In an astronomical revelation that challenges conventional wisdom about the cosmos, a celestial body orbiting a star located 1,400 light-years away is confounding scientists and shattering preconceived notions about the universe’s boundaries.
This extraordinary object is a brown dwarf, a curious classification that straddles the line between planets and stars. Yet, it defies categorization due to its remarkably close orbit with an intensely hot host star. The temperature of this brown dwarf surpasses an astonishing 8,000 Kelvin (7,727 degrees Celsius or 13,940 Fahrenheit), rendering it hot enough to disintegrate the molecules in its atmosphere into individual atoms.
Such a temperature far exceeds even the searing surface of the Sun, which registers at a relatively mild 5,778 Kelvin. This brown dwarf, known as WD0032-317B, has remarkably set a new temperature record for its kind, making it the hottest specimen of its category ever discovered.
Though brown dwarfs tend to be warmer than planets, they pale in comparison to the cooler-burning red dwarf stars, unable to achieve temperatures akin to those of the Sun through internal fusion processes.
Led by astrophysicist Na’amaHallakoun from the Weizmann Institute of Science in Israel, an international team of researchers has christened the object WD0032-317B. Their discovery offers an invaluable opportunity to gain insights into the fate of gas giants resembling Jupiter that orbit extremely hot, massive stars. Observing these interactions is a challenge due to factors like stellar activity and rotation rates.
When planets are situated in close proximity to their host stars, they endure intense ultraviolet radiation. This radiation has the power to vaporize their atmospheres and break down molecular structures, a process known as thermal dissociation.
Nonetheless, the dynamics of this extreme environment remain largely unexplored. In such proximity to a blazing star, extracting signals from an exoplanet’s orbit can be complicated by the glare of the star’s activity.
One such example is the exoplanet KELT-9b, which orbits a blue supergiant star, resulting in day-side temperatures exceeding 4,600 Kelvin. This surpasses the temperatures of many stars, including red dwarfs, the most prevalent stellar type in our galaxy, which possess a maximum surface temperature of around 4,000 Kelvin.
The study of such extreme scenarios could be facilitated by brown dwarfs in binary systems with white dwarf stars. White dwarfs, remnants of stars like our Sun, are smaller and dimmer than blue supergiants, making them a suitable backdrop against which to discern the presence of heated companion objects.
Brown dwarfs are enigmatic entities, straddling the boundary between planets and stars. With a mass approximately 13 times that of Jupiter, they possess sufficient pressure and heat in their cores to trigger deuterium fusion, a process reliant on a heavier isotope of hydrogen. Brown dwarfs can reach temperatures of roughly 2,500 Kelvin, making them cooler and dimmer than red dwarfs, yet emitting infrared radiation.
Contrastingly, white dwarfs mark the final phase in the lifecycle of stars like our Sun. As these stars exhaust their core hydrogen, they shed their outer layers, resulting in the collapse of their core into an ultra-dense object approximately the size of Earth. White dwarfs emit residual heat but possess temperatures akin to blue supergiants due to the highly energetic process that leads to their formation.
Enter WD0032-317, a scorching, low-mass white dwarf star roughly 40 percent of the Sun’s mass, burning at a staggering 37,000 Kelvin.
Early observations in the 2000s, using the Ultra-Violet-Visual Echelle Spectrograph (UVES) on the European Southern Observatory’s Very Large Telescope, suggested that WD0032-317 was experiencing orbital movement induced by an unseen companion. Subsequent infrared observations confirmed this companion to be a brown dwarf.
Hallakoun and her colleagues conducted further UVES observations, revealing that the companion is a brown dwarf with a mass ranging between 75 and 88 times that of Jupiter, on a swift orbit lasting just 2.3 hours.
The detection hinged on a unique phenomenon—the evaporation of the brown dwarf’s atmosphere, releasing detectable hydrogen emissions as it faces its white dwarf host. Tidally locked due to its close proximity, one side of the brown dwarf perpetually faces the star, causing the extreme temperature disparities.
The team’s calculations unveil an astonishing range of temperatures on the brown dwarf, with the day side’s temperature varying between approximately 7,250 and 9,800 Kelvin, while the night side ranges from 1,300 to 3,000 Kelvin. These extremes make WD0032-317B a riveting subject for studying how incredibly hot stars can erode their lower-mass companions.
The remarkable discovery of WD0032-317B not only captivates the scientific community but also offers a remarkable avenue for understanding the interactions between stars and their companions in intense environments. Through unraveling the mysteries of objects like WD0032-317B, we gain insights into phenomena such as KELT-9b, providing a deeper understanding of the intricate mechanisms shaping our universe.
News Mania Desk / Agnibeena Ghosh 20th August 2023
