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Dark Matter and Tiny Black Holes [Prelims Bits]

Tags: Prelims Current events of national and international importance

Source: The Hindu

Context: A study suggests that ultra-heavy dark matter captured by dense stellar remnants could collapse into tiny black holes and eventually destroy their host stars.
Dark matter: Invisible matter inferred mainly from its gravitational effects; unlike ordinary matter, it does not significantly interact with electromagnetic radiation.
Objects studied: Millisecond pulsars and white dwarfs, both extremely dense stellar remnants.
Proposed process: Ultra-heavy dark matter particles → accumulate at stellar core → gravitational collapse → tiny black hole → feeds on stellar matter → may consume the star.
Tiny black hole: Could initially have a mass as low as about 40 tonnes; normally, very small black holes would rapidly lose mass through Hawking radiation.
Hawking radiation: Theoretical quantum effect through which black holes lose mass and can eventually evaporate; smaller black holes evaporate faster.
Dark-matter feeding: A continuous supply of captured dark matter could allow the tiny black hole to grow faster than it evaporates.
Natural laboratories: Long-lived millisecond pulsars and white dwarfs can help constrain the properties of ultra-heavy dark matter that is difficult to test experimentally on Earth.
Pulsar: A pulsar is a highly magnetised, rapidly rotating neutron star whose radiation beams can appear as regular pulses when directed toward Earth.

Q1. Consider the following pairs:

Object/Phenomenon	Characteristic
1. Millisecond pulsar	Rapidly rotating neutron star with extremely regular observed pulses
2. White dwarf	Dense stellar remnant that can serve as a laboratory for studying dark-matter effects
3. Hawking radiation	Quantum effect associated with mass loss and possible evaporation of black holes
4. Dark matter	Matter whose presence is established primarily through its strong interaction with electromagnetic radiation

How many of the above pairs are correctly matched?

(a) Only one
(b) Only two
(c) Only three
(d) All four

Answer: (c)

Explanation:

Pair 1 is correctly matched: A pulsar is a rapidly rotating, highly magnetised neutron star whose radiation can be observed as periodic pulses.
Pair 2 is correctly matched: White dwarfs are extremely dense stellar remnants and can potentially constrain properties of ultra-heavy dark matter.
Pair 3 is correctly matched: Hawking radiation theoretically causes black holes to lose mass, with sufficiently small black holes potentially evaporating rapidly.
Pair 4 is incorrectly matched: Dark matter is characterised by its lack of significant electromagnetic interaction, while its gravitational effects provide major evidence for its existence.