Astronomy

= Galaxy Formation =

Practice Quiz =Early Astronomers= The very earliest people, as early as six million years ago, knew much more about the moon and the planets and the stars than most people do today. That's because they lived mainly outside, without electric lights blocking out the sky, and they saw every night how the moon and the planets moved.

By about 3500 BC (and maybe long before that), people thought of these moving things in the sky as living beings - gods, with their own human-like personalities. If the moon and the planets were gods, they could affect the lives of people, and so the Mesopotamians and the Egyptians began to chart the movements of the planets and the moon to try to predict the future. They identified hundreds of constellations of stars, drew star maps, and created the idea of horoscopes and the signs of the Zodiac. These early astronomers all thought that the earth was the center of the universe, and that the moon, the sun, the planets and the stars all went around and around overhead in the sky. Around 600 BC, the Greek astronomer Thales rejected this idea that the moon and the stars were gods. Instead, Thales suggested that the earth was a round ball, and that the moon was lit by light reflecting from the sun. If the earth was round, then you could think of the moon and planets and stars and sun as going all the way around the earth. In 585 BC, Thales used this idea to become the first astronomer to successfully predict an eclipse of the sun. By about 430 BC, Anaxagoras had followed up on Thales' ideas to show exactly what caused eclipses.

Two hundred years later, about 250 BC, Eratosthenes calculated the circumference of the earth, and shortly after that Aristarchus figured out that the earth went around the sun, instead of the other way around, by considering the curved shadow of the earth on the moon during an eclipse of the moon. Aristarchus also figured out that the sun had to be a lot bigger than either the earth or the moon, and that the stars must be much, much farther away than the moon or the sun. Even though Aristarchus was right, though, most scientists thought he must be wrong - how could the stars really be that far away? It just seemed unlikely.

By 130 AD, Buddhist travelers from India had apparently brought news of these new Greek ideas to China, where Zhang Heng knew that the moon was a ball lighted by the sun, and understood eclipses. Sadly, meanwhile the Greeks had rejected this whole line of thought, and Roman astronomers like **Ptolemy** had gone back to thinking that the sun and stars went around the earth, rather than think that the stars were so far away. About 500 AD, the Indian astronomer Arya Bhata added the new idea that the earth spun around on its axis to make day and night. But Arya Bhata also went back to the earlier idea that the earth was at the center of the universe and the moon and the planets, the sun and the stars all moved around the sky. Even so, Arya Bhata did some important mathematical work on sines and cosines, and on time-pieces like water-clocks, that would help to measure the distances to the planets and stars.

A Chinese star chart from the 600s AD shows even some very faint stars that are hard to see with just your eyes. About 900 AD, the Islamic astronomer Al Razi built on Arya Bhata's work to show that the sun was bigger than the earth and the moon was smaller than the earth. Soon afterward, Islamic glass workers used medical research on the way the human eye worked to figure out how to to make glass lenses that would focus the heat of the sun in one spot. By 1100 AD, Al Ghazali was able to understand again what caused eclipses of the sun and the moon. About 1260 AD, another Islamic astronomer, Al Tusi, used an observatory to make very accurate measurements of the movements of the planets. Al Tusi also realized that the Milky Way was really not a cloud but a lot of very far away faint stars. In the 1470s, the Ottoman astronomer Ali Qushji revived the idea that the earth went around the sun.

By 1514, the Polish astronomer **Copernicus** published a small book proving that the earth actually went around the sun, as Aristarchus had thought more than a thousand years earlier. Still many people - most people - did not believe Copernicus, and his cause had to be defended in the later 1500s by Galileo, and again in the 1700s by **Isaac Newton**.

Ptolomy Copernicus Brache Kepler Galileo Newton

or The history of astronomy comprises three broadly defined areas that have characterized the science of the heavens since its beginnings. With varying degrees of emphasis among particular civilizations and during particular historical periods astronomers have sought to understand the motions of celestial bodies, to determine their physical characteristics, and to study the size and structure of the universe. The latter study is known as cosmology. **Motions of Sun, Moon, and Planets**

From the dawn of civilization until the time of Copernicus astronomy was dominated by the study of the motions of celestial bodies. Such work was essential for astrology, for the determination of the calendar, and for the prediction of eclipses, and it was also fueled by the desire to reduce irregularity to order and to predict positions of celestial bodies with ever-increasing accuracy. The connection between the calendar and the motions of the celestial bodies is especially important, because it meant that astronomy was essential to determining the times for the most basic functions of early societies, including the planting and harvesting of crops and the celebration of religious feasts.

