Giant galaxy clusters bend light into arcs, and mergers keep the largest galaxies growing

the gist

A massive galaxy cluster bends light the way a lens does, so galaxies lying behind it get stretched into glowing arcs. This cluster, SDSS J1336-0331, works as a natural magnifying glass for studying distant galaxies. It was also part of a study of 42 brightest cluster galaxies, the giant elliptical galaxies at the centres of clusters. The study found these giants are fed by cold gas from their surroundings, and that their recent growth comes mostly from mergers, where two galaxies collide and combine.

how it works

Mass bends the path of light, so a cluster heavy enough acts like a lens. Light from galaxies behind it is distorted into arcs and sometimes multiple images. Astronomers use this effect to see faint, distant objects that would otherwise be too dim to detect.

so what

Brightest cluster galaxies are among the most massive and luminous galaxies in the universe, so how they grow reveals how large galaxies build up over billions of years. Mergers, rather than steady star formation, appear to drive their late growth.

ESA/Hubble · CC BY 4.0

Image: ESA/Hubble & NASA

source: ESA/Hubble ↗

historyWikipediaclassic1336–1565 · Karnataka, India

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 ↗