Meteorites can reveal a lot about the composition and formation of their parent bodies, but such postcards from beyond come with no return address, making their provenance difficult to establish. Often, astronomers must observe the object's inbound trajectory and then trace its orbit backward through time to nail down the region of space or the specific parent body that a meteorite sprang from. (In one unprecedented case announced in March, a group of researchers had the added advantage of having spotted the object in space before its atmospheric entry.)

In 2007 a sky-watching program known as the Desert Fireball Network tracked a streak of light over Australia that led researchers to meteorite fragments on the ground. Through an analysis of its composition and orbital characteristics, the meteorite, known as Bunburra Rockhole, has revealed itself to be out of the ordinary, one of a small family of its kind to not originate from a large asteroid known as Vesta. The research, led by meteoritic and planetary scientist Philip Bland of Imperial College London, appears in this week's Science.

Astronomers looking for planets encircling stars outside our solar system—known as extrasolar planets, or exoplanets—are claiming the first planetary detection from a technique known as astrometry, which tracks the location of stars in the sky with great precision.

Astrometric observations of a nearby star called VB 10 revealed a telltale motion in the star's position caused by the gravitational pull of its companion planet, dubbed VB 10b. VB 10 and its planet are an astronomical odd couple: the star is one of the least massive known, whereas the planet itself is some six times the mass of Jupiter. In contrast to the solar system, where the sun is some 10 times the diameter of the largest planet, VB 10 and VB 10b have roughly the same width.

Mission controllers last night sent a command to the Kepler spacecraft, NASA's unprecedented planet hunter launched last month, to eject its dust cover, effectively opening the telescope to the heavens.

Kepler, now some two million miles (three million kilometers) from Earth, will trail our planet in an orbit around the sun, observing a patch of sky for three-plus years in search of possible companion planets around a group of 100,000 stars. The spacecraft bears the largest space-borne camera ever, a photometer composed of 42 charge-coupled devices (CCDs), to monitor those stars for periodic dips in stellar brightness that occur as orbiting planets block a portion of the stars' light from Kepler's view.

Two teams of astronomers made headlines in November after announcing they had photographed planets orbiting regular stars other than our own sun. (Such bodies are known as extrasolar planets, or exoplanets.) One of those planets, Fomalhaut b, the companion to a star called Fomalhaut some 25 light-years away, was spotted by the Hubble Space Telescope; a star known as HR 8799, nearly 130 light-years distant, was found by ground-based observations to harbor a system of at least three planets.

Now reprocessed images taken by Hubble in October 1998 show that the space-based observatory had picked up the signal of the outermost of HR 8799's planets (white dot at lower right in image) 10 years prior to that announcement. Astronomer David Lafrenière, a postdoctoral fellow at the University of Toronto and a member of the team that found the planets around HR 8799 last year, led the archival work. In a statement, he credited an improved image-processing technique that he and colleagues developed for uncovering the hidden planet, saying it can now be used "to see planets that are one-tenth the brightness of what could be detected before with Hubble."

Saturn's G ring, a faint band of material near the outer bounds of the planet's famed ring system, hosts a bright arc about 90,000 miles (150,000 kilometers) long. The arc, or partial ring, which stretches through about a sixth of the G ring's length, is believed to provide the rest of the ring with dust and ice, but its evolution has remained a mystery.

Recent images from the Cassini spacecraft (at left) point to a moonlet embedded in the G ring. The moonlet, the Cassini team speculates, might help to repopulate the arc, and then the ring as a whole, with material as it suffers collisions with meteoroids or other small bodies within the ring.

Ice cores drilled from the poles have provided valuable historical climate records, as the composition of the ice and the air bubbles trapped therein offers a relatively pristine glimpse of ancient conditions. Now a group of Japanese scientists says that the same technique may yield records of significant astronomical events as well.

In a paper posted recently to arxiv.org, Yuko Motizuki of the RIKEN Nishina Center for Accelerator-Based Science in Wako, Japan, and colleagues present evidence for an Antarctic ice-core record of supernovae, or stellar explosions, a millennium ago. A 400-foot (122-meter) core pulled up in 2001 at Dome Fuji station in East Antarctica shows spikes in the concentration of nitrate ion (NO₃^–) that coincide with two known supernovae in the 11th century: supernova 1006, named for the year it was observed, and the Crab Nebula supernova of 1054. (Astronomers and astrologers in the Far East and the Middle East were already making detailed records of such events by that time.) Nearby supernovae, the researchers write, shower Earth with gamma rays, which can boost levels of nitrogen oxides in the atmosphere that might be recorded as nitrate spikes in the ice.

Burdened with an avalanche of astronomical images and not enough manpower to sort through them, an international consortium of institutions is turning to ordinary Web denizens for help. The Galaxy Zoo 2 project builds on the original Galaxy Zoo, launched in 2007, which presented volunteers with images of galaxies for classification as elliptical or spiral—and, if spiral, clockwise or counterclockwise. The new iteration, launched this week, follows up on that basic data set by probing galaxy structure more deeply. Galaxy Zoo 2 throws a quarter million images of bright galaxies to armchair astronomers for examination: How many arms in that spiral galaxy? How elongated is that ellipse? Does the image appear to depict a merger of multiple galaxies?

NASA and the European Space Agency (ESA) today unveiled their joint plans for exploring the outer planets, choosing to head to Jupiter and four of its moons before further exploring the moons of Saturn. Each space agency will launch a spacecraft in 2020 that will reach the Jovian system in 2026 and then spend three years exploring Jupiter and its largest natural satellites: Europa, Ganymede, Io and Callisto. ESA's craft will spend one of those years examining Ganymede, and NASA's probe will do the same for Europa.

Europa is considered one of the more habitable bodies in the solar system and so merits investigation as a possible abode for life. The Galileo spacecraft, which explored the Jovian system from 1995 to 2003, discovered what might be a subsurface ocean of liquid water under Europa's crust of ice. The moon was considered sufficiently compelling that when NASA concluded the Galileo program, the spacecraft was sent plunging to its doom in the atmosphere of Jupiter to avoid possible disruption or contamination of Europa and its ocean.

Here in New York City, where Scientific American is based, we don't often get to enjoy the pleasures of stargazing. The moon is a reliable sight, as are many of the closer stars, but relatively faint objects like Comet Lulin, making what's believed to be its maiden voyage past Earth, are usually drowned out by light pollution. In more astronomy-friendly (read: darker) corners of the globe, however, Lulin is already being spotted, more than two weeks before it ventures closest to our planet on February 24.

Amateur and professional astronomers alike have managed to catch the comet on camera—a collection of their links appears below. If you capture a good image of Lulin yourself, let us know by commenting on this blog post with a link, or get in touch via Twitter at http://twitter.com/sciam. We'll update this post as the links come in. Happy hunting!

Titan, Saturn's largest moon, has a curious abundance of methane, both in its atmosphere and in massive liquid pools on the surface. As with Mars, the presence of the relatively short-lived compound on Titan raises questions about its origin. (Methane comes largely from biological processes on Earth, but other celestial bodies might have different primary sources for the hydrocarbon, such as subsurface geologic activity—Titan appears to be something of a long shot for sustaining life.)

Satellite data from NASA's Cassini mission continue to provide clues as to the workings of Titan's methane cycle. A new paper in Geophysical Research Letters details the latest findings from Cassini, including a vast system of hydrocarbon (methane and ethane) lakes near the poles that appear to be replenished by seasonal precipitation from storm clouds. One of the lakes, whose discovery was announced last summer, is comparable in surface area to Lake Ontario.