astro 7n exam 1

What is Newtons 1st law

An object at rest, or in motion in a straight line at a constant speed, will remain in that state unless acted upon by a force.

What is Newtons 2nd law

F=ma

What is Newton 3rd law

For every action, there is an equal and opposite reaction. (sun exerts a force on the planets, the planets exert an equal force on the sun)

What is the equation for the stregth of gravity on the surface of a planet

G= M/R^2

If you have more mass

there will be more gravity

If there is a larger distance between planets

there will be less gravity

if Mars has 1/10 the mass of the Earth and 1/2 the radius of Earth, calulate the gravity on the surface of mars in comparison to earth

g = (1/10) / (1/2) 2 = (1/10) / (1/4) = 4/10

mars has 4/10 the surface gravity

Newton’s Universal Law of Gravitation gives

the force of gravity between any two objects in the Universe.

Newton’s Universal Law of Gravitation is

F = G(m1 m2) / r^2

What causes day and night?

Rotation of the Earth on its axis.

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

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

What happens to the Earth in one year?

It orbits the Sun, once (also referred to as one complete revolution about the Sun).

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

With the North pole toward the Sun.

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

Winter

When does winter begin in the Northern Hemisphere

on or about Dec. 21, the nights are longer than days

When does spring begin?

March 21, days and nights are equal

When does summer begin?

June 21, days are longer then nights in the north

When does fall begin

September 21, days and nights are equal

Would seasons happen if earths axis was not tilted?

No

What happens to the moon in 1 month?

it moves once around the Earth.

What causes the phases of the Moon?

The Sun is lighting up different fractions of the part of the Moon we see from Earth.

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

When is the full moon visible?

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

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).

How are the Sun, Earth, and Moon positioned when it is new Moon?

Sun — Moon — Earth

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

Sun — Earth — Moon

What is a solar eclipse?

The Moon is blocking the Sun’s light, or a location on the Earth’s surface is passing under the Moon’s shadow.

How are the Sun, Earth, and Moon positioned when it is a solar eclipse?

Sun — Moon — Earth (as in a new Moon).

What is a lunar eclipse?

Earth’s shadow passes across the 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 (as in a full Moon).

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 about eclipses of the moons of Mars?

Mars has two small 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 Sun. This leads to more frequent eclipses visible from Mars.

What is a Constellation?

large defined areas of the sky (like states in a map of a country) anything visibly within that region is considered "in" that constellation (there are 88 of them, in all (dividing up the total celestial sphere))

Stars in the same constellation are likely to be…

at very different distances from us. Not necessarily close to each other, though they appear close projected on our sky.

Are different constellation visible at different times? what is and example?

yes, "Orion the Hunter" is prominent in the Winter — because as the Earth travels around the Sun, its nightime side faces different regions of space.

What is an ecliptic?

the apparent path of the Sun over the course of a year, with respect to the distant stars — also refers to the plane in which the Earth orbits the Sun.

How many zodiac constellations are there? where do they lie?

the 12 (or 13) constellations that lie along the ecliptic.

is the sun inside a zodiac at all times?

yes, in each one for about a month, each year.

Can you see the zodiac constellation that the sun is in?

No, it is behind the Sun all day and not on the nighttime side of Earth.

Can you see your zodiac constellation on your birthday?

No, it is behind the sun, you have to wait 6 months

Winter zodiacs constellations…

ones opposite the Sun in the winter

Summer Zodiac constellations…

ones opposite the Sun in the summer

What does light behave like

a wave and a particle

What is a particle of light called?

Photon

List the forms of light from high to low energy

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

What does high energy light mean?

High frequency, short wavelength, bluer color

What does low energy light mean

low frequency, long wavelength, a redder color

What do all forms of radiation travel at?

the speed of light

What are radio waves measuered in

meters and centimeters

What is visible light measuered in

ten-billionths of a meter (hundreds of nanometers)

What are x-rays usually measuered in

nanometers down to picometers

What do prisms do?

split light into different colors by bending different wavelengths by \n different angles.

Blackbody radiation is

energy radiated by an object

In the Blackbody spectrum, a higher temperature means

more light in total and a peak intensity at a shorter wavelength

In blackbody radiation the sun is

5800 degrees kelvin, this peaks in the visible light region (peaks at green)

What is room temperature in blackbody radiation

room temp. is about 300 degrees kelvin, peaking in the infrared region

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

visible and radio, To see other kinds of light you would need a telescope that is in space

What are continuum spectrum

light at all wavelengths

What is an 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

how is an absorption line produced

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

What is an emmison 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 (i.e., an "excited" gas)

how is an emmsion line produced?

electrons jump from higher to lower energy levels, and emit photons of those specific energies.

what do different chemicals have?

different energy levels that their electrons can occupy, and thus give rise to different placements and patterns of lines in their spectra; in other words, each chemical element has its own spectral fingerprint.

