Science 9 Unit 5

STUDY
PLAY

Terms in this set (...)

Equinox
either of the two times a year (once in Spring and once in Fall) when the Sun crosses the equator and day and night are equal in length; usually about March 21st and September 23rd
Geocentric
the Earth centered model of the solar system originally proposed about 2000 years ago by the Greek philosopher Aristotle
Heliocentric
the Sun centered model of the solar system first proposed by Polish astronomer Nicolas Copernicus
Ellipses
an oval formed around two foci ( a circle is formed around one focus); the orbital paths of planets travelling around the sun are ellipses
Astronomical Units
a measure of the distance used to describe the position of planets relative to the Sun; 1 AU is equal to the average distance from the center of the Earth to the center of the Sun (149 599 000 km)
Light Year
the distance that light travels in 1 year (approximately 9.5 trillion kms); used to measure distances between stars and galaxies
Nebulae
vast clouds of gas (mostly hydrogen) and dust in space, where stars form.
Interstellar matter
the gases and dust that exist in the space between stars
Prostar
a contracting mass of gas in the first stage of a stars formation
Sun like
two of the main types of stars that can form (the other being massive stars, which are by comparison, larger in mass than sun like stars)
Massive main sequence
on the Hertzsprung-Russell diagram, the stage in the life cycle of most stars during which they produce energy by converting hydrogen into helium; main sequence stars, including our sun, are in a stable state
Red Supergiant
the stage in the life of a massive star during which the star increases in size and become very bright
Red Giant
the stage in the life cycle of a Sun like star during which the star increases in size and becomes very bright
White Dwarf
one of the latter stages in the life cycle of a Sun like star during which the star collapses; white dwarfs are hot but very faint
Black Dwarf
the final phase in the life cycle of a Sun like star
Super Nova
an enormous explosion the marks the death of a massive star
Neutron Star
a small super dense remnant of a super nova
Black Hole
a super dense remnant of a super nova;an object around which gravity is so intense that light can not escape
Constellations
groupings of stars that form patterns in the night sky. Ursa Major is an example
Asterism
a distinct star grouping that is not one of the 88 recognized constellations. The Big Dipper is part of the constellation Ursa Major
Galaxy
a grouping of millions and billions of stars, gas and dust held together by gravity
Solar Wind
streams of electrically charged particles discharged by the \sun in every direction; Solar wind passes the Earth at nearly 400 kms/s
Asteroid
small rocky bodies orbiting the Sun and lying in narrow belt between Mars and Jupiter
Comets
a celestial body composed of dust and ice that orbits the Sun, it has a bright center and a long faint tail that always points away from the sun
Meteoroids
a solid body, usually a fragment of rock or metal, traveling in space with no particular path
Meteor
a meteorite that enters Earth's atmosphere, where heat and friction cause it to glow brightly
Meteorite
the remains of a meteor that do not burn up completely and so last long enough to hit Earth's surface
Azimuth
the angle between the most northerly point of the horizon and the point directly below a celestial body; also the horizontal angle or direction of a compass bering
Altitude
the height of a celestial body above the horizon, ranging from 0 at sea level to 90 degrees straight up
Zenith
the highest point in the sky directly overhead
Ecliptic
the apparent path of the Sun and planets through the stars during the year, as viewed from Earth
Microgravity
the condition in which the gravitational forces that act on a mass are greatly reduced
Gravity
the force of attraction between masses
Satelites
a small body that orbits a larger one; satellites may be natural, such as a moon orbiting a planet, or artificial, such as a spacecraft put into orbit around Earth by humans for research or communication purposes
Refracting Telescope
a type of optical telescope that uses two lenses to gather and focus light
Reflecting Telescope
a type of optical telescope that uses mirrors instead of lenses to gather and focus light
Hubble Space Telescope
one of the largest, most complex satellites ever built; launched in 1990 from the space shuttle Discovery, the HST (named for american astronomer Edwin P. Hubble) uses a series of mirrors to focus light from extremely distant objects
Electromagnetic Energy
forms of radiated energy that travel at the speed of light (300 000 km/s) although they have different wavelengths and frequencies than light
Electromagnetic Spectrum
the complete range of wavelengths over which electromagnetic energy extends; including gamma rays, x-rays, ultra-violet rays, visible light, infrared radiation, microwaves, and radio and television signals
Radio Telescope
a telescope system that collects and analyzes radiation in the radio frequency range from the stars and other bodies in space
Interferometry
a technique of combining the observations of two of more telescopes to produce images that have better resolution that what on telescope alone could produce
Space Probes
unmanned satellites or remote controlled landers used to explore areas or objects in space that are too difficult or dangerous to send humans to
Paralax
the apparent shift in position of a nearby object against a distant background when the object is viewed from two different positions
Spectrometer
an instrument used my astronomers to observe and measure the spectrum of a star
Space Junk
refers to all the pieces of debris that have fallen off rockets, satellites, space shuttles and space stations and remain floating in space