Chapter 26Chapter 26

The Sun and the Solar The Sun and the Solar SystemSystem

Chapter 26.1Chapter 26.1

The Sun’s Size, Heat and StructureThe Sun’s Size, Heat and Structure

SizeSize

More than 1,000,000 earth’s would fit inside More than 1,000,000 earth’s would fit inside the sunthe sun

The sun’s diameter is 110 times the earth’sThe sun’s diameter is 110 times the earth’s Compared to other stars it is just average in Compared to other stars it is just average in

sizesize If the sun was a bottle cap the largest star, If the sun was a bottle cap the largest star,

Epsilon Aurigae, would be the size of a Epsilon Aurigae, would be the size of a football fieldfootball field

Sun’s EnergySun’s Energy

Fusion – the combining of the nuclei of lighter Fusion – the combining of the nuclei of lighter elements to form heavier elements is the elements to form heavier elements is the source of energy of all starssource of energy of all stars

E = mcE = mc22 – this equation shows the relationship – this equation shows the relationship between mass and energybetween mass and energy– Matter can be converted into energyMatter can be converted into energy

Due to intense heat and pressure, atoms get Due to intense heat and pressure, atoms get torn apart into the nuclei and electrons. torn apart into the nuclei and electrons. This results in H & He existing as a plasmaThis results in H & He existing as a plasma

These nuclei normally repel each other, These nuclei normally repel each other, however, due to their speed, over crowding however, due to their speed, over crowding and heat, they are forced to fuse.and heat, they are forced to fuse.

When 4 Hydrogen nuclei come together, When 4 Hydrogen nuclei come together, they produce a Helium nucleus. A by-they produce a Helium nucleus. A by-product of this is energy.product of this is energy.

Sun’s LayersSun’s Layers

During the fusion reaction, energy is produced During the fusion reaction, energy is produced inside the sun that pushes outward is balanced inside the sun that pushes outward is balanced by the force of gravity drawing the layers inwardby the force of gravity drawing the layers inward

Core – mostly plasma H & HeCore – mostly plasma H & He– Temperature ≈ 15,600,000°CTemperature ≈ 15,600,000°C

Radioactive Zone – surrounds the coreRadioactive Zone – surrounds the core– Near the core ≈ 8,000,000°CNear the core ≈ 8,000,000°C– Near the convection zone (next layer) ≈ Near the convection zone (next layer) ≈

2,000,000°C2,000,000°C

Convection Zone – rising and falling currents Convection Zone – rising and falling currents carry energy to sun’s surfacecarry energy to sun’s surface

Photosphere – Photosphere – visible surface visible surface of the sunof the sun– Consist of granules – 1,000km wide, 20 minute lifeConsist of granules – 1,000km wide, 20 minute life– Temperature ≈ 6,000°CTemperature ≈ 6,000°C

Inner atmosphere – chromosphereInner atmosphere – chromosphere– Area where solar prominences take placeArea where solar prominences take place

Outer atmosphere – corona – visible during Outer atmosphere – corona – visible during total solar eclipsestotal solar eclipses

Chapter 26.2Chapter 26.2

Features of the SunFeatures of the Sun

Sun is 150,000,000km away from earth, this Sun is 150,000,000km away from earth, this distance is known as an Astronomical Unit distance is known as an Astronomical Unit (A.U.)(A.U.)

Sunspots – Dark spots on the photosphereSunspots – Dark spots on the photosphere– Some are barely visible while others are 4 Some are barely visible while others are 4

times larger than Earthtimes larger than Earth– Small one may last a few hour – large ones Small one may last a few hour – large ones

monthsmonths

– Are very hot and bright – look dark because the Are very hot and bright – look dark because the photosphere is so much hotter and brighter than photosphere is so much hotter and brighter than the sunspotsthe sunspots

– Move from left to right across surfaceMove from left to right across surface This gave evidence that the sun rotatesThis gave evidence that the sun rotates

– An increase in sun spots may result in An increase in sun spots may result in increased solar flares, solar winds and aurorasincreased solar flares, solar winds and auroras

– Sunspot activity peaks every 11 yearsSunspot activity peaks every 11 years

Sun’s rotationSun’s rotation– At the equator – 25 daysAt the equator – 25 days– At the poles – 34 daysAt the poles – 34 days

