Things are getting a little stranger in the asteroid belt these days! Objects in this zone of the solar system are known to be rocky bodies, though in the past few years several of these bodies have had cometary features detected. One such body is 596 Scheila, which has always been confidently called a main-belt asteroid, meaning it is a rocky body orbiting nicely between Mars and Jupiter causing no trouble to Earth.
Scheila is 113 km in diameter and was discovered in 1906 by August Kopff in Heidelberg and named after an acquaintance of the discoverer. For the past 104 years Scheila has been pleasantly orbiting without much fuss until last week the Catelina Sky Survey found a coma around the object with a 0.68 meter Schmidt telescope; quickly confirmed by many other observers.Scheila, along with several other bodies in the past few years, have created a new class of solar system objects: main-belt comets. Main-belt comets have the orbital characteristics of main-belt asteroids, but exhibit an outgassing, comae, or a dust-tail that is normally seen on icy comets that came from the outer-reaches of our solar system. These bodies are an anomaly and a mystery since an object this close to the sun should have had its ices vaporized away. This has caused another theory to arise that perhaps they are not icy bodies, but perhaps the trail of debris was caused by an asteroid-asteroid collision.
3200 Phaethon, the parent body of the famous Geminid meteor shower, is another example of this. Phaethon was always thought to be an asteroid, a purely rocky body, and even its meteoroids agreed with this, being denser than an average icy-meteoroid. But in recent times Phaethon has exhibited dust-outgassing, causing observers to wonder whether it once was a comet, or if it has had a recently collision to cause the particles.
Unlike Phaethon, Scheila will not intersect Earth’s orbit and thus we will not have a Scheilid meteor shower. Whether this outgassing and dust production from asteroids is due to vaporization of earth or asteroid collisions, only time will tell. Oh, the mysteries of our solar system!
Orbit of 596 Scheila, as computed by the JPL small-body database browser.
Image of 596 Scheila using a V Filter and 10 stacked images of three-minute exposures each.
Image of 596 Scheila using an R Filter and 10 stacked images of three- minute exposures each.
Images were taken via a remote-operated camera located in New Mexico. Stars are trailed because the asteroid was being tracked. You can clearly see the fuzzy “cloud” or coma about the asteroid in the center.
Images courtesy of Bill Cooke and Rhiannon Blaauw, NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala.
The animation below shows the motion of Comet Ikeya-Murakami on Nov. 13, 2010, captured with a New Mexico-based telescope operated remotely by NASA’s Marshall Space Flight Center. The images were taken near dawn and show the comet’s movement over a period of 45 minutes. Each exposure was three minutes in length, and the faint angled streak around 0:10 in the animation is a satellite trail. At the time of these images, the comet was some 229 million miles away from Earth.
Comet Ikeya-Murakami was discovered very recently on Nov. 3, 2010, by Japanese amateur astronomers Kaoru Ikeya and Shigeki Murakami. Their discovery is unusual because they both used manual observations through optical telescopes to identify the comet. Such observations are rare in recent times when astronomers use cutting-edge digital imaging to study the skies.
Ikeya-Murakami is classified as a long-period comet, or those comets having eccentric orbits ranging from 200 years millions of years to make one circuit around the sun.
Courtesy of Rob Suggs, NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala.
MSFC astronomer Bill Cooke took this five-minute exposure of Comet Hartley 2 late on the night of Saturday, Oct. 16, 2010, using a 10″ telescope in New Mexico.
The comet, which has now reached naked eye visibility, was just under 11.5 million miles from Earth and sporting a coma over a degree across — twice the size of the full moon. You can read more about the “coma” and other parts of a comet at the NASA Worldbook: Comets page.
This very active visitor to our neighborhood makes its closest approach around 8 a.m. EDT on Oct. 20, at a distance of 11.2 million miles. Unfortunately, the light from the nearly full moon will tend to wash out the comet’s pale green glow, so comet watchers are advised to make use of a pair of binoculars for the best view.
Image courtesy of Bill Cooke, NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala.
It’s a strange-sounding name for a constellation, coming from the Greco-Roman word for giraffe, or “camel leopard”. The October Camelopardalids are a collection of faint stars that have no mythology associated with them — in fact, they didn’t begin to appear on star charts until the 17th century.
Even experienced amateur astronomers are hard-pressed to find the constellation in the night sky. But in early October, it comes to prominence in the minds of meteor scientists as they wrestle with the mystery of this shower of meteors, which appears to radiate from the giraffe’s innards.
