Several small newly discovered galaxies seem to be missing a whole lot of dark matter, and physicists are not sure of the reason behind it.
Most of a classic galaxy is invisible. This shifty mass is known as the dark matter, appears to be a key ingredient used for a galaxy formation - it is the scaffold that attracts normal matter - disclosed itself only as an extra gravitational pull on stars and gas, yet vents no light.
However, the research team has recently discovered that 19 dwarf galaxies - all are smaller compared to the Milky Way - decline this universal wisdom. These newly discovered galaxies have much less dark matter than expected. The findings in ‘Nature Astronomy’, more than quintuples the known population of dark matter defector, added fuel to an already approaching mystery.
Astrophysicist Qi Guo of Beijing’s Chinese Academy of Sciences said that “we are not sure why and how these galaxies form.” Usually, the dwarf galaxies concentrate dark matter far more than their elder galaxies, she noted. However, their small size leads to weaker gravity that has a problem holding on to shaky clouds of gas. It eventually shifts the balance of mass in dominated galaxies towards the dark matter.
England’s Durham University Astrophysicist Kyle Oman said that “this new class of galaxy is straining our ability to explain all galaxies in one cohesive framework.” However, Oman was not involved in this study.
In 2016, Oman, along with his colleagues, has discovered two galaxies that seemed to be missing the dark matter.
Guo and her mates wondered if these dwarf galaxies are more in number. Therefore, using the current information, the research team considered dwarf galaxies by looking at how fast hydrogen runs around each one. Hence, the higher speed indicates total mass. After this, they combined the mass of all the stars and hydrogen, assumed from starlight, to evaluate how much of its mass is made up of normal matter.
Therefore, for every galaxy, total mass included up to more than the mass of the stars and gas - don’t be surprised, as that extra mass is the dark matter. But in around 6 percent cases, there was not as much extra mass as predicted.
Meanwhile, designated AGC 213086 weighted at nearly 14 billion Suns. If it is typical, around 2 percent of its mass - almost 280 million solar masses - it would-be stars and gas. Instead, it is the actual record of normal matter is about 27 percent of its total mass or 3.8 billion solar masses.
Out of 324 dwarf galaxies analyzed, 19 seems to be missing the dark matter. Those are all within around 500 million light-years of Earth, and five are in or near other groups of typical galaxies. In those cases, the research team has noted, maybe their closest have somehow switched off their dark matter. But the remaining 14 dwarf galaxies are far away from others. Either these odds formed in a different way or some internal plots like exploding stars have hampered their balance of dark matter or baryons.
The University of California’s Astrophysicist James Bullock has stated that it might not be a case of missing dark matter. Still, these small galaxies have been stick to their normal matter or even have stolen some and so they “have too many baryons.” He further says, “This is telling us something about the diversity of galaxy formation...exactly what that’s telling us, that is the trick.”