NASA's planet hunting satellite found another potentially habitable earth-sized planet

Pablo Tucker
January 7, 2020

NASA's planet-looking mission TESS has discovered its first doubtlessly liveable exoplanet the dimensions of Earth-orbiting a star about 100 light-years from Earth, in response to the company.

If liquid water is on the planet's surface, it will heat up and evaporate, creating the presence of water vapor, broken down into hydrogen and oxygen, in the atmosphere.

"Before our work, oxygen at similar levels as on Earth was thought to be undetectable with NASA's James Webb Space Telescope", said Dr. Thomas Fauchez, an astronomer at NASA's Goddard Space Flight Center.

As science continues on its quest to find signs of life beyond planet Earth, the study of exoplanets - planets around other stars - is one of the fastest growing areas in astronomy, holding out the promise of essential clues towards understanding whether and where life might exist elsewhere in the Universe.

Until about a decade ago, only two habitable zone planets of any size were known to astronomers: Earth and Mars. It is exclusively about 40% of our solar mass and measurement, with half of the surface temperature. TOI 700 d is the first Earth-size habitable-zone world discovered by TESS.

A few other similar planets have been discovered before, notably by the Kepler Space Telescope, but this is the first discovered by TESS, which was launched in 2018.


TOI 700 d, the outermost known planet in the system, is the really intriguing one.

All of the planets are believed to be tidally locked to TOI 700, meaning they rotate once per orbit so that one side is constantly bathed in daylight.

Earth completes an orbit around the sun every 365 1/4 days.

And in-depth observations of light that has streamed through TOI 700 d's atmosphere on its way to Earth could tell us a great deal about conditions on the alien world's surface, which remain a total mystery at the moment.

The findings were declared in the 235 meeting of the American Astronomical Society (AAS) in Honolulu Monday.

The TESS satellite monitors sectors of the sky for 27 days at a time, allowing the satellite to track changes in the brightness of a star caused by an orbiting planet crossing in front of it.


The researchers use signals called spectral lines, which are detected from the passage of starlight through the planet's atmosphere to project what the planet's surface would look like. The second planet, c, is considered to be gaseous and between the size of Earth and Neptune, completing an orbit every 16 Earth days.

"Spitzer saw TOI 700 d transit exactly when we expected it to", Rodriguez added.

Our own atmosphere supports a liquid ocean on Earth now because our star is quite big and brighter than TOI-700. That model of the atmosphere has a deep layer of clouds on the star-facing side.

"Oxygen is one of the most exciting molecules to detect because of its link with life, but we don't know if life is the only cause of oxygen in an atmosphere", Schwieterman said. If we put the same quantity of greenhouse gases as we have on Earth on TOI-700 d, the surface temperature on this planet would still be below freezing.

Intriguingly, some researchers propose oxygen can also make an exoplanet appear to host life when it does not, because it can accumulate in a planet's atmosphere without any life activity at all.

The National Aeronautics and Space Administration (NASA) has explored another possibly habitable exoplanet. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA's Ames Research Centre in California's Silicon Valley; the Harvard-Smithsonian Centre for Astrophysics in Cambridge, Massachusetts; MIT's Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore.


"Someday, when we have real spectra from TOI 700 d, we can backtrack, match them to the closest simulated spectrum, and then match that to a model", said Gabrielle Engelmann-Suissa, a Universities Space Research Association visiting research assistant at NASA's Goddard Space Flight Center.

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