by Astronomers believe they have discovered a massive, rare flare from a dead, highly magnetic star, or magnetar, that was bright enough to illuminate an entire galaxy. If true, the discovery would mark the first time gamma rays from a “recently deceased” neutron star erupting outside the Milky Way have been seen.
The flare was first seen by the Integral Science Data Center in Geneva in the form of a short burst of high-energy X-rays that lasted only a tenth of a second. Integral alerted astronomers who realized, just 13 seconds after the burst, that these gamma rays appeared to be coming from the bright galaxy Messier 82 (M82), known as the “Cigarette Galaxy” because on its elongated shape; The Cigar Galaxy is located approximately 12 million light years from Earth.
All this, however, left a mystery for the astronomers to solve. Was this the fairly common gamma-ray burst they were seeing from this galaxy, which also has intense star formation, or was it the flare of a highly magnetic field?
Related: One of the most ‘extreme’ stars died unexpectedly
“We immediately understood that this was a special alert,” said Sandro Mereghetti, head of research and scientist at the National Institute for Astrophysics (INAF-IASF), in a statement. “Gamma-ray bursts come from far away and anywhere in the sky, but this burst came from a bright galaxy nearby.”
To investigate a gamma-ray flare, Mereghetti and colleagues made quick observations of the source of the burst with the XMM-Newton space telescope. They reasoned that if this gamma-ray burst was a short gamma-ray burst created by a powerful event like two neutron stars smashing together and merging, then an associated afterglow should be visible in x-rays and visible light. . This event would also set off a space-time “ring” with ripples known as “gravitational waves.”
“The XMM-Newton observations only showed the hot gas and stars in the galaxy,” said INAF team member and researcher Michela Rigoselli. “If this burst had been a short gamma-ray burst, we would have seen a fading source of X-rays coming from its location, but this aftershock was not present.”
Integral’s role in enabling researchers to get off track in investigating this gamma-ray burst was — excuse me in advance — central to determine its true origin and trace it back to a magnetar eruption in M82.
“When unexpected observations like this are collected, Integral and XMM-Newton can be flexible in their schedules, which is essential in time-critical discoveries,” explained Integral project scientist Jan-Uwe Ness in the statement. “In this case, if the observations were made even a day later, we wouldn’t have such strong proof that this is indeed a magnetar and not a gamma-ray burst.”
A dead magnet and flames
Magnetars are a type of neutron star notable for their extremely powerful magnetic fields. Like all neutron stars, magnetars are born when a star with at least eight times the mass of the sun consumes the fuel they need for nuclear fusion at their core. This eliminates the outward force associated with radiation pressure that has kept these stars from collapsing under their own gravity for millions, if not billions, of years.
When this protection is removed, the core of this dying star collapses and the outer layers that make up most of the star’s mass are exploded in a supernova explosion. The result is the core of a dead star with a mass of one to two times that of the sun falling in at a width of no more than 12 miles (20 kilometers).
The result of this rapid collapse is that neutron stars are made up of the densest matter in the universe, which if brought to Earth would be only a tablespoon weighing 1 billion tonnes. This fall has two other major consequences, too.
Just as an ice skater on Earth takes advantage of the conservation of angular momentum by pulling in their arms to increase their spin speed, the rapid radial contraction of the core of a dying star causes a newborn neutron star to spin at an incredible speed. Some young neutron stars have been found to spin as fast as 700 times per second.
Also, the collapse causes the magnetic field lines of the star’s core to tighten closer together. The closer the field lines, the stronger the magnetic field. That means some neutron stars have the most powerful magnetic fields in the entire cosmos. The rotational speed and intensity of neutron stars decrease as these stellar remnants age.
“Some young neutron stars have extra strong magnetic fields, more than 10,000 times greater than normal neutron stars. These are called magnetars. They release energy in flares, and sometimes those flares are huge,” another researcher said. of the European Space Agency, Ashley Chrimes. said.
It is thought to be because when “quakes” on the surface of these young, highly magnetic neutron stars disrupt their strong magnetic fields, magnetar flares are both massive and extremely rare.
In the 50 years since the cosmos was observed in gamma rays, mankind has experienced only three flares. Those were found in 1979, 1998 and 2004, and all came from magnetars located in the Milky Way.
But, perhaps it is fortunate that blister magnets are rare. The example seen in December 2004, caused by a magnet 30,000 light years from Earth, was so powerful that it affected our planet’s upper atmosphere. The effect was similar to that caused by solar flares, but the sun is 1.9 billion times closer to Earth than the magnetar behind the gamma-ray flare of 2004. Let that sink in.
The Holographic discovery marks the first time a flare from a magnetar outside the Milky Way has been seen. However, the team thinks that some of the other short gamma-ray bursts seen by Integral were also flares from extraterrestrial magnetars.
“However, such short bursts can only be caught serendipitously when an observatory is already pointing in the right direction,” said Jan-Uwe. “This makes Integral, with its large field of view, more than 3,000 times greater than the sky area covered by the moon, so important for the sensors.”
RELATED STORIES:
— A new approach could help scientists see inside a neutron star
— Dead star ‘glitches’ could reveal the origin of fast radio bursts
— The heaviest neutron star ever seen is shredding its companion
The location of the magnetar in M82 is significant as this bright galaxy has experienced a burst of intense star formation. This confirms that, in such starburst regions, massive stars “live fast and die young,” leaving young neutron stars as turbulent, fast-spinning magnetars.
The team will now search for more magnetars in star galaxies to help better understand the lives and deaths of massive stars in these regions, and to better understand how neutron stars evolve over time. time.
“This discovery opens our search for other extragalactic magnetars,” said Chrimes. “If we can find enough more, we can begin to understand how often these flares occur and how these stars lose energy in the process.”
The team’s research was published on Wednesday (April 24) in the journal Nature.
