NGC 5643: Secrets of a spiraling galactic powerhouse

Today’s Image of the Day from the European Space Agency features the spiral galaxy NGC 5643, which is located roughly 40 million light-years away in the constellation Lupus. 

NGC 5643 belongs to the Hubble classification SBc, indicating that it is a barred spiral galaxy with loosely wound arms. 

Its orientation, nearly face-on to Earth, provides astronomers with an exceptional view of its detailed spiral structure and central bar.

NGC 5643: A grand design spiral 

“NGC 5643 is what’s known as a grand design spiral, referring to how the galaxy’s two large, winding spiral arms are clear to see,” noted ESA. “The spiral arms are defined by bright blue stars, lacy reddish-brown dust clouds and pink star-forming regions.”

“As fascinating as the galaxy appears at visible wavelengths, some of NGC 5643’s most interesting features are invisible to the human eye.” 

Intense activity in NGC 5643

This galaxy is notable for its Seyfert 2 nucleus, a type of active galactic nucleus (AGN). The intense activity in its core is powered by a supermassive black hole that accretes surrounding material, emitting energy across a wide range of wavelengths. 

“When a supermassive black hole ensnares gas from its surroundings, the gas collects in a disc that heats up to hundreds of thousands of degrees. The superheated gas shines brightly across the electromagnetic spectrum, but especially at X-ray wavelengths,” said ESA.

Observations have revealed jets and outflows of material emanating from the nucleus, likely driven by the black hole’s activity. 

NGC 5643’s AGN has been studied extensively for its role in galactic evolution, particularly in how its energetic processes interact with the galaxy’s interstellar medium.

The mystery of NGC 5643 X-1

However, ESA pointed out that NGC 5643’s active galactic nucleus isn’t the brightest source of X-rays in the galaxy. 

“Researchers using ESA’s XMM-Newton discovered an even brighter X-ray-emitting object, called NGC 5643 X-1, on the galaxy’s outskirts. What could be a more powerful source of X-rays than a supermassive black hole?” 

“Surprisingly, the answer appears to be a much smaller black hole! While the exact identity of NGC 5643 X-1 is not yet known, evidence points to a black hole that is about 30 times more massive than the Sun.” 

“Locked in an orbital dance with a companion star, the black hole ensnares gas from its stellar companion, creating a superheated disc that outshines the galactic center,” said ESA.

Star formation in NGC 5643

NGC 5643 also exhibits prominent regions of star formation within its spiral arms. These areas are rich in gas and dust – the raw materials for birthing new stars – and glow brightly in ultraviolet and infrared light. 

Observations from the Hubble Space Telescope and the Very Large Telescope (VLT) have helped uncover the complex interplay between star formation and the galaxy’s central activity.

Extended ionized gas regions 

A defining feature of NGC 5643 is the presence of its extended ionized gas regions, which are shaped by the galaxy’s AGN activity and star-forming regions. 

These structures have been mapped through optical spectroscopy, revealing intricate patterns that help astronomers understand the physical conditions of the gas, such as density, temperature, and composition.

The galaxy also has a dust lane that crosses its nucleus, partially obscuring direct observations of the central region in visible light. 

Overall, NGC 5643 offers a fascinating glimpse into the dynamics of barred spiral galaxies with active nuclei, serving as a valuable resource for studying the interactions between supermassive black holes, star formation, and galactic evolution.

The constellation Lupus

Lupus is a constellation located in the southern sky, its name meaning “wolf” in Latin. It has been known since antiquity and was cataloged by the Greek astronomer Ptolemy. 

Once part of the larger constellation Centaurus, Lupus was later recognized as a distinct constellation. It is relatively faint but holds historical significance in mythology, often associated with a sacrificial wolf in ancient stories.

Lupus is bordered by other constellations like Scorpius, Centaurus, and Libra. Its stars do not form a particularly striking pattern, but it contains a variety of interesting astronomical features. Among them are numerous double stars, globular clusters, and other deep-sky objects, visible through telescopes. 

For observers in the Southern Hemisphere, Lupus is best seen in the winter and spring months, while it appears closer to the horizon for those in northern latitudes.

This constellation also lies along the Milky Way, offering a rich field of stars and nebulae for stargazers. Despite its modest brightness, Lupus holds a special place in the science of astronomy.

Image Credit: NASA/ESA Hubble Space Telescope

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