* Astronomy

Galactic or open star clusters are relatively young swarms of bright stars born together near the plane of our Milky Way Galaxy. Separated by about a degree on the sky, two nice examples are M46 (upper left) 5,400 light-years in the distance and M47 (lower right) only 1,600 light-years away toward the nautical constellation Puppis.


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M46, around 300 million years old, contains a few hundred stars in a region about 30 light-years across. M47, 80 million years old, is a smaller but looser cluster of about 50 stars spanning 10 light-years.
This image also contains an ancient interloper. The small, colourful patch of glowing gas in M46 is actually the planetary nebula NGC 2438 - the final phase in the life of a sun-like star billions of years old. NGC 2438 is estimated to be only 3,000 light-years distant and likely represents a foreground object, only by chance appearing along our line of sight to youthful M46.