Main content
Course: Big History Project > Unit 3
Lesson 1: How Were Stars Formed? | 3.0- ACTIVITY: The Life of a Star
- ACTIVITY: Infographic —Life Cycles of the Stars
- WATCH: Unit 3 Overview - Stars and Elements
- ACTIVITY: Unit 3 Vocab Tracking
- WATCH: How Were Stars Formed?
- ACTIVITY: Threshold Card — Threshold 2 Stars Light Up
- WATCH: Threshold 2 — Stars Light Up
- WATCH: Elements - A Brief Big History (H2)
- ACTIVITY: This Threshold Today
- ACTIVITY: DQ Notebook 3.0
- READ: Gallery — Structure in the Universe
- READ: Gallery — Stars
- Quiz: How Were Stars Formed?
© 2024 Khan AcademyTerms of usePrivacy PolicyCookie Notice
WATCH: Threshold 2 — Stars Light Up
The early Universe was dark and cold – until a few atoms of hydrogen and helium got together, and a star was born. Explore the birth of stars from the aftermath of the Big Bang and discover how tiny variations in matter density, coupled with gravity, led to the formation of stars. Learn how protons and electrons fused together, creating energy that lit up the universe and formed galaxies. Created by Big History Project.
Want to join the conversation?
how many galaxies are there?(8 votes)
"According to the best estimates of astronomers there are at least one hundred billion galaxies in the observable universe. They've counted the galaxies in a particular region, and multiplied this up to estimate the number for the whole universe." http://www.physics.org/facts/sand-galaxies.asp(5 votes)
If the universe is expanding, can we estimate which direction it's expanding in? And if so, can we find out where it's expanding away from. And would that be where the big bang originated?(6 votes)
Brad sounds like you are asking where the centre of the known Universe is. Interestingly, there appears to be no centre to the Universe since the Big Bang cannot be seen as an ordinary explosion.
"It was an explosion of space, not an explosion in space. According to the standard models there was no space and time before the Big Bang. There was not even a "before" to speak of. So, the Big Bang was very different from any explosion we are accustomed to and it does not need to have a central point."
http://math.ucr.edu/home/baez/physics/Relativity/GR/centre.html(3 votes)
Why does the extreme heat of nuclear fission stop a star from collapsing?(4 votes)
Because it emits an outward pressure against the inward pressure caused by gravity.(6 votes)
Can someone check if i am correct.
To re-cap, matter (electrons, protons, neutrons), energy (gravity, nuclear forces, electro-magnetisim), time and space were created during the big bang.
The big bang refers to the creation and expansion of the universe. High heat caused a plasma to exist, a mush full of charged particles (electrons/protons). 380,000 years after the big bang the temperature fell enough to allow the electrons and protons to combine into atoms, mainly of Hydrogen and Helium, forming clouds of gas/atoms.
Clouds of atoms spread throughout the universe were not of the same density. Denser clouds were acted upon gravity and drawn together. In these dense regions of the universe, temperature and pressure began to rise, which led to atoms being split and the re-creation of plasma.
Once the heat in the plasma centre of these dense gas clouds reached above 10 billion degrees, protons began to fuse and release energy. This marked the birth of the star which filled the dark universe, lighting it with energy.
Stars continued to emit energy until all the protons within the dense clouds are used up.(4 votes)- how long does it take for a star to form?(3 votes)
It takes millions of years for a star to form, which is actually pretty quick when talking about space.(1 vote)
Where Can we see the expanding universe?(2 votes)- we can't see it with naked eye until we can't see anything at all but we can see it from satellites and probes(2 votes)
Video transcript
NARRATOR:
Right after the Big Bang, our young Universe was what scientists
call a plasma. This was basically
an incredibly hot mush of charged particles without
much structural complexity. About 380,000 years later,
things began to change. By then, temperatures
had fallen low enough for protons, which
have positive charges, to link up with electrons,
which have negative charges. And together, they formed
electrically neutral atoms, very simple ones like
hydrogen, some helium, and a few slightly heavier atoms
thrown in for good measure. The Universe now contained
vast clouds of these atoms. Add gravity and now
you have the ingredients for our second threshold,
the formation of stars. Here's what happened next. Wherever there was
slightly more matter, gravity is more powerful. So, tiny variations
in the density of matter became the first
Goldilocks condition for this second threshold. Gravity packed
slightly denser regions ever closer together,
squashing them so tightly that they began to heat up. This growing pressure and heat created our second
Goldilocks condition. Eventually,
the clouds got so hot, the protons and electrons
split apart once more, recreating a plasma. And when temperatures in
these hot spots got to about 10 million degrees Celsius,
protons began to fuse together and part of them turned into
energy as they did so. This huge release of heat from the center
of each cloud of matter stopped the cloud from
collapsing any further. And this is how the
first stars lit up. Soon, the Universe
had billions of hot spots pouring energy into
the cold of deep space. Each star would
continue releasing energy into space for millions
or even billions of years until it had
no more protons to fuse. And as these stars
formed, so did galaxies, each containing
billions of stars. Galaxies in turn grouped together
into huge clusters and chains of galaxies, the largest structures
in the Universe. Suddenly, the Universe seemed
to have a lot more variety and a lot more structure. Now, what new
things could happen in a Universe filled with stars?