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Astronomy: The Solar System

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posted on Oct, 26 2004 @ 07:52 PM
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Sorry for the major delay, Iíve been amidst a move and adjusting to a very odd schedule and havenít had much time to work on ATS. I was planning on doing a series of Constellations, but since itís been so long and Iím sure some of you have been looking forward to the next installment, so this is it!


Also, as usual, bear with my poor graphic skills.

The Basics
Here are some graphics so you can see the scale of the Solar System. You can also see the distance of the planets from the Sun, given in AUs. One AU is equal to the mean distance from Earth to the Sun: 93 million miles or 150 million kilometers.

The Inner Solar System*


The Outer Solar System*


Some odd things can be noticed if you observe a planet steadily for a period of weeks or months. The oddest being the phenomena of retrograde motion. The planets move relative to the stars from the west to the east. But since Earth moves faster that the superior planets (planets further from the Sun than Earth) it will eventually overtake them in its orbit. When this happens the planet being observed seems to make a backward loop in the sky. This effect can be seen most obviously in Mars, since it is the nearest superior planet.

Viewing planets depends a lot on their location in relation to the Sun and Earth. The angle of an inferior planet, as seen from Earth, is known as elongation. While at their Greatest Eastern and Western Elongations, the inferior planets will lie in the evening and morning skies, respectively. When the elongation is zero, the planet is known to be at conjunction. When an inferior planet is opposite the Sun, it is at its Superior Conjunction, while when it is between the Sun and Earth, it is at its Inferior Conjunction.

Inferior Orbit

1.) Earth; 2.) Sun; 3.) Superior Conjunction; 4.) Greatest Eastern Elongation; 5.) Inferior Conjunction; 6.) Greatest Western Elongation; 7.) Angle of Elongation

Outer planets also have Conjunctions, but only when they are opposite the Sun. When the Earth is between the Sun and superior planet, that planet is deemed to be in its Opposition. At this time the planet looks largest and is visible all night. Also, the planet would lie due south from northern latitudes and due north from southern latitudes.

Superior Orbit

1.) Sun; 2.) Earth; 3.) Planet at Opposition; 4.) Planet at Conjunction

The Sun (More than just there for a good tan!)
The Sun, the closest star to Earth, the source of light and heat for all the Solar System, and a mere 93 million miles (150 million kilometers) away. The Sun dwarfs all other bodies in our Solar System, and as a testament to that makes up 98% of all the mass.

Diameter: Though classified as a dwarf star, the Sunís diameter is 864,000 miles (1.5 million Kilometers). Thatís nearly 110 times the diameter of the Earth.
Mass: 2 X 10^30 Kg (333,000 times that of Earth)
Class: G2 V Main Sequence Dwarf
Surface Temperature: 5800 K (10,400 F)
Core Temperature: 15 million K (29 million F)
Luminosity: 3.9 X 10^26 J/s (watts)
Age: 4.6 billion years (out of a 10-12 year existence)
Composition: 74% Hydrogen, 25% Helium, 1% everything else
Energy Source: Nuclear Fusion (H fused to He)

The Sun, as well as every other star, stays in a sphere due to Hydrostatic Equilibrium. That is basically a balance between the outward pressure of the nuclear ďfireĒ and gravity.

Structure
**

As you can see, the Sun is made up of many different parts and layers. Starting from the inside out you have the Core, the Radiative Zone, the Convective Zone, the Photosphere, the Chromosphere, and the Corona.

The Core is where the thermonuclear reactions that power the Sun take place. In this area temperatures soar to 15 million degrees Kelvin. Also, this area only makes up about 1/20 of the Sunís diameter. Energy from these reactions travels out of the Sun first as radiation (in the Radiative Zone) and then through convection (in the Convective Zone). Over time, this energy reaches the photosphere. The photosphere is the source of visible light. Also, it is where sunspots are located. Sunspots are ďcoolĒ areas in the photosphere associated with huge magnetic field disturbances. Following the photosphere is the chromosphere, which is a color absorption/emission layer. In this highly turbulent gas layer, some frequencies of light are absorbed, while others are given off. Finally we reach the corona, which is the thin, but intensely hot, outer portion of the sun. In the corona there are holes, which allow streams of solar wind to come forth. Sometimes there is whatís known as a coronal mass ejection, in which particles are ejected from the Sun in a violent explosion. When the particles from these explosions reach Earth the create the auroras.

Sunspots
A sunspot is made up of two parts, the Umbra (darker, cooler central region) and the Penumbra (lighter, cool outer region.) Sunspots can last from only a few days to several months, and range in size from a few hundred miles across to complex groups extended over 60,000 miles (100,000 km) on the Sunís surface.


