Astro Exam 1 Study Guide

Telescopes above Earth's atmosphere are better because:

-certain kinds of radiation cannot get through atmosphere all the way to the surface (X-ray, gamma-ray, UV, IR) -conditions give clearer images without atmospheric blurring

Meteors

A bright streak of light that results when a meteoroid burns up in Earth's atmosphere

Kepler's Second Law

A line joining a planet and its star sweeps out equal areas during intervals of time. OR, a planet's speed is fastest when the planet is closest to the sun (perihelion) and slowest when its farthest away (aphelion)

An "onion skin" shell burning structure, with elements up to iron being produced, develops in:

A star much more massive than the sun

Speed of light

All forms of radiation travel at:

Newton's First Law

Any object at rest, or in motion in a straight line will remain in that state unless acted upon by a force

What is at the center of the planetary nebula?

Both the core of the dying star and something that will eventually become a white dwarf

Venus

Closest planet to earth

What factor is not in the Drake equation?

Communication lag due to large distances between stars

When does winter begin?

Dec. 21 - nights longer than days in northern hemisphere

What is a lunar eclipse?

Earth's shadow passes across the moon

How does the sun appear to move in the sky in the course of the day?

East to West because of the Earth's rotation. The stars and planets move in the same way from our point of view, also because of the Earth's rotation

Greenhouse effect

Energy from Sun heats Earth. Earth's surface radiates this heat back towards space by giving off infrared radiation.

A star that is twice the mass of our sun would have a habitable zone that:

Includes Mars but not Earth

What happens to the moon in one month?

It moves around the Earth once

What happens to the Earth in one year?

It orbits the sun once (one complete revolution)

What does not happen when an object approaches a black hole?

It quickly gets sucked in even from a large distance

When does summer begin?

June 21 - days longer than nights in the north

When does spring being?

Mar. 21 - days and nights have equal length

What eclipses of the moons of Mars?

Mars has two tiny moons, Phobos and Deimos. Relative to Earth's moon, they are tiny and closer to their planet and orbiting faster - and closer to the orbital plane of mars around the Sn. This leads to more frequent eclipses visible from Mars

How can we measure the mass of a black hole?

Measure the speed of the orbit of a star in a binary system with the black hole

What is the order of the phases of the moon?

New - Waxing Crescent - First Quarter - Waxing Gibbous - Full - Waning Gibbous - Third Quarter - Waning Crescent - New (repeat)

When does fall begin?

September 21 - days and nights equal length

how are the Sun, Earth and Moon positioned when it is full moon?

Sun - Earth - Moon

How are the sun, earth, and moon positioned when it is a lunar eclipse, and what phase is the moon in?

Sun - Earth - Moon (full moon)

how are the sun, earth, and moon positioned when it is a solar eclipse?

Sun - Moon -Earth (new moon)

Newton's Universal Law of Gravitation

The force of gravity between two point masses (every mass attracts other masses). More mass = stronger gravity

What is a solar eclipes

The moon is blocking the Sun's light or a location on the earth's surface is passing under the moon's shadow

Why do eclipses not occur every month on earth?

The moon orbits the earth in a slightly different plane than the earth orbits the sun

What does the Drake equation estimate?

The number of technological civilizations in the Milky Way

Kepler's First Law

The planets orbit the sun in elliptical orbits with the sun at one focus. These ellipses tend to be nearly circular for the planets in our solar system

What causes the phases of the moon?

The sun is lighting up different fractions of the part of the moon we see from earth

Why do we have seasons?

The tilt of the Earth's axis of rotation, with respect to the plane of its orbit around the Sun (and not because of changing distance from Sun) The Earth's tilt is about 23 degrees.

How do solar sized and smaller stars die? About how large are their remnants?

