AstronomyPicture of the Day—20181116

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.

2018November 16

TheCave Nebula in Hydrogen, Oxygen, and Sulfur

ImageCredit & Copyright: Chuck Ayoub

Explanation:What's inside this cosmic cave? A stellar nursery 10 light-years deep. Thefeatured skyscape is dominated by dusty Sh2-155, the Cave Nebula. In thetelescopic image, data taken through a narrowband filters tracks the nebularglow of hydrogen, oxygen, and sulfur, colors that together form the HubblePalette. About 2,400 light-years away, the scene lies along the plane of ourMilky Way Galaxy toward the royal northern constellation of Cepheus.Astronomical explorations of the region reveal that it has formed at theboundary of the massive Cepheus B molecular cloud and the hot, young stars ofthe Cepheus OB 3 association. The bright rim of ionized hydrogen gas isenergized by radiation from the hot stars, dominated by the bright star just tothe left of the cave entrance. Radiation driven ionization fronts are likelytriggering collapsing cores and new star formation within.