The Milky Way’s Dark Centre
The Milky Way’s Dark Centre
Subject: Science and Technology
Section: Space
Context: Sagittarius A* (SgrA*), this region is believed to host a supermassive black hole of about 4 million times the solar mass.
Concept:
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy’s appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.
The Event Horizon Telescope is an international collaboration capturing images of black holes using a virtual Earth-sized telescope.
The Event Horizon Telescope is not just a single telescope. It consists of a consortium of eight powerful telescope arrays around the world given below, which together made up a giant eye, the size of the Earth and 3 million times sharper than the human eye.
Atacama Large Millimetre/sub-millimetre Array,- Atacama Pathfinder Experiment,
- IRAM 30-metre telescope,
- James Clerk Maxwell telescope,
- Large Millimetre Telescope Alfonso Serrano,
- Submillimetre Array,
- UArizona Submillimetre Telescope and
- South Pole Telescope.
The image looks at the massive object that sits at the very centre of our galaxy. Scientists had previously seen stars orbiting around something invisible, compact, and very massive at the centre of the Milky Way. This strongly suggested that this object — known as Sagittarius A* (Sgr A*, pronounced “sadge-ay-star”) — is a black hole, and this image provides the first direct visual evidence of it.
What is this black hole?
A black hole is a location in space with a gravitational pull so strong that nothing, not even light, can escape it. A black hole’s outer edge, called its event horizon, defines the spherical boundary where the velocity needed to escape exceeds the speed of light. Matter and radiation fall in, but they can’t get out.
Black hole’s shadow
The gas moving around the black hole emits light, which takes a curved path around the black hole and this leaves a central dark portion, referred to as the “shadow” of the black hole. This effect happens because of the enormous gravity of the central region. Thus, this image is an attestation of Einstein’s General Relativity theory.
What is naked singularity?
A naked singularity is a hypothetical gravitational singularity without an event horizon. In a black hole, the singularity is completely enclosed by a boundary known as the event horizon, inside which the gravitational force of the singularity is so strong that light cannot escape.
What is a wormhole?
A wormhole is a speculative structure linking disparate points in spacetime, and is based on a special solution of the Einstein field equations. A wormhole can be visualized as a tunnel with two ends at separate points in spacetime.
How far is the event horizon from a black hole?
The size of a black hole is defined by its event horizon – a distance from the center of the black hole within which nothing can escape. Scientists had previously been able to calculate that Sagittarius A* is 16 million miles (26 million kilometers) in diameter.
What is the reason for using a Long Baseline interferometry (VLBI)?
VLBI is a powerful technique in radio astronomy. By linking together widely separated radio telescopes, VLBI allows astronomers to see the universe in more detail than ever.
What is Messier 87?
Messier 87 (also known as Virgo A or NGC 4486, generally abbreviated to M87) is a supergiant elliptical galaxy with several trillion stars in the constellation Virgo. One of the most massive galaxies in the local universe.