Hubble caught a nearby white dwarf bending the light of a distant star, as Einstein predicted

the gist

Einstein's general relativity says mass warps space, so light passing a massive object curves along a bent path. Stein 2051B, a white dwarf only 17 light-years away, drifted in front of a star about 5000 light-years away. Hubble observed the pair eight times over two years, and the white dwarf's gravity shifted the background star's apparent position by about 2 milliarcseconds. That is roughly the size of an ant crawling across a euro coin seen from 2300 kilometres away. Ground telescopes cannot reach this precision, so it took a space telescope to see it.

how it works

When a foreground star passes almost exactly in front of a background star, its gravity bends the background star's light toward us, making the background star appear shifted and brightened. The effect is strongest when the alignment is nearly perfect and is measured by tracking the shift over time.

so what

It is a direct test of general relativity at a scale that was out of reach for a century, with a small, nearby star providing the lens. The method can also detect objects that give off no light.

fun fact

A white dwarf is the dense leftover core of a Sun-like star, after it has shed its outer layers.

more on this

background

Gravitational microlensing is an astronomical phenomenon caused by the gravitational lens effect. It can be used to detect objects that range from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers can only detect bright objects that emit much light (stars) or large objects that block background light (clouds of gas and dust). These objects make up only a minor portion of the mass of a galaxy. Microlensing allows the study of objects that emit little or no light.

When a distant star or quasar gets sufficiently aligned with a massive compact foreground object, the bending of light due to its gravitational field, as discussed by Albert Einstein in 1915, leads to two distorted images (generally unresolved), resulting in an observable magnification. The time-scale of the transient brightening depends on the mass of the foreground object as well as on the relative proper motion between the background 'source' and the foreground 'lens' object.

From Wikipedia: Gravitational microlensing (CC BY-SA 4.0) ↗

see

NASA and ESA, CC0, via Wikimedia Commons

NASA / ESA, Public domain, via Wikimedia Commons

ESA/Hubble · CC BY 4.0

Image: NASA, ESA, and K. Sahu (STScI)

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 ↗