Most distant exoplanet discovered by Kepler turned out to be… surprisingly familiar

(ORDO NEWS) — An exoplanet 17,000 light-years from Earth has been discovered in data collected by the now-defunct Kepler space telescope.

It is the most distant world ever discovered by a planet-hunting observatory, twice as large as the previous record. It is noteworthy that the exoplanet is an almost exact twin of Jupiter – it has a similar mass and orbits at a distance almost equal to the distance of Jupiter from the Sun.

Named K2-2016-BLG-0005Lb, it is the first exoplanet confirmed in a 2016 data analysis that found 27 possible objects using gravitational microlensing rather than Kepler’s main detection method. Information about the discovery was presented in the Monthly Notices of the Royal Astronomical Society and is available on the arXiv preprint server.

Kepler was not designed to search for planets using microlensing, so in many ways it is surprising that it succeeded,” said astronomer Eamonn Kerins of the University of Manchester.

The Kepler spacecraft played a huge role in the discovery of the field of exoplanet astronomy. It was launched in 2009 and has spent nearly 10 years looking for planets outside the solar system, or exoplanets. During this time, his observations revealed more than 3,000 confirmed exoplanets and 3,000 more candidates.

His technique is ingeniously and deceptively simple. Kepler looked at fields of stars optimized to detect faint, regular dips in starlight that indicate an exoplanet is in orbit around a star. This is called the transit method, and it’s good for finding large, nearby exoplanets orbiting their stars.

Microlensing is a bit more complicated, it uses a quirk of gravity and random alignment. The mass of a body, such as a planet, creates a gravitational curvature of space-time around it.

If this planet passes in front of a star, then the curved space-time acts like a magnifying glass, which very weakly and briefly causes the star’s light to become brighter.

Gravitational microlensing is very well suited for searching for exoplanets at a great distance from the Earth, orbiting their stars at quite large distances, down to very small planetary masses. The most distant galactic exoplanet discovered to date has been found using microlensing – it’s an 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 decided to look at Kepler’s data for microlensing events spanning several months in 2016. They identified 27 events, five of which were completely new, not yet detected in ground-based telescope data.

“To see the effect at all, a near-perfect alignment between the foreground planetary system and the background star is required,” Kerins explained.

“The odds of a planet having such an impact on a background star are tens to hundreds of millions to one against. But there are hundreds of millions of stars at the center of our galaxy. So Kepler just sat there and watched them for three months.”

One of the five events was K2-2016-BLG-0005Lb, and it looked promising for an exoplanet orbiting the star. To confirm their signal, the team turned to data from five ground-based surveys that were observing the same patch of sky at the same time as Kepler.

They found that Kepler observed the signal a little earlier and a little longer than the five ground observations.

This combined data set allowed the team to determine that the exoplanet has a mass of about 1.1 times that of Jupiter and orbits its star at a distance of 4.4 astronomical units. The average distance of Jupiter from the Sun is 5.2 astronomical units.

The difference in viewpoint between Kepler and observers on Earth allowed us to triangulate where the planetary system is on our line of sight,” Kerins said.

Kepler was also able to observe without interference from weather or daylight, allowing us to accurately determine the mass of the exoplanet and its orbital distance from the host star. In fact, it is an identical twin of Jupiter in terms of mass and distance from the Sun, the mass of which is about 60 percent of the mass of our Sun.

While we currently have no more data on this system, this discovery has implications for our search for extraterrestrial life.

There is reason to believe that Jupiter may have played an important role in the conditions that allowed the Earth to emerge and thrive on Earth; searching for analogues of Jupiter in the orbits of distant stars may be a way to identify these conditions.

The fact that Kepler, a non-microlensing instrument, was able to make such a detection bodes well for future microlensing instruments. NASA’s Nancy Grace Roman Space Telescope, scheduled to launch within the next five years, will search for microlensing events, as will ESA’s Euclid, scheduled to launch next year.

These discoveries could revolutionize our understanding of exoplanets.

“We will learn how typical the architecture of our own solar system is,” Kerins said. The findings will also allow us to test our understanding of how planets form. “This is the beginning of an exciting new chapter in our search for other worlds.”


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