The Sun and It’s Family

INTRODUCTION

The sun is the most important thing in the sky for us. There could be no life on Earth without its heat and energy. The sun is a star, a swirling mass of hot gases spinning around in space. It is just like the other stars you see in the sky at night. The are suns that are far, far away. We see our sun during the day simply because it is so much closer to us.

Where did the Sun

come from?

Birth of the SunAbout 5,000 million years ago, there

was no Sun, or Earth. Our part of space was filled with a huge cloud of dust and gas. Slowly, gravity pulled this cloud together. It began to shrink and spin faster. The middle of the cloud became thick and hot and finally turned into a giant ball of glowing gas. A new star, our Sun, was born.

Orion Nebula

This is the Orion Nebula, a mass of gas and dust in which stars are born.

All stars begin the same way. They are formed in clouds of dust and gas.

Characteristics of the SunRadius, diameter & circumferenceThe sun is nearly a perfect sphere. Its

equatorial diameter and its polar diameter differ by only 6.2 miles (10 km). The mean radius of the sun is 432,450 miles (696,000 kilometers), which makes its diameter about 864,938 miles (1.392 million km). You could line up 109 Earths across the face of the sun. The sun's circumference is about 2,713,406 miles (4,366,813 km).

Characteristics of the SunMass and volumeThe total volume of the sun is 1.4 x

1027 cubic meters. About 1.3 million Earths could fit inside the sun. The mass of the sun is 1.989 x 1030

kilograms, about 333,000 times the mass of the Earth. The sun contains 99.8 percent of the mass of the entire solar system.

Characteristics of the SunTemperature: 5800 K (surface)

15,600,000 K (core)Chemical compositionJust like most other stars, the sun is

made up mostly of hydrogen, followed by helium. Nearly all the remaining matter consists of seven other elements — oxygen, carbon, neon, nitrogen, magnesium, iron and silicon.

Characteristics of the SunFor every 1 million atoms of hydrogen

in the sun, there are 98,000 of helium, 850 of oxygen, 360 of carbon, 120 of neon, 110 of nitrogen, 40 of magnesium, 35 of iron and 35 of silicon. Still, hydrogen is the lightest of all elements, so it only accounts for roughly 72 percent of the sun's mass, while helium makes up about 26 percent.

Characteristics of the Sun

ELEMENTS Abundance (pct. Of total # of atoms)

Abundance (pct. Of total mass)

Hydrogen 91.2 71.0Helium 8.7 27.1Oxygen 0.078 0.97Carbon 0.043 0.40

Nitrogen 0.0088 0.096Silicon 0.0045 0.099

Magnesium 0.0038 0.076Neon 0.0035 0.058Iron 0.030 0.014

Sulfur 0.015 0.040

Characteristics of the Sun Yellow dwarfIt may be the biggest thing in this

neighborhood, but the sun is just average compared to other stars. Betelgeuse, a red giant, is about 700 times bigger than the sun and about 14,000 times brighter.

The sun is classified as a G-type main-sequence star, or G dwarf star, or more imprecisely, a yellow dwarf. Actually, the sun — like other G-type stars — is white, but appears yellow through Earth's atmosphere.

Internal Structure and Atmosphere

Internal Structure and Atmosphere

The sun and its atmosphere are divided into several zones and layers.

1. The solar interior, from the inside out, is made up of the core, radiative zone and the convective zone.

2. The solar atmosphere above that consists of the photosphere, chromosphere, a transition region and the corona.

3. Beyond that is the solar wind, an outflow of gas from the corona.

Internal Structure and Atmosphere

(The Solar Interior) 1. Core: The core produces colossal amounts of energy, including all of the Sun's light and heat. Here the temperature and pressure are so great that hydrogen atoms are squeezed together to form helium. This reaction is called nuclear fusion.

Internal Structure and Atmosphere (The Solar Interior)

2. Radiation zone: In the radiative zone, energy from the core

slowly travels outward. This region is so dense that the Sun's energy takes about 150,000 years to work its way through.

