NASA's Kepler spacecraft has been observing deep in the Milky Way galaxy for almost a decade. It has detected more than 2,500 confirmed planets orbiting distant stars, and more than 2,500 other worlds are waiting to be confirmed. Thirty of these confirmed planets live within the habitable zones of their host stars, places where liquid water could exist as it does on Earth.
But Kepler is running out of gas now.
"With nary a gas station can be found in deep space, the spacecraft will run out of fuel," said in a statement from NASA Charlie Sobeck the systems engineer for the mission of the Kepler space telescope .
"We hope to reach that moment in several months."
NASA placed the Kepler telescope 94 million miles from Earth, in an orbit around the sun. In this way, Earth's gravity and reflected light do not interfere with Kepler's precise measurements of distant planets.
Out there, in a vacuum, it is extremely unlikely that Kepler will become a threatening piece of space debris that could present collision risks for other satellites.
"Deep space missions like Kepler are neither close to Earth nor in sensitive environments, which means we can afford to extract every last bit of data from the spacecraft," Sobeck said.
It's amazing that Kepler is still working.
In 2013, a wheel used to keep the ship pointed in the right direction broke, which means that Kepler's entire mission, which depended on pointing in a specific direction, had to change.
However, NASA found a way to temporarily stabilize the telescope for months at a time by using the pressure of sunlight, "like a directional kayak in the stream," Sobeck said.
Since then, Kepler has detected hundreds of exoplanets, more than 300 of which have been confirmed.
When Kepler sees an exoplanet, however, it does not actually capture an image of the distant planetary body; They are too far. Instead, Kepler observes a star that is submerged in brightness when a planet pbades from time to time in front of the distant star.
NASA scientists can then judge the size and possible composition of the exoplanet based on how long it took to travel around the star and how much light temporarily blocked the planet.
Although Kepler will soon be exhausted and leave its long and lonely orbit in space, the spacecraft will soon be replaced by another exoplanet-space-hunting telescope, NASA's in-transit exoplanet study satellite (TESS).
TESS will launch into space on April 16.
"TESS will search for planets outside our solar system in almost all of the sky, focusing on the brightest stars less than 300 light-years away, and adding to Kepler's treasure discovery of the planet's discoveries," Sobeck said.