2023-06-16 21:22:20
Six new runaway stars have been discovered across the Milky Way. Two hypervelocity stars, called J0927 and J1235, are moving faster than any object of this type ever seen.
According to new research, these record-breaking stars are traveling at 5.1 million miles per hour (2,285 kilometers per second) and 3.8 million miles per hour (1,694 kilometers per second), respectively. J0927 has the fastest orbital speed ever observed, and if it were a ground object, it would be able to race between New York and Mississippi in less than a second. At this speed, any object can revolve around the Earth 694 times in an hour.
The other four stars are no slouch in the speed department, all traveling at 2.2 million miles per hour (1,000 kilometers per second). These high-velocity stars travel through the Milky Way so fast that they have enough speed to escape the gravitational influence of our galaxy, also known as escape velocity.
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“These stars are unusual because they travel much faster than normal stars in the Milky Way. Because it is faster than the galactic escape velocity, it will soon be catapulted into intergalactic space,” team leader and Harvard/Smithsonian Center for Astrophysics researcher Karim El-Badry told Space.com. “We were looking for things like that, so we had some hope and expectation that they were there, but their properties were different from what we expected.”
The team behind the discovery believes that the incredible speed of these four stars might be the result of being launched by a specific type of cosmic explosion called a Type IA supernova. This gave them unusually high surface temperatures, El Badry said, which surprised the team.
“They are much hotter than normal stars – and their unusual formation history may have involved a supernova explosion right next to them!” The astrophysicist explained.
Type Ia supernovae occur in binary systems with stellar remnants called white dwarfs, which form when sun-like stars die, feeding on material from a companion star.
White dwarfs – also known as “declining stars” – are incredibly dense as a result of the collapse of a stellar core, crushing mass around the sun into a ball the size of Earth, but not big enough. The alleged cross Chandrasekhar mountain rangeThe mass required for a star to launch a “normal” supernova and produce a neutron star or black hole upon its death.
When material from its donated stellar companion falls onto the surface of a white dwarf, the stellar debris collects. That is, this process of donating stellar material might give the white dwarf the critical mass needed to propel it over the Chandrasekhar limit, leading to a thermonuclear explosion known as a Type Ia supernova.
Not only do these explosions create some of the brightest events in the universe, but they are so consistent that astronomers refer to them as “steady candles” because they can be used to measure cosmic distances.
While any supernova can release enough energy to create runaway stars, the team thinks it may take an even more powerful supernova to accelerate these stars to supersonic speeds. These particular explosions are known as “violent helium-ignited mergers” or “dynamically degenerate double explosions”.
D⁶ supernovae occur when white dwarfs strip helium rather than hydrogen from the outer layers of their companion star, which is thought to be another white dwarf (hence the double decay). This results in a second massive explosion (hence the double blast) catapulting the subwhite dwarf into a high-velocity runaway star.
“The formation of runaway stars is very unusual,” El Badry explained. “All stars in the Milky Way have atmospheres that are mostly hydrogen and helium, but these materials contain neither hydrogen nor helium and are mostly made up of carbon and oxygen.”
This indicates that these runaway stars are degenerate white dwarfs and also supports the idea that they were exploded by a D⁶ supernova at extreme speeds.
El-Badry and colleagues used the constant light output of Type Ia standard candles to calculate the firing rate of runaway stars. They found that the rate at which high-velocity stars form corresponds with the rate at which Type Ia supernovae persist, suggesting that many of these events may be D⁶ explosions.
This led to the conclusion that there are a large number of such high-speed stars passing through the universe that astronomers have yet to discover.
Although they were discovered within the Milky Way, these runaway new stars, at 2.2 million miles per hour (1,000 kilometers per second), will one day leave our galaxy at an escape velocity of regarding 1.2 million miles per hour (550 kilometers per second). . The group believes that they are not the first stars shot up by the Milky Way.
“If a large portion of the type Ia supernovae formed a D6 star, the galaxy might have launched more than 10 million stars into intergalactic space.” Al-Badri and colleagues wrote:
Of course, the spin rate is reasonable, and just as our galaxy is throwing high-speed stars at its neighbors, researchers led by El Patri believe other galaxies are throwing high-speed stars at us. They say that many of the faint, runaway stars, which spewed out from galaxies in the local group of the Milky Way, must have penetrated our galaxy near the solar system.
The research is described in a paper submitted for publication in the Open Journal of Astrophysics and is now available in the paper’s repository. arXiv.
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