The celestial phenomena observed by the ancients were the same as those of today. The Sun progressed steadily westward in the course of a day, and the stars and the five visible planets did the same at night. The Sun could be observed at sunset to have moved eastward about one degree a day against the background of the stars, until in the course of a year it had completely traversed the 360° path of constellations that came to be known as the zodiac. The planets generally also moved eastward along the zodiac, within 8° of the Sun's apparent annual path (the ecliptic), but at times they made puzzling reversals in the sky before resuming their normal eastward motion. By comparison, the Moon moved across the ecliptic in about 27 1/3 days and went through several phases. The earliest civilizations did not realize that these phenomena were in part a product of the motion of the Earth itself; they merely wanted to predict the apparent motions of the celestial bodies. Although the Egyptians must have been familiar with these general phenomena, their systematic study of celestial motions was limited to the connection of the flooding of the Nile with the first visible rising of the star Sirius. An early attempt to develop a calendar based on the Moon's phases was abandoned as too complex, and as a result astronomy played a lesser role in Egyptian civilization than it otherwise might have. Similarly, the Chinese did not systematically attempt to determine celestial motions. Surprising evidence of a more substantial interest in astronomy is found in the presence of ancient stone alignments and stone circles found throughout Europe and Great Britain, the most notable of which is Stonehenge in England. As early as 3000 B.C., the collection of massive stones at Stonehenge functioned as an ancient observatory, where priests followed the annual motion of the Sun each morning along the horizon in order to determine the beginning of the seasons. By about 2500 B.C., Stonehenge may have been used to predict eclipses of the Moon. Not until 1000 A.D. were similar activities undertaken by New World cultures. **Babylonian Tables.** Astronomy reached its first great heights among the Babylonians. In the period from about 1800 to 400 B.C., the Babylonians developed a calendar based on the motion of the Sun and the phases of the Moon. During the 400 years that followed, they focused their attention on the prediction of the precise time the new crescent Moon first became visible and defined the beginning of the month according to this event. Cuneiform tablets deciphered only within the last century demonstrate that the Babylonians solved the problem within an accuracy of a few minutes of time; this was achieved by compiling precise observational tables that revealed smaller variations in the velocity of the Sun and of the Moon than ever before measured. These variations - and others such as changes in the Moon's latitude - were analyzed numerically by noting how the variations fluctuated with time in a regular way. They used the same numerical method, utilizing the same variations, to predict lunar and solar eclipses. **Greek Spheres and Circles.** The Greeks used a geometrical rather than a numerical approach to understand the same celestial motions. Influenced by Plato's metaphysical concept of the perfection of circular motion, the Greeks sought to represent the motion of the divine celestial bodies by using spheres and circles. This explanatory method was not upset until Kepler replaced the circle with the ellipse in 1609. Plato's student Eudoxus of Cnidus, //c//.408-//c//.355 B.C., was the first to offer a solution along these lines. He assumed that each planet is attached to one of a group of connected concentric spheres centered on the Earth, and that each planet rotates on differently oriented axes to produce the observed motion. With this scheme of crystalline spheres he failed to account for the variation in brightness of the planets; the scheme was incorporated, however, into Aristotle's cosmology during the 4th century B.C.. Thus the Hellenic civilization that culminated with Aristotle attempted to describe a physical cosmology. In contrast, the Hellenistic civilization that followed the conquests of Alexander the Great developed over the next four centuries soon predominant mathematical mechanisms to explain celestial phenomena. The basis for this approach was a variety of circles known as eccentrics, deferents, and epicycles. The Hellenistic mathematician Apollonius of Perga, //c//.262-//c//.190 B.C., noted that the annual motion of the Sun can be approximated by a circle with the Earth slightly off-center, or eccentric, thus accounting for the observed variation in speed over a year. Similarly, the Moon traces an eccentric circle in a period of 27 1/3 days. The periodic reverse, or retrograde, motion of the planets across the sky required a new theoretical device. Each planet was assumed to move with uniform velocity around a small circle (the epicycle) that moved around a larger circle (the deferent), with a uniform