Astr 102 Final Flashcards
Retrograde motion is ___ while prograde motion is ___
the apparent backward motion of planets with respect to fixed stars. Prograde motion is the apparent forward motion of the planets from respect to fixed stars.
Aristotle determined ___
The SHape of the Earth
Aristarchus deduced ___
Deduced the relative size and distances of the Earth, the Moon, and the Sun.
Eratosthenes was the first person to ___
get a rough estimation as to the size of the Earth by measuring the distance between two cities from word of mouth. His estimate was in fact to large though.
Hipparchus ___
Revised the findings of Aristarchus, and discovered that the Earth experiences precession.
Ptolemy developed the ___
Ptolemaic model which is the geocentric model using epicycles to explain retrograde motion.
Copernicus is the one who developed the ___
Heliocentric model.
Tycho Brahe’s contribution to astronomy was ___
to observe the stars and made nightly observations for 25 years. He also hired Johannes Kepler.
Johannes Kepler’s astronomical contributions were ___
Kepler’s three laws of planetary motion.
Galileo made many contributions but five were very notable. What Were they?
Made many discoveries such as discovering Venus went through phases like the moon, discovered Jupiter’s moons, he discovered the moon was not perfect and similar imperfections to Earth, he discovered the Milky Way which was made up of countless stars, when observing the Sun he discovered imperfections known now as Sun Spots which also proved the moon wasn’t a perfect sphere like the moon.
Describe how one would measure the size of the Earth.
Measure the difference in the lengths of shadows in two different cities.
List and describe each of Kepler’s 3 laws.
- Planets orbit the Sun in elliptical orbits.
- The speed of a planet varies inversely with its distance to the Sun.
- A planet’s orbital period is related to its distance from the Sun. (P2-a3).
Describe how astronomers can use light to determine temperature. What would astronomers find if two stars had the same temperature?
Astronomers would look at the intensity of light as a function of wavelength. The position of the peak {towards the short-
wavelength – or blue end for high temperature} can be used to determine the temperature.
What is the photosphere? What is the photosphere considered to be? What is its approximate temperature?
The photosphere is the bottom-most layer considered to be the surface of the Sun. the temperature is 4,500 - 6,000 K.
What are sunspots and why do they occur? What is the temperature like in sunspots? What is the primary force for sunspots?
Sunspots are magnetically active regions of the sun whose temperature is less than the rest of the photosphere. The primary force of sunspots is magnetism.
How long does a single sunspot last? How long do sunspot cycles last?
A single sunspot can last between hours and months. The sunspot cycle is 11 years.
. Does the sun rotate? If so, describe its rotation.
The Sun does rotate. However, it is not a solid mass and thus, the poles rotate slower than the equator.
How do electrons produce light? What does electron quantization refer to?
As electrons transition from an outer to an inner orbital, it releases energy. Quantization refers to the electrons absorbing or emitting only specific amounts of energy.
Describe what an emission spectrum is and discuss why it is different than an
absorption spectrum.
An emission spectrum is a continuous black constant background with strips of color running through it, whereas an absorption background is a continuous bright background with dark lines running through it.
How can astronomers determine the direction and speed of a star?
As astronomers collect the spectra of stars, they observe the position of spectral lines. Should the lines be blue shifted, that would indicate that the stars are moving towards us. If the lines are shifted to the red end of the spectrum that would indicate that the star is moving away from us. The greater the shift, the faster the speed.
What is one significant discovery binary stars allows us to make?
Binary stars help allow us to determine the mass of stars
What is the Hertzsprung-Russel Diagram? What is the significance of the HR diagram?
It’s a diagram that is a plot of the brightness of stars as a function of their temperature. It also shows that stars fall naturally onto certain areas. )
What does the magnitude and luminosity of stars mean? How are they similar?
How are they different?
Magnitude refers to brightness, while luminosity refers to energy. They are both measures of light.
What do apparent and absolute mean? How do those terms relate to magnitude and luminosity?
apparent means evident from a certain position or view. Absolute means the actual truth regardless of perspective. In terms of luminosity and magnitude, absolute luminosity and magnitude is the intrinsic amount they release, the apparent magnitude and luminosity is what we view here on Earth.
