An exoplanet a whopping 17,000 light-years from Earth has been found in data collected by the now-defunct Kepler space telescope.
It is the farthest world ever recorded by the planet-hunting observatory, double the previous record. Intriguingly, the exoplanet is almost an exact twin of Jupiter – of similar mass and orbiting at almost the same distance as Jupiter’s distance from the Sun.
Dubbed K2-2016-BLG-0005Lb, it represents the first confirmed exoplanet from a 2016 data run to be discovered 27 possible objects Using a technique called gravitational microlensing instead of Kepler’s primary detection method. The discovery was submitted to the Monthly Bulletins of the Royal Astronomical Societyand is available on the preprint server arXiv.
“Kepler was never designed to find planets using microlensing, so it’s amazing in many ways that it did.” said astronomer Eamonn Kerins the University of Manchester.
The Kepler spacecraft was instrumental in blasting the field of exoplanet astronomy wide open. Launched in 2009, it spent nearly 10 years searching for extra-solar system planets, or exoplanets. During that time, his observations revealed over 3,000 confirmed exoplanets and another 3,000 candidates.
His technique is ingenious and deceptively simple. Kepler stared at starfields optimized to detect the faint, regular dips in starlight that indicate an exoplanet is in orbit around a star. This is called the transit method and is good for finding larger nearby exoplanets orbiting close to their stars.
Microlensing is a bit trickier, using a quirk of gravity and random orientation. The mass of a body like a planet creates a gravitational warp of space-time around it. When that planet then passes in front of a star, the curved space-time essentially acts like a magnifying glass, allowing the starlight to brighten up very faintly and briefly.
Gravitational microlensing is very good at finding exoplanets at great distances from Earth orbiting their stars at fairly large distances down to very small planetary masses. The most distant galactic exoplanet discovered to date has been captured through microlensing, at Earth mass world 25,000 light years away.
Because Kepler is optimized to detect changes in starlight, a team of researchers led by the University of Manchester recently considered examining the Kepler data for microlensing events from an observation window spanning several months in 2016. she 27 events identifiedfive of which were entirely new and not yet identified in data from ground-based telescopes.
“To see the effect at all requires near-perfect alignment between the foreground planetary system and a background star,” explained Kerins.
“The odds of a background star being affected by a planet in this way are tens to hundreds of millions to one. But there are hundreds of millions of stars at the center of our galaxy. So for three months Kepler just sat and watched them. “
One of the five events was K2-2016-BLG-0005Lb, and it looked promising for a star-orbiting exoplanet. So the team searched records from five ground-based surveys looking at the same patch of sky at Kepler’s time to confirm their signal.
They found that Kepler observed the signal slightly earlier and slightly longer than the five ground-based surveys. This combined dataset allowed the team to determine that the exoplanet has about 1.1 times the mass of Jupiter and orbits its star at a circular distance of 4.4 astronomical units. Jupiter’s average distance from the Sun is 5.2 astronomical units.
“The different vantage point between Kepler and observers here on Earth allowed us to triangulate where the planetary system is along our line of sight,” said Kerins.
“Kepler was also able to observe continuously through weather or daylight, allowing us to accurately determine the exoplanet’s mass and its orbital distance from its parent star. It is essentially Jupiter’s identical twin in terms of mass and position from its sun, which is about 60 percent the mass of our own sun.”
Although we currently have no further data on the system, this finding has implications for our search for extraterrestrial life. There is evidence that Jupiter may have played a instrumental role in the conditions that allowed Earth to form and thrive on Earth. Search for Jupiter analogues orbiting distant stars could be a way to identify these conditions.
The fact that Kepler, an instrument not designed for microlenses, was able to perform this type of detection bodes well for future instruments that can will be designed for micro lenses. NASA’s Roman Space Telescope Nancy Grace is scheduled to be launched in the next five yearswill be on the lookout for microlensing events, as will ESA Euclidplanned for a launch next year.
These discoveries could revolutionize our understanding of exoplanets.
“We learn how typical the architecture of our own solar system is,” said Kerins. “The data will also allow us to test our ideas about how planets formed. This is the beginning of a new exciting chapter in our quest for other worlds.”
The research was submitted to the Monthly Bulletins of the Royal Astronomical Society and is available on arXiv.