Umbra is the center potion; Penumbra is the outer portion.

Sunspots rise and fall in a cycle that lasts about 11 years. At the start of this cycle there are few spots, and appear mainly away from the equator. As the cycle gets around itís peak sunspots appear closer and closer to the equator of the Sun and even up to 100 or more can be visible at one time.


1.) First sunspots of new cycle; 2.) Last sunspots of old cycle; 3.) Sunspots appear nearer to the equator; 4.) Number of spots falls off; 5.) Last spots of old cycle; 6.) First spots of new cycle.

Prominences
Occasionally eruptions occur near sunspots, called prominences or flares. Particles are ejected from the Sunís surface and escape through coronal holes.

Eclipses of the Sun
Every so often the Moon passes between the Earth and Sun, blocking its lights to cause a solar eclipse. At least two solar eclipses occur each year, but not everyone can see them. Anyone within the dark, inner part of the shadow (the umbra) will see a total eclipse. Under the lighter, outer shadow (the penumbra) a partial eclipse will be seen. When the Sunís disc is entirely covered the corona becomes visible. A total eclipse can last just under 10 minutes, though between 2 and 3 minutes is much more usual. A partial eclipse can last up to four hours in some cases.



When the Moon is farthest away from the Earth, it is unable to completely cover up the disc of the Sun. This is called an annular eclipse, because a ring, or annulus, of light remains visible at mid eclipse.



Mercury
The closest planet to the Sun, Mercury leads a scorched, frozen, and battered existence. It is always close to the Sun, in fact never more than 28 degrees away, making it very hard to observe. It also bears a striking resemblance to our Moon, being covered with craters, being just slightly larger, and having neither air nor water.

Diameter: 3025 miles (4868 kilometers)
Sun Distance: 36 million miles (58 million kilometers)
Rotation: 59 Earth Days
Revolution: 88 Earth Days
Mass: .06 Earth
Gravity: .38 Earth
Average Temp.: 333 F (167 C)
Maximum Magnitude: -1.5

Observation
Though it is possible to locate Mercury with the naked eye, more often than not binoculars would be needed. The best time to locate Mercury would be around its greatest elongation, since it would be farthest from the Sun. While viewing during this time, a magnification of 250X would show Mercury to be as large as the Moon appears to the naked eye. Mercury also undergoes phases, which can be seen through a small telescope or binoculars.

Atmosphere and Climate
Mercury is an airless, waterless wasteland. Due to this and its proximity to the Sun, its surface is blasted with solar radiation which can raise the daytime temperature to over 840 F (450 C.) At night the surface temperatures to below Ė290 F (-180 C.)

Geography and Geology
Mercury has been battered over the ages by a myriad of objects. The gravity of the Sun pulls objects such as asteroids and comets into it, which on occasion have collided with Mercury. Though highly similar to the surface of Earthís Moon, one distinct feature is that Mercury has 2 mile high cliffs that run for several hundred miles. These were most likely caused by the shrinking and wrinkling of the planet as it cooled. Also, Mercury is believed to have a large iron core that makes up ĺ of its diameter.

Venus
Venus is the closest planet to the Earth, both in distance and size. It is also the third brightest object in the night sky as a result of both its closeness to Earth and the fact that it is covered with highly reflective clouds.

Diameter: 7520 miles(12100 kilometers)
Sun Distance: 67 million miles (108 million kilometers)
Rotation: 243 Earth Days (Retrograde)
Revolution: 221 Earth Days
Mass: .82 Earth
Gravity: .91 Earth
Average Temp.: 870 F (465 C)
Maximum Magnitude: -4.7

Observation
Venus can be seen in the morning of evening sky, depending on whether it is east or west of the Sun. Venus goes through phases, much like Mercury and the Moon. Binoculars will show the crescent phases, but a small telescope would be needed in order to view the full series. Due to the clouds that completely cover Venus, its surface is invisible to us. These clouds also look brighter over the poles thank over the rest of the disk.

Atmosphere and Climate
Venus is enveloped in clouds of sulfuric acid that lie 30-45 miles above its surface. Below these clouds the atmosphere consists mainly of carbon dioxide gas. Due to its highly dense atmosphere, the atmospheric pressure on the surface of Venus is about 90 times that of Earth. The surface winds are gentle, but in the clouds winds reach several hundred miles per hour. The result of this is that the clouds whip around the planet in about 4 Earth days, and, like the planetís rotation, in an east-to-west motion.

