TESS Discovery Leads to Surprising Find of Promising World

Released Wednesday, July 31, 2019

ID: 13266

- Produced by:
- Chris Smith
- Visualizations by:
- Chris Smith
- Written by:
- Francis Reddy

Tour the GJ 357 system, located 31 light-years away in the constellation Hydra. Astronomers confirming a planet candidate identified by NASA’s Transiting Exoplanet Survey Satellite subsequently found two additional worlds orbiting the star. The outermost planet, GJ 357 d, is especially intriguing to scientists because it receives as much energy from its star as Mars does from the Sun.

Credit: NASA's Goddard Space Flight Center

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Music: "Golden Temple" from Killer Tracks.

Complete transcript available.

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A planet discovered by NASA’s Transiting Exoplanet Survey Satellite (TESS) has pointed the way to additional worlds orbiting the same star, one of which is located in the star’s habitable zone. If made of rock, this planet may be around twice Earth’s size.

The new worlds orbit a star named GJ 357, an M-type dwarf about one-third the Sun’s mass and size and about 40% cooler that our star. The system is located 31 light-years away in the constellation Hydra. In February, TESS cameras caught the star dimming slightly every 3.9 days, revealing the presence of a transiting exoplanet — a world beyond our solar system — that passes across the face of its star during every orbit and briefly dims the star’s light.

The transits TESS observed belong to GJ 357 b, a planet about 22% larger than Earth. It orbits 11 times closer to its star than Mercury does our Sun.

But while researchers were looking at ground-based data to confirm the existence of the hot Earth, they uncovered two additional worlds. The farthest-known planet, named GJ 357 d, is especially intriguing. The planet’s size and composition are unknown, but a rocky world with this mass would range from about one to two times Earth’s size.

GJ 357 d is located within the outer edge of its star’s habitable zone, where it receives about the same amount of stellar energy from its star as Mars does from the Sun. If the planet has a dense atmosphere, which will take future studies to determine, it could trap enough heat to warm the planet and allow liquid water on its surface.

GJ 357 c, the middle planet, has a mass at least 3.4 times Earth’s, orbits the star every 9.1 days at a distance a bit more than twice that of GJ 357 b. TESS did not observe transits from this planet, which suggests its orbit is slightly tilted — perhaps by less than 1 degree — relative to the hot Earth’s orbit, so it never passes across the star from our perspective.

Recorre el sistema GJ 357, ubicado a 31 años luz de distancia, en la constelación Hidra. Unos astrónomos que estaban confirmando un candidato a planeta identificado por el Satélite de Sondeo de Exoplanetas en Tránsito encontraron posteriormente otros dos mundos orbitando la estrella. El planeta más exterior, GJ 357 d, es especialmente intrigante para los científicos porque recibe tanta energía de su estrella como Marte recibe del Sol.

Crédito: Centro de Vuelo Espacial Goddard de la NASA

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Illustration depicting one interpretation of planet GJ 357 b.

Credit: NASA's Goddard Space Flight Center/Chris Smith

Illustration depicting one interpretation of planet GJ 357 c.

Credit: NASA's Goddard Space Flight Center/Chris Smith

Illustration depicting one interpretation of planet GJ 357 d.

Credit: NASA's Goddard Space Flight Center/Chris Smith

Illustration depicting one interpretation of planet GJ 357 d.

Credit: NASA's Goddard Space Flight Center/Chris Smith

Illustration depicting a 360-degree rotation of GJ 357 b. A 4K still image is also available for download.

Credit: NASA's Goddard Space Flight Center/Chris Smith

Illustration depicting a 360-degree rotation of GJ 357 c. A 4K still image is also available for download.

Credit: NASA's Goddard Space Flight Center/Chris Smith

Illustration depicting a 360-degree rotation of GJ 357 d. A 4K still image is also available for download.

Credit: NASA's Goddard Space Flight Center/Chris Smith

This diagram shows the layout of the GJ 357 system. Planet d orbits within the star’s so-called habitable zone, the orbital region where liquid water can exist on a rocky planet’s surface. If it has a dense atmosphere, which will take future studies to determine, GJ 357 d could be warm enough to permit the presence of liquid water.

Credit: NASA's Goddard Space Flight Center/Chris Smith

Versions of this animation with Spanish labels are also available for download.