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Our solar system consists of an average star we call the Sun, the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. It includes: the satellites of the planets; numerous comets, asteroids, and
The Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud.
The Sun is the star at the center of the Solar System
Evolution of Low-Mass Stars :
1-The Sun began its life like all stars asa intersteller cloud.
2-This cloud collapses due to gravity into a dense core.
3. In about a million years a small, hot. dense core called a protostar forms.
4. When the temperature reaches 10,000,000K in the core, fusion begins and transforms
the protostar into a main-sequence star.
5. Low mass stars like the Sun remain on the main-sequence for about 10 billion years.
Note: Massive stars stay on the main-sequence ror about I billion years.
6.hydrogen fusion begins in a shell around the core and the star expands into a Red Giant.
7-after most of the hydrogen is fused into helium. helium fusion begins in an event called the helium flash .
8-Stars can then become unstable and turn into pulsating stars like RR Lyrae variables or cephied variables .
9.As a star burns helium into carbon the radiation pressure pushes the stars"s outer atmosphere away from the core creating a Planetary Nebula.
10-This leaves an exposed core called a white dwarf . Have the same diameter as the Earth.
he Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process.
The sun is the main sourse of energy In the earth .
Earth's Moon is an astronomical body that orbits the planet and acts as its only permanent natural satellite.
Phases of the Moon
The Moon produces no visible light of its own
*It shines only by reflected sunlight
*Surface is very dark, only 7% reflective
During the month, we see a complete cycle of Phases:
*The sunward hemisphere is fully lit.
*The opposite hemisphere is dark.
New Moon & Full Moon
Moon and Sun are on the same side of the sky.
Near side is in total darkness.
Moon and Sun rise together.
Moon is opposite the Sun in the sky.
*The near side is fully illuminated.
*Moon rises as the Sun is setting.
Quarter Moons occur when the Earth, Moon, & Sun are at right angles:
Half of the near side is illuminated
Half of the far side is illuminated
Quarter Moon between New Moon and Full
Quarter Moon between Full Moon and New Moon
Sometimes also called "Third Quarter"
With New Moon and Full Moon, they help to divide the Lunar Month into quarters.
Waxing: inereasing illumination
Waxing Crescent: just after New Moon
Waxing Gibbous: just before Full Moon
Waning: decreasing illumination
Waning Gibbous: just after Full Moon
Waning Crescent: just before New Moon
Mercury planet :
Mercury is the innermost and smallest
planet in the Solar System. It orbits the
Sun once every 87.969 Earth days,
completing three rotations about its axis
for every two orbits. Mercury's orbit has
the highest eccentricity of all the Solar
System planets, and Mercury has the
smallest axial tilt. The perihelion of
Mercury's orbit precesses around the Sun
at an excess of 43 arcseconds per century,
a phenomenon that was explained in the
20th century by Albert Einstein's General
Theory of Relativity. Mercury is bright
when viewed from Earth, ranging from
-2.3 to 5.7 in apparent magnitude, but is
not easily seen as its greatest angular
separation from the Sun is only 28.3°.
Mercury is the innermost planet
Surface: Heavily cratered & virtually no atmosphere
nterior: Large iron core & weak magnetic field. Weak tectonic activity (wrinkles as it cools
Mercury is heavily created,like the moon .
Jumbled terrain .
Daytime: 500K (441 F)
Nighttime: 100K (-279 F)
Some daytime locations are as hot as 600K.
Poles are in perpetual twilight:
*Axis has virtually no tilt.
*118Plar soil is cold: 125 K (-234 F)
Mercury is intermediate in size between the Moon and Mars. We expect:
Thinner lithosphere than the Moon, bul
Thicker than Earth or Mars
See lobate scarps, signs of tectonic disturbance (but NOT plate tectonics):
*Lobate scarps mark thrust faulting.
*The lithosphere wrinkles as Mercury's interior cools and contracts.
Rocky mantle is about 700 km thick.
Unexpectedly large iron core:
75% of the radius of Mercury!
Contains 60% of the planet's mass.
Weak Magnetic Field:
High average density: 5.43 g/cc, compared with Mars which is bigger but only 3.9 g/cc.
1% as strong as Earth's
How did Mercury get such a huge core?
One idea is that during formation Mercury collided nearly head-on with a large body
Collider was smaller than Mercury
Venus, the second planet from the sun, is named for the Roman goddess of love and beauty. The planet Venus — the only planet named after a female — may have been named for the most beautiful deity of her pantheon because it shone the brightest of the five planets known to ancient astronomers.
In ancient times, Venus was often thought to be two different stars, the evening star and the morning star — that is, the ones that first appeared at sunset and sunrise. In Latin, they were respectively known as Vesper and Lucifer. In Christian times, Lucifer, or "light-bringer," became known as the name of Satan before his fall. However, further observations of Venus in the space age show a very hellish environment. This makes Venus a very difficult planet to observe from up close, because spacecraft do not survive long on its surface.
Venus is unusual because it spins the opposite direction of Earth and most other planets. And its rotation is very slow. It takes about 243 Earth days to spin around just once. Because it's so close to the sun, a year goes by fast. It takes 225 Earth days for Venus to go all the way around the sun. That means that a day on Venus is a little longer than a year on Venus.
Since the day and year lengths are similar, one day on Venus is not like a day on Earth. Here, the sun rises and sets once each day. But on Venus, the sun rises every 117 Earth days. That means the sun rises two times during each year on Venus, even though it is still the same day on Venus! And because Venus rotates backwards, the sun rises in the west and sets in the east.
Just like Mercury, Venus doesn’t have any moons.
Venus is the hottest planet in our solar system.
Venus is a terrestrial planet. It is small and rocky.
Venus has a thick atmosphere. It traps heat and makes Venus very hot.
