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Overview The brightest and largest object in our night sky, the Moon makes Earth a more livable planet by moderating our home planet’s wobble on its axis, leading to a relatively stable climate. It also causes tides, creating a rhythm that has guided humans for thousands of years. The Moon was likel…

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Sky Map Online web app provides free, printable & interactive sky charts for any location, time and viewpoint. It shows the night sky stars up to magnitude 12, planets and DSO.

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Learn more about Google Earth.

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Aw snap! Google Earth isn't supported on your browser. You may need to update your browser or use a different browser. Please see our system requirements for more information. Chrome is a great choice and you can download it here. Or if you're feeling adventurous, you can try Earth anyway by choosing an option below.

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The Moon l Phases, Orbit and distance from the Earth

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The Moon has been known since prehistoric times. It is the second brightest object in the sky after the Sun. Learn facts and figures.

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La luna es el único satélite natural de la Tierra y el único cuerpo del Sistema Solar que podemos ver en detalle a simple vista o con instrumentos sencillos.

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Portal Educativo - ¿Sabes que son las fases de la Luna? aprenderás a reconocerlas.

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Moon Phases 2018 - Lunar Calendar for Fort Worth, Texas, USA

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The Moon phase calculator shows exact times of the various moon phases for Fort Worth, Texas, USA in year 2018 or in other locations and years.

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Experience Earth, our solar system, nearby asteroids, the universe, and the spacecraft exploring them with immersive real-time 3D web-based apps for Mac, PC and mobile devices. No download or sign up necessary.

Experience Earth, our solar system, nearby asteroids, the universe, and the spacecraft exploring them with immersive real-time 3D web-based apps for Mac, PC and mobile devices. No download or sign up necessary.

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Welcome to NASA's Eyes, a way for you to learn about your home planet, our solar system, the universe beyond and the spacecraft exploring them.

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NASA.gov brings you the latest images, videos and news from America's space agency. Get the latest updates on NASA missions, watch NASA TV live, and learn about our quest to reveal the unknown and benefit all humankind.

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(Image credit: Getty Images)

It is the largest object in the solar system, but how big is the sun when compared to the rest of the stars in the Milky Way galaxy? The sun is classified as medium-sized among these hundreds of billions of stars.

Radius, diameter and circumference

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, according to NASA. The sun's circumference is about 2,715,396 miles (4,370,006 km).

It may be the biggest thing in this neighborhood, 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.

"We have found stars that are 100 times bigger in diameter than our sun. Truly those stars are enormous," NASA says on its SpacePlace website. "We have also seen stars that are just a tenth the size of our sun."

According to NASA's solar scientist C. Alex Young, if the sun were hollow, it would take about one million Earths to fill it.

It's possible that the sun is even larger than previously thought. Xavier Jubier, an engineer and solar eclipse researcher, creates detailed models of solar and lunar eclipses to determine precisely where the moon's shadow would fall during the solar eclipse. But when he matched actual photos and historical observations with the models, he found precise eclipse shapes only made sense if he scaled up the sun's radius by a few hundred kilometers.

Even missions like NASA's Solar Dynamics Observatory (SDO) and measurements of the inner planets across the face of the sun don't refine the star's radius as precisely as desired.

(Image credit: NASA/SDO)

"It's harder than you think just to put a ruler on these images and figure out how big the sun is - [SDO] doesn't have enough precision to nail this down," NASA researcher Ernie Wright told Space.com. "Similarly, with the Mercury and Venus transits, it turns out [a measurement based on those is] not quite as precise as you'd like it to be."

Wright said different papers using a variety of methods have produced results that differ by as much as 930 miles (1,500 km). That could be a problem if you are planning to skirt the edges of the next solar eclipse.

"For most people, yes, it doesn't really matter; it won't change everything," Jubier said. "But the closer you get to the edge of the [eclipse] path, the more risk you take."

Mass and volume

The total volume of the sun is 1.4 x 10 ²⁷cubic meters. About 1.3 million Earths could fit inside the sun, according to NASA's statistics. The mass of the sun is 1.989 x 10 30 kilograms, about 333,000 times the mass of the Earth. The sun contains 99.8 percent of the mass of the entire solar system, leading astronomers Imke de Pater and Jack J. Lissauer, authors of the textbook Planetary Sciences, to refer to the solar system as "the sun plus some debris".

But the sun's weight isn't constant. Over time, the solar wind has carried particles, and thus mass, away from the star. According to astronomer Phil Plait, the sun loses an average 1.5 million tons of material every second to the solar wind.

