VOA慢速英语--科学家们报告了有史以来最大的恒星爆炸

（单词翻译）

Scientists have just seen the biggest star explosion observed to date. Star explosions are often called supernovas.

The supernova was up to 100 times larger than our sun and happened in a galaxy¹ far away.

It released two times as much energy as any star explosion ever observed and happened about 4.6 billion light years from Earth, scientists said. A light year is the distance light travels in one year, which is 9.5 trillion kilometers.

Matt Nicholl is an astrophysicist with the University of Birmingham in England. He told Reuters news agency that two very large stars - each about 50 times the sun's mass - may have joined to make one huge star. He thinks this took place about 1,000 years before the explosion. The stars had been part of a binary² system -- two stars pulled toward each other through gravity.

The joined star exploded in a supernova that has been named SN2016aps.

"We found that the supernova was able to become so bright because of a powerful collision" between the matter thrown by the explosion and a shell of gas shaken off by the star a few years before, Nicholl explained.

He is lead writer of the study published this week in the journal Nature Astronomy.

Stars die in many different ways, depending on their size and other properties. When a massive star - more than eight times the mass of our sun - uses up its fuel, it cools off and its center collapses³. This launches shock waves that cause its outer layer to explode so violently that it can shine brighter than whole galaxies⁴.

The researchers observed the explosion for two years until it lowered to one percent of its highest brightness. They said it may have been an example of an extremely rare "pulsational pair-instability" supernova.

Peter Blanchard explains what that means. He said pulsational pair-instability is when very large stars experience pulsations which throw material away from the star.

Blanchard, who co-wrote the study, is an astrophysicist at Northwestern University in Illinois.

He said the discovery shows there are many new and exciting things that remain uncovered in the universe.

Very massive stars like this one were probably more common early in the universe's history, Nicholl said.

"The nature of those first stars is one of the big questions in astronomy," Nicholl added. "Seeing things further away means looking back further and further in time. So we might actually be able to see the very first stars if they explode in a similar manner to this one. Now we know what to look for."

Words in This Story

galaxy - n. any one of the very large groups of stars that make up the universe

theory - n. an idea or set of ideas that is intended to explain facts or events

astrophysicist - n. a scientist who studies the physical and chemical properties and structures of stars, planets and other objects in outer space

gravity - n. the natural force that tends to cause physical things to move towards each other

collision - n. a crash in which two or more things or people hit each other

pulsational - adj. a periodically recurring⁵ increase and decrease of a quantity, such as pressure, volume or voltage

astronomy - n. the scientific study of stars, planets, and other objects in outer space