Westerhout 5 ( Sharpless 2-199, LBN 667, Soul Nebula) is an

emission nebula An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star. Among the several different types of emission n ...

located in

Cassiopeia Cassiopeia or Cassiopea may refer to: Greek mythology * Cassiopeia (mother of Andromeda), queen of Aethiopia and mother of Andromeda * Cassiopeia (wife of Phoenix), wife of Phoenix, king of Phoenicia * Cassiopeia, wife of Epaphus, king of Egy ...

. Several small open clusters are embedded in the nebula: CR 34, 632, and 634 (in the head) and IC 1848 (in the body). The object is more commonly called by the cluster designation IC 1848. Small emission nebula IC 1871 is present just left of the top of the head, and small emission nebulae 670 and 669 are just below the lower back area. The galaxies

Maffei 1 Maffei 1 is a massive elliptical galaxy near the constellation borders between Perseus and Cassiopeia, located 9.8 million light years away. Once believed to be a member of the Local Group of galaxies, it is now known to belong to a separate grou ...

and

Maffei 2 Maffei 2 is an intermediate spiral galaxy about 1 E23 m, 10 million light-years away in the constellation Cassiopeia (constellation), Cassiopeia. Maffei 2 and Maffei 1 were both discovered by Paolo Maffei in 1968 from their infrared emission. M ...

are both nearby the nebula, although light extinction from the Milky Way makes them very hard to see. Once thought to be part of the

Local Group The Local Group is the galaxy group that includes the Milky Way, where Earth is located. It has a total diameter of roughly , and a total mass of the order of . It consists of two collections of galaxies in a " dumbbell" shape; the Milky Way ...

, they are now known to belong to their own group- the

IC 342/Maffei Group The IC 342/Maffei Group (also known as the IC 342 Group or the Maffei 1 Group) corresponds to one or two galaxy groups close to the Local Group. The member galaxies are mostly concentrated around either IC 342 or Maffei 1, which would be the br ...

. This complex is the eastern neighbor of IC1805 (

Heart Nebula The Heart Nebula (also known as the Running Dog Nebula, Sharpless 2-190) is an emission nebula, away from Earth and located in the Perseus Arm of the Galaxy in the constellation Cassiopeia. It was discovered by William Herschel on 3 November 178 ...

) and the two are often mentioned together as the "Heart and Soul". Image:Heart and Soul nebulae.jpg, The

and Westerhout 5 are seen in this

infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

mosaic A mosaic () is a pattern or image made of small regular or irregular pieces of colored stone, glass or ceramic, held in place by plaster/Mortar (masonry), mortar, and covering a surface. Mosaics are often used as floor and wall decoration, and ...

from NASA's WISE telescope.

Star formation

W5, a radio source within the nebula, spans an area of sky equivalent to four full moons and is about 6,500 light-years away in the constellation Cassiopeia. Like other massive star-forming regions, such as Orion and Carina, W5 contains large cavities that were carved out by radiation and winds from the region's most massive stars. According to the theory of

triggered star formation Star formation is the process by which dense regions within molecular clouds in interstellar space—sometimes referred to as "stellar nurseries" or "star-forming regions"— collapse and form stars. As a branch of astronomy, star formation inclu ...

, the carving out of these cavities pushes gas together, causing it to ignite into successive generations of new stars. The image in the gallery above contains some of the best evidence yet for the triggered star formation theory. Scientists analyzing the photo have been able to show that the ages of the stars become progressively and systematically younger with distance from the center of the cavities.

References

{{Cassiopeia (constellation) H II regions Astronomical radio sources Sharpless objects Articles containing video clips Cassiopeia (constellation) Emission nebulae IC objects Star-forming regions