Meanwhile, in the heart of the star, mass is converted into energy. The powerhouse of the star converts more than 4 million tons of solar material into energy every second, Plait said.

Altogether, Plait estimated that the sun has lost a total of 10 ²⁴ tons of material over its 4.5-billion-year lifetime, or more than 100 times the mass of the Earth. While that sounds like a lot, it's only about 0.05 percent of the star's total mass.

Yellow dwarf

(Image credit: Getty Images)

The sun is classified as a G-type main-sequence star, or G dwarf star, or more imprecisely, a yellow dwarf. Actually, the sun - like other G-type stars - is white, but appears yellow through Earth's atmosphere.

Stars generally get bigger as they grow older. In about 5 billion years, scientists think the sun will start to use up all of the hydrogen at its center, according to NASA. The sun will puff up into a red giant and expand past the orbit of the inner planets, including Earth. The sun's helium will get hot enough to burn into carbon, and the carbon will combine with the helium to form oxygen. These elements will collect in the center of the sun.

Later, the sun will shed its outer layers, forming a planetary nebula and leaving behind a dead core of mostly carbon and oxygen - a very dense and hot white dwarf star, about the size of the Earth.

While the sun is typical in most respects, it does have one quality that stands out from the majority of stars - it is a loner. Most stars have a companion, with some part of a triple or even a quadruple system.

But it may not have always been a solo star. Research suggests that all stars may have started out with a companion. The sun's companion may have been a wide binary, putting it as much as 17 times farther from the sun than Neptune and making it easier to be stripped away.

"The idea that many stars form with a companion has been suggested before, but the question is: how many?" the study's first author Sarah Sadavoy, a NASA Hubble fellow at the Smithsonian Astrophysical Observatory, said. "Based on our simple model, we say that nearly all stars form with a companion."

Additional resources

For more facts about the sun, read NASA's overview: 10 Need-to-Know Things About the Sun. Additionally you can check out their Sun Fact Sheet for more statistics.

Bibliography

De Pater, Imke, and Jack J. Lissauer. Planetary sciences. Cambridge University Press (2015). https://books.google.co.uk

Embedded binaries and their dense cores. Monthly Notices of the Royal Astronomical Society, Volume 469, Issue 4 (2017). https://academic.oup.com/mnras/article/469/4/3881/3795556

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The sun is our solar system's most massive object, but what size is it?

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Check out our amazing space and astronomy facts for kids. Learn about different space objects and enjoy a range of cool trivia.

Sun Facts for Kids

Enjoy these fun Sun facts for kids. Learn how hot the Sun is, how long it takes light from the Sun to reach Earth, what the Sun is made of and more.

Read on for a range of interesting facts about the Sun.

The Sun is a star found at the center of the Solar System.

It makes up around 99.86% of the Solar System's mass.

At around 1,392,000 kilometres (865,000 miles) wide, the Sun's diameter is about 110 times wider than Earth's.

Around 74% of the Sun's mass is made up of hydrogen. Helium makes up around 24% while heavier elements such as oxygen, carbon, iron and neon make up the remaining percentage.

Light from the Sun reaches Earth in around 8 minutes.

The Sun's surface temperature is around 5500 degrees Celsius (9941 degrees Fahrenheit), so pack plenty of sunscreen if you plan on visiting (remembering that the average distance from the Sun to the Earth is around 150 million kilometers).

The Sun's core is around 13600000 degrees Celsius!

The Sun generates huge amounts of energy by combining hydrogen nuclei into helium. This process is called nuclear fusion.

Because of the Sun's huge influence on Earth, many early cultures saw the Sun as a deity or god. For example, Ancient Egyptians had a sun god called Ra while in Aztec mythology there is a sun god named Tonatiuh.

The Sun produces a solar wind which contains charged particles such as electrons and protons. They escape the Sun's intense gravity because of their high kinetic energy and the high temperature of the Sun's corona (a type of plasma atmosphere that extends into space).

Planets with strong magnetic fields such as Earth manage to deflect most of these charged particles as they approach.

A solar eclipse occurs when the Moon is between the Sun and the Earth.

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Fun Sun Facts for Kids - Interesting Facts about the Sun

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Check out our amazing space and astronomy facts for kids. Learn about different space objects and enjoy a range of cool trivia. Sun Facts for Kids Enjoy these fun Sun facts for kids. Learn how hot the Sun is, how long it takes light from the Sun to reach Earth, what the Sun is made of and more.

