From UPSC perspective, the following things are important :
Prelims level : Event Horizon Telescope (EHT), Black Hole
Mains level : Not Much
A new research says that M87* which was imaged by the Event Horizon Telescope (EHT) is not necessarily a black hole but could even be a naked singularity with a gravitomagnetic monopole.
- In 2019, astronomers of the Event Horizon Telescope (EHT) captured the first ever image of a supermassive black hole (M87*) which was located at the centre of a galaxy Messier 87.
- This black hole was calculated to be 6.5 billion times the Sun’s mass and is 55 million light years away from the Earth.
- The discovery set the world of astronomy on fire and also found a mention in the “popular information” section of the announcement of the Nobel Prize in physics for 2020.
- Andrea Ghez and Rheinhard Genzel were awarded half the share of the prize for their study of the black hole at the centre of the Milky Way galaxy, Sagittarius A*.
A black hole has two parts:
- Singularity at its core– a point that is infinitely dense, as all the remnant mass of the star is compressed into this point.
- Event horizon – an imaginary surface surrounding the singularity, and the gravity of the object is such that once anything enters this surface, it is trapped forever.
- Not even light can escape the pull of the singularity once it crosses the event horizon.
- That is why, we cannot see the singularity at the heart of a black hole but only see points outside the event horizon.
- Hence, all the physics happening within the black hole’s event horizon is indeed blocked from the view of the observer.
What is the recent explanation of M87*?
Ans. Naked Singularity
- When stars much more massive than the Sun reach the end of their lives, they collapse under their own gravity, and the product of this collapse is a black hole.
- In many scenarios of stellar collapse, the event horizon does not form, and the singularity is exposed to the outside, without any event horizon shielding it.
- This is called naked singularity.
Monopoles and gravity
- In the nineteenth century, James Clerk Maxwell unified electricity and magnetism as one combined phenomenon, showing that light is an electromagnetic wave.
- But there is an asymmetry between electricity and magnetism.
- While positive and negative electric charges can be found to exist independently, the poles of a magnet are always found in pairs, north and south bound together.
- There is an analogy between gravitational force and electromagnetism to say that mass is like electric charge and can exist independently, thus it can be called a “gravito-electric charge”.
But then, what is the gravito-magnetic charge?
- In 1963, Newman, Tamburino and Unti (NUT) proposed a theoretical concept called a “gravito-magnetic charge” also called a gravitomagnetic monopole.
- The new research has shown that M87* could be a black hole (with or without gravitomagnetic monopole) or a naked singularity (with or without gravitomagnetic monopole).
Try this PYQ:
Q. “Event Horizon” is related to:
(b) Black hole
(c) Solar glares
(d) None of the above
Post your answers here.
Back2Basics: Event Horizon Telescope (EHT)
- The EHT project is an international partnership formed in 2012.
- It is a network of 10 radio telescopes on four continents that collectively operate like a single instrument nearly the size of the Earth.
- Its main objective is to directly observe the immediate environment of a black hole.
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