UPSC Daily Current Affairs | Prelim Bits 01-10-2024

Earth's Future after Red Giant Phase of Sun

The recent discovery of earth like planet orbiting a white dwarf is getting a sneak peek at the future of the Solar System, and the fate of Earth.

• Rocky planet – It comes in at around 1.9 times the mass of Earth, orbiting its star at around twice Earth's distance from the Sun.
• The star is a white dwarf which means any life that might have been on the exoplanet was probably obliterated before or during the star's red giant death throes.
• White dwarf – It began as an ordinary star 1 or 2 times the mass of the sun and its current mass is about half the sun.
• Distance of Orbiting – Before its host star's death, it orbited at a distance, possibly placing it in the habitable zone.
• Following its star's demise, it is at 2.1 times that distance.
• Current state of the planet - It's currently a freezing world because the white dwarf, which is in fact smaller than the planet, is extremely faint compared to when it was a normal star.
• Significance of the finding – It offers insight into Earth’s potential survival after sun’s death.

• Research modeling shows that this planet very likely had a similar orbit to Earth before its host star became a red giant.
• It implies that Earth's chances for survival may be higher than currently thought.

Reference

Science Alert| Earth like Planet Orbiting a Dwarf Star

White Dwarf

A recent study using Hawaii-based telescopes, found the 1^st rocky planet that is orbiting the white dwarf about 4,200 light years away from our solar system near the bulge at the center of the Milky Way galaxy.

• White Dwarf – It is the stellar core left behind after a dying star has exhausted its nuclear fuel and expelled its outer layers to form a planetary nebula.
• It is the last observable stage of evolution for low- and medium-mass stars.

Stars having a larger mass may end their lives as black holes or neutron stars. A light year is the distance light travels in a year, about 5.9 trillion miles.

• Conditions for formation – Stars with a mass less than 8 times the sun.
• Formation – It is formed when a low-mass star like our sun exhausts most of its nuclear fuel.
• Composition - Compared to our sun, it has a similar carbon and oxygen mass though it is much smaller in size.
• Features - It is about as massive as the Sun, yet only slightly bigger than the Earth.
• It is one of the densest forms of matter, surpassed only by neutron stars and black holes.
• Temperatures - It can exceed 100,000 Kelvin according to NASA.
• They no longer support nuclear fusion reactions that generate energy, but they are still extremely hot.

White Dwarfs cool over time, and it is predicted that they would ultimately form ‘black dwarfs’, although the Universe is likely not old enough for any black dwarfs to exist yet.

• Luminosity - Despite having too high a temperature, they have a low luminosity as they’re so small in size.
• It luminosity can be used by astronomers to measure how long ago star formation began in a particular region.

Hubble was the 1^st telescope to directly observe white dwarfs in globular star clusters in 2003, which astronomers reported as the dimmest stars ever seen in a globular star cluster.

References

1. The Hindu| Planet Orbiting a White Dwarf
2. ESA Hubble| White Dwarfs

Khur

Khur have recently overcome a near-extinction event.

• It is an Indian Wild Ass, a species of ass that is native to the countries of southern Asia.
• It is one of the 4 remaining subspecies of the Asian Wild Ass.
  • Scientific name - Equus hemionus khur
  • Other local terms – Ghudkhur or Indian onager
• Range – Earlier it extended from Southern India towards southern Pakistan, Afghanistan and south-eastern Iran.
• Now, it can only be found in India.
• Features – It is almost the size of a zebra, and lives for 21 years.
• Stable groups consist of females and their young while Stallions tend to be loners, especially in the breeding season.
• On the flat terrain of the Rann, they are capable of bursts of up to 70 km per hour.
• Their gestation periods are long, 11 to 12 months, and concurrent lactation and pregnancy is sometimes seen.
• Feed – It predominantly feeds on grasses.

Surra is an infection in Indian Wild Ass caused by the protozoan parasite Trypanosoma evansi and spread by biting insects

• Threat – Increased human presence for salt farming, agriculture coupled with extensive cattle grazing, has led to their dispersal.
• Irrigation canals that bring water to the southern rim of the Little Rann can also add salinity to the soil.
• Conservation status
  • IUCN – Endangered
  • Wildlife Protection Act 1972 – Schedule I
• Conservation – India has declared a Wild Ass Sanctuary in Little Rann of Kutch, the largest sanctuary in Gujarat.
• It was set up in 1973, only remaining habitat of the Indian wild ass.
• About 6,000 of these sandy and brown creatures live in this area.

Reference

The Hindu| Survival of Khur in India’s Salt Desert

The Rann of Kutch

• It is reputed to be one of the largest salt deserts in the world.
• Location – It lies at the end of the Gulf of Kutch in Gujarat.
• Size – It is about 7500 km² in area.
• Evolution – It evolved when waters of the Arabian Sea made incursions into this region 150-200 million years ago.
• Geological upheavals led to the rise of a landmass that cut off the Kutch basin from the sea.
• Types – It is divided into the Little Rann and the Big Rann.

• Landscape – For most of the year, it consists of vast, barren desiccated, unbroken bare surface of dark silt, encrusted with salts.
• It is also known for ecologically important Banni grasslands
• Landscape changes - A striking alteration occurs when the monsoon sets in, and the Rann turns into a shallow wetland.

The Rann of Kutch can be considered a large ecotone, a transitional area between marine and terrestrial ecosystems.

• Bets – About 75 elevated pieces of land turn into islands, called bets by the local Agariya and Maldhari communities.
• The largest plateau is called Pung.
• Economic significance – The salt marsh attracts human enterprise, 30% of India’s salt comes from the Little Rann.

Reference

The Hindu| India’s Salt Desert