Science News - Twinkle Twinkle Little Star, How I wonder what you will become

Twinkle Twinkle Little Star, How I wonder what you will become

They say you either die a hero or live long enough to become a villain. Stars are similar, some after shining light their whole lives end up becoming black holes and trapping any light that comes near them. In search of finding how many of these stars become merging black holes,. astrophysicists Karan Jani of Vanderbilt University in Nashville, TN and Abraham Loeb of Harvard University in Cambridge, MA used L.I.G.O data along with added constraints and published a study on January 31st, 2020 in the Astrophysical Journal Letters. Their research concerns the question of how many stars eventually become black holes as well as how black holes become binary systems (two black holes that circle one another till they collide). The study places estimates that 14% of all stars are destined to merge as black holes and it helps uncover some of the history and reasoning behind our very universe alongside guiding further observations. After all as Sean McWilliams an astrophysicist at West Virginia University responded in an email, "black holes are objects made of pure gravitational energy, with no messy matter to get in the way."

L.I.G.O stands for Laser Interferometer Gravitational-Wave Observatory. This observatory detects catalytic cosmic events such as black hole mergers given the fact that these collisions cause giant gravitational waves which can be detected using sensitive sensors. As of now, L.I.G.O has publicly announced over 40 binary black holes (BBH) events, of which 10 are confirmed detections. However, as a result of these continued observations and data, two questions arise. First, how is it that black holes are produced from stellar processes, and secondly, how are black holes brought together such that they merge in a universe whose age is finite. The latter question appears given the consideration of how long (10 billion years) it would take for black holes at some distance such as from the Sun to Mercury to push together.

These became the guiding questions in the researchers’ study and using the assumption that all the black hole systems observed by L.I.G.O were stellar black holes meaning created due to the death of a star collapsing into itself to create a singularly. In addition with the fact that stars birth rates were known, they analyzed and derived a global stellar budget. The methodology behind how they derived the answer to the question of what is the maximum budget for producing mergers of binary black holes from stellar evolution considered multiple astrophysical constraints. Initially, the discussion of available stars in the universe at a given time was presented, then it was further limited by the process and possibility of the star becoming an individual black hole. Finally, the consideration of the data of the eventual black hole mergers and how it is that two black holes got near enough to collide was added onto the previous deduction to reach a final answer.

The researchers came to the conclusion that at most 14% of all stars in the universe are destined to collide as black holes which is considered to be very efficient on nature’s part. Lead researcher Karan Jani also says, "one of the key findings was … the stars that created black holes were one of the earliest stars that were born in the universe."

Black holes are permanent members of the universe because once created they stay as such, even with mergers occurring. Extensions and plans for future observation include two new L.I.G.O centers being built, one in India as well as one in Japan. Furthermore along the line LISA will be the first space-based gravitational wave detector allowing us to look at even more cosmic collisions and black holes, furthering our understanding on the framework of the universe.

References

Jani, K., & Loeb, A. (2020). Global Stellar Budget for L.I.G.O Black Holes. The Astrophysical

Journal, 889(2).