Searching For Another Earth? Zoom In On A Star, Astronomers Say

An international team of astronomers have developed a technique to search for a planet similar to Earth, by closely observing the surface of stars

Representational image of Earth | Photo: Getty

New Delhi: Astronomers searching for planets similar to Earth in the planetary systems apart from our solar system have achieved a milestone — by closely observing the surface of stars.

The nature of the star in a planetary system, and the distance between a planet and the host star, determine whether life can be supported in that planet. 

An international team of researchers has developed a new technique to distinguish between light signals coming from stars and signals coming from planets orbiting those stars. The team, led by Yale astronomers, has used a combination of data from ground-based and orbiting telescopes.

The astronomers studied a star named Epsilon Eridani, to determine whether it hosts Earth-like planets.

The study was published in the Astronomical Journal recently.

Studying The Stars To Understand Planets

Signals from small planets and stars provide an idea of their surface pattern. The astronomers used a method known as radial velocity to search for exoplanets in other planetary systems. The velocity of a star along the line of sight of the observer is known as radial velocity. 

The astronomers used spectrometers to study the star's motion. A spectrometer is an optical instrument that is used to measure properties of light over a specific portion of the electromagnetic spectrum. The spectrometer stretches the light emitted by a star into a spectrum or a band of frequencies. Using this data, the astronomers studied how the gravitational pull of a planet orbiting around a star causes variations in the star's velocity.

Scientists Overcome A Challenge To Detect Earth-like Planets

The researchers used instruments such as EXtreme PREcision Spectrograph (EXPRES), designed by the Yale University astronomers, the Transiting Exoplanet Survey Satellite (TESS), and the Center for High Angular Resolution Astronomy (CHARA) interferometric telescope array — the world's largest optical interferometer. The interference of two beams of light is employed in an interferometer to make precise measurements. Also, separated telescopes are combined into a much larger telescope by interferometry. 

These instruments are able to compensate for the distortion in the measurements of radial velocity caused due to the boiling, convecting plasma created by the energy emitted from stars. 

Reconstructing The Surface Of Epsilon Eridani

They detected a starspot on Epsilon Eridani using interferometry. They observed the radial velocities from starspots to match up with data from EXPRES. 

Epsilon Eridani is a star in the southern constellation of Eridanus, and is visible from most regions of Earth. The astronomers searched for cooler regions on the surface of the star, known as starspots, caused by strong magnetic fields. They used TESS data to reconstruct the surface of the star, and studied the locations and sizes of starspots, the star's rotation, and signals emitted by the star. 

Using this technique, the astronomers found a connection between radial velocity signature and certain features on the star's surface. They obtained the direct image of the entire surface of the star, and determined its radial velocity contribution. Such information about a star will help scientists determine whether Earth-like planets exist in that planetary system.