chapter 8 glossary terms
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(above is the electromagnetic spectrum)
- Radiation consisting of electromagnetic waves that travel at the speed of light (3.00x108 m/s)
- ex. visible light, gamma rays, x-rays, microwaves, and radio waves.
- A refracting telescope is an optical telescope. An optical telescope detects visible light.
- There are 2 kinds:
- refracting and reflecting telescopes
Refracting telescopes use a lens to collect light.
- A reflecting telescope is an optical telescope. An optical telescope detects visible light.
- There are 2 kinds:
- refracting and reflecting telescopes.
A reflecting telescope uses a mirror to collect light from an object.
- An artificial (man-made) object or vehicle that orbits earth, the moon, or other celestial bodies.
- A satellite can also be a celestial body that orbits another of larger size.
- ex. the moon is earth's natural satellite.
- Orbiters are observatories that orbit other planets.
- Average operational life: 2-3 years
- Equipped with high-res. digital cameras
Solar nebula theory
- The solar nebula theory states that stars and planets form together.
- The theory 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.
- eg. the sun
A vast cloud of gas and dust, which may be the birthplace of stars and planets.
The hot, condensed object at the centre of a nebula.
- The process of energy production in which hydrogen nuclei combine to form helium nuclei.
- nuclear fusion begins when the temperature of a protostar reaches around 10 000 000oc.
- The surface layer of the sun.
- The photosphere is several thousand miles deep.
- An area of strong magnetic feilds on the photosphere.
- When charged particles disturb the suns photosphere, sunspots form.
- The photosphere is about 60000c and sunspots are about 45000c.
- A stream of fast-moving charged particles ejected by the sun into the solar system.
- These events (solar storms) can disrupt telecommunications and damage electronic equipment aboard spacecraft.
- They can overload the electrical power network, causing large-scale power blackouts.
- Solar flares can occur where there are complex groups of sunspots, in which magnetic fields explosively eject intense streams of charged particles into space (solar wind).
- When they hit 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 earth's polar regions called auroras.
- They charge gasses in 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.
- Sun emits radiation from across the entire electromagnetic spectrum.
- Earth's surface absorbs most of the visible light and emits infrared radiation into 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 adiates per second.
- (it is power in Joules per second J/s)
- A star's absolute magnitude is how bright the star would be at a distance of 32.6 light years from earth.
- eg. the absolute magnitude of the sun is 4.7.(the sun is faint compared to others)
- A spectroscope is an instrument that produces a pattern of colors and lines, called a spectrum, from a narrow beam of light.
- It usually projects the spectrum onto a photographic plate or a digital detector.
- Certain specific wavelengths within a spectrum characterized by lines; spectral lines identify specific chemical elements within the star's photosphere.
Hertzsprung-Russel (H-R) diagram
- A graph that compares the properties of stars.
- The graph has star colour(temp) on the x-axis, and absolute magnitude on the y-axis.
- Using this graph astronomers have discovered several different categories of stars.
- The central band of stars stretching from the upper left to lower right of the H-R diagram.
- The main sequence accounts for about 90 percent of the stars that can be seen from earth.
- A white dwarf is a small, dim hot star.
- How they are formed:
- Low mass stars, or red dwarfs, consume their hydrogen slowly, up to as long as 100 billion years. During that time, they are slowly evaporating, and eventually all thats left is a very faint white dwarf.White dwarfs no longer produce energy of their own, but are incredibly hot.
- A supernova is a massive explosion in which the entire outer portion of a star is blown off.
- A supernova can be millions of times brighter that the original star was.
- During this explosion, the heavier elements formed (from before the explosion by fusion) are ejected into the universe.
- Some of the elements become parts of new stars, and some form planets and other bodies.
- A star so dense that only neutrons can exist in its core.
- If the star began with a mass of about 12 to 15 solar masses, the core will shrink to approximately 20km in diameter.
- The pressure is so great that electrons are squeezed into protons, and the star eventually becomes a neutron star.
How low-mass stars evolve
- Low mass stars (red dwarfs) have less mass than the sun and consume 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.
- White dwarfs no longer produce energy, but are very hot. they may take billions of years to cool down.
How intermediate-mass stars evolve
- Intermediate-mass stars such as the sun, consume their hydrogen faster than low-mass stars.
- When their hydrogen is used up, 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.
How high-mass stars evolve
- Stars that are 12 or more solar masses are high-mass stars that consume fuel even faster than intermediate-mass stars.
- These stars die more quickly and violently.
- Heavier elements form by fusion and the star expands into a supergiant. Iron forms in the core and the core collapses violently, and a shock wave travels through the star.
- The outer portion of the star explodes producing a supernova.
The phenomenon in which one celestial object moves directly in front of another celestial object, as viewed from earth.
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