Astronomy The scientific study of matter in outer space, especially the positions, dimensions, distribution, motion, composition, energy, and evolution of celestial bodies and phenomena.

Big Bang–origin of the Universe created between 10 & 20 billion years ago from a cosmic explosion that hurled matter and in all directions. created between 10 & 20 billion years ago from a cosmic explosion that hurled matter and in all directions. initially suggested because it explains why distant galaxies are traveling away from us at great speeds; also predicts the existence of cosmic background radiation initially suggested because it explains why distant galaxies are traveling away from us at great speeds; also predicts the existence of cosmic background radiation Although widely accepted, it probably will never be proved Although widely accepted, it probably will never be provedhttp://liftoff.msfc.nasa.gov/academy/universe/b_bang.html

Galaxies Galaxy - a massive system of hundreds of millions of stars, all gravitationally interacting, and orbiting about a common center. Galaxy - a massive system of hundreds of millions of stars, all gravitationally interacting, and orbiting about a common center.

Galaxies Astronomers estimate that there are about 125 billion galaxies in the universe.

Galaxies There are two types of galaxies – distinguished by the amount of energy they emit: Normal – can be thought as the total energy they emitted (sum emitted) from each of the stars found in the galaxy.

Galaxies Active - there is a great deal more emitted energy than there should be... Active - there is a great deal more emitted energy than there should be... (this excess energy is found in the infrared, radio, UV, and X- ray regions of the electromagnetic spectrum. )

Spiral Galaxy has central lens-shaped, bright nucleus made of millions of stars ¾ of galaxies are spiral Rotating with 2 to 4 arms 2 to 4 arms

Spiral Galaxy

A Barred Spiral Galaxy: has massive straight bar runs through; gravita- tional pull from the bar causes interstellar gas and dust clouds to form a pair of spiral arms that extend from the ends of the bar

Elliptical Galaxy shape ranges from almost spherical to lens-shaped (lenticular galaxy) shape ranges from almost spherical to lens-shaped (lenticular galaxy)

Galaxies Irregular Galaxy – uneven, cloud of stars and dust. i.e. Magellanic Clouds Irregular Galaxy – uneven, cloud of stars and dust. i.e. Magellanic Clouds

Our Galaxy Milky Way Galaxy – our sun is one of billion stars. our sun is one of billion stars. At least140,000 light years across At least140,000 light years across 1,000 light years thick at center 1,000 light years thick at center The halo, which is a spherical cloud surrounding the disk, contains only about 2% as many stars as the disk. It contains old and cool stars, since it has little gas & dust. The halo, which is a spherical cloud surrounding the disk, contains only about 2% as many stars as the disk. It contains old and cool stars, since it has little gas & dust. all the stars visible to the unaided eye from Earth belong to the Milky Way all the stars visible to the unaided eye from Earth belong to the Milky Way

Milky Way Galaxy What kind of galaxy is ours? (mass (latest value) = about 2,000,000 times that of the Sun (mass (latest value) = about 2,000,000 times that of the Sun )

Active Galaxy Active Galaxy There are several types of active galaxies: Seyferts, quasars, and blazars. Quasars - An enormously bright object at the edge of our universe which emits massive amounts of energy... Active galaxy nuclei 

Active Galaxy Quasars – (quasi-stellar radio source) - brightest objects in the universe - larger and more massive than any known star any known star - is considered to possibly be a “proto-galaxy” (we will not cover Seyferts and blazars, for more info: s.html) s.html s.html.

This is what a quasar would look like from here…. This is what a quasar would look like from here…. Go to the site for more information

The Milky Way Galaxy, commonly referred to as just the Milky Way, or sometimes simply as the Galaxy,[a] is the home galaxy of the Solar System, and of Earth. It is agreed that the Milky Way is a spiral galaxy, with observations suggesting that it is a barred spiral galaxy. It contains billion stars and an estimated 50 billion planets, 500 million of which could be located in the habitable zone of their parent star. The Milky Way is part of the Local Group of galaxies and is one of around 200 billion galaxies in the observable universe. The Milky Way Galaxy, commonly referred to as just the Milky Way, or sometimes simply as the Galaxy,[a] is the home galaxy of the Solar System, and of Earth. It is agreed that the Milky Way is a spiral galaxy, with observations suggesting that it is a barred spiral galaxy. It contains billion stars and an estimated 50 billion planets, 500 million of which could be located in the habitable zone of their parent star. The Milky Way is part of the Local Group of galaxies and is one of around 200 billion galaxies in the observable universe. The Solar System is located in the Milky Way galaxy halfway out from the center, on the inner edge of the Orion–Cygnus Arm. The Sun orbits around the center of the galaxy in a galactic year—once every million Earth years. The Solar System is located in the Milky Way galaxy halfway out from the center, on the inner edge of the Orion–Cygnus Arm. The Sun orbits around the center of the galaxy in a galactic year—once every million Earth years. It is generally believed that a black hole does exist at the center of the Milky Way galaxy. The latest value we have seen is that it has a mass of about 2,000,000 that of the Sun. In fact, it is believed that this may be common for most galaxies. Observational evidence supports these ideas more and more. However, you must keep in mind that due to the large absorption and source confusion when trying to look into the center of a galaxy, it is very, very hard to see what's there! It is generally believed that a black hole does exist at the center of the Milky Way galaxy. The latest value we have seen is that it has a mass of about 2,000,000 that of the Sun. In fact, it is believed that this may be common for most galaxies. Observational evidence supports these ideas more and more. However, you must keep in mind that due to the large absorption and source confusion when trying to look into the center of a galaxy, it is very, very hard to see what's there! The "Milky Way" is a translation of the Latin Via Lactea, in turn translated from the Greek Γαλαξίας (Galaxias), referring to the pale band of light formed by stars in the galactic plane as seen from Earth. The "Milky Way" is a translation of the Latin Via Lactea, in turn translated from the Greek Γαλαξίας (Galaxias), referring to the pale band of light formed by stars in the galactic plane as seen from Earth.