Astronomers have discovered an exoplanet with several times the mass of the Earth orbiting a nearby star. A paper reporting this discovery is published in the Monthly Notices of the Royal Astronomical Society (arXiv.org preprint).
An artist’s impression of HD 26965b and its star. Image credit: Sci-News.com.
Designated HD 26965b, the newly-detected alien world has a mass of 8.47 Earth masses and is located a mere 16 light-years away.
This planet revolves around the bright K-class dwarf star HD 26965 once every 42.4 days.
The host star is approximately 6.9 billion years old, has a mass about 78% of the Sun’s and a radius 87% as large.
“HD 26965 is the primary of a very widely separated triple system. The other two companions are an M4 dwarf and a white dwarf,” said University of Florida astronomer Bo Ma and co-authors.
“This star is a very bright metal poor star with an absolute magnitude of V=4.4. This makes it the second brightest star in the night sky with a super-Earth detection so far, just behind HD 20794 (V=4.3).”
“One interesting fact is that HD 20794 has a similar metallicity as HD 26965, which is consistent with the finding that smaller planets are detected around stars with wide-ranging metallicities.”
“With a minimum mass of 8.4 Earth masses, HD 26965b likely possesses a gaseous atmosphere based on other planets with known masses and radii,” they added.
“However, we note that Kepler-10c has a similar mass and orbit, is hosted by a similar, low-metallicity star, and does not possess an envelope, so HD 26965b may be a similar type of world.”
HD 26965b was found using the ‘wobble’ method, called radial velocity, by the Dharma Planet Survey (DPS).
This method watches for the telltale jitters of stars as they are pulled back and forth by the gravitational tugs of an orbiting planet; the size of the wobble reveals the mass of the planet.
“In a search through the early data from the DPS survey, we discovered a radial velocity signal consistent with a super-Earth orbiting a V=4.4 K dwarf, HD 26965. Additional radial velocity data were found from the Keck archive and HARPS archive,” the astronomers said.
“The same signal was independently detected by Matias Diaz of the Universidad de Chile and co-authors, but they could not confirm if it is from a planet or from stellar activity.”
_____
Bo Ma et al. The first super-Earth Detection from the High Cadence and High Radial Velocity Precision Dharma Planet Survey. MNRAS, published online July 19, 2018; doi: 10.1093/mnras/sty1933
Matias R. Diaz et al. 2018. The Test Case of HD 26965: Difficulties Disentangling Weak Doppler Signals from Stellar Activity. AJ 155, 126; doi: 10.3847/1538-3881/aaa896
