



Skip to: Asteroid novelties ✧ 21,922 total numbered and named ✧ Eureka! ✧ Dreaming of asteroids
n the first evening of 1801, Palermo Observatory director Giuseppe Piazzi noticed an extra star through his telescope among the others in Taurus that didn’t seem to belong there.
Its steady movement over the next few evenings convinced him he had found, at the very least, a new comet.
Piazzi named his object Ceres Ferdinandea after Ceres, the Roman goddess of agriculture, and King Ferdinand III of Sicily. The greater astronomical community, recalling Herschel had originally named his discovery after Britain’s King George III, met him halfway and jettisoned the Ferdinandea.
and 4 Vesta
shown to scale
The total number of asteroids on the books reached an even 100 with James Craig Watson’s discovery of Hekate in 1868, but the floodgates really opened with astrophotography pioneer Max Wolf toward the end of the century. Up until this time astronomers had to depend on their eyes and hand-drawn charts, but a photographic plate exposed an hour or more as the telescope followed the star field with a clock drive would reveal asteroids as tiny streaks. Wolf himself eventually discovered 248 of them, from 323 Brucia (a Mars crosser) in 1891 to 1214 Richilde in 1932, the last year of his life. Among his most notable was 588 Achilles, the first of many Jupiter Trojans — asteroids that pace Jupiter within its orbit either 60 degrees ahead of it or 60 degrees behind.
Here are eight asteroids and likely former asteroids in descending order of size. For comparison, Hyperion at 270 km (170 miles) is roughly the width of Northern Ireland or Massachusetts; at the other extreme a person could walk the length of Gaspra, 12 km (7.5 miles), in about two hours. Hyperion, Phoebe, Amalthea, and Phobos are widely understood to be asteroids captured by Saturn, Jupiter, and Mars.
Phoebe1 is much darker, reflecting 6% or about the same as lampblack. It’s also about three times as dense as Hyperion.
Edward Barnard, after whom Barnard’s Star is named, discovered Amalthea in 1892. This was the first Jovian satellite to be discovered after Galileo Galilei’s original four in 1609. Odds are Amalthea’s colors come from sulphur from neighboring Io’s many volcanos.
Phobos is the larger of Mars’s two moons and very dark like Phoebe. For years investigators puzzled over the parallel grooves on Phobos until they realized they were formed by rubble which blasted into orbit during impacts and then spiraled back down over millennia and skittered to a halt in the sand. Phobos itself is losing about 2 cm of altitude per year and will either strike Mars or shatter into a ring in 30 to 80 million years.
Some odd ones
So far, only 21,922 (4%) of the numbered asteroids are named. Currently the highest-numbered named asteroid is 543315 Asmakhammari.The shortest names are 85 Io (not to be confused with the Jovian moon Io), 954 Li, 1714 Sy, 2705 Wu, 3271 Ul, 6498 Ko, 16563 Ob, 22260 Ur, and 366852 Ti. First and last in the phonebook would currently be 20813 Aakashshah, named after a science fair-winning New Jersey medical student; and 22521 ZZ Top. Someone even honored their keypad with 6600 Qwerty.
There’s 13681 Monty Python, as well as 9617 Grahamchapman, 9618 Johncleese, 9619 Terrygilliam, 9620 Ericidle, 9621 Michaelpalin, and 9622 Terryjones. You’ll also find 3834 Zappafrank and 4147 Lennon, 4148 McCartney, 4149 Harrison, and 4150 Starr. 15845 Bambi and 16626 Thumper are named after the Disney characters and 3252 Johnny, 4238 Audrey, and 7707 Yes are named after Johnny Carson, Audrey Hepburn, and the British progressive rock band Yes. There’s no No, but a 2857 NOT, named after the Nordic Optical Telescope.
One of the slowest-rotating asteroids is 288 Glauke which grinds along at one revolution every 50 days. At the other extreme you have asteroid 2014 “Pitbull” RC, spinning over a quarter of a million times faster or once every 15.8 seconds. This was the same body that skimmed over New Zealand on 7 September 2014 with only 39,900 km (24,800 miles) to spare.
More discoveries
The LINEAR project, NEAT, and Spacewatch currently represent the state of the art in the automated search and documentation of asteroids and especially Near-Earth Objects which might pose a threat of impact. These three parties have discovered over 200,000, 28,000, and 11,000 asteroids respectively.
From the latest reports there are 8,190 Jupiter Trojans known and 27 Neptune Trojans. Nothing yet appears to be pacing Saturn but as of this writing at least three objects — 83982 Crantor, 2010 EU65, and 2011 QF99 — have been confirmed for Uranus.

The first Mars Trojan to turn up was 5261 Eureka at the planet’s L5 point (trailing 60 degrees behind). Eight more have been identified there since then and, remarkably, they and Eureka all consist of that same green mineral olivine mentioned above. At least one asteroid, 1999 UJ7, leads Mars at L4. Mars also has at least half a dozen companions that fall short of the Trojan category, called co-orbitals.
The earth has company, too. One of the more interesting so far is 3753 Cruithne (KRIN-ya), originally spotted by UK Schmidt Telescope staff observer Duncan Waldron in 1986 but not fully appreciated until 1997 when Paul Wiegert and Kimmo Innanen at York University in Toronto and Seppo Mikkola at the University of Turku in Finland plotted out its byzantine path. From our perspective it gyrates through what’s called a horseshoe orbit, at times lagging the earth on its way around the sun and at other times racing ahead of it. Some call Cruithne a “second moon” but even at its brightest it’s fainter than Pluto.
