December 2007

Tunguska to Arecibo: Connecting the Dots

December 19, 2007

Fifteen megatons of TNT would set off a blast a thousand times more powerful than the weapon used on Hiroshima. 2000 square kilometers of flattened pine forest near the Podkamennaya Tunguska River in central Siberia bear witness to what such a blast can do. That explosion occurred on June 30, 1908 [original typo said '2008,' [...]

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Gamma Rays and Civilizations

December 18, 2007

Lately I’ve been thinking about cosmic killers, the kind of extinction events that could destroy an entire ecosphere and any civilization living within it. It’s a natural enough thought given our speculations about life elsewhere in the universe. Just how hostile a place is the Milky Way? We’re beginning to learn that planets are abundant [...]

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Uranus & Neptune: A Planetary Switch?

December 17, 2007

How long did it take for the planets in our Solar System to form? Much depends upon the surface density of the solar nebula protoplanetary disk, the gas and dust from which the planets emerged. And the problem with surface density — mass per area — in these settings is that it’s hard to observe [...]

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Homing in on Europa Under the Ice

December 15, 2007

We wrap up our look at the American Geophysical Union meeting last week in San Francisco with an update on Europa. An interesting point that William McKinnon (Washington University, St. Louis) made in a news briefing there has that what had been a belief that there is an ocean on Europa is now hardening into [...]

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Carnival of Space 33

December 15, 2007

Universe Today offers the latest Carnival of Space, which will have exoplanet watchers checking Steinn Sigurðsson’s Dynamics of Cats site for updates on CoRoT. Almost a year into its mission, the observatory has completed its first 150-day continuous examination of the same area of sky, and the results are, so rumor has it, quite interesting. [...]

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Saturn’s Rings More Ancient than First Thought

December 14, 2007

The accepted take on the formation of Saturn’s rings not so long ago was that they had emerged within the past 100 million years. The most likely driver: A comet that broke a larger moon into pieces, forming ring features seemingly consistent with what the Voyagers saw in the 1970s and the Hubble telescope has [...]

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Gliese 581d: A Habitable World After All?

December 13, 2007

Gliese 581 is back in the news with a flourish. Astronomy & Astrophysics is publishing two independent studies of the system asserting that at least one of the inner planets is indeed located within the habitable zone of that star. Gliese 581 c and d are noteworthy every time they’re mentioned. Of five and eight [...]

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A Red Haze on Distant Exoplanet

December 12, 2007

We’re learning more and more about HD 189733b, an extrasolar planet some 63 light years from Earth in the direction of the constellation Vulpecula. This transiting ‘hot Jupiter’ orbits once every two days about three million miles out from its primary. David Charbonneau (Harvard-Smithsonian Center for Astrophysics) and team recently measured an unusual spectrum from [...]

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Voyager: Still Not Out of the Shockwave?

December 11, 2007

The recent Voyager news, reported from the American Geophysical Union conference in San Francisco and recently discussed here, has drawn attention to the apparent asymmetry of our Solar System. Voyager 1 crossed the termination shock — where the solar wind first encounters the thin gas of the interstellar medium — some three years ago. But [...]

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To Tame the Solar Wind

December 10, 2007

Some day we may be using solar sails to take payloads into an increasingly busy Solar System. Let’s hope that day isn’t far off, because the technology looks practical. But as we study solar sail methods, in which the sail is pushed by the momentum of photons, we also want to keep magnetic sail possibilities [...]

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