Astronomy Stars, Galaxies, and the Universe

Tools of Ancient Astronomy

Tools of Modern Astronomy

The Electromagnetic Spectrum The electromagnetic spectrum is a list of electromagnetic waves placed in order of increasing energy.

Tools of Modern Astronomy Astronomers use tools that focus different types of electromagnetic energy to study distant objects in space. Astronomers use tools that focus different types of electromagnetic energy to study distant objects in space. Telescopes What are these tools called?

Radio Wave Telescopes World’s Largest Radio Telescope: Arecibo Facility in Puerto Rico measures 1000 feet across, 167 feet deep, and 20 acres. Can we hear radio waves? No, radios convert electromagnetic radiation to sound energy we can hear.

Infrared Telescopes The United Kingdom Infrared Telescope in Hawaii. How does your body interpret infrared radiation? Heat

Visible Light Telescopes The Hubble Telescope is a light telescope that floats in space! Why would Hubble Telescope pictures be clearer than ones taken from Earth’s surface? There is no atmosphere to look through.

Ultraviolet Telescopes The Hopkins ultraviolet telescope being released by the Space Shuttle. Why would an ultraviolet telescope need to be in space? Earth’s atmosphere blocks ultraviolet radiation.

X-Ray Telescopes The Chandra X-Ray Telescope What else do we use x-rays for? Medical diagnosing like to see if you have a broken bone.

Gamma Ray Telescopes The gamma-ray telescope on Mt. Hopkins, Arizona. Besides stars, what else emits gamma-rays? Nuclear Explosions.

Characteristics of Stars  1) brightness, which astronomers describe in terms of magnitude or luminosity;  2) color;  3) surface temperature;  4) size;  5) mass (amount of matter)  1) brightness, which astronomers describe in terms of magnitude or luminosity;  2) color;  3) surface temperature;  4) size;  5) mass (amount of matter)

Magnitude and luminosity  A star's brightness as viewed from Earth is its apparent magnitude.  Luminosity is the rate at which a star emits energy.  A star's brightness as viewed from Earth is its apparent magnitude.  Luminosity is the rate at which a star emits energy.

Color and Temperature  A star's color depends on its surface temperature.  Dark red stars  2500 K.  Bright red stars  3500 K  Yellow stars (e.g. the Sun)  5500 K.  Blue stars  10,000 to 50,000 K  A star's color depends on its surface temperature.  Dark red stars  2500 K.  Bright red stars  3500 K  Yellow stars (e.g. the Sun)  5500 K.  Blue stars  10,000 to 50,000 K

Size and Mass  Astronomers measure the size of stars in terms of the sun's radius.  Astronomers express the mass of a star in terms of the solar mass, the mass of the sun.  The mass of the sun is written out as 2 followed by 30 zeros.  Astronomers measure the size of stars in terms of the sun's radius.  Astronomers express the mass of a star in terms of the solar mass, the mass of the sun.  The mass of the sun is written out as 2 followed by 30 zeros.

Nebula to Globule  New stars form from large, cold clouds of dust and gas.  Stars usually start to form in a nebula, a cloud of interstellar hydrogen gas and dust.  When the gas and dust are forced together, they form a slowly rotating globule. Gravitational forces survive through gas pressure and the globule starts to collapse, then the cooling occurs and the spin increases.  New stars form from large, cold clouds of dust and gas.  Stars usually start to form in a nebula, a cloud of interstellar hydrogen gas and dust.  When the gas and dust are forced together, they form a slowly rotating globule. Gravitational forces survive through gas pressure and the globule starts to collapse, then the cooling occurs and the spin increases.

Globule to Star  The globule starts to change into a protoplanetary disk (which could also become a planet) and a central core (which will become a star).  The core of the protoplanetary disk starts to increase in temperature.  When fusion starts to begin, that's when a protostar has been formed. If the temperature reaches about 27,000,000,000°F, nuclear fusion begins, then stars start to form.  The globule starts to change into a protoplanetary disk (which could also become a planet) and a central core (which will become a star).  The core of the protoplanetary disk starts to increase in temperature.  When fusion starts to begin, that's when a protostar has been formed. If the temperature reaches about 27,000,000,000°F, nuclear fusion begins, then stars start to form.

A Star is Born  When stars are born they come in different sizes and their color range from blue to red.  The size of a star depends on the gas and dust that have been collected during the birth of the star.  The color of the star depends on the surface temperature of the star.  The more mass a star starts out with the hotter and brighter it will be.  When stars are born they come in different sizes and their color range from blue to red.  The size of a star depends on the gas and dust that have been collected during the birth of the star.  The color of the star depends on the surface temperature of the star.  The more mass a star starts out with the hotter and brighter it will be.

