The smallest star of its kind, a dead star that is half the size of the Moon, has ever been seen.It is a white dwarf star, which is the superdense collapsed center of a star within the mass range of Sun. However, it measures only 4,280 km (2,660 mi) in circumference. It is also the largest white dwarf star that we have ever seen. It has a mass of around 1.35 times that of the Sun.Take a moment to think about that. It's a tiny fraction of the Sun's mass compressed into a sphere slightly smaller than our Moon. It's amazing, isn’t it?The white dwarf ZTF J1901+1458, located 130 light-years from Earth, is truly amazing. Its mass and denseness place it just above the Chandrasekhar limit, which is the maximum mass that a white dwarf can have before it becomes unstable enough to explode in a stunning supernova."We found this very interesting object that was not quite large enough to explode," stated Ilaria Caiazzo, Caltech theoretical astrophysicist. "We are really probing the size of a white dwarf."White dwarfs are the smallest type of dead star on this dead star continuum. These stars are made up of collapsed cores that have eight times the mass as the Sun. When these stars reach the end of their main-sequence (nuclearfusion), their outer material is blown off and the core, which no longer supports the outward pressure of nuclear fusion, becomes an ultradense object.The white dwarf is prevented from collapsing under its own gravity up to the Chandrasekhar limit (around 1.4 solar masses). These electrons provide the star with the outward pressure it needs to keep from collapsing by removing electrons from their atomic nuclei.However, there are many white dwarf stars that exist in binary systems. This means that they are in orbital dance with another star. If they are close enough, the white dwarf can siphon material from its binary companion. This process can push the dead star beyond the Chandrasekhar limit and often trigger a Type Ia supernova.ZTF J1901+1458 appears to be an exceptional case.The team found that the white dwarf was the result of a merger between two smaller white dimers. However, their combined mass is not enough to produce a Type Ia supernova.It is only 100 million years old and has a crazy magnetic field, which is about a billion times stronger than the Sun. It rotates around once in seven minutes. It's not the fastest white dwarf spin, but it's close. These characteristics indicate a merger in history.It is possible to be astonished at what happens next.Caiazzo stated, "This is highly speculational, but it's possible the white dwarf is large enough to further collapse into a neutron Star."It is so dense and massive that electrons in its core are being captured by protons within nuclei to make neutrons. The force of gravity is pushed against by electron pressure, which keeps the star intact. When enough electrons are removed, the core will collapse.When a star with a mass between 8-30 times that of the Sun reaches its end, neutron stars are formed. They are denser than white dwarfs and support by neutron degeneracy tension. The stellar core becomes a neutron star once it has gone kablooey and has lost its outer material.ZTF J1901+1458, according to the team's analysis, suggests another formation route for the low-mass extreme objects.This could indicate that ZTF J1901+1458, or other stars similar to it, could tell us a lot more about the types white dwarf binaries which turn into neutron star. They are expected to be found by the team.There are many questions that need to be answered, including what is the galaxy's rate of white dwarf mergers and how can it explain the high number of supernovae of type Ia. What is the magnetic field created by these powerful events? And why are there so many magnetic field strengths among white dwarfs? Caiazzo stated."Finding large numbers of white dwarfs from mergers will allow us to answer all these questions."Nature published the research.
