A spiral galaxy that acts as a natural microwave laser

the gist

UGC 6093 is a barred spiral galaxy with arms that swirl out from a bar across its centre. It is also an active galaxy, meaning its core holds a supermassive black hole pulling in surrounding gas. As that gas heats up, it can drive a natural amplifier that emits microwaves instead of visible light. This is called a megamaser, the galactic version of a maser, a microwave laser. Megamasers can be some 100 million times brighter than the masers found in galaxies like the Milky Way. Hubble's wide-range camera can image the same galaxy in near-infrared, visible and near-ultraviolet light, which helps untangle its complexity.

how it works

A supermassive black hole pulls in gas that forms a disc, and the intense radiation from that disc can pump molecules, such as water, into a population inversion. When those molecules drop back to lower energy states, they emit coherent microwaves, amplifying in a chain much like a laser. In megamasers the path is long and dense enough to produce huge brightness.

so what

Megamasers are powerful probes of black holes, because their microwave signals can reveal the motion of gas close to the central engine. They show how extreme conditions in galactic centres can produce lasers on a cosmic scale.

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 ↗