Welcome to The Solar System and The Universe Eighth Grade Elective.

Welcome to The Solar

System and The UniverseEighth Grade Elective

What Is Astronomy?

Answer the following question in your notebook: What do you think the

term “astronomy” means?

Astronomy: the branch of science that deals with celestial objects, space, and the physical universe as a whole

What Do Astronomers Do?

Study planets and the sun in our own solar system, as well as other stars, solar systems, galaxies, and the whole universe.

Try to understand how the universe works

Study the evolution of stars in an attempt to understand how our own star, the sun, and our solar system of planets were created and what will happen to them as they age

Types of Astronomers

Most astronomers concentrate on a particular question or area of astronomy: for example, planetary science, solar astronomy, the origin or evolution of stars, or the formation of galaxies.

Observational astronomers design and carry out observing programs with a telescope or spacecraft to answer a question or test the predictions of theories.

Theorist work with complex computer models of a star’s interior, for example, to understand the physical processes responsible for the star’s appearance.

What Does It Take To Be An Astronomer?

One of the most important sciences astronomers must learn is physics

Physics is the study of the laws of nature and how particles interact with one another

They also study chemistry, computer science, and mathematics

Why Study Astronomy?

Think It- Write It: Take a few minutes to write down why you decided to take this course.

Practical Uses: Knowledge of astronomy

allows us to keep track of time and seasons and predict the tides

Intellectual Interest Astronomy is a fun and

interesting science to study

It allows you to leave everyday life behind, to expand your horizons and to explore the conditions of human existence

The Celestial Sphere

The Night Sky

Activity: Close your eyes and imagine looking up at the night sky. What do you see?

Questions: Have you ever visited a planetarium? Have you ever tried to locate a

constellation? Do you know how to find the north

star?

Is The Sky Moving?

If you pay close attention to the night sky you will notice that the stars appear to move over time

Question: So, is the sky really moving? What do you think?

Answer: No, it is actually Earth that rotates on its axis (once every 24 hours), making the stars, as well as the Sun and Moon, appear to rise and set

The Celestial Sphere

Close your eyes again and imagine a huge hollow sphere that surrounds Earth. Think of all the stars as dots painted on the sphere

Note: we know this analogy isn't really correct—some stars are much further away than others—but the visual image presents a handy way of thinking about the sky.

The imaginary hollow sphere is called the celestial sphere.

Longitude and Latitude

Latitude

Latitude lines run horizontally Degrees latitude are

numbered from 0° to 90° north and south, with 0° degrees being the equator

Longitude

Longitude lines run vertically The Earth is divided into

360° longitude Zero degrees longitude is

located at the Prime Meridian (0°)

The degrees continue 180° east and 180° west where they meet and form the International Date Line

How Do Latitude and Longitude Work Together?

To precisely locate points on the earth's surface, degrees longitude and latitude have been divided into minutes (') and seconds (”)

There are 60 minutes in each degree. Each minute is divided into 60 seconds

To locate the latitude and longitude of a specific place check out this site :

http://universimmedia.pagesperso-orange.fr/geo/loc.htm

The Celestial Sphere

What is the Celestial Sphere?

The celestial sphere is an imaginary projection of the Sun, Moon, planets, stars, and all astronomical bodies upon an imaginary sphere surrounding Earth

It is a useful mapping and tracking remnant of the geocentric theory of the ancient Greek astronomers

It provides an important tool to astronomers for fixing the location and plotting movements of celestial objects

How Does It Work?

The celestial sphere describes an extension of the lines of latitude and longitude

Projections of lines of latitude and longitude are transformed into declination and right ascension

Just as every point on Earth can be expressed with a unique set of latitude and longitude coordinates, every object on the celestial sphere can be specified by declination and right ascension coordinates.

