A Sun-Like Star Found Orbiting A Black Hole

A Sun-Like Star Found in the Orbit of a Black Hole
A Sun-Like Star in the Orbit of a Black Hole - Gaia BH1 is a Sun-like star co-orbiting a black hole estimated to be 10 times the mass of the Sun. Credits: ESO/L. Found in Calcada

Karl Schwarzchild proposed the possibility of black holes in 1916 as a solution to the field equations of Einstein's general theory of relativity. In the mid-20th century, astronomers first developed indirect methods of studying the effects of black holes on objects and space around them. Supermassive black holes (SMBHs) at the heart of most large galaxies in the universe have been the subject of scientific study since the 1980s. The first photo of an SMBH was released by the Event Horizon Telescope (EHT) consortium in April 2019.

These observations offer the chance to put the principles of physics to the ultimate test and provide new insights into the forces that created the universe. A recent article claims that an international research team has observed a sun-like star with strange orbital characteristics using data from ESA's Gaia Observatory. Based on the characteristics of its orbit, the researchers concluded that it must be a component of a black hole binary system. This indicates that there are a significant number of inactive black holes in our galaxy, making it the closest black hole to our solar system.

Kareem El-Badry, an astronomer affiliated with the Harvard-Smithsonian Center for Astrophysics (CfA) and the Max Planck Institute for Astronomy, served as the study's principal investigator (MPIA). He was joined by researchers from the CfA, MPIA, Caltech, UC Berkeley, the Flatiron Institute Center for Computational Astrophysics (CCA), the Weizmann Institute of Science, the Observatoire de Paris, the Kavli Institute for Astrophysics and Space Studies at MIT, and numerous other institutions. Monthly Notices of the Royal Astronomical Society will publish the paper detailing their findings.

These studies are part of a larger effort to find inactive black hole neighbors to regular stars in the Milky Way galaxy, El-Badry told Universe Today by email. “I have been looking for hidden black holes for the past four years using various datasets and techniques,” El-Badry said. This is the first time this search has yielded results, although my previous attempts have yielded a large number of binaries referred to as black holes.

El-Badry and colleagues used data from the European Space Agency (ESA) Gaia Observatory for their research. Nearly 1 billion astronomical objects, including stars, planets, comets, asteroids and galaxies, have been measured by this project over nearly a decade. The Gaia project aims to create the most accurate 3D space catalog ever made by tracking the motion of objects as they rotate around the center of the Milky Way (a process known as astrometry).

For their research, El-Badry and colleagues examined all 3 stars in Gaia Data Broadcast 3 (GDR168.065) that appear to orbit two bodies. As a result of their investigation, they discovered a G-type (yellow star) star known as Gaia DR3 4373465352415301632, which they named Gaia BH1 for their purpose. Based on the observed orbital resolution, El-Badry and colleagues concluded that this star must have a black hole binary. El-Badry said:

“The motion of the star in the sky is constrained by Gaia measurements, which suggests that the star orbits the black hole in an elliptical fashion. Based on the orbit's size and period, we can set a limit to the mass of its invisible companion—about 10 solar masses. We used three more telescopes to make spectroscopic observations of the star to confirm the accuracy of the Gaia solution and rule out non-black hole alternatives. This helped us tighten our restraints on the comrade's mass and showed that he was truly "black".

To support their observations, the scientists studied Gaia BH1's radial velocity readings from various telescopes. High Resolution Echelle Spectrometer (HIRES) at the WM Keck Observatory, Fiber-fed Extended-Range Optical Spectrograph (FEROS) in the MPG/ESO telescope, X-Shooter spectrograph in the Very Large Telescope (VLT), Gemini Multi-Object Spectrographs (GMOS), Magellan Echellette (MagE) and Big Sky Field Multi-Object Fiber (LAMOST).

The spectra obtained with these equipment allowed the researchers to see and analyze the gravitational forces affecting its orbit, a technique similar to the technique used to find exoplanets (Doppler Spectroscopy). These additional observations confirmed the orbital resolution of Gaia BH1 and the presence of a companion in its orbit, estimated to be around ten solar masses. As El-Badry points out, these discoveries may represent the first black hole in the Milky Way not seen due to X-ray emissions or other energetic releases:

“According to the models, there are 100 million black holes in the Milky Way. But we've only seen about 20 of them so far. All we've seen before are what are known as "X-ray binaries," when a black hole swallows a co-star and the ingested matter is emitted heavily in X-rays as a result of its gravitational potential energy. However, this is just the tip of the iceberg; there may be a much larger population lurking in more distant binaries. The discovery of Gaia BH1 sheds some advance light on this population.”

These results, if confirmed, would indicate that the Milky Way has a sizable population of inactive black holes. By this we mean black holes without bright disks, bursts of radiation, or hypervelocity jets from their poles (as is often the case with quasars). If these are common in our galaxy, they could have important implications for how stars and galaxies evolve. But it is possible that this particular inactive black hole is an anomaly and not representative of the general population.

El-Badry and colleagues look forward to Gaia Data Release 4 (GDR 4), which will include all data collected during the five-year nominal mission, with an as-yet-unknown publication date. The latest catalogs of astrometric, photometric and radial velocity for all observed stars, pairs, galaxies and exoplanets will be included in this release. Data from nominal and extended missions will be included in the fifth and final release (GDR 5). (full ten years).

According to El-Badry, "the next Gaia data release will enable dozens of similar systems to be found", based on the rate of BH comrade formation proposed by Gaia BH1. “It is difficult to pinpoint what an item means about the population (it might just be a quirk, a fluke). We look forward to doing population demographic research with larger samples.”

Source: phys.org/news

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