The icy moon Ariel (white) casts a shadow on the cloud tops of Uranus - the moon is named for a mischievous spirit in Shakespeare's The Tempest (Image: NASA/ESA/l Sromovsky/H Hammel/K Rages/U Wisc/Space Science Institute/SETI Institute)
Posted on 09/02/2006 3:19:24 AM PDT by Virginia-American
A tiny moon has been caught floating in front of Uranus for the first time, the Hubble Space Telescope reveals. The moon's shadow can also be seen on the planet's cloud tops, creating a solar eclipse on Uranus itself.
Hubble imaged the event unexpectedly in July 2006, during a set of observations meant to study the planet's clouds. "When we first got this image back, we looked at it and said, 'What's that bright spot and that dark spot?'" says team member Heidi Hammel of the Space Science Institute in Boulder, Colorado, US. "We thought, it must be a problem with the detector."
Then, recognising that it resembled "transit" events seen fairly frequently around other giant planets, such as when Jupiter's moon Io passes in front of that planet's disc, the researchers realised they had seen the first ever transit on Uranus. It featured the 1130 kilometre-wide (700 mile-wide) Ariel, one of the planet's 27 moons.
The events are so rare because Uranus, unlike the solar system's other planets, is tilted almost completely on its side, with its rotational axis lying nearly in its orbital plane.
Its moons, however, orbit the icy giant above its equator. So when either of Uranus's poles is facing the Sun during the planet's 84-year orbit, the moons do not cross its disc at all as seen from Earth. Instead, they circle it on orbits that resemble the rings around a bull's eye.
Rare chance
Uranus, its moons and the Sun are only in the right alignment to observe the effect every 42 years. Now, Uranus is approaching such an ideal viewing period – it will reach its equinox, in which the Sun will shine directly over the planet's equator, in 2007. "This is a once-in-a-career event for most of us," Hammel told New Scientist.
It is also the first time in the history of astronomy that such observations are even possible. When the planet's equinox last occurred, in 1965, existing telescopes were simply not powerful enough to resolve the transits. Even today, only two or three telescopes can image them, including Hubble.
"This planet and its system of rings and moons and magnetic fields are so far away, we need the biggest and best telescopes on Earth to do a lot of the observations," Hammel explains.
In fact, the planet is so far away that even the best telescopes do not have vision sharp enough to determine the moons' sizes simply by imaging them. "They're so far away, they're just points of light," Hammel continues.
But during equinoxes, astronomers can gauge the moons' sizes by observing the moons passing in front of each other or into each other's shadows. "By looking at how long it takes for the secondary satellite to go into and out of eclipse, we can figure out the size of the first moon, which is casting the shadow," she says. Knowing the moons' physical sizes reveals their mass and clues about their history, she says.
"It's very exciting," Hammel told New Scientist. "We're really hoping we get enough telescope time to do what we need to do."
The icy moon Ariel (white) casts a shadow on the cloud tops of Uranus - the moon is named for a mischievous spirit in Shakespeare's The Tempest (Image: NASA/ESA/l Sromovsky/H Hammel/K Rages/U Wisc/Space Science Institute/SETI Institute)
Truly fabulous!
Images of Uranus .... Wow who would have thunk it.... Millions of dollars on a telescope for this simply amazing.
Amazng. I wonder if NASA can keeep the Hubble Space Telscope operating.
Uranus is blue!
Not typically !!
(( Space ping ))
A piece of Uranus where the Sun don't shine...
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Mods blew this one away a day or two ago. And the fun was just beginning.
":^/
Don't they have computer simulations that would show all of those planetary orbits, along with the moons, the attending illumination from the sun, the moons, and attendant shadows cast on the planet, etc., in full graphic representation??
My God, I would place even money I can pull up Google results that will direct me to FREE SOFTWARE that will allow me to run such a graphic program on my home computer..
How is it the Space Institute doesn't have such software?
How is it they aren't running such software on their targets in the solar system?
I would think that if someone is going to use the (darn) HUBBLE telescope to take shots of Uranus, then the first thing you do is run simulations on your (darn) computer(s) to determine what it is you SHOULD be seeing, and be able to compare it to the photographic results..
Seriously, the more I think about this the more it (ticks) me off..
Bump
That's just what they'd like you to think...
Looks like a blue marble in front of black paper to me - did this photo come from seeBS?
Yeah, I didn't get theat either. I'm sure they have ephemerides for all the planets and their satelites. I rmemeber years ago there was a somwhat similar series of eclipses of Pluto and Cahron, and they had been planned for in advance.
I am really angry with Saturn and Uranus. Neptune and Jupiter are OK though.
I thought the P.C. crowd had the name changed of Uranus ......... to Urectum.
cheese
The rings of Uranus were discovered in 1977, from observations during a stellar occultation event by astronomer teams at the Kuiper Airborne Observatory (KAO) and the Perth Observatory (Australia). Just before and after the planet moved in front of the (occulted) star, the surrounding rings caused the starlight to dim for short intervals of time. Photos obtained from the Voyager-2 spacecraft in 1986 showed a multitude of very tenuous rings. These rings are almost undetectable from the Earth in visible light.