By 2014 six more earth co-orbitals had been added to the list as well as a leading (L4) Trojan. At least one of those co-orbitals, 54509 YORP, spins about its axis at an accelerating speed. At the moment YORP makes one rotation about every 5 hours, but into the far distant future that’s expected to increase to around once every 20 seconds — at which point it will fly apart.
Floating treasure
Before our ancestors learned to smelt iron ore, they scavenged the metal from iron-nickel meteorites. These come from asteroids representing about 25% of the inner solar system total. The remainder are stony or intermediate blends of the two, while the Centaurs and others beyond lean more toward ices.5
The mineral resources up for grabs out there are staggering. Jeffrey Kargel of the US Geological Survey in Flagstaff, Arizona estimates even a trifling 1-kilometer-wide metallic asteroid would yield 400,000 metric tons of metal (not just the iron and nickel, but many others including gold and platinum) worth between $500,000,000,000 and $9,000,000,000,000 by 2016 prices.
When it comes to asteroid mining or other gainful cosmic pursuits, distance can be far less important than the change in velocity, delta-V, you need to intercept your target. The minimum ∆V to reach the moon from low earth orbit is 6 km (3.4 miles) per second, but we know of over 600 NEOs even more accessible. So far the very smallest ∆Vs are for a couple of mysterious and possibly artificial6 objects, 2007 UN12 and 1991 VG at 3.8562.396 miles and 3.9982.484 miles kps. Named NEOs with the three smallest are 25143 Itokawa (a bizarre rubble pile the Japanese Hayabusa probe photographed in 2005), 4660 Nereus, and 65803 Didymos at 4.632.877 miles, 4.983.094 miles, and 5.13.2 miles kps. Eros also looks pretty attractive at 6.0693.77 miles kps.
Once upon a time
steroids have long been a staple of speculative fiction.
One of the earliest such references was in the 1898 serial Edison’s Conquest of Mars by Garrett P.
Serviss7.
In the process of hunting down Martians (so much for multiculturalism) a fleet of earthly spaceships encounters an asteroid:
For a moment we were startled beyond expression. The truth had flashed upon us. This must be a golden planet — this little asteroid. If it were not composed internally of gold it could never have made me weigh three times more than I ought to weigh.
“But where is the gold?” cried one.
“Covered up, of course,” said Lord Kelvin. “Buried in star dust. This asteroid could not have continued to travel for millions of years through regions of space strewn with meteoric particles without becoming covered with the inevitable dust and grime of such a journey. We must dig down, and then doubtless we shall find the metal.”
Though seriously wanting for scientific accuracy, a couple of my favorite asteroid tales come from the first season (1959-60) of the anthology TV series The Twilight Zone. The first was Episode 7, The Lonely, written by Rod Serling. Jack Warden stars as Jim Corry, a prisoner sentenced to 40 years of solitary confinement on a thoroughly desolate and dispiriting “Ceres-XIV.” An android in the form of Jean Marsh keeps him company.
Charles Beaumont wrote Episode 20, Elegy. Here, three astronauts crash-land on an asteroid built up like a picturesque country village. All its inhabitants are frozen in place but one, who startles them by introducing himself as caretaker Jeremy Wickwire (Cecil Kellaway). They learn the asteroid is a mausoleum in which the deceased are posed permanently in tableaux celebrating their fondest earthly aspirations. Wickwire plays the gracious host, but in true Zone fashion ultimately slips the trio a mickey and turns them into bio-mannequins. He summarizes, “While there are men, there can be no peace.”
1. Like the songbird it’s FEE-bee; in the the original Greek, PHOY-bee.
2. Though the International Astronomical Union imposes a strict 16-character limit, 4015 Wilson-Harrington was grandfathered as it was previously known as Comet Wilson-Harrington, discovered in 1949 and named after its co-discoverers.
3. The IAU has chosen to designate interstellar asteroids with a capital letter I followed by a numeral indicating the order of discovery, I1 ʻOumuamua being the first. ʻOumuamua (pronounced Oh moo-uh moo-uh) is a Hawaiian term characterizing the object as a messenger or scout.
4. NASA tells us it would love to send a probe to catch up with 'Oumuamua, but its whopping delta-V of 60 km/s is beyond current tech using chemical propulsion.
5. We call these objects comets if they outgas visibly, though the line between asteroids and comets has always been blurry.
6. Spent 70s-era rocket fuel tanks have been suggested, though from the objects' behavior they appear too dense for that.
7. Though now mostly forgotten, Serviss (1851-1929) was an enormously popular astronomy lecturer and authored many books on the subject.
Ceres and Vesta ☆ NASA/JPL;
Hyperion, Phoebe ☆ Cassini-Huygens/NASA;
Amalthea, Ida, Gaspra ☆ Galileo/NASA;
Mathilde, Eros ☆ NEAR - Shoemaker;
Phobos ☆ HiRISE/NASA;
NEAR Shoemaker and Kleopatra simulations, Rabinowitz photo ☆ NASA;
Cruithne orbit animations ☆ Jecowa (CC);
'Oumuamua simulation by the European Southern Observatory (ESO) / M. Kornmesser