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DID YOU KNOW?

* It takes eight minutes and 20 seconds for the light leaving the sun to reach Earth. (Note: Never look directly at the sun!) The light from our next closest stellar neighbor, Proxima Centauri, takes more than four years to reach Earth!

* The sun actually creates weather in space-a stream of charged particles called "solar wind." Sometimes these particles erupt from sunspots (cooler regions of the sun's surface) as "solar flares" that can knock out power on Earth.

* Our sun rules the solar system on its own, but many stars share their systems with a second or third star. Imagine having two or three birthdays!

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Think Earth is the most important spot in the solar system? Think again. The sun is the real star of the show-literally!

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A flare is defined as a sudden,
rapid, and intense variation in brightness. A solar flare occurs when magnetic energy that has built up in the
solar
atmosphere is suddenly released.
Radiation is emitted
across virtually the entire electromagnetic
spectrum, from radio waves at
the long wavelength end,
through optical emission to x-rays and gamma rays at the short wavelength end. The amount of energy
released is the equivalent of millions of 100-megaton hydrogen bombs exploding at the same time! The first
solar flare recorded in astronomical literature was on September
1, 1859. Two scientists, Richard C. Carrington and Richard
Hodgson, were independently observing sunspots at the time, when they viewed a large flare in white light.

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Stars are giant fusion reactors, smashing protons together to produce energy.

Credit: by Karl Tate, Infographics Artist

Inside stars like the sun, the extreme temperature rips atoms into their components: protons, neutrons and electrons. Under normal conditions, the mutual repulsion of individual protons ought to force them apart. Quantum-tunneling effects in the sun allow hot, high-speed protons to fuse into helium nuclei. This fusion reaction drives the sun's radiance.

In the proton-proton fusion reaction, first two protons fuse. Usually the pair breaks apart again immediately, but once in a while one of the protons is transmuted into a neutron. The resulting proton-neutron pair is deuterium, a type of hydrogen. Also, a positron and a neutrino are emitted. When the positron encounters its antiparticle (an electron), the pair annihilates to form a gamma ray.

Then, another proton collides with the deuterium nucleus, forming a helium-3 nucleus (two protons and a neutron) plus a gamma ray. Gamma rays eventually work their way up from the core of the sun and out into space in the form of sunlight.

The helium-3 nucleus collides with another one, creating a helium-4 nucleus, plus two extra protons.

Solar Quiz: How Well Do You Know Our Sun?

The Sun in HD: Latest Photos by NASA's Solar Dynamics Observatory

Anatomy of Sun Storms & Solar Flares (Infographic)

Embed: Paste the code below into your site.

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Proton Fusion, the Sun's Power Source, Explained (Infographic)

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Inside stars like the sun, the extreme temperature rips atoms into their components: protons, neutrons and electrons. Under normal conditions, the mutual repulsion of individual protons ought to force them apart. Quantum-tunneling effects in the sun allow hot, high-speed protons to fuse into helium nuclei. This fusion reaction drives the sun's radiance.

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NASA's website for all news, images and videos related to Earth science. Your planet is changing. We're on it.

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Planetary Atmospheres

Earth is not the only world with an atmosphere. Each of the planets - and even a few moons - in our solar system have an atmosphere. Some planets have active atmospheres with clouds, wind, rain and powerful storms. Scientists use light spectroscopy to observe the atmospheres of planets and moons in other solar systems .

Each of the planets in our solar system has a uniquely structured atmosphere. The atmosphere of Mercury is extremely thin and is not very different from the vacuum of space. The gas giant planets in our solar system - Jupiter, Saturn, Uranus and Neptune - each have a thick, deep atmosphere. The smaller, rocky planets - Earth, Venus and Mars - each have thinner atmospheres, hovering above their solid surfaces. The moons in our solar system typically have thin atmospheres, with the exception of Saturn's moon, Titan. Air pressure at the surface of Titan is higher than on Earth! Of the five officially recognized dwarf planets, Pluto has a thin atmosphere that expands and collapses seasonally, and Ceres has an extremely thin and transient atmosphere made of water vapor.

But only Earth's atmosphere has the layered structure that traps enough of the Sun's energy for warmth while also blocking much of the harmful radiation from the Sun. This important balance is necessary to maintain life on Earth.

© 2021 UCAR

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The atmosphere is a mixture of gases that surrounds the planet. Without the atmosphere, life on Earth wouldn't be possible.

