Astronomers discover 'super-Earth' planet orbiting nearby star

May 29, 2017 by Tomasz Nowakowski, report
Phase folded curve of the planetary signal detected in GJ 625 using the parameters of the MCMC model. Left panel shows the CCF measurements, right panel the TERRA measurements. Grey dots show the measurements after subtracting the detected activity induced signals. Red dots are the same points binned in phase with a bin size of 0.1. The error bar of a given bin is estimated using the weighted standard deviation of binned measurements divided by the square root of the number of measurements included in this bin. Blue line shows the best fit to the data using a Keplerian model. Credit: Mascareño et al., 2017.

(—European astronomers report the detection of a new extrasolar world several times more massive than Earth. The newly found exoplanet, classified as a so-called "super-Earth," is circling a nearby star designated GJ 625. The researchers detailed their finding in a paper published May 18 on

"Super-Earths" are more massive than Earth but not exceeding the mass of Neptune. Although the term "super-Earth" refers only to the mass of the planet, it is also used by astronomers to describe planets bigger than Earth but smaller than the so-called "mini-Neptunes" (with a radius between two to four Earth-radii).

Located only 21 light years away, GJ 625 is an M-dwarf star (spectral type M2) about 1/3 the size and mass of the sun. Such offer great potential in the search for alien Earth-like worlds, as low-mass rocky planets appear to be more frequent around M-dwarfs. However, finding an Earth-like planet orbiting low-mass stars is difficult due to their stellar activity. This is because signals induced by the rotation of a star can easily mimic those of planetary origin. Therefore, the signals coming from M-dwarfs tend to be comparable to those of close to the habitable zone of their stars.

Recently, a team of astronomers led by Alejandro Suarez Mascareño of the Canary Islands Institute of Astrophysics, has completed challenging studies of GJ 625, which began in 2013 and lasted over three and a half years. The observations were conducted with the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) spectrograph installed at the Telescopio Nazionale Galileo at the Roque de los Muchachos Observatory on the island of La Palma, Canary Islands, Spain.

The researchers analyzed 151 radial-velocity time series from HARPS-N as part of the HArps-n red Dwarf Exoplanet Survey (HADES) radial velocity program, which resulted in the discovery of a new planet.

"We report the discovery of a super-Earth orbiting at the inner edge of the habitable zone of the star GJ 625 based on the analysis of the radial-velocity (RV) time series from the HARPS-N spectrograph, consisting in 151 HARPS-N measurements taken over 3.5 yr," the paper reads.

The newly found alien world, designated GJ 625 b, has a minimum mass of 2.8 Earth masses, which makes it the lightest exoplanet found around an M2 star to date. The planet orbits its host every 14.6 days at a distance of approximately 0.08 AU from the star, which is relatively close. By comparison, Mercury orbits the sun at a mean distance of 0.38 AU.

The results of radial velocity measurements allowed the team to conclude that GJ 625 b is a small "super-Earth" on the inner edge of the and has a mean surface temperature of 350 K that is very dependent on the atmospheric parameters. Moreover, the researchers assume that the newly detected exoworld might potentially host liquid water, but more observations focused on GJ 625 b's atmosphere are required to confirm this assumption.

Explore further: Scientists discover a nearby superearth

More information: HADES RV Programme with HARPS-N at TNG: V. A super-Earth on the inner edge of the habitable zone of the nearby M-dwarf GJ 625, arXiv:1705.06537 [astro-ph.EP]

We report the discovery of a super-Earth orbiting at the inner edge of the habitable zone of the star GJ 625 based on the analysis of the radial-velocity (RV) time series from the HARPS-N spectrograph, consisting in 151 HARPS-N measurements taken over 3.5 yr. GJ 625 b is a planet with a minimum mass M sin i of 2.82 ± 0.51 M⊕ with an orbital period of 14.628 ± 0.013 days at a distance of 0.078 AU of its parent star. The host star is the quiet M2 V star GJ 625, located at 6.5 pc from the Sun. We find the presence of a second radial velocity signal in the range 74-85 days that we relate to stellar rotation after analysing the time series of Ca II H&K and Hα spectroscopic indicators, the variations of the FWHM of the CCF and and the APT2 photometric light curves. We find no evidence linking the short period radial velocity signal to any activity proxy.

Related Stories

Scientists discover a nearby superearth

November 17, 2016

Ph.D. student Alejandro Suárez Mascareño, of the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL), and his thesis director, Rafael Rebolo and Jonay Isaí González Hernández, have discovered ...

Earth-like planet may exist in a nearby star system

April 19, 2016

(—An Earth-like planet may be lurking in a star system located just 16 light years away, according to a new research. The star, named Gliese 832, was recently investigated by a team of astronomers searching for ...

The space weather forecast for Proxima Centauri B

April 3, 2017

Proxima Centauri, the closest star to the Earth (only 4.28 light-years away) is getting a lot of attention these days. It hosts a planet, Proxima Cen b, whose mass is about 1.3 Earth-mass (though it could be larger, depending ...

Recommended for you

Ancient meteorite tells tales of Mars topography

May 24, 2018

By looking at an ancient Martian meteorite that landed in the Sahara Desert, Lawrence Livermore National Laboratory (LLNL) scientists and collaborators have determined how and when the red planet's crustal topographic and ...

Rosetta unravels formation of sunrise jets

May 23, 2018

The atmosphere of Rosetta's comet 67P/Churyumov-Gerasimenko is far from homogeneous. In addition to sudden outbursts of gas and dust, daily recurring phenomena at sunrise can be observed. In these, evaporating gas and entrained ...

Drilling success: Curiosity is collecting Mars rocks

May 23, 2018

Engineers working with NASA's Curiosity Mars rover have been hard at work testing a new way for the rover to drill rocks and extract powder from them. This past weekend, that effort produced the first drilled sample on Mars ...

New study details geological process behind Titan's dunes

May 23, 2018

Titan's windswept dunes may sprawl millions of more kilometers than previously thought and were likely formed by geological processes similar to those on Earth, according to a new study. The new findings could help scientists ...


Adjust slider to filter visible comments by rank

Display comments: newest first

5 / 5 (2) May 29, 2017
"Located only 21 light years away, GJ 625 is an M-dwarf star (spectral type M2) about three time the size and mass of the sun." Huh? A red dwarf star of three solar masses?
5 / 5 (2) May 29, 2017
Actually, it's:
M(star) [Msun] 0.30 +/-0.07
R(star) [Rsun] 0.31+/-0.06
... according to the PDF on ...
Notified the editors, hope this will be corrected soon ...
1 / 5 (5) May 29, 2017
14 day orbital period, 0.08 Au, most likely a moon orbiting a planet.
not rated yet Jun 12, 2017
Giving the planet's expected surface temperature in degrees Kelvin is a bit misleading. 350K - 273.15 = 76.85°C (Or 170 degrees Fahrenheit if you prefer.) Humans might be able to live near the poles, but if there is enough water to make it habitable, rainfall near the equator would probably make living there impossible. Of course, mountains near the equator, or (desert) areas downwind of mountain ranges might be habitable as well.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.