WILL THE SUN SHINE FOR EVER ? Let's get a brief knowledge about the Sun and HOW much time is there for it to run out of FUEL....

THE SUN (Heart Of Our Solar System)

The Sun is a star a vast sphere of luminous gas. Its light is a by-product of gas-fueled nuclear reactions in its core. It shines steadily now, but in about five billion years it will swell up before dying as a cold, dark cinder in space. 

The Sun is a star which is located at the center of our solar system. It is a yellow dwarf star that gives off different types of energy such as infra-red energy (heat), ultraviolet light, radio waves and light. It also gives off a stream of particles, which reaches Earth as "solar wind". The source of all this energy is nuclear fusion. Nuclear fusion is the reaction in the star which turns hydrogen into helium and makes huge amounts of energy.

INTRODUCTION

The Sun is a star like many others in our Milky Way galaxy. The Sun is a type of star called a G-type main-sequence star based on its spectral class. It has existed for a little over 4.5 billion years. It is going to continue for at least as long. The Sun is about a hundred times as wide as the Earth. It has a mass of 1.9891×10³⁰ kg. This is 333,000 times the mass of the Earth. 1.3 million Earths can fit inside the Sun.

The Sun fuses about 600 million tons of hydrogen into helium every second. It can take between 10,000 and 170,000 years for the energy in the core of the Sun to escape.

Our solar system is in the Milky Way galaxy and located in an outer spiral arm. This is where we call “home.” The solar system is made up of some major and minor players, all of which interact with each other.

ORBITS

Galactic Center

RADIUS

432,376

miles

Its diameter is about 1.39 million kilometres (864,000 miles), or 109 times that of Earth.

It holds 99.8 percent of the solar system's mass and is roughly 109 times the diameter of the Earth — about one million Earths could fit inside the sun.

Though massive, the Sun still isn’t as large as other types of stars. It’s classified as a yellow dwarf star.

DISTANCE TO EARTH

92.96 M

miles

SURFACE TEMPERATURE

5,778

Kelvin

STAR SYSTEM

Solar System

1672

Giovanni Cassini and Jean Richer determined the distance to Mars and were thereby able to calculate the distance to the Sun.

1800

William Herschel discovered infrared radiation beyond the red part of the solar spectrum.

1980

The Solar Maximum Mission was launched by NASA.

2018

Solar Probe travels within 26.55 million miles of the Sun to become the closest spacecraft to the Sun.

The Sun Profile

Age:	4.6 Billion Years
Type:	Yellow Dwarf (G2V)
Diameter:	1,392,684 km
Equatorial Circumference:	4,370,005.6 km
Mass:	1.99 × 10^30 kg (333,060 Earths)
Surface Temperature:	5,500 °C

Size of the Sun

Sun size compared to Earth, Neptune, Uranus, Saturn and Jupiter

Sun Features

Sunspots

Sunspots are areas of the Sun’s surface that appear darker than the surrounding areas, this is because they are cooler. They form in areas of strong magnetic activity that inhibit heat transfer.

Solar Flares

When the magnetic fields near sunspots cross, tangle or are re-organised, an explosion of energy can be released. Intense solar flares can interfere with radio communications on Earth.

Satellites

Name	Distance from Sun	Length of Year	Classification
Mercury	57,909,227 km	88 Earth days	Planet
Venus	108,209,475 km	225 Earth days	Planet
Earth	149,598,262 km	365.24 days	Planet
Mars	227,943,824 km	1.9 Earth years	Planet
Ceres	413,700,000 km	4.6 Earth years	Dwarf Planet
Jupiter	778,340,821 km	11.9 Earth years	Planet
Saturn	1,426,666,422 km	29.5 Earth years	Planet
Uranus	2,870,658,186 km	84.0 Earth years	Planet
Neptune	4,498,396,441 km	164.8 Earth years	Planet
Pluto	5,874,000,000 km	248.0 Earth years	Dwarf Planet
Haumea	6,452,000,000 km	283.3 Earth years	Dwarf Planet
Makemake	6,850,000,000 km	309.9 Earth years	Dwarf Planet
Eris	10,120,000,000 km	560.9 Earth years	Dwarf Planet

History of The Sun

The Sun is by far the largest object in the solar  system. It contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest).

It is often said that the Sun is an "ordinary" star. That's true in the sense that there are many others similar to it. But there are many more smaller stars than larger ones; the Sun is in the top 10% by mass. The median size of stars in our galaxy is probably less than half the mass of the Sun.

The Sun is personified in many mythologies: the Greeks called it Helios and the Romans called it Sol.

The Sun is, at present, about 70% hydrogen and 28% helium by mass everything else ("metals") amounts to less than 2%. This changes slowly over time as the Sun converts hydrogen to helium in its core.

The outer layers of the Sun exhibit differential rotation: at the equator the surface rotates once every 25.4 days; near the poles it's as much as 36 days. This odd behavior is due to the fact that the Sun is not a solid body like the Earth. Similar effects are seen in the gas planets. The differential rotation extends considerably down into the interior of the Sun but the core of the Sun rotates as a solid body.

