Jul 29 2019
A research work published in The Astrophysical Journal Letters reports that scientists from Dartmouth College have found a planet revolving around one of the brightest known young stars. The star, aged about 45 million years, and its planet could offer intriguing insights into the formation of planetary bodies.
Data on the brightness of a young star led to the discovery of exoplanet DS Tuc Ab. Red arrows mark “transits” where the planet crossed between Earth and the planet’s host star. The large, smooth variations are caused by the star, a result of its youth. (Image credit: Elisabeth Newton)
The planet is an exoplanet since it is outside of the solar system and was discovered as part of NASA’s Transiting Exoplanet Survey Satellite (TESS) mission. Although numerous exoplanets have already been discovered, only very few of them have been found to circle comparatively young stars.
DS Tuc Ab, the exoplanet detected as part of the Dartmouth study, can be regarded as a “pre-teen” with respect to planetary time. Although the planet is not growing anymore, due to its young age, it is still experiencing quick changes such as loss of atmospheric gas due to the radiation emitted from its host star.
Millions or billions of years could be needed for planets to attain maturity. It is not possible to observe this process in real time; hence, scientists are looking for planets around young stars to observe the process in action and gain insights into the formation and evolution of planets.
One of the overall goals of astronomy is understanding the big picture of how we got here, how solar systems and galaxies take shape and why. By finding solar systems that are different from our own—especially young ones—we can hope to learn why Earth and our own solar system evolved in the ways that they did.
Elisabeth Newton, Assistant Professor of Physics and Astronomy, Dartmouth College
The size of DS Tuc Ab is nearly six times that of Earth and lies between the sizes of Neptune and Saturn. Due to its size, it is possible that its composition is similar to that of the giant planets in the solar system. With two suns, the exoplanet completes one full revolution around its main star within just eight days.
In November 2018, the planet was initially detected by NASA satellite. In March 2019, the Dartmouth team confirmed the observation with the help of data from NASA’s Spitzer Space Telescope and other space- and ground-based observatories, for example, the South African Large Telescope (SALT).
The planet is located nearly 150 light-years away from Earth, where 1 light-year measures somewhat less than 6 trillion miles.
“We were really excited when we confirmed this discovery because the planet orbits such a bright, well-known young star. Our whole team worked together to learn everything we could about this solar system,” stated Newton, who headed a group of researchers from the University of North Carolina at Chapel Hill, the University Texas at Austin, and other research centers from across the globe.
NASA’s TESS mission has been using the transit method to search for planets around stars in the vicinity. The method involves detecting the obstruction of light when a planet passes between Earth and its host star. Then, scientists examine observations from other telescopes to confirm the finding.
The star’s brightness lets us study the planet in detail because the more photons you have the better statistics you have. A discovery of this sort with such a unique age and an unusual planet size would not be possible without TESS.
Elisabeth Newton, Assistant Professor of Physics and Astronomy, Dartmouth College
Newly formed planets are larger initially and are considered to turn smaller eventually as they cool down and lose atmosphere. Since this planet is still in its formation stage, the researchers believe that atmosphere evaporation can be detected in real time.
Gaining insights into this process could help researchers foretell what could happen to the exoplanet over the next billions of years. It can also be used to understand the way atmospheric escape might have had an impact on older planets, including Earth.
“We hope that by seeing this planet’s atmosphere, we can provide a snapshot of what planets look like at a young age,” stated Newton.
The TESS satellite was launched on April 18th, 2018. NASA reports that the TESS mission will study 200,000 of the brightest stars in the vicinity of the sun to look for transiting exoplanets, such as those that could support life.
Although the size of DS Tuc Ab is known, the researchers are not aware of its overall mass. This makes it difficult for the researchers to presently tell about the density and composition of the exoplanet. The star’s immense brightness could enable future studies to measure the mass of the exoplanet or determine the molecular composition of its atmosphere.