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Notes & Queries 9/22/07

Apropos of our recent speculations about planets without stars, this short podcast from Earth & Sky discusses dark planets within our galaxy able to sustain life, at least for a while. The scenario, developed by John Debes (Carnegie Institution) and Steinn Sigurðsson (Pennsylvania State): A planet with a large moon passes near a giant world like Jupiter. The team’s simulations show the Earth-moon system ejected into interstellar space, with the possibility of a thick atmosphere and large tidal forces keeping the place warm for more than a hundred million years.
ESA’s latest backgrounder on the Don Quijote candidate mission lays out a plan to rendezvous with an asteroid and orbit it, monitoring its shape, mass and gravitational field. A second spacecraft would then be sent to impact the asteroid at about 10 km/s, while the first vehicle monitors the result, looking for changes in the asteroid’s trajectory. Mission planners have considered oft-mentioned Apophis as one of several potential targets. Even if approved, Don Quijote wouldn’t launch until early in the next decade. The recent impact in Peru reminds us of the need to learn more about space debris, though Tunguska left a far starker testament.
Anticipating the next generation of ground and space-based telescopes, astronomers convene at the Astrophysics in the Next Decade conference on September 24 in Tucson. The rapidly expanding pace of exoplanetary investigation will only be accelerated as equipment ranging from the European Extremely Large Telescope to the James Webb Space Telescope comes online, not to mention what we’ll learn from earlier space missions like Kepler. We may know within the next twenty years (via spectroscopic studies) whether one or more terrestrial exoplanets are likely candidates for life. Ironically, the demonstration of such may well come before we know for sure whether places much closer to home, like Mars or Europa, are themselves life-bearing.
HD 74156 becomes the eighth star known to be orbited by three or more planets, thanks to recent work using data from the Hobby-Eberly Telescope. The star is a G0 some 65 parsecs from the Sun, its two previously discovered planets being 6.2 and 1.9 Jupiter masses respectively. The lower mass world is known to be in a short-period orbit (51.7 days), the larger in a much wider 2477 day orbit. The new planet has an orbital period of 347 days and a minimum mass of 0.4 Jupiter masses; all three orbits show significant orbital eccentricity. The paper is “Detection of a Third Planet in the HD 74156 System Using the Hobby-Eberly Telescope,” accepted by The Astrophysical Journal (abstract).
Imagine Isaac Newton working with a slightly different apparatus than the one he used to study the nature of light. Here’s Astounding/Analog editor John Campbell on the matter, as found recently on Crowlspace:

Literally, by a hairline Newton missed the spectroscope. Had he used a slit, the spectrum of the Sun would have been bright colors crossed by mysterious black bands and lines. He could not have left that mystery untouched. He would have found that sodium thrown on a candlewick would produce bright-yellow lines matching exactly two powerful dark lines in the mysterious solar spectrum. Calcium would have given him red lines, copper and other metals…

The result: A jump start on basic chemistry and spectroscopy. Would Newton, discovering the absorption lines in the spectrum go on to influence others to deliver the goods on distant planetary atmospheres? If so, as Adam Crowl speculates, a possible downside might have been a slowdown in the birth of spaceflight, the Solar System early on being seen as devoid of life. A fascinating speculation indeed.

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  • ljk March 13, 2008, 11:05


    A meteorite that struck Peru in September, digging out a
    deep hole and startling nearby residents, behaved so strangely
    that scientists may have to rethink what happens when space
    objects hit planets.