2008 EB61
Published on Mar 14, 2008 at 10:47 pm.
2 Comments.
Filed under asteroids.
Images were taken last Sunday of a spot near the western edge of the constellation Virgo. In these images were stars galaxies. But, there were some other things there, too. Astronomy students studying those images observed several dots that were in slightly different positions in the different images. Those dots were asteroids, what astronomers call “minor planets.” One of those moving dots, though, did not correspond to any known asteroid. Monday, it was confirmed that the dot was actually a hitherto unknown asteroid. Soon, it was given an official provisional designation of 2008 EB61. The discovery images are shown below. Click on them to see a larger version, with the new asteroid marked.
Only a few observations of this asteroid have been made, and no spectroscopic data is available, yet. So, I don’t know the composition or albedo (brightness) of the object. Assuming that it is pretty average for an asteroid, then its brightness seems to indicate that it is probably about 1.5 to 2 miles across. It is located in the outer portion of the asteroid belt. In fact, it is very near the 1:2 Kirkwood Gap. That is a place near the outer edge of the main asteroid belt where asteroids orbit the Sun exactly twice as quickly as Jupiter. That means that Jupiter nudges the asteroids every two orbits in the same spot in the asteroid’s orbit. When that happens over a long enough time, the asteroids orbit becomes somewhat chaotic. Its eccentricity begins to change drastically, with the orbit sometimes becoming eccentric enough to range in distance from the asteroid belt to perhaps even closer to the Sun than the Earth. Such an orbit could, over a long enough time, threaten to intersect the orbits of one of the other planets. Now, this doesn’t mean that 2008 EB61 is an imminent threat to Earth. In fact, it may be that this asteroid might never have an orbit that intersects Earth’s orbit. Of course, being near the Kirkwood Gap is not the same as being in the gap. But, as I have mentioned in an earlier post, asteroid orbits can move around some. So, there is no guarantee that the asteroid will stay out of the Kirkwood Gap forever.
The orbit is fairly circular, for an asteroid, having an eccentricity of only about 0.05. That is a little more elliptical than Earth’s orbit. Most asteroids have a bit more elliptical orbit (the bigger the eccentricity, the more elliptical the orbit is). The orbit is a bit tilted with respect to the orbits of Earth and the rest of the planets. The orbit of 2008 EB61 has an inclination of about 8 degrees, as seen in the orbit diagram below.
JPL’s Small Body Database Browser has a page where you can look at the orbit of 2008 EB61 from several directions. That is where I got these orbit diagrams. Now, I should point out that the calculated orbit might not be exact. After all, there are only a few observations of the asteroid. So, there is some uncertainty in its orbit. That’s to be expected, after all, because it was only discovered less than a week ago.
Oh, and I should also congratulate the students, Ryan and Robbyn, who discovered the asteroid. They are students working with me!
-Astroprof
Oomi on March 18, 2008 at 7:52 am: 1
Congratulations!
Rubaru on March 20, 2008 at 12:06 pm: 2
Dear AstroProf –
Congrats to Robbyn and Ryan on this discovery. It puts them into an special category of people. And with you being their mentor, well…that’s cool too!