3. Convection zone: In the convection zone, rising and falling

currents carry heat from the radiative zone to the surface. This nonstop churning is similar to what happens when you boil water on a stove.

Internal Structure and Atmosphere

(The Solar Atmosphere)

1. Photosphere: The lowest layer of the sun's

atmosphere is the photosphere. It is about 300 miles (500 kilometers) thick. This layer is where the sun's distance from the sun to Earth, light reaches our planet in about eight minutes.

Internal Structure and Atmosphere (The Solar Atmosphere)

2. Chromosphere: The next layer is the chromosphere.

The chromosphere emits a reddish glow as super-heated hydrogen burns off. But the red rim can only be seen during a total solar eclipse. At other times, light from the chromosphere is usually too weak to be seen against the brighter photosphere.

Internal Structure and Atmosphere (The Solar Atmosphere)

3. Corona: The corona is the Sun's extended outer

atmosphere. It is the luminous white halo visible in a photo of a total solar eclipse*. Mysteriously, the corona is much hotter than the surface of the Sun, so hot that it also produces a type of light called X-rays. Temperatures in the sun's corona can get as high as 3.5 million degrees F (2 million degrees C). As the gases cool, they become the solar wind.

Internal Structure and Atmosphere

(Beyond the corona) 1. Flare: Intense explosions on the Sun that spew

enormous amounts of energy into space. 2. Prominence: Great looping arcs of hot gas that erupt

from the Sun. 3. Sunspots: Dark blemishes on the Sun's surface.

Sunspots are cooler than the area around them.

How Hot is the Sun? At the core of the sun, gravitational

attraction produces immense pressure and temperature, which can reach more than 27 million degrees F (15 million degrees C). Hydrogen atoms get compressed and fuse together, creating helium. This process is called nuclear fusion.

How Hot is the Sun?

Nuclear fusion produces huge amounts of energy. The energy radiates outward to the sun's surface, atmosphere and beyond. From the core, energy moves to the radiative zone, where it bounces around for up to 1 million years before moving up to the convective zone, the upper layer of the sun's interior. The temperature here drops below 3.5 million degrees F (2 million degrees C). Large bubbles of hot plasma form a soup of ionized atoms and move upwards to the photosphere.

How Hot is the Sun?

The chromosphere, the next layer of the sun's atmosphere is a bit cooler — about  7,800 degrees F (4,320 degrees C). Visible light from the chromosphere is usually too weak to be seen against the brighter photosphere, but during total solar eclipses, when the moon covers the photosphere, the chromosphere can be seen as a red rim around the sun.

The temperature in the photosphere is about 10,000 degrees F (5,500 degrees C). It is here that the sun's radiation is detected as sunlight. Sunspots on the photosphere are cooler and darker than the surrounding area. At the center of big sunspots the temperature can be as low as 7,300 degrees F (4,000 degrees C).

How Hot is the Sun?

Temperatures rise dramatically in the corona, which can also only be seen during an eclipse as plasma streams outward like points on a crown. The corona can get about 3.5 million degrees F (2 million degrees C). As the corona cools, losing heat and radiation, matter is blown off as the solar wind.

The Family of the Sun

The Sun’s Family The solar system is located at a

distance of about 30,000 to 33,000 light years from the centre of the Milky Way galaxy. The sun is a star like other stars with the only difference that it is nearer to us as compared to other stars. It has a family of its own. The sun and its family put family of its own. The sun and its family put together are called the solar system.

The Sun’s Family The Terrestrial Planets:

Rocky Planets: Mercury, Venus, Earth & Mars

The Jovian Planets: Gas Giants: Jupiter, Saturn, Uranus

& Neptune Pluto: fits into neither category Small Icy & Rocky Bodies:

Icy: Icy Moons, Kuiper Belt Objects, & Comets

Rocky: Giant Moons, Asteroids & Meteoroids

Earth is one of 8 PLANETS in our SOLAR SYSTEM. The planets orbit a central STAR we call the SUN.

MercuryVenus

Earth

Mars

Jupiter Saturn

UranusNeptune

Rocky terrestrial planets of the inner Solar System.

Gas & ice giant planets

of the outer Solar System.

