For the first time in recorded history, astronomers have been able to identify indirect evidence of a giant planet, dwelling in the orbit of a white dwarf star, known as WDJ0914+1914. Although the planet itself was not observed directly, its existence was suggested by the detection of a gas disc, created from its evaporating atmosphere. This historical discovery took place in the constellation of Cancer and the evidence was collected using the Very Large Telescope at the European Southern Observatory in Chile.
Significance of the Discovery
This groundbreaking discovery showcases the first real evidence of a planet revolving around a white dwarf star. Before this event, only smaller entities such as asteroids were observed in the proximity of white dwarfs. This system gives us a sneak peek into the far distant future of our solar system, forecasted about 4.5 billion years from now, where the Sun will transform into a white dwarf and evaporate all planets.
Understanding White Dwarfs
White dwarfs are stars that have exhausted all hydrogen fuel used for nuclear fusion reactions. They develop from stars like the Sun, which fuse hydrogen cores into helium through nuclear fusion. Fusion reactions produce heat and outward pressure in a star’s core, leading it to inflate into a gigantic red giant. Conversely, gravity exerts inward pressure, balancing the expansion.
As the hydrogen fuel depletes and fusion slows down, gravity causes the star to collapse onto itself, resulting in a white dwarf. Incredibly dense and compact, white dwarfs possess very high densities due to their reduced size post the fusion phase.
Transitioning from White to Black Dwarfs
Over tens or even hundreds of billions of years, a white dwarf cools down and transforms into a stagnant black dwarf, which emits no energy. As the oldest stars in the universe are between 10 to 20 billion years old, no black dwarfs have been identified so far.
It’s worth noting that not all white dwarfs cool into black dwarfs. If a white dwarf has enough mass, it reaches a level known as the Chandrasekhar Limit. Beyond this limit, the internal pressure of the star becomes so intense that the star explodes in a thermonuclear supernova.
Chandrasekhar Limit: The Boundary for White Dwarfs
| Description | Details |
|---|---|
| Mass Limit | No stable white dwarf can be more massive than about 1.4 times the mass of the Sun. |
| Name Origin | The limit is named after Nobel laureate Subrahmanyan Chandrasekhar. |
| Proposed Year | First proposed in 1931. |
| Nobel Prize | He was awarded the Nobel Prize in Physics in 1983 for his work on stellar structure and evolution. |
The Chandrasekhar Limit symbolizes the maximum theoretical mass possible for a stable white dwarf star. Any celestial object with a higher mass must inevitably collapse into a neutron star or a black hole. The limit owes its name to the Nobel laureate Subrahmanyan Chandrasekhar, who introduced the concept in 1931. He received a Nobel Prize in Physics in 1983 for his significant contributions towards comprehending the physical processes involved in the structure and evolution of stars.