Stars & Universe Test 1

Due tonight at 11pm

Newton's First 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.

Newton's Second Law

The acceleration of a body due to a force will be in the same direction as the force, with a magnitude inversely proportional to its mass.

Newton's Third Law

For every action, there is an equal and opposite reaction.

g = M / R ^2

The strength of gravity, g, on the surface of a planet is given this equation. M is the mass of the planet and R is its radius.

More mass

More gravity

Less separation

Less gravity; if the radius of a planet were twice that of another, the gravity is 1/4 as strong.

Newton's Law of Gravitation

The force of gravity is proportional to (mass of object 1) × (mass of object 2) divided by the distance between the two objects squared

When do new seasons start?

The 21st day of March, June, September, and December

Why do we have seasons?

Earth's axis of 23 degrees causes certain hemisphere to experience different weather throughout the year.

What direction does the Sun appear to move in?

East to West, just like the stars and planets.

Moon phase order

New - Waxing Crescent - First Quarter - Waxing Gibbous - Full -- Waning Gibbous - Third Quarter - Waning Crescent - New

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).

Position during a New Moon or Solar Eclipse.

Sun — Moon — Earth

Positions during a Full Moon or Lunar Eclipse.

Sun — Earth — Moon

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.

Lunar Eclipse

Earth's shadow passes across the Moon.

Mars moon (Phobos and Deimos) eclipses

Similar to Earth's in terms of positioning, but because of the faster orbit and closer distance, eclipses happen more often.

Constellation

Large defined areas of the sky, with anything within those areas considered as a part of it.. 88 in total

Why can't we see certain stars or constellations all the time?

Stars in the same constellation are likely to be at very different distances from us; Different constellations are visible at different times of year, because Earth is facing different parts of space during its orbit.

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.

Zodiac constellations

The 12 (or 13) constellations that lie along the ecliptic; Virgo, Aries, Sagittarius, etc.

Sun's relationship with Zodiac constellations

Resides in a Zodiac constellation at all times, one per month every year. You can't see that constellation in that time since it is behind the Sun all day, and not on the nighttime side of Earth. The Sun is in your Zodiac "sign" month. To see it you must wait until night 6 months from your birthday.

Light

Has some properties of a wave and other properties of a particle. A particle of this is called a photon.

Forms of light ranked from highest to lowest energy

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

Bluer color light

high-energy light = high frequency = low / short wavelength

Redder color light

low-energy light = low frequency = high / long wavelength = a redder color

What radiation gets through Earth's atmosphere?

Visible and radio waves. A telescope is needed to see other radiation

Blackbody Spectrum

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

What do all forms of radiation travel at?

the speed of light

Prism

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

Sun's surface temperature

about 5800 degrees Kelvin. Its spectrum peaks in the visible light region (peak around green — a "green star"!)

Room temperature

about 300 degrees Kelvin; a "blackbody" at this temperature peaks in the infrared (IR) region of light.

Continuum spectrum

Light at all wavelengths

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 electrons move from a lower to a higher energy level

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 (i.e., an "excited" gas)

Why does each chemical element have its own spectral fingerprint?

Different chemical elements have different energy levels that their electrons can occupy, and thus give rise to different placements and patterns of lines in their spectra

Reflecting Telescopes

use a mirror to collect and focus light

Refracting Telescopes

use a lens to collect and focus light

Important qualities of telescopes

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

Light-gathering power

Telescopes collect light in proportion to the area of their mirrors; The area of circle is proportional to its diameter squared.

Angular resolution

the ability to distinguish or separate two nearby light sources

Why do stars appear to twinkle in telescopes?

Earth's atmosphere limits angular resolution, or "seeing," for ground-based telescopes

Magnification

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 space telescopes better than Earth ones?

There's no atmospheric blurring or certain rays like gamma or x-rays being blocked out. The drawback is that it's difficult and expensive for big light-collecting area to be launched into space