velocity appropriate for each particular planet. Hipparchus, //c//.190-120 B.C., the most outstanding astronomer of ancient times, made refinements to the theory of the Sun and Moon based on observations from Nicaea and the island of Rhodes, and he gave solar theory essentially its final form. It was left for Ptolemy, //c//.100-//c//.165, to compile all the knowledge of Greek astronomy in the//Almagest// and to develop the final lunar and planetary theories. With Ptolemy the immense power and versatility of these combinations of circles as explanatory mechanisms reached new heights. In the case of the Moon, Ptolemy not only accounted for the chief irregularity, called the equation of the center, which allowed for the prediction of eclipses. He also discovered and corrected another irregularity, evection, at other points of the Moon's orbit by using an epicycle on a movable eccentric deferent, whose center revolved around the Earth. When Ptolemy made a further refinement known as prosneusis, he was able to predict the place of the Moon within 10 min, or 1/6°, of arc in the sky; these predictions were in good agreement with the accuracy of observations made with the instruments used at that time. Similarly, Ptolemy described the motion of each planet in the //Almagest//, which passed, with a few notable elaborations, through Islamic civilization and on to the Renaissance European civilization that nurtured Nicolaus Copernicus. The revolution associated with the name of Copernicus was not a revolution in the technical astronomy of explaining motions, but rather belongs to the realm of cosmology. Prodded especially by an intense dislike of one of Ptolemy's explanatory devices, known as the equant, which compromised the principle of uniform circular motions, Copernicus placed not the Earth but the Sun at the center of the universe; this view was put forth in his //De revolutionibus orbium caelestium// (On the Revolutions of the Heavenly Spheres, 1543). In that work, however, he merely adapted the Greek system of epicycles and eccentrics to the new arrangement. The result was an initial simplification and harmony as the diurnal and annual motions of the Earth assumed their true meaning, but no overall simplification in the numbers of epicycles needed to achieve the same accuracy of prediction as had Ptolemy. It was therefore not at all clear that this new cosmological system held the key to the true mathematical system that could accurately explain planetary motions. **Keplerian Ellipses and Newtonian Gravitation.** The German astronomer Johannes Kepler provided a daring solution to the problem of planetary motions and demonstrated the validity of the heliocentric theory of Copernicus, directly associating the Sun with the physical cause of planetary motions. At issue for Kepler was a mere 8 ft discrepancy between theory and observation for the position of the planet Mars. This degree of accuracy would have delighted Ptolemy or Copernicus, but it was unacceptable in light of the observations of the Danish astronomer Tycho Brahe, made from Uraniborg Observatory with a variety of newly constructed sextants and quadrants and accurate to within 1 ft to 4 ft. This new scale of accuracy revolutionized astronomy, for in his //Astronomia nova// (New Astronomy, 1609), Kepler announced that Mars and the other planets must move in elliptical orbits, readily predictable by the laws of planetary motion that he proceeded to expound in this work and in the //Harmonices mundi// (Harmonies of the World, 1619). Only by abandoning the circle could the heavens be reduced to an order comparable to the most accurate observations. Kepler's laws and the Copernican theory reached their ultimate verification with Sir Isaac Newton's enunciation of the laws of universal gravitation in the //Principia// (1687). In these laws, the Sun was assigned as the physical cause of planetary motion. The laws also served as the theoretical basis for deriving Kepler's laws. During the 18th century, the implications of gravitational astronomy were recognized and analyzed by able mathematicians, notably Jean d' Alembert, Alexis Clairaut, Leonhard Euler, Joseph Lagrange, and Pierre Laplace. The science of celestial mechanics was born and the goal of accurate prediction was finally realized. During all of this discussion the stars had been regarded as fixed. While working on his catalog of 850 stars, however, Hipparchus had already recognized the phenomenon known as the precession of the equinoxes, an apparent slight change in the positions of stars over a period of hundreds of years caused by a wobble in the Earth's motion. In the 18th century, Edmond Halley, determined that the stars had their own motion, known as proper motion, that was detectable even over a period of a few years. The observations of stellar positions, made with transit instruments through the monumental labors of such scientists as John Flamsteed, laid the groundwork for solving a cosmological problem of another era: the distribution of the stars and the structure of the universe.

