|Where does the sun come from?
|Question Date: 1999-06-08|
I'm not sure from your question if you mean where
does the sun come from when it appears each
morning, or where did the sun come from originally
(i.e., how was it "born"). If you are wondering
where it comes from each morning, the sun doesn't
really move. All that is happening is that Earth
is rotating around, and during the night, the part
of the Earth that we are on is facing away from
the sun. When the sun appears to rise in the
morning, all that is happening is that the Earth
has turned so that we can just start to see the
If you are wondering where the sun came
from originally, there was an answer to one of the
last batch of Scienceline questions about how
starts are born. The sun is just a star, and was
born in the same way as other stars, so you can
just look up the answer to that question.
The sun and other stars come from space dust and
gasses.Space is not a total vacuum. It has very
small amounts of gasses and dust in it. But in
some places the dust gets just a little dense and
gravitational attraction takes over and causes it
all to come together very slowly--millions and
billions of years. Eventually the cloud gets
dense enough and big enough that pressure is
exerted on the gasses in the center so that they
heat up--but it isn't a star yet. Much later, the
heat and pressure are so great that nuclear
reactions begin and then you have a star or our
sun. If you want to see places where stars are
forming, check out nebulae.
The sun was formed more than 6 billion years ago
from a cloud of gas and dust that came from the
remnant of a previous star that exploded as a
super-nova. You might look in the Scienceline
archives under the question "how are stars
formed?" in the astronomy section. Historically,
people have had to make other ideas about where
the sun came from each day as it comes over the
horizon, goes across the sky, and sets again.
What sorts of explanations for where the sun comes
from each day do you think people might have made
before they understood astronomy as we do
There are several theories about this -- it is
generally thought that the sun and solar system
coalesced out of diffuse gas in the milky way
about 4.6-4.4 billion years ago, with most of the
mass (99.98%) ending up in the sun. The sun is
known to be a population 2 star -- i.e. its
spectra shows traces of many elements other than
hydrogen and helium so it is almost certainly made
up of gas mixed with debris from earlier stars.
(It is believed that all elements beyond iron are
formed only in such collossal explosions).
Although there are many views about why the gas
collapsed, it is known that the sun is inside of a
supernova blast sphere, formed when a super nova
exploded eons ago. Such explosions can cause local
high density regions within which stars can form.
You can see newly formed stars as bright open
clusers --with the pleiades (the seven sisters)
and the big dipper association as the easiest and
the orion nebula grop as the newest easily
Although 4. 5 billion years seems very
long, astronomers now routinely find galaxies
whose light has been enroute to us for far longer.
Most theories place the formation of the milky
way at least 12 billion years ago -- so there has
been lots of time for the universe to build stars
which died before the sun formed....
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