“Nebulae” collection
Sadr Region
Pretty dark nebulae in front of hydrogen clouds
The red/orange parts of the image are made up of hydrogen and sulphur, the bluish parts are oxygen. The black parts are dark nebulae or absorption nebulae which block the light of the stars behind them. You can see such dark clouds with the naked eye as dark patches against the brighter background of the Milky Way!
Crescent Nebula
NGC 6888 / Caldwell 27 / Sharpless 105 / WR 136
The star you see in the middle of the nebula is called WR136. Somewhere around 300,000 years ago it ran out of fuel and became a red giant. It threw off some material, gas and dust, into space. Since then its solar wind sends shockwaves through that cloud, forming it, heating it up, causing it to glow and emit all sorts of radiation.
Veil Nebula
NGC 6960 / Caldwell 34
The Veil Nebula is the remnant of an exploded star. It is massive; when viewed from Earth it is over 30 times the area of the full Moon. The actual diamater is about 65 light-years and our distance from it is around 2,500 light-years. Even the finest filaments are huge; their thickness is about the distance from the Sun to Pluto! The supernova explosion (that this nebula is the remnant of) happened less than 20,000 years ago.
Ring Nebula
M57 / NGC 6720
Dora’s favorite planetary nebula imaged on the night of the summer solstice. In the middle is a (now) white dwarf. It is actually 200x as bright as the Sun, but is 2,400 light-years away. This nebula is tiny (when viewed from Earth), just 1.5 by 1 arcminutes. It only started the expansion 200-600 years ago!
North America & Pelican nebulae
NGC 7000 / Caldwell 2 & IC 5070 & IC 5067
The North America Nebula is huge; when viewed from Earth it is over 10 times the area of the full Moon. The actual diamater is about 90 light-years and our distance from it is around 2,590 light-years.
Horsehead Nebula
Barnard 33
Horsehead Nebula in Orion, 1,375 light-years from Earth. The brightest star in field of view is the triple star Alnitak (ζ Orionis). That is, three stars orbiting one another in a complicated dance. One of the companions is even visible in the picture.