Dark matter might look more familiar than we previously thought. A new study suggests that the mysterious particles might be analogous to protons and electrons in that they could lose energy, allowing them to clump together and form star-like or planet-like objects.
Astronomers have long noticed a crucial difference between dark matter and ordinary matter: one collapses and one doesn鈥檛. Ordinary atoms radiate away energy through a force called electromagnetism, allowing their orbits to shrink. If enough atoms do this, they collapse to form compact objects. That much is evident from the existence of stars, planets and even us.
Dark matter, however, does not appear to collapse. Instead, it only exists on the largest scales 鈥� in smooth, giant halos that surround galaxies. And if it doesn鈥檛 collapse, scientists assumed that it doesn鈥檛 feel the force of electromagnetism. 鈥淭hat鈥檚 a pretty good guess,鈥� says at the Fermi National Accelerator Laboratory in Batavia, Illinois.
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But at Rutgers University in Newark, New Jersey, suggests the guess might be incorrect. His team argues that dark matter might look like ordinary matter in that it might be composed of two types of charged particles 鈥� a heavy one like a proton and a light one like an electron. If true, the particles will certainly feel the force of electromagnetism.
Still a halo
This model still explains the large-scale halo around the Milky Way. That鈥檚 key, if it is to be considered as a possibility. But it also means that dark matter would be able to clump together to form 鈥榙ark objects鈥� analogous to stars and planets, says co-author at Rutgers University.
Maybe the halo of dark matter surrounding any galaxy isn鈥檛 smooth at all, like astronomers previously assumed, but is instead composed of these smaller substructures 鈥� much like the disk of the Milky Way is actually composed of smaller clumps of dust and stars.
Hooper is also hopeful that next-generation surveys will allow scientists to probe dark matter on smaller scales. Gravity from those smaller objects, for example will pull on stars, causing them to move ever so slightly toward the dark objects. That movement might be visible from telescopes such as the European Space Agency鈥檚 Gaia mission, which launched in 2013 to precisely pinpoint the positions of one billion stars in the Milky Way.
Should scientists find hints of dark objects within the Gaia dataset, especially ones that appear within the halo of dark matter encircling our galaxy, the observation would lend itself well to the new theory.
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