M46 with NGC2438

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When you point your telescope to this part of the sky, you see a Open Cluster known as M46. Open Clusters are a group of stars that were made about the same time from the same emission nebula. You will notice almost same color for these stars, as their age and composition is almost the same having been born from the same cloud. In this case, almost all these stars are blue, denoting that they are hot stars in their youth. Sun on the other hand is white, a combination of red, green & blue. This cluster is about 4900 light years away and has about 500 stars (some of which outside this field of view), roughly with average mass being equal to our Sun. Scientists think that this cluster came up around 250 million years back (relatively recent as Sun was born about 4.5 billion years back).

If you look closely, you will a small round object (which I have put it on top-right as an inset). The object is planetary nebula NGC2438. Planetary nebulae are remains of a dead stars – like the mess left after a little explosion. At the end of a normal-sized star’s life, in the red giant phase, the outside layers of a star are ejected. Because the outside is gone, the star shines brightly and is very hot. The ultraviolet radiation given off by the center of the star ionizes the gas and plasma that was thrown out from the star. This is what causes a planetary nebula to look like it does.

NGC 2438 appears to lie within the cluster near its northern edge, but it is most likely unrelated since it does not share the cluster’s radial velocity – it means that they are not moving the same way, therefore unconnected by gravity. It is an example of a superimposed pair, which happen to lie on the same line of sight from our location.

About 3,000 light-years distant it lies within the boundaries of the nautical constellation Puppis.

I took this image over 3.4 hours. (Luminance 28 images of 5 minutes and 3 color sets of 3 minutes each for 7 images).

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