Astronomy 201 Flashcards
Chapters 1-5
From the position of Earth inside the Milky Way Galaxy, humans cannot see through to the far rim of the Galaxy with visible light because:
The space between the stars contains interstellar dust.
Which of the following is equal to 1 astronomical unit (AU)?
The average distance between Earth and the Sun
A reason why the International Date Line bends along the line?
To avoid cutting through groups of islands
X-rays coming from space can only be studied above Earth’s atmosphere because:
they are stopped by the large number of atoms in Earth’s atmosphere with which they interact.
Why do the speeds of the planets of the solar system in their orbits around the Sun vary?
Because of their elliptical orbits
Which of the following statements is true about electromagnetic waves?
They do not require a medium in which to travel.
Which of the following is a necessary condition for a celestial body to be deemed a planet?
It must orbit a star.
Which of the following is a limitation of Kepler’s laws?
They do not help us understand what forces of nature influence planetary motion.
Why do electrons get loose from the ground state, deep inside stars?
Because of the heat inside stars
The Local Group is part of a supercluster of galaxies, called the _____, which stretches over a distance of 110 million light-years.
Virgo Supercluster
For an ellipse, the ratio of the distance between the foci to the length of the major axis is called its _____.
Eccentricity
A difference between planets and stars?
Stars have the ability to consistently produce their own light, whereas planets lack this ability.
According to Niels Bohr, how do electrons remain in orbit around the nuclei?
By only following orbits of certain possible sizes
A reason for the appearance of dark bands in absorption spectra?
Absorption of light at certain frequencies by certain elements
Why was Kepler’s discovery of the elliptical shapes of the orbits of planets a decisive moment in the history of human thought?
Because it demonstrated that an acceptable cosmos could contain a more complex shape like an ellipse, instead of having only circles
The temporary apparent westward motion of a planet observed over the course of many nights as Earth passes between it and the Sun is called _____.
Retrograde motion
The ecliptic is the path _____.
The Sun appears to take around the celestial sphere
A reason atoms are not like a miniature solar system?
The typical atom is far emptier than our solar system out to Neptune.
The reason for Earth’s sky being fairly bright at twilight?
The scattering of sunlight by Earth’s atmosphere when the Sun is below the horizon
The difference between a solar day and a sidereal day?
Sidereal day is defined in terms of the rotation period of Earth with respect to the stars, whereas solar day is defined in terms of the rotation period of Earth with respect to the Sun.
What would occur as the eccentricity of an ellipse approaches one?
The ellipse would become flatter.
The speed needed to make a satellite orbit Earth without being drawn in by the planet’s gravity?
8 km/s
Dark matter
It cannot be directly observed, even with the help of instruments.
The similarity between all types of electromagnetic waves?
They all travel at the same speed in a vacuum.