Geography and Geology
Most of the surface of Venus is covered by rolling plains that are dotted with mountains and craters formed by meteor impacts. There are two main upland regions; Aphrodite Terra; near the equator and about half the size of Africa, and Ishtar Terra; in the far north and about the size of Australia. Ishtar contains the 7 mile (11 kilometer) tall Maxwell Montes; the highest point on Venus.

Earth
The Earth, where we live, is the largest of the four rocky inner planets. It is unique in that it has a surface abundant in liquid water and an atmosphere rich in nitrogen and oxygen. It is also the only planet known to harbor life.

Diameter: 7926 miles(12756 kilometers)
Sun Distance: 93 million miles (150 million kilometers)
Rotation: 24 hours
Revolution: 365 days
Mass: 6.59 X 10^21 tons
Gravity: 1 Earth
Average Temp.: 59 F (15 C)

Atmosphere and Climate
The atmosphere that surrounds the Earth plays an important role in protecting and sustaining life. It shields the Earth from extreme solar radiation and meteorite impacts. Most importantly, its density, combined with Earthís distance from the Sun, provides the right temperature for liquid water to exist. Circulation in the atmosphere is also important since heat energy is transferred from the equator to the poles.

Geography and Geology
Earthís crust is made up of plates, which float on the viscous mantle and slowly move apart or slip between one another. Mountain ranges, volcanoes, and earthquakes occur along the edges of these plates. The core is made of iron and nickel, the outer part of which is liquid. Motions in this liquid core are what give the Earth its magnetic field.

The Moon
Earthís only natural satellite is so close that its average distance is only 238 900 miles (384 400 kilometers). This is close enough that even a small pair of binoculars will reveal surface features in astonishing detail. There is also no air or liquid water, which means there is o weather on the moon. It is also without geological activity; its main landforms are the results of meteorite impacts.

Diameter: 2160 miles(3476 kilometers)
Earth Distance: 238 900 miles (384 400 kilometers)
Rotation: 27.3 days
Revolution: 29.5 days
Mass: .01 Earth
Gravity: .17 Earth
Average Temp.: 0 F (-18 C)
Maximum Magnitude: -12.7

Observation
Since the Moon rotates on its axis exactly once in the time it takes to orbit the Earth, the same hemisphere (the near side) always faces the Earth. Due to this, we can only see about half of the Lunar surface from Earth. The main features of the moon can be seen with the naked eye; the dark, lowland plains and the lighter colored highlands. With binoculars or a small telescope, innumerable mountain ranges and craters will be revealed. Surface texture is best seen near the day/night border, also called the terminator, when shadows are at their longest. When the surface is illuminated at high angles, such as when the Moon is full, it appears to be washed out and even some craters can seem to disappear. Despite this though, some features need this high contrast in order to be seen at their most prominent, such as the dark maria and the rays around some craters.

The Moon also goes through phases that can easily be observed. At new Moon, the near side of the Moon is completely in shadow. As it orbits the Earth, the visible area grows (or waxes) from a crescent to a gibbous phase to full. Following full, the phases then occur in reverse, as the visible area shrinks (or wanes)

***

Eclipses of the Moon
Every so often, a full Moon will pass into the Earthís shadow and is eclipsed. The entire time the Moon is in shadow can sometimes be as long as 4 hours, and the time the Moon is totally eclipsed may be over an hour. Up to three lunar eclipses may occur in any given year, but some years there are none. Lunar eclipses can be visible on the Earthís surface wherever the Moon is above the horizon.

****

History and Geology
The Moon is believed to be about 4.5 billion years old, forming from when a body the size of Mars impacted with the Earth. Debris from this impact was thrown into orbit and eventually combined to form the Moon. Left over debris bombarded the Moon until about 3.9 billion years ago. Molten lava spewed from inside the Moon, which then created the maria. This process took at least 2 billion years. There is less maria on the far side of the Moon because the crust is thicker there, so less lava reached the surface.

Mars
Mars is a small, rocky planet that in many ways is similar to our Earth. It has a 24 hour day, a pattern of seasons that resembles Earthís, and even polar eyes caps. There are on the other hand, several important differences: the temperatures on the surface of Mars rarely rise above freezing, and the atmosphere is thin and contains almost no oxygen

Diameter: 4220 miles(6790 kilometers)
Sun Distance: 157 million miles (253 million kilometers)
Rotation: 24 hour
Revolution: 1.88 years
Mass: .11 Earth
Gravity: .38 Earth
Average Temp.: -81 F (-63 C)

Observation
Mars is easy to spot with the naked eye most of the year, but is most apparent at times of opposition. Binoculars will show only a tiny red-orange disk, but with even a small telescope the planetís polar ice caps and its largest surface markings can be seen. For a serious observer, a telescope with an 8-inch or larger aperture is recommended. Under magnification of about 100 times Mars will appear to be about as large as the Moon is to the naked eye.

