Chapter 26 ~

Stars and Galaxies

Section 1 ~ Constellatio

ns

Chapter 26 Section 1Before you read - write the reading’s objectives in this space:1 – _____________________________________________________________________________________________________________________________________________________________________2 – _____________________________________________________________________________________________________________________________________________________________________3 - ______________________________________________________________________________________________________________________________________________________________________

Before you read - write the reading’s objectives in this space:

1 - Describe a constellation as a pattern of stars.

2 - Compare and contrast types of optical telescopes.

3 - Explain how a radio telescope differs from an optical one.

What is a Constellation? __________________________________________________________________________________________________________________________________________________________________

•Constellations and the stars that make them up are visible with the unaided eye.

1

What is a Constellation? Long ago, people named patterns of stars after characters in stories, animals, or tools. Constellations are names given to these star patterns by ancient cultures

•Constellations and the stars that make them up are visible with the unaided eye.

What are telescopes used for? ____________________ .___________________________________________________________________________________________________________________________There are two basic types of optical telescopes, what are they? 1- _________________- Uses only lenses to study light.

Light passes through the objective lens. The eyepiece then magnifies the image.

2

What are telescopes used for? Optical telescopes are used to study objects in visible light, and radio telescopes are used to study objects in the radio wavelengths.

There are two basic types of optical telescopes, what are they? 1- Refracting telescope - Uses only lenses to study light.

Light passes through the objective lens. The eyepiece then magnifies the image.

2- A ________telescope uses a mirror as an objective to reflect light to the focus.

Light passes through the open end of a reflecting telescope and strikes a concave mirror at the base of the telescope.

3

2- A reflecting telescope uses a mirror as an objective to reflect light to the focus.

Light passes through the open end of a reflecting telescope and strikes a concave mirror at the base of the telescope.

How can you can find the magnifying power (Mp) of a telescope? ________________________________________________________________________________

Formula:

4

How can you can find the magnifying power (Mp) of a telescope?

Divide the focal length of the objective (fo) by the focal length of the eyepiece (fe).

Formula:Mp = fo/fefe(Mp) = fo

fe = fo/Mp

What would the magnifying power for a telescope with a focal length of 3,000mm and an eyepiece with a focal length of 40mm be? Formula:

Plug in and solve:

5

What would the magnifying power for a telescope with a focal length of 3,000mm and an eyepiece with a focal length of 40mm be? Formula:

Plug in and Solve:

Mp = fo/fe

Mp = 3,000mm/40mm

Mp = 75 times

If the focal length of a telescopes objective is 800mm and the magnifying power of the telescope is 40 times, what is the focal length of the eye piece?

Formula to use:

Plug in and solve:

6

If the focal length of a telescopes objective is 800mm and the magnifying power of the telescope is 40 times, what is the focal length of the eye piece?

Formula to use:

Plug in and solve:

fe = fo/Mp

fe = 800mm/ 40

fe = 20mm

The most recent innovations in optical telescopes involve active and adaptive optics.

_____________________________________________________________________________________________________________________________

What does adaptive optics do?

_____________________________________________________________________________________________________________________________

7

The most recent innovations in optical telescopes involve active and adaptive optics.

With active optics, a computer is used to correct changes in temperature, mirror distortions, and bad viewing conditions.

What does adaptive optics do?

Uses a laser to probe the atmosphere and relay information to a computer about air turbulence.

What is a radio telescope? ____________________________________________________________________________________ Radio waves have long wavelengths, a radio telescope must be built with a very large objective, usually some form of dish antenna.

Astronomers often build several radio telescopes close together and connect them to form one large telescope.

8

What is a radio telescope? A telescope that collects and amplifies radio waves.

Radio waves have long wavelengths, a radio telescope must be built with a very large objective, usually some form of dish antenna.

Astronomers often build several radio telescopes close together and connect them to form one large telescope.

How Hubble Sees (2 min)

Hubble Space TelescopeEven using active and adaptive optics, the atmosphere limits what Earth-based telescopes can achieve. For this reason, astronomers use space telescopes, such as the Hubble Space Telescope.What is a light-year?

__________________________________________________________________________________________________________________________________________________________________________________________________________________

9

NOVA Saving Hubble Update 15min

How Hubble Sees (2 min)

Hubble Space TelescopeEven using active and adaptive optics, the atmosphere limits what Earth-based telescopes can achieve. For this reason, astronomers use space telescopes, such as the Hubble Space Telescope.What is a light-year?

The distance that light travels in one year. Speed of light 186,000 miles/secThe distance light travels in one full year is about 6 trillion miles.

Speed of light 186,000 miles/sec

The distance light travels in one full year is about 6 trillion miles.

That's well beyond the bounds of the solar system, yet only a quarter of the way to the nearest star, Alpha Centauri, in the southern constellation of the Centaur. It will take another three-plus years before we reach that star's burning surface. Alpha Centauri is more than 26 trillion miles or 4.3 light years away.

What is a spectroscope? ____________________________________________________________________________________________________________________________________________________________________________________________Can you think of a time when we did something similar?

**This can tell astronomers a great deal about a star. For example, they can determine its

chemical composition, its surface temperature, and

whether it is moving away from or toward

Earth.

10

What is a spectroscope? A device that uses a prism or diffraction grating to disperse the light into its component wavelengths. A spectroscope disperses light into its individual wavelengths, or its spectrum.

Can you think of a time when we did something similar?

**This can tell astronomers a great deal about a star. For example, they can determine its

chemical composition, its surface temperature, and

whether it is moving away from or toward

Earth.

What does a spectroscope do?

                                         A spectroscope helps us find out what stars are made of. It disperses, or separates, white light from a star into a very wide spectrum of colors — much wider than a normal prism does. When spread very wide, black lines appear in the spectrum.The first scientists to observe these lines wondered why they were there and what they meant. It turns out that particular elements in the star created particular patterns of lines. Once scientists knew the element responsible for a certain pattern, they knew which elements were present in the star. This was a revolutionary discovery.

Section CheckSection Check

11Question 1

A refracting telescope uses a _______ as an objective.

A. mirrorB. waveC. convex lensD. laser

11

Section CheckSection Check

11Answer

The answer is C. Convex lens are curved outward like the surface of a ball.

Section CheckSection Check

11Question 2

What does a spectroscope do?

12

Section CheckSection Check

11Question 2

What does a spectroscope do?

Answer

A spectroscope disperses the light from a star or other celestial object collected by a telescope into an electromagnetic spectrum.

Section CheckSection Check

11Question 3

What is the distance that light travels in one year?

A. 15 million kmB. 9.5 trillion kmC. 12 billion kmD. 2 million km

13

11Section CheckSection Check

Answer

The answer is B. Large distances in space are measured in a unit called a light-year, which is 9.5 trillion km.