about nebulae?

Question

how are they created and what's their life span? which is the closest nebula to the solar system? Can a nebula be seen with the naked eye in a fairly light polluted region (an urban city)?

Answer 1

Nebulae are just large clouds of gas and dust. These regions either mark the birth or death of stars. Star birthing regions such as the Eagle and Orion nebulae are huge clouds of gas and dust that have begun to collapse under their own gravity. These overdense regions have a tendancey to form from gas and dust piling up in the spiral arms of our galaxy.

A nebulae can also be formed from the gas expelled from the death of a low mass star, forming a planetary nebulae such as the Ring nebula or the Owl nebula. Note the term "planetary" nebula was given to these objects since they were green in color, much like the (at the time) recently discovered planet Uranus. They are vast clouds of gas and dust, and are not related to planets.

Lastly a high mass star's supernova can also leave a nebula, the crab nebula is the remnant of a high mass star exploding in the 11th century.

The Helix Nebula at around 400 light years is the nearest planetary nebula, The Orion Nebula is one of the closest star-forming nebulae at about 1500 light years.

What can you see with the naked eye? The Orion Nebula apears as the middle "star" in Orion's "sword". You will need the aid of binoculars or a telescope to see any nebulosity though.

Historically, until we figured out what they were spiral galaxies were called "spiral nebulae." You can see the Andromeda Galaxy with the naked eye, but you need very dark skys to do it.

Answer 2

Nebula are formed by dying stars blowing off their outer layers or the ionization caused by new stars forming in a cloud of gas. Since they're clouds of gas and plasma, they'll usually last until something happens to scatter their material. The one called MyCn18 is about 8000 light years away. Usually they aren't visible from light-polluted areas.

Answer 3

In a clear dark sky, away from city lights, you can see the Orion nebula without a telescope.

Answer 4

because of the fact it exchange right into a supernova, now that's a supernova remnant which leaves at the back of a cloud like shape it quite is what a nebula is. yet another component to the "remnant" is the pulsar, yet that's no longer cloud-like, yet confusing to work out even with large telescopes.