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By Jaedyn Waggoner. Block C. Mr. Horton. Science 9
Happened approximately 13.5 billion years ago
The Big Bang was caused by the density of the compressed galaxies. It was in a very
high density state, then it expanded. After the beginning expansion, it cool to let
subatomic particles and later on, simple atoms to form.
There are 3 types of universes, open, flat, and closed.
Open universes expand forever.
Flat universes expand forever, but the rate that it expanded at would eventually slow
down to zero after an infinite amount of time.
Closed universes eventually stop expanding and recollapse on itself, potentially causing
another big bang.
In all three types of universes, the expansion does slow eventually, and the cause of them
slowing is of course, gravity.
What is an astronomer?
- an astronomer is a scientist who studies celestial bodies i.e. black holes, planets,
stars, asteroids, comets, nebulae, and galaxies (space).
Astronomers use telescopes and radio signal type technologies to better understand our
universe and how it works. It is important to know about our universe because if we didn’t,
we wouldn’t know the precautions that come with meteors and asteroids and such.
Galaxies are thought to be formed as the result of little quantum fluctuations from the aftermath
of the Big Bang. They gain mass by clustering and merging with one another.
There are 4 types of galaxies, Elliptical, Spiral, Lenticular, and irregular.
Elliptical galaxies don’t have very much gas and dust. Because gas and dust are found in
clouds that stars are born from, there are not many young stars in elliptical galaxies. They
contain mostly old, red stars.
Spiral galaxies have two very distinct regions. The middle – the disk of the galaxy – contains
the spiral arms. The disk is where many stars are born, and it has a lot of gas and dust. Most of
the stars are young, blue Population I stars. Type C spiral galaxies have the most amount of
gas and dust.
Lenticular galaxies have central bulges and disks, but lack spiral arms. It’s quite easy to
mistake a lenticular galaxy for an elliptical galaxy, but only if the disk is faint.
Galaxies that don’t fit into the spiral or elliptical galaxies are considered irregular galaxies. They
have a wide variety of shape and characteristics, and are frequently the result of when two or
more galaxies collide.
Edwin Hubble was an American Astronomer who helped in creating the theory about
extragalactic astronomy. He also provided evidence that many things back then called
Nebulae were actually galaxies past the Milky Way.
This theory had been previously discovered by the Belgian Priest and Astronomer,
Georges Lemaître, but because it was written down and recorded in an illegible notebook,
the theory stays called “Hubble’s Law”.
The Hubble’s Law is the observation that objects seen and observed far out in space are
often found to have a Doppler Effect that could be considered relative velocity far from
Earth and that this Doppler-Effect-measured velocity of certain galaxies moving away
from Earth is proportional to their distance from Earth for galaxies that are up to a
hundred or so megaparsecs away. The Hubble Law is the first observational basis for the
expansion of space paradigm and it is one of the most cited theory for the Big Bang
Redshift is when any electromagnetic radiation from an object is increased in wavelength
or shifted to a certain point in the spectrum. Whether the radiation is on the visible
spectrum or not, redder means the wavelength has increased.
Certain redshifts are an example of the Doppler effect.
Cosmological redshift is caused by the expansion of the universe and distant light sources
(usually more than a couple million light years away).