Astronomy Fact of the Day: WISE 0855−0714, the Chilly Champion

Our sun blazes at a surface temperature of nearly 10,000 degrees Fahrenheit. But out in the vast expanse of space, far beyond our solar system's cozy confines, lurks a celestial object so cold it challenges our very definition of a "star": WISE 0855−0714. This brown dwarf, discovered by NASA's Wide-field Infrared Survey Explorer (WISE) mission, holds the title of the coldest-known star, boasting a frigid surface temperature of a mere -48° Fahrenheit (-44° Celsius).

Brown dwarfs occupy a fascinating middle ground between planets and stars. Too massive to be considered planets, they lack the mass needed to sustain hydrogen fusion, the process that powers stars like our sun. This absence of sustained fusion means they radiate far less energy and consequently remain significantly cooler than their stellar counterparts. WISE 0855−0714, however, takes this coolness to an extreme.

Located approximately 7.2 light-years away from Earth, this sub-brown dwarf is incredibly faint. Its low temperature means it emits most of its radiation in the infrared spectrum, making it undetectable to the naked eye and difficult to observe with visible-light telescopes. It was only thanks to WISE's infrared capabilities that this elusive object was discovered.

The incredibly low temperature of WISE 0855−0714 presents astronomers with intriguing questions. Its composition and formation remain areas of active research. While typical brown dwarfs form from the collapse of gas and dust clouds, the precise processes leading to the creation of such an exceptionally cool object are still being investigated. Understanding its atmospheric composition, internal structure, and evolution could provide valuable insights into the formation and evolution of other low-mass objects in the universe.

Further complicating the picture is the object's relatively high speed compared to its neighboring stars. This suggests it might have been ejected from a nearby star system, a scenario supported by its low metallicity (meaning a lower abundance of elements heavier than hydrogen and helium compared to the Sun).

The discovery of WISE 0855−0714 underscores the diversity and complexity of celestial objects in our galaxy. This "chilly champion" serves as a reminder that our understanding of stars and planetary systems is constantly evolving, and there are still many mysteries waiting to be uncovered in the cold, dark corners of space. Future observations, using advanced infrared telescopes and spectroscopic analysis, will hopefully shed more light on this fascinating object and help us better understand the processes that govern the formation and evolution of stars and brown dwarfs.