BIG BANG + GALAXIES

THE BIG BANG THEORY This theory states that the universe began from an initial point or singularity which has expanded over billions of years to form the universe as we now know it. (It was not really a big bang.)

What happened. Scientists believe that the Universe was initially so hot and dense, that even elementary particles like protons and neutrons could not exist. Instead, different types of matter (called matter and anti-matter) collided together, creating pure energy. But as the Universe began to cool during the first few minutes, protons and neutrons began to form. Then slowly over time these protons, neutrons and electrons came together to form Hydrogen and small amounts of Helium. During the billions of years that followed, stars, planets and galaxies formed to create the Universe as we see it today.

Pieces of Evidence Supporting the Big Bang Red Shift The presence of Background Radiation

Red Shift- Every galaxy seems to be moving away from Earth Red Shift- Galaxies seem to be racing away from the center of the Universe. Red Shift- Every galaxy seems to be moving away from Earth Hubble’s Law- The farther away the galaxy, the faster it is receding (moving away) from the earth. Astronomers conclude the universe is expanding at tremendous speeds.

Red shifted Red has the lowest frequency / longer wavelengths Left = “normal” Right = distant galaxy

All Galaxies are Red Shifted

Doppler Shift for Light We get the same effect for light as for sound.

Background Radiation Energy left over from the Big Bang is evenly spread out throughout the universe. If the universe was initially very, very hot as the Big Bang suggests, we should be able to find some remnant of this heat. In 1965, Radioastronomers Arno Penzias and Robert Wilson discovered a 2.725 degree Kelvin (-454.765 degree Fahrenheit, -270.425 degree Celsius) Cosmic Microwave Background radiation (CMB) which pervades the observable universe.

Measuring the Afterglow of the Big Bang Wilkinson Microwave Anisotropy Probe (WMAP) Launched: Summer, 2001 (NASA/WMAP Science Team)

A cosmic sonogram…. 9 years of images compiled into one image of the “night sky” WMAP Actual Sky Maps NASA/WMAP Science Team

Expanding Universe If the universe is expanding, then the objects near the very edge of the universe are the oldest objects in the universe. The most distant known objects in the universe are over 13 billion light years from the Earth

What Happens Next? Astronomers feel that the Big Bang theory leads to many possible futures for the Universe, here are a couple.

Open Universe Galaxies will continue racing outward (continue to expand). All of the stars will die off as the last of their energy is released. There will be nothing left, total emptiness.

Closed Universe Gravitational attraction between the galaxies will cause the movement away from each other to slow and, eventually come to a halt. The gravitational pull will begin to pull the galaxies back to the center of the universe.

Closed Universe cont. All of the matter and energy will again come close together and end in a central area (possibly no larger than a dime). Then another Big Bang will occur and the formation of the universe will begin all over again. This restructuring may occur once every 80 to 100 billion years.

Expanding Universe If galaxies are all moving away, then at some point they were all much closer. Hubble’s Law implies the Universe is expanding. Hubble Telescope -> Put in orbit around Earth In 1990. Takes high Resolution images of space

“An expanding universe does not preclude a creator, but it does place limits on when he might have carried out his job.” -Steven Hawking, A Brief History of Time

Galaxies

GALAXIES A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. Galaxies range in size -- few thousand stars (1,000) to giants with one hundred trillion stars (100,000,000,000,000) Galaxies are categorized according to their visual morphology as elliptical, spiral and irregular. Many galaxies are thought to have black holes at their active centers

The “Discovery” of Galaxies At the beginning of the 20th century, what we now call spiral galaxies were referred to as “spiral nebulae” and most astronomers believed them to be clouds of gas and stars associated with our own Milky Way. The breakthrough came in 1924 when Edwin Hubble was able to measure the distance to the “Great Nebula in Andromeda” (M 31, at right) and found its distance to be much larger than the diameter of the Milky Way. This meant that M 31, and by extension other spiral nebulae, were galaxies in their own right, comparable to or even larger than the Milky Way. Edwin P. Hubble (1889-1953)

Spiral Galaxies Pinwheel shape Huge, about 32,000 to 160,000 light years across Young and old stars present New stars forming Revolve quickly around a central bulge, looks like a thin disk from the side with a halo present Large amounts of gas and dust

The Nuclear Bulge of M31 Young stars have formed along the foreground spiral arm. M31’s two satellite galaxies M32 and NGC 205, both dwarf elliptical galaxies, are in the bottom center and upper right. (NOAO/AURA Photos)

Examples of Spirals

Elliptical Galaxies Round to oval shape, Bulge but no disk, halo present Massive, 6.5 million light years across Almost no new stars, mainly old stars present Rotate as a whole with each star having a unique orbit Small amounts of gas and dust

Irregular Galaxies No regular shape, Halo is present, may show signs of a bulge 3,200 to 32,500 light years across Many new stars present with mostly young blue stars Unsure of movement Very large amounts of gas and dust

Clusters of Galaxies Rather than occurring individually in space, galaxies are grouped in clusters ranging in size from a few dozens to thousands of galaxies. The Coma Cluster, shown at right, is 300 million light years from the Milky Way and contains more than 1,000 (and possibly as many as 10,000) galaxies. The Milky Way is a member of a small cluster called the Local Group which contains about 40 galaxies. The largest member of the Local Group is M 31, with the Milky Way coming in second in size. (NOAO/AURA Photo)

Milky Way Galaxy Our galaxy Spiral in shape 100,000 light years across

Units of distance – Light Year Light year is a unit of distance Light moves at a velocity of 300,000 kilometers per second or 186,000 thousand miles per second. So, in one year it can travel about 10 trillion km. The nearest star Proxima Centauri is 4.24 light years away.

Units of distance- Astronomical Unit A little closer to home to home we use an AU or astronomical unit which is the average distance between the Earth and the sun to measure distances in our solar system. 1 AU=93 million miles Mercury =.39 Earth=1.0 Jupiter=5.2

SPIRAL GALAXIES Size – arm extend outward Stars – young Movement – rotate quickly Spiral galaxies have three main components: a bulge, disk, and halo (see above). The bulge is a spherical structure found in the center of the galaxy. This feature mostly contains older stars. The disk is made up of dust, gas, and younger stars. The disk forms arm structures. Our Sun is located in an arm of our galaxy, the Milky Way. The halo of a galaxy is a loose, spherical structure located around the bulge and some of the disk. The halo contains old clusters of stars, known as globular clusters.

Elliptical Galaxies Elliptical galaxy M87 What ellipticity does this Elliptical galaxies are shaped like a spheriod, or elongated sphere. Size – largest Stars – present and older Elliptical galaxies are given a classification that corresponds to their elongation from a perfect circle, otherwise known as their ellipticity. The larger the number, the more elliptical the galaxy is. So, for example a galaxy of classification of E0 appears to be perfectly circular, while a classification of E7 is very flattened. Elliptical galaxy M87 What ellipticity does this Galaxy have??

IRREGULAR < Large Magellanic Cloud Shape – not distinct, used to Be spiral or elliptical Size – Stars – present Movement Irregular galaxies have no regular or distinct structure. They are divided into two groups, Irr I and IrrII. Irr I type galaxies have regions of elemental hydrogen gas, and many Population I stars, which are young hot stars. Irr II galaxies simply seem to have large amounts of dust that block most of the light from the stars. All this dust makes is almost impossible to see distinct stars in the galaxy.