My Science School

 As well as heat and light, the sun blasts out special particles called solar wind. When these get trapped by Earth’s magnetic field near the poles they can create spectacular light shows, called auroras. Even though auroras are best seen at night, they are actually caused by the sun. The sun sends us more than heat and light; it sends lots of other energy and small particles our way. The protective magnetic field around Earth shields us from most of the energy and particles, and we don’t even notice them.

But the sun doesn’t send the same amount of energy all the time. There is a constant streaming solar wind and there are also solar storms. During one kind of solar storm called a coronal mass ejection, the sun burps out a huge bubble of electrified gas that can travel through space at high speeds.

When a solar storm comes toward us, some of the energy and small particles can travel down the magnetic field lines at the north and south poles into Earth’s atmosphere.

There, the particles interact with gases in our atmosphere resulting in beautiful displays of light in the sky. Oxygen gives off green and red light. Nitrogen glows blue and purple.

 

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The sun is so ginormous that all of the planets of the solar system could fit inside it hundreds of times over. The 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).

It may be the biggest thing in this neighbourhood, 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.

 

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Located at the centre of the solar system is the sun. It is a star, like the ones you see in the night sky. A burning ball of gas, made of mostly hydrogen and helium, it provides us with the heat we need to survive. The sun is doing massive that its gravity – the force that pulls things together - keeps the planets in orbit around it. Like other stars, our sun is basically a large ball of gas that is 91% hydrogen and 8.9% helium. The sun’s mass is around 70.6% hydrogen and 27.4% helium.

While a majority of our sun may be gas it does have six distinct regions: the core, the radiative zone, and the convective zone in the interior, the visible surface, called the photosphere; the chromospheres; and the outermost region, the corona.

The sun is held together due to gravitational attraction that produces an intense temperature and pressure at the core. The core’s temperature is about 27 million degrees F/15 million degrees C.

This is hot enough to continue the constant state of thermonuclear fusion, a process where atoms combine to create larger atoms and in that process they release huge amounts of energy.

Our star: The Sun is 150 million kilometers (93 million miles) away from the Earth (this distance varies slightly throughout the year, because the Earth’s orbit is an ellipse and not a perfect circle). The Sun is an average star – there are other stars which are much hotter or much cooler, and intrinsically much brighter or fainter. However, since it is by far the closest star to the Earth, it looks bigger and brighter in our sky than any other star. Energy is constantly being generated deep within the sun. It can take up to 100,000 years for energy to reach the surface, but then it only take 8 minutes to reach the earth!

Solar flare: Huge eruptions from the surface of the sun are called solar prominences. They form loops because of the Sun’s invisible magnetic field. Flares are closely associated with the ejection of plasmas and particles through the Sun's corona into outer space; flares also copiously emit radio waves. If the ejection is in the direction of the Earth, particles associated with this disturbance can penetrate into the upper atmosphere (the ionosphere) and cause bright auroras, and may even disrupt long range radio communication. It usually takes days for the solar plasma ejecta to reach Earth. Flares also occur on other stars, where the term stellar flare applies. High-energy particles, which may be relativistic, can arrive almost simultaneously with the electromagnetic radiations.

Sunspots: Dark patches that appear on the surface of the sun are called sunspots. They are cooler areas that usually last for a few weeks. Individual sunspots or groups of sunspots may last anywhere from a few days to a few months, but eventually decay. Sunspots expand and contract as they move across the surface of the Sun, with diameters ranging from 16 km (10 mi) to 160,000 km (100,000 mi). Larger sunspots can be visible from Earth without the aid of a telescope. They may travel at relative speeds, or proper motions, of a few hundred meters per second when they first emerge.

 

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The solar system is located in the Milky Way, a huge spiral galaxy containing billions of stars. They are grouped in “arms” that spiral outwards. All of the stars are travelling around a point at the centre. The Milky Way does not sit still, but is constantly rotating. As such, the arms are moving through space. The sun and the solar system travel with them. The solar system travels at an average speed of 515,000 mph (828,000 km/h). Even at this rapid speed, the solar system would take about 230 million years to travel all the way around the Milky Way. Scientists think there is a super massive black hole located there that sucks in anything that gets too close to it.