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Blanketing the Earth is a thick layer of air that protects us from radiation from the Sun, falling meteors and toxic gases. This blanket, known as the atmosphere, has three layers. Without it, our Earth would be like any other planet - extremely hot or cold, pockmarked and lifeless. Three cheers for the atmosphere!

Fun Facts About the Atmosphere for Kids

There are five layers within the atmosphere. The troposphere, the stratosphere, mesosphere, ionosphere and exosphere are the layers of the atmosphere.

The troposphere lies closest to the Earth and is about 11 miles thick. This layer contains most of the air and oxygen in the atmosphere. Our weather is formed in the troposphere. Water evaporates from land to become rain or snow. Winds bring warm or cool weather.

The stratosphere lies above the troposphere and goes up about 30 miles high. The ozone layer is in the stratosphere. The ozone protects us from harmful rays from the Sun.

The mesosphere is the next layer, reaching 50 miles from the Earth. This layer of the atmosphere is very cold - about -180 degrees Fahrenheit. Brrrr! Here is where most meteors burn up. Without this layer, our Earth would be pocked like the Moon and other planets.

The ionosphere extends 430 miles above the Earth and is considered outer space. It is very thin and very cold. An electrical layer created by ions is found here which is used to transmit radio waves. This electrical layer also causes the Northern Lights.

High above the Earth is the exosphere, the final layer of our atmosphere. This layer extends into space. Solar winds compress it and push it down. When the winds are still, this layer can extend more than 6,000 miles into space.

The Atmosphere Vocabulary

All About the Atmosphere Video for Kids

Check out this cool video about the Earth's Atmosphere for kids:

The Atmosphere Q&A

Question: Can the atmosphere be damaged?

Answer: Chemicals and pollution can damage the atmosphere.

Enjoyed the Easy Earth Science for Kids all about the Atmosphere info? Take the FREE & Fun all about the Atmosphere quiz and download FREE all about the Atmosphere worksheet for kids. For lengthy info click here.

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Blanketing the Earth is a thick layer of air that protects us from radiation from the Sun, falling meteors and toxic gases. This blanket, known as the atmosphere, has three layers. Without it, our Earth would be like any other planet - extremely hot or cold, pockmarked and lifeless.

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Diagram of the layers within Earth's atmosphere. Troposphere
The troposphere starts at the Earth's surface and extends 8 to 14.5 kilometers high (5 to 9 miles). This part of the atmosphere is the most dense. Almost all weather is in this region. Stratosphere
The stratosphere starts just above the troposphere and extends to 50 kilometers (31 miles) high. The ozone layer, which absorbs and scatters the solar ultraviolet radiation, is in this layer. Mesosphere
The mesosphere starts just above the stratosphere and extends to 85 kilometers (53 miles) high. Meteors burn up in this layer Thermosphere
The thermosphere starts just above the mesosphere and extends to 600 kilometers (372 miles) high. Aurora and satellites occur in this layer. Ionosphere
The ionosphere is an abundant layer of electrons and ionized atoms and molecules that stretches from about 48 kilometers (30 miles) above the surface to the edge of space at about 965 km (600 mi), overlapping into the mesosphere and thermosphere. This dynamic region grows and shrinks based on solar conditions and divides further into the sub-regions: D, E and F; based on what wavelength of solar radiation is absorbed. The ionosphere is a critical link in the chain of Sun-Earth interactions. This region is what makes radio communications possible. Exosphere
This is the upper limit of our atmosphere. It extends from the top of the thermosphere up to 10,000 km (6,200 mi). Credit: NASA/Goddard

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Diagram of the layers within Earth's atmosphere.

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Does the moon have an atmosphere? it's complicated?

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Does the moon have an atmosphere? it's complicated?

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Is There an Atmosphere on the Moon?

The Lunar Atmospheric Composition Experiment (LACE) deployment during the Apollo 17 mission. Image credit: NASA
[image-51]

Until recently, most everyone accepted the conventional wisdom that the moon has virtually no atmosphere. Just as the discovery of water on the moon transformed our textbook knowledge of Earth's nearest celestial neighbor, recent studies confirm that our moon does indeed have an atmosphere consisting of some unusual gases, including sodium and potassium, which are not found in the atmospheres of Earth, Mars or Venus. It's an infinitesimal amount of air when compared to Earth's atmosphere. At sea level on Earth, we breathe in an atmosphere where each cubic centimeter contains 10,000,000,000,000,000,000 molecules; by comparison the lunar atmosphere has less than 1,000,000 molecules in the same volume. That still sounds like a lot, but it is what we consider to be a very good vacuum on Earth. In fact, the density of the atmosphere at the moon's surface is comparable to the density of the outermost fringes of Earth's atmosphere where the International Space Station orbits.

