12 January 2020
A NASA satellite has discovered an Earth-sized world within its star's "habitable" area -- where liquid water could possibly exist.
The world is known as an exoplanet. This term is used for planets that orbit a star outside of our own solar system.
NASA's Transiting Exoplanet Survey Satellite, or TESS, made the discovery. TESS was launched in 2018 to expand on the work of earlier exoplanets that space telescopes had discovered. Exoplanets are hard for telescopes to identify; the bright lights of the stars they orbit can hide them.
TESS contains four individual cameras that search for drops in light levels. This may be linked to planetary movements. Scientists then attempt to confirm the presence of worlds and try to estimate the size and orbit of the planets.
The newly found planet, called "TOI 700 d," is about 100 light years away from Earth, NASA's Jet Propulsion Laboratory said. It is about 20 percent larger than Earth. TOI 700 d is one of three planets orbiting a star known as TOI 700.
The discovery was announced during a recent meeting of the American Astronomical Society in Honolulu, Hawaii.
Being in a star's habitable area means that a planet has temperatures that could permit liquid water to exist on the surface. Since water is necessary for life as we know it, the presence of liquid means it could possibly support life.
Astronomers have not yet been able to measure TOI 700 d's mass. Such measurements will be necessary to estimate whether it is a rocky planet like Earth, or a gassy one like Neptune.
Elisa Quintana is an astronomer at NASA's Goddard Space Flight Center in Greenbelt, Maryland. She told Nature magazine that few Earth-sized planets have been discovered in habitable areas. She says this makes the latest find "exciting."
Scientists say they confirmed the planet information using NASA's Spitzer Space Telescope. They have modeled the planet's possible environments to help support future observation activities.
The modeling team for TOI 700 d is led by Gabrielle Engelmann-Suissa. She is a visiting research assistant at Goddard. She said in a statement that the modeling process is very important to help learn more about conditions on TOI 700 d as more data is collected.
"It's exciting because no matter what we find out about the planet, it's going to look completely different from what we have here on Earth," Engelmann-Suissa said.
Another exoplanet discovery was also discussed at the Astronomical Society meeting. Scientists announced that TESS had found its first exoplanet orbiting two stars instead of one.
The planet is called TOI 1338 b, which lies about 1,300 light years away from Earth, NASA said. It is about seven times larger than Earth. That makes it between the sizes of Neptune and Saturn.
Astronomers have estimated that one of the planet's stars is about 10 percent more massive than our sun. The other star is cooler, less bright and only one-third of our sun's mass. The two stars orbit each other every 15 days.
These kinds of planets, called circumbinaries, are difficult to identify. So far, scientists have confirmed about 24 of them. The first such discovery came in 1993.
Overall, more than 3,500 exoplanets have been discovered over the past 20 years.
I'm Bryan Lynn.
Bryan Lynn wrote this story for VOA Learning English, based on reports from NASA, Agence France-Presse and Nature. Ashley Thompson was the editor.
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Words in This Story
habitable – n. able to be lived in