Conditions at the Sun's core (approximately the inner 25% of its radius) are extreme. The temperature is 15.6 million Kelvin and the pressure is 250 billion atmospheres. At the center of the core the Sun's density is more than 150 times that of water.

 
INTERNAL STRUCTURE AND ATMOSPHERE OF THE SUN

The sun and the atmosphere of the sun are divided into several zones and layers. The solar interior, from the inside out, is made up of the core, radiative zone and the convective zone. The solar atmosphere above that consists of the photosphere, chromosphere, a transition region and the corona. Beyond that is the solar wind, an outflow of gas from the corona.

The core extends from the sun's center to about a quarter of the way to its surface. Although it only makes up roughly 2% of the sun's volume, it is almost 15 times the density of lead and holds nearly half of the sun's mass.

Next is the radiative zone, which extends from the core to 70% of the way to the sun's surface, making up 32 % of the sun's volume and 48% of its mass. Light from the core gets scattered in this zone, so that a single photon often may take a million years to pass through.

The convection zone reaches up to the sun's surface, and makes up 66% of the sun's volume but only a little more than 2% of its mass. Roiling "convection cells" of gas dominate this zone. Two main kinds of solar convection cells exist — granulation cells about 600 miles (1,000 kilometers) wide and supergranulation cells about 20,000 miles (30,000 km) in diameter.

The photosphere is the lowest layer of the sun's atmosphere, and emits the light we see. It is about 300 miles (500 km) thick, although most of the light comes from its lowest third. Temperatures in the photosphere range from 11,000 F (6,125 C) at the bottom to 7,460 F (4,125 C) at the top. Next up is the chromosphere, which is hotter, up to 35,500 F (19,725 C), and is apparently made up entirely of spiky structures known as spicules typically some 600 miles (1,000 km) across and up to 6,000 miles (10,000 km) high.

PHOTOSPHERE (Surface of the Sun)

The surface of the Sun, called the photosphere, is at a temperature of about 5800 K. Sunspots are "cool" regions, only 3800 K (they look dark only by comparison with the surrounding regions). Sunspots can be very large, as much as 50,000 km in diameter. Sunspots are caused by complicated and not very well understood interactions with the Sun's magnetic field.

A small region known as the chromosphere lies above the photosphere.

The highly rarefied region above the chromosphere, called the corona, extends millions of kilometers into space but is visible only during a total solar eclipse (left). Temperatures in the corona are over 1,000,000 K.

It just happens that the Moon and the Sun appear the same size in the sky as viewed from the Earth. And since the Moon orbits the Earth in approximately the same plane as the Earth's orbit around the Sun sometimes the Moon comes directly between the Earth and the Sun. This is called a solar eclipse; if the alignment is slightly imperfect then the Moon covers only part of the Sun's disk and the event is called a partial eclipse. When it lines up perfectly the entire solar disk is blocked and it is called a total eclipse of the Sun. Partial eclipses are visible over a wide area of the Earth but the region from which a total eclipse is visible, called the path of totality, is very narrow, just a few kilometers (though it is usually thousands of kilometers long). Eclipses of the Sun happen once or twice a year. If you stay home, you're likely to see a partial eclipse several times per decade. But since the path of totality is so small it is very unlikely that it will cross you home. So people often travel half way around the world just to see a total solar eclipse. To stand in the shadow of the Moon is an awesome experience. For a few precious minutes it gets dark in the middle of the day. The stars come out. The animals and birds think it's time to sleep. And you can see the solar corona. It is well worth a major journey.

The Sun's magnetic field is very strong (by terrestrial standards) and very complicated. Its magnetosphere (also known as the heliosphere) extends well beyond Pluto.

The sun won't die for 5 billion years, so why do humans have only 1 billion years left on Earth?

As the Sun matures into a Red Giant, the oceans will boil and Earth will become uninhabitable. Credit: Fsgregs, CC BY-SA

In a few billion years, the sun will become a red giant so large that it will engulf our planet. But the Earth will become uninhabitable much sooner than that. After about a billion years the sun will become hot enough to boil our oceans.

The sun is currently classified as a "main sequence" star. This means that it is in the most stable part of its life, converting the hydrogen present in its core into helium. For a star the size of ours, this phase lasts a little over 8 billion years. Our solar system is just over 4.5 billion years old, so the sun is slightly more than halfway through its stable lifetime.

Even stars die

After 8 billion years of happily burning hydrogen into helium are over, the sun's life gets a little more interesting. Things change because the sun will have run out of hydrogen in its core – all that's left is the helium. The trouble is that the sun's core is not hot or dense enough to burn helium.

In a star, gravitational force pulls all the gases towards the centre. When the star has hydrogen to burn, the creation of helium produces enough outward pressure to balance out the gravitational pull. But when the star has nothing left in the core to burn, gravitational forces take over.

Eventually that force compresses the centre of the star to such a degree that it will start burning hydrogen in a small shell around the dead core, which is still full of helium. As soon as the sun begins to burn more hydrogen, it would be considered a "red giant".

