NASA’s Transiting Exoplanet Survey Satellite (TESS) satellite has recently characterized the first nearby super-earth outside of our solar system- located at a distance of about 31 light-years away.
Discovered in early 2019, astronomers named this super-earth as GJ 357 d. Fascinatingly, this is the first nearby super-Earth that could harbor life and the discovery could provide insight into Earth’s heavyweight planetary cousins.
Cornell’s Lisa Kaltenegger, associate professor of astronomy, director of Cornell’s Carl Sagan Institute and a member of the TESS science team, said, “The exoplanet is more massive than our own blue planet. With a thick atmosphere, the planet GJ 357 d could maintain liquid water on its surface like Earth, and we could pick out signs of life with telescopes that will soon be online.”
In Feb 2019, TESS observed that the dwarf sun GJ 357 dimmed very slightly every 3.9 days. This provides an indication of a transiting planet moving across the star’s face.
As NASA reported, the planet was GJ 357 b, a so-called “hot Earth” about 22% larger than Earth.
Further observations revealed two more exoplanetary siblings: GJ 357 c and GJ 357 d.
Exoplanet GJ 357 c sizzles at 260 degrees Fahrenheit and has at least 3.4 times Earth’s mass. However, the system’s outermost known sibling planet—GJ 357 d, a super-Earth—could provide Earth-like conditions and orbits the dwarf star every 55.7 days at a distance about one-fifth of Earth’s distance from the sun. It is not yet known if this planet transits its sun.
Jack Madden, the doctoral candidate explained, “Investigating new discoveries provides an opportunity to test theories and models. We built the first models of what this new world could be like. Just knowing that liquid water can exist on the surface of this planet motivates scientists to find ways of detecting signs of life.”
Undergraduate student Zifan Lin ’20 said, “Working on a newly discovered planet is something of a dream come true. I was among the first group of people to model its spectra, and thinking about this still overwhelms me.”
In a nod to her institute’s namesake, the late Cornell professor Carl Sagan, Kaltenegger said: “If GJ 357 d were to show signs of life, it would be at the top of everyone’s travel list—and we could answer a 1,000-year-old question on whether we are alone in the cosmos.”
Other co-authors of the study include Sarah Rugheimer, Oxford University; Antigona Segura, National Autonomous University of Mexico (UNAM); Rafael Luque and Eric Pallé, both of the Institute of Astrophysics of the Canary Islands and the University of La Laguna; and Néstor Espinoza, Max Planck Institute for Astronomy, Germany.
The study is published in the journal Astronomy & Astrophysics.