What is the moon's atmosphere made of? We have some clues. The Apollo 17 mission deployed an instrument called the Lunar Atmospheric Composition Experiment (LACE) on the moon's surface. It detected small amounts of a number of atoms and molecules including helium, argon, and possibly neon, ammonia, methane and carbon dioxide. From here on Earth, researchers using special telescopes that block light from the moon's surface have been able to make images of the glow from sodium and potassium atoms in the moon's atmosphere as they are energized by the sun. Still, we only have a partial list of what makes up the lunar atmosphere. Many other species are expected.

We think that there are several sources for gases in the moon's atmosphere. These include high energy photons and solar wind particles knocking atoms from the lunar surface, chemical reactions between the solar wind and lunar surface material, evaporation of surface material, material released from the impacts of comets and meteoroids, and out-gassing from the moon's interior. But which of these sources and processes are important on the moon? We still don't know.

With the discovery of significant ice deposits at the moon's poles by NASA's Lunar CRater Observation and Sensing Satellite (LCROSS) and Lunar Reconnaissance Orbiter (LRO) missions, and the discovery of a thin scattering of water molecules in the lunar soil by the Chandrayaan X-ray Observatory, another fascinating possibility has captured researchers' interest. The moon's atmosphere may play a key role in a potential lunar water cycle, facilitating the transport of water molecules between polar and lower latitude areas. The moon may not only be wetter than we once thought, but also more dynamic.

One of the critical differences between the atmospheres of Earth and the moon is how atmospheric molecules move. Here in the dense atmosphere at the surface of Earth, the molecules' motion is dominated by collisions between the molecules. However the moon's atmosphere is so thin, atoms and molecules almost never collide. Instead, they are free to follow arcing paths determined by the energy they received from the processes described above and by the gravitational pull of the moon.

The technical name for this type of thin, collision-free atmosphere that extends all the way down to the ground is a "surface boundary exosphere." Scientists believe this may be the most common type of atmosphere in the solar system. In addition to the moon, Mercury, the larger asteroids, a number of the moons of the giant planets and even some of the distant Kuiper belt objects out beyond the orbit of Neptune, all may have surface boundary exospheres. But in spite of how common this type of atmosphere is, we know very little about it. Having one right next door on our moon provides us with an outstanding opportunity to improve our understanding.

Among the goals of the Lunar Atmosphere and Dust Environment Explorer (LADEE) are to determine the composition and structure of the tenuous lunar atmosphere and to understand how these change with time, and as external conditions vary. LADEE's measurements come at a key time: with increasing interest in the moon by a number of nations, future missions could significantly affect the natural composition of the lunar atmosphere.

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Is There an Atmosphere on the Moon? The Lunar Atmospheric Composition Experiment (LACE) deployment during the Apollo 17 mission. Image credit: NASA [image-51] Until recently, most everyone accepted the conventional wisdom that the moon has virtually no atmosphere.

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www.solarastronomy.org where the Sun always shines!

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PAYPAL OR ANY OTHER EMAIL BASED DONATION CAN BE SENT

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El Sol se formó hace 4.650 millones de años y tiene combustible para 5.000 millones más. Después, comenzará a hacerse más y más grande, hasta convertirse en una gigante roja. Finalmente, se hundirá por su propio peso y se convertirá en una enana blanca, que puede tardar un trillón de años en enfriarse.

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Introducción

El Sol es la estrella que, por el efecto gravitacional de su masa, domina el sistema planetario que incluye a la Tierra. Es el elemento más importante en nuestro sistema solar y el objeto más grande que contiene aproximadamente el 98% de la masa total del sistema solar. Mediante la radiación de su energía electromagnética, aporta directa o indirectamente toda la energía que mantiene la vida en la Tierra, porque todo el alimento y el combustible procede en última instancia de las plantas que utilizan la energía del sol en su proceso de fotosíntesis.

Tipo espectral: Nuestro sol es una estrella del tipo espectral G2V, denominada también enana amarilla.

