Less than a year after the launch, TESS is already looking for bizarre worlds

SEATTLE – The next generation of exoplan hunters comes to their own. In the first four months of observation, NASA's satellite satellite survey for transit exoplanets (TISS) has already found eight certified planets, some of which are not similar to what astronomers have seen before.

"The data flow is already in progress," said TESS chief researcher George Ricker of the MIT at a press conference at the American Astronomical Society on January 7.

TESS began in April and began to observe science in July (SN: 5/12/18, p. 7). It was designed as a continuation of the feasible space telescope Kepler, which began to darken in October after almost a decade of observation (SN Online: 10/30/18). Like Kepler, TESS searches for planets by observing falls in starlight when the planets cross or cross their stars.

Unlike Kepler, who has been constantly looking at a single part of the sky for many years, TESS scans a new segment of the sky every month. For more than two years, TESS will cover the entire 360 ​​degrees sky visible from Earth's orbit.

In the first four segments, TESS has already spotted eight certified planets and more than 320 unconfirmed candidates, said Xu Chelsea Huang of MIT. And more of them are quite weird.

Take the third planet, HD 21749b. Only 52 light years away has the lowest temperature known for the planet circling around the bright, near stars, astronomers at a meeting and an article published on arXiv.org reported on January 1st.

For this reason, he is a great candidate for further observations with future telescopes, such as the James Webb Space Telescope, to be launched in 2021. Webb will use star filtering through planets such as this to measure the properties of these atmospheres and to find signs. life (SN: 4/30/16, p. 32).

"If we want to study the atmosphere of cold planets, this is the one we start with," Huang said.

"Cool" is a relative term. This planet is still probably too hot and the life of the host. Its orbit lasts 36 days on Earth, which is the longest known orbital period for planets crossing bright stars in 100 light-years of the sun.

It leaves this at a distance from the star, which is supposed to warm the surface of the planet to around 150 ° C, too hot for running water. At 2.84 times the Earth's size and 23.2 times Earth's mass, its density indicates that it must have a dense atmosphere, unlike earthly life-support.

But it's still worth checking, says astronomer Diana Dragomir of MIT, a member of the TESS team. Despite its heat, this planet is "cold" compared to most of the burning worlds whose atmospheres can now be tested by astronomers so close that it is so similar to the Earth's system. Smaller, colder and more similar Earth worlds are few and far between them and may not circulate around such bright stars.

Searching for longer planets "helps you explore the diversity of planets that are out there," says Paul Dalba of the University of California, Riverside, who studies the atmosphere of exoplanets but was not involved in the discovery of TESS. Since TESS uses such a short time to watch each segment of the sky, astronomers expect that most of its planets are shorter than the Earth's moon. "The fact that we are getting this longer period, which in my opinion is very exciting, shows that TESS is not only in the shortest possible time."

The other planets in the first TESS pull are equally exotic. TESS's first finding, Pi Mensae c, was reported in September (SN Online: 18.9.18). The planet circulates around its star every 6.27 days and is approximately 2.14 times larger than the Earth's mass and 4.8 times the Earth's mass, giving it a density similar to pure water.

Unusual thing about this super Earth is the company that keeps it, Huang said. Earlier observations showed that the star Pi Mensae also has a planet that is 10 times larger than the mass of Jupiter, which circulates every 5.7 years. This planet, Pi Mensae b, spins on a wild eccentric orbit, fluctuates between the distance of the Earth and the distance from Jupiter from its star.

"This is the most extreme system we know, which has this type of architecture," Huang said.

Theories about how the planets develop such cumbersome orbits show that this super-Jupiter should extract Pi Mensae c from the system (SN: 5/12/18, p. 28). "We are really surprised that the inner super-Earth has actually spent this disturbing event," Huang said. "This is the secret that we really want to understand."

The second planet found by TESS, LHS 3844b, has radium only 1.3 times Earth. However, he is constantly moving around his planet every 11 hours, so he has a surface temperature of about 540 ° C, Huang said. "It's probably a world of lava."

TESS completed about one twelfth of the first sky survey, but Ricker is already preparing proposals to extend the initial two-year mission. Orbita TESS is stable due to the gravity of the Moon, so no fuel is needed to stay in place. The fuel on board, used to change the direction of telescopic points, is sufficient for 300 years.

"Orbita itself has been designed to be extremely stable over time periods of decades to hundreds," said Ricker. "TESS will be a truly important part of our astronomical efforts for the next decade and for the future."