Planet hunter TESS finds more potentially habitable worlds

NASA’s planet-hunting satellite TESS has been hard at work lately, discovering a bevy of exoplanets, some of which could be potentially habitable.

Firstly, TESS discovered three exoplanets in orbit around the star UCAC4 191-004642. The planets are small and temperate and the system is relatively close to Earth, making it easier for future experiments to determine if the planets have atmospheres by using tools like the upcoming James Webb Telescope.

In addition, scientists also used TESS to examine GJ 357 b, an exoplanet they had detected by observing a pattern of dimming of star GJ 357. The dimming occurs when the planet passes between Earth and the star. The planet is about 20% bigger than Earth and has a high temperature of 490 degrees Fahrenheit (254 degrees Celsius), making it a “hot Earth.”

But in the course of investigating the planet, the researchers found something unexpected — two more planets, one of which is within the star’s habitable zone.

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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. NASA's Goddard Space Flight Center/Chris Smith

The furthest planet in the system, GJ 357 d, is a prime candidate for further exploration. “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,” co-author Diana Kossakowski of the Max Planck Institute for Astronomy in Heidelberg, Germany, said in a statement. “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.”

If the planet does not have an atmosphere it would be extremely cold, with an equilibrium temperature of minus 64 degrees Fahrenheit (minus 53 degrees Centigrade). It is hefty, weighing in at 6.1 times the mass of the Earth, but it is closer to its star than the Earth is to the Sun, at about 20% of the distance. Scientists aren’t sure what the planet is composed of or what size it is, but it is possible rocky and one or two times the size of the Earth.

The findings are published in the journal Astronomy & Astrophysics.

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