Space.com (December 28, 2009)
"This year provided plenty of cosmic eye-openers for astronomers and casual stargazers alike. Neighborhood planets such as Mercury and Jupiter received makeovers in both a scientific and literal sense. The discovery of water on the moon and Mars provided clues to the past, not to mention hints for the future of space exploration. A class of newly-detected 'Super-Earth' planets around alien stars may ultimately prove more habitable than Earth. And a growing fleet of existing, new and revived space telescopes promises another stellar year ahead.
"Here are the stories that stood out:
"9. Oddball Objects
"Earth had a front row seat to a multitude of space objects in 2009, with stunning meteor showers, wayward space rocks buzzing the planet and weird lights in the sky – both natural and man-made.
"Annual light shows such as the Leonid meteor shower continued to dazzle, but some space rocks came a bit too close for comfort. An asteroid exploded over Indonesia with the force of several Hiroshima bombs on Oct. 8, 2009, and became the biggest space rock to take aim at Earth in more than a decade...."
The list goes on, with links to related articles like the one I included in that quote. The items are in the familiar 'countdown' order, like "8. Mercury, Unmasked" and "4. First Rocky Planet Around Alien Star."
The article does a pretty good job of summarizing each of the nine big deals the Space.com folks chose as the top items relating to astronomy in 2009.
Rocky Planet Horror ShowThat heading almost makes sense. Keep reading.
One of this year's big deals, "4. First Rocky Planet Around Alien Star," is about COROT-7b: a planet that's 400 or 500 light years away, depending on which account you read. The planet orbits a G9 star in the constellation Monoceros: Our star is spectral class G2. At that range, working out exact distances for a star is tricky. Then, there's the matter of editorial decisions when it comes to rounding off numbers.
Anyway, COROT-7b made it into the December issue of Sky and Telescope, too. (Vol. 118, No. 6, p. 14 - if you don't have it, your local library might)
What made it possible to figure out that COROT-7b was a rocky world, like the one we're standing on, is that astronomers were able to measure its diameter. COROT-7b passes in front of its star on each orbit, as seen from Earth. By carefully measuring the 1-part-in-3,000 dimming of the star, astronomers got a diameter of 4.8 times the diameter of Earth - give or take 0.8 Earth-diameters.
With the mass of COROT-7b known by how much its star wobbles, the average density of the planet can be determined: 5.6 grams per cubic centimeter. Give or take 1.3. Earth's average density is 5.51 grams per cubic centimeter.
With an average density that close to our home planet's, odds are that COROT-7b is made of a mix of metal and rock, like Earth.
Don't make vacation plans, though. Even if we could get there, the weather is awful. When it rains on COROT-7b, it rains rock. (October 1, 2009)
- "Another Super-Earth: Probably With Water, Possibly With Strange Chemistry"
(December 17, 2009)
- "Earth May Not Be a "Class M" Planet"
(December 5, 2009)
- "Water on Mars: The Lost Ocean of Barsoom?"
(November 23, 2009)
- "Water - On the Moon?!"
(November 15, 2009)
- "COROT-7b: A Planet with Weather Worse than Minnesota's"
(October 1, 2009)
- "Mercury: A Hot Little Planet"
(May 2, 2009)
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