There are 100-400 billion stars in the Milky Way galaxy. When we look up at the night sky we see the light from thousands of stars. The closest of which, Proxima Centauri, is trillions of kilometres from Earth. It can be hard to imagine, an object so far away, shines so bright that we can see it from Earth. But something much more incredible is the fact that one of these stars is at the very heart of our Solar System - the Sun. The Sun gives us day - the ultimate light source.
1: The Sun has many names
The Sun’s name comes from an ancient language called Proto-Germanic. The word for Sun was Sunnōn, and this word later became Sunne in Old English. Ancient peoples thought the Sun was a god and gave the Sun special names, such as Ra, the Sun god from ancient Egypt and Surya, the name of the Sun god in Hinduism. The ancient Greeks called the Sun Helios, a name we still use today.
2: The Sun contains more than 99% of the mass of the Solar System
The Sun is the largest and most massive object in our solar system. It has a diameter of about 1.4 million kilometres, which is 109 times larger than the Earth's diameter. It also has a mass of about 1.989 x 10^30 kilograms, which is 333,000 times more than the Earth's mass.
3: The Sun is a giant ball of gas
The Sun is made of hydrogen (70%) and helium (25%), with small amounts of other elements such as oxygen, carbon, neon, iron, and others. These elements came from the cores of ancient stars that exploded as supernovas before the Sun was born. However, because the Sun is so hot, most of the gas converts to the fourth state of matter - Plasma.
4: The Sun is halfway through its lifecycle
The Sun is a yellow dwarf star, which means it belongs to the main sequence of stars that fuse hydrogen into helium in their cores. The Sun is about 4.5 billion years old, which means it is halfway through its lifetime. In another 5 billion years, the Sun will run out of hydrogen and start fusing helium into heavier elements. This will cause the Sun to expand and become a red giant star, swallowing Mercury, Venus, and possibly Earth.
5: The Sun is a giant battery
The Sun produces an enormous amount of energy through nuclear fusion in its core. Every second, the Sun converts about 600 million tons of hydrogen into 596 million tons of helium and 4 million tons of energy in the form of gamma rays. This energy travels from the core to the surface through radiation and convection, taking about 170,000 years to reach the photosphere.
6: The Sun is white
The photosphere is the visible surface of the Sun that we see from Earth. It has a temperature of about 5,500 degrees celsius, which is cooler than the core's temperature of about 15 million degrees Celsius (27 million degrees Fahrenheit). The photosphere emits light in all colours, but it appears white to our eyes because all the colours are mixed together.
7: The Sun is bumpy
The photosphere is not smooth and uniform but rather covered with granules and Sunspots. Granules are bright areas that are hotter than their surroundings and last for about 10 minutes. They are caused by convection currents that bring hot plasma from the interior to the surface. Sunspots are dark areas that are cooler than their surroundings and last for days or weeks. They are caused by magnetic fields that inhibit convection and reduce the temperature.
7: The Sun has a powerful magnetic field
The Sun has a powerful magnetic field that extends throughout the solar system and influences its environment. The magnetic field is generated by electric currents in the plasma that flows inside the Sun. The magnetic field changes over time and reverses its polarity every 11 years, creating a cycle of solar activity.
8: The Sun is like an onion - it has layers
The Suns atmosphere, consists of three layers: the photosphere, the chromosphere, and the corona. The chromosphere is a thin layer above the Suns photosphere. It emits reddish light during solar eclipses. The corona is a much thicker layer above the chromosphere that emits white light and extends millions of kilometres into space. The corona is much hotter than the photosphere, reaching temperatures of over a million degrees celsius.
9: Solar activity can affect us here on Earth
Solar activity produces various phenomena that can affect us on Earth, such as:
solar flares
coronal mass ejections
solar wind; and
auroras.
Solar flares are sudden bursts of intense radiation. These flares can affect radio communications and satellites.