(why do they study stars)

=Stars= When you look at the night sky you can see many beautiful stars. If you are out in the country or camping in the mountains or the desert away from the city lights, you may see thousands of them. You may even be able to see part of the Milky Way. In a town or city, you can't see nearly as many stars because the city lights create a glow in the sky masking many of them.

There are several different kinds of stars in the sky. Some are very big. A couple of stars have been found that are 100 to 200 times larger than the sun. Some very old stars are smaller than the Earth. Scientists study stars and place them in groups based on how they are alike and how they are different. he sun is an average sized star.

Constellations
A constellation is a group of visible stars that form a pattern when viewed from Earth. The pattern they form may take the shape of an animal, a mythological creature, a man, a woman, or an inanimate object such as a microscope, a compass, or a crown.

The sky was divided up into 88 different constellations in 1922. This included 48 ancient constellations listed by the Greek astronomer Ptolemy as well as 40 new constellations.

The 88 different constellations divide up the entire night sky as seen from all around the Earth. Star maps are made of the brightest stars and the patterns that they make which give rise to the names of the constellations.

The maps of the stars represent the position of the stars as we see them from Earth. The stars in each constellation may not be close to each other at all. Some of them are bright because they are close to Earth while others are bright because they are very large stars.

Not all of the constellations are visible from any one point on Earth. The star maps are typically divided into maps for the northern hemisphere and maps for the southern hemisphere. The season of the year can also affect what constellations are visible from where you are located on Earth.

Famous Constellations

Here are a few of the more famous constellations:


 * Orion

Orion is one of the most visible constellations. Because of its location, it can be seen throughout the world. Orion is named after a hunter from Greek mythology. Its brightest stars are Betelgeuse and Rigel. || Constellation Orion ||

Ursa Major

Ursa Major is visible in the northern hemisphere. It means "Larger Bear" in Latin. The Big Dipper is part of the Ursa Major constellation. The Big Dipper is often used as a way to find the direction north.

Ursa Minor

Ursa Minor means "Smaller Bear" in Latin. It is located near Ursa Major and also has the pattern of a small ladle called the Little Dipper as part of its larger pattern.




 * Draco

The Draco constellation can be viewed in the northern hemisphere. It means "dragon" in Latin and was one of the 48 ancient constellations.

Pegasus

The Pegasus constellation is named after the flying horse by the same name from Greek mythology. It can be seen in the northern sky. || Constellation Draco ||

The Zodiac

The zodiac constellations are the constellations that are located within a band that is about 20 degrees wide in the sky. This band is considered special because it is the band where the Sun, the Moon, and the planets all move.

There are 13 zodiac constellations. Twelve of these are also used as signs for the zodiac calendar and astrology. Uses for Constellations
 * Capricornus
 * Aquarius
 * Pisces
 * Aries
 * Taurus
 * Gemini
 * Cancer
 * Leo
 * Virgo
 * Libra
 * Scorpius
 * Sagittarius
 * Ophiuchus

Constellations are useful because they can help people to recognize stars in the sky. By looking for patterns, the stars and locations can be much easier to spot.

The constellations had uses in ancient times. They were used to help keep track of the calendar. This was very important so that people knew when to plant and harvest crops.

Another important use for constellations was navigation. By finding Ursa Minor it is fairly easy to spot the North Star (Polaris). Using the height of the North Star in the sky, navigators could figure out their latitude helping ships to travel across the oceans.

Interesting Facts about Constellations
 * The largest constellation by area is Hydra which is 3.16% of the sky.
 * The smallest is Crux which only takes up 0.17 percent of the sky.
 * Small patterns of stars within a constellation are called asterisms. These include the Big Dipper and Little Dipper.
 * The word "constellation" comes from a Latin term meaning "set with stars."
 * Twenty two different constellation names start with the letter "C."

= Star Life Cycle =
 * Vocabulary:** nebula, protostar, main sequence star, red giant, super giant, white dwarf, supernova, black dwarf neutron star, black hole

Stars are born, stars grow old, stars die. The life cycle of a star begins in a nebula and ends in a black hole. The lifespan of a star depends on its mass. The more massive it is, the shorter it lives. This 'long' and 'short' however, is in millions and billions of years!

The life cycle of a star is actually its 'struggle to live' fighting the gravitational pull and internal pressure. A majority of the life of a star is spent in the main sequence stage. Most stars, specifically our Sun, fuse hydrogen into helium and helium into heavier elements like carbon, oxygen up to even iron and nickel. Stars exhaust their energy during this process. Stars go through a series of changes during their lifespan. The process is known as stellar evolution, during which they change in their structure, composition, and appearance. Very massive stars live for a few million years, while those with lesser mass live for trillions of years.

