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PAGE CONTENTS:
Our Galaxy - The Milky Way
The Sun
The Moon
Jupiter
Mars
Mercury
Neptune
Saturn
Pluto
Uranus
Venus
OUR GALAXY - THE MILKY WAY
The planets in the solar system rotate anticlockwise, except Venus,
Uranus and Pluto which rotate clockwise. No one knows why.
Tenth Planet Discovered
While not necessarily an American History event, the discovery
of the tenth planet in our solar system was big news and was announced on July 29th. The American astronomers proved the existence
of the planet located further out than Pluto. It had been postulated for 75 years. It has yet to be named, currently designated
as 2003 UB313. It is slightly larger than Pluto, has a small moon - about 155 miles across - and takes more than
500 Earth years to orbit the Sun.
The average surface temperature of the outer planets–
Uranus, Neptune, Pluto – is about -364 degrees F, 11 times colder than inside a home freezer.
The star Zeta Thaun, a supernova, was so bright when it exploded in 1054
that it could be seen during the day.
The average surface temperature of the outer planets– Uranus, Neptune,
Pluto – is about -364 degrees F, 11 times colder than inside a home freezer.
Light takes one-tenth of a second to travel from New York to London, 8
minutes to reach the Earth from the Sun, and 4.3 years to reach Earth from the nearest star.
Our galaxy has approximately 250 billion stars - and it is estimated by
astronomers that there are 100 billion other galaxies in the universe.
Traveling at the speed of 186,000 miles per second, light take 6 hours
to travel from Pluto to Earth.
A light-year is how far light travels in one year, which is about 5.9 trillion
miles.
How big is the Milky Way?
If the Milky Way Galaxy
was the size of the U.S.A., Earth would be far smaller than the smallest particle of dust, barely visible through the most
powerful microscopes.
How many stars lie within the Milky Way?
The
Milky Way has approximately 250 billion stars - and it is estimated by astronomers that there are 100 billion other galaxies
in the universe.
What's the most common type of galaxy?
Three-quarters
of the galaxies in the universe are spiral galaxies. There are three other types of galaxies: elliptical, irregular, and lenticular.
What order are the planets in, exactly?
It's
easy to remember the order of the planets with this line: My Very Eager Mother Just Served Us Nine Pizzas. The capital letters
stand for the order of the planets, starting closest to the sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune,
and Pluto. That is, except for between January 1979 and March 1999 when, because of a large orbital eccentricity, Pluto was
closer to the sun than Neptune.
WHEN WERE THE PLANETS DISCOVERED?
Mercury,
Mars, Venus, Jupiter, and Saturn were known from ancient times. Uranus was discovered in 1781, Neptune in 1846, and Pluto
in 1930.
THE SUN
The Sun is about midway in the scale of star sizes, but most are smaller ones. Only five percent of the stars in our
galaxy are larger than the Sun. (That's five billion larger stars, however.)
As recently as half a century ago, there was no clear understanding as to why the sun shines. The discovery
that it is due to nuclear-fusion reactions was not made until the 1930s, by Hans Beth and Carl von Weizsacker.
The Sun is colossal. It contains 99.8 percent of the total
mass of the solar system. More than one million Earths would be required to match its volume.
If a pin was heated to the same temperature
as the center of the Sun,its heat would set alight everything within 60 miles of it.
The Sun's solar wind
is so powerful, it has large effects on the tailsof comets, and scientists have determined that it even has measurable
effects on the trajectories of spacecraft.
How much of our solar system is in the sun?
The
sun contains over 99.8 percent of the total mass in our solar system, while Jupiter contains most of the rest. The fractional
percentage that is left is made up of our Earth and moon and the remaining planets and asteroids.
Four million tons of hydrogen dust are destroyed on the Sun
every second.
The smallest visible sunspots have an area of 500 million square
miles, about fifty times the size of Africa. The largest sunspots have an area of about 7,000 million square miles.
A cosmic year is the amount of time it takes the Sun to revolve
around the center of the Milky Way, about 225 million years.
The pressure at the center of the Sun is about 700 million tons
per square inch. It's enough to smash atoms, expose the inner nuclei, and allow them to smash into each other, interact, and
produce the radiation that gives off light and warmth.
