Jupiter’s ‘big brother’ has moon-forming dust disk

Earth’s moon was created by an early collision with another large planetary body. It was a “chip off the old block.” Mars captured its asteroidal moons as they passed by. But Jupiter made its own moons out of dust and gas remaining from its formation. Now, observations by astronomer Subhanjoy Mohanty of the Harvard- Smithsonian Center for Astrophysics and his colleagues provide the first direct evidence for a dusty disk around a distant planet that in mass would be Jupiter’s “big brother.”

“It is quite possible that moons or moonlets could form out of this disk, just as they have around the giant planets in our own solar system,” said Mohanty.

Mohanty presented the discovery June 5, 2006, in a press conference at the 208th meeting of the American Astronomical Society. Other members of the team are Ray Jayawardhana (University of Toronto), Nuria Huélamo (ESO) and Eric Mamajek (CfA).

The team studied a planetary mass object known as 2MASS1207-3932B, which is located about 170 light-years from Earth in the direction of the constellation Centaurus. 2M1207B, as it is abbreviated, orbits a tiny brown dwarf star at a separation of about 40 astronomical units, or 3.7 billion miles – comparable to the size of Pluto’s orbit. That separation is much larger than typical for binary brown dwarf systems. The wide separation may indicate that the duo formed in relative isolation, far from passing stars that could have pulled them apart.