A galaxy cluster weighing 180 trillion suns bends light like a lens

the gist

Galaxy clusters are some of the most massive structures in the universe, groups of galaxies bound together by gravity. The cluster MACS J0454.1-0300 has a mass estimated at around 180 trillion times that of the Sun. Its gravity bends the path of light passing through it, so galaxies behind it appear stretched into sweeping arcs. This gravitational lensing acts as a natural magnifying glass, making objects too faint to detect otherwise visible. Astronomers use the effect to study the early universe, and Hubble's Frontier Fields programme was set up to exploit it.

how it works

Mass warps spacetime, as Einstein's general relativity describes, so light passing a massive object follows a curved path. A cluster this massive bends light from galaxies behind it, which can focus and stretch their images. The stretching forms arcs, while the amplification brightens distant galaxies enough for telescopes to detect them.

so what

Lensing lets astronomers see galaxies from a much younger universe, which would be far too faint for current telescopes without the magnification. It also offers a way to weigh clusters directly, including their invisible dark matter.

the bigger pattern

Gravitational lensing was predicted by Einstein's general relativity and first confirmed in 1919, when starlight was observed bending around the Sun during a solar eclipse. Today lensing clusters are used to map dark matter, since the bending reveals mass whether or not it shines.

fun fact

In 1936 Albert Einstein published a paper predicting that a star could be magnified by another star passing in front of it, an effect he thought too faint ever to observe.

ESA/Hubble · CC BY 4.0

Image: ESA/Hubble & NASA Acknowledgement: Nick Rose

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 ↗