Smile! NASA's exoplanet hunting telescope takes pic of Earth
Meteorologist/Science Writer
Friday, December 8, 2017, 1:40 PM - Where were you on Sunday afternoon? If you were outside, you're going to be part of NASA's first picture of Earth from the alien planet hunting Kepler Space Telescope!
The Kepler Space Telescope, which has provided us with a treasure trove of alien worlds to marvel over, has turned its gaze homeward this week, and for just 30 minutes on Sunday, December 10, specifically from 4:38-5:08 p.m. EST, it took an image of Earth using its sensitive optics.
According to NASA:
This event is expected to help scientists better understand and adjust for the ways Earth’s luminous presence in the skyscape affects the data retrieved by the telescope, besides being another moment to reflect on our planet’s place in the cosmos.
During that 30 minute window on Sunday, this was Kepler's view of Earth, from its position of about 140 million kilometres "behind" us in our orbit around the Sun:
A simulated view of Earth, using NASA's Eyes on the Solar System viewer, showing Kepler's view of the planet during this photo opportunity. Credit: NASA
The Kepler Space Telescope has been been gazing out into the galaxy for roughly 8 years now, giving us just a hint at how many planets there are - especially potentially habitable planets - there are beyond our solar system.
It does this by using what's known as the "transit method" of exoplanet detection. By collecting light from a star for a very long time, the spacecraft can watch how the star changes in brightness over time. If the brightness of the star suddenly dims and then returns to normal, it's possible that the telescope caught a planet around that star as it passed between us and the star, thus blocking out some of the star's light from reaching us. This is known as a transit. By tracking multiple transits of the same planet, astronomers can determine how big it is, and how close it is to its star. When telescopes on the ground point at these stars, and also detect the planets there, this shifts Kepler's "candidate" worlds to being "confirmed" planets.
The very special finds by Kepler are those smaller, likely-rocky worlds that orbit at just the right distance from their star, where it's not too hot or too cold for them to have liquid water on their surface (the so-called "habitable zone"). There's no way to tell, right now, whether these planets actually do have water, or whether they harbour alien life, so we call them "potentially habitable" worlds.
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So far, Kepler has discovered over 5,000 candidate exoplanets, and more than 2,500 confirmed ones, which includes 30 small "habitable zone" worlds. The vast majority of these were found during its initial mission, from 2009-2013, when it stared straight down our local arm of the Milky Way galaxy, taking in the light of the same grouping of around 150,000 stars, all at once, all the time. In 2013, it had to end that part of its mission due to technical problems, as it could no longer keep itself stabilized, to watch that specific set of stars.
In 2014, the telescope began its "K2" mission. Rather than consistently staring at one set of stars, Kepler instead switches targets every 80 days or so, as it trails along behind Earth and uses the pressure from sunlight on its outer hull to lend it the stability it needs.
Of the planets it has found, 515 candidates and 178 confirmed worlds have been found during the K2 mission.
This isn't the first time that NASA has snapped a pic of Earth from a distant spacecraft. We've seen ones from Cassini at Saturn and Messenger at Mercury. The Curiosity rover even snapped one from Mars, and most recently, the OSIRIS-Rex spacecraft took pictures as it flew away from Earth towards asteroid Bennu.
We're not likely to see anything pretty from Kepler's image of Earth, when it arrives back here in a few months, though. The telescope's instruments are designed for precision light sensitivity, not high-resolution details. What we get back will look more like the image Kepler took of Mars, from earlier this year.
Mars from the Kepler Space Telescope, taken on March 21, 2017. Credit: NASA
Stay tuned for when NASA releases this new photo of our homeworld.
Sources: NASA Ames | NASA's Eyes
