A galaxy trailing star-forming tendrils shows how a cluster's hot gas can strip a galaxy

the gist

The jellyfish galaxy JW39 lies about 900 million light-years away in Coma Berenices and is moving through a galaxy cluster. Clusters are full of a very hot, thin plasma called the intracluster medium. As a galaxy moves through it, the gas acts like a headwind, pushing gas and dust out of the galaxy's disc. This process is called ram-pressure stripping, and it leaves long trailing ribbons that resemble jellyfish tentacles. Hubble's Wide Field Camera 3 studied these tails and found that star formation in the tentacles is not noticeably different from star formation in the galaxy's disc. Stripping leaves a galaxy with less gas to make new stars, so its star formation eventually slows.

how it works

A galaxy moving through the intracluster plasma feels a pressure that pushes against its gas. Where that pressure exceeds the gravity holding the gas in place, the gas is stripped away and streams behind the galaxy.

so what

The study shows that star formation can continue in the extreme conditions of stripped gas, which challenges assumptions about where stars can form. Jellyfish galaxies also provide a natural laboratory for how galaxies die out in dense clusters.

the bigger pattern

Galaxies in clusters are shaped by their environment, including gravitational tugs and gas stripping. Studies of interacting and stripped galaxies have been a major theme in extragalactic astronomy for decades.

ESA/Hubble · CC BY 4.0

Image: ESA/Hubble & NASA, M. Gullieuszik and the GASP team

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 ↗