Tiny galaxy with a bright nebula

Dwarf galaxy NGC 2366

The dwarf galaxy NGC 2366 might be small and dim, but it is home to a surprisingly bright, star-forming nebula—the blue patch in the top-right corner—and close enough so that its individual stars can be made out.

THE STARRY SMOG stretching across this image obtained by the Hubble Space Telescope is the central part of the dwarf galaxy known as NGC 2366. The most obvious feature in this galaxy is a large nebula visible in the upper-right part of the image, an object known as NGC 2363.

A nearby yellowish swirl is not in fact part of the nebula. It is a spiral galaxy much further away, whose light is shining right through NGC 2366. This is possible because galaxies are not solid objects. Galaxies are overwhelmingly made up of the empty space between stars.

NGC 2366 and NGC 2363 are located about 10 million light-years away. As a dwarf galaxy, NGC 2366’s size is in the same ballpark as the two main satellite galaxies of our Milky Way, named the Large and Small Magellanic Clouds. Like the Magellanic Clouds, NGC 2366’s lack of well-defined structure leads astronomers to further classify it as an irregular galaxy.

Although NGC 2366 might be small by the standards of galaxies, many of its stars are not, and the galaxy is home to numerous gigantic blue stars. The blue dots scattered throughout the galaxy speak to the burst of star formation that the galaxy has undergone in recent cosmic time. A new generation of these stellar titans has lit up the nebula NGC 2363.

In gas-rich star-forming regions, the ultraviolet radiation from young, big, blue stars excites the hydrogen gas, making it glow. NGC 2363, as well as other, smaller patches seen throughout Hubble’s image, are the latest birth sites for stellar giants.

Imaged through green and infrared filters, these nebulae take on a blue-ish tinge in this image, though their actual colour is a shade of red.

Adapted from information issued by NASA / ESA.

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