Astronomy Midterm

Waxing Moon

The phase of the Moon after the new Moon and before the full Moon when the lit portion appears to grow larger.

Waning Moon

The phase of the Moon after the full Moon and before the new Moon when the lit portion appears to decrease.

Revolution of the Moon

The motion of the Moon around the Earth.

Rotation of the Moon

The spinning of the Moon about its own axis.

First Quarter

A phase of the Moon where half of the Moon is lit, appearing to observers on Earth as the right side lit.

Third Quarter

A phase of the Moon that follows the full Moon where half of the Moon is lit on the left side as seen from Earth.

Solar Eclipse

An event that occurs when the Moon covers the Sun, either totally or partially, usually during the New Moon phase.

Lunar Eclipse

An event where the Earth's shadow falls on the Moon, either totally or partially, typically during the Full Moon phase.

Eclipses

Astronomical events involving the shadow of one celestial body falling on another; includes both solar and lunar eclipses.

Full Moon

The phase of the Moon when it is fully illuminated as seen from Earth.

Astronomy

scientific study of the planets, stars, galaxies, the universe as a whole

Astronomical Unit (AU)

Average distance from Earth to the Sun. Approximately 150 million kilometers

Massive

Contains mass

Scientific Method

The formal procedure used to test (attempt to falsify) the validity of a scientific hypothesis and theories

Theory

A well developed (group of) ideas tied solidly to known physical laws and make testable predictions about the universe.

Idea

An untested notion about how something might be

Fact

An observation or measurement

Hypothesis

An idea that leads to testable predictions

Law

Series of observations that scientists that can use to make predictions with no explanation of why it occurs

Scientific Principle

A generalization about the universe that guides scientists in the construction of a new hypothesis; not independent of other principles

Light Time Travel

How long it would take for light to travel a given distance. Used do to it being the fastest possible speed, always the same speed, 300,000 kilometers/second

Light Year

The distance that light travels in one year, approximately 9.46 trillion kilometers. It is used to measure astronomical distances.

Big Bang

The leading explanation for the origin of the universe 13.8 billion years ago, suggesting it began as an extremely hot and dense point and has been expanding ever since.

In the beginning only Helium and Hydrogen existed with traces of Lithium, Beryllium, and Boron. These combined to make stars and galaxies, leading to the formation of heavier elements through nuclear fusion in stars.

Satellite

Object in orbit more massive than a body

Nuclear Diffusion (stars)

that emit light and heat due to nuclear fusion in their cores, serving as the building blocks of galaxies.

Nuclear Fusion (stars)

is the process where two light atomic nuclei combine to form a heavier nucleus, releasing energy in the process. It is the reaction that powers stars and produces heavier elements.

Cosmic Location

Universe ,Laniakea Supercluster, Virgo Supercluster, Local Group, Milky Way, Solar System, Earth

Waves

Radio, Microwave, Infared, Visible, Ultra Violet, X-ray, Gamma Ray

Falsified

The ability to be proven wrong

Occam’s Razor

When faced with competition hypothesis that explain all observations equally well, choose the one with the fewest assumptions, the simpler explanation

Cosmological Principle

The testable assumption that the same physical laws that apply here and now also apply everywhere and at all times; there is no special locations or directions in the universe

Zenith

Point directly above the observer in the celestial sphere

Meridian

The line on the celestial sphere that runs from north to south dividing the sky into an eastern half and a western half

Horizon

The line that separates the sky from the ground. Perpendicular to zenith then spin 360 that’s your horizon

Celestial Sphere

Imaginary sphere with celestial objects in its inner surface.

Initially created by the Ancient Greeks

Constellation

Group of stars that seem fixed pattern on the celestial sphere

 

Day

Time it takes Earth to rotate on its axis.

A sidereal day is the time it takes for the Earth to complete one full rotation relative to distant stars, approximately 23 hours and 56 minutes.

A solar day, which is about 24 hours, measures the time from one noon to the next, accounting for Earth's orbit around the Sun.

Apparent Daily Motion

The daily path each object takes across the sky.

Altitude

The location of an object above the horizon or the angle formed between the object and the observer's line of sight, measured in degrees.

