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TESS finds its first planet in the earth's size

  TESS finds its first terrestrial planet
The Artist's perception of HD 21749c, the first terrestrial planet found by NASA's Transiting Exoplanet Survey Satellite (TESS), as well as its siblings, HD 21749b, a hot sub-Neptune great world. Credit: Robin Dienel, authorized by the Carnegie Institution for Science

A nearby system hosts the first Earth Size Planet discovery of NASA's Transiting Exoplanet Survey Satellite, as well as a warm sub-Neptune world, according to a new paper from a team of astronomers including Carnegie's Johanna Teske, Paul Butler, Steve Shectman , Jeff Crane and Sharon Wang.

. It is so exciting that TESS, which was launched about a year ago, is already a game changer in the planet hunting industry,

"Teske, who is the second author of the magazine, said." The spacecraft examines the sky and we work with the TESS follow-up group to flag potentially interesting targets for further observations on ground-based telescopes and instruments. "

One such tool, the Planet Finder Spectrograph on the Magellan II telescope at the Carnegie's Las Campana Observatory in Chile, was an important part of this effort, which helped to confirm the TESS signal Planetary character and to measure the mass of the newly discovered sub-Neptune. PFS-built by Shectman and Crane with a method pioneered by Butler and his co-workers working on a technique called the radial velocity method, which is currently the only way astronomers to measure the masses of individual planets, without any known masses it is very challenging to determine a planet's density or its general chemical composition.

This method takes advantage of the fact that the gravity of a star does not affect the planet that orbits it, but the gravity of the planet also affects the star in turn. The PFS enables astronomers to discover these small angles that the earth's gravity induces in the star's orbit.

"PFS is one of the only instruments in the Southern Hemisphere that can make these types of measurements," Teske added. "So it will be a very important part of further characterizing the planets found by the TESS mission."

With an orbit that takes about 36 days to complete, the sub-Neptune HD 21749b has the longest period of any of the TESS discoveries published so far. Because of the technology used by TESS, it is anticipated that most of the planets that the mission finds will have cycles of less than 10 days, so HD 21749b is unusual in this regard. In fact, this also made the detection of the planet in TESS data an extra challenge.

"There was a lot of detective work involved, and the right people were there at the right time," says lead author Diana Dragomir of the MIT's Kavli Institute of Astrophysics and Space Research. "But we were lucky, and we caught the signals, and they were really clear."

Its host star has about 80 percent of our sun's mass and is about 53 light-years away from the earth. HD 21749b has about 23 times the earth's mass and a radius of about 2.7 times the earth's. Its density indicates that the planet has a significant atmosphere, but is not rocky, so it can potentially help astronomers understand the composition and evolution of the cooler sub-Neptune planet's atmosphere.

Exciting is the longer period's sub-neptune plan in this system not alone. It has a sibling plan, HD 21749c, which takes about eight days to pave the host star and is much smaller like the Earth.

"Measuring the exact mass and composition of such a small planet will be challenging, but important for comparing HD 21749c to Earth," says Wang. "Carnegie's PFS team continues to collect data on this object with this goal in mind. "

Thanks to TESS, astronomers can for the first time measure the masses, atmospheric compositions and other properties of many smaller exoplanets. Although small exoplanets are common in our galaxy, there is still much to learn about their diversity and how they compare with the planets in our own solar system. "19659006]" For stars that are very close and very bright, we waited to find up to a few dozen earth-sized planets, "said Dragomir." And here we are – this would be ours first, and it is a milestone for TESS. It paves the way to find smaller planets around even smaller stars, and those planets may be habitable. "

An exoplanet with an 11 hour orbit

More information:
Diana Dragomir et al., TESS delivers its first earth plan and a warm sub-Neptune, Astrophysical Journal (2019). DOI: 10.3847 / 2041-8213 / ab12ed

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TESS finds its first ground-level plan (2019, April 15)
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