Astronomers detect powerful cosmic objects unlike anything they've seen before
As a supernova it flashes too fast, and as a pulsar it flashes too slowly. What is it in the universe?
The artist draws a slowly rotating magnetar imagination, which may be a mysterious source of signals. (Photo courtesy of ICRAR, International Centre for Radio Astronomy Research)
Astronomers have discovered a mysterious, twinkling star in our galaxy that releases massive energy to Earth three times in an hour.
Scientists have stated that this strange and energetic star, about 4,000 light-years from the sun, is unique and unlike any observed star.
The star under discussion, called GLEAM-XJ162759.5-523504.3 (in this case we refer to as GLEAM), suddenly appeared during a recent study of galactic radio waves.
According to the researchers, GLEAM quickly brightened up in about 60 seconds, directly becoming the brightest star in the entire night sky, and then disappearing into the darkness in a flash. Almost 20 minutes later, the star reappeared—steadily reaching a bright peak again, and a minute later there was nothing left in the night sky.
Objects like this that flicker in front of our telescope lenses are what we call transient objects. Usually, a transient marks a dying star, called a supernova, or the bizarre, rapidly rotating remains of a dead star, also known as a neutron star. However, according to what the researchers wrote in the latest survey, there is no one standard explanation that fits perfectly with the performance of this newly discovered object.
It is also possible that this mysterious GLEAM is evidence of the existence of a completely new object. So far, this object has only existed in theory, or it is a type that no astronomer has ever imagined.
"In the few hours we observed, the object appeared and disappeared. This was completely unexpected," the study's lead author — Natasha Hurley-Walker — a radio astronomer at Bentley Curtin University in Australia — said in the statement, "It's a little scary for astronomers because there's nothing known in the sky that would be like that." ”
The picture shows the location of this mysterious luminous object in the Milky Way. (Image source: Curtin, International Research Center for Radio Astronomy)
The last light of the dying star
There are usually two types of "transients". One is a "slow transient," which can appear within a few days and then disappear after a few months. Among them are supernovae — when dying stars break away from their outer atmosphere in a violent explosion, they emit a bright glow that gradually dims as the temperature of the star's remnants drops.
The other is "fast transients," which blink every few milliseconds. These include objects like pulsars (a type of neutron star) that rotate very fast while flashing bright radio radiation generated by the magnetic field of a dead star.
The authors of the new study discovered GLEAM when using the Murchison-Wildfield Array (MWA) radio telescope in the Australian outback to look for transient phenomena like this. The researchers say GLEAM's one-minute-long brightening pattern can't explain these phenomena; the switch flickers too fast to be a supernova; too slow to be a pulsar.
After analyzing the object, we learned that it is very bright, but from Earth it is smaller than the sun. According to the researchers, GLEAM's radio radiation is also highly polarized (that is, their light waves vibrate only on one plane), suggesting that they are generated by extremely strong magnetic fields.
These features match a theoretical object known as an ultra-long period magnetar, which is essentially a highly magnetized neutron star that spins very slowly. The researchers said that while the rare object was predicted to exist, it had never been observed in space before.
"Nobody expected to detect such stars directly because we didn't expect them to be so bright," Hurley-Walker said. "It somehow converts magnetic energy into radio waves, much more efficient than anything we've seen before."
"There may be other explanations for the mysterious GLEAM phenomenon," the researchers add. It may be a rare type of white dwarf , ( a dead star with insufficient mass to collapse into a neutron star ) that rarely emits radio signals by absorbing the energy of a binary companion star. The researchers say that if such a star rotates at the correct speed, it could jump like GLEAM.
We need further observations in other wavelengths of the electromagnetic spectrum to solve this star mystery. Now that GLEAM has been discovered, researchers are also studying archived observations of MWA to see if any similar objects have ever appeared.
Related knowledge
A pulsar (from a pulse-injecting power source)[1][2] is a highly magnetized rotating neutron star whose magnetic poles emit electromagnetic radiation. This radiation can only be observed when a beam of radiation is directed at the Earth (similar to a lighthouse, where light can only be observed when it is pointed in the direction of the observer), which is also what causes pulse emission to appear. Neutron stars are dense and have short and regular rotation periods, which produces a very precise pulse interval. For a single pulsar, the pulse interval varies from milliseconds to seconds. Pulsars are among the candidates for ultra-high-energy cosmic ray sources. (See Centrifugal acceleration mechanism.) )
The cycles of pulsars make them a very useful tool for astronomers. Observations of pulsars in neutron star systems indirectly confirm the presence of gravitational radiation. In 1992, the first extrasolar planet was discovered around the pulsar PSR B1257+12. In 1983, it was discovered that some pulsars were even more accurate in timing than atomic clocks at the time.
Supernova (/su p r no v/; pl. supernovae /-vi / or supernovas; Abbreviated SN and SNe) is a powerful and bright stellar explosion. This ephemeral astronomical phenomenon occurs in the final evolutionary phase of massive stars, or when white dwarfs are triggered into runaway nuclear fusion. The original objects, known as "ancestors," either collapsed into neutron stars or black holes or were completely destroyed. The peak luminosity of a supernova can rival that of an entire galaxy, and then fade away over a period of weeks or months.
Supernovae are more energetic than novae. In Latin, "nova" means "new", and astronomically refers to a new bright star that has temporarily appeared. The addition of the prefix "super-" distinguishes supernovae from ordinary supernovae, which are far less luminous than the former. The term supernova was coined by Walter Budd and Fritz Zwicky in 1929.
BY： Brandon Specktor
FY：Astronomical volunteer team
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