Scientists are confused about two newly discovered stars. The two stars, one of which was announced this month in the journal Nature, send out long pulses (脉冲) of radio waves about every 20 minutes. This means they move much more slowly, and they have other characteristics that astronomers can’t explain. “We are all still quite amazed,” says astronomer Natasha Hurley-Walker, who led the discovery of both of these surprising sources.
The mystery began in 2021, when Hurley-Walker and her colleagues discovered a slowly repeating radio pulse. It shone for three months. But by the time they discovered it in the records, its activity had died down, and it had become invisible in the skies. In a January 2022 paper, the scientists suggested the object could be a kind of star called a magnetar (磁陀星). But the object, with the name GLEAM-X J162759.5-523504.3, sent out a pulse every 18 minutes instead of every few seconds like known magnetars.
It also had no X-ray signal associated with the radio emission (发射), which doesn’t fit with magnetar theories. And strangely, the object’s magnetic field was likely much stronger than previously seen. So the scientists began looking for other similar objects. In June 2022, Hurley-Walker and her colleagues began observing the entire visible sky every three nights. Almost immediately, they found something that sent out a radio flash every 21 minutes.
At first glance, it looked similar to the previously discovered object. But once the team began to dig through data for additional pulses from this source, named GPM J1839-10, the object only seemed more perplexing. Unlike the first star, the signal of J1839-10 was detected over decades.
For now, researchers assume both objects are the same. But why would one flash for three months and the other for 33 years and counting? “I don’t know,” says Hurley-Walker. “That’s the problem.”
8. What can be learned about the two newly discovered stars?
A.They were made public in Nature this month. |
B.They send out short radio waves every 20 minutes. |
C.They move at the slowest speed of all known stars. |
D.They are unlike the stars astronomers have seen before. |
9. How often do known magnetars send out a pulse?
A.Every few seconds. | B.Every 18 minutes. |
C.Every 20 minutes. | D.Every 21 minutes. |
10. What drove scientists to look for the second star?
A.Radio waves research project. | B.Strange features of the first star. |
C.The government’s guidance program. | D.The assumption of the magnetar theories. |
11. Which of the following best explains “perplexing” underlined in paragraph 4?
A.Appealing. | B.Challenging. |
C.Unaccountable. | D.Unacceptable. |