The Sun is 330,330 times larger than Earth.
More than one million Earths would fit inside the sun.
The Sun contains over 99.8 percent of the total mass in our
solar system, while Jupiter contains most of the rest. The fractional percentage that is left is made up of our Earth and
moon and the remaining planets and asteroids.
The sun is 93 million miles from earth, yet it's 270,000 times
closer than the next nearest star.
The Sun is about midway in the scale of star sizes, but most
are smaller ones. Only five percent of the stars in our galaxy are larger than the Sun. (That's five billion larger stars,
however.)
The sun has "burned" for more than 4.5 billion years and will
continue to do so for several billion more. It is a massive collection of gas, mostly hydrogen and helium. Because it is so
massive, it has immense gravity, enough gravitational force to hold all of hydrogen and helium together (and to hold all of
the planets in their orbits around the sun!).
The sun burns 9 million tons of gas a second. At this rate,
it has been estimated it will burn out in another 10 billion years.
Four million tons of hydrogen dust are destroyed on the Sun
every second.
The smallest visible sunspots have an area of 500 million square
miles, about fifty times the size of Africa. The largest sunspots have an area of about 7,000 million square miles.
A cosmic year is the amount of time it takes the Sun to revolve around
the center of the Milky Way, about 225 million years.
The pressure at the center of the Sun is about 700 million tons per square
inch. It's enough to smash atoms, expose the inner nuclei, and allow them to smash into each other, interact, and produce
the radiation that gives off light and warmth.
The Sun is 330,330 times larger than Earth.
More than one million Earths would fit inside the sun.
The sun has "burned" for more than 4.5 billion years and will continue
to do so for several billion more. It is a massive collection of gas, mostly hydrogen and helium. Because it is so massive,
it has immense gravity, enough gravitational force to hold all of hydrogen and helium together (and to hold all of the planets
in their orbits around the sun!).
The smallest visible sunspots have an area of 500 million square miles,
about fifty times the size of Africa. The largest sunspots have an area of about 7,000 million square miles.
The weight of the Sun is two billion billion billion tons, about 333,420
times that of the Earth.
The sun burns 9 million tons of gas a second. At this rate, it has been
estimated it will burn out in another 10 billion years.
Is our sun running out of time?
The Sun's total
lifetime as a star capable of maintaining a life-bearing Earth is about 11 billion years. Nearly half the time has passed.
Sun's Core
The temperature at the sun's core
is thought to be about 15 million degrees C (27 million degrees F), by far the hottest temperature in the solar system. The
material there is plasma, a gas of electrons and atomic nuclei, compressed to about ten times the density of lead. The sun's
nuclear fusion reactions only happen in the innermost core, where the pressure and temperature are high enough to fuse hydrogen
into helium. The energy generated there starts out as high energy gamma rays and x-rays, not as visible light. The energy
released by fusion makes its way out from the core through several layers, colliding with the dense plasma all the way. It
takes about a million years for each photon (energy "particle") to reach the surface of the sun. By that time the energy has
been divided and down- shifted by collisions, until it's mostly visible light.
How much energy does the sun produce?
The Sun
produces more energy every minute than all the energy used on Earth in a whole year.
WHY DO THE SUN AND MOON APPEAR MUCH LARGER WHEN POSITIONED
NEAR THE HORIZON THAN WHEN HIGHER IN THE SKY?
This apparent difference in size is known as the "moon illusion".
To our eyes, the sky at the horizon seems more distant than the sky overhead. When we see the moon against the "more distant"
horizon sky, it appears larger than when seen against the "closer" overhead sky.
THE MOON
If the moon were placed on the surface of the continental UnitedStates,
it would extend from San Francisco to Cleveland (2,600 miles).
The Moon weighs 81 billion tons.
The Sea of Tranquility is on the Moon. It’s not a real sea, but a
“maria,” one of the regions on the Moon that appear dark when looking at it.
A full moon rarely shows up on Halloween, although Halloween is often associated
with full moons. Full moons on Halloween over the past century have occurred in 1925, 1944, 1955, and 1974. The next full
moon on October 31 will occur in 2020.
How much brighter than a half Moon is a full Moon?
