if stars are formed from molecular clouds

im wondering what caused the ignition or spark for each star to start?
i was reading about star formation and it says Stars form inside relatively dense concentrations of interstellar gas and dust known as molecular clouds. These regions are extremely cold (temperature about 10 to 20K, just above absolute zero). At these temperatures, gases become molecular meaning that atoms bind together.

If the atoms bind together does it make it easier or harder to ignite?

I ask because i thought it was impossible to make ignition at that extreme of a cold.
does anyone know?

a reply to: Belcastro

The work done to compress the gasses in the star formation cloud create the energy that is the heat that causes a great rise in temperature.

The binding causes the temp spike. That's why the inside of the sun is so much hotter than the surface, tons of pressure causing millions of nuclear explosion events in a strange tangle of all sorts of quantum weirdness.

a reply to: Belcastro

Consider if one of them gases turned liquid is say hydrogen, on the outer parts of the liquid state there will be gas as it is on the outside and that is flammable. That is my best guess I don't know this as absolute fact in outer space.

Galaxies are atoms on a much bigger scale. Stars are simply electrons popping in and out of existence. Many of them exist in multiple places at once, so when you look up at the night sky and see billions of stars, what you're actually seeing is multiple instances of the same 112 or so electrons... at least that's my theory anyways.

a reply to: Belcastro

I used to know the 3 stages of stellar evolution and I can't quite remember them
now.

a reply to: Belcastro

I'm pretty sure that as the clouds become larger and generate more gravity the pressure on the elements in the center of the mass becomes greater and greater until eventually fusion occurs.

In a nutshell.

originally posted by: hubrisinxs
a reply to: Belcastro

The work done to compress the gasses in the star formation cloud create the energy that is the heat that causes a great rise in temperature.

What compresses the gas in the first place?

Good old Wikipedia Wikipedia on star formation

originally posted by: misterhistory
Good old Wikipedia Wikipedia on star formation

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Best post ever.

a reply to: hubrisinxs

The work done to compress the gasses in the star formation

What process compress's the gas?

a reply to Brotherman

liquid state there will be gas as it is on the outside and that is flammable

How is a gas flammable in the vacuum of space?

a reply to: Bone75

Yeah I like this...we live in the Truman Show

a reply to: watchitburn

sure that as the clouds become larger and generate more gravity

I didn't know that gravity was "generated" or if we even have any real solutions to what gravity is yet...correct me if I'm wrong

Didn't they discover recently that there are black holes in the middle of most spiral galaxies, bet you that is the 'Engine' that creates stars.

Gravity.
As The Cloud of gases coalesce The central mass increases thereby increasing its gravitational pull.
As the Central Mass pools more gas to itself more pressure is created.
The intense pressures Heat up the gas.
When the pressure Reaches a critical point Atomic fusion occurs And the rest of the gases serve as a ready fuel supply to continue the reaction

originally posted by: TheConstruKctionofLight
a reply to: Bone75

Yeah I like this...we live in the Truman Show

More like Horton Hears a Who.

as it has already been explained.

Stars form as a local density of cold gas begins to exert a tiny gravitational force which further causes more gas and dust to gather.

Depending on the local density, after a few million years, the process runs away and you form a large gassy ball similar to that of a large gas giant, only for the case of a star it will be much higher mass.

Through the process of gravitational collapse the material that was once cold, is undergoing collisions and compression which heats it up. As there is no internal heat source to stop the outer material from falling in, the protostellar core will continue to become dense and hot.

This will reach a critical point at which the density and temperature of the material will reach a point where fusion is sustainable. Once this occurs, object becomes an actual Star. The fusion process at the core maintains the star from further gravitational collapse as energy is radiated outwards from the core.

Depending upon how much mass the star obtained during its younger stages determines how much pressure the core is under, how much material the star can fuse per section and thus how much energy is produced. The knock on affect is then the stellar class.

A star born in a material rich area, with plently of material, will tend to gather a large amount of material and be a bright blue/white star that will burn fast and die young. A star born in a more deprived area will be smaller and redder... but also live longer.

originally posted by: Belcastro
If the atoms bind together does it make it easier or harder to ignite?

The atoms binding together IS the ignition, it's called nuclear fusion.

originally posted by: Belcastro
I ask because i thought it was impossible to make ignition at that extreme of a cold.
does anyone know?

You do need high temperatures and pressures for nuclear fusion as far as we know (which is one reason we are skeptical about so-called "cold fusion"), but the friction of atoms during collapse of a gas cloud provides plenty of heat and gravity results in plenty of pressure for fusion to occur if the mass is large enough, and if the mass isn't large enough, you get something like Jupiter, where the mass is about ten times too low for fusion to occur.

originally posted by: misterhistory
Good old Wikipedia Wikipedia on star formation

It can get complicated according to that but there are some admirable attempts in this thread to simplify the wiki explanation.

originally posted by: TheConstruKctionofLight
How is a gas flammable in the vacuum of space?

It's not, stars don't combust like a flame, they are powered by nuclear fusion.

originally posted by: TheConstruKctionofLight
I didn't know that gravity was "generated" or if we even have any real solutions to what gravity is yet...correct me if I'm wrong

We understand the behavior of gravity on the scale of our solar system which is relevant to star formation, and that's enough to answer many questions about star formation. Newton wrote down equations describing the behavior of gravity centuries ago which are still essentially correct with a few exceptions which require relativity to explain like the precession of Mercury, and he also admitted he didn't know why it followed those equations, just that it did. Now we have more refined equations thanks to Einstein but I think we are still in the same situation Newton described, where we understand the behavior of gravity, but not the exact cause of the behavior.

a reply to: watchitburn

This is how I thought (maybe just from assuming, rather than knowledge) it goes down. Over time, the gravity gathers, speeding up as the gravity increases, eventually enough to fuse atoms (fusion) at the ridiculous pressures. With the right amount of material, etc., it becomes self-sustaining.

For some reason, it's hard for me to keep in mind that the gasses are starting off so cold. I always tend to forget. My mind always wants to think of it as hot clouds of gasses.

originally posted by: dogstar23
For some reason, it's hard for me to keep in mind that the gasses are starting off so cold. I always tend to forget. My mind always wants to think of it as hot clouds of gasses.

There are plenty of hot gas clouds, many of them hotter than the surface of the sun, however that thermal energy tends to prevent their collapse, so as the wiki article cited above explains, if they are too hot that will prevent the collapse:

An interstellar cloud of gas will remain in hydrostatic equilibrium as long as the kinetic energy of the gas pressure is in balance with the potential energy of the internal gravitational force.

"kinetic energy of the gas pressure" is of course related to temperature, and if it's really hot it can expand rather than contract.