Earth Space Systems. Semester 1 Exam. Astronomy Vocabulary

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1 Earth Space Systems Semester 1 Exam Astronomy Vocabulary Astronomical Unit- Aurora- Big Bang- Black Hole- 1AU is the average distance between the Earth and the Sun (93 million miles). This unit of measurement is used to compare distances between other astronomical bodies. A bright display of changing colorful light caused by solar radiation interacting with the magnetosphere in our upper atmosphere and occurring at both polar regions. The theory that states the universe began as a small mass that exploded violently. A massive star that collapses to a small volume and great density and whose gravity is so strong that it does not allow any radiation to escape. Coronal Mass Ejection (CME/Solar Flare) It occurs when a solar prominence ejects a large amount of hot, magnetic radiation from the Sun s surface. This eruption typically originates at the Sunspot location on the Sun s surface. A solar flare can cause great damage to satellites and electronic devices on Earth. Degrees Kelvin A unit of measurement used to measure the surface temperature of a star. Add 273 degrees to the number to convert to Celsius.

2 Eclipse A total or partial blocking of one object in space by another. The blocking of the light of one celestial body by another passing in front of it. Elliptical Orbit Giant Star The elliptical shaped path that planets and comets take around host stars. The Moon also has an elliptical orbit around Earth. A star with a large mass. This category includes White and Blue Stars on the Main Sequence as well as the Red and Super Red Giants that are off the Main Sequence. Kepler s Laws Law #1- The revolutionary path of each planet around the Sun is elliptical. Law #2-When planets orbit the Sun, they travel faster when they are nearer the Sun and slower when they are farther away. Law #3- The farther a planet is away from the Sun then its orbital period will be longer. Lunar Eclipse It occurs during a Full Lunar phase. The Earth moves directly between the Sun and the Moon. The Earth s shadow is cast directly on the lighted Full Moon. The Lunar Eclipse is more common and lasts longer than a Solar Eclipse.

3 Main Sequence Star Nebula A star plot on the diagonal line in the Hertzsprung - Russell diagram (H-R) which graphs luminosity and surface temperature. Once a star is stable and its gravitational inward pull overcomes the stars outward release of energy, it can be graphed on the Main Sequence. A star lives about 90% of its lifetime on the Main Sequence. Also, 90% of all stars are main sequence stars. Its life on the Main Sequence occurs after the Protostar stage. A dense cloud of hot dust and gas where Protostars (young stars) form. Nebular Theory A Theory that states that our Sun and the planets in our Solar system were formed from the nebular remnants of a Supernova. Nebular remnants from the Supernova contain heavy elements like iron which is abundant in our planet. Newton s Universal Law of Gravitation Anything with mass has an attractive force with anything else that has mass. Nuclear Fusion The process by which Hydrogen atoms join or fuse together in the Sun s core to form Helium.

4 Planetary Probe Protostar Spacecrafts that explore celestial bodies like satellites, planets, stars asteroids and comets. Some examples include Apollo 11 and the Eagle; Soho (Sun) satellite; Opportunity and Spirit (Mars); Curiosity (Travelling to Mars now.); Cassini (Saturn) A contracting cloud of dust and gas with enough mass to form a young star. Radio Telescope Revolution Rotation A ground based, big dished telescope designed to make observations in radio wavelengths rather than visible wavelengths. They are less affected by weather and the atmosphere as are ground based optical telescopes. Their disadvantage is that radio waves will interfere so they are placed on mountain tops or hidden in valleys. The movement of a celestial object around another celestial object. The spinning motion of a planet, star or satellite (Moon) on its axis. Earth s rotational period is 24 hours. The Sun s rotational period is about 29 Earth days. The Moon s rotational period is 27.3 days.