A direct extension of Earth's equator at 0° latitude is the celestial equator at 0° declination

Declination

Declination- the angular distance of a point north or south of the celestial equator

Declination is further divided into arcminutes and arcseconds

In 1° of declination, there are 60 arcminutes (60’)

In one arcminute there are 60 arcseconds (60”)

Right Ascension (longitude)

Right ascension- the distance of a point east of the First Point of Aries, measured along the celestial equator and expressed in hours, minutes, and seconds

Instead of longitude, right ascension is measured in hours

Corresponding to Earth's rotation, right ascension is measured from zero hours to 24 hours around the celestial sphere

One hour represents 15 angular degrees of travel around the 360° celestial sphere

Important Points on the Celestial Sphere

The Celestial Poles

The stars on the celestial sphere seem to rotate around the north and south celestial poles

Celestial poles- points on the celestial sphere that are directly above Earth's North and South Pole

The Celestial Poles

The North Star

If you live in the Northern Hemisphere, you’ve probably heard of the north star

The North Star, also known as Polaris is bright star that's very close to the north celestial pole!

The Celestial Equator

Another important imaginary line on the sky is the celestial equator

This line is actually an imaginary circle on the celestial sphere, directly above Earth's equator

It is always exactly 90 degrees from the celestial poles, just like Earth's equator is 90 degrees from its polesCelestial Equator

The Horizon

The horizon is the edge of our local sky

Since we are located on the surface of Earth we can see only half of the celestial sphere at one time

Zenith

The point straight overhead on the celestial sphere is called the zenith

The zenith is the point you'll see if you lie on your back and look straight up at the stars

It is always 90 degrees from the horizon.

Since the sky rotates from east to west above us, the meridian marks the halfway point of the celestial sphere.

The Meridian

Fun Facts

In the morning, the Sun is east of the meridian (because the Sun rises in the east).

At local noon, the Sun is right on the meridian

In the afternoon the Sun moves past the meridian to the west

In Latin, the morning is ante meridiem, which is abbreviated a.m. and means “before meridian”

After noon, it is post meridiem, or p.m., which means “after meridian”

Is the Sky Really

Moving?

The Sun

You know that planets orbit the Sun, but planets do not orbit at uniform velocity.

Because of the elliptical shape of Earth's orbit, Earth moves faster when closet to the sun (perihelion) and slower when it is furthest away (aphelion)

This difference in Earth's orbital velocities (speed of an object in a specific direction) makes the Sun appear to move at different speeds at different times

Why Stars Appear To Move

All the stars in the sky are pretty much standing still - they only look like they're moving

There are two different reasons why stars appear to move across our sky: The Earth is spinning The second is because the Earth

itself is moving around the Sun.

Why We See Different Stars

Standing on the surface of Earth we see the stars passing by until after a whole revolution around the Sun So, it would take a year for us to see

all the stars pass by

At the same time as the Earth is moving around the sun it is spinning on it own axis (once a day) So, we see some different stars

coming into view as the Earth spins from night to night and other stars move out of view

The Moon Is Following

Me!

Unlike the stars, the moon is actually moving in orbit around the earth

The Moon’s motion has two parts: It looks like it's moving around the

earth once per day along with everything else

In addition, it is actually moving around the earth once per month- this is what makes it move to a different place on the sky

Moon Phases

http://www.brainpop.com/science/space/moonphases/preview.weml

Key Points

A new moon occurs when the moon is positioned between the earth and sun with the illuminated portion of the moon facing away from earth

At a full moon the moon is between the earth and sun, but the moon is on the opposite side of the earth, so the entire sunlit part of the moon is facing us

Eclipses

Eclipses

An eclipse is caused by the casting of a shadow of one heavenly body on another

Recall that the Earth is in constant motion It rotates around its own axis It revolves around the sun

The moon is also in constant motion It orbits around the Earth It rotates around its own axis

Lunar Eclipse

Solar Eclipse

Constellations

Constellations

http://www.brainpop.com/science/space/constellations/preview.weml

Ancient cultures celebrated heroes, gods, and mythical beast by giving their names to groups of stars