What do reflectiong telescopes use

a mirror to collect and focus light

What do refracting telescopes use?

a lens to collect and focus light

What are important qualities of a telescope?

light-gathering power, angular resolution, and the quality of the instruments. The magnification is not so important.

what do telescopes collect light in proportion too?

area of their mirrors (proportional to diameter squared)

A 2m diameter telescop collects how much light compared to a 1 m

a 2m-diameter telescope collects 2 x 2 = 4 times as much light as a 1m-diameter telescope (1 x 1 = 1) or, a a 2m-diameter telescope collects the same amount of light as a 1m-diameter telescope in 1/4 the time

What is angular resolution

the ability to distinguish or separate two nearby light sources (with good angular resolution)

What does earths atmosphere do to angular resolution

limits it, makes stars twinkle

what dose magnification do?

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

Why are telescopes above earths atmosphere better?

\-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; i.e., better seeing

What is an issue with telescopes above earths atmosphere?

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

who proposed the sun centered modle of the universe

Copernicus

What is 1 au

the distance between the earth and the sun

What is keplers first law

planets orbit the sun in elliptical orbits with the sun at one focus, the eclipses tend to be nearly circular

What is keplers second law

planets speed is faster when the planet is closer to the sun

what is keplers 3rd law

P^2 = a^3, where P is the orbital period (a planet's year, given as a mulitple of Earth years) and a is the semimajor axis (average distance from Sun, given in AU).

A hypothetical planet takes 3 years to orbit the Sun. How far from the Sun does it orbit?

3 years is the period ("P"). Calculate P^2 = 9 \\n So, from P^2 = a^3 : a^3 = 9.

a= cubed root 9

a= 2.08

A hypothetical planet orbits the Sun at a distance of 5 AU. How long is its orbital period (i.e., its year)?

a=5

5^3=125

125=p^2

11^2 =121 12^2=144, somewhere between 11 and 12

Mecury is…

closest to the sun, you can only see it when its close to the sun

what is the size of mercury in comparison to earth

Mercury is much smaller than Earth. It is similar to Mars in mass and radius, and only a bit bigger than Earth’s Moon; surface gravity less than on Earth

what is the temperature like on Mercury?

Temperature is extremely high on the day side and extremely low on the night side, due to lack of an atmosphere to distribute heat evenly around the planet (or to retain that heat on the night side)

Does mercury have alot of craters

yes

what relative speed does mercury rotate?

slowly, 59 earth days to rotate

How long is a year on Mercury

88 earth days

does mercury have an atmosphere

no significant atmosphere; the sky appears black (can see in to deep space), even in daytime — except for the exact position of the Sun

What is mercurys average density

5 grams per cubic centimeter, similar to metals and rocks

Where is venus located

it is the second planet from the sun and it is the closest planet to earth

Where is venus visible

in western sky in evenings near the Sun, and in the eastern sky just before sunrise; looks like a very bright star. Also shows phases, like the Moon.

how big is venus?

Just slightly smaller than Earth in mass (82%) and in radius (95%).

how long is a day on venus? how long is a year?

A day is 243 earth days, a year is only 225 earth days

what direction does venus rotate

Venus' rotation is in the opposite direction to its orbit around the Sun — i.e., it rotates clockwise when viewed from above (Earth & most other planets rotate counter-clockwise).

what direction does the sun travel on venus?

west to east (backwords)

What is venus atmosphere like

Dense atmosphere — mostly carbon dioxide — of gases produced by volcanic outgassing, but not dissolved in ocean like on Earth, also sulfuric acid in clouds

What is the temperature like on venus? why?

Venus' surface is very hot (> 700 K, hotter than Mercury), because of the presence of large amounts of greenhouse gases (mostly CO2) in its atmosphere to contain heat.

what is the density of venus

5\.2 grams per cubic centimeter — similar to Mercury — and made of metals/rock

What is the surface of venus like?

Active volcanoes, huge lava flows and channels, some large craters, but small meteors burn up in the thick atmosphere before they can impact to leave small craters.

what is earths atmosphere like

fairly thick atmosphere