astronmy chapter 2

What is retrograde motion?

The unpredictable backward motion of planets.

What is the Geocentric model?

The belief that Earth is the center of the universe.

What are inferior planets?

Planets that never stray far from the sun.

What are superior planets?

Planets that are not tied to the sun.

What is the Ptolemaic model?

A geocentric model of the solar system developed by Ptolemy.

What are epicycles?

Little sub circles used to explain retrograde motion in the Geocentric model.

What is the Heliocentric model?

The belief that the sun is the center of the universe.

Who developed the Heliocentric model?

Copernicus.

How did the Heliocentric model explain retrograde motion?

As a change of perspective as the Earth passes the planets in their orbits.

Why was the Heliocentric model not widely accepted?

Due to its conflict with religious beliefs at the time.

Who observed the revolution of Jupiter's moons around Jupiter?

Galileo.

What did Galileo's observations of Jupiter's moons support?

The Heliocentric model.

What did Galileo use to observe Jupiter's moons?

His newly developed telescope.

What did the observations of Jupiter's moons parallel?

Copernicus' model of the solar system.

What did the Catholic church adopt?

The Geocentric model.

What did the Geocentric model fit well with?

The belief that Earth was the center of all things.

What did the Heliocentric model predict better?

Planetary motion.

What did the Heliocentric model explain retrograde motion as?

A change of perspective as the Earth passes the planets in their orbits.

What did the Heliocentric model conflict with?

Current religious beliefs.

Who is considered the father of experimental science?

Galileo Galilei

What theories greatly angered the Catholic church?

Heliocentric Theory

What happened to Galileo Galilei as a result of his theories?

Arrested and forced to recant under threat of torture, spent last years under house arrest

Who made meticulous observations of planetary positions?

Tycho Brahe

What did Tycho Brahe's observations support?

Copernican model of the solar system

Who did Tycho Brahe collaborate with?

Johannes Kepler

What was Johannes Kepler's contribution to the development of the planetary model?

Used Tycho Brahe's data to determine planetary orbits were ellipses

What did Johannes Kepler develop regarding planetary motion?

Laws regarding planetary motion

What did Kepler's first law state?

Planets move around the sun in ellipses with two foci, one empty and one containing the sun

What did Kepler's second law state?

Areas swept out by planets as they move around their orbits are equal

What does the current model of the Solar System consist of?

Sun, 8 planets, their moons, and other objects in elliptical orbits around the sun

What question did Sir Isaac Newton solve?

Why do planets move as they do

Who is considered the most influential scientist in history?

Sir Isaac Newton

Who is considered the most intelligent man who ever lived?

Isaac Newton

What groundbreaking field did Isaac Newton develop?

Differential calculus

What fundamental laws of motion did Isaac Newton develop?

Newton's Laws of Motion

What did Newton's laws of gravitation explain?

The orbits of planets

What is Newton's First Law of Motion?

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

What is Newton's Second Law of Motion?

When a force F acts on a mass m, it produces an acceleration a equal to the force divided by the mass (F=ma).

What is Newton's Law of Gravity?

Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.

What did Newton postulate about the planets' motion?

There must be a force acting on the planets since their motion was not in a straight line but being continually 'pulled' towards the sun.

What did Newton develop after studying the orbits of the planets and their velocities?

The law of universal gravitation.

What are telescopes?

Instruments that collect and focus light and other forms of electromagnetic radiation.

What are the two general types of telescopes?

Optical telescopes and non-optical telescopes.

What do optical telescopes focus?

Visible light.

What are the two types of optical telescopes?

Refracting telescopes and reflecting telescopes.

What do refracting telescopes use to focus light?

Lenses.

What is the advantage of refracting telescopes?

Good magnification and resolution.

What is the disadvantage of refracting telescopes?

Poor light collection and inability to focus all wavelengths simultaneously.

What do reflecting telescopes use to focus light?

Curved mirrors.

What is the advantage of reflecting telescopes?

Excellent light collection and less expensive to construct.

What is the disadvantage of reflecting telescopes?

Resolution not quite as good as refracting telescopes.

What type of telescope is currently favored by astronomers?

Reflecting telescopes.

What is the limiting factor to getting quality optical images?

Light collection.

