By Prarthana Mitra
An exoplanet, christened Wolf503b, was discovered by a team of German and Canadian stargazers at NASA. It is situated 145 light years away from the earth, and supposedly twice its size.
The Kepler Space Telescope made this wondrous discovery along with a few others, which are enumerated in detail in a study led by Merrin Peterson, an Institute for Research on Exoplanets (IREX) graduate who obtained her postgraduate degree in May.
How did they go about characterising it?
Locating it in the Virgo constellation, Peterson’s study noted that Wolf503b orbits its star every six days which means it is pretty close to it, about 10 times closer than Mercury is to the Sun.
Acknowledging her advisor Bjorn Benneke in the discovery process, she told Science Daily, “In May, when the latest release of Kepler K2 data came in, we quickly ran a program that allowed us to find as many interesting candidate exoplanets as possible. Wolf 503b was one of them.”
In order to characterise the system of stars better, the astronomers first obtained a spectrum of the host star at the NASA Infrared Telescope Facility, which confirmed it to be an old ‘orange dwarf,’ slightly less bright than the Sun and twice as old. It also allowed for a precise determination of the radius of both the star and its companion.
To rule out inaccurate naming, the team obtained adaptive optics measurements from Palomar Observatory and also examined archival data, which enabled them to confirm the exoplanet didn’t have a more massive companion that could be interpreted as a transiting planet.
Why is Wolf 503b interesting?
Astronomers have often wondered whether exoplanets are small and rocky ‘super-Earths’ or gaseous mini versions of Neptune. According to a recent discovery in 2017, there are significantly fewer planets that are between 1.5 and 2 times the size of Earth than those either smaller or larger than that. This drop, called the Fulton gap, distinguishes the two types of planets from each other.
“Wolf 503b is one of the only planets with a radius near the gap that has a star that is bright enough to be amenable to more detailed study that will better constrain its true nature,” explained Benneke, Professor at the Universite de Montreal in Canada.
“It provides a key opportunity to better understand the origin of this radius gap as well as the nature of the intriguing populations of ‘super-Earths’ and ‘sub-Neptunes’ as a whole.”
Wolf 503b is relatively close to Earth than other exoplanets, and thus very bright, making it the cynosure of attention for the upcoming James Webb Space Telescope. Its mass and radius determined by Kepler’s observations shed light on the bulk density of the planet and its composition.
Using a technique called transit spectroscopy, it will now be possible to study the chemical content of the planet’s atmosphere, and to detect the presence of molecules like hydrogen and water, a crucial parameter to determine similarity with Earth or Neptune. This was not possible for most exoplanets.
“By investigating the nature of Wolf 503b, we’ll understand more about the structure of planets near the radius gap and more generally about the diversity of exoplanets present in our galaxy,” said Peterson. “I look forward to learning more about it.”
Prarthana Mitra is a staff writer at Qrius