5 Satellite- based Telescope A telescope that is attached to a space probe that observes distant celestial objects by making them appear closer. Examples include the Hubble Telescope that views stars and distant galaxies or the Kepler Telescope which discovers new planets and solar systems in our Milky Way Galaxy. The Webb Telescope, just recently launched, will soon look farther into the Universe than any other prior telescope. Solar Eclipse It occurs during a New Moon lunar phase when the Moon is directly between the Sun and the Earth. The Moon s shadow covers the Earth. A Total Solar Eclipse is rare and is short lived for a small geographic area. The area where the Total Eclipse occurs is covered by the Umbra (darkest shadow). Spectrometer An instrument that measures the spectrum of a light source such as light from a distant star or galaxy. Astronomers use spectrographs to determine the elements that are found in stars. When the star s light is seen through a spectrograph, each absorbed wavelength is shown as a dark line on a spectrum.

6 Star Cycle The formation, evolution and death of a star. The path of the star cycle depends on the mass of the stable star on the Main Sequence. All stars form in Nebulae. The first stage is the Protostar. Once stable, it becomes a Main Sequence star. Upper left on the Sequence are the massive, hotter and more luminous Blue and White stars. The middle of the sequence has medium mass yellow (G) stars like our Sun. The lower section of the Main Sequence has smaller, cooler and less luminous Red stars. The more massive Blue and White stars live shorter lives while the less massive Red stars live longer lives. Our Sun s lifespan is about 10 Billion years. Our sun has existed for about 5 Billion years. Towards the end of a star s life on the Main Sequence, the core stops fusing Hydrogen to Helium in the core and the core collapses. A medium mass to low mass star will leave the Main Sequence and become a Red Giant. A large mass star will become a Super Red Giant star.

7 All Red Giant and Super Red Giant stars have increased luminosity and cooler surface temperatures (brighter and cooler). Red and Super Red Giants then enter the Variable stage where the stars begin to collapse further. After the Variable stage of a Medium to Low Mass Star, the outer shell forms a Planetary Nebula around a hot, smaller and less luminous star called a White Dwarf. White Dwarfs are about the size of our Earth but still have a mass near the original Main Sequence star. Eventually the White Dwarf will dim and become a Black Dwarf. After the Variable stage of a Large Mass star, a tremendous explosion occurs resulting in a Supernova and a surrounding nebula, rich in heavy elements and capable of contracting to form a new star and planetary solar system. Astronomers believe that this process formed the development of our Sun and Planets. The Supernova can contract even further and turn into a highly magnetic, fast spinning star called a Neutron star. The Neutron star can further develop into a Pulsar which is a pulsating spinning star. After a Supernova, some super massive stars collapse so much that they form an invisible Black Hole. A Black Hole s gravitational inward pull is so great that its light and radiation cannot escape. Astronomers have even detected some Black Holes masses that are billions of times the Sun s mass.

8 Sunspots Supernova Telescope Tides A dark area of gas on the Sun s surface that is cooler than the surrounding surface. Sunspots often occur in an 11 year cycle. The beginning of the cycle starts with the year that has the fewest number sunspots (solar minimum). About 5.5 years later after solar minimum, sunspots occur in the largest numbers (solar maximum). After solar maximum, about 5.5 years later solar minimum occurs again. Sunspots often occur in pairs where solar prominences form and Coronal Mass Ejections (CME) or Solar Flares eject from the surface of the Sun. By observing sunspots, astronomers determined that the Sun rotates on its axis is a Solar Maximum year. The brilliant explosion of a dying supergiant star. A device built to observe distant objects by making them appear closer. The periodic rise and fall of the level of water in the ocean. Tides are caused primarily by the Moon s gravitational pull on us and secondarily by the Sun s (New Moon) gravitational pull.

9 Tides (cont.) The Highest high tides and lowest low tides occur during the New and Full Moon Lunar Phases (Spring Tides). Neap Tides (1 st and Last Quarter) are not as great. White Dwarf The blue-white hot core of a dying medium mass star that is left behind after its outer layers (planetary nebula)have expanded and drifted out into space.