New Instrument EXPRES Ready to Search for Earth-like Planets

©Lowell University

Astronomers at Yale University, in collaboration with Lowell Observatory, are embarking on a search that will answer one of the oldest questions in astronomy: Are there planets similar to Earth orbiting other stars?

Lowell Observatory's Discovery Channel Telescope will gather light from stars and feed it into the Extreme Precision Spectrometer (EXPRES). A spectrometer splits light into different colors, similar to how shining light through a prism produces a rainbow. Astronomers will then analyze the light to search for the signatures of a planet. In this case, a change in the motion of the star along our line of sight -the radial velocity-, would indicate the presence of a planet.

The gravity of a star pulls the planet (or planets) towards it, but the planet does not fall into the star because of its circular motion. At the same time, the planet is actually pulling the star back. Big planets will give a big pull, causing a larger change in the radial velocity of the host star. The pull produced by small planets is very difficult to measure.

"Up until now the only planets we could detect with ground-based spectrometers were the bigger ones, the Saturns and Jupiters," said Yale professor Debra Fischer, whose team designed EXPRES. "We know the smaller planets are out there, but they've slipped through our nets."

Although astronomers have identified thousands of exoplanets in the past twenty years, none are true analogs of Earth. The revolutionary design of EXPRES means it is capable of finding planets about the size of Earth, in the "habitable zone" of stars similar in size, temperature, and age as our own Sun. Planets in the habitable zone are neither too hot or cold, meaning water can be in liquid state, forming lakes or even oceans, increasing the likelihood of finding life.

Designed and built at Yale University, EXPRES is now operational at the 4.3-m Lowell Observatory Discovery Channel Telescope (DCT) in Arizona. Astronomers at Lowell Observatory will benefit from this collaboration, being able to use EXPRES for their own research.

"The cutting edge technology of EXPRES, combined with Lowell's state of the art DCT is a real tour de force, enabling astronomers to make amazing new discoveries" said Lowell astronomer Dr. Joe Llama. "At Lowell we will complement the 100 Earth's project by using EXPRES to advance our knowledge in other areas of astronomy. Lowell projects include searching for signature of life in the atmospheres of exoplanets, studying the variations of stars like our Sun, and determining the conditions under which comets form".

With EXPRES now collecting data, astronomers are beginning to search for the first true Earth analog planet. Such a discovery would greatly advance our understanding about life in the Universe.

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