The Universe Is Not So Chaotic: New Findings on Galaxy Collisions
The number of violent collisions between large galaxies is only about one-tenth of previously estimated figures, according to a recent announcement by an Australian researcher.
Dr. Alister Graham from the Research School of Astronomy and Astrophysics at the Australian National University in Canberra has published his study in the latest issue of the Astrophysical Journal Letters.
When two galaxies collide, the massive black holes at their centers enter a binary orbit around a central gravitational area. As this orbit decays, the black holes move closer together, and their immense gravitational pull begins to engulf nearby stars.
Stars continue to be “consumed” in this manner until the mass absorbed equals or exceeds the total mass of the black holes.
In the past, direct observations of galaxies led to the speculation that such collisions must be quite frequent in the universe to accumulate enough mass for the massive black holes we observe at the centers of galaxies.
However, according to Graham, researchers have focused solely on galaxies born from collisions, neglecting those that have remained intact and have not had their “insides” devoured.
Using the Hubble Space Telescope, Graham studied a group of galaxies located 100 million light-years away. He compared the mass of black holes at the centers of collided galaxies with the available star mass in galaxies that have not undergone “war”.
Graham found that these intact galaxies have sufficient star mass to create a massive black hole, even after just one collision with another galaxy. “Previously, we believed that it would take ten collisions to achieve this,” he stated.
Graham’s research provides the first direct evidence supporting a hypothesis that astronomers have utilized in their cosmological models for over a decade. Their previous observations did not align with this hypothesis.
Thuận An (via ABC Online)
