Dead stars could break one of physics' most famous limits

from ScienceDaily

A surprising new discovery suggests that some dead stars can grow far more massive than scientists once thought possible. Computer simulations show that powerful magnetic fields could allow white dwarfs to reach 2.4 times the mass of the Sun, dramatically exceeding a famous limit that has stood for decades. The findings could help explain unusually bright supernova explosions that have long puzzled astronomers.

explained

The Chandrasekhar limit is the maximum mass of a stable white dwarf star. These stars resist gravitational collapse primarily through electron degeneracy pressure, compared to main sequence stars, which resist collapse through thermal pressure. The Chandrasekhar limit is the mass above which electron degeneracy pressure in the star's core is insufficient to balance the star's own gravitational self-attraction. The value of the Chandrasekhar limit depends upon the ratio of the number of electrons to nucleons (neutrons plus protons) in the star. For small stars this ratio is around 1/2 and the limit is about 1.44 M☉. The limit was named after Subrahmanyan Chandrasekhar who won the 1983 Nobel prize together with William Alfred Fowler for work on stellar models.

From Wikipedia: Chandrasekhar limit (CC BY-SA 4.0) ↗

so what

The usual limit, about 1.4 solar masses, underpins how Type Ia supernovae are used as cosmic distance markers, so heavier white dwarfs could change how we read the universe.

fun fact

Subrahmanyan Chandrasekhar worked out his limit as a young man on a ship sailing from India to England.

Hampi was once one of the world's largest cities, until its Vijayanagara capital was destroyed in 1565

the gist

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.

how it works

The city was built around a fortified core with temples, markets and water structures along the river, supplied by an extensive network of roads and waterworks. When the empire fell, the city was not rebuilt, so its stone monuments were left standing.

so what

Hampi shows how quickly a great city can vanish after a military defeat, and how a ruined capital can remain sacred. Its ruins give historians a view of medieval South Asia that few other sites can match.

fun fact

The name Hampi comes from Pampa, an old name for the Tungabhadra River.

From Wikipedia, the free encyclopedia · text CC BY-SA 4.0

Image: Wikimedia Commons

source: Wikipedia ↗

2 min

politicsshortCNA2:01

False allegations about Singapore’s hand in Indonesia’s markets and a made-up meeting

from CNA

CNA Verify has found close to 400 posts pushing falsehoods tying Singapore to Indonesia’s stock market rout and to a secret meeting that never took place. Together, they drew nearly 12 million views, and some were circulated by accounts that appeared to be working in concert, across multiple social media platforms.

Here’s how the disinformation campaign targeting Singapore was uncovered.

on YouTube: CNA ↗