2023-08-07 01:08:06
Schematic diagram of the merger of two neutron stars. (University of Warwick/Mark Garlick/Public Domain)[The Epoch Times, August 7, 2023](The Epoch Times reporter Linda compiles and reports) In our galaxy, there are regarding 100 billion stars, and they are all locked in Somewhat pared-down, organized track, but with a few escapees. These runaway stars were probably blasted out of orbit by a supernova explosion, and fled to the depths of the universe without returning. The Milky Way produces regarding two supernovae per century, and not every supernova triggers the aforementioned stellar escape, making these events relatively rare. But astronomers have just reported six new such escapes in a recent study. Two of them were also the fastest ever. In the new study, astronomers used data collected by the European Space Agency’s (ESA) Gaia Space Observatory (Gaia) to identify two of the fastest runaway stars in the radial direction. The speed of the first star, J0927, is 1,420 miles per second. A second star, J1235, follows at 1,053 miles per second. These speeds are difficult to understand from human experience. For example, the fastest human-made spacecraft is the Parker Solar Probe, which reached a record speed of 101 miles per second in 2021, which is regarding one-tenth of the aforementioned stellar speed. But if you’re going to escape the galaxy, you’ll need really fast speeds. Seven miles per second is needed just for the rocket to escape Earth’s gravity. Entire galaxies like the Milky Way have escape velocities of up to 341 miles per second. It can be said that the super-high-speed stars J0927 and J1235 have such amazing speeds. They likely derive their extraordinary speed from “dynamically driven double-degenerate double-detonation” (D⁶) supernovae. Supernova Explosions A double detonation typically occurs when a white dwarf — a type of star that is older and cooler than our sun — orbits another white dwarf. White dwarfs are peculiar objects because they can exist in relative silence for billions of years or explode as supernovae. Why do white dwarfs explode? As the white dwarf sucks material from its companion star, it heats up, eventually triggering a runaway reaction that destroys the white dwarf in a violent explosion in the form of a supernova. This process is known as the “single degenerate model” of Type Ia supernovae. Something more special happens when the companion star is another white dwarf star covered in a thick layer of helium, a D⁶ supernova explosion, according to space journalist Michelle Starr for Science Alert. . D⁶ is called double detonation because it involves two different explosions. The first explosion occurs when one of the white dwarfs accumulates too much helium, which triggers a thermonuclear explosion, Starr said. “But the helium explosion goes a step further: its shock wave triggers a second explosion in the white dwarf’s core,” Stahl added. The new study has been submitted for publication in the Open Journal of Astrophysics. ◇Editor in charge: Ye Ziwei
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