The Sun for Kids - Fun Facts & Pictures All About the Sun, Solar Cycles, and Solar Space Missions

All stars die eventually! Stars die when the supply of hydrogen that they burn for energy runs out. Usually, this takes billions and billions of years. Class G stars, like the Sun, live for about 10 billion years. Right now, the Sun is about 4. That means that it has 5. When it dies, it will likely disintegrate the Earth!

Earth's Sun: Facts About the Sun's Age, Size and History

Compared to other stars, the Sun is about medium sized. The Earth just looks like a tiny dot! Remember, Kelvin is a unit of measurement that scientists use to measure temperature. It would be impossible for you to go close to the surface of the Sun because it would be way too hot! It gets even hotter on the inside. Where does all this heat come from? The nuclear fusion that happens in the center of a star releases lots and lots of energy.

This energy releases as heat and is what makes stars so hot. Some parts are slightly cooler than others.

Fun Facts About Our Sun

Compared to other stars, the Sun is medium-sized. You could fit about 1 million Earths inside of it! Compare the sun to all the planets in our solar system. Despite its typical whiteness, most people mentally picture the Sun as yellow; the reasons for this are the subject of debate.

The Sun is composed primarily of the chemical elements hydrogen and helium. At this time in the Sun's life, they account for The Sun's original chemical composition was inherited from the interstellar medium out of which it formed. Originally it would have contained about Since the Sun formed, the main fusion process has involved fusing hydrogen into helium. Over the past 4. The proportions of metals heavier elements is unchanged. Heat is transferred outward from the Sun's core by radiation rather than by convection see Radiative zone below , so the fusion products are not lifted outward by heat; they remain in the core [68] and gradually an inner core of helium has begun to form that cannot be fused because presently the Sun's core is not hot or dense enough to fuse helium.

In the future, helium will continue to accumulate in the core, and in about 5 billion years this gradual build-up will eventually cause the Sun to exit the main sequence and become a red giant. The chemical composition of the photosphere is normally considered representative of the composition of the primordial Solar System.

These meteorites are thought to retain the composition of the protostellar Sun and are thus not affected by settling of heavy elements. The two methods generally agree well. In the s, much research focused on the abundances of iron-group elements in the Sun.

The first largely complete set of oscillator strengths of singly ionized iron-group elements were made available in the s, [73] and these were subsequently improved. Various authors have considered the existence of a gradient in the isotopic compositions of solar and planetary noble gases , [75] e.

Prior to , it was thought that the whole Sun has the same composition as the solar atmosphere.

Recent analysis of SOHO mission data favors a faster rotation rate in the core than in the radiative zone above. The remainder of the Sun is heated by this energy as it is transferred outwards through many successive layers, finally to the solar photosphere where it escapes into space as sunlight or the kinetic energy of particles. However, the large power output of the Sun is mainly due to the huge size and density of its core compared to earth and objects on earth , with only a fairly small amount of power being generated per cubic metre.

Theoretical models of the Sun's interior indicate a power density, or energy production, of approximately The fusion rate in the core is in a self-correcting equilibrium: From the core out to about 0. The radiative zone and the convective zone are separated by a transition layer, the tachocline. This is a region where the sharp regime change between the uniform rotation of the radiative zone and the differential rotation of the convection zone results in a large shear between the two—a condition where successive horizontal layers slide past one another.

The Sun's convection zone extends from 0. In this layer, the solar plasma is not dense enough or hot enough to transfer the heat energy of the interior outward via radiation. Instead, the density of the plasma is low enough to allow convective currents to develop and move the Sun's energy outward towards its surface. Material heated at the tachocline picks up heat and expands, thereby reducing its density and allowing it to rise. As a result, an orderly motion of the mass develops into thermal cells that carry the majority of the heat outward to the Sun's photosphere above.

Once the material diffusively and radiatively cools just beneath the photospheric surface, its density increases, and it sinks to the base of the convection zone, where it again picks up heat from the top of the radiative zone and the convective cycle continues.