You
might expect that a full moon would be twice as bright as a half moon, since the bright part is twice as large in the sky.
But a full moon is actually nine times as bright as a half Moon. Even one day before a full moon, its brightness is about
30% less. The full moon's greater brightness is related to the sun's angle of illumination of the moon's irregular surface.
When you are looking at a half moon, you see not only the parts of the craters, rocks, and mountains that are in sunlight,
you also see the shadows they cast. Since the moon has no atmosphere to spread out the light, the shadows are deep and dark.
When the moon is full, the sun's light comes from almost directly behind us. As a result we see no shadows, only the illuminated
parts of all the moon's features. Even the flat maria (plains) are brighter, because their surfaces are composed of tiny dust
particles, each of which casts a shadow that's invisible when the moon is full.
JUPITER
JUPITER WEIGHS OVER TWICE AS MUCH AS ALL THE OTHER KNOWN PLANETS COMBINED.
All the planets in our solar system could be placed inside Jupiter.
Jupiter spins faster than any other planet. A point on the equator of
Jupiter spins faster around the center of the planet at a speed of 28,273 mph. The speed of the spin makes the planet bulge
slightly at its equator.
Jupiter is the largest planet, and
it has the shortest day. Although Jupiter has a circumference of 280,000 miles, compared with Earth's 25,000, Jupiter manages
to make one turn in 9 hours and 55 minutes.
Jupiter is the planet with the shortest day: slightly under 10 hours. However, its years are 12 times as long as ours.
MARS
Afternoon temperatures on Mars go up to about 80 degrees in some
areas, and down to -190 degrees F at night.
Is Mars really red?
The fourth planet from
the Sun (between the Earth and Jupiter), Mars has long been referred to as the Red Planet because it appears to shine with
a reddish hue when viewed from Earth. However, recent NASA photographs indicate that the planet isn't really red at all -
but is more of a tan or butterscotch color
How long is a day on Mars?
The diameter of
Mars is approximately 4219 miles, considerably smaller than that of the Earth (7926 mi). But a Martian day is surprisingly
similar in length to one on Earth (24 hours and 37 minutes), while a Martian year is nearly twice as long (687 days).
Does Mars have a moon?
Yes, in fact it has
two, Diemos and Phobos, both of which are irregularly shaped and pitted with craters. Diemos orbits Mars once every 31 hours;
Phobos speeds through the Martian sky three times a day, circling the planet every seven hours.
Phobos, one of the moons of Mars, is so close to its parent planet that
it could not be seen by an observer standing at either of Mars poles. Phobos make three complete orbits around Mars every
day.
Can a human live on Mars?
Probably not - The
Martian atmosphere is very different from Earth and is composed primarily of carbon dioxide (95.32%), with small amounts of
other gases, such as Nitrogen (2.7%), Argon (1.6%), and Oxygen (0.13%). Martian air contains only 1/1000th as much water as
Earth's air, but it can still condense to form clouds, fog, and even frost. The average recorded temperature on Mars is a
chilly -81°F, with a maximum temperature of 68° F and a minimum of -220° F.
What about the face on Mars?
Perhaps the most
enduring image from the surface of Mars (and certainly the most controversial) is that of "The Face," which was first photographed
by Viking Orbiter 1 in 1976. Subsequent images from the Mars Global Surveyor spacecraft of this outcropping in the Cydonia
region show that it is nothing more than a bumpy hill. The face-like quality was the result of video compression and distortion.
WHAT IS THE LARGEST MOUNTAIN IN THE SOLAR SYSTEM?
The
largest mountain in the Solar System is Olympus Mons on Mars. At a height of over 26 km (16 miles), it is nearly three times
taller than Mt. Everest. Olympus Mons is also enormous in its width: 600 km (360 miles) across.
A COLDER, DRIER MARS
Many believe that the
giant canyons on Mars were carved by ancient water rivers, but Nick Hoffman of La Trobe University in Melbourne now claims
that they were carved by dense flows similar to the flows of gas, ash and rubble that sometimes erupt from Earth volcanoes.