Lives of Stars  Throughout a star's life, it tries to fight the inward pull of the force of gravity.  Stars live different lengths of time depending on the size.  The hotter and brighter a star is, the shorter their lives are.  Throughout a star's life, it tries to fight the inward pull of the force of gravity.  Stars live different lengths of time depending on the size.  The hotter and brighter a star is, the shorter their lives are.

Long Live the Stars!  For example, the sun would live for about 10 billion years while a star 20 times bigger than that will only live for 10 million years.

A Star’s Final Hours  When a star's supply of hydrogen runs out, it eventually dies.  The death of a star depends on what type of star it is and the size of the star.  Stars will either become a black dwarf, a neutron star or a black hole, depending on the size of a star.  When a star's supply of hydrogen runs out, it eventually dies.  The death of a star depends on what type of star it is and the size of the star.  Stars will either become a black dwarf, a neutron star or a black hole, depending on the size of a star.

The Evolution of Stars  Main Sequence Phase - Longest phase of a star’s life - hydrogen is burning in core - fusion energy and gravity are balanced  Red Giant Phase - all hydrogen in the core has become helium - gravity becomes stronger and the star begins to collapse  White Dwarf Phase - shells are blown away - remaining core is carbon and oxygen  Black Dwarf Phase - core has become so cold that it is difficult to see - the star has died  Main Sequence Phase - Longest phase of a star’s life - hydrogen is burning in core - fusion energy and gravity are balanced  Red Giant Phase - all hydrogen in the core has become helium - gravity becomes stronger and the star begins to collapse  White Dwarf Phase - shells are blown away - remaining core is carbon and oxygen  Black Dwarf Phase - core has become so cold that it is difficult to see - the star has died

Supernova  That’s not the end!  The collapsing core shrinks to a size about 6 miles in diameter  Then it “rebounds” outwards in less than a second, sending all of its gases and dust to be used again for the birth of a new star.  That’s not the end!  The collapsing core shrinks to a size about 6 miles in diameter  Then it “rebounds” outwards in less than a second, sending all of its gases and dust to be used again for the birth of a new star.

What’s left behind?  The gravity of the collapsing star that is left behind becomes a Black Hole  a region of space whose gravitational force is so strong that nothing can escape from it.  A black hole is invisible because it traps even light.  The gravity of the collapsing star that is left behind becomes a Black Hole  a region of space whose gravitational force is so strong that nothing can escape from it.  A black hole is invisible because it traps even light.

What’s at the center of a Black Hole?  All its matter is located at a single point in its center.  This point, known as a singularity, is much smaller than an atomic nucleus.  All its matter is located at a single point in its center.  This point, known as a singularity, is much smaller than an atomic nucleus.

A X-ray telescope picture of a black hole. Black Hole

Star Systems  A star system is a small number of stars which orbit each other bound by gravitational attraction.  A large number of stars bound by gravitation is generally called a star cluster or galaxy.  A star system is a small number of stars which orbit each other bound by gravitational attraction.  A large number of stars bound by gravitation is generally called a star cluster or galaxy.

Galaxies  A galaxy is a massive, gravitationally bound system consisting of stars, an interstellar medium of gas and dust, and dark matter all orbiting a common center of mass.  Our galaxy is called the Milky Way  A galaxy is a massive, gravitationally bound system consisting of stars, an interstellar medium of gas and dust, and dark matter all orbiting a common center of mass.  Our galaxy is called the Milky Way

The Universe  The Universe is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them.  Astronomical observations indicate that the universe is ± 0.12 billion years old[1] and at least 93 billion light years across.  The Universe is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them.  Astronomical observations indicate that the universe is ± 0.12 billion years old[1] and at least 93 billion light years across.

History of the Universe  According to the prevailing scientific theory, the universe has expanded from a gravitational singularity known as the Big Bang, a point in space and time at which all the matter and energy of the observable universe were concentrated.

Resources  pg pg            Green, Paul J. "Star." World Book Online Reference Center World Book, Inc.  Icko Iben Jr. & Alexander V. Tutukov. The Lives of Stars. 9 April  Ella Revzin, Matt Dietrich, and Rebecca Elsenheiwer.To Live and Die a Star. 9 April 2002.<  pg pg            Green, Paul J. "Star." World Book Online Reference Center World Book, Inc.  Icko Iben Jr. & Alexander V. Tutukov. The Lives of Stars. 9 April  Ella Revzin, Matt Dietrich, and Rebecca Elsenheiwer.To Live and Die a Star. 9 April 2002.<