Note added August 9, 2005: This entry was part of the Tangled Bank carnival of science blogs at Creek Running North.
In my last blog entry I showed a picture of what I thought was one of the two (now three, actually) objects recently discovered lurking in the outer solar system. We observed it using GORT, a telescope my group built to look for galaxies and such.
Well, Logan and I observed the field again on Saturday, a day after the first observations, and — lo and behold — one of the "stars" had moved! And it was the very one I figured must be 2003 EL61, the 70%-of-Pluto-sized iceball orbiting the Sun at 50 AU, 50 times the Earth-Sun distance, or roughly 7.5 billion kilometers (4.5 billion miles) out. Here are the two images, side-by-side:
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| Image of EL61 from July 29, 2005 |
Image of EL61 from July 30, 2005 |
As Galileo said, “And yet, it moves.” You can see how far the dinky little thing moved in a single day. Pretty cool. By the way, as before, I didn’t do the best job processing the images, so there are still leftover bits and pieces of things in the images. EL61 is marked in both.
Take a look at that image. That object orbits the Sun, so slowly it takes 375 or so years to complete one circuit. The surface temperature is something like -400 Fahrenheit. The surface itself is probably frozen nitrogen, oxygen, and methane, colored a dirty dark red from organic compounds made by the interaction of feeble UV light from the distant Sun with those simple chemicals. It has a moon, which circles it once every 49 days. And even then, it’s not all that strange– there are probably millions of objects out there just as icy, just as dark, and just as lonely. There are a lot of worlds in this solar system of ours, a lot of territory to discover and explore.
August 1st, 2005 at 9:43 pm
So what’s your opinion, Phil? Is it a planet or not? What will the International Astronomers group decide? This is so cool. What a great time to be alive. It must have been just as exciting for guys like Galileo and Keppler, et al, when they made their astonishing discoveries. Just think how long it took for them to notify the scientific community in those days, not to mention convince the general public of new concepts those discoveries inferred. Now we know things in a matter of hours or days. Too much!
August 1st, 2005 at 11:58 pm
“we know things in a matter of hours or days” — sort of. Thanks to the Web of a Million Lies, we can get information within hours or days after it’s officially released, but the time between discovery, confirmation, and publication is still on the order of months to years, especially in astronomy. Who wants to be remembered as the follow-up act to Pons and Fleischmann? (Thus sayeth the layman.)
Even with the historically unprecedented access to scientific data and information, I still can’t seem to find a concise listing of the TNOs, Plutinos, cubewanos, whateveros that are popping up like summertime weeds. I’ve heard of Quaoar, and Sedna, and Orcus, and DW 200?, and, and…. Anyone with a good page that has all these beasties?
August 2nd, 2005 at 2:27 am
Wow, it really moves! If only such a short timespan could provide a good orbit estimation.
Richard Board,
Nature website has an article about the future definition of planethood.
http://www.nature.com/news/2005/050801/full/050801-2.html
The discovery of 2003 UB313 have forced the IAU committee to hurry, and “[...] a definition should be ready by the end of the week.”
Phil Brady,
* Minor Planet Center lists all the unusual (i.e. non-Main Belt asteroids) here: http://cfa-www.harvard.edu/iau/lists/MPLists.html
* David Jewitt (one of the discoverers of the first Kuiper Belt object) has a good Kuiper Belt website: http://www.ifa.hawaii.edu/~jewitt/kb.html
* And of course, you can always try Wikipedia: http://en.wikipedia.org/wiki/Kuiper_belt (that page includes links to all the largest trans-Neptunian objects)
August 2nd, 2005 at 5:33 am
I wonder, is it possible to image the far away one, UB313 I believe, with your telescope??
It’s just fun to be able to image big chunks far away…
August 2nd, 2005 at 9:49 am
Actually, Michelle, it is. It’s about 1/2 as bright as EL61, so we’re going to go for it eventually. UB313 isn’t up until early in the morning, and our ’scope isn’t fully automated yet– no one (including me!) wants to stay up that late just to get some pictures. Plus the ’scope primary use is for other objects, so while I’ve been able to get an hour on it to do this, the main stuff takes precedence.
August 2nd, 2005 at 10:23 am
This has surely been an exciting few days. Thanks for the pictures!
I think UB313 should be called a planet if it indeed is bigger than Pluto and also travels closer to the sun occasionally.
August 2nd, 2005 at 10:27 am
Spoken like a true skeptic. I see why you like reality the way it is.
August 2nd, 2005 at 11:50 am
Hmmmm…..that Nature article was interesting, but I have a different idea.
The new objects seem to be slightly blurring the line between planets and KBOs. Not only is one larger than pluto, but one also has its own moon very much along the lines of Charon.
When is the IAU going to realize that existing definitions of “Planet” are totally arbitrary, beurocratic designations?
There are already three different classes of planet in our solar system. There are the inner “terrestrial” planets, the big gas giants Jupiter and Saturn, and the two smaller “icy” gas giants, Uranus and Neptune.
When pluto was discovered, the Kuiper Belt as a whole hadn’t been. So, without truly understanding it, they classified it as a “planet”. Now, after the discoveries of objects like Quaoar and Sedna, the KBOs like Pluto are getting a new designation because of their distance and orbital eccentricities/inclines.
But with these truly large worlds, some with moons, are we simply going to have to create a whole new class of planet? What if we were to discover something slightly larger than 2003 UB313 a little bit futher out? What if the orbit was also inclined, which would explain why it hadn’t been discovered yet, but also less eccentric? What if it had an orbit around the same, or slightly less, eccentricity than Pluto? How would we classify it?
Is it maybe time to designate a new classification of “Kuiper Planets”?
August 2nd, 2005 at 1:39 pm
We really need more complex classification system than the current simple major planet/minor planet system.
Although it doesn’t really matter what they are called — every classification is more or less arbitrary, and every object is unique in its own way — it is good to have astronomical objects classified anyway; for example, if someone says you that an object is a plutino, and you know what ‘plutino’ means, you immediately understand that it is like Pluto a Kuiper Belt object in 2:3 orbital resonance with Neptune.
August 6th, 2005 at 5:48 am
If there is indeed a 10th planet, does this mean my horoscopes were incorrect ?
August 15th, 2005 at 8:37 am
Yes, it looks like UB313 and Pluto are unusually large for TNOs and unusually
small for “regular” planets. Pluto at least has been “grandfathered” in as
a planet for nigh on 70 years now. So that probably qualifies UB313, too.
September 26th, 2005 at 10:56 am
I love this debate! When they started discovering larger and larger KBOs, I knew it would bring the discussion of what is really a planet – especially Pluto’s status – to a head. We’ve dodged the question for too long. Now everyone is talking. It is lively and entertaining, and will probably be one of the better remembered parts of early 21st century astronomy. Personally, I have always gone with the conclusion that any object orbiting the sun with enough gravity to pull itself into a sphere should be considered. Since a number of asteroids fit that definition, it would probably not fly with the general public. “Guess what Mrs. Teacher, this year you can teach the 3rd grade that we have 23 planets!â€? That leaves us with historical planets and picking arbitrary sizes. Pluto is a “historical” planet, and would be next to impossible to dethrone after 75 years. My suggestion: go with the class mentioned above called “Kuiper Planets” to go along with the Terrestrial Planets and Gas Giants. Pluto, and anyhing bigger, would be a member of this class. It is very arbitrary, but draws the line based on 75 years of tradition. If too many are discovered, we can revisit the definition later. After all, Ceres was first called a planet.