Astro 7N Unit 2 Flashcards
Who proposed the Sun-Centered (Heliocentric) Model of the Universe?
Copernicus
What is the distance between the Earth and the Sun?
1 “Astronomical Unit”
How long does it take for the Earth to orbit the Sun?
1 year
What is Keplers 1st Law?
The planets orbit the Sun in elliptical orbits with the Sun at one focus
What is Keplers 2nd Law?
a planet’s speed is fastest when the planet is closest to the Sun (at a point called perihelion), and slowest when it is farthest away (aphelion)
What is Keplers 3rd Law?
P^2 = a^3
, where P is the orbital period (a planet’s year, given as a multiple
of Earth years) and a is the semimajor axis (average distance from Sun, given in AU)
What is an Aurora?
solar wind particles hit atmospheric gas and lead to emission of different colors;
What is the Greenhouse Effect?
Energy from Sun heats Earth. Earth’s surface radiates this heat back towards space by giving off infrared radiation
What is the Kuiper Belt?
disk-shaped region beyond Neptune, ranges 30 – 55 AU, contains several dwarf planets
What is the Oort Cloud?
houses long-period comets, out beyond the Kuiper belt
What are the three criteria for an object to be considered a planet?
- orbit the Sun (not be a moon around another object);
- be massive enough to be nearly round;
- clear the region around its orbit (Pluto does not; many other objects there)
The Formation of the Solar System…
- the Solar System formed 4.5 billion years ago
- starting with cloud of gas and dust, it collapses due to its own gravity
- as it collapses, the spinning cloud flattens and forms a disk
- the Sun forms at center
- “lumps” in the disk become planets
- the regions around these proto-planetary clumps clear out (or material is absorbed)
- only rocks and metals survive in inner region; outside, ices and gases also survive
- takes a few tens of millions of years to form 11
What is the order of the planets going outward from the Sun?
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
Describe Comets
- A few kilometers in size
- Tails pointing away from the Sun develop due to the solar wind
- Made of ice (both water ice and “dry ice”) and dust — remnants of Solar System formation
Describe Asteroids
- rocks left over when the planets formed
- many are in the “Asteroid Belt” between Mars and Jupiter
Describe Meteors
- streak across the sky very quickly — they are also called “shooting / falling stars”
- most meteors are tiny dust particles or grains — less than a centimeter in size — that rapidly burn up in Earth’s atmosphere;
Describe Mercury
grayish color, craters, similar to Earth’s moon, but does not have prominent maria, the dark “seas,” like the Moon does
Describe Venus
Bright, yellowish, and cloud-covered (no sharp surface features visible). A clue that this is not a gas giant is that it does not have rings, which all gas giants (aka “Jovian planets”) in our Solar System have
Describe Earths Moon, Luna
Grayish and cratered, and with distinctive large dark maria, the
remains of old lava flows that covered large patches of its surface
Describe Mars
Mars is the color of rust, whitish ice caps at its poles, many craters, some prominent old volcanoes, some large valleys, but no significant surface water
Describe Vesta, an asteroid
non spherical
Describe Jupiter
Distinctive stormy stripes, cloud bands in different colors (red or brown, to white or even blue-ish). Also has the Great Red Spot, an Earth-sized circular storm in its southern hemisphere.
Describe Saturn
Large ring system. Central planet tan-colored and has long-stretched cloud bands, but less color contrast between them as on Jupiter
Describe Titan, Saturn’s Moon
Saturated orange color (as opposed to Venus’ pale yellow).
Complete cloud cover; cannot see sharp surface features. Like with Venus, the lack of rings is a hint to help not mistake this for a gas giant.
Describe Uranus
Distinctive deep blue-green color. Generally few visible cloud features. A wide ring system, but the individual rings are very dark and thin, with clear gaps between them (compare to Saturn’s). Also, it is tipped nearly on its side, compared to other planets
Describe Neptune
Dark and deep blue in color. A few visible dark storm and cloud features. A smaller ring system than Uranus, with just a few thin dark rings
Describe Pluto
a tiny “icy dwarf,” it orbits the center of gravity of its system with the proportionally-large moon, Charon