A causa de su proximidad a la Tierra y como es una estrella típica, el Sol es un recurso extraordinario para el estudio de los fenómenos estelares. No se ha estudiado ninguna otra estrella con tanto detalle. La estrella más cercana al Sol está a 4,3 años luz; para observar los rasgos de su superficie comparables a los que se pueden ver de forma habitual en el Sol, se necesitaría un telescopio de casi 30 km de diámetro. Además, un telescopio así tendría que ser colocado en el espacio para evitar distorsiones causadas por la atmósfera de la Tierra.

Historia de la observación científica

Durante la mayor parte del tiempo que los seres humanos han estado sobre la Tierra, el Sol ha sido considerado un objeto de especial importancia. Muchas culturas antiguas adoraron al Sol y muchas más reconocieron su importancia en el ciclo de la vida. Aparte de su relevancia posicional para señalar, por ejemplo, solsticios, equinoccios y eclipses, el estudio cuantitativo del Sol data del descubrimiento de las manchas solares; el estudio de sus propiedades físicas no comenzó hasta mucho más tarde. Los astrónomos chinos observaron manchas solares a simple vista ya en el año 200 a.C. Pero en 1611, Galileo utilizó el telescopio, recién inventado, para observarlas de modo sistemático. El descubrimiento de Galileo significó el comienzo de una nueva aproximación al estudio del Sol, que pasó a ser considerado un cuerpo dinámico, en evolución, y sus propiedades y variaciones pudieron ser, por tanto, comprendidas científicamente.

El siguiente avance importante en el estudio del Sol se produjo en 1814 como resultado directo del invento del espectroscopio por el físico alemán Joseph von Fraunhofer. Un espectroscopio divide la luz en las longitudes de onda que la componen, o colores. Aunque el espectro del Sol había sido observado ya en 1666 por el matemático y científico inglés Isaac Newton, la precisión del trabajo de Fraunhofer sentó las bases para los primeros intentos de una explicación teórica detallada de la atmósfera solar.

Parte de la radiación de la superficie visible del Sol (la fotosfera) es absorbida por el gas, algo más frío, que hay sobre ella. Sin embargo, sólo se absorben longitudes de onda de radiación particulares, que dependen de las especies atómicas presentes en la atmósfera solar. En 1859, el físico alemán Gustav Kirchhoff demostró que la falta de radiación en ciertas longitudes de onda del espectro solar de Fraunhofer se debía a la absorción de radiación por átomos de algunos de los mismos elementos presentes en la Tierra. Con esto, no sólo demostró que el Sol está compuesto de materia común, sino que también planteó la posibilidad de obtener información detallada sobre los objetos celestes mediante el estudio de la luz emitida por ellos. Éste fue el comienzo de la astrofísica.

El progreso en el conocimiento del Sol ha continuado gracias a la habilidad de los científicos para hacer observaciones nuevas o mejorar las anteriores. Entre los avances en instrumentos de observación que han influido de forma significativa en la física solar están el espectroheliógrafo, que mide el espectro de los rasgos solares individuales; el coronógrafo instrumento que permite el estudio de la corona solar sin eclipses ya que tapa al sol de manera precisa y el magnetógrafo, inventado por el astrónomo estadounidense Horace W. Babcock en 1948, que mide la fuerza del campo magnético de la superficie solar. El desarrollo de cohetes y satélites ha permitido a los científicos observar la radiación en longitudes de onda no transmitidas a través de la atmósfera de la Tierra. Entre los instrumentos desarrollados para su uso en el espacio se encuentran los coronógrafos, los telescopios y los espectrógrafos sensibles a una radiación ultravioleta extrema y a los rayos X. Los instrumentos especiales han revolucionado el estudio de la atmósfera exterior al Sol.

Características del sol: Composición y estructura

La energía solar se crea en la parte más interior del Sol denominado NUCLEO. Es aquí donde la temperatura (15.000.000° C) y la presión (340 mil veces la presión del aire en la Tierra al nivel del mar) son tan intensas que se llevan a cabo las reacciones nucleares. Éstas reacciones causan que cuatro átomos de hidrógeno se fusionen y formen una partícula alfa o núcleo de helio. La partícula alfa tiene cerca de 0.7 % menos masa que los cuatro protones. La diferencia en la masa es expulsada como energía y es llevada a la superficie del Sol, a través de un proceso conocido como convección, donde se liberan luz y calor. La energía generada en el centro del Sol tarda un millón de años para alcanzar la superficie solar. Cada segundo se convierten 700 millones de toneladas de hidrógeno en cenizas de helio, el núcleo solar esta compuesto de hidrógeno y helio en cantidades iguales y un 2% de otros elementos. En el proceso se liberan 5 millones de toneladas de energía pura; por lo cual, el Sol cada vez se vuelve más ligero.

