Seemingly adrift in a cosmic sea of stars and gas, this delicate, floating apparition is cataloged as NGC 7635: the Bubble Nebula. In this wide-angle view, the Bubble nebula lies at the center of a larger complex of shocked glowing gas about 11,000 light-years distant in the fair constellation Cassiopeia. NGC 7635 really is an interstellar bubble, blown by winds from the brightest star visible within the bubble's boundary. The bubble's expansion is constrained by the surrounding material. About 10 light-years in diameter, if the Bubble nebula were centered on the Sun, the Sun's nearest stellar neighbor, Alpha Centauri, would also be enclosed. (Text adapted from Astronomy Picture of the Day)

This image has been chosen as NASA Astronomy Picture of the Day for April 28, 2006

Remarkable features Click the image to view and interact with the hi-res image. 2 Cas is star with a visual magnitude of 5.70. Click here for further info. 4 Cas is a bright red star, with a visual magnitude of 4.98. Click here for further info. M52 is a large and rich open stars cluster in Cassiopeia. It contain about 100 stars in about 16 arcminutes. Its magnitude is 8.2 and lie at 4,800 light years from the Sun. NGC7635 is the Bubble nebula (see description above). NGC7510 is an open stars cluster in Cepheus, about 7 arcminutes large, containing about 60 stars. Its magnitude is 9.3 and lie at about 10,000 light years. NGC7538 is a nebula in Cepheus, 10 acrminutes large. Sh2-161 is a large doubly ionized hydrogen (HII) nebula. Its size is about 90x60 arcminutes. Some nice dark nebulae are visible in front of Sh2-161, like LDN1229, LDN1233 and LDN1234. Sh2-157 is a tiny HII nebula, large 3x3 arcminutes. LBN536 is a large HII nebula, its size is about 80x40 arcminutes.   Find Chart The position of the nebular complex around the Bubble Nebula (in the red circle) among Cepheus and Cassiopeia. Image from Cartes du Ciel.

In order to produce the color image seen here, I worked with data coming from 2 different photographic plates taken at Palomar Observatory between 1991 and 1997. The original file is 9,896x12,468 pixels with a resolution of about 1 arcsec per pixel. The image show an area of sky large 2.7° x 3.5° (for comparison, the full-Moon is about 0.5° in diameter).
A larger field-of-view image is also available, its size is 11,766x13,414. It show an area of sky large 3.3° x 3.7°.
Copyright: Davide De Martin (http://www.skyfactory.org).

Other images of the same celestial field found online

• http://antwrp.gsfc.nasa.gov/apod/ap040328.html by Brian Lula;
• http://www.aao.gov.au/images/captions/int010.html by David Malin;
• http://www.icefogobservatory.com/Astro_image_pages/Planetary_nebulae/bubble-M52-fullpage.html by Peter Finnoff.

This image is a composite from black and white images taken with the Palomar Observatory's 48-inch (1.2-meter) Samuel Oschin Telescope as a part of the second National Geographic Palomar Observatory Sky Survey (POSS II). The images were recorded on two type of glass photographic plates - one sensitive to red light and the other to blue light and later they were digitized. Credit: Caltech, Palomar Observatory, Digitized Sky Survey.