Stargazers at the Search for Extraterrestrial Life Institute (SETI) used the brand new Gemini Planet Imager to closely examine a star which is 100 million light years away in the constellation of Eridanus.
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“51 Eridani is only 20 million years old, a little more massive than our sun – a flawless target”, says James Graham, a professor at UC Berkeley and Project Scientist for GPI. “51 Eri was born 20 million years ago, 40 million years after the dinosaurs died out”.
“By targeting young stars, we can catch planets while they are hotter and brighter and can study how planets evolve over time”, says ASU astrophysicist Jennifer Patience, an associate professor in the School of Earth and Space Exploration and part of the GPI Exoplanet Survey Team.
“Many of the exoplanets astronomers have studied before have atmospheres that look like very cool stars”, study lead author Bruce Macintosh, a professor of physics in the Kavli Institute at Stanford University who led the construction of GPI, said in the release.
Furthermore, the faint nature of the planet, combined with its relatively close proximity to the star it orbits, makes it “the most Jupiter-like planet ever imaged – except, of course, that it’s so young, which is why we can see it”, he added.
An artist’s conception of 51 Eridani b. (If 51 Eridani b were in our solar system, it would orbit the sun between Saturn and Uranus, according to the Gemini Planet Imager.). Macintosh agrees. “It’s really the most Jupiter-ish thing ever imaged directly”, he says. Using GPI to study more young solar systems such as 51 Eridani, he said, will help astronomers understand the formation of our neighbour planets, and how common that planet-forming mechanism is throughout the universe. “This one looks like a planet”.
The apparent similarity strengthens the possibility that the system could harbour smaller planets like Earth located even closer to the star.
Imaging an exoplanet directly like this is incredibly hard; a planet’s host star is usually so luminous that it often washes out all nearby objects. Other directly-imaged planets are five times the mass of Jupiter or more. “We have special masks to block the light from the star and let us separate the planet from the star, and a very advanced adaptive optics system that can do a extremely good job fixing the turbulence in the earth’s atmosphere and the slight imperfections in the telescope that would hide a planet”.
The Gemini Planet Imager actually directly images the planets it discovers.
“We could quite easily have a planet with an Earth-like mass which simply cannot be seen using current technology”.
The gas giants in this solar system formed by building up a large core over a few million years and then pulling in a huge amount of hydrogen and other gasses to form an atmosphere.
Marois said 51 Eridani b is the first planet discovered with this technique that appears to have been formed the same way as planets in our own solar system – from tiny dust particles clumping together into rocks and eventually the core of a planet.
The new planet is also the first planet detected by the Gemini Planet Imager (GPI).
At the moment, astronomers have two different theories for how big planets formed. But the Jupiter-like exoplanets that have so far been discovered are much hotter than models have predicted, hinting that they could have formed much faster as material collapses quickly to make a very hot planet.
Its temperature is estimated to be about 427 Celsius, hot enough to melt lead. Jupiter is the largest planet in the solar system at 318 times the size of our Earth – imagine a planet twice that size.
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The researchers said they plan to begin observing 51 Eri b again in late September, when it emerges from behind the sun, in order to map out the exoplanet’s orbit.