If true, Mars has probably been cold and lifeless for the past 3.5 billion years, far longer than most scientists believe,
according to a report in this week's edition of New Scientist. The flows might have resulted from the collapse of unstable
Martian terrain followed by release of liquid carbon dioxide from underground caches. The liquid carbon dioxide would have
vaporized upon reaching the surface to form fire extinguisher-like clouds of gas and supercooled dry ice, water ice, dust,
and rubble. When they swept downhill, these clouds would have carved out the valleys that still exist today. "It's intriguing
and fascinating, but I'm very skeptical," says planetary scientist Jay Melosh of the University of Arizona in Tucson. He believes
that, as the carbon dioxide vaporized, the flows would have rapidly run out of steam before they could do much damage.
HOW LONG IS A DAY ON MARS?
24 hours, 37 minutes,
and 22 seconds.
Martian Ice
Evidence continues to mount that Mars has massive amounts
of water--albeit water frozen into sheets of ice. Why does that matter? Because water is key to life as we know it, and all
that Martian ice might just contain actual extraterrestrial life.
Scientists perusing erosion patterns on Mars's surface
have long theorized that the Red Planet was once a watery world. But in the last few years, they've found a virtual flood
of new evidence. Some highlights:
-
In 2004, NASA announced that its Mars rovers had gathered
direct evidence that water once washed over the Red Planet.
-
In 2006, Mars scientists published before-and-after pictures
containing "the strongest evidence to date that water still flows occasionally" on the planet's surface.
-
In 2007, scientists studying Mars's southern polar ice
cap announced that it likely contains enough water to cover the entire planet with a sea 36 feet (11 meters) deep--if the
ice ever melts.
And the evidence just keeps coming. NASA scientists
announced that new data from the Mars Reconnaissance Orbiter suggests the Red Planet's poles aren't its only icy parts. Using
a special "shallow radar" system that lets them peer beneath Mars's surface, they've determined that distinctive dome-shaped
geological features in Mars's mid-latitudes likely contain large deposits of ice.
Of course, finding ice is not the same as finding life.
But it does raise some interesting questions--like, what's life like on Mars, if there is any?
Think little green microbes, not little green men. Mars
is mild compared to some planets, but life there would need both sunscreen and mittens. The planet gets a decent amount of
light, which is crucial for photosynthesis. But the Martian atmosphere is too weak to provide protection from the damaging
solar energy that comes with it. The result is a cosmic bombardment of lethal radiation many times more powerful than what
we get here on Earth.
And for all that radiation, Mars is still a pretty cold
place, about -81 degrees Fahrenheit (-63 degrees Celsius) on average. On a warm day, in a warm place, it can feel like spring
on Earth. But most of the time, in most places, Mars makes Antarctica look tropical. That's fine for a virtual skate like
this one, but hardly hospitable for living things that need liquid water, like us.
--Steve Sampson and Christopher Call
KnowledgeNews is brought to you by Every Learner, Inc.,
an independent small business dedicated to supporting lifelong learners. Copyright © 2007, Every Learner, Inc. All rights
reserved.
MERCURY
If you were on the planet Mercury, it would seem like a year
or more from one day to the next. That's because Mercury, being close to the sun, revolves around it in only 88 days, completing
one year. But it takes twice as long as that for Mercury to make one full rotation on its axis thus completing a full day.
Source:
FASCINATING FACTS by David Louis
PLUTO
The smallest planet in our solar system, Pluto, is a little smaller than
Earths moon.
Some astronomers believe Pluto's strange and erratic orbit indicates
that it wasn't one of the original planets at all, but rather, a moon of Neptune that somehow broke loose.
The most eccentric orbit of any planet in the solar system belongs to
Pluto, a ball of rock and ice smaller than Earth's Moon. With its even smaller companion, Charon, Pluto traces an elliptical
orbit in the outer reaches of the solar system. When it is closest to the Sun, Pluto is 2.8 billion miles out (4.4 billion
km), which is closer than Neptune. But the outer end of its long path is 4.6 billion miles from the Sun (7.5 billion km).
For all but twenty years of its 248-year orbit, Pluto is the outermost known planet in the solar system. Pluto's unusual orbit
has an effect on the planet. When it is closest to the Sun some of the ice on its surface evaporates, giving Pluto a thin
atmosphere probably composed of nitrogen, carbon monoxide, methane, and other light gases. That atmosphere condenses into
snow when the planet is farther from the Sun.