The Nine Planets

Earth is one of 8 PLANETS in our SOLAR SYSTEM. The planets orbit a central STAR we call the SUN.

MercuryVenus

Earth

Mars

Jupiter Saturn

UranusNeptune

Rocky terrestrial planets of the inner Solar System.

Gas & ice giant planets

of the outer Solar System.

The Nine Planets

The Terrestrial Planets

Earth(1 M)

Mars(0.11 M)Venus

(0.82 M)

Mercury(0.055 M)

Terrestrial Planets

Mercury, Venus, Earth & Mars “Earth-Like” Rocky Planets Largest is Earth Only in the inner solar system (0.4 to 1.5

AU) Rocky Planets:

Solid Surfaces Mostly silicates and iron High Density: 3.9-5.5 g/cc (rock & metal) Earth, Venus, & Mars have atmospheres

Solid inner core

Liquid outer core

The Jovian Planets

Jupiter(318 M)

Uranus(15 M)

Saturn(95 M)

Neptune(17 M)

The Jovian PlanetsJupiter, Saturn, Uranus &

Neptune Largest Planets: at least 15 times mass

of Earth. Jupiter, largest, is 318 Earth Masses Only in the outer solar system (5 to 30

AU) Gas Giants (“Jupiter-like”):

No Solid Surfaces (mostly atmosphere) Mostly Hydrogen & Helium Rocky/icy inner cores Low density: 0.7 to 1.7 g/cc (water is 1

g/cc)

Pluto: The Planet that Doesn’t Fit

Pluto is neither a Terrestrial nor Jovian Planet. Smallest of the planets Intermediate Density: 1.8 g/cc (mostly

icy) Pluto’s orbit is also odd:

The most elliptical orbit of all the planets

The most highly inclined: ~17º from the Ecliptic.

Largest of a distinct class of objects, but still a “planet”.

Small Icy Bodies Pluto is the largest of a class

of icy bodies: Found only in the outer solar

system Densities of 1.2 to 2 g/cc (like

ices) Examples:

Triton, large moon of Neptune Charon, Pluto’s large moon Trans-Neptunian Objects (Kuiper

Belt Objects & Plutinos)

Triton

The Leftovers (Minor Bodies)

1. Asteroids:2. Meteoroids:3. Comets:

Asteroids small, airless rocky world

revolving around the sun Too small to be called planets  the mass of all the asteroids is

less than that of Earth's moon. Most asteroids lie in a vast ring

between the orbits of Mars and Jupiter

Asteroids

253 Mathilde951 Gaspra

243 Ida

Meteoroids small bodies that travel

through space smaller than asteroids and just

a size of a pebble Most meteoroids come from

asteroids that are broken apart by impacts with other asteroids

Meteor burning up in the atmosphere.

Comets is an icy body that releases gas or dust contain dust, ice, carbon dioxide,

ammonia, methane and more As a comet gets closer to the sun, the

ice on the surface of the nucleus begins turning into gas, forming a cloud known as the coma.

Radiation from the sun pushes dust particles away from the coma, forming a dust tail, while charged particles from the sun convert some of the comet's gases into ions, forming an ion tail. 

Comet Classification by Period

Comets can be classified by the length of time they take to travel once around the Sun. Short-period comets have orbits that take less than 200 years. Two types of short-period comets are recognized. Jupiter-family short-period comets are influenced by Jupiter's gravity and have orbital periods shorter than 20 years. Their orbits usually reach the orbit of Jupiter. Halley-type short-period comets have orbital periods that range from 20 to under 200 years and go past the orbit of Neptune. Long-period comets take 200 or more years to orbit the Sun. Some long-period comets may take thousands of years to orbit the Sun, or may pass by the Sun once and then never return.

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The Giant Moons Natural satellites orbiting planets. Giant Moons:

Earth: The Moon Jupiter: Io, Europa, Ganymede, & Callisto

(the Galilean moons) Saturn: Titan Neptune: Triton

Many smaller moons, both rocky & icy.

Only Mercury & Venus have no moons.

The Giant Moons

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