Astronomers from CalTech and Hawai'i have just discovered the smallest white dwarf that formed after 2 less massive stars merged. It is said to have a mass that is greater than the Sun in a body roughly the size of the Moon.
Ilaria Caiazzo, the lead author and researcher at CalTech, explains that despite it seeming counterintuitive, smaller white dwarfs are always more massive. This is because white dwarfs lack nuclear burning that keeps normal stars again their own self-gravity,m the size of white dwarfs are instead regulated by quantum mechanics.
White Dwarf Explained
According to NASA, white dwarfs are stars that have exhausted all their nuclear fuel and are almost at the end of their nuclear burning stage. These types of stars expel most of their outer material, creating what is known as a planetary nebula. Once all nuclear fuel is burned up, only the hot core remains.
The core then becomes a hot white dwarf, with temperatures far exceeding 100,000 Kelvin. Unless it accretes matter from a nearby star, the white dwarf then cools down in the next billion years.
Because white dwarf stars are unable to create their own internal pressure, gravity begins to compact its matter inward until even its electrons are smashed together. Normally, this circumcenter isn't allowed to occupy the same energy level.
Discovering a White Dwarf with More Mass than the Sun
The discovery published in the journal Nature, entitled "A highly magnetized and rapidly rotating white dwarf as small as the Moon," was made by the ZTF operating at Caltech's Palomar Observatory and 2 Hawai'i telescopes. These helped astronomers characterize the dead star.
The discovery of the white dwarf helps explain what can happen as a star begins to die. A pair of white dwarfs, spiraling each other, begin to lose energy in the form of gravitational waves, which ultimately begin to merge. If the dead stars have enough mass, they will explode into what is known as a Type I supernova. However, below the threshold of mass, dwarf stars can combine into a new white dwarf with a heavier mass.
ScienceDaily reports that the newfound tiny white dwarf, named by astronomers as ZTF J1901+1458, evolved its progenitors to merge, producing a white dwarf that has 1.35 times the mass of the sun. It has an immense magnetic field roughly 1 billion times stronger than the sun and whips around it, its axin at a frenzied pace revolving every 7 minutes.
Caiazzo explains that the team caught the object that wasn't massive enough to explode and probed how massive white dwarfs would come to be. The team of astronomers speculates that it's possible that the white dwarf has enough mass to one day collapse into a neutron star, reports ScienceDaily.
If the theory is correct, it may mean that portions of other neutron stars form in the same way. The new object's closeness of about 130 light-years away and young age of roughly 100 million years old indicates that similar occurrences may be more common in our galaxy than we previously thought.
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