Astronomers Shed Light on the Mystery of Missing Twin Stars at the Center of Our Galaxy

by Manuel Costa
stellar binaries

A captivating image taken by the Hubble Space Telescope showcases the binary stars Alpha Centauri A and Alpha Centauri B, located in the constellation of Centaurus. These stellar twins, situated 4.3 light-years away from us, orbit a shared center of gravity every 80 years, maintaining an average distance equivalent to 11 times the span between Earth and the sun. The discovery of such binary pairs, however, has eluded astronomers in the vicinity of the supermassive black hole residing in the heart of our Milky Way galaxy.

In a surprising departure from the norm, scientists from the University of California, Los Angeles (UCLA) and the W. M. Keck Observatory have scrutinized more than ten years’ worth of data pertaining to 16 young supermassive stars encircling the colossal black hole. Their analysis, published recently in the Astrophysical Journal, defies expectations, revealing that all 16 stars are solitary entities.

This revelation raises several intriguing questions: Why are these stars, which are approximately ten times larger than our sun, forming independently in the harsh environment surrounding the black hole? Have their stellar counterparts been forcibly expelled by the gravitational influence of the black hole? Or have these pairs of stars merged into solitary entities?

The findings lend support to a scenario in which the supermassive black hole compels nearby binary star systems to merge or undergo disruption, resulting in the expulsion of one of the stars from the system.

Dubbed S-stars, the observed stars are predominantly youthful, having formed within the past 6 million years, and boast considerable mass. They are primarily concentrated within a distance equivalent to a light-month, or nearly 500 billion miles, from the black hole.

“It’s astonishing to witness stars this young in such proximity to the black hole. They couldn’t have migrated to this region within a mere 6 million years. The emergence of a star in such an inhospitable environment is truly remarkable,” remarked Devin Chu, a UCLA postdoctoral scholar and the study’s lead author.

Chu and his colleagues employed data acquired using Keck’s adaptive optics instruments to conduct a groundbreaking search for spectroscopic binary stars among the S-stars. Spectroscopic binary stars appear as singular objects when observed through optical telescopes, but scientific analysis of the light they emit reveals their true binary nature.

Remarkably, all the S-stars that appeared solitary were indeed single stars.

The researchers made an even more intriguing discovery: The number of possible pairs of S-stars near the black hole was significantly lower than the number of comparable stars within the region surrounding our sun, known as the solar neighborhood.

This conclusion was reached by calculating a metric called the binary fraction, which represents the number of stars that could potentially exist in pairs within a given area. A higher binary fraction indicates a greater likelihood of star pairs. Previous studies have shown that the binary fraction for stars resembling the S-stars in our solar neighborhood is around 70%. In the present study, however, the researchers found that near the black hole at the center of the Milky Way, the upper limit was just 47%, indicating that the extreme environment surrounding the black hole curtails the survival of binary star systems.

“This disparity highlights the incredibly unique nature of the galactic center. We are dealing with an environment that defies normal expectations. Moreover, it suggests that the black hole actively drives the merging or disruption of binary stars in its vicinity, which holds significant implications for the production of gravitational waves and the ejection of hypervelocity stars from the center of our galaxy,” explained Chu.

The UCLA researchers now plan to further investigate how the calculated limit on the binary fraction compares to the binary fraction for similar stars located at greater distances from the black hole, albeit still within its gravitational influence.

Reference: “Evidence of a Decreased Binary Fraction for Massive Stars within 20 milliparsecs of the Supermassive Black Hole at the Galactic Center” by Devin S. Chu, Tuan Do, Andrea Ghez, Abhimat K. Gautam, Anna Ciurlo, Kelly Kosmo O’neil, Matthew W. Hosek Jr., Aurélien Hees, Smadar Naoz, Shoko Sakai, Jessica R. Lu, Zhuo Chen, Rory O. Bentley, Eric E. Becklin and Keith Matthews, 11 May 2023, Astrophysical Journal.
DOI: 10.3847/1538-4357/acc93e

Frequently Asked Questions (FAQs) about stellar binaries

Q: What did astronomers discover about the supermassive stars near the Milky Way’s black hole?

A: Astronomers discovered that all 16 young supermassive stars near the black hole are single, not binary. This suggests that the black hole’s influence causes the disruption or merging of stellar binaries, leading to a lack of twin stars in that region.

More about stellar binaries

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GalaxyExplorer June 18, 2023 - 10:45 am

So, these scientists studied those big stars near the black hole and turns out they’re not paired up like they should be. It’s like they got kicked out by the black hole or something. The black hole’s a troublemaker!

CosmicWonder June 18, 2023 - 11:53 am

Whoa! Stars that are supposed to be born in pairs are going solo near that massive black hole. Like, why? Did the black hole mess things up? Maybe it’s messing with their gravity or something. Mind-blowing!

SpaceEnthusiast99 June 18, 2023 - 2:27 pm

Hold up! Astronomers just discovered that these supermassive stars near the black hole are all loners. No twins in sight! It’s like the black hole is playing matchmaker and breaking them up. Fascinating, right?

Stargazer123 June 18, 2023 - 4:19 pm

omg! Astronomers found out that all those massive stars near the black hole are alone! No twinsies for them. Whoa, so does the black hole gobble up their twins or what? Crazy stuff!

AstroGeek June 19, 2023 - 2:02 am

Woah, woah, woah! Brace yourselves! These scientists dug into the data and guess what? All those mega stars near the black hole are going solo, no duos in sight! Looks like the black hole is wrecking their binary vibes. Mind = blown!


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