Spiral Galaxy Messier 94

This image shows the galaxy Messier 94, which lies in the small northern constellation of the Hunting Dogs, about 16 million light-years away.

Within the bright ring around Messier 94 new stars are forming at a high rate and many young, bright stars are present within it – thanks to this, this feature is called a starburst ring.

The cause of this peculiarly shaped star-forming region is likely a pressure wave going outwards from the galactic centre, compressing the gas and dust in the outer region. The compression of material means the gas starts to collapse into denser clouds. Inside these dense clouds, gravity pulls the gas and dust together until temperature and pressure are high enough for stars to be born.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1542a/

Star-Forming Region LHA 120-N44

This colourful view shows the star-forming region LHA 120-N44 in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way. This picture combines the view in visible light from the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile with images in infrared light and X-rays from orbiting satellite observatories.

At the centre of this very rich region of gas, dust and young stars lies the star cluster NGC 1929. Its massive stars produce intense radiation, expel matter at high speeds as stellar winds, and race through their short but brilliant lives to explode as supernovae. The winds and supernova shock waves have carved out a huge cavity, called a superbubble, in the surrounding gas.

Observations with NASA's Chandra X-ray Observatory (shown here in blue) reveal hot regions created by these winds and shocks, while infrared data from NASA's Spitzer Space Telescope (shown in red) outline where the dust and cooler gas are found. The visible-light view from the MPG/ESO 2.2-metre telescope (in yellow) completes the picture and shows the hot young stars themselves as well as the glowing clouds of gas and dust that surround them.

Combining these different views of this dramatic region has allowed astronomers to solve a mystery: why are N44, and similar superbubbles, giving off such strong X-rays? The answer seems to be that there are two extra sources of bright X-ray emission: supernova shock waves striking the walls of the cavities, and hot material evaporating from the cavity walls. This X-ray emission from the edge of the superbubble shows up clearly in the picture.

Image Credit: Optical: ESO, X-ray: NASA/CXC/U.Mich./S.Oey, IR: NASA/JPL
Explanation from: https://www.eso.org/public/images/potw1236a/

Star Cluster Pismis 24

Home to some of the largest stars ever discovered, the open stellar cluster Pismis 24 blazes from the core of NGC 6357, a nebula in the constellation of Scorpius (the Scorpion). Several stars in the clusters weigh in at over 100 times the mass of the Sun, making them real monster stars. The strange shapes taken by the clouds are a result of the huge amount of blazing radiation emitted by these massive, hot stars. The gas and dust of the nebula hide huge baby stars in the nebula from telescopes observing in visible light, as well as adding to the hazy appearance of the image.

This image combines observations performed through three different filters in visible light (B, V, R) with the 1.5-metre Danish telescope at the ESO La Silla Observatory in Chile.

Image Credit: ESO/IDA/Danish 1.5 m/ R. Gendler, U.G. Jørgensen, J. Skottfelt, K. Harpsøe
Explanation from: https://www.eso.org/public/images/potw1015a/