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Big stars like supergiants and hypergiants have shorter lives as they consume their fuel at a faster rate than smaller stars. As these massive stars die they explode as massive bright supernova.

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With a mean average distance of 150 million kilometres from Earth and with light travelling at 300,000 kilometres per second, dividing one by the other gives us an approximate time of 500 seconds, or eight minutes and 20 seconds. Although this energy reaches Earth in a few minutes, it will already have taken millions of years to travel from the Sun’s core to its surface.

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Because the Earth travels on an elliptical orbit around the Sun, the distance between the two bodies varies from 147 to 152 million kilometres. The distance between the Earth and the Sun is called an Astronomical Unit (AU).

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At around 4.5 billion years old, the Sun has already burned off about half of its store of Hydrogen. It has enough left to continue to burn Hydrogen for approximately another 5 billion years. The Sun is currently a type of star known as a Yellow Dwarf

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Solar flares occur when magnetic energy is released by the Sun during magnetic storms, which we see as sunspots. In sunspots, the magnetic lines are twisted and they spin, much like a tornado would on Earth.

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This is a stream of charged particles, which travels through the Solar System at approximately 450 kilometres per second. Solar wind occurs where the magnetic field of the Sun extends into space instead of following its surface.

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tars are luminous spheres made of plasma – a superheated gas threaded with a magnetic field. They are made mostly of hydrogen, which stars fuse in their cores. That process releases energy, which pushes against the weight of the outer layers of the star and keeps it stable. The energy is also released as heat and light, which are radiated out to space. Stars are the main components of galaxies, and were among the first objects to form in the early universe. The closest star to Earth is the Sun.

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Star formation happens in clouds of interstellar gas and dust called “nebulae”. These clouds are mostly molecular hydrogen, and are often referred to as HII regions. The process begins when the cloud is nudged into a spinning motion, perhaps by a shock wave from a nearby supernova explosion. Clumps begin to form, and they get hotter and hotter as they gain more mass. When the temperature inside such a “young stellar object” reaches 10 million degrees Celsius, a process called “nuclear fusion” ignites, and a star is born.

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When smaller stars such as red dwarfs or red giants use up all their fuel and nuclear fusion slows they start to die, and become small “white dwarf” stars which will emit white light until they finally darken into "black dwarfs".

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he stars have played a very important role throughout human history. They have formed part of religious practices, been grouped into constellations, used in astrology star signs, helped to design calendars and were very important navigational tools for early explorations across land and seas.

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Stars are huge celestial bodies made mostly of hydrogen and helium that produce light and heat from the churning nuclear forges inside their cores. Aside from our sun, the dots of light we see in the sky are all light-years from Earth. They are the building blocks of galaxies, of which there are billions in the universe. It’s impossible to know how many stars exist, but astronomers estimate that in our Milky Way galaxy alone, there are about 300 billion.

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When all the Hydrogen has been burned, the Sun will continue for about 130 million more years, burning Helium, during which time it will expand to the point that it will engulf Mercury and Venus and the Earth. At this stage it will have become a red giant

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At the Sun’s core, energy is generated by nuclear fusion, as Hydrogen converts to Helium. Because hot objects generally expand, the Sun would explode like a giant bomb if it weren’t for its enormous gravitational force. The temperature on the surface of the Sun is closer to 5,600 degrees Celsius.

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There is only a 10 kilometre difference in its polar diameter compared to its equatorial diameter. Considering the vast expanse of the Sun, this means it is the closest thing to a perfect sphere that has been observed in nature

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If a hollow Sun was filled up with spherical Earths then around 960,000 would fit inside. On the other hand if these Earths were squished inside with no wasted space then around 1,300,000 would fit inside. The Sun’s surface area is 11,990 times that of the Earth’s.

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Red supergiants, such as Betelgeuse in the constellation Orion make our Sun look small, 20x its mass, and 1,000x larger. Red hypergiants such as the largest known star VY Canis Majoris are even bigger, over 1,800x the size of the Sun.

