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Recycling Cassiopeia A
Massive stars in our Milky Way Galaxy live spectacular lives. Collapsing from vast cosmic clouds, their nuclear furnaces ignite and create heavy elements in their cores. After a few million years, the enriched material is blasted back into interstellar space where star formation can begin anew. The expanding debris cloud known as Cassiopeia A is an example of this final phase of the stellar life cycle.

Light from the explosion which created this supernova remnant would have been first seen in planet Earth's sky about 350 years ago, although it took that light about 11,000 years to reach us. This false-color Chandra X-ray Observatory image shows the still hot filaments and knots in the Cassiopeia A remnant.

High-energy emission from specific elements has been color coded, silicon in red, sulfur in yellow, calcium in green and iron in purple, to help astronomers explore the recycling of our galaxy's star stuff - Still expanding, the blast wave is seen as the blue outer ring. The sharp X-ray image, spans about 30 light-years at the estimated distance of Cassiopeia A. The bright speck near the center is a neutron star, the incredibly dense, collapsed remains of the massive stellar core.

Image & info via APOD
https://apod.nasa.gov/apod/astropix.html

Image Credit: NASA, CXC, SAO

#nasa #space #science #stars #Cassiopeia #exploration
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Sharpless 132 Nebula

In this image, taken by +Nicolas Kizilian using a William Optics Zenithstar 66 Telescope and a Moravian G2-8300 camera, you can see Sharpless 132 (Sh2-132, LBN 473) , an HII region type emission nebula in the constellation of Cepheus (https://goo.gl/h8tIIA), about 10,400 light-years away from Earth.

The nebula is ionized by a bunch of hot and massive stars with strong ultraviolet radiation, most notably the two Wolf-Rayet stars HD 211564 (https://goo.gl/Rxk8p3) and HD 211853 (https://goo.gl/JadPa2).

The bubble-like structure you can see is most likely caused by stellar winds (https://goo.gl/Z9Sotn) of massive stars.

Visible at the very right side center of the image is the small open cluster (https://goo.gl/fM4XdP) Berkeley 94. In the bottom left you can see the open cluster NGC 7235.

In the top right you can see a small red ring-like feature called Abell 79, most likely a planetary nebula.

What is an emission nebula?

An emission nebula is a cloud of ionized gas (often by ultraviolet radiation from nearby stars) emitting light of various colors, in case of HII mostly reddish-pink (if viewed in natural colors). More information here:
https://en.wikipedia.org/wiki/Emission_nebula
https://en.wikipedia.org/wiki/H_II_region

What is a Wolf-Rayet star?

Wolf-Rayet stars are massive stars that have extremely high surface temperatures of 30,000 K to around 200,000 K. They are also very luminous, some of them several million times more luminous than our Sun, although much of their radiation output is in the ultraviolet part (https://goo.gl/6sMI2) of the spectrum and not the visible part. They blast strong winds of particles out into space while burning up their fuel, lasting only a few hundred thousand years, a short life for a star. More information here:
https://en.wikipedia.org/wiki/Wolf%E2%80%93Rayet_star

What is a planetary nebula?

A planetary nebula is an emission nebula (https://goo.gl/QtI28t), it is basically a shell of glowing ionized gas ejected from old red giant stars and driven by the ultraviolet radiation of the resulting young and hot white dwarf (https://goo.gl/HGYVfx). They are short-lived objects, lasting a few tens o
f thousands of years until the white dwarf has cooled down so much that its not putting out enough ultraviolet radiation anymore and the gas no longer gets ionized. More here:
https://en.wikipedia.org/wiki/Planetary_nebula
https://en.wikipedia.org/wiki/Red_giant

Read more about the different types of nebulae here in this article I wrote for PhotographingSpace:
https://photographingspace.com/what-are-nebulae/

And in case you want to know more about colors in astrophotography, take a look here:
https://photographingspace.com/ap-color/

Image credit: Sharpless 132 +Nicolas Kizilian https://goo.gl/XByRWx Used with permission

If you like this image, you can find Nicolas here on G+ (+Nicolas Kizilian), on Twitter (https://twitter.com/NKizilian) and on Facebook (https://www.facebook.com/NicolasKizilian) and see more of his work here on his website: http://www.astropixels.fr

Thank you for your interest in this Astronomy/Astrophysics collection. Maybe add me on Google+ (+Pierre Markuse) and Twitter (https://twitter.com/Pierre_Markuse) or have a look at the Space/Space Technology collection here: https://goo.gl/5KP0wx

#science #astronomy #astrophotograpy #emissionnebula #space #photography #hiiregion #sharpless132 #sh2132 #wolfrayetstar #abell79 #ngc7235 #opencluster
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Few astronomical sights excite the imagination like the nearby stellar nursery known as the Orion Nebula. The Nebula's glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud. Many of the filamentary structures visible in the featured image are actually shock waves - fronts where fast moving material encounters slow moving gas. The Orion Nebula spans about 40 light years and is located about 1500 light years away in the same spiral arm of our Galaxy as the Sun. The Great Nebula in Orion can be found with the unaided eye just below and to the left of the easily identifiable belt of three stars in the popular constellation Orion. The featured image, taken last month, shows a two-hour exposure of the nebula in three colors. The whole Orion Nebula cloud complex, which includes the Horsehead Nebula, will slowly disperse over the next 100,000 years.

M42: The Great Orion Nebula
Image Credit & Copyright: Francesco Battistella
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2017/12/20
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