La energía producida de esta forma es transportada a la mayor parte de la superficie solar por la denominada zona de radiación. mediante un proceso llamado difusión radiativa. Sin embargo, más cerca de la superficie, en la zona de convección que ocupa el último tercio del radio solar, la energía es transportada por la mezcla turbulenta de gases donde los más calientes empujan para ascender.

La fotosfera es la superficie superior de la zona de convección. Se pueden ver pruebas de la turbulencia en la zona de convección observando la fotosfera y la atmósfera situada encima de ella.

Las células turbulentas de la fotosfera le confieren una apariencia irregular y heterogénea. Este modelo, conocido como granulación solar, lo provoca la turbulencia en los niveles más altos de la zona de convección. Cada gránulo mide unos 2.000 km de ancho. Aunque el modelo de granulación siempre está presente, los gránulos individuales solamente duran unos 10 minutos. También se presenta un modelo de convección mucho mayor, provocado por la turbulencia que se extiende en las profundidades de la zona de convección. Este modelo de sobregranulación contiene células que duran un día y tienen 30.000 km de ancho como media.

Cromosfera:
Significa "Espera de color" y es el aro de color rojizo que se puede observar en un eclipse total de sol cuando La Luna se interpone entre El Sol y La Tierra. La cromosfera se encuentra ubicada entre la fotosfera y la corona solar. Tiene un espesor entre 3000 y 5000 kilómetros. Tiene miles de picos verticales, llamados espículas, estos picos verticales apenas duran unos minutos, son chorros de gas expulsados de la cromosfera a una veintena de kilómetros por segundo y que penetran la región exterior del sol a varios millares de kilómetros. Ver información más detallada en nuestro diccionario de astronomía: www.todoelsistemasolar.com.ar/cromosfera.php

(Click en la imagen para agrandarla)

Manchas solares

George Ellery Hale descubrió en 1908 que las manchas solares (áreas más frías de la fotosfera) presentan campos magnéticos fuertes. Estas manchas solares se suelen dar en parejas, con las dos manchas con campos magnéticos que señalan sentidos opuestos. El ciclo de las manchas solares, en el que la cantidad de manchas solares varía de menos a más y vuelve a disminuir al cabo de unos 11 años, se conoce por lo menos desde principios del siglo XVIII. Sin embargo, el complejo modelo magnético asociado con el ciclo solar sólo se comprobó tras el descubrimiento del campo magnético del Sol.

Como cada mancha solar dura como mucho unos pocos meses, el ciclo solar de 22 años refleja los procesos asentados y de larga duración en el Sol y no las propiedades de las manchas solares individuales. Aunque no se comprenden del todo, los fenómenos del ciclo solar parecen ser el resultado de las interacciones del campo magnético del Sol con la zona de convección en las capas exteriores. Además, estas interacciones se ven afectadas por la rotación del Sol, que no es la misma en todas las latitudes. El Sol gira una vez cada 27 días cerca del ecuador, pero una vez cada 31 días más cerca de los polos.

La corona:
La atmósfera solar exterior que se extiende varios radios solares desde el disco del Sol es la corona. Todos los detalles estructurales de la corona se deben al campo magnético. La mayor parte de la corona se compone de grandes arcos de gas caliente: arcos más pequeños dentro de las regiones activas y arcos mayores entre ellas. Las formas arqueadas y a veces rizadas se deben al campo magnético.
En los años cuarenta se descubrió que la corona es mucho más cálida que la fotosfera. La fotosfera del Sol, o superficie visible, tiene una temperatura de casi 6.000º C. La cromosfera, que se extiende varios miles de kilómetros por encima de la fotosfera, tiene una temperatura cercana a los 30.000º C. Pero la corona, que se extiende desde justo encima de la cromosfera hasta el límite con el espacio interplanetario, tiene una temperatura de 1.000.000º C. Para mantener esta temperatura, la corona necesita un suministro de energía.

La búsqueda del mecanismo por el cual la energía llega a la corona es uno de los problemas clásicos de la astrofísica. Todavía está sin resolver, aunque se han propuesto muchas explicaciones. Las recientes observaciones del espacio han mostrado que la corona es una colección de rizos magnéticos, y cómo se calientan estos rizos se ha convertido en el foco principal de la investigación astrofísica.