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The most common star, are red dwarfs. They are less than half the size and mass of our Sun, and burn their fuel very slowly so live longer than any other type of star, over 100 billion years. Red dwarfs are cooler than most stars and so shine less, eventually getting dimmer they do not explode.

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Each galaxy contains hundreds of billions of stars and there is estimated to be over 100 billion galaxies in the universe. So the total number of stars in the universe is mind boggling, estimated to be at least 70 sextillion and possibly as high as 300 sextillion, that's 300,000,000,000,000,000,000,000!!!!!

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When stars die, all the elements they created in their cores are scattered to space, to become part of interstellar clouds of gas and dust. Those chemical elements are seed materials for new generations of stars, planets, and life.

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Stars may “live” longer than humans do – ranging from tens of millions to billions of years – but eventually, they, too, come to the ends of their lives. The manner of a star’s death depends on the mass it had after it finished forming. Stars with masses similar to the Sun die much differently from stars that have 7 or more solar masses. Yet, the process of star death starts out the same for all stars: they run out of fuel. For much of its life, a star fuses hydrogen to make helium. When that runs out, then the star fuses helium, and then carbon. Each level of fusion releases more energy, which heats up the star.

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In sun-like stars, the increased heating causes them to swell up to become giant stars. Any nearby planets are enveloped by the expanding star. Eventually the outer stellar atmosphere blows away, creating an expanding cloud of gas around the star. This is called a “planetary nebula”. What’s left of the star itself slowly shrinks and cools. Eventually, the dying star becomes a white dwarf.

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Stars that are much more massive than the Sun continue the fusion process until they reach a point where the core collapses. The outer layers also collapse onto the core and then rebound out to space in a catastrophic explosion called a supernova.

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Astronomers sort stars into categories according to their spectral characteristics – that is the information contained in the light they radiate. The general categories are O, B, A, F, G, K, M, R, N, T, Y, and group stars (and stellar objects) by their temperatures, luminosities, and colors. For example, O- and B-type stars are blue-looking and are generally among the hottest stars – between 30-40,000 Kelvin. A-type stars are blue-white and have temperatures around 9,500 K. The F-type stars are white and are no hotter than 7,500 K. The G-type stars are yellow-white and around 5,900-6,000 K. At the cooler end of the spectrum, the K and M stars are orange and red, respectively, and range from 5,300 to 3,800 degrees Kelvin.

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The coolest stellar objects are the R, N, T, and Y stars, which include the brown dwarfs (objects too hot to be planets and too cool to be stars).

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Astronomers further classify stars by such characteristics as their rotation rates, and metallicity (how many elements heavier than hydrogen and helium they contain). In addition, they use some other specific information about their luminosity or the existence of exotic chemical elements in the star’s atmosphere.

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The most famous star in our sky is the Sun, the source of the heat and light that powers the solar system. It’s a G-type star that formed some 4.6 billion years ago. The Sun is a yellow-white dwarf that will continue its hydrogen-burning phase (that is, “live” on the Main Sequence) for another 5 or so billion years. Then, it will start to fuse helium, which will heat up the Sun and cause it to expand. The Sun may form a planetary nebula, and eventually will shrink down to become a white dwarf. It will continue cooling for another 10-15 billion years.

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Stars are plotted on a color-luminosity chart called the Hertzsprung-Russell Diagram. The stars in their hydrogen-burning phase fall into a curving line called the Main Sequence. White dwarfs, giants, and supergiants all fall outside this sequence, showing that they are fusing other elements and thus are in advanced stages of evolution.

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Star birth can take millions of years and create families of stars. Astronomers see examples of star formation in nebulae throughout our own Milky Way Galaxy and in many other galaxies. The most famous and closest stellar nursery to Earth is the Orion Nebula, which lies about 1,500 light-years away and is visible to observers from November through April each year.