Astronomers Find ‘Young Jupiter’, the Smallest Planet Outside This Solar System Directly Seen By Telescope


Astronomers have found the smallest planet outside this solar system yet to be directly photographed by a telescope on Earth, a methane-shrouded gas giant much like a young Jupiter.

This newfound alien planet, called 51 Eridani b, orbits a star about 96 light-years from Earth in a planetary system that may be much like Earth’s own solar system. The discovery could shed light on how our solar system formed, scientists added.

Over the last 20 years, astronomers have confirmed the existence of more than 1,800 exoplanets, or alien planets around other stars. Many of these worlds are quite unlike any planets in Earth’s solar system. For example, so-called “hot Jupiters” are gas giants that orbit their host stars more closely than Mercury does the sun.

More than 1,000 of the exoplanets confirmed to date were discovered by NASA’s Kepler Space Telescope. Kepler indirectly finds planets by detecting a loss of starlight as a world passes in front of its star.

However, this new planet was discovered using the Gemini Planet Imager, an instrument on the Gemini South telescope in Chile, which directly detects exoplanets by looking for light from the worlds themselves.

“To detect planets, Kepler sees their shadow,” study lead author Bruce Macintosh, lead investigator on the Gemini Planet Imager and an astrophysicist at Stanford University in California, said in a statement. “The Gemini Planet Imager instead sees their glow, which we refer to as direct imaging.”

The scientists detailed their findings online Aug. 13 in the journal Science.

The smallest exoplanet photographed yet
Exoplanets are very dim compared to stars. As such, the exoplanets directly imaged until now were large, weighing at least five Jupiters. However, Gemini Planet Imager is one of a new generation of instruments designed specifically for discovering and analyzing small, faint planets orbiting close to their stars.

The imager, which is about the size of a small car, is perched atop the 26-foot (8 meters) Gemini South Telescope. It relies on deformable mirrors known as adaptive optics to sharpen images of stars, and then masks their light. Any remaining incoming light is then analyzed, with the brightest spots hinting at possible worlds.

Scientists focused on 51 Eridani, a yellow-white dwarf star about 1.5 times the mass and diameter of the sun located roughly 96 light-years away from Earth in the Southern Hemisphere constellation Eridanus. This star, also known as 51 Eri, is very young, only 20 million years old. In comparison, the sun is about 4.6 billion years old.

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SOURCE:, Charles Q. Choi

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