CIS/RAS: Planet-like Object May Have Once Been a Star

[bystander]

Planet-like Object May Have Spent Its Youth as Hot as a Star
Carnegie Institution for Science | Royal Astronomical Society | 2014 Aug 05

A four-stage sequence (left to right) showing the possible extreme temperature evolution for WISE J0304-2705. When young the object was as hot as a star, shining with a temperature of at least 2800 °C for about 20 million years. After 100 million years or so it had cooled to 1500 °C, and by a billion years its temperature was around 1000 °C. The final stage is billions of years later, when WISE J0304-2705 had cooled to its current planetary temperature of 100-150 °C. [b][i](Credit: John Pinfield, 2014)[/i][/b]

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Astronomers have discovered an extremely cool object that could have a particularly diverse history—although it is now as cool as a planet, it may have spent much of its youth as hot as a star.

The current temperature of the object is 200 to 300 degrees Fahrenheit (100 to 150 degrees Celsius), which is intermediate between that of the Earth and of Venus. However, the object shows evidence of a possible ancient origin, implying that a large change in temperature has taken place. In the past this object would have been as hot as a star for many millions of years.

Called WISE J0304-2705, the object is a member of the recently established "Y dwarf" class—the coolest stellar temperature class yet defined, following the other classes O, B, A, F, G, K, M, L, and T. Although the temperature is similar to that of the planets, the object is dissimilar to the rocky Earth-like planets, and instead is a giant ball of gas like Jupiter.

The international discovery team, led by David Pinfield from the University of Hertfordshire and including Carnegie’s Yuri Beletsky, identified the Y dwarf using the WISE observatory—a NASA space telescope that has imaged the entire sky in the mid-infrared. The team also measured the spectrum of light emitted by the Y dwarf, which allowed them to determine its current temperature and better understand its history. Their work is published by Monthly Notices of the Royal Astronomical Society.

Only 20 other Y dwarfs have been discovered to-date, and amongst these WISE J0304-2705 is defined as “peculiar” due to unusual features in its emitted light spectrum. ...

Discovery of a new Y dwarf: WISE J030449.03-270508.3 - D. J. Pinfield et al

• arXiv.org > astro-ph > arXiv:1408.0284 > 01 Aug 2014