Astronomers Detect Rare Giant Flare from Magnetar

April 27, 2024

Scientists have detected the most distant-known instance of a giant flare from a magnetar, a type of neutron star with immensely strong magnetic fields, residing in the Messier 82 (M82) galaxy, also known as the “Cigar Galaxy.” The flare, a surge of gamma rays, released an amount of energy equivalent to 10,000 years of our sun’s output in just a tenth of a second.

Magnetars and Giant Flares

Magnetars are a class of neutron stars, the compact remnants of massive stars, that possess the strongest magnetic fields ever measured in the universe. Occasionally, they produce enormous eruptions of gamma rays called giant flares, which are the most powerful nondestructive energy releases known in the cosmos.

Only two confirmed giant flares have been observed in the Milky Way galaxy (in 2004 and 1998) and one in the neighboring Large Magellanic Cloud (in 1979).

Detection and Confirmation

The giant flare from the M82 galaxy was detected by the European Space Agency’s Integral space observatory on Nov. 15, 2023. Follow-up observations by the XMM-Newton space telescope confirmed that the flare was not associated with a short gamma-ray burst, which would have been caused by events like the merger of two neutron stars. The absence of an X-ray afterglow and gravitational waves supported the magnetar giant flare hypothesis.

Significance of the Discovery

The discovery of the M82 giant flare marks the most distant known occurrence of such an event, as M82 is located 12 million light-years from Earth. The flare’s origin in a “starburst galaxy” like M82, which has a high star formation rate, is significant because it confirms that massive stars in these regions “live fast and die young,” leaving behind young, turbulent, and rapidly spinning magnetars.

Magnetar Formation and Characteristics

Magnetars form when massive stars (at least eight times the mass of the sun) exhaust their nuclear fuel and collapse, resulting in a supernova explosion.
The stellar core is compressed into an extremely dense neutron star, with a mass of 1-2 solar masses packed into a sphere no larger than 12 miles (20 km) in diameter.
This rapid collapse leads to high rotational speeds (up to 700 times per second) and intense magnetic fields, the strongest in the universe.

Future Research

The discovery of the M82 giant flare opens up the search for more extragalactic magnetars, particularly in starburst galaxies. By studying more magnetars, scientists hope to better understand the frequency of these flares, how these stars lose energy in the process, and the evolution of neutron stars over time. This research will also provide insights into the lives and deaths of massive stars in regions of intense star formation.

The detection of the giant flare from the magnetar in the M82 galaxy is a significant milestone in the study of these extreme cosmic objects and their role in the evolution of stars and galaxies.

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