Magnificent coronal mass eruption. Credit: NASA, CC BY

The process of compression in the centre allows the outer regions of the star to expand outwards. The burning hydrogen in the shell around the core significantly increases the brightness of the sun. Because the size of the star has expanded, the surface cools down and goes from white-hot to red-hot. Because the star is brighter, redder and physically larger than before, we dub these stars "red giants".

Earth's fiery demise

It is widely understood that the Earth as a planet will not survive the sun's expansion into a full-blown red giant star. The surface of the sun will probably reach the current orbit of Mars – and, while the Earth's orbit may also have expanded outwards slightly, it won't be enough to save it from being dragged into the surface of the sun, whereupon our planet will rapidly disintegrate.

Life on the planet will run into trouble well before the planet itself disintegrates. Even before the sun finishes burning hydrogen, it will have changed from its present state. The sun has been increasing its brightness by about 10% every billion years it spends burning hydrogen. Increased brightness means an increase in the amount of heat our planet receives. As the planet heats up, the water on the surface of our planet will begin to evaporate.

An increase of the sun's luminosity by 10% over the current level doesn't sound like a whole lot, but this small change in our star's brightness will be pretty catastrophic for our planet. This change is a sufficient increase in energy to change the location of the habitable zone around our star. The habitable zone is defined as the range of distances away from any given star where liquid water can be stable on the surface of a planet.

With a 10% increase of brightness from our star, the Earth will no longer be within the habitable zone. This will mark the beginning of the evaporation of our oceans. By the time the sun stops burning hydrogen in its core, Mars will be in the habitable zone, and the Earth will be much too hot to maintain water on its surface.

How long will the Sun shine?

If our Sun is four and a half billion years old, how much longer will it shine? Stars like our Sun burn for about nine or 10 billion years. So our Sun is about halfway through its life. But don’t worry. It still has about 5,000,000,000—five billion—years to go.

When those five billion years are up, the Sun will become a red giant. That means the Sun will get bigger and cooler at the same time. When that happens, it will be different than the Sun we know today. As a red giant, our Sun will become about 2,000 times brighter than it is now!

        Open Issues

• Is there a causal connection between the Maunder Minimum and the Little Ice Age or was it just a coincidence? How does the variability of the Sun affect the Earth's climate?
• Since all the planets except Pluto orbit the Sun within a few degrees of the plane of the Sun's equator, we know very little about the interplanetary environment outside that plane. The Ulysses mission will provide information about the polar regions of the Sun.
• The corona is much hotter than the photosphere. Why?

Interesting Facts about the Sun

• The Sun is one of the millions of stars in the solar system. It is, however, larger than most (although not the biggest) and a very special star to us. Without the Sun there would be absolutely no life on Earth.
• The Sun is 870,000 miles (1.4 million kilometers) across. This is so big it is hard to imagine, but it would take more than one million Earths to fill the size of the Sun!
• The Sun is so big it takes up 99% of the matter in our solar system. The 1% left over is taken up by planets, asteroids, moons and other matter.
• The Sun is about 4.5 billion years old. It is thought to be halfway through its lifetime. Stars get bigger as they get older.
• As the Sun ages, it will get bigger. When this happens, it will consume some of the things close to it, and this includes Mercury, Venus and maybe even Earth and Mars. Luckily this is billions of years in the future.
• The Sun is the centre of the solar system.
• The Sun is 92.96 million miles (149.6 kilometers) away from Earth.
• The Sun is made of a ball of burning gases. These gases are 92.1% hydrogen and 7.8% helium.
• The sunlight we see on Earth left the Sun 8 minutes ago. This is the length of time it takes for the light to travel the distance between the Sun and the Earth.
• When the moon goes around the Earth, it sometimes finds itself between the Earth and the Sun. This is called a solar eclipse and makes the Earth dark whilst the moon shuts out most of the Sun’s light. This only lasts for a couple of hours while the moon continues its rotation and moves out of the way of the sun.
• In ancient astronomy, it was thought that the Sun moved. People believed that the Earth stayed still and the Sun rotated around it.
• About 2000 years ago some began to think it was the Sun that stays still whilst the planets make a path around it. This only became an accepted theory around the 1600s when Isaac Newton proposed the sun-centric solar system.
• The Sun is almost a perfect sphere. It is the closest thing to a sphere found in nature with only a 6.2 mile (10 kilometres) difference between its vertical and horizontal measurements.
• The Sun’s core is extremely hot! An unthinkable 13,600,000 degrees Celcius!
• The Sun has a very big magnetic field. It is the most powerful magnetic field in the whole solar system. This field is regenerating itself, but scientists are unsure how.
• The Sun produces solar winds. These are a stream of particles from the Sun that stream out into space. This is why planets atmospheres are so important. They protect the planet from these solar winds.
• The Sun rotates but not as Earth does. On Earth, the planet is rotating at the same speed no matter where you are. The Sun does not rotate like a solid object and is spinning faster at its equator than it is at its poles. It is complicated to say how fast the Sun is spinning but depending whereabouts on the Sun you are looking at it takes between 24 and 38 days to spin around.
• The Sun has been both worshipped and feared throughout history by a variety of cultures.

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