Why do astronomers build telescopes with larger mirrors?

To gather more light and see fainter objects in the sky.

How much more light can the largest telescopes collect compared to the human eye?

More than a million times.

How is the size of a telescope characterized?

By the diameter of its lens or mirror.

What is the diameter of a 36-inch telescope?

36 inches

What is the purpose of a telescope with low light collection capabilities?

To obtain images with good definition of most objects

What is the effect of using a telescope with high light collection capabilities?

Many more objects are visible, but high luminosity objects are 'washed out'

How can brighter images be obtained?

By photographing an image with long exposure time

What is needed to get quality images when photographing with long exposure time?

Good tracking equipment

What is the diameter of the mirrors in the largest optical/infrared telescopes?

10 meters

Why do large telescopes use segmented mirrors?

Smaller mirrors are easier and cheaper to build

What are the advantages of larger mirrors in telescopes?

Collect more light, see fainter objects, and provide sharper images

What causes stars to appear blurry in telescopes?

Turbulence in the Earth's atmosphere

Why must gamma-ray and x-ray telescopes be in space?

Those wavelengths don't penetrate the atmosphere

Which types of telescopes can operate from the ground?

Optical, infrared, and radio telescopes

What makes optical and infrared images blurry when observed from the ground?

The atmosphere

What are the requirements for an optical observatory on the ground?

Dark skies, clear skies/few clouds, stable air, high altitude

What are the requirements for a radio observatory on the ground?

An area far from cell phones and TV/radio stations

Where are some optical and infrared observatories located?

Hawaii, Chile, Arizona, Texas

What is the ability of some telescopes on the ground to correct for atmospheric blurring?

Partial correction

What is the purpose of a 36-inch telescope?

To observe objects with a lens or mirror that is 36 inches in diameter

What is the image quality obtained from a telescope with low light collection capabilities?

Good definition of most objects

What is the image quality obtained from a telescope with high light collection capabilities?

Many more objects are visible, but high luminosity objects are 'washed out'

What is a space-based telescope?

Telescope that avoids atmosphere distortion and light pollution.

What are the advantages of space-based telescopes?

Detect x-rays and infrared wavelengths, capable of incredible magnification.

How has the Hubble Space Telescope changed our view of the universe?

Fundamentally changed how we see the universe.

What is the diameter of the mirror of the Hubble Space Telescope?

2.4 meters.

Why does the Hubble Space Telescope produce sharp images?

It is above the atmosphere.

What do ground-based telescopes lack compared to space-based telescopes?

Ability to avoid atmosphere distortion and light pollution.

What type of images does the Hubble Space Telescope provide?

Very sharp images of tiny patches of sky.

What is the advantage of telescopes designed to photograph the entire sky?

Possible to search for new rare objects.

What is the purpose of space-based telescopes?

Collect light across the entire electromagnetic spectrum.

What do we see at different wavelengths?

Different phenomena.

Name some space observatories.

Hubble (visible), Chandra (x-ray), Galex (UV), Spitzer (infrared), WMAP (radio), Compton (gamma ray).

What does Chandra detect?

Objects with very high temperatures.

What has Chandra been invaluable in studying?

High-energy objects like black holes and active galactic nuclei.

What does the Spitzer Space Telescope detect?

Objects with lower temperatures.

Why does the Spitzer telescope need to be super-cooled?

To detect infrared light.

What happened to the Spitzer's coolant in 2009?

It ran out.

What is the main function of the Kepler Space Telescope?

Detection of exoplanets.

How does the Kepler Space Telescope detect exoplanets?

By observing fluctuations of star luminosities.

How many exoplanets has the Kepler Space Telescope identified?

2000+.

What is the purpose of the James Webb telescope?

N/A

What is the James Webb Space Telescope?

A more capable telescope replacing the Hubble.

What is the primary mirror size of the James Webb Space Telescope?

6.6M segmented mirror, larger than Hubble's 2.4M mirror.

What is the purpose of the multiple layered heat shield on the JWST?

To eliminate contamination of images from solar heat.

What are the control systems on the JWST for?

To compensate for solar wind.

What is the purpose of the multiple heat sinks and radiators on the JWST?

To prevent heat contamination from internal systems.