Now that is cool!
Thanks for the info, Patrick.
LOL! The IAU should really consider renaming this poor planet!
The difference between simulation and reality?
Let's see - you can have Olive Oil (Popeye's girlfriend) as your prefered simulations ....
.... and I'll have Raquel or Gina Lollobrigida.
THAT is the difference.
"The icy moon Ariel (white) casts a shadow on the cloud tops of Uranus - the moon is named for a mischievous spirit in Shakespeare's The Tempest"
A mischevous spirit around uranus.
Snicker.
Sir William Herschel, [who] formally discovered the planet on March 13, 1781, named it Georgium Sidus (George's Star) in honour of King George III of Great Britain.
When it was pointed out that sidus means star and not planet, he rebaptised it the Georgian Planet.
This name was not acceptable outside of Britain.
-- [French astronomer, Pierre] Lalande proposed in 1784 to name it Herschel, at the same time that he created the planet's symbol ("a globe surmounted by your initial"); his proposal was readily adopted by French astronomers.
-- [Swedish astronomer Erik] Prosperin, of Uppsala, proposed the names Astraea, Cybele, and Neptune (now borne by two asteroids and a planet).
-- [Finnish-Swedish-born Russian astronomer Anders Johann] Lexell, of St. Petersburg, compromised with Great Britain's Neptune.
-- [Swiss mathematician Daniel] Bernoulli, from Berlin, suggested the names Hypercronius and Transaturnis.
-- [German physicist Georg Christoph] Lichtenberg, from from Göttingen, chimed in with Austräa,, a goddess mentioned by Ovid.
The name Minerva was also proposed.
Finally,[German astronomer Johann Elert] Bode, as editor of the Berliner Astronomisches Jahrbuch, opted for Uranus, after Latinized version of the Greek god of the sky, Ouranos;
[Hungerian astromoter] Maximilian Hell followed suit by using it in the first ephemeris*, published in Vienna.
Examination of earliest issues of Monthly Notices of the Royal Astronomical Society from 1827 shows that the name Uranus was already the most common name used even by British astronomers by then, and probably earlier.
The name Georgium Sidus or "the Georgian" were still used infrequently (by the British alone) thereafter.
The final holdout was HM Nautical Almanac Office, which did not switch to Uranus until 1850.
In the Chinese, Japanese, Korean, and Vietnamese languages, the planet's name is literally translated as the sky king star (天王星).
=================================
* Ephemeris: A table giving the coordinates of a celestial body at a number of specific times during a given period.
Only if I spend too much time sitting.
Bwahahaha!
This is what I have to deal with on a daily basis.
I mean dealing with his sense of humor, not his blue anus ;-)
Juvenile-jokes-about-Uranus thread.
A thinly veiled attempt by the gay coalition to detract attention from the eviction of pluto!
I think that the guys studying Neptune's atmosphere just didn't do the calculations and were pleasantly surprised. BTW, moons' shadows on Jupiter are observed and photographed all the time.
I appreciate the clarification. lol
I hope so.
Excellent comment. A liquid through the nose shooter.
Uranus got mooned!
It's just the sheer idiocy of the quotes in the article..
Are these people astronomers or middle-school students?
"Geeze, we thought maybe Hubble was broken or something".. Duh..
These "astronomers" didn't do their homework..
Worse than you think. They called it a transit, when clearly it's an eclipse. Sheesh.
The JPL free ephemeris website http://ssd.jpl.nasa.gov/?sat_ephem claims that they produce ephemerides of Areil 0.02 arcsecond accuracy from 1980 to 2010. The diameter of Uranus is ~3.6 arc seconds viewed from Earth, so they can predict it's location to about one part in 1/180 of the diameter of Uranus. They clearly would have predicted this if they had done the math.
Reuter's exclusive! Looks like an Israeli space crime to me!
The sun is really bright there, I bet you could get a sunburn on.. you know...
Perhaps they have just enough computer time to do their stated work--taking up more computer time to work out the positions of 27 moons that have no bearing on their work might be a violation of their grant...just guessing here, perhaps computer time is a lot more plentiful than it used to be, but I still think we need more info before trashing these stargazers as imcompetents.
LOL
Pluto ....... relegated to just being man's best friend.
Not so bad.
Thanks for the ping!
"I just took this great photo of Uranus. Wanna see it?"
Cheers!
You're welcome to your opinion, but I would expect better knowledge of the subject matter than that exhibited in the article..
I'll give you this.. It may have been the reporter(s) that are mis-stating the situation / circumstances..
At any rate, knowing the albedo of one of the moons and observing it for changes as it orbits behind the planet would give indication of such things as the height and density of the atmosphere and cloud cover..
Additionally, the shadow cast upon said cloud cover could also provide information on cloud height and density...
I would bet that any stars that pass behind the planet are also observed to determine atmospheric characteristics..
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