HomeScience and ResearchSpaceLooking for Earth-like planets: just Zoom in on a star

Looking for Earth-like planets: just Zoom in on a star

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Astronomers looking for Earth-like planets in other solar systems have made a significant breakthrough by taking a closer look at star surfaces.

An international team of researchers led by Yale astronomers Rachael Roettenbacher, Sam Cabot, and Debra Fischer developed a new technique that distinguishes between light signals from stars and signals from planets orbiting those stars by combining data from ground-based and orbiting telescopes.

An article describing the discovery has been accepted for publishing in the Astronomical Journal.

“Our techniques pull together three different types of contemporaneous observations to focus on understanding the star and what its surface looks like,” Roettenbacher, a Yale postdoctoral fellow and lead author of the paper, said in a statement.

“From one of the data sets, we create a map of the surface that allows us to reveal more detail in the radial velocity data as we search for signals from small planets.”

For decades, astronomers have utilized a process known as radial velocity to look for exoplanets in other solar systems. The motion of a star along an observer’s line of sight is referred to as radial velocity.

Astronomers hunt for variations in a star’s velocity that could be produced by an orbiting planet’s gravitational attraction. This information is provided by spectrometers, which examine the light emitted by a star and stretch it into a spectrum of frequencies that can be examined.

However, as astronomers raced to create methods for detecting Earth-like planets, they found a stumbling block that has slowed work for years. The energy emitted by stars creates a boiling cauldron of convecting plasma, which distorts radial velocity measurements and obscures signals from small, rocky planets.

Fortunately, a new generation of superior technology is addressing this issue. The EXtreme PREcision Spectrograph (EXPRES), designed and built by Fischer’s team at Yale, the Transiting Exoplanet Survey Satellite (TESS), and the Center for High Angular Resolution Astronomy (CHARA) interferometric telescope array are among these devices.

ThThe researchers used TESS data to rebuild the surface of Epsilon Eridani, a star in the southern constellation of Eridanus visible from most of Earth’s surface, for the new study. They then looked for starspots, which are colder portions of a star’s surface created by strong magnetic fields.

“With the reconstructions, you know the locations and sizes of spots on the star, and you also know how quickly the star rotates,” said Cabot. “We developed a method that then tells you what kind of signal you would see with a spectrometer.”

The researchers then compared their TESS reconstructions to data from Epsilon Eridani’s EXPRES spectrometer, which was obtained concurrently.

“This allowed us to directly tie contributions of the radial velocity signature to specific features on the surface,” Fischer said. “The radial velocities from the starspots match up beautifully with the data from EXPRES.”

The researchers also utilised another technique known as interferometry to find a starspot in Epsilon Eridani, making this the first interferometric detection of a starspot in a star similar to the Sun.

Interferometry is the process of combining individual telescopes to form a much larger telescope. The researchers employed the CHARA Array, the world’s biggest optical interferometer, which is located in California, to accomplish this.

Roettenbacher and her colleagues plan to use their new technology to directly photograph the whole surface of a star and quantify its contribution to radial velocity using sets of interferometric observations.

“Interferometric imaging is not something that is done for a lot of stars because the star needs to be nearby and bright. There are a handful of other stars on which we can also apply our pioneering approach,” Roettenbacher said.

Image Credit: Yale

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