At the photosphere, the temperature has dropped to 5, K and the density to only 0. The thermal columns of the convection zone form an imprint on the surface of the Sun giving it a granular appearance called the solar granulation at the smallest scale and supergranulation at larger scales. Turbulent convection in this outer part of the solar interior sustains "small-scale" dynamo action over the near-surface volume of the Sun. The visible surface of the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light.

Because the upper part of the photosphere is cooler than the lower part, an image of the Sun appears brighter in the center than on the edge or limb of the solar disk, in a phenomenon known as limb darkening. During early studies of the optical spectrum of the photosphere, some absorption lines were found that did not correspond to any chemical elements then known on Earth. In , Norman Lockyer hypothesized that these absorption lines were caused by a new element that he dubbed helium , after the Greek Sun god Helios. Twenty-five years later, helium was isolated on Earth.

During a total solar eclipse , when the disk of the Sun is covered by that of the Moon, parts of the Sun's surrounding atmosphere can be seen. It is composed of four distinct parts: The chromosphere, transition region, and corona are much hotter than the surface of the Sun. Rather, it forms a kind of nimbus around chromospheric features such as spicules and filaments , and is in constant, chaotic motion. The corona is the next layer of the Sun.

A flow of plasma outward from the Sun into interplanetary space is the solar wind. The heliosphere , the tenuous outermost atmosphere of the Sun, is filled with the solar wind plasma. The solar wind travels outward continuously through the heliosphere, [] [] forming the solar magnetic field into a spiral shape, [] until it impacts the heliopause more than 50 AU from the Sun. In December , the Voyager 1 probe passed through a shock front that is thought to be part of the heliopause.

High-energy gamma-ray photons initially released with fusion reactions in the core are almost immediately absorbed by the solar plasma of the radiative zone, usually after traveling only a few millimeters. Re-emission happens in a random direction and usually at a slightly lower energy. With this sequence of emissions and absorptions, it takes a long time for radiation to reach the Sun's surface.

Because energy transport in the Sun is a process that involves photons in thermodynamic equilibrium with matter, the time scale of energy transport in the Sun is longer, on the order of 30,, years. This is the time it would take the Sun to return to a stable state, if the rate of energy generation in its core were suddenly changed. Neutrinos are also released by the fusion reactions in the core, but, unlike photons, they rarely interact with matter, so almost all are able to escape the Sun immediately. For many years measurements of the number of neutrinos produced in the Sun were lower than theories predicted by a factor of 3.

• Our Sun - Our Solar System - Astronomy for Kids - Kids Know It.
• More help, more resources, more learning..
• Le colonel Chabert - Texte intégral (Classique t. 1009) (French Edition).
• Vanini Vanini (Spanish Edition).

This discrepancy was resolved in through the discovery of the effects of neutrino oscillation: The Sun has a magnetic field that varies across the surface of the Sun. Its polar field is 1—2 gauss 0. The magnetic field also varies in time and location. The quasi-periodic year solar cycle is the most prominent variation in which the number and size of sunspots waxes and wanes. Sunspots are visible as dark patches on the Sun's photosphere , and correspond to concentrations of magnetic field where the convective transport of heat is inhibited from the solar interior to the surface.

As a result, sunspots are slightly cooler than the surrounding photosphere, and, so, they appear dark. At a typical solar minimum , few sunspots are visible, and occasionally none can be seen at all. Those that do appear are at high solar latitudes. The largest sunspots can be tens of thousands of kilometers across. An year sunspot cycle is half of a year Babcock —Leighton dynamo cycle, which corresponds to an oscillatory exchange of energy between toroidal and poloidal solar magnetic fields.

At solar-cycle maximum , the external poloidal dipolar magnetic field is near its dynamo-cycle minimum strength, but an internal toroidal quadrupolar field, generated through differential rotation within the tachocline, is near its maximum strength. At this point in the dynamo cycle, buoyant upwelling within the convective zone forces emergence of toroidal magnetic field through the photosphere, giving rise to pairs of sunspots, roughly aligned east—west and having footprints with opposite magnetic polarities.

