Study of Universe and its parts – Stars & Planets – Astronomy

Study of Universe and its parts – Stars & Planets unit 1

This Astronomy, unit 1 lesson includes the study of universe and its parts including planets, stars and the solar system.


The study of the origin, nature, and evolution of the universe and its parts.

Even though astronomy deals with large objects…

Our understanding of them is rooted in atomic and subatomic physics.

The Astronomical Unit

(AU) ~93,000,000 miles. The distance from the Earth to the Sun.

Pluto is _______ AU from the sun.

39 AU.

Speed of Light

186,000 mi/sec. 3 x 10^8 m/sec

The Light Year

A measure of distance, not speed. The distance light travels in one year. ~63,000 AU.

Next nearest star to earth is ________

Proxima Centauri; 4.3 ly from earth.

The galaxy is ___________ ly across.

120,000 ly.

The Universe is ~ _____________ly across.

~10-15 BILLION.


Relatively small, compared to stars, nonluminous bodies that orbit stars.


Big balls of hot gas.

Star Cluster

A grouping of hundreds of thousands of stars that stretches many light years across.

The Solar System

The sun, its planets, asteroids, comets, etc.


A large system of stars, star clusters, gas, dust orbiting a common center of gas.

60000000000000000000000000 in scientific notation =

6.0 x 10^24


Fixed patterns of stars used to indicate the positions of objects in the sky.

How many established constellations?


Number of brightness that is not visible to the human eye.


Celestial Sphere

Imaginary shell that surrounds the earth on which astronomers paste apparent locations.


Marks the top of the sky above your head.


Marks the bottom of the sky directly below your feet.

Scientific Model

A carefully devised mental conception of how things work.

Angular Distance

The distance measured between two point on the celestial sphere.

Angular Diameter

The measurement of a single object from edge to edge.


The slow change in direction of Earth’s axis of rotation. Picture a spinning top. Takes 26,000 years for one cycle.


Caused by the 23.5 degree tilt of our earth and the fact that the sun hits different points of earth at different angles.

Lunar Eclipse

Occurs when the moon is full and passes through Earth’s shadow.

Solar Eclipse

Occurs when the moon passes directly between Earth and the sun.

Milankovitch Hypothesis

Small changes in Earth’s orbit, precession, and inclination (tilt) affect Earth’s climate and can cause ice ages.

Retrograde Motion

The apparent E-W, then W-E, then back to E-W motion.

Only ________ exhibit retrograde motion.


Geocentric Models

Puts the Earth and the center of the universe and insists that the Earth is motionless. Aristotle, Ptolemy

Heliocentric Models

Put the sun at the center of the solar system. Copernicus.

Stellar Parallax

The apparent motion of a body due to the motion of the observer.

Kepler’s First Law of Planetary Motion

The law of ellipses. The orbit of planets around the sun is elliptical.

Kepler’s Second Law of Planetary Motion

The law of equal areas. An imaginary line connecting the sun to the planets will sweep out and equal area in equal times.

Kepler’s Third Law of Planetary Motion

The Harmonic Law. The square of a planets period is equal to the cube of its orbit’s semi-major axis. p^2 = a^3.

Galileo’s Observations

1) Mountains on the moon. 2) Spots on the sun. 3) Too many stars. 4) Moons of Jupiter. 5) Phases of Venus.

Which of Galileo’s observations refute Aristotle’s observations?

Mountains on the moon (perfect heavenly objects.) Spots on the sun, LOTS of stars, Moons of Jupiter (Jupiter had the ability to keep its moon)

Which of Galileo’s observations supported Copernicus’s observations?

Phases of Venus b/c it proved that the sun was the center of the solar system.


A commonly accepted set of scientific ideas and assumptions.


Scientific modelling is the process of generating abstract, conceptual models for study.

Newton’s First Law

Law of Inertia. A body at motion will stay at motion until acted upon by a net outside force.

Newton’s Second Law

Law of force. a=F/m or F= ma.

Newton’s Third Law

Action-Reaction Law. Each action has an equal but opposite reaction.

Name the regions of the electromagnetic spectrum.

Visible light, infared light, microwaves, radio waves, ultraviolet, x-rays, and gamma rays.

Visible Light

Allow us to see color.

Infared Light

Allows us to sense waves as heat.


Used for cooking.

Radio Waves

Used for cell phones.


Can cause skin cancer


Project transparent imagery.

Gamma rays

Can kill living cells.

Advantages to Reflector Telescopes

Can be built bigger, cheaper, and without chromatic aberration.

How to increase “seeing” ability

Go somewhere high and dry, use interferometers (linked telescopes), and use atmospheric compensation technique (away from light pollution)

Radio Telescope

A reflecting telescope made of metal with a detector.

Advantages of space-based telescopes

Resolution is ideal and all wavelengths can be observed.