The Night sky: The Milky Way used to be visible on every clear, moonless night, everywhere in the world. Today, however, most people live in places where it's impossible to see the Milky Way because of widespread light pollution caused by lights left on all night long. Seeing the Milky Way requires a special effort for most people, but its well worth the trouble.

To see the Milky Way, you'll need to travel far from any city, to a wilderness area. Even in rural farming country, there are still a lot of bright lighting fixtures that wipe out the night sky. 

Black hole: Tucked inside the very center of the galaxy is a monstrous black hole, billions of times as massive as the sun. This supermassive black hole may have started off smaller, but the ample supply of dust and gas allowed it to gorge itself and grow into a giant. The greedy glutton also consumes whatever stars it can get a grip on. Although black holes cannot be directly viewed, scientists can see their gravitational effects as they change and distort the paths of the material around it, or as they fire off jets. Most galaxies are thought to have a black hole in their heart.

 

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The solar system is made up of our star called the sun, and everything that travels, or orbits, around it. This includes eight planets and their moons, dwarf planets, asteroids, comets, and smaller bits of rock and dust. The solar system is one of many solar systems that exist in the Universe.

Beyond our own solar system, there are more planets than stars in night sky. So far, we have discovered thousands of planetary systems orbiting other stars in the Milky Way, with more planets being found all the time. Most of the hundreds of billions of stars in our galaxy are thought to have planets of their own, and the Milky Way is but one of perhaps 100 billion galaxies in the universe.

While our planet is in some ways a mere speck in the vast cosmos, we have a lot of company out there. It seems that we live in a universe packed with planets — a web of countless stars accompanied by families of objects, perhaps some with life of their own.

Gas planets: The four outer planets – Jupiter, Saturn, Uranus, and Neptune –are the largest planets in the Solar System. They are mostly made of gas and spacecraft are unable to land on them. Jupiter is the largest planet in our solar system. It has a radius almost 11 times the size of Earth. It has 50 known moons and 17 waiting to be confirmed, according to NASA.  Saturn is about nine times Earth's radius and is characterized by large rings; how they formed is unknown. It has 53 known moons and nine more awaiting confirmation, according to NASA. Uranus has a radius about four times that of Earth's. The planet has 27 moons, and its atmosphere is made up of hydrogen, helium and methane, according to NASA. Neptune also has a radius about four times that of Earth's. It has 13 confirmed moons and an additional one awaiting confirmation, according to NASA.

Asteroids:  Asteroids are lumps of rock and metal left over from when the solar system first formed. Most can be found in the asteroid belt, which is located between the planets Mars and Jupiter. There are millions of asteroids in our Solar System. Scientists estimate the asteroid belt has between 1.1 and 1.9 million asteroids larger than 1 kilometer (0.6 mile) in diameter, and millions of smaller ones. Most of the undiscovered asteroids are likely the smaller ones (less than 100 km across) which are more difficult to detect. Some astronomers estimate there could be 150 million asteroids in the entire Solar System.

Rocky planets: Closest to the sun are the four rocky planets-Mercury, Venus, Earth and Mars. They all began their existence in the same way, but over time became very different worlds. They are the closest four planets to the Sun. They are made of rocks and metals. They have a solid surface and a core which is mainly made of iron. They are much smaller than the gas planets and rotate more slowly.

Super-sized: The solar system is so big that if the sun were the size of a basketball, the earth would be the size of a sesame seed – and it would be located more than 25 m (80 ft) away! The Earth is the largest of the four inner, rocky planets in our Solar System, at more than 12,000 km in diameter. But even at this size, Earth is dwarfed by all four of the gas giant planets, which range in size from Neptune (at nearly 4 times the size and 17 times the mass of Earth) all the way up to our Solar System's giant, Jupiter, with more than 11 times the Earth's diameter and over 300 times its mass.

Dwarf Planets: Dwarf planets, such as Pluto, also travel around the sun; these worlds are smaller than the other planets. Scientists think there may be dozens of undiscovered dwarf planets hiding in the solar system. It is possible that there are another 40 known objects in the solar system that could be rightly classified as dwarf planets. Estimates are that up to 200 dwarf planets may be found when the entire region known as the Kuiper belt is explored, and that the number may exceed 10,000 when objects scattered outside the Kuiper belt are considered.

 

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