NGC 1491 is an emission nebula. Emission Nebulae are primarily composed of ionized H II. The nebulae are usually the home of new-born stars, and it is these stars that cause the nebulae. Emission nebulae are usually found near new stars because it takes a lot of heat and energy to ionize the hydrogen, heat and energy that only young stars have. Temperature in an emission nebula can range from 7,000 K to 20,000 K. Generally, emission nebulae have a red glow due to the de-ionizing of hydrogen. The density of most emission nebulae is low.
NGC 1491 is in the constellation Perseus. It lies about 10,700 light-years away from earth and is about 9 light years across; in comparison to most emission nebulae, NGC 1491 is relatively small. NGC 1491 has a dark spot right in the middle of it; darks spots are formed when dust clouds block the light. The brightest spot of the nebula is on the right side of the dark spot; this indicates that the nebula is more dense at that spot, has less dust blocking the light or a combination of the two.
"Emission Nebula." Redorbit. N.p., 19 Oct. 2004. Web. 22 Nov. 2011. <http://www.redorbit.com/education/reference_library/space_1/universe/2574674/emission_nebula/index.html>
Lightner, Samuel. "Emission Nebulae." FusEdWeb. N.p., n.d. Web. 22 Nov. 2011. <http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/Nebula/Emission.html>.
"NGC 1491." Wide-Field Infrared Survey Explorer. N.p., 4 May 2011. Web. 22 Nov. 2011. <http://wise.ssl.berkeley.edu/gallery_NGC1491.html>.
|Right Ascension (J2000)||04:03:14|
|Filters used||B (Blue), C (Clear), R (Red), V (Green)|
|Exposure time per filter||B, V, R and C (60s x 5)|