Is Pluto Colder Than Hell?

[mikeemmert]

They have discovered that Pluto is even colder than they thought it was:<br /><br />http://www.space.com/scienceastronomy/060103_pluto_cold.html<br /><br />From the article:<br /><br /><font color="yellow">"Earth-bound astronomers taking Pluto's temperature have confirmed suspicions that the planet is colder than it should be. It's thought that the planet’s lower temperature is the result of interactions between its icy surface and thin nitrogen atmosphere.<br /><br />Using the Submillimeter Array, or SMA, a network of radio telescopes located in Hawaii, astronomers found that Pluto’s average surface temperature was about 43 K (-382 degrees F) instead of the expected 53 K (-364 degrees F), which is what the temperature of Pluto’s largest moon, Charon, is. "<font color="white"><br /><br />I'm quite glad to see a new heat-sensitive telescope being brought to bear on this subject. I have some suspicions that albedos of the Kuiper belt objects haven't been accurately determined. This entails measuring heat emissions.<br /><br />If New Horizons makes it off the ground in time, maybe one task it could be put to as it flies by Jupiter is calibrating these instruments (SMA and Spitzer, amongst others). Does anybody know of any other spacecraft that can be used for such calibrations? Hayabusa, for instance?<br /><br /></font></font>

 

[spayss]

"Earth-bound astronomers taking Pluto's temperature have confirmed suspicions that the planet is colder than it should be."<br /><br />Just to nitpick. <br /><br /> That's poorly worded science. Pluto is exactly the temperature it should be because of the physics involved. The previous assessment of astronomers was wrong.

 

[formulaterp]

<font color="yellow">If New Horizons makes it off the ground in time, maybe one task it could be put to as it flies by Jupiter is calibrating these instruments (SMA and Spitzer, amongst others). Does anybody know of any other spacecraft that can be used for such calibrations? Hayabusa, for instance? </font><br /><br />I assume you mean by comparing albedo calculations from NH and earth based scopes? If so, could they not do that with Gallileo or Cassini data?

 

[bonzelite]

yes. politically-correct, face-saving headlines like that are common. it is often phrased like "astronomers shocked at star system that should not be there..." <br /><br />"super planet discovered that should not exist..."<br /><br />but it is all what it should be --prior estimates, guesses, or observations were either inconclusive, inaccurate, or wrong. it's very simple to understand that. <br /><br />they're discovering newer and more amazing things about Pluto, and we're yet at least 10 years away from actually arriving there.

 

[mikeemmert]

Gallileo was deliberately crashed. Some archived data may be useful, but calibrations are more accurate if the observations are done at the same time. One reason is albedo variations across the surface of an object; Pluto's albedo varies from 0.49 to 0.66 (yes, that's a lot of variation, more than most objects). Then there are delayed effects such as evaporation, postulated for the lower temperatures on Pluto and quite a problem for comet measurements.<br /><br />Cassini is definitely a good possibility. Phoebe would have made a good target for that. But Iapetus would make a poor one, unless the observations were done simultaneously. Enceladus is subject to thermal inertia and worse, outgassing that is probably tidal and not solar for it's energy source.<br /><br />Mostly what you want is IR radiation measurements free from the background of the Earth's atmosphere or of dust in the intervening distance between the target object and the probe on the one hand, and the instrument (SMA or ALMA or Spitzer) on the other.<br /><br />I don't know the technological state of Cassini's infrared equipment. I do know that infrared detectors have improved over the years and that Cassini is fairly old.<br /><br />Another problem is that Cassini is in the Saturn system, where there are probably a lot of particles floating around. These will have their own signature, degrading the signal to noise ratio. Hayabusa might be better on that account.<br /><br />Gegenschien, the asteroid belt, and interstellar dust make infrared astronomy a tricky business.

 

[Philotas]

Lets not hope this means that Plutos atmosphere will have froze out by the time New Horizons reaches it. One of the arguments for getting NH launched as soon as possible was just about that. <div class="Discussion_UserSignature"> </div>

 

[mikeemmert]

No, if you read the link, it means Pluto is still evaporating. That's what's cooling it down.

 

[Philotas]

I read stright past it. <img src="/images/icons/blush.gif" /> <br /><br />I thought Pluto was moving farther away from the Sun and thus should be freezing; but it`s melting, and cooling itself in the process. Sounds like a paradox. <div class="Discussion_UserSignature"> </div>

 

[mikeemmert]

Thermal inertia. Rarely is Dec. 22 the coldest day, nor is June 22 the hottest. Hottest time of the day is 3:00 to 5:00.<br /><br />Y'know, this factor is going to cause big problems measuring albedos of objects with eccentric orbits using the infrared flux. Apparently they keep heating up past perihelion. The best idea is probably to start with KBO's with the most circular orbits. Buffy?<br /><br />Sheeeeeeshhhhh.........it keeps getting more complicated!