Gravitational microlensing has been actively employed in the search for MACHOs (Massive Astrophysical Compact Halo Objects) in the galactic halo, although with ambiguous results. The idea here is to find large, dark objects by detecting the microlensing effects they produce on stars behind them. While these dark matter studies have looked toward the Large Magellanic Cloud, we are using the same technique elsewhere in the planet hunt, finding that exoplanets can magnify the light of stars behind them in the galactic bulge, producing a clear detection. Remember, for this kind of work, you want a dense background field of stars because the alignment needed for microlensing is obviously rare. The Magellanics are ideal, as is the galactic bulge, and so, for that matter, is M31, the Andromeda galaxy. And if our early exoplanet work, relying on radial velocity and transit methods, has naturally produced large planets in the Jupiter class, microlensing can be quite effective at smaller...

Planets around binary stars continue to be a major interest here, given our fascination with nearby Alpha Centauri. Thus the recent radio interferometry images captured by the Submillimeter Array radio telescope system (Mauna Kea) come right to the top of the queue. We're looking at a young binary system called V4046 Sagittarii, providing a glimpse of planetary system formation occurring around two stars of roughly the Sun's mass. This system is approximately 240 light years from our own. Image: Submillimeter Array image of the rotating, gaseous disk surrounding the young twin-star system V4046 Sagittarii (located at the white dot in the image). Note the size of the V4046 Sagittarii disk relative to the orbit of Neptune, shown to scale at the lower right (the filled oval at lower left represents the size of the smallest structures that could be detected in the image). The disk is tipped from our perspective, such that it appears as elliptical rather than circular. The image is...

I love Greg Laughlin's remark to the Washington Post's Joel Achenbach in last week's article Astronomers Seek New Home Closer to Home. Having discussed Debra Fischer's ongoing search for Alpha Centauri planets and his own theories on planet formation around binary stars, Laughlin points out where we stand today: "We have what is to all appearances by far the best planet in the galaxy. And we have no workable backup plan." The Washington Post article doubtless draws on Lee Billings' earlier piece in SEED Magazine called The Long Shot, which discusses with an elegance rare in science writing the attempt to find planets around the Centauri stars by Fischer as well as Michel Mayor's Geneva team. Mayor has been using the High Accuracy Radial velocity Planet Searcher (HARPS) instrument at La Silla, the Cadillac of radial velocity instrumentation (and boy does that auto industry reference date me!). Competition can work wonders, and having two teams on the case can only bode well for quick...

We're now up to 347 detected exoplanets around 293 stars. The latest find turns out to be intriguing on several counts. VB 10 is a red dwarf about 20 light years away in the constellation Aquila. Its newly detected planet is a gas giant with a mass six times that of Jupiter, a 'cold Jupiter' not so different from our own. Interestingly, although the star is considerably more massive, both planet and star should have roughly the same diameter. Image: This artist's diagram compares our solar system (below) to the VB 10 star system. Astronomers successfully used the astrometry planet-hunting method for the first time to discover a gas planet, called VB 10b, around a very tiny star, VB 10. All of the bodies in this diagram are shown in circular insets at the same relative scales. Astrometry involves measuring the wobble of a star on the sky, caused by an unseen planet yanking it back and forth. Because the VB 10b planet is so big relative to its star, it really tugs the star around. The...

Anyone who thought the Deep Impact mission was over when the spacecraft drove an impactor into comet Tempel 1 some four years ago has been given a lesson in the strategy of extended missions. Now heading for a flyby of comet Hartley 2 (late in 2010), Deep Impact is also doing yeoman work in the study of extrasolar planets. That phase of the mission is called Extrasolar Planet Observations and Characterization (EPOCh), but the spacecraft housing both investigations is now referred to as EPOXI. If the acronyms can be confusing, the latest news from EPOXI is straightforward, and encouraging. A paper slated for summer publication in the Astrophysical Journal reports on the spacecraft's observations of our own planet, made in 2008 when it was between 17 and 33 million miles from Earth. The idea was to tune up our capabilities at observing distant planets, using spectral information to map the distribution of continents and oceans. EPOXI's High Resolution Imager thus set up a trial of...

Finding Earth-like planets around any star would be a stunning feat, and either Kepler or CoRoT may deliver such news before too long. But how much more exciting still if we find a planet like this around a star as close as Centauri B? After all, the Centauri stars are our closest stellar neighbors, close enough (a mere 40 trillion kilometers!) to conjure up the possibility of a robotic mission there and, if we play our propulsion cards right in the future, perhaps a manned trip as well. A Radial Velocity Long Shot But can we pick up the faint signature of a terrestrial world in this system, given that it would be akin to 'detecting a bacterium orbiting a meter from a sand grain -- from a distance of 10 kilometers'? The phrase is Lee Billings', from his fine essay in SEED called The Long Shot, on an ongoing project to do just that. Most radial velocity surveys are spread out over numerous stars, picking off close-in worlds whose traces should be obvious in short periods of time....