Astronomy Origin and Fate of the Universe

Hubble’s Law Hubble’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 = Spectra Spectra Spectra are the colors produced when the wavelengths of light are separated.

The Doppler Effect The Doppler effect is a change of light or sound wavelengths as a source moves t tt toward or a aa away from the observer. Red shift = source is moving a aa away so wavelengths stretch into longer wavelengths Blue shift = source is moving c cc closer so wavelengths squeeze into shorter wavelenghts. B LUE TO YOU.

Deep Space Phenomena Based on the observed rates of expansion it is believed that about billion years ago all matter was concentrated into one “primeval atom”. BIG BANG This “atom” exploded and sent all matter and space expanding = BIG 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. nuclear fusion –Here gravity pulls particles together and nuclear fusion starts at 10,000,000 o C and a star is born.

The Horse Head Nebula

More Horse Head Nebula Shots

Types of Stars Depending on the conditions within a nebula, different types of stars can form: Red Giants = big, “cool” stars White Dwarfs = “small”, hot stars

How Are Stars Classified? Stars are classified by: –Temperature –Color –Luminosity / Brightness

Stars are Classified by Temperature and Color. HOTCOLD BLUEWHITEYELLOWORANGEREDBROWN

What is a Main Sequence Star?

What is a Main Sequence 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 Sequence”. Stars start out in the M MM Main Sequence and as the core cools, they move onto the giant category. A few rare stars are bigger and brighter and become s ss supergiants.

Stars are Classified by Brightness 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 Stars neutron star A neutron star results when a white dwarf collapses and the pressure converts the electrons into atomic nuclei to produce neutrons. neutron star supernova The outer portion of a neutron star may explode with incredible force producing a supernova.

Supernova What is a Supernova? Supernova 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. –M–Material from the explosion may form a new star called a p pp pulsar – a rapidly spinning neutron star. –T–The most massive stars collapse into black 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. ?