Astronomers using data from NASA’s Transiting Exoplanet Survey Satellite have discovered a super-Earth orbiting an unusually bright, Sun-like star called HD 39091.
An artist’s impression of the super-Earth HD 39091c. Image credit: Sci-News.com.
HD 39091, also known as π Mensae, Gliese 9189 and HIP 26394, is a naked-eye G0-type star at a distance of 60 light-years.
The star has a radius about 1.1 times that of the Sun, 1.1 times the Sun’s mass, and is already known to host HD 39091b, a gas giant with a mass about 10 times that of Jupiter and an orbital period of 5.7 years.
The newly-discovered world, named HD 39091c, orbits the star every 6.27 days.
“The HD 39091 system consists of a giant planet on a long-period, highly eccentric orbit, and a super-Earth with a period that is smaller by two orders of magnitude,” said MIT astronomer Dr. Xu (Chelsea) Huang and colleagues.
“To date, only a few other systems are known with this type of architecture.”
The astronomers analyzed observations of the HD 39091 system made by NASA’s Transiting Exoplanet Survey Satellite (TESS).
“The mission of the TESS is to search for transiting planets as small as Earth around the nearest and brightest stars,” they said.
“Four 10-cm optical telescopes are used to repeatedly image wide fields and monitor the brightness of suitable stars. The data are then searched for periodic dips that could be caused by transiting planets.”
“We report on the discovery of a transiting planet around HD 39091, exactly the type of planet TESS was designed to detect.”
The team’s calculations show that HD 39091c has a radius 2.1 times that of Earth and a mass about 4.8 times the Earth’s mass.
The planet likely has a large portion of lighter materials — such as water, methane, hydrogen, and helium — in addition to a rocky/iron core.
“With a near-infrared magnitude of 4.24, HD 39091 is one of the brightest stars available for planetary atmospheric characterization with the James Webb Space Telescope (JWST),” Dr. Huang and co-authors said.
The discovery will be reported in a paper in the Astrophysical Journal Letters.
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Chelsea X. Huang et al. 2018. TESS Discovery of a Transiting Super-Earth in the π Mensae System. ApJL, in press; arXiv: 1809.05967
