Thursday, January 25, 2007

Streaking Past Jupiter

Equipped with his five senses, man explores the universe around him and calls the adventure Science. ~Edwin Powell Hubble

When everyone was going crazy about devaluing Pluto (about which I wrote at length, culminating here), one of the very stupid thoughts to be floated was that, if Pluto was no longer considered a planet, should the New Horizons project be scrapped?

New Horizons was, and is, a satellite on its way to investigate what we used to call the ninth planet (or the eighth planet, when it came inside the orbit of Neptune). By the time the debate had reached it's height, with the IAU's decision to reduce Pluto to a dwarfy, icy, Kuiper-Beltish sort of thing, New Horizons was streaking through the inner Solar System like the proverbial bat out of hell, heading for a 2015 rendezvous with Pluto, Charon, two other little moons and whatever else might be out there.

So, what did the nay-sayers want to do, call it back?

Fortunately, no one paid much attention to the non-debate concerning whether Pluto's demotion somehow denigrated the nature of the New Horizons probe. In fact, the probe's rapid progress has it in a position to start sending some science back, not about Pluto, but about Jupiter.

It is hard to grasp sometimes just how fast this satellite is moving. To put it into perspective, New Horizons launched January 19, 2006. It will make its closest approach to Jupiter on February 28 – of this year! Now if you aren't amazed by that, consider that Galileo, the little satellite that could, took six years to make the trip, needing two or three gravity boosts in the process. To put it simply, New Horizons is the fastest thing we've ever launched into space – or anywhere else for that matter.

Fast as it is, New Horizons is using Jupiter to give it a further speed boost, because its still a long, long way to Pluto. Despite taking 1/6 the time to get to the Jovian system that Galileo did, it will take another eight years to get to the depths of space where Pluto lurks. Pluto is awaaaaay out there.

All this speed was accomplished by making the satellite as compact (about the size of a piano, as opposed to Cassini, which was a bus) as possible and putting it on a large rocket. There is a trade off for traveling at this incredible rate; you can't slow down. To put enough fuel and a big enough engine on New Horizons to enable it to slow down and possibly orbit the Pluto system would have made it so heavy that it would have taken many more years to get where it was going. Even a light-weight ion engine would have required so much deceleration time, that nothing would be gained by using the constant acceleration afforded (assuming that we had sufficient experience with ion engines; so far, Deep Space One is the only usage and, while it worked, it was a bit finicky in its behavior).

The Jupiter encounter gives the New Horizons team a chance to test out systems, gather some science, and conduct a dress-rehearsal of what an incredibly high speed flyby is like. Already, early pictures are showing changes in the great Red Spot of Jupiter since Cassini took its flyby pictures. There will be pictures of Io's current volcanic state, which should prove interesting as Io seems to be the most dynamic place in the Solar System short of the Sun.

But one of the most interesting aspects of this pass is that New Horizons will plunge through Jupiter's “tail”. Like any planet with a magnetic field, the solar wind blows Jupiter's magnetosphere back away from the planet into a comet sort of shape. In fact, New Horizons' path will take it the length of that “cometary tail” which will give tremendous amounts of data on the extent and strength of Jupiter's magnetic field and on the solar wind's effects.

Principle investigator Alan Stern is, as one might expect, very excited, but he also has something on his mind. After years of working to get NASA to send a probe to Pluto, he was saddened to see the old ice-ball get demoted to whatever it got demoted to.

Okay, okay, it's a dwarf planet, but I think the IAU's approach and definition is dumb, as I've said at length before.

At any rate, Mr. Stern is not giving up, using this flyby, and any other opportunity to get Pluto back to planethood. Well, that's all well and good, but I think he's going to be disappointed. Once New Horizons gets out to the Kuiper Belt, it will give us, hopefully, a good look at Pluto and quite probably a look at some other ice balls floating around in the neighborhood. It's quite possible that Pluto will be found to be much closer kin to a comet than to anything we would normally recognize as a planet.

Knowing what Pluto and other Kuiper Belt objects are like will give us important clues about the formation of the solar system. If Pluto's status as a non-planet is confirmed as a result, that wouldn't be so awful.

Besides, “building block of the solar system” isn't a bad thing to be called.

Pluto probe begins close-up study of Jupiter

NASA's Pluto Probe Prepares for Jupiter Flyby

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