Astronomers Identify 'White Dwarf' Star that Survived Massive Explosion
2022-07-03
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1Scientists have identified a star that, they say, survived a massive explosion and ended up being brighter than before.
2The star is a kind known as a "white dwarf."
3These are very dense objects that have a mass about equal to the sun.
4But they can be as large as planets like Earth.
5A white dwarf is formed when the star burns off all its central nuclear fuel and loses its outer layers.
6Astronomers observed the white dwarf star with the Hubble Space Telescope.
7The telescope is operated by the American Space Agency NASA.
8The Hubble has discovered "the oldest burned-out stars in our Milky Way Galaxy," NASA reported.
9Some ancient white dwarf stars seen by Hubble are estimated to be 12 to 13 billion years old.
10That is nearly as old as the universe itself.
11The observed star is in a galaxy called NGC 1309.
12It is about three quarters the size of our Milky Way.
13The white dwarf is about 108 million light years from Earth.
14A light year is the distance light travels in a year.
15The observation team said that at some point, the white dwarf reached a mass that was 1.4 times the sun's mass.
16This led to thermonuclear reactions in the star's center that caused a supernova event.
17NASA describes a supernova as an "extremely bright, super-powerful explosion of a star."
18A supernova takes place at the end of a star's life.
19The scientists say the supernova should have killed off the white dwarf star but did not.
20The research was led by a team at the Las Cumbres Observatory in California.
21The lead writer of a study describing the finding was astronomer Curtis McCully.
22He told Reuters news agency, "During the explosion, radioactive material was produced. This is what powers the brightness of the supernova."
23He added that some of the material "was left over in the surviving remnant star" and acted as fuel to heat it.
24"We were quite surprised that the star itself had not been destroyed but had actually survived and is brighter than before it exploded," McCully said.
25There are different kinds of supernova events.
26Each depends on the size and chemical makeup of the star and the power of the explosion.
27This observed white dwarf produced an uncommon kind of supernova called "Type Iax," the Las Cumbres Observatory said in a statement.
28The team said this kind is less bright and weaker than traditional "Type Ia" supernovas.
29Scientists believe this kind of supernova does not destroy the white dwarf.
30Instead, it leaves behind an "undead" remnant.
31This theory is confirmed by the new observations, the research team said.
32"We have called these objects 'zombie stars' for this very reason. They died, but not quite," McCully said.
33Earlier experiments involving supernova activity had suggested that in some cases, white dwarf stars were able to survive these kinds of events.
34"It's exciting to think that was telling us something about the actual physics of these supernovas," McCully added.
35Scientists have discovered about 50 supernovas of this kind.
36But until now, they had not been able to identify the surviving white dwarf star.
37Scientists believe that our sun is also likely to become a white dwarf one day.
38This happens to about 97 percent of stars.
39But the event involving our sun is not expected to happen until at least 5 billion years from now.
40I'm Bryan Lynn.
1Scientists have identified a star that, they say, survived a massive explosion and ended up being brighter than before. 2The star is a kind known as a "white dwarf." These are very dense objects that have a mass about equal to the sun. But they can be as large as planets like Earth. A white dwarf is formed when the star burns off all its central nuclear fuel and loses its outer layers. 3Astronomers observed the white dwarf star with the Hubble Space Telescope. The telescope is operated by the American Space Agency NASA. 4The Hubble has discovered "the oldest burned-out stars in our Milky Way Galaxy," NASA reported. Some ancient white dwarf stars seen by Hubble are estimated to be 12 to 13 billion years old. That is nearly as old as the universe itself. 5The observed star is in a galaxy called NGC 1309. It is about three quarters the size of our Milky Way. The white dwarf is about 108 million light years from Earth. A light year is the distance light travels in a year. 6The observation team said that at some point, the white dwarf reached a mass that was 1.4 times the sun's mass. This led to thermonuclear reactions in the star's center that caused a supernova event. 7NASA describes a supernova as an "extremely bright, super-powerful explosion of a star." A supernova takes place at the end of a star's life. The scientists say the supernova should have killed off the white dwarf star but did not. 8The research was led by a team at the Las Cumbres Observatory in California. The lead writer of a study describing the finding was astronomer Curtis McCully. 9He told Reuters news agency, "During the explosion, radioactive material was produced. This is what powers the brightness of the supernova." He added that some of the material "was left over in the surviving remnant star" and acted as fuel to heat it. 10"We were quite surprised that the star itself had not been destroyed but had actually survived and is brighter than before it exploded," McCully said. 11There are different kinds of supernova events. Each depends on the size and chemical makeup of the star and the power of the explosion. 12This observed white dwarf produced an uncommon kind of supernova called "Type Iax," the Las Cumbres Observatory said in a statement. The team said this kind is less bright and weaker than traditional "Type Ia" supernovas. 13Scientists believe this kind of supernova does not destroy the white dwarf. Instead, it leaves behind an "undead" remnant. This theory is confirmed by the new observations, the research team said. 14"We have called these objects 'zombie stars' for this very reason. They died, but not quite," McCully said. Earlier experiments involving supernova activity had suggested that in some cases, white dwarf stars were able to survive these kinds of events. "It's exciting to think that was telling us something about the actual physics of these supernovas," McCully added. 15Scientists have discovered about 50 supernovas of this kind. But until now, they had not been able to identify the surviving white dwarf star. 16Scientists believe that our sun is also likely to become a white dwarf one day. This happens to about 97 percent of stars. But the event involving our sun is not expected to happen until at least 5 billion years from now. 17I'm Bryan Lynn. 18Reuters and the Las Cumbres Observatory reported on this story. Bryan Lynn adapted the report for VOA Learning English. 19We want to hear from you. Write to us in the Comments section, and visit our Facebook page. 20___________________________________________________________________ 21Words in This Story 22galaxy - n. one of the independent groups of stars in the universe 23remnant - n. a piece of something that continues to exist when the rest of that thing goes away 24zombie - n. a dead body that walks around, as portrayed in fictional stories