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Keck AO photo of Pluto system, Sharper than Hubble!
elakdawalla
post Oct 12 2007, 03:38 PM
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University of Hawaii Astronomer Takes Sharpest Picture of Pluto System

"Almost 30 years after the discovery of Pluto's large moon, Charon, a University of Hawaii astronomer [David Tholen] has used a ground-based telescope to take an image of the Pluto system that exceeds the sharpness possible with the Hubble Space Telescope..." ohmy.gif

And still at least 6 years until spaceborne telescopes will do better than groundbased adaptive optics systems...wonder if JWST (due to launch in 2013) or New Horizons (approaching Pluto in 2015) will get there first?

--Emily


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nprev
post Oct 12 2007, 04:13 PM
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Oh, man...that is just distilled & purified cool...thanks, Emily! smile.gif Gotta love Pluto's 122 deg axial tilt...


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stevesliva
post Oct 12 2007, 05:01 PM
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Sharper... but better? I recall some albedo mapping done by Hubble...
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PDP8E
post Oct 12 2007, 05:39 PM
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Here is the Hubble/Pluto pix
I wonder if we will be able to match this up when Pluto-Express returns ground truth?

Cheers
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ugordan
post Oct 12 2007, 05:45 PM
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Pluto-Express? rolleyes.gif


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elakdawalla
post Oct 12 2007, 05:53 PM
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Those Hubble albedo maps are models, based upon many observed mutual occultations of Charon and Pluto. Charon crosses a bit of Pluto -- takes out a bit of Pluto's light -- then next time it crosses on a slightly different chord -- takes out a different bit of Pluto's light -- watch enough of those and you can get a very low-resolution sense of where there may be big bright spots and big dark spots on Pluto and also Charon. I don't think any of these images actually resolve surface features on Pluto. Just remember how few pixels Hubble gets on Ceres -- then extrapolate that to Pluto's distance.

--Emily


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PDP8E
post Oct 12 2007, 05:54 PM
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Oh Yeah...New Horizons...
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Alan Stern
post Oct 12 2007, 06:10 PM
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QUOTE (elakdawalla @ Oct 12 2007, 05:53 PM) *
Those Hubble albedo maps are models, based upon many observed mutual occultations of Charon and Pluto. Charon crosses a bit of Pluto -- takes out a bit of Pluto's light -- then next time it crosses on a slightly different chord -- takes out a different bit of Pluto's light -- watch enough of those and you can get a very low-resolution sense of where there may be big bright spots and big dark spots on Pluto and also Charon. I don't think any of these images actually resolve surface features on Pluto. Just remember how few pixels Hubble gets on Ceres -- then extrapolate that to Pluto's distance.

--Emily



Emily- The HST images definitely resolved Pluto. See the original AJ paper or the press releases. In the image above the inset is the *actual* image: see the polar caps and other spots?

Alan
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elakdawalla
post Oct 12 2007, 07:02 PM
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Oops -- sorry! I must have been thinking of something else...

--Emily


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tedstryk
post Oct 12 2007, 07:07 PM
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Here is one of the actual views from the FOC set that has been posted a lot (and no, I didn't do anything to it).



Additionally, here is the more recent map, in color, from Hubble's ACS HRC (images taken in 2002-2003)



To call the new Keck images, at least from what has been released, "better than Hubble" is a stretch.

This view, also in color, is one produced in from the 1980s mutual event data (the data that Emily was thinking about) by the team of Young, Crane, and Binzel.



This set, by Marc Buie and others (I believe Alan Stern was also involved), is also based on the mutual events. Note that because of the fact that Charon stays over the same hemisphere, only one side of Pluto and one side of Charon could be mapped. The other sides were approximated using light-curve data. The mutual-event derived data on Pluto can be seen on the left, the mutual event derived data on Charon can seen on the right.



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Guest_PhilCo126_*
post Oct 12 2007, 07:28 PM
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Guests






The never-ending discussion, (very or overwhelmingly) large ground based telescopes or space based telescopes?
Hubble has about factor 40 less light gathering power than Keck and might be a factor 10 more expensive, but Hubble has a higher annual amount of observing time.
Keck’s light gathering power allows to obtain a more precise spectrum of faint stars…
However, space-based and ground telescopes are complementary… and to conduct IR astronomy, we better take our (unmanned) telescopes into space, preferably to L2 wink.gif
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scalbers
post Oct 12 2007, 09:12 PM
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Here is William Johnston's Pluto map (scroll to bottom) that does some merging of the light curve data with Hubble imagery. This is one way to get the "best of both worlds".

http://www.johnstonsarchive.net/spaceart/cylmaps.html


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Louise Sharples
post Oct 12 2007, 09:31 PM
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Nicely separated, but no surface details, unlike the Hubble images. Colour me unimpressed.
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tedstryk
post Oct 12 2007, 10:12 PM
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QUOTE (Louise Sharples @ Oct 12 2007, 09:31 PM) *
Nicely separated, but no surface details, unlike the Hubble images. Colour me unimpressed.


Granted, it isn't better than Hubble, but for a ground-based image of something so faint, it is quite incredible. Glib comments like this are certainly not called for.


Scalbers: That map seems to just use the general color from the mutual events data, which at any rate only cover one hemisphere.


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nprev
post Oct 13 2007, 12:35 AM
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This is probably a dumb question (yeah, putting on my dunce hat, here), but why are the albedo maps depicted as equatorial projections? Pluto's axial tilt as I mentioned before is around 122 deg with respect to its orbit, and the Keck & Hubble images appear to give us a nearly polar view.

I know I'm missing something obvious here since its rotation period has been well-known for decades, but would appreciate enlightenment.


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