They become white dwarfs about the size of earth

Photon

a particle of light

ROYGBIV

an acronym for the spectrum of light

Aurora

an atmospheric phenomenon consisting of bands of light caused by charged solar particles following the earth's magnetic lines of force

Comets

balls of ice, rock, and dust in space with a tail

maria (Latin for "seas")

dark-colored, less cratered, valleys; geologically younger; filled by lava 1 to 4 billion years ago

wavelengths of X-rays

even smaller (nm)

Newton's Third Law

for every action, there is an equal and opposite reaction

Forms of light (from high energy to low energy)

gamma ray > xray > ultraviolet (UV) > visible > infrared (IR) > microwave > radio

impact craters

gouged out from explosions, asteroids or comets that hit the moon

High-energy light

high frequency, low/short wavelength, bluer color

Low-energy light

high/long wavelength, redder color

Blackbody spectrum

higher temperature = more light in total, and a peak intensity at a shorter wavelength (or at a bluer color)

A star that is 75% of the mass of our sun would have a habitable zone that is:

includes Venus only

Telescopes above Earth's atmosphere are worse because:

it is hard (and expensive) to get a very large light-collecting area launched into space

Continuum spectrum

light at all wavelengths

Important qualities of telescopes

light gathering power, angular resolution, and the quality of the instruments, magnification not so important

terra (Latin for "land")

light-colored features, heavily-cratered, high peaks; geologically older; highlands uplifted from impacts in early solar system

What is the main requirement for a habitable zone?

liquid water

wavelengths of radio waves

meters and centimeters

Asteroids

objects revolving around the sun that are too small and too numerous to be considered planets. Remains from the solar system formation

When is the full moon visible?

only at night. It transits (is highest in the sky, overhead) at midnight; the full moon rises 6 hours earlier and sets 6 hours later (at sunrise)

Kepler's Third Law

p^2=a^3, where P = orbital period (a planet's year, given as a multiple of earth years), a= the semimajor axis (average distance from Sun, given in AU)

Regorith

powdery dust and rocky debris that covers the Moon; broken apart by small meteorites hitting moon continuously

Emission line

produced when electrons from higher to lower energy levels, and emit photons of those specific energies

Absorption line

produced when the electrons in atoms absorb photons and remove light of specific energies from the spectrum. Then the electrons more from a lower to a higher energy level

300 degrees Kelvin

room temperature; a blackbody at room temperature peaks in the infrared (IR) region of light

What causes day and night?

rotation of the earth on its axis

Absorption spectrum

shows absorption lines - dark lines in the spectrum at certain wavelengths, superimposed on a continuum spectrum -produced by a less energetic gas cloud in front of a light source

Emission spectrum

shows emission lines - bright lines at specific wavelengths, in an otherwise empty (dark) spectrum, due to emission of photons from atoms in gas that have electrons in elevated levels (ex: excited gas)

Properties of light:

some properties of a wave and some of a particle

Prism of light:

splits light into different colors by bending different wavelengths by different angles

Light gathering power:

telescopes collect light in proportion to the area of their mirrors

wavelengths of visible light

ten billionths of a meter

angular resolution

the ability to distinguish or separate two nearby light sources (with good angular resolution). The earth's atmosphere limits angular resolution

Newton's Second Law

the acceleration of a body due to a force will be in the same direction as the force, with the magnitude directly proportional to mass. F=ma

When is the new moon visible?

the new moon is visible during the day. It transits at noon; it rises 6 hours earlier (at sunrise) and sets 6 hours later (at sunset)

g=M/R^2

the strength of gravity, on the surface of a planet

5800 degrees kelvin

the sun's surface temperature. Its spectrum peaks in the visible light region (peak around green - a green star)

refracting telescope

use a lens to collect and focus light

Relecting telescopes

use a mirror to collect and focus light

What kinds of radiation get through the Earth's atmosphere?

visible and radio

What season is it in the Southern hemisphere when it is summer in the northern hemisphere?

winter

How is the Earth's axis tilted when we have summer in the Northern hemisphere?

with the pole toward the sun

Magnification

zooms in on a smaller portion of the sky, to see more detail (but also observes a smaller overall area of the sky)