Scientists Discover a New Kind of Star Explosion
2022-04-26
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1Scientists who study stars have detected a previously unknown kind of event called a micronova.
2The event involves thermonuclear explosions that take place on a star called a white dwarf.
3The explosions happen because the white dwarf's gravity has pulled material from a companion star.
4Astronomers said recently that a micronova is by far the least powerful kind of star explosion now known.
5Micronovae are observed from Earth as bursts of light lasting about 10 hours.
6They have been documented on three white dwarf stars:
7one 1,680 light years away from Earth, one 3,720 light years away, and one 4,900 light years away.
8A light year is the distance light travels in one year.
9Simone Scaringi of Durham University in England was the lead writer of the study that appeared in the publication Nature.
10"The discovery was an unexpected surprise," Scaringi said.
11He added that finding these events "requires looking at the right place at the right time."
12White dwarf stars are among the densest objects in the universe.
13They result from the collapse of a dying star's core.
14They have the mass of our sun but are about the size of Earth.
15Most stars, including the sun, will end their existence in this way.
16Some white dwarfs are part of what is called a binary system, meaning that they are in an orbit with another star.
17Micronovae happen in special binary systems with a white dwarf star possessing a strong magnetic field and a low-mass normal star.
18The white dwarf's gravity can pull hydrogen gas from the companion star's surface.
19The hydrogen then flows toward the white dwarf's magnetic poles.
20At the white dwarf's poles, the pressure and temperature rise.
21This causes thermonuclear fusion that converts hydrogen into helium and releases energy.
22"...This fusion is explosive, and the micronova occurs: a thermonuclear 'bomb' goes off," said astronomer Paul Groot who helped write the study.
23The explosion is not widespread and does not destroy the white dwarf.
24In fact, micronova events can repeat many times.
25"Only a very small percentage of the white dwarf participates in this explosion, roughly about one millionth of the surface area...this would be an area of about, say, the city of London," Groot added.
26Each micronova event burns through material equal to one large asteroid, or just over one millionth of Earth's mass, Scaringi said.
27A micronova is similar to a nova, a thermonuclear explosion involving a whole star.
28With novae, the white dwarf does not have a strong magnetic field, meaning that hydrogen stolen from the companion star is spread rather than staying at the poles.
29Novae can last for weeks or months, burning through about a million times more mass than micronovae, Scaringi said.
30The researchers discovered the micronovae when examining data from NASA's TESS space telescope.
31They used the European Southern Observatory's Very Large Telescope in Chile to confirm the explosions involving white dwarfs.
32There are other kinds of star explosions as well.
33A kilonova takes place when two neutron stars or a neutron star and a black hole merge.
34A hypernova is a kind of supernova involving a large star exploding at the end of its life and collapsing to form a black hole.
35And a luminous red nova involves two stars merging.
36I'm John Russell.
1Scientists who study stars have detected a previously unknown kind of event called a micronova. 2The event involves thermonuclear explosions that take place on a star called a white dwarf. The explosions happen because the white dwarf's gravity has pulled material from a companion star. 3Astronomers said recently that a micronova is by far the least powerful kind of star explosion now known. 4Micronovae are observed from Earth as bursts of light lasting about 10 hours. They have been documented on three white dwarf stars: one 1,680 light years away from Earth, one 3,720 light years away, and one 4,900 light years away. A light year is the distance light travels in one year. 5Simone Scaringi of Durham University in England was the lead writer of the study that appeared in the publication Nature. 6"The discovery was an unexpected surprise," Scaringi said. He added that finding these events "requires looking at the right place at the right time." 7White dwarf stars are among the densest objects in the universe. They result from the collapse of a dying star's core. They have the mass of our sun but are about the size of Earth. Most stars, including the sun, will end their existence in this way. 8Some white dwarfs are part of what is called a binary system, meaning that they are in an orbit with another star. 9Micronovae happen in special binary systems with a white dwarf star possessing a strong magnetic field and a low-mass normal star. The white dwarf's gravity can pull hydrogen gas from the companion star's surface. The hydrogen then flows toward the white dwarf's magnetic poles. 10At the white dwarf's poles, the pressure and temperature rise. This causes thermonuclear fusion that converts hydrogen into helium and releases energy. 11"...This fusion is explosive, and the micronova occurs: a thermonuclear 'bomb' goes off," said astronomer Paul Groot who helped write the study. 12The explosion is not widespread and does not destroy the white dwarf. In fact, micronova events can repeat many times. 13"Only a very small percentage of the white dwarf participates in this explosion, roughly about one millionth of the surface area...this would be an area of about, say, the city of London," Groot added. 14Each micronova event burns through material equal to one large asteroid, or just over one millionth of Earth's mass, Scaringi said. 15A micronova is similar to a nova, a thermonuclear explosion involving a whole star. With novae, the white dwarf does not have a strong magnetic field, meaning that hydrogen stolen from the companion star is spread rather than staying at the poles. Novae can last for weeks or months, burning through about a million times more mass than micronovae, Scaringi said. 16The researchers discovered the micronovae when examining data from NASA's TESS space telescope. They used the European Southern Observatory's Very Large Telescope in Chile to confirm the explosions involving white dwarfs. 17There are other kinds of star explosions as well. A kilonova takes place when two neutron stars or a neutron star and a black hole merge. A hypernova is a kind of supernova involving a large star exploding at the end of its life and collapsing to form a black hole. And a luminous red nova involves two stars merging. 18I'm John Russell. 19Will Dunham reported on this story for Reuters. John Russell adapted it for Learning English. 20____________________________________________________________________ 21Words in This Story 22thermonuclear - adj. Of or relating to transformations in the nuclei of atoms of low atomic weight (such as hydrogen) 23companion - n. a celestial body that appears close to another but that may or may not be associated with it in space 24astronomer -n. a scientist who studies stars, planets and objects in outer space 25burst -n. a short period of producing something suddenly 26merge - v. to become combined into one