New observations of the monster planet revolving Beta Pictoris

Multi-epoch observations of the β Pictoris b exoplanet. The planet was imaged in 2003 (left image) in the L' band (3.8 μm) in the plane of the circumstellar disk surrounding the star (not seen here). It was detected again October 2009 (middle) when it had moved to the other side of the star. The new observations made March 2010 at 2.18 μm are shown in the right panel. The planet has moved yet again relative to its position measured in 2009.

By Astronomy & Astrophysics, Paris, France
Published: March 4, 2011

Astronomy and Astrophysics is publishing new observations of the giant planet around Beta Pictoris. Discovered in 2009, this planet, called Beta Pictoris b, has now been detected again with the NaCo instrument on the Very Large Telescope (VLT). Astronomers find that the planet is moving around the star. They have also measured the mass and the effective temperature of Beta Pic b.

Astronomy & Astrophysics publishes new high angular resolution observations of the giant planet orbiting the star Beta Pictoris. Located 63.4 light-years from the Sun, Beta Pic is a young star about 12 million years old and 75 percent more massive than our Sun. Beta Pic is well-known for harboring an extended and structured circumstellar disk. It was actually the first star to have its disk directly imaged more than 25 years ago. In 2009, a giant planet was seen orbiting within the disk. With an orbital distance of 8 to 15 astronomical units (AU), Beta Pictoris b is the closest exoplanet to its star that has ever been imaged. This planet offers a new opportunity to study the planetary formation processes, in particular the interactions between the planets and their native disks.

An international team of astronomers observed the Beta Pic system using the VLT/NaCo instrument at 2.18 microns, previous observations having been made near 4 microns. They detected the planet again and compared these new observations with the previous ones. Combining all the data together shows that the planet is moving around the star, as expected from the previous data. Analyzing these new observations, the team was then able to measure the mass of the planet, around 7 to 11 times the mass of Jupiter, and its effective temperature, between 2000° and 3100° Fahrenheit (1100° and 1700° Celsius).

This new data already tell us something about the formation of the planet, especially because the system is young. The planet Beta Pic b is still warm, implying that it has retained most of the primordial heat acquired during its formation. If it has been formed in a similar way to the giant planets of our solar system, and its mass and temperature cannot be explained by some evolutionary models that hypothesize a total release of the energy acquired during the accretion of disk materials.

Forthcoming observations of Beta Pictoris b with NaCo and also with the next generation VLT instrument SPHERE should soon provide more details about its atmosphere and orbital properties and about the way this companion influences the surrounding disk material.