Astronomy Picture of the Day—20181229

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2018December 29

NGC6357: The Lobster Nebula

ImageCredit: Dean Carr

Explanation:Why is the Lobster Nebula forming some of the most massive stars known? No oneis yet sure. Cataloged as NGC 6357, the Lobster Nebula houses the open starcluster Pismis 24 near its center -- a home to unusually bright and massivestars. The overall blue glow near the inner star forming region results fromthe emission of ionized hydrogen gas. The surrounding nebula, featured here,holds a complex tapestry of gas, dark dust, stars still forming, and newly bornstars. The intricate patterns are caused by complex interactions betweeninterstellar winds, radiation pressures, magnetic fields, and gravity. NGC 6357spans about 400 light years and lies about 8,000 light years away toward theconstellation of the Scorpion.