Seriously, when did this happen? And where was I? Did I leave the room for five minutes to use the bathroom or something and everyone was like “quick, let’s completely change the solar system!”
Okay, to be fair we didn’t completely restructure the solar system. It’s really just everything beyond Neptune.
Everyone remembers a few years back when Pluto stopped being a planet, right? Well, I don’t know about you, but I never got a satisfactory explanation for why that happened. People (and by people, I mostly mean news outlets) were just like “they decided it was too small, so now it’s a dwarf planet.” End of story.
That’s not what happened, guys.
What really happened was that back in 2005, a Palomar Observatory based team lead by astronomer Mike Brown, discovered Eris, an object roughly three times the size of Pluto (they thought at the time) orbiting our sun at approximately 1.442×1010 km out. (That is a very approximate distance, since Eris, like Pluto, has an eccentric orbit. Did you know that Pluto’s eccentric orbit sometimes brings it closer to the sun then Neptune? True fact.)
This was not the first large body we had discovered beyond the orbit of Pluto. The first, Chiron, was found in 1977. But it was the size of Eris that made people sit up and take note. That was when they decided that maybe it was time to actually define what a “planet” was, since that had never been done.
So in 2006, the International Astronomical Union finally sat down and decided what it takes to be a planet. And Pluto didn’t make the cut.
If that upsets you because you want your childhood image of the solar system to remain intact, think of it this way: if Pluto had remained a planet, then Eris would have to be considered one as well, so no matter what you were going to have to come up with some new mnemonics.
And seriously, there may well be over a hundred or more objects that fit the parameters of a dwarf planet out in the Kuiper belt. Some estimates place the number closer to two hundred.
In light of this new information, I formally redact all previous criticisms I made of the decision to de-planetize Pluto. I get it now, we can’t make all the poor elementary school children memorize over a hundred planet names. Good call, IAU!
Of course, currently the IAU only officially recognizes the existence five dwarf planets. We know there are more then that, but until we can pin down some of the details about the others, the IAU can’t formally recognize them. This is because we just can’t be sure how big these objects really are. Or how many of them there are, or where exactly they are, or what their orbits look like, etc. These things are just so freaking far away, measuring anything way out there is really, really hard.
For example, you remember when I said that at the time of its discovery they thought Eris was three times the size of Pluto? Well, new estimates are that it’s actually pretty close to Pluto in size, maybe just a bit bigger. It’s hard to tell in part because Pluto’s atmosphere makes measuring its true size extremely tricky.
Wait. Stop. Hold the phone. What was that?
Guys, Pluto has an atmosphere. And five moons, at least two of which are just big wobbly potatoes.
Seriously, I had no idea how little I knew about everything beyond Neptune. (The technical term is Trans-Neptunian Objects) And more to the point, I had no idea how little astronomers knew about these objects. I guess I thought we had pretty much figured out how to get reliable data about anything within our solar system. Boy was I wrong.
But good news! We won’t be in the dark for long, at least not as far as Pluto is concerned. This July, 2015, the New Horizons space probe will be doing a flyby of the dwarf planet.
Launched in 2006 (shortly before Pluto stopped being a planet), New Horizons’ mission is to gather information about Pluto and it’s primary moon Charon, and hopefully to continue on to explore additional objects in the Kuiper belt.
How cool is that? I mean, it’s taken nine years to get the probe out there, but soon we will get actual information about Pluto. Information that is impossible to gather from Earth, like figuring out what Pluto’s atmosphere is made of, and measuring its surface temperature, stuff like that.
And I think that is really really cool. I’m super glad I didn’t know about New Horizons until now, because I would have spent the last nine years being impatient to know what it would find out. But now I only have to wait a little more then a month. Plus however long it takes NASA to receive, translate and interpret the data, I suppose. But how long could that take? ::clings desperately to her optimistic naivety::
Don’t tell me, it’s as bad as knowing when the next season of Dr. Who is actually coming out. Some things are easier to wait for when you don’t know how long you will be waiting.