Science and Technology › Space

Astronomy and cosmology

Astronomy and cosmology: telescopes and observatories, stars, black holes and neutron stars, exoplanets, dark matter and dark energy, the Sun's cycle and space weather, eclipses, comets and asteroids. Prelims has asked about Cepheids, nebulae and pulsars, and about solar flares.

UPSC has asked

Prelims 2025: solar flares and coronal mass ejections striking the outer atmosphere
Prelims 2023: Cepheids, nebulae and pulsars
Prelims 2022: effects of a major solar storm on the Earth

Showing 1 of 5 subjects, those that changed from 16 to 31 August 2026.Show all

Betelgeuse

Prelims

Betelgeuse is a red supergiant in the constellation Orion whose brightness rises and falls on a six year cycle, for which there was no agreed explanation. Astronomers using the Very Large Telescope have found strong evidence of a close companion, named Betelgeuse B.

The companion appears to be a young star of about 2.6 to 3.1 times the Sun's mass.
It could explain the six year cycle, because it periodically blocks part of the star's light.
A second observation is awaited to confirm the finding.

What changed

30 Aug 2026
The Hindu, 30 Aug 2026: Betelgeuse may have a companion star (opens in a new tab)

corona: The Sun's outermost atmosphere, extending millions of kilometres into space and far hotter than the visible surface below it.

coronagraph: An instrument that blocks a bright disc so that what lies close beside it can be seen: the Sun's corona without an eclipse, or a planet beside another star.

coronal mass ejection: A huge burst of magnetised plasma thrown out of the corona into space, which can reach the Earth and disturb its magnetic field.

path of totality: The narrow strip on the Earth's surface from which the Moon is seen covering the Sun completely.

Lagrange Point 2: A point about 1.5 million km beyond the Earth, directly away from the Sun, where a spacecraft circles the Sun in step with it.

dark matter: Unseen matter that neither emits nor absorbs light and is detected only through its gravitational pull.

Hawking radiation: Radiation black holes are predicted to emit as they lose mass; smaller ones evaporate faster.

millisecond pulsar: A neutron star, the collapsed core of a dead star, spinning hundreds of times a second and sweeping a beam of radiation past Earth.

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