Today’s Image of the Day from the European Space Agency features the barred spiral galaxy NGC 3783, which is located about 130 million light-years away in the constellation Centaurus. NGC 3783 is also the most prominent of a galaxy group (by the same name) that contains 47 galaxies. 

Galaxy groups

“Like galaxy clusters, galaxy groups are aggregates of gravitationally bound galaxies. Galaxy groups, however, are less massive and contain fewer members than galaxy clusters do: where galaxy clusters can contain hundreds or even thousands of constituent galaxies, galaxy groups do not typically include more than 50,” noted ESA.

“The Milky Way is actually part of a galaxy group, known as the Local Group, which contains two other large galaxies (Andromeda and the Triangulum galaxy), as well as several dozen satellite and dwarf galaxies.”

HD 101274: A blue giant star

The bright object that appears to the right of the galaxy is the star HD 101274. “The perspective in this image makes the star and the galaxy look like close companions, but this is an illusion. HD 101274 lies only about 1,530 light-years from Earth, meaning it is about 85 thousand times closer than NGC 3783,” explained ESA. 

The star is part of the NGC 3766 cluster, which is sometimes referred to as the Pearl Cluster, an open cluster known for its richness in bright stars and its relatively young age.

HD 101274 is categorized as a blue giant star, characterized by its high temperature and luminosity.

Blue giants are massive stars that have left the main sequence phase of stellar evolution and are burning helium or heavier elements in their cores. These stars are known for their short lifespans relative to smaller stars due to their rapid consumption of nuclear fuel.

Significance of blue giants

Stars like HD 101274 are important for astronomers because they help in studying the properties of stellar populations in clusters and the dynamics of stellar evolution in different environments.

The spectral and photometric observations of such stars can provide valuable insights into the characteristics of their atmospheres, internal structures, and the processes occurring within and around them.

Bright central region of NGC 3783

One of the most interesting aspects of NGC 3783 is that it harbors an active galactic nucleus, meaning its central region is exceptionally luminous, likely due to the presence of a supermassive black hole. This black hole is actively accreting material, which emits a substantial amount of radiation as it spirals inward and heats up.

The galaxy is particularly known for its bright central region and has been studied extensively in the ultraviolet and X-ray light spectra to understand better the properties of the accretion disk around the black hole and the complex dynamics of the material surrounding it. These studies are crucial for understanding the physics of active galactic nuclei and the role they play in galaxy evolution.

According to ESA, NGC 3783 is a Type I Seyfert galaxy. “In this image it is recorded by Hubble in incredible detail, from its glowing central bar to its narrow, winding arms and the dust threaded through them, thanks to five separate images taken in different wavelengths of light,” noted ESA.

“In fact, the galactic center is bright enough to Hubble that it exhibits diffraction spikes, normally only seen on stars such as HD 101274.”

More about the NGC 3783 galaxy group

The NGC 3783 group is part of the larger Hydra-Centaurus Supercluster, which itself is a massive collection of galaxies and galaxy clusters located primarily in the constellations of Hydra and Centaurus.

The NGC 3783 group consists of several galaxies that are gravitationally bound and interact with each other. These interactions can influence the galaxies’ evolution through mechanisms like tidal forces and merger events, which can trigger star formation, fuel central black holes, and reshape the galaxies’ structures.

Studying groups like the NGC 3783 group helps astronomers understand how galaxies evolve together in a common gravitational environment, offering insights into the dynamics and evolution of structures on cosmic scales.

Image Credit: ESA/Hubble & NASA

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