Astronomers get best view yet of exoplanet in motion around its star

The Gemini Observatory has given us our best view yet of an exoplanet moving in its orbit around a distant star

An artist's impression of Beta Pictoris b in orbit around its star. Image Credit: ESO

An artist’s impression of Beta Pictoris b in orbit around its star. Image Credit: ESO

A team of astronomers, using the Gemini Observatory, has given us our best view yet of an exoplanet moving in its orbit around a distant star. A series of images captured between November 2013 to April this year shows the exoplanet Beta Pictoris b as it moves through one and a half years of its 22-year orbital period.

First discovered in 2008, Beta Pictoris b is a gas giant planet ten to twelve times the mass of Jupiter, with an orbit roughly similar to that of Saturn. It is part of a dynamic and complex system that includes comets, orbiting gas clouds, and an enormous debris disc that in our Solar System would extend from Neptune’s orbit to nearly two thousand times the Sun-Earth distance. Because the planet and debris disk interact gravitationally, the system provides astronomers with an ideal laboratory to test theories on the formation of planetary systems beyond ours.

The images in the series represent the most accurate measurements of the planet’s position ever made,” says Maxwell Millar-Blanchaer of the University of Toronto. “In addition, we’re able to see both the disk and the planet at the exact same time. With our combined knowledge of the disk and the planet we’re really able to get a sense of the planetary system’s architecture and how everything interacts.”

The research includes refinements to measurements of the exoplanet’s orbit and the ring of material circling the star, which shed light on the dynamic relationship between the two. It also includes the most accurate measurement of the mass of star Beta Pictoris to date and shows it is very unlikely that Beta Pictoris b will pass directly between us and its parent star.

“It’s remarkable that Gemini is not only able to directly image exoplanets but is also capable of effectively making movies of them orbiting their parent star,” says Chris Davis, astronomy division program director at the National Science Foundation, which is one of five international partners that funds the Gemini twin telescopes’ operation and maintenance. “Beta Pictoris is a special target. The disc of gas and dust from which planets are currently forming was one of the first to be observed and is a fabulous laboratory for the study of young planetary systems.”

Astronomers have discovered nearly two thousand exoplanets in the past two decades but most have been detected with instruments—like the Kepler space telescope—that use the transit method of detection: astronomers detect a faint drop in a star’s brightness as an exoplanet transits or passes between us and the star, but do not see the exoplanet itself. With Gemini Planetary Imager (GPI), astronomers image the actual planet—a remarkable feat given that an orbiting world typically appears a million times fainter than its parent star. This is possible because GPI’s adaptive optics sharpen the image of the target star by cancelling out the distortion caused by the Earth’s atmosphere – it then blocks the bright image of the star with a device called a coronagraph, revealing the exoplanet.

Laurent Pueyo, who is with the Space Telescope Science Institute and involved in the research, says: “It’s fortunate that we caught Beta Pictoris b just as it was heading back—as seen from our vantage point—toward Beta Pictoris,” he says. “This means we can make more observations before it gets too close to its parent star and that will allow us to measure its orbit even more precisely.”

In August 2015, the team announced its first exoplanet discovery: a young Jupiter-like exoplanet designated 51 Eridani b. It is the first exoplanet to be discovered as part of the GPI Exoplanet Survey (GPIES) which will target 600 stars over the next three years.

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