New Horizons, to infinity and beyond!
I stumbled across this image while looking up Quaoar. I knew a number of Trans-Neptunian objects have been discovered, but I had never seen them portrayed before. Click on the image to see the full size version, it’s quite detailed. When I grew up the solar system was a pretty simple thing, who knew it would explode into dozens of dwarf planets? All of these are pretty small compared to the Earth, and from where they are the sun is just a very bright star. Will we be colonizing any of these puppies? Not anytime soon I suspect. Still, we should familiarize ourselves with them…one never knows what the future brings.
Eris is the biggest of the lot. It’s the largest dwarf planet known, and the ninth largest object directly orbiting the sun. Not too shabby for something discovered in 2003. In fact its discovery was what prompted the International Astronomical Union to redefine what was and wasn’t a planet. Eris was briefly hailed as the “tenth planet,” alas now it is merely the largest dwarf planet. It has less than ten percent of Earth’s gravity, and it’s got a little more surface area than Russia. A wee bit colder though, around 30-50 degrees kelvin (hundreds of degrees below freezing,) the surface appears to be covered with grey frozen methane. It takes Eris 557 years to orbit the Sun, it’s farther from the Sun than any other known objects except comets. On the plus side, Eris has a cute little moon.
Then there’s 2003 EL61, aka “Santa.” Yes, it’s shaped like an egg, apparently something very bad happened in Santa’s past, like a collision with another dwarf planet. It has about the same surface area as China or the USA. Only one twentieth of the Earth’s gravity though. It appears to have water ice on the surface, and was named Santa because it was discovered just after Christmas 2003. Controversy over who discovered it first is holding up its official name. As cold as Eris of course, but Santa has two large moons, it must be quite beautiful from the surface.
2005 FY9 is also waiting an official name, for now it has been called “Easterbunny” by its discoverer. It’s small, a bit smaller than Australia, but bright. In fact it’s bright enough to be seen with high end amateur telescopes. It looks kinda red, and may even have a brief transitory atmosphere when it is close to the sun. Again, one twentieth of the Earth’s gravity, and too cold to even imagine.
Sedna, Orcus, Quaoar, and Varuna. Well, um, at least they’re named. Sedna is distinguished by having a very long year, it takes Sedna longer than ten thousand years to orbit the Sun. No one knows why, possibly it didn’t even originate with the Sun and was captured from a passing star. Orcus. Well, it’s small and unremarkable, with about the same surface area as Sudan or Argentina. Quaoar has the same surface area as India, and is distinguished by being the first trans-Neptunian object to be measured using the Hubble Space Telescope. It’s pronounced: ˈkwɑːwɑr. Lastly we have Varuna, about the same surface area as Greenland. It’s spinning very fast (its day is about three hours) and because of that it’s probably more egg shaped than spherical.
Lastly we have the fun one, the redoubtable former planet Pluto and its huge moon Charon. Pluto has about the same surface area as Russia, and gravity about one twentieth Earth normal. The surface temperature can get to a balmy 55 degrees Kelvin. It’s apparently rocky and covered with nitrogen ice. Pluto’s moon Charon isn’t huge in an absolute sense, it’s just huge compared to Pluto. No other planet has a moon so large compared to itself, some astronomers consider Pluto and Charon to be a “double planet” rather than a planet and a moon. Well, I guess that would be double dwarf planet. Charon has more surface area than India. It wasn’t even discovered until 1978. Charon has less rock that Pluto, is covered with water ice…and probably even has active cryovolcanoes. It must be a spectacular sight from the surface of Pluto.
The best thing about Pluto and Charon is that a probe is on the way. The New Horizons probe has passed Jupiter and will arrive at Pluto in 2015. NASA helpfully has a countdown to the flyby date on their web site, how cool is that? Aside from the usual instruments…the probe carries some artifacts like a Florida quarter and some of the ashes of Clyde Tombaugh, the man who discovered Pluto. Unfortunately, New Horizons won’t be stopping at Pluto, this is a flyby mission. It will pass about 6200 km (10,000 miles) from Pluto and then pass Charon at about 27,000 km (16,800 miles.) Basically it has to go so fast to get to Pluto/Sharon in decent time that there’s no good way to slow it down. A shame, but still, it will be the first visit to these objects and it will be taking pictures and other measurements furiously in the weeks before and after the flyby. At closest approach features as small as 50 m will be visible, it ain’t going to be Google Pluto but its still amazing.
And of course the best is for last. After it passes Pluto New Horizons is going to continue on to the Kuiper belt and with any luck it will flyby another dwarf planet or Kuiper Belt Object. Where the luck part comes in is that they actually haven’t discovered a Kuiper Belt Object that is within range of New Horizon’s manoeuvre capabilities. There’s a lot of them out there waiting to be discovered, and astronomers are definitely looking. I just love the way scientists wring every last bit of use out of each probe these days. New Horizons took some excellent measurements and pictures of Jupiter when it flew by it for example, and it they do find a Kuiper Belt object it can visit, that’s just icing on the cake.
(The above image is published legally in accordance with its license: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License“. I was writing this post late into the night and had all sorts of weird nightmarish dreams about taking a space ship to Pluto, another price I pay to blog I suppose.)