Hubble photographs a galaxy cluster whose light has taken over 5 billion years to reach us

the gist

The cluster PLCK G004.5-19.5 was first found by ESA's Planck satellite through the Sunyaev-Zel'dovich effect, a shadow that hot electrons in cluster gas cast on the cosmic microwave background, the afterglow of the Big Bang. The brightest galaxy sits at the centre, and a thin curved arc above it is a gravitational lens, where the cluster's mass bends the light of galaxies behind it. Everything else visible is a distant galaxy, redshifted by the expansion of the universe. Hubble imaged the cluster as part of the RELICS survey, which looked for the brightest distant galaxies for the James Webb Space Telescope to study.

how it works

Hot electrons in a cluster's gas scatter photons of the cosmic microwave background, leaving a small dip in its temperature in that direction, which Planck detects. Gravitational lensing happens because mass bends spacetime, so light from galaxies behind the cluster curves around it and forms arcs and multiple images.

so what

Massive clusters act as natural magnifiers, letting telescopes see galaxies that would otherwise be too faint. Surveys like RELICS find those targets so that later telescopes, such as Webb, can study the early universe in detail.

ESA/Hubble · CC BY 4.0

Image: ESA/Hubble & NASA, RELICS

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 ↗