Latitude

The angular distance north or south from the equatorial plane of a nearly spherical body

Longitude

The angular distance west or east from the equatorial plane of a nearly spherical body

Circumpolar

Can always be seen from the horizon from a specific location on Earth, appearing to circle around the celestial pole.

Revolve

One object orbits another

Rotate

Spin on an axis

Ecliptic

The annual path of the sun against the stars; this follows the zodiac the 12 constellationsand is the basis for the changing seasons and the positions of celestial objects in the sky.

Summer Solstice

When the north pole is titled towards the sun, the day when the sun is the highest in the sky as it crosses the meridian, the sun rises farthest north of east, sets furthest north of west, marks the first day of summer typically on June 21

Winter Solstice

When the north pole is tilted away from the sun, resulting in the shortest day of the year, typically occurring around December 21.

Equinoxes

Twice a year when day and night are of approximately equal length, marking the beginning of spring and fall, typically occurring around March 21 and September 23.

Tropical Year

The time between equinoxes which is slightly shorter than 1 solar Earth orbit and is approximately 365.24 days long, marking the cycle of seasons.

Tropics

the regions of Earth located between the Tropic of Cancer and the Tropic of Capricorn (23.5 N and 23.5 S), the sun is directly overheard on the equinoxes

Precession of the Equinoxes

The change of the positon of the equinoxes over time due to the Earth's axial tilt and orbital motion, resulting in a gradual shift in the alignment of the stars as viewed from Earth.

Noon

The time at which the Sun crosses the meridian.

Equator

Imaginary line on Earth dividing it in half.

At the equator all stars rise and set each day.

At other latitudes, the celestial equator intersects the horizon due east and due west. Therefore, a star on the celestial equator rises due east and sets due west. Stars north of the celestial equator rise north of east and set north of west. Stars south of the celestial equator rise south of east and set south of west.

Tropical Year

The time between one crossing ot the vernal equinox and the next. Slightly shorter than the time it takes for Earth to orbit once about the sun.

New Moon

When the moon is between Earth and the sun.

Far side illuminated, from Earth its in darkness.

-UP AT DAYTIME.

• Up at daytime

• NEVER visible in night

• Rises with the sun at sunrise

• Crosses the meridian near noon

• Sets with the sun in the west.

Cresent

Phase in which the object appears less than half illuminated by the Sun

Gibbous

Phase in which the object appears more than half illuminated by the Sun

Waxing Crescent

• Moon visible east of the sun

• Most noticeable just after sunset, near the west

• Lit on the west side

First Quarter Moon

• 1 week after a new moon

• Named due to a fourth of its way through orbit

• Rises at noon

• Meridian at Sunset

• Sets as Midnight

Full Moon

• Opposite of the sun

• Viewed from Earth fully illuminated by the sun

• 2 weeks after the new moon

• Rises as the sun sets

• Meridian at midnight

• Sets at sunrises

Third Quarter Moon

• Half of the near side is in sunlight and half darkness

• Rises at Midnight

• Crosses meridian near sunrise

• Sets at noon

Eclipse

When the shadow of one astronomical object falls on another

Solar eclipse

When the Moon passes between Earth and the Sun casts a shadow on Earth.

• small shadow

Lunar Eclipse

• Moon is in the Earth’s shadow occurs when the Earth passes between the Sun and the Moon, causing the Earth’s shadow to cover the Moon.

Geocentric Model

An Earth-centered model of the solar system which prevailed for 1,500 years in which the planets and the sun moved in circles around a stationary Earth

Apparent Retrograde Motion

Movement of the planets with respect to the “fixed stars” in which plants appear to move westward for a period of time before resuming their regular eastward motion. The explanation of this is much simpler with the heliocentric model compared to the geocentric.

This can be easily understood as an illusion caused by the relative motion between Earth and the other planets

Ptolemy’s Explanation of Apparent Retrograde in the Geocentric Model

Ptolemy’s model of the solar system included interconnected circles. While traveling along its large circle, a planet would at the same time be moving along its smaller circles.

Heliocentric Model / Copernican Revolution

While not the first person to propose that the solar system was centered on the sun, Copernicus (1473-1543) was the first to develop a mathematical model that made testable predictions about the planetary orbits published in De revolutionibus orbium coelestium (“On the Revolutions of the Heavenly Spheres”)

A frame of reference

A coordinate system within which an observer measures positions and motions.

