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Hubble has observed every planet in the solar system but one: Mercury.
So Hubble has observed the Sun, but it did so literally bass-ackwards. That was to protect its mirror; raw UV from the Sun can photochemically damage sensitive parts inside the ‘scope, and of course can heat them up to dangerous levels. Also, as I pointed out before, some of the cameras would in fact be damaged by direct sunlight.
Because of that, Hubble is not allowed to point anywhere near the Sun, just to make sure no stray light seeps in. This “solar avoidance zone” is a circle 50 degrees in radius around our star. Anything closer than that is forbidden.
This directive has been broken by Hubble precisely once: to observe Venus, which gets about 45 degrees from the Sun at maximum. These observations were made using WFPC2 (shown in the image above; it was taken in the near-UV to see structure in the Venusian clouds) and the Goddard High Resolution Spectrograph. Astronomers were looking for sulfur dioxide in the atmosphere of Venus, a chemical which had been detected by an earlier probe and might be emitted by volcanism on the planet. All kinds of overrides had to be sent to the telescope to allow these observations, and it was so difficult that it hasn’t been and probably won’t ever be repeated.
But Mercury never gets even that far from the Sun; at most it is a mere 28 degrees from the Sun, far too close to ever be seen by Hubble. But that’s OK: we have the MESSENGER spacecraft. It’s zipped past Mercury twice already, and will fly by Mercury one more time in the coming months before falling into orbit around the innermost planet in 2011, where it will map the planet with far higher detail than Hubble ever could.
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Links to this Post
- Happy Birthday Hubble! at Asymptotia | April 24, 2012
- 22nd Aniversary of Hubble Deployment | ALuRic.net | April 25, 2012
- This Day In History For April 25, Hubble, W-2 and More | Wis U.P. North | April 25, 2012
- Hubble Spies Brilliant Beacons From a Dying Star: Big Pic – Discovery News | Danta Report | April 26, 2012
- Friday Links | April 26, 2012
- An Orion Sunset | David Reneke | Space and Astronomy News | April 27, 2012
- The Week in Review « Tor/Forge's Blog | April 27, 2012
- Astronomy News Round-up « Space « Science Today: Beyond the Headlines | April 27, 2012