Tiny briefcase-sized satellite spots an exoplanet and sets a new record

A miniature NASA satellite called ASTERIA has set a new record of being the smallest satellite ever to detect an exoplanet.

ASTERIA spotted the exoplanet 55 Cancri e, roughly twice the size of Earth and orbiting close enough to its star to be exceedingly hot on its surface. Scientists already knew there was a planet in this location, so they searched for it using ASTERIA as a way to test the small satellite’s capabilities, not expecting that it would be possible to actually detect the planet.

But to their surprise and delight, ASTERIA was able to perform a marginal detection. “We went after a hard target with a small telescope that was not even optimized to make science detections — and we got it, even if just barely,” Mary Knapp, the ASTERIA project scientist at MIT’s Haystack Observatory and lead author of the study, said in a statement. “I think this paper validates the concept that motivated the ASTERIA mission: That small spacecraft can contribute something to astrophysics and astronomy.”

The super-Earth exoplanet 55 Cancri e, depicted with its star in this artist's concept, likely has an atmosphere thicker than Earth's but with ingredients that could be similar to those of Earth's atmosphere.
The super-Earth exoplanet 55 Cancri e, depicted with its star in this artist’s concept, likely has an atmosphere thicker than Earth’s but with ingredients that could be similar to those of Earth’s atmosphere. NASA/JPL-Caltech

ASTERIA was not even originally intended to be a scientific instrument. It was built as a technological demonstration of how a small satellite could remain focused on a distant point for a long period of time, as was only intended to run for 90 days at first. But its mission was extended, and the tiny satellite was able to detect the exoplanet using the transit method, in which the brightness of a distant star is observed. If that brightness dips at regular intervals, scientists can infer there must be a planet passing between the star and us.

“Detecting this exoplanet is exciting because it shows how these new technologies come together in a real application,” said Vanessa Bailey, the principal investigator for ASTERIA’s exoplanet science team at NASA’s Jet Propulsion Laboratory. “The fact that ASTERIA lasted more than 20 months beyond its prime mission, giving us valuable extra time to do science, highlights the great engineering that was done at JPL and MIT.”

ASTERIA spacecraft prepared for mass-properties measurements
Left to right: Electrical Test Engineer Esha Murty and Integration and Test Lead Cody Colley prepare the ASTERIA spacecraft for mass-properties measurements in April 2017 prior to spacecraft delivery ahead of launch. ASTERIA was deployed from the International Space Station in November 2017. NASA/JPL-Caltech

Although CubeSats like ASTERIA will never replace dedicated planet-hunting missions like TESS, the research does show the enormous potential of these tiny satellites.

“This mission has mostly been about learning,” said Akshata Krishnamurthy, co-investigator and science data analysis co-lead for ASTERIA at JPL. “We’ve discovered so many things that future small satellites will be able to do better because we demonstrated the technology and capabilities first. I think we’ve opened doors.”

The findings will soon be published in the Astronomical Journal.

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