The planet Pluto takes 248 Earth years to orbit the Sun. For 20 of those
years, it is closer to the Sun than the planet Neptune. The nature of its orbit, however, always prevents it from colliding
with Neptune.
NEPTUNE
The discovery of Neptune was announced in 1846. But when astronomers checked previous records, they found the record
of an observation of the planet as far back as 1795 by astronomers who, believing it to be a star, recorded the position routinely.
The coldest place in the solar system is the surface of Neptune's largest
moon Triton, which has a temperature of -391 degrees Fahrenheit, only 69 degrees Fahrenheit above absolute zero.
SATURN
Saturn would float on water if there was an ocean large enough to accommodate
it because of its density. However, Saturn is 95 times heavier than the Earth.
Saturn's Rings
The really spectacular thing about Saturn remains the rings. All
the gaseous giants in our solar system--Jupiter, Saturn, Uranus, and Neptune--have them. But not like Saturn's. So, inquiring
minds want to know, how did the broad and beautiful rings of Saturn form?
Astronomers figure that our sun formed within a giant cloud of gas
and dust. Drawn together by gravity, particles in this cloud coalesced into a rotating pool heated by the energy of the gravitational
collapse. In time, this rotating pool was dense enough and hot enough to fire up as a star.
The leftover material around the new star eventually flattened into
a similarly rotating disk. Again drawn together by gravity, particles in the disk coalesced into rotating pools. But this
time, there simply wasn't enough material to fire up stars. Instead, the pools made planets.
Something similar may have been at work to create the myriad moons
around planets like Jupiter, Saturn, Uranus, and Neptune--miniature solar systems all. Maybe, some scientists say, Saturn's
rings are just cold bits of primordial soup that never managed to make a moon.
Nonsense on stilts, say other scientists. That may be how solar
systems form, but it's not how Saturn and its bright rings did. Surely rings 4.6 billion years old would be dirtier, they
say, marred by all kinds of dust and debris--like week-old snow. Saturn's rings shine like a new penny.
And surely by now gravitational forces would have cut ancient rings
down to size, like the smaller, darker rings of Jupiter, Uranus, and Neptune. Saturn and its rings are the widest planetary
body in the solar system.
No, these scientists think that Saturn's rings are a very recent
(and perhaps even recurring) phenomenon--such that if dinosaurs had invented telescopes, Galileo Rex might well have spied
a ringless Saturn.
Several hundred million years ago, perhaps a cold, moon-sized object
from the outer solar system flew too close. Saturn's gravity captured it, and tidal forces ripped it apart. Or maybe a renegade
meteor smashed into one of Saturn's own icy moons and broke it apart. Either way, the bright bits of ice in orbit made broad
and beautiful rings.
It may add up. The mass of all the icy chunks and bits throughout
Saturn's rings amounts to about one medium-sized moon--for despite their reach, the rings are only tens of meters thick. They
are, many scientists now think, fragile, dynamic things that only a bit of cosmic luck lets us see.
--Michael Himick
KnowledgeNews is brought to you by Every Learner,
Inc., an independent small business dedicated to supporting lifelong learners. Copyright © 2007, Every Learner, Inc. All rights
reserved.
URANUS
The seventh planet from the Sun, Uranus, is tipped on its side so that
at any moment one pole is pointed at the Sun. The polar regions are warmer than the equator. At the poles, a day lasts for
42 Earth years, followed by an equally long night.
VENUS
On Venus, the Sun rises in the west and sets in the east, the oppositeof the Earth. Venus rotates
from east to west, not from west to eastas the Earth and the other planets do.
Venus is much brighter than any other planet or star. At its brightest
it can cast shadow, and even be seen during the day time.
The planet Venus does not tilt as it goes around the Sun, so consequently,
it has no seasons. On Mars, however, the seasons are more exaggerated and last much longer than on Earth.
The planet Venus is enveloped by an atmosphere of sulfuric acid. (Source:
About.com)
Venus has no magnetic field, perhaps because of its slow rotation. It also
has no satellites.
Venus is much brighter than any other planet or star. At its brightest
it can cast shadow, and even be seen during the day time.
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