The magnetic polarity of sunspot pairs alternates every solar cycle, a phenomenon known as the Hale cycle. During the solar cycle's declining phase, energy shifts from the internal toroidal magnetic field to the external poloidal field, and sunspots diminish in number and size. At solar-cycle minimum , the toroidal field is, correspondingly, at minimum strength, sunspots are relatively rare, and the poloidal field is at its maximum strength.

With the rise of the next year sunspot cycle, differential rotation shifts magnetic energy back from the poloidal to the toroidal field, but with a polarity that is opposite to the previous cycle. The process carries on continuously, and in an idealized, simplified scenario, each year sunspot cycle corresponds to a change, then, in the overall polarity of the Sun's large-scale magnetic field. The solar magnetic field extends well beyond the Sun itself. The electrically conducting solar wind plasma carries the Sun's magnetic field into space, forming what is called the interplanetary magnetic field.

As a result, the outward-flowing solar wind stretches the interplanetary magnetic field outward, forcing it into a roughly radial structure. For a simple dipolar solar magnetic field, with opposite hemispherical polarities on either side of the solar magnetic equator, a thin current sheet is formed in the solar wind.

The Sun's magnetic field leads to many effects that are collectively called solar activity. Solar flares and coronal-mass ejections tend to occur at sunspot groups. Slowly changing high-speed streams of solar wind are emitted from coronal holes at the photospheric surface. Both coronal-mass ejections and high-speed streams of solar wind carry plasma and interplanetary magnetic field outward into the Solar System. Solar activity is thought to have played a large role in the formation and evolution of the Solar System. With solar-cycle modulation of sunspot number comes a corresponding modulation of space weather conditions, including those surrounding Earth where technological systems can be affected.

Long-term secular change in sunspot number is thought, by some scientists, to be correlated with long-term change in solar irradiance, [] which, in turn, might influence Earth's long-term climate. This coincided in time with the era of the Little Ice Age , when Europe experienced unusually cold temperatures. A recent theory claims that there are magnetic instabilities in the core of the Sun that cause fluctuations with periods of either 41, or , years. These could provide a better explanation of the ice ages than the Milankovitch cycles. The Sun today is roughly halfway through the most stable part of its life.

It has not changed dramatically for over four billion [a] years, and will remain fairly stable for more than five billion more. However, after hydrogen fusion in its core has stopped, the Sun will undergo dramatic changes, both internally and externally. The Sun formed about 4. This indicates that one or more supernovae must have occurred near the location where the Sun formed.

A shock wave from a nearby supernova would have triggered the formation of the Sun by compressing the matter within the molecular cloud and causing certain regions to collapse under their own gravity. Much of the mass became concentrated in the center, whereas the rest flattened out into a disk that would become the planets and other Solar System bodies. Gravity and pressure within the core of the cloud generated a lot of heat as it accreted more matter from the surrounding disk, eventually triggering nuclear fusion. Thus, the Sun was born. HD and HD are hypothesized stellar sibling of the Sun, having formed in the same molecular cloud.

The Sun is about halfway through its main-sequence stage, during which nuclear fusion reactions in its core fuse hydrogen into helium. Each second, more than four million tonnes of matter are converted into energy within the Sun's core, producing neutrinos and solar radiation. At this rate, the Sun has so far converted around times the mass of Earth into energy, about 0. The Sun will spend a total of approximately 10 billion years as a main-sequence star.

The core is therefore shrinking, allowing the outer layers of the Sun to move closer to the centre and experience a stronger gravitational force, according to the inverse-square law. This stronger force increases the pressure on the core, which is resisted by a gradual increase in the rate at which fusion occurs. This process speeds up as the core gradually becomes denser. The Sun does not have enough mass to explode as a supernova. Instead it will exit the main sequence in approximately 5 billion years and start to turn into a red giant.

