Astronomers have been puzzled by a glowing blob that appears to be inside one of the enormous gamma-ray emanations from the center of our galaxy.
In new research published in Nature Astronomy, we show that the cocoon is caused by a group of millisecond pulsars located in the Sagittarius dwarf galaxy. While our results clear up the mystery of the cocoon, they also cast a pall over attempts to look for dark matter in any glow it emits.
It was seeing with the rays.
Our atmosphere protects us from the rays of the sun. These particles of light are more powerful than the ones we see.
Scientists had no idea of the beauty of the sky until instruments were lofted into space. More and more of the richness has been revealed thanks to the discoveries made by the Vela satellites.
The state-of-the-art instrument operating today is the Fermi Gamma Ray Space Telescope. A number of surprises have been uncovered by the ability of Fermi to detect faint sources.
There are mysterious bubbles.
There was a surprise in 2010 when something in the center of the Milky Way blew a pair of bubbles. 10% of the sky is covered by theseFermi bubbles.
There is a chance that the source of the bubbles is a black hole. This monster is 4 million times larger than the sun and is located in the center of the universe.
Black holes are found in most of the galaxies. Black holes are active in some cases. They simultaneously emit outflowing "jets" visible across the spectrum.
Researchers wondered if they could find a smoking gun tying the bubbles to the black hole. There was a hint of a jet pointing back towards the center of the universe.
This picture became muddy with time and further data. The jet-like feature in one of the bubbles was confirmed, but the other appeared to evaporate under scrutiny.
There was a bright spot in one of the bubbles, but no one else.
Where it comes from and how it came from.
The nature of thecocoon is examined in Nature Astronomy. This structure has nothing to do with the bubbles or the black hole.
The southern bubble is actually caused by rays from the Sagittarius dwarf galaxy which are visible from the position of Earth.
The constellation of Sagittarius is where the Sagittarius dwarf is located. The remnant of a larger galaxy is the cause of the strong field that has torn apart. There are stars pulled out of the Sagittarius dwarf that can be seen in the sky.
What's going on?
Cosmic rays, which are high-energy particles, collide with the gas between the stars to create the main source of gamma rays.
The process can't explain the radiation from the Sagittarius dwarf. The same harassment that took away so many of its stars caused it to lose its gas.
Where do the rays originate?
They are thought to be a signature of dark matter, a substance that is invisible to the naked eye but which is thought to make up most of the universe. Dark matter isn't the origin because the shape of the cocoon matches the distribution of visible stars.
The stars were responsible for the radiation. The Saggitarius dwarf's stars are old. Which type of source produces the radiation?
The radio waves are millisecond.
There is only one way to see rapidly spinning objects. These are the remnants of stars that are much larger than the sun.
A neutron star is an object about as heavy as the sun but only 20 km across and rotates hundreds of times per second.
The rapid rotation and strong magnetic field of the neutron stars make them a natural particle accelerators.
The particles emit radiation.
There is a search for dark matter.
We discovered that millisecond pulsars are sources of gamma rays in other stellar systems.
They cast a pall over efforts to find evidence for dark matter by showing that there is a stronger "background" of gamma rays from millisecond pulsars.
Any signal they produce may not be interpreted as dark matter.
There is a search for dark matter signals.
More information: Roland M. Crocker et al, Gamma-ray emission from the Sagittarius dwarf spheroidal galaxy due to millisecond pulsars, Nature Astronomy (2022). DOI: 10.1038/s41550-022-01777-x Journal information: Nature AstronomyUnder a Creative Commons license, this article is re-posted. The original article is worth a read.
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