The October Camelopardalids are not terribly spectacular, with only a handful of bright meteors seen on the night of Oct. 5. It may have been first noticed back in 1902, but definite confirmation had to wait until Oct. 2005, when meteor cameras videotaped 12 meteors belonging to the shower. Moving at a speed of 105,000 miles per hour, Camelopardalids ablate, or burn up, somewhere around 61 miles altitude, according to observations from the NASA allsky meteor cameras on the night of Oct. 5, 2010.
So they aren’t spectacular. Their speed is calculated. Their “burn up” altitudes and orbits are known. So what’s the mystery?
Camelopardalids have orbits, which indicates that they come from a long period comet, like Halley’s Comet. But the Camelopardalids don’t come from Halley, nor from any of the other comets that have been discovered. Hence the mystery: somewhere out there is — or was — a comet that passes close to Earth which has eluded detection. These tiny, millimeter size bits of ice leaving pale streaks of light in the heavens are our only clues about a comet of a mile, maybe more, in diameter.
This is why astronomers keep looking at the Camelopardalids meteors. They hope that measuring more orbits may eventually help determine the orbit of the comet, enabling us to finally locate and track this shadowy visitor to Earth’s neighborhood.
The skies were clear over New Mexico last night — Oct. 6, 2010 — so Rhiannon Blaauw of NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala., captured this image of Comet Hartley 2 at a distance of “only” about 14 million miles from Earth.
Hartley 2 has passed out of the constellation Cassiopeia and is now traveling through the constellation Perseus. On October 20th, the comet will come within 11 million miles of Earth. Since comets rarely come this close, it will be faintly visible to the naked eye in the early morning sky. The comet has an orbital period — or time to travel once around the sun — of approximately 6.5 years.
For those interested in astronomy photography, the image was taken with a single shot color filter with 300-second exposure via a remote-operated telescope located in Mayhill, N.M.
We’re tracking Hartley 2’s journey as it approaches Earth, so stay tuned for more photos!
Image courtesy of Rhiannon Blaauw, NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala.
In this image taken on the evening of Friday, Oct. 1, Comet Hartley 2 can be seen in the constellation Cassiopeia (north-east sky, not far from horizon).
Hartley 2 will only be in Cassiopeia for a few more day before traveling through the constellation Perseus. It’s a Jupiter Family Comet that we can’t see right now because it’s too tiny at approximately 1.2 km across. In this image, the comet was still 16,500,000 miles from Earth.
On October 20th, Hartley 2 will will come within 11 million miles of Earth, and since comets rarely come this close, it will be visible to the naked eye in the early morning sky. The comet has an orbital period, or time to travel once around the sun, of approximately 6.5 years.
For those interested in astronomy photography, the image was taken with a single shot color filter with 300-second exposure. It was captured by Rhiannon Blaauw of NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala., via a remote-operated telescope in Mayhill, N.M.
We’ll be keeping an eye on Hartley 2 as it approaches Earth, so stay tuned for more photos!
Images courtesy of Rhiannon Blaauw, NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala.
A pale green interloper among the stars of Cassiopeia, Comet Hartley 2 shines in this four-minute exposure taken on the night of Sept. 28, 2010, by NASA astronomer Bill Cooke:
Still too faint to be seen with the unaided eye, the comet was 18 million miles away from Earth at the time. Cooke took this image using a telescope located near Mayhill, N.M., which he controlled via the Internet from his home computer in Huntsville, Ala.
Comet-watching from the comfort of your living room! Modern astronomy is truly amazing…
More About Comet 103P/Hartley 2
Comet 103P/Hartley 2, a small periodic comet, was discovered in 1986 by Malcolm Hartley, an Australian astronomer. It orbits the sun about every 6.5 years, and on Oct. 20, the comet will make its closest approach to Earth since its discovery. In this case, “close” means 11 million miles, or 17.7 million kilometers. A moonless sky will make for promising viewing conditions in the northeastern skies, especially just before dawn.
Comet Hartley 2’s nuclear diameter is estimated at 0.75-0.99 of one mile — 1.2-1.6 kilometers — and it’s believed to have enough mass to make approximately 100 more apparitions, or appearances, near Earth. The 2010 appearance also marks one of the closest approaches of any comet in the last few centuries.
Images courtesy of Bill Cooke, NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala.