VOA科学技术2024--NASA: Nova Explosion to Be 'Once-in-Lifetime' Event in Night Sky

The American space agency NASA says a huge star explosion is expected to light up the night sky later this year. NASA describes it as a "once-in-a-lifetime" event.

The event is known as a nova. It happens when changes to a star cause it to release a large amount of energy and it becomes very bright. This activity is only temporary and such stars usually return to their normal state after experiencing a nova event.

Astronomers² have predicted the nova is likely to happen by September 2024. The expected event will involve a two-star system - called a binary³ system - in the constellation⁴ Corona⁵ Borealis, also known as the Northern Crown. This constellation is about 3,000 light years from Earth. A light year is the distance light travels in a year - about 9.5 trillion kilometers.

The binary system is called T Coronae Borealis. It contains two gravitationally linked stars - a white dwarf⁶ and a red giant.

NASA describes a white dwarf as the remains⁷ of an Earth-sized star that died. A white dwarf is formed when the star burns off all its central nuclear fuel and loses its outer layers.

A red giant forms when a star releases large amounts of hydrogen at its center. This loss of energy causes the star to begin to collapse⁸. But the process also increases the red giant's temperature and pressure, leading to new releases of energy that can affect nearby objects.

Astronomers say a red giant's release of hydrogen in a binary system causes a heavy buildup of pressure and heat on the white dwarf. Over time, such buildup can cause a "thermonuclear explosion" large enough to blast away the material the white dwarf had collected.

This process differs from a supernova. NASA describes a supernova as an "extremely bright, super-powerful explosion of a star." The main difference is that a supernova is the final destruction that happens at the end of a particular star's life. In a nova, the white dwarf remains active after the event.

Scientists believe novas appear to repeat, on average, about every 80 years. NASA notes that nova events can keep happening "for tens of hundreds or thousands of years." That is why the space agency called the upcoming nova a "once-in-a-lifetime event."

Scientists say the nova explosion will be so bright, people should be able to see the resulting light without telescopes or other special equipment. The bright light can make it appear as though a new star has formed in the sky.

It will be at least the third time humans have witnessed a nova, the French news agency AFP reports. The event was first discovered by Irish astronomer¹ John Birmingham in 1866 and then reappeared in 1946.

Sumner Starrfield is a professor of astrophysics at Arizona State University. He told AFP he was very excited to see the nova event. He has studied the T Coronae Borealis star system at different times since the 1960s.

Starrfield is currently working on a scientific paper to predict what astronomers will learn about the repeating nova, whenever it shows up. "It could be today... but I hope it's not," he joked.

Rebekah Hounsell is a research scientist specializing in nova events at NASA's Goddard Space Flight Center in Maryland. She said that interest in the event may "create a lot of ... astronomers out there." She hopes this can give young people "a cosmic event they can observe for themselves, ask their own questions, and collect their own data."

She added that the nova event might even be helpful to "fuel the next generation of scientists."

Words in This Story

astronomer - n. a person who studies stars and planets

constellation - n. a group of stars that forms a particular shape in the sky and has been given a name

excited - n. feeling very happy and enthusiastic

cosmic - adj. relating to the whole universe

1 astronomer   

n.天文学家

参考例句：

• A new star attracted the notice of the astronomer.新发现的一颗星引起了那位天文学家的注意。
• He is reputed to have been a good astronomer.他以一个优秀的天文学者闻名于世。

2 astronomers   

n.天文学者，天文学家( astronomer的名词复数 )

参考例句：

• Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》

3 binary   

adj.二，双；二进制的；n.双(体)；联星

参考例句：

• Computers operate using binary numbers.计算机运行运用二进位制。
• Let us try converting the number itself to binary.我们试一试，把这个数本身变成二进制数。

4 constellation   

n.星座n.灿烂的一群

参考例句：

• A constellation is a pattern of stars as seen from the earth. 一个星座只是从地球上看到的某些恒星的一种样子。
• The Big Dipper is not by itself a constellation. 北斗七星本身不是一个星座。

5 corona   

n.日冕

参考例句：

• The corona gains and loses energy continuously.日冕总是不断地获得能量和损失能量。
• The corona is a brilliant,pearly white,filmy light,about as bright as the full moon.光环带是一种灿烂的珠白色朦胧光，几乎像满月一样明亮。

6 dwarf   

n.矮子，侏儒，矮小的动植物；vt.使…矮小

参考例句：

• The dwarf's long arms were not proportional to his height.那侏儒的长臂与他的身高不成比例。
• The dwarf shrugged his shoulders and shook his head. 矮子耸耸肩膀，摇摇头。

7 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

8 collapse   

vi.累倒；昏倒；倒塌；塌陷

参考例句：

• The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。
• The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做了一次彻底的调查分析。