This article was originally featured in The Conversation.
Imagine you’re a farmer searching for eggs in the chicken coop–but instead of a chicken egg, you find an ostrich egg, much larger than anything a chicken could lay.
That’s a little how our team of astronomers felt when we discovered a massive planet, more than 13 times heavier than Earth, around a cool, dim red star, nine times less massive than Earth’s Sun, earlier this year.
The smaller star, called an M star, is not only smaller than the Sun in Earth’s solar system, but it’s 100 times less luminous. Such a star should not have the necessary amount of material in its planet-forming disk to birth such a massive planet.
The Habitable Zone Planet Finder
Over the past decade, our team designed and built a new instrument at Penn State capable of detecting the light from these dim, cool stars at wavelengths beyond the sensitivity of the human eye–in the near-infrared–where such cool stars emit most of their light.
Attached to the 10-meter Hobby-Eberly Telescope in West Texas, our instrument, dubbed the Habitable Zone Planet Finder, can measure the subtle change in a star’s velocity as a planet gravitationally tugs on it. This technique, called the Doppler radial velocity technique, is great for detecting exoplanets.
“Exoplanet” is a combination of the words extrasolar and planet, so the term applies to any planet-sized body in orbit around a star that isn’t Earth’s Sun.
Thirty years ago, Doppler radial velocity observations enabled the discovery of 51 Pegasi b, the first known exoplanet orbiting a Sunlike star. In the ensuing decades, astronomers like us have improved this technique. These increasingly more precise measurements have an important goal: to enable the discovery of rocky planets in habitable zones, the regions around stars where liquid water can be sustained on the planetary surface.
The Doppler technique doesn’t yet have the…
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