Credit:ESO/L. Calçada/P. Delorme/Nick Risinger (skysurvey.org)/R. Saito/VVV Consortium
Astronomers have discovered a planet which is not orbiting a star, challenging our earliest definitions of what makes a planet.
The absence of a nearby star to obscure the new planet, named CFBDSIR2149, has enabled scientists to make fairly detailed observations, despite it being over 100 light years away from Earth. Using the European Southern Observatory’s Very Large Telescope (VLT – unsurprisingly named for an instrument 8m in diameter), they estimate that it is between four and seven times the mass of Jupiter, and between 50 million and 120 million years old. The age of the planet was of particular interest to scientists, as it is relatively young next to our 4.6 billion year-old sun. By comparing the radiation spectrum of the planet with known data and atmospheric models, astronomers estimate that that planet’s temperature is about 430° Celsius.
Free-floating objects such as this have been identified before, but scientists have never been able to confirm whether they had the requisite mass, temperature and age to be termed a planet. Instead they were classified as brown-dwarfs: failed stars, which were too small to sustain fusion reactions in their cores.
The formation of free-floating planets remains a mystery, with scientists unsure whether they were knocked out of their original orbit around a star, or originate from collapsing clouds of gas and dust. The discovery of more isolated planets will hopefully shed light on the issue and may further our understanding of the formation of stars and planets in other star systems.
http://arxiv.org/abs/1210.0305