Moons
Mars has two small moons, Phobos and Deimos. Their average diameters are 14 and 7 miles, respectively. Both moons are highly irregularly shaped, and heavily cratered. Modern opinions are that these moons are asteroids captured by the planetís gravity. The moons are too faint to be seen without a large telescope.

Atmosphere and Climate
Mars has an atmosphere that is mainly carbon dioxide. The atmosphere is also so thin that the surface pressure is less than 1% of that on Earth and the average temperature is usually several degrees below freezing. During the winter the atmosphere freezes at the poles, adding a layer of carbon-dioxide frost to the permanent polar caps of ice. In these polar areas high altitude clouds can sometimes be seen from Earth. Dust storms are also a major force of nature on Mars. These storms are usually localized, but when Mars is at its closest the storms can cover the entire planet.

Geography and Geology
Mars can be conveniently divided into two parts. These parts are the Southern Hemisphere, which is mainly a heavily cratered upland, and the Northern Hemisphere, which is smoother and several miles lower in elevation. Mars has several huge volcanoes, the most remarkable being Olympus Mons. This, now dormant, volcano has a base 400 miles wide, and a summit 17 miles high. It dwarves all other volcanoes in the solar system. Not only does Mars have several volcanoes, it also has a spectacular canyon system: Valles Marineris. It is more than 2,500 miles long (one-fifth the planetís circumference) and is visible through a telescope as a dark streak. The surface of Mars is mainly a rock-strewn desert, colored rust by the high levels of iron oxide present.

Jupiter
Jupiter is the largest planet in the solar system, weighing more than twice as much as all the other planets combined. Also, this behemoth has the fastest rotation of all the planets; a mere 10 hours. The visible portions of Jupiterís atmosphere are swirling, markedly banded clouds. Beneath the surface of these clouds the planet is composed mainly of hydrogen and helium, both of which are compressed to the point where they begin to act like metals.

Diameter: 88,000 miles (142,000 kilometers)
Sun Distance: 483 million miles (777 million kilometers)
Rotation: 9 hours, 50 minutes
Revolution: 11.86 years
Mass: 318 Earth
Gravity: 2.36 Earth
Average Temp.: -227 F (-144 C)

Observation
Jupiter is usually the brightest planet following Venus, making it very visible in the night sky. Because of this, even a pair of binoculars can show it as a rounded disc. With a smaller telescope the most prominent clouds bands can be see. If a watchful eye is kept of the planet for about 10-15 minutes, change in the clouds can be seen. Also, through a small telescope, Jupiterís ďeggnessĒ can be seen. Because of its high rotation the planetís equatorial diameter is over 5,600 miles greater than its polar diameter. Jupiter looks its best and brightest at opposition, when a magnification of only 40X will show the planet to be as large as the full Moon looks to the naked eye.

Structure and Atmosphere
A cloudy atmosphere that is approximately 600 miles deep covers Jupiter. Depending on temperature and pressure, both of which increase with depth, different clouds layers of different compositions can be found. Beneath these clouds there is no solid surface, but liquid hydrogen and helium, which have been compressed by Jupiterís gravity. Deep below this is where hydrogen is compressed even further it begins to act like molten metal. Convection in this layer produces the planetís strong magnetic field, which extends for millions of miles into space. Underneath these layers is thought to be a small, rocky core.

Cloud Belts and Storms
Jupiterís rapid rotation and high gravity pulls the planetís gasses into light and dark bands. The lighter bands, called zones, gas rises from the warm interior and condenses to form high-altitude clouds. The darker clouds, called belts, occur at lower altitudes, where gas descends. The color of the belts varies from red to brown to blue, depending on the composition of the gasses. The most prominent feature is the Great Red Spot, which is in effect a massive hurricane. This swirling, high-altitude storm rotates counterclockwise in about a week. It has been tracked scientifically since 1831, but a similar feature is thought to have been seen as early as the 17th century.

Rings and Moons
Jupiter has a faint ring of dust over 60,000 miles wide that is its ring system. Thatís about as exciting it gets! Jupiter has 16 satellites, of which there are three categories: the inner eight, the middle four, and the outer four. The la st two groups are most likely captured asteroids. The inner eight, primarily the four Galilean moons, all have circular orbits on Jupiterís equatorial plane.

