Hubble captures a collection of spiral galaxies  -

Hubble captures a collection of spiral galaxies 

Today’s Image of the Day from the European Space Agency features a collection of spiral galaxies captured by the Hubble Space Telescope.

“This image is a really interesting example of how challenging it can be to tell whether two galaxies are actually close together, or just seem to be from our perspective here on Earth,” says ESA.

“A quick glance at this image would likely lead you to think that NGC 1356, LEDA 467699 and LEDA 95415 were all close companions, whilst IC 1947 was more remote. However, we have to remember that two-dimensional images such as this one only give an indication of angular separation: that is, how objects are spread across the sphere of the night sky. What they cannot represent is the distance objects are from Earth.” 

“For instance, whilst NGC 1356 and LEDA 95415 appear to be so close that they must surely be interacting, the former is about 550 million light-years from Earth and the latter is roughly 840 million light-years away, so there is nearly a whopping 300 million light-year separation between them. That also means that LEDA 95415 is likely nowhere near as much smaller than NGC 1356 as it appears to be.”

On the other hand, notes ESA, NGC 1356 and IC 1947 seem to be separated by a relative gulf in this image, they are actually much closer neighbors in space compared to NGC 1356 and LEDA 95415.

Spiral galaxies are among the most visually striking objects in the universe. They are characterized by their flat, disk-like structure with spiral arms winding outward from the center. These galaxies are not just beautiful but also fascinating for several reasons.

The central region of a spiral galaxy typically contains a bulge composed of older stars. This contrasts with the spiral arms, which are often sites of active star formation, marked by the presence of younger, hotter stars. These arms give spiral galaxies their distinctive appearance and are thought to be formed due to density waves that compress and expand the gas and dust in the disk.

Spiral galaxies contain significant amounts of interstellar medium, the gas and dust that fill the space between stars. This medium is crucial for star formation, as new stars are born from the gravitational collapse of gas clouds.

The rotation of spiral galaxies is another intriguing aspect. The stars and other materials in these galaxies rotate around the center, but not at the same speed. This differential rotation contributes to the winding of the spiral arms.

Many spiral galaxies, including the Milky Way, have a supermassive black hole at their center. The presence of these black holes plays a significant role in the dynamics and evolution of the galaxies.

image Credit: European Space Agency

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