Even before it becomes a red giant, the luminosity of the Sun will have nearly doubled, and Earth will receive as much sunlight as Venus receives today. Once the core hydrogen is exhausted in 5. It will then expand more rapidly over about half a billion years until it is over two hundred times larger than today and a couple of thousand times more luminous.

Sun - Wikipedia

This then starts the red-giant-branch phase where the Sun will spend around a billion years and lose around a third of its mass. After the red-giant branch the Sun has approximately million years of active life left, but much happens. It will then have reached the red clump or horizontal branch , but a star of the Sun's mass does not evolve blueward along the horizontal branch. Instead, it just becomes moderately larger and more luminous over about million years as it continues to burn helium in the core.

When the helium is exhausted, the Sun will repeat the expansion it followed when the hydrogen in the core was exhausted, except that this time it all happens faster, and the Sun becomes larger and more luminous. This is the asymptotic-giant-branch phase, and the Sun is alternately burning hydrogen in a shell or helium in a deeper shell. After about 20 million years on the early asymptotic giant branch, the Sun becomes increasingly unstable, with rapid mass loss and thermal pulses that increase the size and luminosity for a few hundred years every , years or so.

The thermal pulses become larger each time, with the later pulses pushing the luminosity to as much as 5, times the current level and the radius to over 1 AU. Models vary depending on the rate and timing of mass loss. Models that have higher mass loss on the red-giant branch produce smaller, less luminous stars at the tip of the asymptotic giant branch, perhaps only 2, times the luminosity and less than times the radius. By the end of that phase—lasting approximately , years—the Sun will only have about half of its current mass.

The post-asymptotic-giant-branch evolution is even faster. The luminosity stays approximately constant as the temperature increases, with the ejected half of the Sun's mass becoming ionised into a planetary nebula as the exposed core reaches 30, K. The final naked core, a white dwarf , will have a temperature of over , K, and contain an estimated The Apex of the Sun's Way , or the solar apex , is the direction that the Sun travels relative to other nearby stars.

This motion is towards a point in the constellation Hercules , near the star Vega.

Formation & evolution

Of the 50 nearest stellar systems within 17 light-years from Earth the closest being the red dwarf Proxima Centauri at approximately 4. The Sun orbits the center of the Milky Way, and it is presently moving in the direction of the constellation of Cygnus. A simple model of the motion of a star in the galaxy gives the galactic coordinates X , Y , and Z as:.

We take X 0 and Y 0 to be zero and Z 0 is estimated to be 17 parsecs. In the X, Y coordinates, the sun describes an ellipse around the point, whose length in the Y direction is. The oscillation in the Z direction takes the sun. The Sun's orbit around the Milky Way is perturbed due to the non-uniform mass distribution in Milky Way, such as that in and between the galactic spiral arms. It has been argued that the Sun's passage through the higher density spiral arms often coincides with mass extinctions on Earth, perhaps due to increased impact events.

It is thought that the energy necessary to heat the corona is provided by turbulent motion in the convection zone below the photosphere, and two main mechanisms have been proposed to explain coronal heating. Currently, it is unclear whether waves are an efficient heating mechanism. Current research focus has therefore shifted towards flare heating mechanisms. Theoretical models of the Sun's development suggest that 3. Such a weak star would not have been able to sustain liquid water on Earth's surface, and thus life should not have been able to develop.

However, the geological record demonstrates that Earth has remained at a fairly constant temperature throughout its history, and that the young Earth was somewhat warmer than it is today. One theory among scientists is that the atmosphere of the young Earth contained much larger quantities of greenhouse gases such as carbon dioxide , methane than are present today, which trapped enough heat to compensate for the smaller amount of solar energy reaching it. However, examination of Archaean sediments appears inconsistent with the hypothesis of high greenhouse concentrations.

Instead, the moderate temperature range may be explained by a lower surface albedo brought about by less continental area and the "lack of biologically induced cloud condensation nuclei".