Newfound Alien Planet Hot Enough to Melt Iron (SPACE.com)

Astronomers have found an alien planet not much bigger than Earth, but so blisteringly hot that life has no shot of gaining a foothold there.

The exoplanet, known as Kepler-21b, is just 1.6 times bigger than our home planet, making it a so-called "super Earth." But it orbits so close to its parent star that astronomers estimate its surface temperature to be about 2,960 degrees Fahrenheit (1,627 degrees Celsius) — hot enough to melt iron.

Researchers found Kepler-21b using NASA's planet-hunting Kepler space telescope. Kepler spots alien worlds using what's called the "transit method," which looks for telltale dips in a star's brightness caused when a planet crosses in front of the star's face from Kepler's perspective, and blocks some of its light.

Astronomers then confirmed Kepler-21b with the help of telescopes at Arizona's Kitt Peak National Observatory.

Kepler-21b is located 352 light-years from Earth. Its mass is no more than 10 times that of our home planet, researchers said, but it sits just 3.7 million miles (6 million kilometers) from its host star and takes 2.8 days to complete one orbit. Earth, for comparison, zips around the sun at a distance of 93 million miles (150 million km).

Kepler-21b's parent star, known as HD 179070, is 1.3 times more massive than the sun. HD 179070 is a little hotter and brighter than our star, researchers said, and a little younger, too. Astronomers estimate its age at 2.84 billion years, compared to 4.6 billion years for the sun.

HD 179070 cannot be seen by the unaided eye, but a small telescope can easily pick it out, researchers said.

Since its launch in March 2009, the $600 million Kepler spacecraft has identified 1,235 alien planet candidates. Kepler-21b is just the 26th of these to be confirmed by follow-up observations, but Kepler scientists have estimated that at least 80 percent of the instrument's finds will end up being the real deal.

If that turns out to be the case, Kepler's discoveries will more than double the number of known alien planets, which currently stands at about 700. Astronomers think our Milky Way galaxy likely harbors billions of alien planets, though most are so far away that they'll be difficult for us to detect.

Researchers report the discovery of Kepler-21b in an upcoming issue of the Astrophysical Journal.

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Newfound Comet Will Swing By Earth in 2013 (SPACE.com)

A newfound comet discovered by a telescope designed to hunt for dangerous asteroids will make its closest pass by Earth in 2013 and should be visible to the naked eye when it draws near, astronomers say.

Hawaii's Pan-STARRS 1 telescope detected the comet, which is called C/2011 L4 (PANSTARRS), on the night of June 5 and 6, and the discovery was confirmed by follow-up observations with a different instrument a day later. The comet will likely come within about 30 million miles (50 million kilometers) of the sun in February or March 2013 — about the same distance as the planet Mercury, researchers said.

During its closest approach to Earth in two years, comet C/2011 L4 (PANSTARRS) likely to be visible low in the western sky shortly after sunset, weather permitting. Skywatchers interested in seeing the newfound icy wanderer should look up then, because they may never get another chance to see it. [Photo of comet C/2011 L4 (PANSTARRS)]

"The comet has an orbit that is close to parabolic, meaning that this may be the first time it will ever come close to the sun, and that it may never return," said the University of Hawaii's Richard Wainscoat in a statement. Wainscoat helped confirm the comet's existence.

Right now, C/2011 L4 (PANSTARRS) is about 700 million miles (1.2 billion km) from the sun, placing it beyond the orbit of Jupiter. It is currently so faint that only telescopes with sensitive electronic detectors can pick it up.

The comet's clunky moniker is slightly unusual. Comets are usually named after their discoverers, but in this case such a large team of researchers helped spot the icy wanderer that it took the name of the telescope instead.

Pan-STARRS 1 found the comet while scanning the sky for potentially hazardous asteroids — ones that may someday hit Earth. The comet, however, poses no danger to our planet, researchers said.

The telescope has a 1.8-meter-diameter mirror and the largest digital camera in the world at 1.4 billion pixels. Pan-STARRS 1 takes an image every 45 seconds, and each of these pictures is nearly 3 gigabytes in size.

Comet C/2011 L4 (PANSTARRS) most likely originated in the Oort cloud, a halo of icy objects in the far reaches of the solar system. The comet was probably flung toward the sun by a distant passing star, researchers said.

Over the next few months, astronomers will continue to study the comet, which will allow better predictions of how bright it will eventually get, researchers said.

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