TESS finds its First Earth-sized Planet

TESS finds its First Earth-sized Planet

TESS finds its First Earth-sized Planet
Image Credits: Phys.org

The Transiting Exoplanet Survey Satellite (TESS) was launched just a year ago but it has already found its first Earth-sized exoplanet.

Launched on 18 April 2018, TESS is expected to discover around hundreds of Earth-like planets during its two-year mission. Having said that, this duration could be extended if the satellite is able to successfully operate beyond its original mission. Scientists believe that this planet hunter will prove to be a game-changer in the planet-hunting business because of its immense potential.


The primary purpose of the Transiting Exoplanet Survey Satellite of NASA is to explore planets around the closest and brightest stars. It is located in a special orbit higher up, so it doesn’t suffer from atmospheric interference. Astrophysicists involved with the TESS mission expect the planet hunter to find more than a thousand planets smaller than Neptune and dozens of Earth-sized planets. The solar-powered spacecraft carries four 100-millimeter-wide cameras that provide wide fields of view. The cameras stare at a particular region of the sky for between 27 and 351 days each, before moving on to another area. However, TESS doesn’t work exactly as Kepler Space Telescope (NASA’s recently deceased space telescope) did.

TESS will focus on stars which are 30 to 100 times brighter than the ones observed by Kepler. The core functionality remains the same. TESS will observe stars and will look for dips in light intensity as a planet passes in front of the star. The amount of light reaching TESS decreases as it’s blocked by an orbiting planet. Although the basic goal of the satellite is to find exoplanets (of all kinds), its main priority is to find planets that are almost the same size as Earth. It is a much difficult task as larger planets are easier to spot than smaller ones. The teams behind TESS made sure that the satellite was right up to the task. Johanna Teske, the Second Author of the paper from the Carnegie Science Institute, talked about the spacecraft in the following words:

“It’s so exciting that TESS, which launched just about a year ago, is already a game-changer in the planet-hunting business. The spacecraft surveys the sky and we collaborate with the TESS follow-up community to flag potentially interesting targets for additional observations using ground-based telescopes and instruments.”

Planet Finder Spectrograph (PFS)

The Carnegie Institute for Science is an important figure in this discovery because they’re part of the consortium that operates the Las Campanas Observatory in Chile, where the Magellan Telescopes are located. The Magellan II Telescope has a unique instrument attached to it called the Planet Finder Spectrograph (PFS), which was developed and pioneered by the scientists involved in this study. The PFS helped the researchers to confirm the first two planets discovered by the satellite.

Discovery of The Earth-sized Planet

The observations of this particular star system have already revealed the existence of HD 21749b, which is about 23 times heftier than the Earth. Similarly, it is 2.7 times wider than our world. These numbers indicate that HD 21749b is most probably gaseous rather than being rocky. It has the highest orbital time (36 Earth days) among all the TESS planets discovered to date but the surface temperature of about 150o F makes it pretty much uninhabitable.

On the other hand, researchers discovered a new Earth-sized planet which has an orbital period of 8 days. It is significantly smaller than its sibling and is about the size of Earth. Sharon Wang, a Co-author of the study, mentioned that measuring the exact mass and composition of such a small planet will be a challenging task but is extremely vital for comparing HD 21749c to Earth. Meanwhile, Carnegie’s PFS team is continuing to collect data on this object with this goal in mind. Diana Dragomir, the Lead Author of the research from the Kavli Institute for Astrophysics and Space Research at MIT, referred to the significance of this discovery by saying,

“For stars that are very close by and very bright, we expected to find up to a couple dozen Earth-sized planets. And here we are—this would be our first one, and it’s a milestone for TESS. It sets the path for finding smaller planets around even smaller stars, and those planets may potentially be habitable.”

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