An object discovered orbiting a star 1,400 light-years away is testing the limits of what we previously thought was possible in the universe. The object, a brown dwarf, is on an incredibly close orbit with its hot host star, resulting in a temperature that exceeds 8,000 Kelvin, well above the Sun’s temperature of 5,778 Kelvin. This brown dwarf, known as WD0032-317B, is the hottest object of its kind ever discovered, breaking all known records.
Understanding Extreme Environments
The discovery of this brown dwarf could help us understand what happens to gas giants like Jupiter orbiting massive, hot stars. Planets in close proximity to their stars are exposed to high levels of ultraviolet radiation, which can cause their atmospheres to evaporate, and the molecules within to break apart. This process is known as thermal dissociation. However, the study of such environments is difficult due to the properties of the stars, such as their activity and rotation rate.
Brown Dwarfs and White Dwarfs
A brown dwarf is a unique object that falls between a planet and a star in its characteristics. It is about 13 times the mass of Jupiter and can have enough pressure and heat in its core to ignite deuterium fusion. Brown dwarfs can reach sizes of up to 80 Jupiter masses and temperatures of around 2,500 Kelvin. They are cooler and dimmer than red dwarfs but glow in infrared wavelengths.
On the other hand, white dwarfs are the final stage in the life cycle of stars like the Sun. When these stars run out of hydrogen in their core, they eject their outer layers, and the core collapses into an ultra-dense object around the size of Earth. White dwarfs shine with residual heat, but the death process is very energetic, making them extremely hot with temperatures comparable to those of blue supergiants.
Studying Extreme Regimes
One way to study extreme regimes is to look at brown dwarfs in binary systems with white dwarfs. White dwarfs are much smaller than supergiants like KELT-9, which makes them dimmer and easier to study. The international team of astrophysicists, led by Na’ama Hallakoun of the Weizmann Institute of Science in Israel, used the Ultra-Violet-Visual Echelle Spectrograph (UVES) instrument on the European Southern Observatory’s Very Large Telescope to obtain new observations of WD0032-317. They found that the brown dwarf is in fact a companion of the white dwarf on a breakneck orbit of just 2.3 hours.
The discovery was made when the astronomers detected the hydrogen emitted by the brown dwarf as the star evaporated it. The brown dwarf is tidally locked, with one side perpetually facing the star, resulting in extreme temperatures. The team calculated that the companion’s heated day-side temperature ranges between 7,250 and 9,800 Kelvin, while its night-side temperature ranges between 1,300 and 3,000 Kelvin.
This discovery is significant as it is the hottest known brown dwarf, making it a great candidate for studying how extremely hot stars can evaporate their lower-mass companions. Studying objects like WD0032-317B can help us understand rare outlier objects like KELT-9b.
The discovery of WD0032-317B challenges our notions of what is possible in the universe and provides an opportunity to study extreme environments and regimes previously unexplored. The study of this brown dwarf and its orbiting companion could lead to a better understanding of the processes that occur in such environments and help us understand the outliers in the universe.
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