Astronomy

Origin and Fate of the Universe

Hubble’s LawHubble’s LawHubble’s law basically says that the

universe is expanding.That is to say that the space between

galaxies is increasing; with greater distance is greater speed.

Closer galaxies are moving apart slower than those galaxies farther away.

HOW DO WE KNOW?

Hubble’s Evidence = Hubble’s Evidence = SSppeeccttrraa

SSppeeccttrraa are the colors produced when the wavelengths of light are separated.

The Doppler EffectThe Doppler Effect

The Doppler effect is a change of light or sound wavelengths as a source moves towardtoward or awayaway from the observer.

Red shiftRed shift = source is moving awayaway so wavelengths stretch into longer wavelengths

Blue shiftBlue shift = source is moving closercloser so wavelengths squeeze into shorter

wavelenghts. BLUE TO YOU.BLUE TO YOU.

Deep Space Deep Space PhenomenaPhenomena

Based on the observed rates of expansion it is believed that about 15-20 billion years ago all matter was concentrated into one “primeval atom”.

This “atom” exploded and sent all matter

and space expanding = BIG BANGBIG BANG

What are Stars?

•Star = a hot, glowing sphere of gas that produces energy by fusion (of hydrogen molecules).–Some stars produce more energy therefore they are hotter.

How Do Stars Form?

•NebulaNebula = a cloud of dust and gas where stars are born. –Here gravity pulls particles together and nuclear fusionnuclear fusion starts at 10,000,000 oC and a star is born.

The Horse Head Nebula

More Horse Head Nebula Shots

Types of StarsTypes of Stars

Depending on the conditions within a nebula, different types of stars can form:

Red Giants = big, “cool” starsWhite Dwarfs = “small”, hot stars

How Are Stars How Are Stars Classified?Classified?

•Stars are classified by:–Temperature–Color–Luminosity / Brightness

Stars are Classified by Temperature and Color.

• HOT COLD

BLUE WHITE YELLOW ORANGE RED BROWN

What is a Main Sequence What is a Main Sequence Star?Star?

What is a Main Sequence What is a Main Sequence Star?Star?

• The H-R diagram represents a pattern that was discovered that allows stars to be compared by brightness and color.

• The majority of stars are found in a band stretching diagonally across the diagram called the “Main SequenceMain Sequence”.

• Stars start out in the Main SequenceMain Sequence and as the core cools, they move onto the giant category. A few rare stars are bigger and brighter and become supergiantssupergiants.

Stars are Classified by Stars are Classified by BrightnessBrightness

• Actual brightness is how bright a star really is.

• Actual brightness does not change, it is an absolute value.

• Example: a 40 watt light bulb is actually converting 40 watts of energy into light.

• Apparent brightness is how bright a star looks from earth.

• Apparent brightness changes depending on distance from earth and viewing conditions (atmosphere).

• Example: a 40 watt light bulb 10 feet away appears brighter than a 40 watt bulb 100 feet away.

…And After Stars are Born?

Life Cycle of a Star

Neutron StarsNeutron Stars

A neutron starneutron star results when a white dwarf collapses and the pressure converts the electrons into atomic nuclei to produce neutrons.

The outer portion of a neutron starneutron star may explode with incredible force producing a supernovasupernova.

What is a SupernovaSupernova?• SupernovaSupernova is when the core of a star

collapses and the outer portion explodes. This is the “death of a star”.

• What remains when a star dies out depends on the mass of the star.– Material from the explosion may form a

new star called a pulsarpulsar – a rapidly spinning neutron star.

– The most massive stars collapse into black holesblack holes.

What is a Black Hole?

• Black Hole = the most dense thing known to exist in the universe. The gravity of a black hole is so great that even light can not escape the pull of a black hole.

The massive density of Black Holes creates a gravitational force that pulls in anything that comes within reach: the reach of this force is called the event horizon.

The fate of objects that enter a Black Hole is still uncertain.

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