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72 Cards in this Set
- Front
- Back
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Life cycle of a sun-like star
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protostar forms from nebula, medium star is formed, red giant is formed, and then a white dwarf is formed
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What do all stars begin their lives as?
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planetary nebula
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How is a star born?
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when contracting gases and dust from a nebula are so hot and dense that nuclear fusion starts forming a star
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Star systems
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two or more stars
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How can an astronomer tell whether there is an unseen second star in a system?
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they observe the effects of its gravity on the brighter star and observe regular changes in the brightness of the star system
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What determines how long a star lives?
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it's mass
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Do stars with more mass last longer than stars with less mass?
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no
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What are the stages in the life of a high-mass star?
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nebula, protostar, high-mass star, supergiant, supernova, and if it is less massive it becomes a neutron star and the most massive turns into a black hole
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What determines which stage occurs after a supernova?
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mass
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What is the relationship between mass and the end stages of stars?
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low-medium mass stars = white dwarf; high mass stars = black hole or proton star
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What are five characteristics used to classify stars?
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color, temperature, size, composition, and brightness
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What reveals a star's temperature?
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color. cool stars= red; hotter stars= blue/white
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How can astronomers infer which elements are found in a star?
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by using a spectrograph
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What does a spectrograph do?
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separates light into colors and makes an image of the resulting spectrum
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What is the chemical composition of most stars?
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73% Hydrogen 25% Helium 2% Other
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What two factors determine how bright a star looks from Earth?
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absolute distance and absolute brightness
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What two things must an astronomer find out in order to calculate a star's absolute brightness?
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size and temperature
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Is a light-year a unit of time?
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no
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What do astronomers use parallax to measure?
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distant stars, the sun, and nearby stars
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Is the closer the star the more shift with parallax?
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yes
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What do astronomers look at to measure parallax shift?
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the same star at two different times of the year when Earth is on different sides of the sun
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telescope
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a device built to observe distant objects by making them clearer
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visible light
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electromagnetic radiation that can be seen with the unaided eye
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wavelength
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the horizontal distance between the crest of one wave and the crest of the next wave
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spectrum
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the range of wavelengths of electromagnetic waves
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optical telescope
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a telescope that uses lenses or mirrors to collect and focus visible light
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electromagnetic radiation
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energy that travels through space in the form of waves
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refracting telescope
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a telescope that uses convex lenses to gather and focus light
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convex lens
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a piece of transparent glass curved so that the middle is thicker than the edges
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reflecting telescope
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a telescope that uses a curved mirror to collect and focus light
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radio telescope
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a device used to detect radio waves from objects in space
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observatory
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a building that contains one or more telescopes
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constellation
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an imaginary pattern of stars in the sky
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spectrograph
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an instrument used that separates light into colors and makes an image of the resulting spectrum
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apparent brightness
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the brightness of a star as seen fro Earth
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absolute brightness
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the brightness of a star if it were at a standard distance from Earth
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light-year
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the distance that light travels in one year, about 9.5 million million km
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parallax
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the apparent change in position of an object when seen from different places
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nebula
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a large cloud of gas and dust in space, spread out in an immense volume
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protostar
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a contracting cloud of gas and dust with enough mass to form a star
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white dwarf
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the blue-white hot core of a star that is left behind after its outer layers have expanded and drifted out into space
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supernova
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the brilliant explosion of a dying super-giant star
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neutron star
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the small, dense remains of a high- mass star after a supernova
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pulsar
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a rapidly spinning neutron star that produces radio waves
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black hole
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an object whose gravity is so strong that nothing, not even light can escape
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binary star
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a star system with two stars
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eclipsing binary
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a binary star system in which one star periodically blocks light from another
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open cluster
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a star cluster that has a loose, disorganized appearance and contains no more than a few thousand stars
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globular cluster
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a large, round, densely-packed grouping of older stars
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galaxy
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a huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity
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spiral galaxy
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a galaxy with a bulge in the middle and arms that spiral outward in a pinwheel pattern
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elliptical galaxy
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a galaxy shaped like a round or flattened ball, generally containing only old stars
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irregular galaxy
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a galaxy that does not have a regular shape
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quasar
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an enormously bright, distant galaxy with a giant black hole at its center
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universe
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all of space and everything in it
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scientific notation
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a mathematical method of writing numbers using powers of ten
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big bang
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the initial explosion that resulted in the formation and expansion of the universe
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Hubble's law
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the observation that the farther away a galaxy is, the faster it is moving away
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cosmic background radiation
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the electromagnetic radiation left over from the big bang
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solar nebula
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a large cloud of gas and dust such as the one that formed our solar system
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planetesimal
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one of the small asteroid-like bodies that formed the building blocks of the planets
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dark matter
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matter that does not give off electromagnetic radiation but appears to be quite abundant in the universe
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dark energy
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a mysterious force that appears to be causing the expansion of the universe
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How is a radio telescope different from both a refracting telescope and a reflecting telescope?
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detect radio waves rather than light
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How is a radio telescope similar to both a refracting and a reflecting telescope?
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they all collect a for of electromagnetic energy
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Why have astronomers built the largest optical telescopes on top of mountains?
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less distortion due to water vapor and gases in the atmosphere
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Why have astronomers placed telescopes in space?
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some forms of electromagnetic radiation are blocked by the atmosphere
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What does the electromagnetic spectrum include?
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radio waves, infrared radiation, visible light, ultraviolet radiation, X- rays, and gamma rays
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What does the brightness of a star depend on?
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size and temperature
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Do astronomers think that the universe is likely to expand forever?
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yes
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How was the universe formed?
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the big bang, when the universe formed in an instant billions of years ago in an enormous explosion
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How was the solar system formed?
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about 5 billion years ago a giant cloud of dust collapsed to form our solar system
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