Galileo Galilei discovered the Jupiterís four largest moons in 1610, which have oddly enough been named for him. The moons, in order from closest to furthest are Io, Europa, Ganymede, and Callisto. A small telescope can pick them out clearly, appearing as small stars lined up along the equator of Jupiter. Sometimes one or more may be missing, either from passing in front of or behind the planet, or just lost in its shadow.

Saturn
Saturn is the most distant planet known to ancient astronomers, the second largest of the solar system, and the most easily recognizable in a telescope. It is so recognizable because of its broad, bright rings that orbit the planet. Like Jupiter, it has an outer gaseous atmosphere that overlies an interior of liquid hydrogen and helium.

Diameter: 74,000 miles (119,000 kilometers)
Sun Distance: 885 million miles (1.425 billion kilometers)
Rotation: 10 hours, 14 minutes
Revolution: 29.5 years
Mass: 95 Earth
Gravity: .92 Earth
Average Temp.: -285 F (-176 C)

Observation
To the naked eye, Saturn looks like a bright, yellowish star. Through binoculars a small, slightly elongated disk can be seen. Through a small telescope the rings, which are over twice the diameter of the planet itself, can be seen clearly. When under 100X magnification it appears to be the same size as the full Moon to the naked eye.

Structure and Atmosphere
Saturnís structure is fairly similar to Jupiterís, only colder and with a layer of haze, which gives Saturn its creamy complexion. Beneath its clouds, just like on Jupiter, is a layer of liquid hydrogen and helium. Below that is a layer of liquid metallic hydrogen, and below that is a massive core composed of rock and ice. The planetís average density is only about 70% that of water. Because of this and its high period of rotation, the planet has a highly elliptical shape Ė its equatorial diameter nearly 7,500 miles greater than its polar diameter.

Rings and Moons
Saturnís rings consist of a swarm of icy chunks, most of which are miniscule in size, but some can be several feet across. Saturn has 18 known moons. The largest is Titan, which is the only moon in the solar system with a substantial atmosphere. It can easily be picked up by observing Saturn with a small telescope.

Uranus
Uranus, the third-largest planet in the solar system, is also one of the most unique. Primarily because its axis of rotation almost lies on its plane of orbit, and so it sems to orbit the Sun nearly on its side.

Diameter: 31,000 miles (50,000 kilometers)
Sun Distance: 1.8 billion miles (2.9 billion kilometers)
Rotation: 17.2 hours
Revolution: 84 years
Mass: 14.5 Earth
Gravity: .89 Earth
Average Temp.: -355 F (-215 C)

Observation
Under good conditions and if you know its location in the sky, you should be able to spot Uranus with the naked eye. In urban areas binoculars may be needed. If you doubt its identity watch it night to night over a few days and you will begin to notice its movement against the background stars.

Atmosphere and Climate
Uranus is covered by methane clouds, which give the planet its pale green color. It is nearly featureless, but the Voyager 2 spacecraft captured images of small, high-altitude clouds. Because of the planets extreme tilt, through the course of each orbit the Sun appears overhead at the equator and both poles. Each pole receives about 42 years of light, while then experiencing 42 years of darkness. The interior of the planet is most likely different from that of Jupiter and Saturn; mostly consisting of water, methane, ammonia, an rock.

Rings and Moons
Uranus only has 11 thin rings, but they consist of some of the darkest matter known in the solar system. The rings are too faint to be seen from Earth by using a telescope an amateur astronomer would use. All of the planetís 21 moons are too faint as well, the brightest being about 14th magnitude.

Neptune
Neptune, the last of the gas giants, is often regarded as the ďsister planetĒ to Uranus. Like Uranus, Neptune has an atmosphere primarily composed of hydrogen, helium, and methane. Neptune also has a faint ring system, and is similar in size.

Diameter: 31,000 miles (50,000 kilometers)
Sun Distance: 2.8 billion miles (4.5 billion kilometers)
Rotation: 18.5 hours
Revolution: 165 years
Mass: 17.1 Earth
Gravity: 1.12 Earth
Average Temp.: -355 F (-215 C)

Observation
Neptune is never bright enough to be seen by using the naked eye, but it can easily be located and viewed with binoculars. While viewing Neptune, the planetís identity can be confirmed by its gradual movement against background stars from night to night. Through a telescope, the planet will appear to be a bluish disk, only about two-thirds the size of Uranus.

Atmosphere and Climate
The atmosphere of Neptune and Uranus are very similar, but Neptuneís is much bluer due to more methane in the upper levels and is much stormier. Voyager 2 photographed the Great Dark Spot in 1989, which was similar to Jupiterís Great Red Spot. Five years later, when the Hubble Space Telescope was turned towards the planet, the Great Dark Spot had vanished and been replaced by another dark spot on the Northern Hemisphere. Both Voyager 2 and Hubble saw bright streaks of methane cirrus clouds. The exact composition of the planetís main cloud deck is not entirely known, but hydrogen sulfide and ammonia are most likely the most prevalent. Neptuneís interior is believed to be similar to Uranusís, consisting of water, ammonia, and methane above a small, rocky core.