Empirical

Based on observation and experimentation rather than theory or pure logic.

Kepler’s Three Laws

1. Law of Planetary Motion Planets move in elliptical orbits

2. Law of Equal Areas Planets move fastest when its closest to the Sun and slowest when it is further from the sun / the area swept out by a planet during a specific time interval is always the same regardless of the location of the planet in orbit

3. Harmonic Law The mathematical relationship between the period of a planets orbit (in years) and its semimajor axis (AU) Distance³ = p²

Ellipse

A specific type of oval symmetric from right to left and from top to bottom. The semi major axis defines the size of an ellipse.

Foci

One of two points that define an ellipse

The shape of an ellipse is given by is eccentricity (e) the ratio of the distnace between foci to the length of the major axis ranging from 0-1. A numeral closer to 0 indicating a shape more comparable to a perfect circle.

Newton’s Law of Motion

First Law (Law of Inertia): An object at rest stays at rest, and an object in motion continues in motion with the same speed and in the same direction unless acted upon by a net external force.

Second Law (Law of Acceleration): The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This is often expressed with the formula F = m*a, where F is the force, m is the mass, and a is the acceleration.

Third Law (Action and Reaction): For every action, there is an equal and opposite reaction. This means that for every force exerted by one object on another, there is a force of equal magnitude but in the opposite direction exerted by the second object on the first.

Velocity

speed with direction

acceleration

rate of change of velocity

Ole Rømer

Studied movement of Jupiter moons observing that they did not follow the predicted schedule set up Kepler’s Laws due to the Earth’s orbit

Light

• Properties of Light 

  • Light moves @ 300,000 km/s Romer 

    • Measured by observing Juptiter’s moon Io

    • Io period 1769 

• Light is a form of energy

  • Force relation to energy 

  • Motion of object require energy 

  • Energy is the ability to do work on matter; doing work involves changing the speed of objects (kinetic energy)

    • Doing work involves changing the speed of objects

• Law of conservation of energy

  • Energy can be converted from one to another but it cannot be created or destroyed 

  • Joules (J) standard measurement

  • KE = ½ mv^2

    • V = speed

    • M = mass

Power

• Energy = / = power 

• Power is the rate at which you use energy or do work 

• Power energy/time

Waves

• Means of transporting energy 

• Typically requires a medium

Mechanical Waves

Wave that periodically deforms then regains its shape

Electromagnetic waves

Can travel through a vacuum/without a medium

Peaks / crests

Highest points on the wave

Valleys / troughs

lowest point on the wave 

Wavelength

length between crests  

Period

The time it takes for one wave to pass by a given point in the medium or one point in space

Frequency

Record of how many full wave cycles pass by a given point in space per second

Kinetic Energy

Energy due to its motions and mass.

Thermal Energy

Sum of kinetic energy of the moving bits of matter inside a substance

Potential Energy

Energy stored in an object due to its position or configuration.

Light as a Wave

Requires a mediumto travel through, such as air or water, and exhibits properties like reflection, refraction, and diffraction.

Light as a Particle

Describes light's behavior as discrete packets of energy called photons, which can transfer energy, exhibit particle-like properties, and account for phenomena like the photoelectric effect.

electromagnetic wave

A type of wave that consists of oscillating electric and magnetic fields and can travel through a vacuum, carrying energy across space.

Electromagnetic Spectrum

Gamma, X-ray, UV, Visible, Infared, Microwave, Radio Waves (LEFT TO RIGHT wavelength increasing therefore decreasing the energy)

Matter

Anything that occupies space and has mass

Absorption

The capture of electromagnetic radiation by matter

Emission

The release of electromagnetic radiation by matter

Integration Time

The time interval during which the eye can add up photons—this is analogous to leaving the shutter open on a camera. The brain “reads out” the information gathered by the eye about every 100 milliseconds (ms).

Quantum efficiency

A measure of the detector's efficiency in converting incoming photons into detectable signal. It represents the percentage of photons hitting the detector's surface that successfully produce an electron-hole pair, which contributes to the measured signal. Higher quantum efficiency indicates better sensitivity, as more of the incoming light is converted into a usable signal.