Credit: NASA/MIT/TESS
The Transiting Exoplanet Survey Satellite (TESS) took this snapshot of the Large Magellanic Cloud (right) and the bright star R Doradus (left) with just a single detector of one of its cameras on Tuesday, Aug. 7. The frame is part of a swath of the southern sky TESS captured in its “first light” science image as part of its initial round of data collection.

NASA’s successor to the Kepler mission, the Transiting Exoplanet Survey Satellite (TESS), is already paying dividends. The satellite was only launched in April and spent time undergoing commissioning and calibration. But it has now started its science mission, and researchers have already discovered two new exoplanets.

NASA/MIT/TESS.
Here is the full 1st-light image from TESS, captured in the southern sky during one 30-minute period on on August 7. Created by combining the view from all 4 of its cameras, this 1st-light image from TESS represents the first observing sector that will be used for identifying planets around other stars. Notable features in this swath of the southern sky include the Large and Small Magellanic Clouds and a globular cluster called NGC 104, also known as 47 Tucanae. The brightest stars in the image, Beta Gruis and R Doradus, saturated an entire column of camera detector pixels on the satellite’s second and fourth cameras. Image via

The space telescope is on a two-year, $337 million mission to expand astronomers’ known catalog of so-called exoplanets, worlds circling distant stars. Like Kepler, TESS will be watching for transits, which occur when a planet passes in front of its star from the observer’s perspective, causing a periodic and regular dip in the star’s brightness.

While the two newly discovered planets are too hot to support life, TESS Deputy Science Director Sara Seager expects many more such discoveries.

Both exoplanets are still candidates, which means astronomers have yet to confirm their existance—but experts are already actively vetting the preliminary results.

The first exoplanet candidate was announced on September 19 and orbits a star called Pi Mensae, 60 light years away from Earth. It orbits its star every 6.3 days and seems to have a density similar to water.

The scientists have used TESS data to discover a new planet around the star Pi Mensae, also known as HD 39091, which is located about 59.5 light-years from Earth in the constellation Mensa, the table. Pi Mensae is a yellow dwarf star like the sun and the second-brightest among stars known to have transiting exoplanets.

Image: Science and Engineering Research Council J survey/C. X. Huang et al., 2018
Image showing host star Pi Mensae (big black dot), around which the new planet was discovered. The red lines show the boundary of the TESS aperture.

Combining the newfound planet’s mass and radius shows it has a similar density to pure water, “though of course we should not imagine the planet to be a globe of water,” the TESS team writes. Instead, it probably has a core made of iron and rock, surrounded by an ocean or atmosphere of lighter materials like water, methane, hydrogen and helium.

TESS will scan a much larger region of the sky than Kepler did – and one that is closer to Earth. But TESS can really be thought of as the first half of a Kepler-like program. Since it will help find a lot of planets, including a few that may be close enough to be imaged by existing hardware. It will lay the groundwork for the giant telescopes that are currently under construction, as well as the James Webb Space Telescope, which continues to inch toward launch. These will greatly expand our reach out into the galaxy, vastly increasing the distance at which we can image planetary atmospheres.