In 1916, Karl Schwarzchild theorized the existence of black holes as a solution to Einstein’s field equations for his General Theory of Relativity.
In the mid-20th century, astronomers first began to detect black holes using indirect methods, which involved observing their effects on surrounding objects and space.
Since the 1980s, scientists have studied supermassive black holes (SMBHs), which reside at the center of most massive galaxies in the Universe. And in April 2019, the Event Horizon Telescope (EHT) collaboration released the first ever image of an SMBH.
These observations are an opportunity to test the laws of physics under the most extreme conditions and provide insights into the forces that shaped the Universe.
According to a recent study, an international research team used data from ESA’s Gaia Observatory to observe a Sun-like star with strange orbital characteristics. Due to the nature of its orbit, the team concluded that it must be part of a binary black hole system.
This makes it the closest black hole to our Solar System and implies the existence of a sizeable population of dormant black holes in our galaxy.
The research was led by Kareem El-Badry, a Harvard Society Fellow astrophysicist at the Harvard-Smithsonian Center for Astrophysics (CfA) and the Max Planck Institute for Astronomy (MPIA).
They were joined by researchers from CfA, MPIA, Caltech, UC Berkeley, the Flatiron Institute’s Center for Computational Astrophysics (CCA), the Weizmann Institute of Science, the Paris Observatory, the Kavli Institute of Astrophysics and Space Research from MIT and various universities.
The paper describing their findings will be published in the Monthly Notices of the Royal Astronomical Society.
As El-Badry explained to Universe Today via email, these observations were part of a larger campaign to identify dormant black hole companions in normal stars in the Milky Way.
“I have been searching for latent black holes for the past four years using a wide range of data sets and methods,” he said.
“My previous attempts resulted in a wide variety of binaries masquerading as black holes, but this was the first time the search paid off.”
For the sake of this study, El-Badry and his colleagues relied on data obtained by the Gaia Observatory of the European Space Agency (ESA). This mission has spent nearly a decade measuring the positions, distances, and proper motions of nearly 1 billion astronomical objects, including stars, planets, comets, asteroids, and galaxies.
By tracking the motion of objects as they orbit the center of the Milky Way (a technique known as astrometry), the Gaia mission aims to build the most accurate 3D space catalog ever created.
For their purposes, El-Badry and colleagues examined the 168,065 Gaia Data Release 3 (GDR3) stars that appeared to have two-body orbits.
Their analysis found a particularly promising candidate, a G-type (yellow star) designated Gaia DR3 4373465352415301632; for their purposes, the team designated it Gaia BH1. From its observed orbital solution, El-Badry and his colleagues determined that this star must have a binary black hole companion.
El-Badry said: “The Gaia data constrains how the star moves across the sky, tracing an ellipse as it orbits the black hole. The size of the orbit and its period constrains the mass of its invisible companion, approximately 10 solar masses.
“To confirm that Gaia’s solution is correct and to rule out alternatives other than black holes, we observed the star spectroscopically with several other telescopes. This tightened our constraints on the companion’s mass and showed that it is indeed ‘dark’ .
To confirm their observations, the team analyzed Gaia BH1’s radial velocity measurements from several telescopes.
This included the High Resolution Echelle Spectrometer (HIRES) at the WM Keck Observatory, the Fiber-Feed Extended Range Optical Spectrograph (FEROS) at the MPG/ESO telescope, the X-Shooter spectrograph at the Very Large Telescope ( VLT), the Gemini multi-object spectrographs. (GMOS), the Magellan Echellette Spectrograph (MagE) and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST).
Similar to the method used to hunt for exoplanets (Doppler spectroscopy), the spectra provided by these instruments allowed the team to observe and measure the gravitational forces influencing their orbit. These follow-up observations confirmed the orbital solution of Gaia BH1 and that a companion of approximately 10 solar masses was co-orbiting with it.
As El-Badry indicated, these findings could constitute the first black hole in the Milky Way that was not observed based on its X-ray emissions or other energetic emissions:
“Models predict that the Milky Way contains about 100 million black holes. But we’ve only observed about 20. All the previous ones we’ve observed are in ‘X-ray binaries’ – the black hole is eating a companion star ., and glows brightly in X-rays as the gravitational potential energy of this material is converted to light.
“But these only represent the tip of the iceberg: a much larger population may be lurking, hidden in more widely separated binaries. The discovery of Gaia BH1 shines the first light on this population.”
If confirmed, these findings could mean that there is a robust population of dormant black holes in the Milky Way. This refers to black holes that are not evident from bright disks, bursts of radiation, or hypervelocity jets emanating from their poles (as is often the case with quasars).
If such objects are ubiquitous in our galaxy, the implications for stellar and galactic evolution could be profound. However, it is possible that this particular latent black hole is an outlier and not indicative of a larger population.
To verify their findings, El-Badry and his colleagues look forward to the yet-to-be-determined Gaia 4 (GDR 4) data release, which will include all data collected during the nominal mission. five years old (GDR 4). ).
This release will include the most up-to-date astrometric, photometric and radial velocity catalogs for all observed stars, binaries, galaxies and exoplanets.
The fifth and final version (GDR 5) will include data from the nominal and extended mission (the full 10 years).
“Based on the rate of occurrence of accompanied BHs implied by Gaia BH1, we estimated that the upcoming release of Gaia data will enable the discovery of dozens of similar systems,” said El-Badry.
“With a single object, it’s hard to know exactly what it implies about the population (it could be something weird, a fluke). We’re excited about the population demographic studies we’ll be able to do with larger samples.”
This article was originally published by Universe Today. Read the original article.