Rings and Moons
Neptune has at least four rings and eight moons, all of which (with the exception of Triton) are too small to be seen with a telescope. Neptuneís rings were photographed by the Voyager 2 spacecraft, which revealed several dense clumps of material deemed ďrings arcs.Ē

The moon Triton is larger than the planet Pluto, and the coldest place known in the solar system with temperatures at nearly Ė400 F. Its surface is covered by nitrogen and methane frost, and liquid nitrogen geysers burst through the surface to leave dark streaks on the planet.

Pluto
Pluto, the tiniest of all the planets, is only about two-thirds the size of our Moon. It is usually the outermost planet, but it has a highly elliptical orbit that, for a short time, brings it closer to the Sun than Neptune. Pluto is also to most recently discovered planet, discovered in 1930. Oddly enough, it is not named after Pluto the cartoon dog, but after the Roman God of War. An 8-year old girl suggested this name, for that reason. Anyone else find anything odd about that?

Diameter: 1,425 miles (2,300 kilometers)
Sun Distance: 3.6 billion miles (5.8 billion kilometers)
Rotation: 6.4 Earth days
Revolution: 248 years
Mass: .0002 Earth
Gravity: .07 Earth
Average Temp.: -369 F (-223 C)

Observation
Pluto is the dimmest of all the planets, and a medium sized telescope would be needed to make it appear as a mere star like point of light. No detail can be seen on its surface. The easiest way to identify Pluto is to study its motion against background stars through a series of photographs taken each night. Plutoís orbit is tilted 17 degrees to that of Earth, so Pluto drifts further from the ecliptic than any other planet.

Structure and Atmosphere
Never having been visited by a space probe, extremely little is known about Pluto. Its surface is believed to be covered by a layer of frozen methane, some of which evaporates to form a thin, temporary atmosphere for a few decades while Pluto is at its closest to the Sun. Below the outer layer of methane ice is believed to be a thick layer of ice, just above a large, rocky core.

Charon
Charon, Plutoís only moon, was not discovered until 1978. It has about half the diameter and one-fifth the mass of Pluto, making it the largest moon in relation to its parent in the solar system. It only orbits 11,400 miles above the planetís surface every 6.4 days. Pluto and Charon spin on their axes in 6.4 days as well, so each body always present the same face to each other.

Vagabonds of the Solar System
Comets, Meteors, and Asteroids; the left over stuff from the creation of the Solar System.

Comets
Comets are icy remnants from the formation of the outer planets. They usually orbit unseen in the Oort Cloud, which extends to at least one light year away from the Sun. Sometimes the gravity of a passing star nudges a comet from the cloud into the inner Solar System so that it can be seen from Earth. Only about 1,000 comets are known, but the Oort Cloud, and its inner region called the Kuiper Belt, are thought to contain billions of them.

Meteors
On any given clear night several bright streaks can be seen in the sky from time to time. They appear suddenly and last for less than a second. These are meteors, caused by specks of comet dust burning up in the uppermost parts of the atmosphere. A handful of random meteors can be seen in an hour, but several times a year the Earth passes through a trail of dust left behind by a comet. Meteors appear to diverge from a single point, called the radiant, and the shower is named after the constellation the radiant is in.



Every day about 10 meteors fall to Earth, called meteoriods. Most land in remote areas or water, and go unnoticed. Over 10,000 have been found on Earth, most long after their fall. They are composed of rock or iron, or a mixture of both. Large meteorites are usually moving fast enough to dig a crater when they hit Earth, but smaller ones are slowed by the atmosphere and drop harmlessly to the surface.

Asteroids
Asteroids, or minor-planets, are small bodies of rock left over from the formation of the Solar System. Only about 10,000 have been discovered, but over a million are believed to exist. Most orbit the Sun in a belt located between Mars and Jupiter, but another large grouping exists in the orbit of Jupiter Ė trailing and leading the planet by 60 degrees. Other smaller groups include the Amor and Apollo asteroids. The Amor group passes through the orbit of Mars, and may one day collide with the planet. The Apollo group passes through the orbit of Earth, and may collide with Earth one day.

The largest asteroid, Ceres, is 580 miles in diameter. The brightest, Vesta, is 360 miles across and can reach a magnitude of 5, making it good for viewing with binoculars. Most asteroids are too faint to be seen, and can only be viewed when they occult, or pass in front of, a star. When this happens, shape, size, and the dynamics of the asteroidís orbit can all be viewed.



