Skip to Content
77 Mass Ave

And then there were three

NASA’s sky survey has discovered another new planet.
February 27, 2019
Adrian Pelletier | Unsplash

NASA’s Transiting Exoplanet Survey Satellite, or TESS, has discovered a third small planet outside our solar system, scientists announced in January.

The new planet, named HD 21749b, orbits a bright dwarf star about 53 light-years away, in the constellation Reticulum, and has the longest orbital period of the three planets so far identified. HD 21749b journeys around its star in a leisurely 36 days, while the “super-Earth” called Pi Mensae b has a 6.3-day orbit and the rocky world known as LHS 3844b speeds around its star in just 11 hours. All three were discovered in the first three months of TESS observations.

The MIT-led TESS mission is monitoring the sky, sector by sector, training its four onboard cameras on each one for 27 days. The idea is to zero in on momentary dips in the light of about 200,000 nearby stars—an indication that a planet has passed in front of them.

NASA’s TESS mission, which will survey the entire sky over the next two years, has already discovered three new exoplanets around nearby stars.
NASA's Goddard Space Flight Center, edited by MIT News

The surface of the new planet is likely around 300 °F (149 °C)—relatively cool given its proximity to its star, which is less bright than the sun.

“It’s the coolest small planet that we know of around such a nearby star,” says MIT postdoc Diana Dragomir, who led the discovery.

HD 21749b is about three times the size of Earth—and a whopping 23 times as massive. But it’s probably not rocky, and therefore not habitable. “The planet probably has an atmosphere composed of heavy molecules, such as water,” says Dragomir.

Serendipitously, the researchers also detected evidence of a second planet in the same planetary system, with a shorter, 7.8-day orbit. If confirmed, it could be the first Earth-size planet discovered by TESS.

Keep Reading

Most Popular

This startup wants to copy you into an embryo for organ harvesting

With plans to create realistic synthetic embryos, grown in jars, Renewal Bio is on a journey to the horizon of science and ethics.

VR is as good as psychedelics at helping people reach transcendence

On key metrics, a VR experience elicited a response indistinguishable from subjects who took medium doses of LSD or magic mushrooms.

This nanoparticle could be the key to a universal covid vaccine

Ending the covid pandemic might well require a vaccine that protects against any new strains. Researchers may have found a strategy that will work.

Stay connected

Illustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.