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
13 Aug 2026 · Prelims
The solar corona
A total solar eclipse crossed Greenland, western Iceland, northern Spain, north eastern Portugal and northern Russia, Europe's first in 27 years and not seen from India. Totality is what makes such a track worth travelling to, because it is still the best way to see the Sun's corona from the ground.
- A solar eclipse happens only at new moon, when the Moon passes between the Earth and the Sun.
- The inner corona is too faint to see against the glare of the solar disc.
- A coronagraph blocks that disc artificially, but scattered light often spoils the view.
- Only in totality, seen from the narrow path of totality, does the Moon block the whole disc.
- The corona's magnetic field drives solar flares and coronal mass ejections, which disturb satellites, navigation and communications on Earth.
The Hindu, 13 Aug 2026: Total solar eclipse over northern Spain (opens in a new tab)
6 Sep 2026 · Prelims
Saturn's south pole
Saturn's north pole carries a long lasting six sided wave, known as the hexagon, and nothing of the kind had been found at the other pole. Scientists have now reported a ten sided wave, a decagon, around the south pole, the first found there.
- It drifts slowly eastward.
- It may be formed by unstable winds or by a nearby anticyclone.
30 Aug 2026 · Prelims
Betelgeuse
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.
The Hindu, 30 Aug 2026: Betelgeuse may have a companion star (opens in a new tab)
2 Sep 2026 · Prelims
The Nancy Grace Roman Space Telescope
The National Aeronautics and Space Administration (NASA) launched the Nancy Grace Roman Space Telescope on 30 August, to survey dark energy, dark matter and exoplanets. Most of what it is sent to measure cannot be seen at all, which is why it carries two instruments rather than one.
- About 5% Ordinary matter. Stars, planets, gas, us
- About 27% Dark matter. Unseen mass holding galaxies together
- About 68% Dark energy. Speeding up the expansion
Wide Field Instrument
- An infrared camera
- Maps galaxies through gravitational lensing, the bending of light by the gravity of unseen mass in between
Coronagraph
- Blocks starlight to reveal planets around stars
- It works from Lagrange Point 2, as the James Webb Space Telescope does, while Hubble orbits the Earth.
10 Sep 2026 · Prelims
Dark matter inside dead stars
Dark matter is detected only through its gravitational pull, so a proposal about what it is has to be tested by what it would do to things already visible. One such thing is a star that has finished burning and is still there.
- An Indian study proposed that ultra heavy dark matter captured inside a dead star could collapse into a tiny black hole that swallows it.
- It looks at millisecond pulsars and white dwarfs, where dark matter falling in outweighs what the black hole loses to Hawking radiation.
- Many such stars have lasted billions of years, which rules out dark matter that would have destroyed them sooner.
Also filed elsewhere
- Space weather forecasting from Aditya-L1 · on Moon, Sun and planetary missions
A solar flare gives no useful warning once it has erupted, because its radiation crosses to Earth in about eight minutes.
- The Hanle Dark Sky Reserve · on Chemicals, noise, light and soil pollution
Ladakh's administration notified the Hanle Dark Sky Reserve (HDSR) in December 2022, India's first and still its only one.