Midterm Study Guide for Astronomy 101

Cosmos – an alternative name for the universe
Meridian – a half circle extending from your horizon (altitude 0) due south through your zenith to your horizon due north. Zenith – the point directly overhead, which has an altitude of 90 degrees.
Latitude –The angular north-south distance between Earth’s equator and a location on Earth’s surface.
Longitude – The angular east-west distance between the prime meridian (which passes through Greenwich) and a location on Earth’s surface.
Speed – The rate at which an object moves. Its units are distance divided by time, such as m/s or km/hr. Velocity – The combination of speed and direction of motion; it can be stated as a speed in a particular direction, such as 100 km/hr due north.
Force – Anything that can cause a change in momentum.
Momentum – The product of an object’s mass and velocity.
Acceleration – The rate at which an object’s velocity changes. Its standard units are m/s squared.
Kinetic energy - Energy in motion, given by the formula (1/2)m * v squared.
Gravitational potential energy - Energy that an object has by virtue of its position in a gravitational field; an object has more gravitational potential energy when it has a greater distance that it can potentially fall.
Power – The rate of energy usage, usually measured in watts (1 watt = 1 joule/s).
Wavelength - The distance between adjacent peaks (or troughs) of a wave.
Frequency – The rate at which peaks of a wace pass by a point, measured in units of 1/s often called cycles per second or hertz. Redshift – (Doppler) A Doppler shift in which spectral features are shirted to longer wavelengths, observed when an object is moving away from the observer.
Focal plane – The place where an image created by a lens or mirror is in focus.
Light pollution – Human made light that hinders astronomical observations. Terrestrial planet - Rocky planets similar in overall composition to Earth. Jovian planet – Giant gaseous planets similar in overall composition to Jupiter. Kuiper Belt – The comet- rich region of our solar system that spans distances of about 30-100 AU from the Sun. Kuiper belt comets have orbits that lie fairly close to the plane of planetary orbits and travel around the sun in the same direction as the planets.
Oort Cloud – A huge, spherical region centered on the Sun, extending perhaps halfway to the nearest stars, in which trilliuons of comets orbit the Sun with random inclinations, orbital directions, and eccentricities. Orbital energy – The sum of an orbiting object’s kinetic and gravitational potential energies. Spectrograph – An instrument used to record spectra. Photons – An individual particle of light, characterized by a wavelength and a frequency
. Ptolemy is credited with being the person who computed the most authoritative tables for calculating the past present and future position of the planets. His tables were the most authoritative throughout the middle ages
. Ptolomy's view of the universe was an earth centred universe with the planets orbiting in spheres but also spheres within spheres which made his model more useful than the preceding models
. Galileo gave credence to Copernicus's claims that the Sun was the center of the universe, not the Earth. He also perfected the USE of the telescope, he DID NOT invent it. With his telescope, he observed sun spots, proved that the Moon had mountains and craters, discovered the four moons of Jupiter, and that Venus goes through phases. Copernicus was an astronomer who stated that the sun was at the center of our solar system and that the planets rotated around it. Up until that time it was commonly believed that the planets, and the sun, rotated around the Earth. He wasn't the first, but was definitely the most famous for it. He also worked to develop better telescopes during the course of his studies. Brahe 1) Observing and measuring the (rough) distance to a supernova, establishing novae as outside the solar system. This proved that the "stellar firmament" was not a God-given stable sphere, but a dynamic system. Brahe made these observations around 1572. 2) Making the most accurate measurements of planetary positions available at that time, and for a long time thereafter. Brahe's data was used by Kepler to develop his laws of planetary motion, determining that the Earth had an elliptical orbit around the Sun.
Kepler contributed a mathematical law of motion to astronomy. Kepler's three laws are: 1) The orbit of every planet is an ellipse with the sun at one of the foci. An ellipse is characterized by its two focal points; see illustration. Thus, Kepler rejected the ancient Aristotelean and Ptolemaic and Copernican belief in circular motion. 2) A line joining a planet and the sun sweeps out equal areas during equal intervals of time as the planet travels along its orbit. This means that the planet travels faster while close to the sun and slows down when it is farther from the sun. With his law, Kepler destroyed the Aristotelean astronomical theory that planets have uniform velocity. 3) The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axes (the "half-length" of the ellipse) of their orbits. This means not only that larger orbits have longer periods, but also that the speed of a planet in a larger orbit is lower than in a smaller orbit.
Questions: categories of electromagnetic radiation according to wavelength Gamma Rays-wavelength: 0.01 nm X-rays -1 nm Ultra-violet Rays-0.1 micrometres Visible Light- Red light: 0.7 micrometres Violet Light: 0.4 micrometres Infrared Radiation- 0.01 mm Microwaves-less than 10 cm, usually 1cm Radiowaves- Long, Medium and Short Waves:2km-10m Very High Frequency (VHF) and Ultra High Frequency (UHF): 10m-10cm What is the difference between refracting and reflecting telescopes? Refractors use lenses while reflectors use mirrors.
Why do stars twinkle? turbulence in the Earth's atmosphere.
In what sense are we “star stuff”? Nearly every atom from which we are made was once inside of a star.
How old is the solar system, relative to the universe? It is about one-third the age of the universe.
How do we know the universe is expanding? be moving away from us, with more distant ones moving faster
. When did we learn that the Earth is not the center of the universe? Within the past 500 years.
Why does the Earth have seasons? The tilt of the earth on its axis.
What is the length of time between new moon and full moon? 14.5 days.
When do lunar eclipses occur? full moon.
How do modern astronomers view astrology? Astrology played an important part in the development of astronomy in ancient times.
Why does the Earth have tides? Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the Earth.
What are the advantages of telescopes over eyes? Telescopes can collect far more light with far better angular resolution.