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 emissio ...

located in Cassiopeia. 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 in the constellation Cassiopeia. Once believed to be a member of the Local Group of galaxies, it is now known to belong to a separate group, the IC 342/Maffei Group. It was named after Paolo Maffei, who ...

and

Maffei 2 Maffei 2 is an intermediate spiral galaxy about 10 million light-years away in the constellation Cassiopeia. Maffei 2 and Maffei 1 were both discovered by Paolo Maffei in 1968 from their infrared emission. Maffei 2 lies in the Zone of Avoidan ...

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. 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 and its satellites form ...

, 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 brig ...

. This complex is the eastern neighbor of IC1805 (

Heart Nebula The Heart Nebula (also known as the Running dog nebula, IC 1805, Sharpless 2-190) is an emission nebula, 7500 light years away from Earth and located in the Perseus Arm of the Galaxy in the constellation Cassiopeia. It was discovered by William ...

) and the two are often mentioned together as the "Heart and Soul". Image: W5 cropped.jpg, Generations of stars can be seen in this infrared portrait from NASA's Spitzer Space Telescope. 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 those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

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, and covering a surface. Mosaics are often used as floor and wall decoration, and were particularly pop ...

from NASA's WISE telescope. Image:IC1848_JeffJohnson.jpg, IC 1848 area imaged using amateur telescope (Credit: Jeff Johnson).

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, 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