Venus has an active surface, including volcanoes!
Venus spins the opposite direction of Earth and most other planets.
Time on Venus:
A day on Venus lasts 243 Earth days.
A year on Venus lasts 225 Earth days.
Venus does not have any moons.
Venus is the second planet from the Sun. That means Mercury and Earth are Venus’ neighboring
To the naked eye, Venus appears as a white point of light brighter than any other planet or star (apart from the Sun).
as it orbits the Sun, Venus displays phaseslike those of the Moon in a telescopic view. The planet appears as a small and "full" disc when it is on the opposite side of the Sun (at superior conjunction). Venus shows a larger disc and "quarter phase" at its maximum elongations from the Sun, and appears its brightest in the night sky. The planet presents a much larger thin "crescent" in telescopic views as it passes along the near side between Earth and the Sun. Venus displays its largest size and "new phase" when it is between Earth and the Sun (at inferior conjunction). Its atmosphere is visible through telescopes by the halo of sunlight refracted around it
Earth is the third planet from the Sun.
Earth is the only place in the known universe confirmed to host life.
What Does Earth Look Like?
From space, Earth looks like a blue marble with white swirls and areas of brown, yellow, green and white. The blue is water, which covers about 71 percent of Earth's surface. The white swirls are clouds. The areas of brown, yellow and green are land. And the areas of white are ice and snow.
The equator is an imaginary circle that divides Earth into two halves. The northern half is called the Northern Hemisphere. The southern half is called the Southern Hemisphere. The northernmost point on Earth is called the North Pole. The southernmost point on Earth is called the South Pole.
Why Do We Have Day and Night?
At all times, half of Earth is lighted by the sun and half is in darkness. Areas facing toward the sun experience daytime. Areas facing away from the sun experience nighttime. As the planet spins, most places on Earth cycle through day and night once every 24 hours. The North Pole and South Pole have continuous daylight or darkness depending on the time of year.
10 Interesting Facts About Earth
1. Plate Tectonics Keep the Planet Comfortable:
Earth is the only planet in the Solar System with plate tectonics. Basically, the outer crust of the Earth is broken up into regions known as tectonic plates. These are floating on top of the magma interior of the Earth and can move against one another. When two plates collide, one plate will subduct (go underneath another), and where they pull apart, they will allow fresh crust to form.
2. Earth is Almost a Sphere:
Many people tend to think that the Earth is a sphere. In fact, between the 6th cenury BCE and the modern era, this remained the scientific consensus. But thanks to modern astronomy and space travel, scientists have since come to understand that the Earth is actually shaped like a flattened sphere (aka. an oblate spheroid).
3. Earth is Mostly Iron, Oxygen and Silicon:
If you could separate the Earth out into piles of material, you’d get 32.1 % iron, 30.1% oxygen, 15.1% silicon, and 13.9% magnesium. Of course, most of this iron is actually located at the core of the Earth. If you could actually get down and sample the core, it would be 88% iron. And if you sampled the Earth’s crust, you’d find that 47% of it is oxygen.
70% of the Earth’s Surface is Covered in Water:
When astronauts first went into the space, they looked back at the Earth with human eyes for the first time. Based on their observations, the Earth acquired the nickname the “Blue Planet:. And it’s no surprise, seeing as how 70% of our planet is covered with oceans. The remaining 30% is the solid crust that is located above sea level, hence why it is called the “continental crust”.
5. The Earth’s Atmosphere Extends to a Distance of 10,000 km:
Earth’s atmosphere is thickest within the first 50 km from the surface or so, but it actually reaches out to about 10,000 km into space. It is made up of five main layers – the Troposphere, the Stratosphere, the Mesosphere, the Thermosphere, and the Exosphere. As a rule, air pressure and density decrease the higher one goes into the atmosphere and the farther one is from the surface.
6. The Earth’s Molten Iron Core Creates a Magnetic Field:
The Earth is like a great big magnet, with poles at the top and bottom near to the actual geographic poles. The magnetic field it creates extends thousands of kilometers out from the surface of the Earth – forming a region called the “magnetosphere“. Scientists think that this magnetic field is generated by the molten outer core of the Earth, where heat creates convection motions of conducting materials to generate electric currents
7.Earth Doesn’t Take 24 Hours to Rotate on its Axis:
It actually takes 23 hours, 56 minutes and 4 seconds for the Earth to rotate once completely on its axis, which astronomers refer to as a Sidereal Day. Now wait a second, doesn’t that mean that a day is 4 minutes shorter than we think it is? You’d think that this time would add up, day by day, and within a few months, day would be night, and night would be day
8. A year on Earth isn’t 365 days:
It’s actually 365.2564 days. It’s this extra .2564 days that creates the need for a Leap Year once ever four years. That’s why we tack on an extra day in February every four years – 2004, 2008, 2012, etc. The exceptions to this rule is if the year in question is divisible by 100 (1900, 2100, etc), unless it divisible by 400 (1600, 2000, etc).
9. Earth has 1 Moon and 2 Co-Orbital Satellites:
As you’re probably aware, Earth has 1 moon (aka. The Moon). Plenty is known about this body and we have written many articles about it, so we won’t go into much detail there. But did you know there are 2 additional asteroids locked into a co-orbital orbits with Earth? They’re called 3753 Cruithne and 2002 AA29, which are part of a larger population of asteroids known as Near-Earth Objects (NEOs).
10. Earth is the Only Planet Known to Have Life:
We’ve discovered past evidence of waterand organic molecules on Mars, and the building blocks of life on Saturn’s moon Titan. We can see amino acids in nebulae in deep space. And scientists have speculated about the possible existence of life beneath the icy crust of Jupiter’s moon Europa and Saturn’s moon Titan. But Earth is the only place life has actually been discovered
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