Chapter 8 glossary terms
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Electromagnet radiation is varying types of energy waves from radio waves to gamma rays. All forms of electromagnet radiation travel at the speed of light. (3.00 x 108
A refracting telescope uses a lens to collect light from an object.
A reflecting telescope uses a curved mirror to collect light from an object.
A satellite is a man-made object that orbits the Earth the Moon, or other celestial bodies.
- - An orbiter is a spacecraft that orbits a planet or other celestial body
- - They don't last long but get good pictures
Solar nebula theory
The theory that describes how stars and planets form from contracting spinning disks of gas and dust.
A celestial body made of hot gasses, mainly hydrogen and some helium
A vast cloud of gas and dust, which may be the birthplace of stars and planets
A contracting mass of gas that represents an early stage in the formation of a star
A nuclear reaction in which energy is produced when hydrogen nuclei combine to form helium nuclei.
The surface layer of the Sun.
- - An area of strong magnetic fields on the photosphere
- -When charged particles disturb the Sun's photosphere sunspots form
- - The photosphere is about 6000oC and sunspots are about 4500oC
A stream of fast-moving charged particles ejected by the Sun into the Solar system.
- Solar flares can occur where there are are complex groups of sunspots in which magnetic fields explosively eject intense streams of charge particles into space (Solar wind)
- When they hit the Earth as solar storms, they can disrupt telecommunications and damage electronic equipment
- Solar flares can result in shimmering curtains of green and/ or red light in the Earths polar regions called auroras
- They result when the high-energy charged particles are carried past Earth's magnetic field generating electric currents that flow towards the poles
- They charge gases in the Earth's upper atmosphere producing light in auroras
Importance of the Sun
- The solar energy from the Sun drives most processes on Earth that support our daily activities
- Solar energy powers the winds and ocean currents as well as weather
- the Sun emits radiation from across the entire electromagnet spectrum
- Earth's surface absorbs most of the visible light and emits infrared radiation to the atmosphere
- The process of reflecting and absorbing energy warms Earth's surface
A stars luminosity is a measure of the total amount of energy it radiates per second.
The brightness of a star at equal distances
- Measured on a stellar magnitude scale which goes from -26 (The Sun) to over 6 in magnitude
A spectroscope is an instrument that produces a pattern of colours and lines, called a spectrum, from a narrow beam of light.
The lines that Fraunhofer observed when looking at the Sun are called spectral lines. A star's spectrum identifies the elements within the star's photosphere.
Hertzsprung-Russell (H-R) diagram
Astronomers started to look from patterns in the properties of stars and observed that each star type has certain properties. These relationships can be shown on a graph called the Hertzsprung-Russell (H-R) diagram. Their graph had star colour (ranging from blue to red) on the x-axis and absolute magnitude (ranging from dimmer to brighter) on the y-axis. The H-R diagram below has luminosity instead of absolute magnitude. Using these H-R graphs Astronomers have discovered several different categories of stars.
The central band of stars stretching from upper left to lower right of the H-R diagram is called the main sequence. The main sequence accounts for about 90 percent of the stars that you can see from Earth.
The phase of a star where it simply cools and fades away, this happens at the end of it's life.
a star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass.
If the star began with a mass of about 12 to 15 solar masses, the core will shrink to approximately 20 km in diameter. The pressure is so great that electrons are squeezed into protons and the star eventually becomes a neutron star. The first neutron star to be discovered is in the center of the crab nebula.
How low-mass stars evolve
Low mass stars (red dwarfs) have less mass than the Sun and consumes their hydrogen slowly over a period that may be as long as 100 billion years. As they age they slowly lose mass becoming a very faint white dwarf. While white dwarfs no longer produce their own energy they are incredibly hot, taking them tens of billions of years from them to cool down. Astronomers theorize that if they do cool down they will become dark embers called black dwarfs.
How intermediate-mass stars evolve
Intermediate-mass stars, such as the Sun consume their hydrogen faster than low mass stars. When their hydrogen runs out, the core collapses. As the core contracts, the temperature increases and the outer layers begin to expand. The expanded layers are cooler and appear red called a red giant. In about 5 billion years the Sun will become a red giant and it will become so large that it's diameter will extend to the current orbit of Mars. Eventually, the layers will disappear into space, and the Sun will become a white dwarf.
How high-mass stars evolve
Stars that are 12 or more solar masses are high-mass stars and consume fuel even faster than intermediate-mass stars. These stars die more quickly and more violently. Heavier elements form by fusion and the star expands into a supergiant. Iron forms in the outer core and the core collapses violently and a shock wave travels through the star. the outer portion of a star explodes creating a supernova. A supernova can be millions of times brighter than the original star was. During a supernova explosion, the heavier elements formed are ejected into the universe becoming parts of new stars, and some form planets, and other bodies.
The most spectacular deaths happen to stars whose initial masses are more than 25 solar masses. The remnant of the supernova explosion is so massive that nothing can compete with the crushing force of gravity and it crushes into a black hole. A black hole is a tiny patch of space that has no volume but does have a mass. The gravitational force of a black hole is so strong that nothing can escape it including light.
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