Күн жүйесі денесіне дейінгі ара қашықтықты параллакс әдісімен анықтау. Физика, 9 сынып, презентация.

ASTROPHYSICS

parallax

PARSEC

luminosity and intensity

magnitude

Learning Objectives

Explain that parallax makes closer stars seem to move relative to more distant ones over the course of a year and size of angles.

Define a parsec.

Know that luminosity depends on temperature and size/magnitude of the star.

Explain why the observed intensity of light from a star (as seen on Earth) depends on the star’s luminosity and its distance from Earth.

Tri-Lingual Keyword Table

Glossary of Keywords

Astronomy: Observation of the motion and distribution of celestial objects.

Astrophysics: Application of physics to astronomy.

Cosmology: Study of the universe as a whole, its origin, and fate.

Space Science: Deals with exploration, including putting people in space.

Astrology: Attempt to predict the future based on the positions of the stars and planets

MILKY WAY GALAXY FACTS

http://space-facts.com/milky-way/

The Solar System

Contains the sun, planets, satellites, asteroids and comets.

Planets include:

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Planets, moons, and comets do not emit light: they just reflect it.

Distances and Velocities in the Solar System

Radar techniques is used.

Radio telescopes are used to send short pulses of radio waves towards a planet or asteroid, which reflect it back.

2d = Ct

where

C = speed of light in a vacuum

d = distance between the telescope and the planet or asteroid

t = total time taken by light to travel from telescope to the planet and back.

Astronomical Units

Light Year (ly)

Basic Trigonometry

Sine, Cosine, and Tangent

https://www.youtube.com/watch?v=oQYcZvh2JHw

Show to class the above video

Parallax Angle, p

Stellar Parallax

The distance to nearby stars can be measured by parallax

Observe how they move relative to very distant stars when the Earth is in different parts of its orbit .

This gives a unit of distance called a parsec (pc).

Stellar Parallax: This is the shifting of nearby stars against the background of more distant ones due to the orbital movement of the Earth about the Sun.

The Parsec

Summary

A parsec is the distance of a star whose apparent position moves by one second of arc when viewed from Earth on two occasions half a year apart.

The angle of parallax measured from the star to the Earth at the two extremes of its orbit is one second of arc.

Important Sizes and Conversions

Complete the Table

Distance Measurement in Parsec

With ground based telescopes the parallax method of distance measurement is acceptably accurate for distances up to

100 pc

Remember!

Question 1

The smallest angle that can be measured between light rays that arrive at the surface of the Earth is 0.01 arc second. What is the distance to a star that subtends this angle? 100 pc

Remember!

Parsec means parallax arcsecond.

Question 2

If the angle subtended by a star is 1 arc second , what is the distance to the star in metres? 3.1E16m

Question 3

Calculate the angle subtended by a star that is 5 pc away from the Earth. 0.2 arcseconds

Question 4

A star subtends an angle of 0.15 arc seconds to the Earth. Calculate its distance. 6.7 pc.

Homework Questions

What are the principal contents of our Solar System?

What is meant by: an astronomical unit, a parsec and a light-year?

How do we measure the distance to objects in the Solar System using radar?

Outline the main differences between planets and comets.

Explain why a comet has a tail which always points away from the Sun

Give the definition of a light-year.

Calculate the distance of a light-year in metres.

Why is the size of observable universe limited by the speed of light?

Laws of Logarithms

Luminosity/Intensity

Energy

Luminosity ( L)

The total energy emitted by a star per second

Apparent brightness ( B)

The amount of energy per second received per unit area.

Luminosity-Apparent Bightness Formula

Question 1

Question 2

Question 3

Luminosity and Magnitude

Luminosity of a star in the night sky depends on: its temperature and its distance from us.

The brightest stars will be close to us and have a high luminosity

The brightest stars are given apparent magnitude 1 and the dimmest apparent magnitude of 6

A magnitude 1 star has an intensity 100 times greater than a magnitude 6 star.

Magnitude Scale of Ancient Greeks

Luminosity and Magnitude Scale

Magnitudes

Types of Magnitudes

Apparent

Apparent magnitude , m, is based on how bight things appear from the Earth.

Apparent magnitude, m, is related to intensity, I, by the following formula:

m = -2.5 logI + Constant

Apparent magnitude, m of a star in the night sky is a measure of its brightness which depends on the intensity of the light received from the star.

Absolute

Absolute magnitude ,M, is based only on the luminosity of the star.

It does not depend on a star’s distance from the Earth

Is defined as what its apparent magnitude would be if it were 10 parsecs away from the Earth.

Apparent ,m, and Absolute ,M, Magnitudes.

Star Brightness

Remember!

Apparent Magnitude, m, means how bright a star looks from the Earth.

Luminosity, L, means how much energy a star puts out per second.

Absolute Magnitude, M, means how bright a star would look if it were 10 parsecs away.

Question 1

Eta Aquilae is a cephoid variable star in the constellation Aquila. It has an apparent magnitude of 3.87 and an absolute magnitude of -3.91. Calculate the distance of Eta Aquilae from the Earth.

360 pc

Question 2

(a) What is the relationship between apparent magnitude and intensity?

(b) What is the equation that links apparent magnitude, absolute magnitude, and distance?

(c) Calculate the absolute magnitude of the Sun given that the Sun’s apparent magnitude is -27.

Question 3

The star Sirius has an apparent magnitude of -1.46 and an absolute magnitude of +1.4.

The star Canopus has an apparent magnitude of -.072 and an absolute magnitude of -5.5.

(a) What of the two stars appears brighter from the Earth?

(b) Calculate the distance of Canopus from the Earth.

Question 4

Question 5

A Blackbody

Absorbs all incident electromagnetic radiations, regardless of frequency or angle of incidence, and reflects none.

Is a perfect emitter of radiations.

Stars are approximately black body radiators

Stefan’s Law

Luminosity and Temperature.

Question 1

A metal ball 3 cm in radius is heated in a furnace to 5000 C. If its emissivity is 0.5, at what rate does it radiate energy? 114.37 W

Question 2

A person’s emissivity is about 0.98.

At a body temperature of 37 degrees Celsius, how much heat does a person radiate each second? Assume body surface area to be 1.7 m²

550 W

Luminosity and Temperature

Energy/Temperature-Wavelength Curves

Wien’s Distribution Law

The wavelength at peak power, λmax , is inversely proportional to the absolute temperature, T of the surface of a black body.

λmax T = a constant

The constant is equal to 0.0029 metre kelvin

BEWARE! The above equation is usually quoted:

λmax T = 0.0029 mK

‘mK’ does NOT mean ‘milli-kelvin’.

This equation can be used to determine the temperature of the ‘surface’ (known as the photosphere) of a star.

Question 1

Question 2

Question 3

Question 4