One of the coolest star-like bodies outside our solar system has been spotted orbiting a red dwarf star 40 light years from Earth.
UNSW Professor Christopher Tinney and a team of international space scientists announced their new result today at the European Week of Astronomy and Space Science. "It's certainly one of the coolest objects ever found," said Professor Tinney, one of the world's most successful "planet hunters", who has 30 extra-solar planet discoveries to his credit.
The researchers made their discovery while searching for cool planet-like objects called "brown dwarfs" in a major survey being undertaken at the United Kingdom Infrared Telescope in Hawaii. They happened to notice that the well-known red dwarf Wolf 940, first catalogued by the pioneering German astronomer Max Wolf ninety years ago, had a fainter companion that shared the same motion across the sky as Wolf 940.
The new brown dwarf has been dubbed Wolf 940B, after the red dwarf it orbits. The new object orbits its star five-times further than the distance at which Pluto orbits the sun and will take 18,000 years to complete a single orbit.
Brown dwarfs are not as bright as red dwarfs because their mass is too low to burn nuclear fuel. In stellar terms, they are relatively cool, dim and hard to see, so scientists use infrared telescopes to detect their faint glow.
The researchers believe that Wolf 940B is Jupiter-sized, but much denser, being 20 to 30 times heavier. It also has a higher temperature of around 300°C.
Professor Tinney says finding low mass objects like Wolf 940B is interesting because it sheds light on other cool-temperature low-mass objects like extra-solar planets - planets outside our solar system.
"At the Anglo-Australian Observatory we have found 30 planets orbiting other stars, but we don't actually see the planet itself. We don't see what its atmosphere looks like," he says. "Looking at systems like this gives us hints as to what the atmospheres of extrasolar planets might look like."
The researchers hope to point a bigger telescope at Wolf 940B to get more details on its atmosphere, which can be used to help build more reliable models. The team made its discovery using the United Kingdom Infrared Telescope and Gemini-North Telescope on Mauna Kea, Hawaii. The finding was confirmed using telescopes in Chile, the Canary Islands and the NASA's Spitzer Space Telescope.
Astronomers have identified around 300 or so "exoplanets" beyond our solar system since the first was found some 40 light years from the Sun, just over a decade ago.
The research finding will be published shortly in the Monthly Notices of the Royal Astronomical Society.
Dan Gaffney - 0411 156 015