El campo magnético también puede retener material más frío encima de la superficie del Sol, aunque este material sólo permanece estable unos pocos días. Estos fenómenos se pueden observar durante un eclipse como pequeñas regiones, conocidas como protuberancias, en el mismo extremo del Sol, como joyas de una corona. Están en calma, pero ocasionalmente entran en erupción, arrojando material solar al espacio.

Viento solar:

En uno o dos radios solares desde la superficie del Sol, el campo magnético de la corona tiene la fuerza suficiente para retener el material gaseoso y caliente de la corona en grandes circuitos. Cuanto más lejos está del Sol, el campo magnético es más débil y el gas de la corona puede arrojar literalmente el campo magnético al espacio exterior. Cuando sucede esto, la materia recorre grandes distancias a lo largo del campo magnético.

El flujo constante del material arrojado desde la corona es conocido como viento solar y suele llegar de las regiones denominadas agujeros de la corona. Allí, el gas es más frío y menos denso que en el resto de la corona, produciendo una menor radiación. El viento solar de los grandes agujeros de la corona (que puede durar varios meses) es muy fuerte. Debido a la rotación solar, estas regiones de fuerte viento solar, conocidas como corrientes de viento solar a gran velocidad, suelen repetirse cada 27 días vistas desde la Tierra. El viento solar provoca alteraciones que se pueden detectar desde el campo magnético de la Tierra.

Evolución solar:

El pasado y el futuro del Sol se han deducido de los modelos teóricos de estructura estelar. Durante sus primeros 50 millones de años, el Sol se contrajo hasta llegar a su tamaño actual. La energía liberada por el gas calentaba el interior y, cuando el centro estuvo suficientemente caliente, la contracción cesó y la combustión nuclear del hidrógeno en helio comenzó en el centro. El Sol ha estado en esta etapa de su vida durante unos 4.500 millones de años.

En el núcleo del Sol hay hidrógeno suficiente para durar otros 4.500 millones de años. Cuando se gaste este combustible, el Sol cambiará: según se vayan expandiendo las capas exteriores hasta el tamaño actual de la órbita de la Tierra, el Sol se convertirá en una gigante roja, algo más fría que hoy pero 10.000 veces más brillante a causa de su enorme tamaño. Sin embargo, la Tierra no se consumirá porque se moverá en espiral hacia afuera, como consecuencia de la pérdida de masa del Sol. El Sol seguirá siendo una gigante roja, con reacciones nucleares de combustión de helio en el centro, durante sólo 500 millones de años. No tiene suficiente masa para atravesar sucesivos ciclos de combustión nuclear o un cataclismo en forma de explosión, como les ocurre a algunas estrellas. Después de la etapa de gigante roja, se encogerá hasta ser una enana blanca, aproximadamente del tamaño de la Tierra, y se enfriará poco a poco durante varios millones de años. Este proceso puede tomarle un trillón de años, se supone que el fin de sus días será como una "enana negra" que es un tipo de estrella que se supone aún no existe en el Universo porque es muy joven, aún si existiera una enana negra en el universo actual sería muy difícil de detectar ya que no emite luz.

ROTACION: ¿Gira el Sol?

El sol está compuesto de gas, por lo cual su rotación no es pareja. El sol gira una vez cada 27 días en el ecuador y una vez cada 31 días terrestres en sus polos, gracias a las manchas solares se pudo calcular la diferencia de velocidad entre el ecuador y sus polos. No ha sido ninguna sorpresa para los astrónomos ya que los planetas gaseosos Júpiter, Saturno, Urano y Neptuno, también tienen esta diferencia de velocidad entre el polo y el ecuador.

Misiones espaciales:

El 12 de agosto de 2018 se ha lanzado la misión "Parker Solar Probe", de la NASA dicha misión durará casi 7 años. La siguiente misión al Sol está programada para febrero del año 2019, la misma está denominada "solar orbiter" y está diseñada por la Agencia Espacial Europea.

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El Sol es la estrella que, por el efecto gravitacional de su masa, domina el sistema planetario que incluye a la Tierra. Es el elemento más importante en nuestro sistema solar y el objeto más grande que contiene aproximadamente el 98% de la masa total del sistema solar.

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ye a wae

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master roshi : goku the sun is a dorf star

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master roshi : goku the sun is a dorf star

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Did you know that Pluto didn’t even finished his orbit when he was considered a planet? Lik if u cri evertim

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what the sun is a star!!!!