New Study Questions the Physicist's Hypothesis on Dark Matter

Scientists spent years and now have discovered that black holes are not the primary reason for the creation of dark matter as per the hypothesis of Stephen Hawking.

When we think black holes and dark matter, we think of Stephen Hawking. He singlehandedly unveiled numerous facts about black holes and his theories, the hypothesis is treasured by those who seek to discover more about the origin of the universe. The Big Bang and what happened after that is “the” unanswered question for cosmologists. Stephen Hawking stated that the universe is finite, and its origin is far simpler than the current theories of scientists related to the Big Bang. He also believed that black holes are the primary source of dark matter. However, not all agree with that.

An international team of researchers has published a paper that ruled out the most famous hypothesis of Stephen Hawking about the origin of dark matter. The paper was published in Nature Astronomy and the team–which included scientists from Japan, India, and the U.S.–reported their analysis on the nearest galaxy to the milky way, Andromeda galaxy. They claim that the source of dark matter was formed in the very beginning of the universe and black holes might not be the parent of the dark matter.

What was the hypothesis?

Scientists believed that dark matter pervades the entire universe. Although we have failed to detect it, its existence is undeniable as numerous celestial phenomena could never take place in the universe without the presence of dark matter in it. In fact, cosmologists believe that the dark matter makes up more than 85% of all universe. Moreover, Hawking worked on black holes to understand the origin of it and believed that black holes could form at the very beginning of the universe. Since the actual nature of dark matter remains enigmatic, he predicted that primordial black holes could behave like dark matter. however, the researchers found shreds of evidence that say otherwise.   

Why do scientists think Hawking is wrong?

To test any theories regarding dark matter and black holes, one must observe black holes and look for instances of “gravitational lensing” of the stars–the phenomenon of bending of light from a distant star due to extreme gravity or due to the existence of black holes. Long ago, Albert Einstein said that space is just like fabric and if there is a presence of celestial objects such as stars, plants, or black hole, the fabric of space-time becomes curved and the light traveling in the straight line would follow the curve of the fabric and thus, is observed as bent. Moreover, if light travels closer to the black hole, it appears magnified, which could be detected by a powerful telescope.

The team of scientists wanted to observe such instances of “gravitational lensing”. However, to observe such thing is a tricky task, as it requires not only the presence but also the perfect alignment of a black hole, a distant star, and an observer on the earth. The team used Hyper Suprime-Cam on the Japanese Subaru Telescope situated in Hawaii and focused on Andromeda galaxy. They collected about 190 images of the galaxy and spotted about 1,000 events to know whether dark matter was made up of primordial black holes. However, they could identify only one event of such kind, forcing them to question the veracity of Hawking’s hypothesis. In fact, researchers now propose that primordial black holes of the size of or less than that of the moon could not make up more than 1% of the total dark matter in the universe, which reopens the question of the origin of the dark matter once again.