The oldest constellations named by Western cultures originated in Assyria over 3000 years ago Babylonian and Greek astronomers

added others in the classical age 48 of these ancient constellations

are still in use

Constellations (cont)

To the ancients, a constellation was a loose grouping of stars

Constellation boundaries, when they were defined at all were only approximate Star Alpheratz could be part of

Pegasus or Andromeda. To correct gaps and ambiguities, in

1928 the International Astronomical Union established 88 official constellations

Constellation now represents not a group of stars but an area of sky and any star within the region belongs to on and only one constellationAlpheratz belongs to

Andromeda

Asterisms= less formally defined groupings of stars The Big Dipper is a well

known asterism that is part of the constellation

Ursa Major

Important to remember:

• Constellations and asterisms are groups of stars that appear

close together in the sky.

• Most are made of up of stars that are not physically

associated with one another

• Some stars may be many times farther away than othere and

moving in other directions.

• The only thing they have in common is that they happen to lie in approximately the same

direction to Earth.

Names of Stars

Ancient astronomers gave individual names to the brightest individual stars

Naming stars however is not very helpful. Why?

Simple names give you no clues to the location of the star in the sky or to its brightness.

Assign letters to the bright stars in a constellation in approximate order of brightness

Greek Alphabet or Letter used (Alpha, beta…)

Constellation of The Hand

According to the Lakota, the Constellation of the Hand, namely the bottom half of the constellation Orion, represents the arm of a great Lakota chief. The gods wanted to punish the Lakota's chief for his selfishness and made the Thunder People rip out his arm. The chief's daughter offered to marry anyone who would recover her father's arm.

Fallen Star, a young warrior whose father was a star and whose mother was human, returned the arm and married the daughter. The return of the arm to the chief symbolizes harmony between the gods and the people with the help of the younger generation.

What are some myths about Constellations?

Your task:

1. Read the Myth story given to you about a specific constellation.

2. Write a retelling of the story.

3. Draw the constellation large enough so it can be hung in our classroom.

ParallaxHow Astronomers Measure

Stars

Brightness of Stars

Astronomers measure brightness of stars using the magnitude scale System first appeared in the writings

of Ptolemy in AD 140 Probably originated earlier by Greek

astronomer Hipparchus. Hipparchus compiled the 1st known

star catalog

The ancient astronomers divided the stars into six classes Brightest = first-magnitude

The larger the magnitude number, the fainter the star

Magnitude of Star

Ancient astronomers could only estimate magnitudes

Modern astronomers can measure the brightness of stars to high precision. Adjustments were made to the scale of magnitude

Favorite Star Vega = .04

Favorite Star Sirius= -1.47

"The Sun is just one among a hundred billion stars in the Milky Way Galaxy, each with its own cosmic tale to tell."— Timothy Ferris, in the film Seeing in the Dark

The Light Year

If you could travel at the speed of light it would take you 8 minutes to reach the sun

The next nearest star, Proxima Centauri, would take you 4.2 years to reach!!

A light year is based on the distance light travels in a year At 300, 000km/sec a light year works out to be

9.5 million million kilometers! (this can also be written as 95. trillion km)

Parallax

Astronomers use parallax to measure star distances

Parallax is the apparent change in position when you look at an object from a different position

Your View Your Friend’s View

Parallax at the movies…

Parallax in Astronomy

To measure a star’s distance astronomers do the following:

1.) Look at a nearby star when Earth is on one side of the sun

2.) Look at the same star six months later, when Earth is on the opposite side of the sun

3.) Measure how much the star appears to have moved against a background of stars that are much further away

The less a star appears to move, the further away it is

Lab: How Far is That Star?

What you’ll need

Masking tape

Paper clips

Black and red pencils, plus a pen to write with

Metric ruler

Paper

Meter stick

Calculator

Lamp without a shade

Copy paper box without the lid

Objectives

Infer the apparent change in position of the dots of light for each star

Calculate the distance to an objects by using ratios of measured values

Predict the parallax of an object at different distances