It won't be wrong to say that a star is a sizzling mass of gas. It is composed of the inner core where the process of fusion takes place and an outer gaseous shell. The core is hot and dense, acting as the gravitational center of a star. The outer shell, made of hydrogen and helium, facilitates the transfer of heat from the core of the star to its surface. Light and heat energy is released into space from the surface of the star. Here's more on the stages in the life cycle of a star.

Stars are born in the nebulae. The matter contained in the nebula determines the mass of the star. Nebulae are clouds of gas and dust in space. The particles stay together due to their own gravitational forces. Nebulae may be formed due to gravitational collapse of gas in the ISM. Gravitational collapse refers to inward fall of a body under its own gravity. Some nebulae are formed from supernova. Here, the particles thrown during the explosion ionize and come together, forming a nebula. Clouds of dust and gas (majorly hydrogen) may be stirred by a passing star, which causes the particles to come closer together. This causes the matter in the nebula to concentrate towards one central point, which becomes the center of mass of the new star. Depending on the amount of matter, a dwarf or a new star is formed. The critical mass for the formation of a new star is around 80 times the mass of Jupiter. Nebulae are of different types. Emission nebulae emit light (electrons from hydrogen atoms combine with protons, giving out red light in the process). Reflection nebulae glow (dust particles in them reflect light from the stars). Many just remain suspended in space for years, while others are able to see a new star born!
 * Nebula**

Gravitational forces make the particles in a nebula spin. As they spin faster, the velocities cause particles to clump together forming a cloud-like structure. This is when a 'protostar' is born. If large clumpy structures break into small clouds, a cluster of protostars may be formed. The gravitational forces in the particles cause contraction and heating of the star. Physicist Viktor Ambartsumian, for the first time, proposed the existence of a protostar. A protostar is formed as a result of contraction out of the gas of giant molecular clouds in the ISM. A protostar starts accreting mass, which means addition of atoms to its center. Due to accretion, a protostar is unable to achieve equilibrium. The process ends with the formation of a T Tauri star. A protostar may take 100, 000 years to reach the main sequence stage in its life cycle Main Sequence Star
 * Protostar**

When gas pressure inside the star equals gravity, the star attains a stable state and begins entering the main sequence phase. It attains a temperature of about 15,000,000 °C. Nuclear fusion occurs and it begins to glow. The star contracts and becomes stable. It is now called the main sequence star or stable star. Stable stars exhibit the condition of equilibrium. Equilibrium is achieved when the force pushing out from the center equals the gravitational force that pulls the atoms inward. As the stars contract, the temperature, density and pressure at the core continue to rise. For a major part of its life span, a star stays in its main sequence phase. The conversion of hydrogen to helium takes place during this stage in the life cycle of a star.

The temperature at the core of the star slowly rises because the star emits energy. Hydrogen gets converted into helium by the process of nuclear fusion. When the hydrogen in the core depletes, the core loses stability. The temperature and pressure continue to rise. At this stage the temperature and pressure are so high that helium can fuse to carbon. This can be referred to as helium burning. The star then starts glowing red, thus entering the red giant phase. Very large red giant stars are known as Super Giants. They are magnanimous in size (have diameters about 1000 times that of the Sun) and have very high luminosities. The path taken by a star after this phase depends on its mass. It will become a neutron star, a white dwarf, black dwarf or a black hole.
 * Red Giant**

Stars with a smaller mass become white dwarfs. Their core shrinks to become a white dwarf while their outer layers are planetary nebulae. White dwarfs are small, dense and strangely faint. Astronomer Willem Jacob Luyten gave them this name. White dwarf stars are composed of electron degenerate matter. They are usually formed out of carbon and oxygen. If their temperature has fused carbon to neon, an oxygen-neon-magnesium white dwarf is formed. The electron degeneracy pressure causes white dwarfs to become dense. As they lack any source of energy, these initially hot stars, on radiating all their energy, cool down. White dwarfs have a mass comparable to that of the Sun and volume comparable to that of the Earth. After the depletion of all its energy, a white dwarf enters the 'dark dwarf' stage.
 * White Dwarf**

Supernova is an explosion of a star accompanied by emission of radiation and light. Sometimes, the light emitted by a supernova can outshine an entire galaxy! There are two basic types of supernovae. One is when a carbon-oxygen white dwarf reaches a critical density value, leading to uncontrolled fusion of carbon and oxygen, further leading to explosion. The second type of supernova is formed towards the end of a massive star's life cycle. When all the fuel in a star is exhausted, the iron core collapses with an explosion forming supernova.
 * Supernova**

