快猫短视频

A mysterious gamma-ray glow in the inner parts of our galaxy could be due to thousands of dead stars spinning at hundreds of times a second. These millisecond pulsars are formed from the remnants of stars that have used up all their fuel, but now blast out radiation. A similar thing might also be happening in the nearby Andromeda galaxy.

The enigmatic glow, called the Galactic Centre Excess (GCE), was first identified in 2009. Since then, several ideas have emerged to describe how it might be formed. One hypothesis posits that the radiation is formed when dark matter particles meet and annihilate, releasing gamma-ray light, while another points the finger at millisecond pulsars. In the latter case, astronomers had largely been focusing on millisecond pulsars whose origins lie in binary star systems where one star has experienced a violent supernova explosion.

Now, at the Australian National University, Canberra, and his colleagues have suggested that another type of millisecond pulsar 鈥� those formed when a massive white dwarf rips material from a star before collapsing and transforming into a whirling pulsar 鈥� can produce a characteristic gamma-ray light that tallies with what astronomers see coming from the Milky Way鈥檚 central regions.

While that on its own doesn鈥檛 rule out dark matter annihilation as a possible source of the GCE, it does present an alternative phenomenon that can 鈥渆xplain the entirety of the signal鈥�, says Crocker. 鈥淢y own view is that the best interpretation now is that not only is the GCE astrophysical rather than dark matter in origin, we know the specific astrophysical sources responsible for it,鈥� he says.

This finding is complemented by a looking at a gamma-ray glow coming from the nearby Andromeda galaxy. at the Gravitation AstroParticle Physics Amsterdam Centre in the Netherlands and his colleagues created maps of where old stars are located within the galaxy, using these as an indicator for where millisecond pulsars are expected to exist. Adding this information to their model of gamma-ray production revealed that the potential contribution from the pulsars was enough to account for the level of gamma rays seen emanating from Andromeda, without the need to invoke the process of dark matter annihilation.

鈥淚n other words, there was no more 鈥榬oom鈥� for the dark matter, as almost all of the excess was already explained by the other components used in our study,鈥� says Zimmer.

Crocker believes future research will show that the glow from Andromeda is caused by the same type of millisecond pulsars that his team suggests causes the GCE. 鈥淚t鈥檚 entirely reasonable and, indeed, consistent with the evidence that both excesses share a similar origin,鈥� he says.

at King鈥檚 College London says the Cherenkov Telescope Array (CTA) project being built in Chile and the Canary Islands will observe the inner Milky Way to investigate the GCE further. 鈥淲ith its unprecedented sensitivity to gamma-ray signals, CTA will be key in determining if millisecond pulsars explain the excess gamma-ray emission, or if dark matter remains a viable contender.鈥�

CTA should also be able to help study Andromeda by looking for as-yet-undetected higher-energy gamma rays coming from any millisecond pulsars, says at the Erlangen Centre for Astroparticle Physics in Germany. 鈥淚f [the higher energies are] not detected, this can constrain the hypothesis that millisecond pulsars are responsible for the emission.鈥�

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