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Ricky Nguyen

on 27 January 2014

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Transcript of Galaxies

What is a Galaxy?
a galaxy is a massive system that is held together by a gravitational attraction
it consist of millions or billions of stars, with gas and dust, and dark matter
dark matter is an important component that is poorly understood
contains varying number of planets, star systems, star clusters, and interstellar clouds (an accumulation of gas, plasma and dust)
ex: The Milky Way Galaxy
Where did it come from?
the word galaxy comes from the Greek word "galaxias"
a combination of theory and observations suggests that the first galaxies formed about a billion years after the
Big Bang

since then larger structures have been forming, such as galaxy clusters and superclusters
galaxy distributions and larger structures agree well with Big Bang simulations of the formation of structure in the universe and are helping to complete details of this theory
common form of a galaxy
it has a similar shape to an ellipse
composed of older, low mass stars, with sparse interstellar medium
ISM- is the matter that exists in the space between the star system in a galaxy
Elliptical Galaxy
Spiral Galaxy
Similar to our Milky Way Galaxy
it looks like a spiraling pinwheel
consists of flat, rotating disk
made up of stars, gas,and dust
has a a central concentration of stars known as the

named after its spiral structure
Irregular Galaxy
an unusual shape for a galaxy
the shape of galaxy has no pattern
this galaxy is uncommon and is not part of the
Hubble sequence

most irregular galaxies were once elliptical or spiral galaxies
they were deformed by their gravitation pull
may contain large amounts of gas and dust
Lenticular Galaxy
it is a galaxy that is in the middle of being an Elliptical and a Spiral galaxy
they are disk galaxies (like spiral galaxies)
used or lost most of their interstellar matter
consists of mostly aging stars (like elliptical galaxies)
it is difficult to tell them apart because they share common properties
Edwin Hubble
in 1925,he discovered Cepheid variables which we now call Andromeda Galaxy
with this he could tell that the group of stars was too far away to be part of the Milky Way
it was the first proof that other galaxies exist.
a variable star having a regular cycle of brightness with a frequency related to its luminosity, allowing estimation of its distance from the earth.
Edwin Hubble
Born -November 20, 1889
Died-September 28, 1953
An American astronomer who played an important and crucial role in establishing the field of extragalactic astronomy
Regarded as one of the most important observational cosmologists of the 20th century
He is known for showing that the recessional velocity increases with its distance from earth
Implying that the universe is expanding- Hubble's Law
This has also been previously discovered by
Georges Lemaitre
Hubble is

also known for providing evidence that any former know nebulae is actually galaxies beyond the milky way
Cosmology is the study of the origin, evolution, and eventual fate of the universe
Recessional velocity is the rate at which an object is moving away, typically from Earth.
our existence does not depend on galaxies
we rely solely on our planet and our Sun.
everything we need to live is here on earth .You can also say we rely on our moon as it does affect tidal activity in the oceans.
yes, we do live in a galaxy and by virtue I guess that is important to us. But for our existence we do not depend on the fact that we are a part of a galaxy.
Significance to Us
A galaxy cluster is a structure that consists of anywhere from hundreds to thousands of galaxies bound by gravity
Superclusters are large groups of smaller galaxy groups and galaxy clusters
How Galaxies tie into

The Universe
the universe has all of the galaxies inside of it
the universe contains galaxies
while galaxies such as our Milky Way Galaxy consists of billions of stars
these stars have planets orbiting them just like the planets in our Solar System
in our Solar System all of the planets including Earth orbit one star,the Sun
Future of Galaxies
in the future, spiral galaxies like the Milky Way Galaxy are expected to produce new generations of stars
they can do this as long as they have dense molecular clouds of interstellar hydrogen in their spiral arms
Elliptical Galaxies already have large amounts of this gas, so they will not produce more stars
About our own Milky
Way Galaxy
it is said that some time in the future our galaxy is going to collide with another named,"Andromeda"
Andromeda is approximately 2.5 light years away and in approximately 4 billion years they will begin colliding and in 6 billion years they will likely become forever joined by gravity and momentum
About our own Milky
Full transcript