Discovery of Nearby Black Holes: Gaia’s Breakthrough Observations

Sub : Sci

Sec: Space sector

Why in News

Astronomers have discovered a massive black hole, Gaia BH3, relatively close to Earth. It is the largest known stellar-mass black hole in the Milky Way and was identified using data from the European Space Agency’s Gaia telescope. This discovery enhances our understanding of black holes and their formation.

About Black Holes:

Black holes are regions in space where gravity is so intense that nothing, not even light, can escape.
They are usually detected through their gravitational influence on nearby stars or through the X-ray emissions produced when matter falls into them.
However, some black holes remain ‘silent,’ with no X-ray emissions, making them difficult to detect.
Identifying Black Holes:
- Orbital Motion Analysis: When a visible star orbits a black hole, it appears to be moving around empty space.
- Doppler Effect Observations: Ground-based telescopes detect shifts in the star’s light spectrum, revealing changes in velocity.
- Mass Estimation: By analysing the star’s orbit using Kepler’s third law, astronomers infer the mass of the unseen object.
Formation: Black holes form when massive stars collapse at the end of their life cycle. This can happen through:
Supernova Explosions: Some high-mass stars explode, leaving behind black holes.
Direct Collapse: In some cases, stars collapse into black holes without an explosion.
Neutron stars, which form from less massive stars, have a maximum limit of around three solar masses. If an unseen companion exceeds this threshold, it must be a black hole.

About Gaia Telescope:

Launched by the European Space Agency (ESA) in 2013, Gaia is a space observatory designed to chart a three-dimensional map of the Milky Way.
Measure the positions, distances, and motions of approximately one billion stars with unprecedented precision. Study the composition and evolution of our galaxy.

Gaia’s Role in Black Hole Discovery:

The European Space Agency’s Gaia telescope has been monitoring billions of stars since 2013. By tracking their motion, Gaia helps identify anomalies indicating the presence of invisible massive objects like black holes.
The latest discovery, Gaia BH3, adds to the previous findings of Gaia BH1 and Gaia BH2, reinforcing the telescope’s crucial role in uncovering hidden black holes.

Gaia’s First Black Hole Discovery: Gaia BH1

Location: 1,560 light-years away, making it the closest known black hole to Earth.
A star was found orbiting an unseen massive object every six months. Data from the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST) and Magellan Clay Telescope in Chile confirmed rapid motion.
Kepler’s third law calculations indicated a mass nine times that of the Sun, confirming it as a black hole.

The Second Discovery: Gaia BH2

Approximately nine solar masses. Identified through a similar technique of tracking a visible star’s motion around an invisible massive object.

The Largest Stellar-Mass Black Hole: Gaia BH3

Discovery in April 2024.
33 solar masses, surpassing the previous record-holder Cygnus X-1 by 12 solar masses. 2,000 light-years, located in the constellation Aquila.
A nearby yellow giant star orbits Gaia BH3 every 11.6 years at a distance comparable to that between the Sun and Uranus.
First black hole found in the outer Milky Way. It appears ‘passive,’ meaning it does not actively pull in matter or emit X-rays.

First Galactic Equivalent of LIGO-Detected Black Holes:

In 2015, LIGO and VIRGO detected gravitational waves from black holes of similar mass merging in distant galaxies (1-2 billion light-years away). Gaia BH3 provides a local counterpart for in-depth study.

Kepler’s Laws of Planetary Motion:

First Law (Law of Ellipses): Planets orbit the Sun in elliptical paths, with the Sun located at one focus of the ellipse.
Second Law (Law of Equal Areas): A line connecting a planet to the Sun sweeps out equal areas during equal intervals of time, indicating that planets move faster when closer to the Sun and slower when farther away.
Third Law (Law of Harmonies): The square of a planet’s orbital period is proportional to the cube of the semi-major axis of its orbit, establishing a relationship between the time a planet takes to orbit the Sun and its average distance from the Sun.

LIGO (Laser Interferometer Gravitational-Wave Observatory):

Detect gravitational waves—ripples in spacetime caused by massive cosmic events like merging black holes or neutron stars.

Consists of two facilities in the United States, located in Hanford, Washington, and Livingston, Louisiana.
In 2015, LIGO made the first direct detection of gravitational waves, confirming a major prediction of Einstein’s general theory of relativity.

Virgo Detector:

A large interferometer located near Pisa, Italy, designed to detect gravitational waves.
Works in conjunction with LIGO and KAGRA to form a global network of gravitational wave observatories.
Participated in the joint detection of gravitational waves from merging neutron stars and black holes, enhancing the ability to localize and study these cosmic events.