extreme temperature evolution for WISE J0304-2705
August 6, 2014

Planet-Like Object May Have Once Been As Hot As A Star

redOrbit Staff & Wire Reports - Your Universe Online

An object that is currently cool as a planet might have spent much of its youth as hot as a star, according to a new research paper appearing in the latest edition of the journal Monthly Notices of the Royal Astronomical Society.

The object currently fluctuates between 200 and 300 degrees Fahrenheit (100 to 150 degrees Celsius), which is in between the temperatures of Earth and Venus, lead investigator David Pinfield of the University of Hertfordshire and his colleagues explained. However, it also shows evidence of a possible ancient origin, which means that it could have experienced a large change in temperature and might have been as hot as a star for millions of years.

Identified by Pinfield and his colleagues using NASA’s Wide-field Infrared Survey Explorer (WISE) observatory, a space telescope launched in 2009 that has captured images of the entire sky in mid-infrared light, the object has been dubbed WISE J0304-2705 and is a member of the recently established “Y dwarf” class.

WISE J0304-2705 joins 20 other Y dwarfs discovered to date, and while its current temperature is similar to planets, the object is not a rocky world like Earth. Instead, it is a large ball of gas similar to Jupiter. Furthermore, the team also dispersed the light it emits into a spectrum, which allowed them to learn more about its history.

Among the Y dwarfs discovered to date, WISE J0304-2705 is defined as 'peculiar' due to unusual features in its emitted light spectrum. The reason that it underwent such extreme evolutionary cooling is because it is “sub-stellar,” the authors said, which means that its interior never becomes hot enough for hydrogen fusion to occur.

Hydrogen fusion is the process which has kept our sun hot for several billion years, and without an energy source helping the planet maintain a stable temperature, it is inevitable that it would begin to cool down. If WISE J0304-2705 is an ancient object, then its temperature evolution would have been a four-stage process.

During the first stage, which would have lasted approximately 20 million years, the object would have been as hot as a star – reaching temperatures of at least 5,100 degrees Fahrenheit (2800 degrees Celsius). After roughly 100 million years, it would have cooled down to about 2,700 degrees Fahrenheit (1500 degrees Celsius).

In its third stage, after one billion years had passed, it would have been down to about 1,800 degrees Fahrenheit (1000 degrees Celsius). Ultimately, billions of years later, WISE J0304-2705 would have cooled to its current planetary temperature of just 200-300 degrees Fahrenheit (100-150 degrees Celsius).

“Our measurements suggest that this Y dwarf may have a composition and/or age characteristic of one of the Galaxy's older members,” Pinfield explained in a statement Tuesday. “This would mean its temperature evolution could have been rather extreme – despite starting out at thousands of degrees.”

WISE J0304-2705, which is located in the Fornax (Furnace) constellation, is reportedly as massive as 20-30 Jupiters combined, which the research team said is intermediate between the more massive stars and typical planets. The researchers also made observations using a trio of ground-based telescopes – the 8-meter Gemini South Telescope, the 6.5-meter Magellan Telescope and the ESO’s 3.6-meter New Technology Telescope.