On May 3rd, while preforming a semi-weekly checkup, NASA engineers found that the Kepler Space Telescope had entered “safe mode.”

What does this mean? Kepler is programmed to switch into a self-protective state in the event of an error. Powering off any non-essential systems allows Kepler to isolate probable causes for concern. The Kepler team can then interact with the spacecraft safely to turn on the systems that still work.

NASA engineers found that reaction wheel #4 had broken. After launch, Kepler used four of these spinning wheels to fine-tune and stabilize its area of observation. If the telescope is unable to point with a high level of precision, it can’t accurately measure a star’s brightness to determine if an exoplanet exists. Reaction wheel #2 failed last July, and although the spacecraft can point accurately using three reaction wheels, two will not suffice.

Unfortunately for Kepler, the spacecraft will have to wait for further notice. A diverse response team made up of people from NASA Ames, Ball Aerospace, JPL, and Goodrich Corporation are investigating wheel recovery options while Kepler resides in a fuel-efficient mode called Point Rest State.

Regardless of Kepler’s current health, researchers have already collected invaluable data revealing the diversity of planets around us. During its initial 3½-year mission plus the first few months of its extended mission, Kepler recorded light curves that show changes in brightness when a planet crosses between Kepler and the subject star. The spacecraft identified more than 2,700 planet candidates and 132 confirmed planets.

By analyzing light curves, astronomers can deduce a planet’s mass, density, and size, as well as how many planets exist in a star system, whether or not a planet orbits in its star’s habitable zone, and even some of the properties of the stars themselves.

Since Kepler has already gathered a large inventory of exoplanets, astronomers and citizen scientists have enough data to stay busy for some time to come.

The possibility of recovering reaction wheel #4 looks bleak, but don’t worry, with the data Kepler has already collected, the mission has definitely been a success!

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA

Phil Plait seemed to appreciate the news just as much. His Discover headline read in all-caps, “ALPHA CENTAURI HAS A PLANET!”

Let’s analyze all of this excitement…

Yesterday, astronomers announced they discovered an Earth-sized planet orbiting Alpha Centauri. The finding is also published in Nature today.

Alpha Centauri lies only 4.3 light-years away—closer than any other star system. And it’s not one star but three—two binary stars similar to the Sun orbiting close to each other, called Alpha Centauri A and B, plus a more distant and faint red companion known as Proxima Centauri. Since the nineteenth century, astronomers have speculated about planets orbiting these bodies, the closest possible abodes for life beyond the Solar System, but searches of increasing precision had revealed nothing. Until now.

“Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days,” says Xavier Dumusque, lead author of the paper. “It’s an extraordinary discovery and it has pushed our technique to the limit!”

A period of 3.2 days means that this new planet orbits extremely close to its parent star, “roasting at perhaps 2,200 degrees Fahrenheit with a surface likely composed of molten lava,” writes Adam Mann in Wired. Not exactly a hospitable neighbor! (Sorry, Mr. Rogers.)

This news comes right on the heels of another exoplanet discovery. On Monday, our friends at Zooniverse announced the first ever confirmed exoplanet discovered by the citizen scientists at Planet Hunters—a gas giant dubbed “PH1” with a radius about 6.2 times that of Earth, making it a bit bigger than Neptune. PH1 resides in a four-star system—twin suns that in turn are orbited by a second distant pair of stars.

These discoveries provide further evidence that, with the number of eyeballs looking for exoplanets (professional astronomers and citizen scientists alike), an Earth-like exoplanet can’t be far off. Again from the Bad Astronomer:

…we’re zeroing in on Terra Nova, folks, and statistically speaking there should be millions of them in the galaxy. It’s only a matter of time before we find the first one.

Image: ESO/L. Calçada