Coronal mass ejections are large eruptions of plasma that can cause geomagnetic storms and can disrupt power grids.
Solar wind is a stream of charged particles that flow from the corona into space at high speeds.
Auroras are colourful lights in the sky that are caused by the solar wind interacting with Earth's magnetic field and atmosphere.
10: The Sun rotates at different speeds
The Sun is not a solid ball of rock, but a giant ball of plasma – super-hot, electrically charged gas. This means that different parts of the Sun can rotate at different speeds. At its equator, it takes about 25 days to complete one rotation, while at its poles it takes about 36 days. The Sun orbits around the galactic centre at a speed of about 220 kilometres per second (137 miles per second), taking about 230 million years to complete one revolution. The Sun is currently about 30,000 light-years away from the galactic centre.
11: Our Sun is a G class star - not to hot but not to cold.
The Sun is the only star in our solar system, but it is not the only star in the universe. There are billions of stars in our galaxy and billions of galaxies in the observable universe.
Stars are categorized by their spectra (the elements that they absorb) and their temperature.
There are seven main types of stars, named by letters from O to M. O stars are the hottest and most massive, while M stars are the coolest and least massive. The types are further divided by numbers from 0 to 9, with higher numbers indicating cooler stars.
Our sun is a G type star. G type stars make up about 7.5 percent of the stars within our galaxy.
The Sun is medium in size, with a radius of around 700,000 kilometres. The largest known star is UY Scuti, a M class star, which has a radius of around 1.2 billion kilometres. The smallest is OGLE-TR-122b at around 167,000 kilometres.
There are stars that are much bigger, hotter, and brighter than the Sun, such as Alnitak, an O class star that is five times hotter than the Sun. There are also stars that are much smaller, cooler, and dimmer than the Sun, such as Proxima Centauri, a M class red dwarf.
The Sun belongs to the Population I generation, which means it has a higher metallicity (proportion of elements heavier than hydrogen and helium) than older stars.
12: The Sun is the source of life on Earth
It provides the energy and heat needed for photosynthesis, weather, climate, and seasons. Photosynthesis is how plants and some bacteria use Sunlight to convert water and carbon dioxide into oxygen and sugar. Weather is the state of the atmosphere at a given time and place, influenced by factors such as temperature, pressure, humidity, wind, and precipitation. The climate is the average weather over a long period, determined by factors such as latitude, altitude, ocean currents, and greenhouse gases. Seasons are the changes in weather and daylight hours that occur due to the tilt of Earths' axis and its orbit around the Sun.
13: The sun gives us vitamin D
The Sun is essential for human health and well-being, as it provides vitamin D, regulates circadian rhythms, boosts mood, and prevents infections. Vitamin D is a nutrient that helps the body absorb calcium and phosphorus, which are important for bone health. Circadian rhythms are the natural cycles of sleep and wakefulness that are synchronized with the day-night cycle. Mood is the emotional state that affects how we feel and behave. Infections are diseases caused by microorganisms such as bacteria, viruses, fungi, and parasites.
14: We've sent a probe to touch the Sun
In 2018 NASA launched the Parker Solar Prode. The Parker probes mission is to explore the Sun’s atmosphere, or corona. It is the first mission to fly so close to the Sun, about 6.5 million kilometers from its surface. The probe is
breaking records for speed and temperature. It can travel faster than 500,000 kph and withstand temperatures of nearly 1,377 celsius. The probe has a special shield to protect it from the Sun’s intense radiation. The Parker probe is helping scientists learn more about our star and its effects on our solar system. You can read more about the Parker probe on NASA’s website or Wikipedia.
15: It rains on the Sun
The Sun produces giant loops of hot plasma that rise from its surface and extend into its outer atmosphere. These loops are called prominences, and they can break apart and release plasma that falls back to the surface as rain. The plasma is made of electrically charged gas that can reach temperatures of over a million degrees Celsius, much hotter than the Sun’s surface. This is called coronal rain.
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