* Denotes image taken from Starry Night: Astronomy. For product information visit: Starry Night Astronomy Software
** Denotes image taken from Nature of the Universe
*** Denotes image taken from Phases of the Moon
**** Denotes image taken from The Lunar Eclipse

[edit on 10/27/2004 by cmdrkeenkid]




posted on Oct, 26 2004 @ 08:02 PM
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After this, do you have amything left to post?
FANTASTIC astronomy cmdrkeenkid
I will be making my first forray into astronomy soon. I was supposed to get my first telescope next week, but I got a 21 mph over speeding ticket sunday
After thats taken care of, I think Ill be able to order it. Its an Orion. I dont have the specs right here, But I think it has a 130 mm mirror (Its a reflective type) I think its about 3 and 1/2 feet. I just want to be able to see the rings on Saturn


Thanks agian for all the info.
Great job on the astronomy lesson


[edit on 10/26/04 by Kidfinger]



posted on Oct, 26 2004 @ 08:05 PM
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niiice info. and good read!!!

now i don't have to go to school anymore right???

again, really niiice...





posted on Oct, 26 2004 @ 08:22 PM
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Awesome! I had some Astronomy in collage and had seen much of the info before but had never seen it explained so well.



posted on Oct, 26 2004 @ 08:35 PM
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very nicely done cmdrkeenkid!

now i've got to hunt down your other astronomy posts.


E_T

posted on Oct, 27 2004 @ 11:20 AM
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Originally posted by cmdrkeenkid
Sunspots are “cool” areas in the photosphere associated with huge magnetic field disturbances.
I think this might need defining it little more accurately, they aren't really cool.
Their temperature is still around 4000 Kelvin but that's enough for so big decrease in amount of radiation that they look dark when compared to normal surface.
Here's good picture showing sunspots and granulation which is caused by convection. (just like in boiling water)


Because sun isn't solid object its rotation differs from normal definition of rotation and is called differential rotation in which rotation period varies depending on latitude, being ~25 days at equator and ~36 at poles.
This uneven roation also twists its magnetic field to "spiral" which often goes to "knot" in some place.
Sunspots are consequence of these knots in magnetic field which prevent convection of matter leading to cooler temperature of sunspots.
Because these knots are like stressed springs they store energy and have also other much more important/dramatic consequences which can affect to our life.
When this knot opens/breaks up all that energy stored to it is released in explosion like flare-eruption which releases huge amounts of energy in forms of electromagnetic radiation (UV, X-ray) and high speed charged particles.

Sunspot group 486 (lower one) caused biggest currently known flare:


First animation shows Nov. 4, 2003 X28 superflare in UV and next CME (Coronal Mass Ejection) caused by it: (white circle=sun's size)

Fortunately for us it was directed away from Earth: "In 1989 a flare about half that strong caused a widespread power blackout in Quebec."
The Sun Goes Haywire

Also in other wavelengths sun doesn't anymore look so calm, this picture shows sun in X-ray wavelength.

This image of 1,500,000įC gas in the Sun's thin, outer atmosphere (corona) was taken March 13, 1996 by the Extreme Ultraviolet Imaging Telescope onboard the Solar and Heliospheric Observatory (SOHO) spacecraft. Every feature in the image traces magnetic field structures. Because of the high quality instrument, more of the subtle and detail magnetic features can be seen than ever before. (Courtesy ESA/NASA)


Views of the Solar System - Sun:
www.solarviews.com...
Curious About Astronomy - The Sun:
curious.astro.cornell.edu...

[edit on 27-10-2004 by E_T]



posted on Oct, 27 2004 @ 05:44 PM
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Originally posted by cmdrkeenkid
Iím sure some of you have been looking forward to the next installment, so this is it!



Yep! I was...and it was worth the wait. This is one great post, very informative. Thanks cmdrkeenkid.

I hope it is okay if I post some pictures of planets!
Please tell me if the pictures interrupt the flow of your thread, I'll be happy to remove them.

Planets:

Mercury: Mariner 10, NASA
external image
antwrp.gsfc.nasa.gov...
Other pictures:
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...

Venus: Magellan Project, JPL, NASA
external image
antwrp.gsfc.nasa.gov...
Other pictures:
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...

Earth & Moon: R. Stockli, A. Nelson, F. Hasler, NASA/ GSFC/ NOAA/ USGS
external image
antwrp.gsfc.nasa.gov...

