The NASA planetary hunter finds a planet the size of Earth 53 light years away.
WASHINGTON: NASA's plant-hunting craft, launched last year, discovered a planet the size of Earth and a warm one the size of Neptune in a nearby star system.
The study published Monday in The Astrophysical Journal Letters reported on an Earth-sized planet called HD 21749c, which takes eight days to orbit its host star.
The host star of these two planets is approximately 80 percent of the Sun's mbad and is about 53 light-years away from Earth.
The Exoplanet Transit Survey Satellite (TESS), launched on April 18, 2018, is the last NASA satellite to search for planets outside of our solar system.
It will control the brightness of more than 200,000 stars over a period of two years, observing temporary drops in brightness caused by planetary transits.
In addition, a tool called Planet Finder Spectrograph (PFS) installed at an observatory in Chile has been used to confirm the planetary nature of the TESS signal and to measure the mbad of newly discovered exoplanets.
"Measuring the exact mbad and composition of such a small planet will be important to compare HD 21749c with Earth," said Sharon Wang, an astronomer at the Carnegie Institution in Washington.
Astronomers can measure the mbades, atmospheric compositions and other properties of many smaller exoplanets for the first time, thanks to TESS and PFS.
"For stars that are very close and very bright, we expect to find up to a couple of dozen planets the size of Earth," said Johanna Teske, also a Carnegie researcher.
"This would be our first, and it is a milestone for TESS.
It sets the path to find smaller planets around even smaller stars, and those planets can be potentially habitable, "said Teske.
Astronomers also discovered in the star system a sister planet HD 21749b, approximately 23 times the mbad of Earth, but less mbadive than Neptune.
It has a radius of approximately 2.7 times that of Earth.
HD 21749b has an orbit that takes approximately 36 days to complete, which is the longest period of any of the TESS discoveries published so far, according to the study.
Its density indicates that the planet has a substantial atmosphere, but it is not rocky, so it can help astronomers to understand the composition and evolution of the colder atmospheres of the subneptune planet.
Small exoplanets are common in our galaxy, but there is still much to learn about their diversity, according to the researchers.
TESS will study more than 90 percent of the sky and will transmit observations to Earth every 13.5 days. (Xinhua / APP)