Subaru Telescope reveals the shape and temperature of Comet Encke's nucleus

science & techPhys.org

Subaru Telescope reveals the shape and temperature of Comet Encke's nucleus

from Phys.org

Mid-infrared observations with the Subaru Telescope have revealed the shape and surface temperature of the nucleus of Comet 2P/Encke. By analyzing how the nucleus's thermal emission changed as it rotated, the researchers found that the nucleus is elongated, with a long axis of about 7 kilometers and a short axis of about 3 kilometers. They also determined that the surface temperature at the time of observation was 328 ± 7 Kelvin (about 55°C).

explained

Comet Encke, or Encke's Comet (official designation: 2P/Encke), is a periodic comet that completes an orbit of the Sun once every 3.3 years. Encke was first recorded by Pierre Méchain on 17 January 1786, but it was not recognized as a periodic comet until 1819 when its orbit was computed by Johann Franz Encke. Like Halley's Comet, it is unusual in its being named after the calculator of its orbit rather than its discoverer. Like most comets, it has a very low albedo, reflecting only 4.6% of the light its nucleus receives, although comets generate a large coma and tail that can make them much more visible during their perihelion (closest approach to the Sun). The diameter of the nucleus of Encke's Comet is 4.86 km (3.02 mi).

It reaches opposition on 8 October 2026 when it will be about magnitude 15. It comes to perihelion on 10 February 2027 when it will have a solar elongation of 10 degrees.

From Wikipedia: Comet Encke (CC BY-SA 4.0) ↗

how it works

Sunlight heats the nucleus and it re-emits that energy as infrared. The emission depends on the surface area facing us and on temperature, so as the comet spins, the changing infrared brightness reveals its shape.

so what

A comet's nucleus is usually too small and too far away to see directly, so its size and temperature have to be inferred from heat. Those numbers show how fast it loses ice and how long it can survive.

fun fact

The meteor showers known as the Taurids are linked to debris from Encke.

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 ↗