Mars: J. Bell (Cornell U.), M. Wolff (SSI) et al., STScI, NASA
external image
antwrp.gsfc.nasa.gov...
Other pictures:
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...

- Phobos & Deimos
external imageexternal image
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...



posted on Oct, 27 2004 @ 05:45 PM
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Jupiter: Cassini Imaging Team, Cassini Project, NASA
external image
antwrp.gsfc.nasa.gov...
Other pictures:
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...

A few moons of Jupiter:
- Io
external image
antwrp.gsfc.nasa.gov...
- Europa
external image
antwrp.gsfc.nasa.gov...
- Ganymede
external image
antwrp.gsfc.nasa.gov...
- Callisto
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antwrp.gsfc.nasa.gov...
-Thebe, Amalthia, & Metis
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antwrp.gsfc.nasa.gov...

Saturn: Hubble Heritage Team, (AURA / STScI), R.G. French (Wellesley College), J. Cuzzi (NASA/Ames), L. Dones (SwRI), J. Lissauer (NASA/Ames)
external image
antwrp.gsfc.nasa.gov...
Other pictures:
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...
antwrp.gsfc.nasa.gov...

A few moons of Saturn:
- Titan
external image
antwrp.gsfc.nasa.gov...
- Tethys
antwrp.gsfc.nasa.gov...
- Phoebe
external image
antwrp.gsfc.nasa.gov...
- Enceladus
antwrp.gsfc.nasa.gov...
- Mimas
antwrp.gsfc.nasa.gov...
- Rhea
antwrp.gsfc.nasa.gov...

[edit on 27-10-2004 by jp1111]



posted on Oct, 27 2004 @ 06:57 PM
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Originally posted by jp1111
Please tell me if the pictures interrupt the flow of your thread, I'll be happy to remove them.


Not a problem... I would have done it myself, but I figured I'd leave the pictures for whoever else to find.

EDIT: "Have" is not spelled "ahve."

[edit on 10/28/2004 by cmdrkeenkid]



posted on Oct, 28 2004 @ 02:56 PM
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You really should try to write a text book or something, because that's what this post looks like. BTW- What kind of telescope do you use at your house? And, with Earth's surpassing orbit, does that mean that one day the earth will literally move into the sun or that it, along with other planets will move out of the solar system? Because that's very strange!



posted on Oct, 28 2004 @ 03:04 PM
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Bravo, no b.s. excellent
I'm voting way above.



posted on Oct, 29 2004 @ 09:11 AM
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Originally posted by RedDragon
You really should try to write a text book or something, because that's what this post looks like. BTW- What kind of telescope do you use at your house? And, with Earth's surpassing orbit, does that mean that one day the earth will literally move into the sun or that it, along with other planets will move out of the solar system? Because that's very strange!


Actually, the Earth is moving away from the Sun at a fraction of an inch per year. This is because of several reasons, but I'll give the main two: 1.) The Sun is losing mass as it burns its hydrogen fuel, so that weakens its gravitaional pull; 2.) The solar wind is strong enough to where it is able to push the Earth away a bit as well.

Of course though, when the Sun begins to die it'll expand into a red giant star. When this happens the Sun will extend it's size to about the diameter of Mars' orbit.

EDIT: I've got a slew of telescopes. Two at the airport, two at home. Plus I have access to about a dozen plus more here at the university. At home I have an 8-inch Reflector of an unknown make that has optics better than most refractors, and a 2-inch Orion Refractor (fairly craptastic now, but was amazing when I was 6!). At the airport I've got an 18.5-inch Dobsonian, again with great optics, and a 10-inch Schmidt-Cassegrain, with decent optics. I've got about a dozen eyepieces, most of which are at the airport. Here at the university I have access to the 10-inch Refractor, which is a dream come true might I add, and various sizes of Dobs from 8-20 inches.

[edit on 10/29/2004 by cmdrkeenkid]



posted on Jan, 5 2005 @ 10:31 AM
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Hi cmdrkeenkid,

I wonder if you have much experience with the images at SOHO for the sun? If so, could you please comment on something? I caught a peek at something in the mpeg for 12/31 image of the sun that was strange to me. I have no background in science but was trying to catch what an xclass flare looks like so I was surfing their images for that date. At 22:11 on 12/31 the image in the EIT 195 mpg exploded with light. Since I am unfamiliar with this stuff, I was wondering if it was an anomoly of the instruments or something that really happened in the sun. The images and Mpegs all seemed to skip the time of the actual flare by several hours which seemed strange to me, unless it caused some sort of bakeout? By the way, the archives for the mpegs skip it too. They leave off at 12/30 and skip over to 1/04. Is that unusual?

thanks




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