A star in the red giant phase takes a different life cycle path. Fusion causes the helium atoms to form carbon atoms. They are further pulled together due to gravity, which results in the formation of oxygen, nitrogen and finally iron atoms. Iron starts absorbing energy that leads to an explosion. During this stage in the life cycle of a star, it is known as the neutron star. A neutron star is mainly composed of neutrons and is very hot and extremely dense (denser than the Sun!). Cores of massive stars collapse, converting proton-electron pairs into neutrons. A neutron star might spin speedily giving off light and X-rays. The highly magnetized spinning star appears to be pulsing, and is known by the name 'Pulsar'. These stars pulsate with surprising regularity.
 * Neutron Star**

Very massive stars become black holes. There is no nuclear fusion, the star core shrinks down to a point and the star gets swallowed by its own gravity, thus becoming a black hole. A black hole, as you might know, is a region through which nothing can pass. It swallows everything that comes its way and grows in size. Black holes are formed when heavy stars collapse in a supernova at the end of their lifespan.
 * Black Hole**

Black holes thus formed grow bigger by absorbing the surrounding mass, swallowing other stars and merging with other black holes. This leads to the creation of super massive black holes. This is where a star's life cycle comes to an end.

**The Sun** The Sun is by far the [|largest]  object in the solar system. It contains more than 99.8% of the total mass of the Solar System.

**Layers** The CORE of the Sun is where energy is first formed. Its temperature is 27 million degrees Fahrenheit. From the core, energy moves outward toward the Sun’s surface and surrounding atmosphere. The energy moves through several layers or zones. Remember the Sun’s layers are made of hot gases and they not solid like the Earth’s layers. The energy moves out from the core through the RADIATIVE ZONE. Scientists calculate the temperature to be cooler than the core—it is only a 4.5 million degrees Fahrenheit. That’s HOT!

The Sun’s next layer is the CONVECTION ZONE. Convection is how energy moves from the inner parts of the Sun to the outer part of the Sun that we see. We can see convection when we look at a pot of boiling water. Convection is what makes large, slow moving bubbles form in a bowl of hot miso soup. Through convection the heat moves from the bottom of the hot soup to the www.eyeonthesky.org soup’s surface where it is cooler. The Sun’s convection zone is a bubbling 2 millions degrees Fahrenheit.

The PHOTOSPHERE, the Sun’s visible surface, is the next layer of the Sun. The bubbling motion of the convection layer makes the granular patterns we see on the photosphere. The granules may look small in pictures, but scientists estimate they are really about the size of the Moon. Sunspots—indicating giant magnetic storms—are also visible on the photosphere. Most of the time sunspots come in pairs—like the poles of a magnet. Even though sunspots are very, very hot they look darker than the rest of the Sun because they’re cooler. This layer of the Sun has cooled off to 10,000 degrees Fahrenheit and the Sunspots are even cooler—about 7,800 degrees F.

Just above the photosphere is the CHROMOSPHERE with huge solar flares and loops of hot gases shooting up thousands of miles. Things begin to heat up again here—the temperature is estimated to be 50,000 degrees F.

And above the chromosphere is the CORONA—we can only see it during a total solar eclipse. The corona is very, very hot—4 million degrees F. It is also very thin. Scientists are still trying to figure out why it is hotter than other parts of the Sun. This is a big mystery… Sometimes when the Sun is very active, the hot gases shooting out of the Sun are so powerful that they blow away from the Sun into the solar system. They stream away in all direction from the Sun and can move up to 1 million miles per hour. These streaming, hot gases are called the SOLAR WIND. SOLAR FLARES are sudden, bright outbursts of energy that happen as the Sun’s magnetic fields twist, tear and reconnect. CORONAL LOOPS are magnetic loops with strong magnetic fields. Giant arches of gas that erupt on the Sun are called PROMINENCES. They can last several days.

CORONAL MASS EJECTIONS coming from the Sun have the most energy of all these solar events. Sometimes they head toward the Earth where they can cause communications disruptions and damage satellites. We are very lucky here on Earth because we have a powerful magnetic shield around us which protects us from getting too much energy. Earth is the perfect home planet for us! The Sun is a very dynamic and active star!