A small portion of the rough-and-tumble neighborhood of swirling dust and gas near one of the most massive and eruptive stars in our galaxy is seen in this NASA/ESA Hubble Space Telescope image. This close-up view shows only a three light-year-wide portion of the entire Carina Nebula, which has a diameter of over 200 light-years. Located 8,000 light-years from Earth, the nebula can be seen in the southern sky with the naked eye. Credit: NASA/ESA, Hubble
IC 63 — nicknamed the Ghost Nebula — is about 550 light-years from Earth. The nebula is classified as both a reflection nebula — as it is reflecting the light of a nearby star — and as an emission nebula — as it releases hydrogen-alpha radiation. Both effects are caused by the gigantic star Gamma Cassiopeiae. The radiation of this star is also slowly causing the nebula to dissipate.
The cosmic brush of star formation composed this alluring mix of dust and dark nebulae. Cataloged as Sh2-239 and LDN 1551, the region lies near the southern end of the Taurus molecular cloud complex some 450 light-years distant.
Image Credit: Adam Block, Mt. Lemmon SkyCenter, University of Arizona
What are nebulas?. And why nebulas are big as galaxies.
Basically, a nebula a huge cloud of gas and dust. Some nebulae are the rest of the death of a giant star, like a supernova. Other nebulae are where new stars are forming. (more)
The nebulae are divided into some types:
Emission nebulae are gas clouds with high temperature. The atoms in the cloud are energized by ultraviolet light from a nearby star and emit radiation when they decay to lower energy states. Emission nebulae are usually red, because of hydrogen, the most common gas in the Universe and commonly emitting red light.
Reflection nebulae are dust clouds that simply reflect the light of a star or nearby stars. Reflection nebulae are usually blue because the blue light is spread more easily. Emission and reflection nebulae are usually seen together and are sometimes called diffuse nebulae.
There are also dark nebulae, they are clouds of gas and dust that almost completely prevent the light from passing through them, are identified by the contrast with the sky around them, which is always more starry or bright. They may be associated with star formation regions.
Planetary nebulae were named after William Herschel because when they first appeared to the telescope, they resembled a planet, later it was discovered that they were caused by ejected material from a central star. This material is illuminated by the central star and shines, and an emission spectrum can be observed. The central star usually ends up as a white dwarf.
Remnant of supernova
Remnant of supernova is a gas envelope, composed of the remains of a star that was destroyed by a violent explosion, supernova, marking the death of this.