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PHYS295 Final
Final Exam study
| Question | Answer |
|---|---|
| How often are large asteroids likely to collide with Earth? | Once every 100,000 to 1 million years. |
| What kind of asteroids provide a more likely threat of colliding with Earth? | Near-Earth asteroids that sit in an asteroid belt just outside of Earth's orbit. |
| What are the names of 4 classes of near-Earth asteroids that present an impact threat? | Amors, Atens, Apollos, and Atiras. |
| What is the difference between comets and asteroids? | Asteroids are made of rocky material and usually exist in the asteroid belt, whereas comets are made up of icy and dusty material and orbit the sun causing a trail of material to melt and fly off behind them. |
| What causes meteorite showers? | When Earth collides with the debris that has melted and flown off of comets that are orbiting the sun. |
| What are the names of the 3 asteroids that had big impacts with Earth? | Tunguska, Chelyabinsk and Chicxulub (AKA dinosaur killer). |
| Why were no craters found after the asteroid Tunguska collided with Earth in 1908? | It is believed that the asteroid exploded high up in Earth's atmosphere, not colliding with the ground, but still causing devastating impacts below in Siberia, Russia and causing cooler temperatures across the globe. |
| How big was Tunguska? | About 80m in diameter. |
| How fast was Tunguska travelling when it collided with Earth? | About 22km/s. |
| How big was Cheylabinsk? | About 20m in diameter. |
| How fast was Cheylabinsk travelling when it collided with Earth? | About 19km/s. |
| How big was the dinosaur killer? | Estimated to be 10-15m in diameter. |
| How many craters have been found in Australia? | Over 19. |
| How does the atmosphere cause scattering of light? | Atmospheric particles block specific regions of the electromagnetic spectrum and redirect the path of the light. |
| What types of telescopes do they use in space to avoid atmospheric blocking? | Gamma/X-ray, ultraviolet, visible, infrared and possibly radio telescopes. |
| What is parallax? | The apparent shift in position of an object when viewed from different angles. |
| What is the parallax phenomenon used for in astronomy? | The parallax angle is used to calculate the distance to objects in space (such as the moon and the sun). |
| What is the approximate distance to the sun from Earth? | 150 million km. |
| What is the approximate distance to the moon from Earth? | 384,000km. |
| What are photometers? | Instruments that measure the intensity of light. |
| What is luminosity? | The amount of energy emitted by a source per second. |
| What is the difference between apparent magnitude and absolute magnitude? | Apparent magnitude measures the brightness of a celestial object from the position of the observer, absolute magnitude measures an object's real, intrinsic brightness by the apparent magnitude if placed at a standard distance. |
| What is a blackbody? | A body that absorbs all the incident light upon it, reflects none, but radiates the absorbed light-energy in some characteristic spectra. |
| What is an example of a blackbody? | Earth (and other planets). |
| How are wavelength and temperature of a blackbody related through Wein's law? | They are inversely proportional. |
| What are spectroscopes/spectographs? | An instrument that analyses light by splitting electromagnetic radiation into component wavelengths. |
| What are emission spectra? | They show bright coloured lines on a dark background when hot gas emits light. |
| What are absorption spectra? | They show dark missing lines on a continuous rainbow background when light passes through a cool gas. |
| What are the spectral classes (ordered relative to how hot they are)? | OBAFGKM |
| How are luminosity and distance (squared) related? | They are inversely proportional? |
| How are luminosity and the radius of a star (squared) related? | They are directly proportional. |
| What can observing stellar spectra from stars belonging to the same spectral class at different luminosities show? | Different atmospheric conditions. |
| What type of star is the Sun? | G2V. |
| Who developed the stellar luminosity classes? | W. W. Morgan and P. C. Keenan. |
| How do we determine the mass of stars? | Through spectroscopy and measuring the doppler shift of the stellar spectrum. |
| What is the doppler shift? | The change in frequency or wavelength of a light wave in relation to an observer who is moving relative to the source of light. |
| How does the Doppler Effect work? | As the observer moves away from the source of light the wavelengths lengthen (redshifted), and as the observer moves towards the source of light the wavelengths shorten (blueshifted). |
| What do most stars exist in? | Systems of 2 or more stars (i.e. binary systems, trinary systems, etc.). |
| Which has smaller wavelength, blue light or red light? | Blue light. |
| What does Kepler's 3rd Law state? | The orbital time T and orbital radius r are related by T^2 being directly proportional to r^3. |
Created by:
Knerdy