A dying Sun-like star has blown a glowing bubble half a light-year wide

the gist

When a Sun-like star runs out of fuel, it sheds its outer layers, and the glowing shell left behind is called a planetary nebula. The Little Gem, NGC 6818, lies about 6,000 light-years away and spans just over half a light-year. Its central star is tiny compared with the cloud, so the gas dominates the view. The shape is uneven, with knotty filaments and layers, because the ejection is not symmetrical. A fast stellar wind from the central star pushes the gas outward and carves bright blowouts where it smashes into slower material.

how it works

The star's core heats up and its outer envelope is puffed away. The fast stellar wind then catches up with the slower gas already ejected and sweeps it into a shell. Collisions between fast and slow gas create the bright, dense knots at the edges.

so what

Planetary nebulae show how stars like the Sun end their lives, and they are a major way that material forged in stars is returned to the galaxy. Imaging at different wavelengths, as Hubble does here, reveals the chemistry and structure of the gas.

the bigger pattern

Planetary nebulae are the Sun's eventual future: in several billion years the Sun is expected to shed its outer layers in this way. Much of the carbon in living things was forged inside stars, and planetary nebulae return that material to space.

fun fact

The name planetary nebula was coined by William Herschel in 1785, because the round shapes looked like planets through small telescopes.

ESA/Hubble · CC BY 4.0

Image: ESA/Hubble & NASA Acknowledgement: Judy Schmidt ( geckzilla.com )

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 ↗