so a minimum) of 28 AU, or a little less than the distance between the Sun and Neptune in our own solar system. This is not unreasonable for a true binary star system, but, of course, the fainter star could be many light years further away than the brighter star (which is presumably the component Gaia measured in determining the parallax). In that case, this would just be a chance alignment of two stars at different distances but not physically associated with one another.
High-resolution spectroscopic observations of UCAC4 379-071051 over time could determine whether or not this is a true binary star system. Astrometric measurements over time with whatever supercedes Gaia (likely) or analysis of occultations of this star by other asteroids (unlikely) could also determine whether or not these stars are a true binary star system.
Confounding factors in the double star solutions include (1) We don’t know the exact size of asteroid 2392 Jonathan Murray (Neowise gives a diameter of 6.5 miles); (2) We don’t yet know the shape or orientation (at event time) of this asteroid (my occultation observation was the first time this asteroid has been observed to occult a star); (3) We don’t know the orientation of my single observation chord (what part of the asteroid crossed the two stars).
As you can see, there’s a lot to consider in trying to interpret this atypical (though not all that unusual) “double dip” occultation event. Of course, the very first thing we did was to rule out any terrestrial cause of the second smaller dip (clouds, for example), and we had to also rule out any equipment anomalies that could have caused the second smaller dip (CCD anomalies, for example). After convincing ourselves that this was a real event, we proceeded with the analysis. A big thank you to Dave Gault and Dave Herald in Australia for their work and expertise in analyzing this data!
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:
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.
To the best of my knowledge, only 19 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.
726 Joëlla Discovered 1911 Nov 22 by Joel Hastings Metcalf (1866-1925) at Winchester, Massachusetts.
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).
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.
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″