Solar winds – corona gives off a constant Solar winds – corona gives off a constant stream of electrically charged particlesstream of electrically charged particles– Mostly protons and electronsMostly protons and electrons– The earth’s magnetic field will reflect most of The earth’s magnetic field will reflect most of

them p.514them p.514– Auroras – bright lights at the earth’s poles Auroras – bright lights at the earth’s poles

caused by solar wind particles interacting with caused by solar wind particles interacting with earth’s magnetic fieldearth’s magnetic field

– Holes in the corona (coronal holes) and solar Holes in the corona (coronal holes) and solar flares are sources of solar windsflares are sources of solar winds

Chapter 26.3Chapter 26.3

Observing the Solar System: A Observing the Solar System: A HistoryHistory

The movement of Planets and StarsThe movement of Planets and Stars

As we watch the sun go across the sky it As we watch the sun go across the sky it appears to move as we stand still.appears to move as we stand still.

For 2,000 years it was the belief that the For 2,000 years it was the belief that the earth was the center of the universe, it is earth was the center of the universe, it is called geocentric (earth centered)called geocentric (earth centered)

Stars were thought to have been holes in a Stars were thought to have been holes in a celestial sphere that surrounded earth. celestial sphere that surrounded earth. Behind the sphere was a source of intense Behind the sphere was a source of intense lightlight

The changing positions of constellations gave The changing positions of constellations gave basics for the 1basics for the 1stst calendars calendars

Some points were not fixed in constellation, Some points were not fixed in constellation, they wandered. Astronomists believe those they wandered. Astronomists believe those point of lights were closer (Planets)point of lights were closer (Planets)

Most of the time the planets move eastward Most of the time the planets move eastward however they stop and then move west for a however they stop and then move west for a few weeks, then back eastward, this is known few weeks, then back eastward, this is known as retrograde motion.as retrograde motion.

Chapter 26.4Chapter 26.4

History of AstronomersHistory of Astronomers

Ptolemy – lived in Egypt in the 2Ptolemy – lived in Egypt in the 2ndnd century ADcentury AD

Geocentric Model – explained retrograde Geocentric Model – explained retrograde motion by the use of epicycles – perfect motion by the use of epicycles – perfect spheres the planet revolved on while on the spheres the planet revolved on while on the planetary sphereplanetary sphere

CopernicusCopernicus

Polish astronomer (1473-1543) proposed a Polish astronomer (1473-1543) proposed a heliocentric (sun centered) solar systemheliocentric (sun centered) solar system

Could explain retrograde by the different Could explain retrograde by the different speeds the planets (including earth) went speeds the planets (including earth) went around the sun (p. 578)around the sun (p. 578)

Tycho BraheTycho Brahe

1616thth century observational astronomer century observational astronomer made in-depth study of the moon and made in-depth study of the moon and

planets throughout their orbitsplanets throughout their orbits identified a number of unexpected identified a number of unexpected

occurrence if the orbits were roundoccurrence if the orbits were round Died before he could apply his dataDied before he could apply his data

KeplerKepler

Used Tycho’s work and found out that the Used Tycho’s work and found out that the orbits were elliptical rather than roundorbits were elliptical rather than round

Created 3 laws of planetary motionCreated 3 laws of planetary motion

11stst law law

planets travel in elliptical orbits with the sun planets travel in elliptical orbits with the sun at one focusat one focus

22ndnd law law

Planets travel faster when closer to the sunPlanets travel faster when closer to the sun– this law is also known as the equal area lawthis law is also known as the equal area law– planets sweep out equal area in equal timeplanets sweep out equal area in equal time

33rdrd Law or Harmonic Law Law or Harmonic Law

is used to find a planets mean distance from is used to find a planets mean distance from the sunthe sun– PeriodPeriod22 = Distance = Distance33

period – time taken to revolve around the sunperiod – time taken to revolve around the sun distance – mean distance between the planet distance – mean distance between the planet

and the sunand the sun The average speed of earth in its orbit is The average speed of earth in its orbit is

30km/sec30km/sec

Newton (1642 – 1727) English Newton (1642 – 1727) English scientist mathematicianscientist mathematician

Newton identifies gravity as the force that Newton identifies gravity as the force that keeps the earth in orbit around the sunkeeps the earth in orbit around the sun

The strength of gravity is proportional to the The strength of gravity is proportional to the masses and indirectly to their distancemasses and indirectly to their distance