2. MERCURY
Mercury is the closest planet to the Sun and is also the smallest of the eight
planets in our solar system. For every 2 orbits of the Sun, which takes around 88
Earth days, Mercury completes three rotations of its axis. It is gravitationally
locked and this rotation is unique to the solar system.
Every seven years or so, Mercury can be seen from Earth passing across the
face of the Sun. This happens because Mercury’s orbit is inclined by 7 degrees to
the plane of Earth’s orbit and its known as a transit. The next transit of Mercury
is on May 9, 2016 and will be visible from Europe after noon.
It is named for the Roman god Mercury, the messenger to the gods – most
likely related to the orbiting speed of the planet.
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4. A year in Mercury is 88 days, yet a Mercury day is 176 Earth
days. Mercury is nearly tidally locked to the Sun – also known as a
gravitational lock – and over time this has slowed the rotation of the
planet to almost match its orbit around the Sun.
Mercury orbits so quickly around the Sun that early civilizations
believed it was actually two different stars – one which appeared in the
morning and another which appeared in the evening.
Mercury is the smallest planet in the solar system with a diameter of
4,879 km and is one of five planets that is visible to the naked eye.
After the Earth, Mercury is the second densest planet.Despite its small
size, Mercury is very dense because it is composed mainly of heavy metals
and rock – the main characteristic of terrestrial planets.
5. Mercury is named after the messenger of the Roman gods, who is
also known as Hermes in Greek mythology. This is because of the speed
in which Mercury orbits the Sun and the speed with which Mercury the
Roman deity was able to deliver messages.
Astronomers didn’t realize that Mercury was a planet until 1543
when Copernicus published his Sun-centered model of the Solar
System – putting the Sun as the centre of the solar system rather than
the previously believed centre, the Earth.
Mercury has no moons or rings because of its low gravity and lack of
atmosphere.
Mercury does not experience any seasons. The axis of Mercury
has the smallest tilt of all other planets, and this results in a lack of
seasons on its surface.
6. Mercury is only the second hottest planet. Venus, though
farther from the Sun than Mercury, actually experiences higher
temperatures. This is because Mercury has no atmosphere to
regulate temperature and results in the most extreme
temperature change of all the planets – ranging from -170°C (-
280°F) during the night to 430°C (800°F) during the day.
Mercury is the only planet which doesn’t rotate exactly
once every year – instead rotating three times for every two
orbits of the Sun. This is because it is nearly tidally locked to
the Sun.
Mercury has a weak magnetic field whose strength is about
1% of the magnetic field on Earth.
7. Mass: 330,104,000,000,000 billion kg
(0.055 x Earth)
Equatorial Diameter: 4,879 km
Polar Diameter: 4,879 km
Equatorial Circumference: 15,329 km
Known Moons: None
Notable Moons: None
Orbit Distance: 57,909,227 km (0.39 AU)
Orbit Period: 87.97 Earth days
Surface Temperature: -173 to 427°C
First Record: 14th Century BC
Recorded By: Assyrian astronomers
8. VENUS
Venus is the second planet from the Sun and the third brightest
object in Earth's sky after the Sun and Moon. It is sometimes
referred to as the sister planet to Earth, because their size and mass
are so similar. Venus is also the closest planet to Earth. The surface
of Venus is hidden by an opaque layer of clouds which are formed
from sulphuric acid.
The planet is named for Venus, the Roman goddess of love and
beauty and is the second largest terrestrial planet.
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10. Venus is the second brightest natural object in the sky. The planet has an
apparent magnitude of -3.8 to -4.6, which makes it visible on a bright, clear day. The
Moon is the only other natural object that is brighter.
Venus is sometimes referred to as the “morning star” and “evening star”. This
dates back to ancient civilizations who believed that Venus was in fact two distinct
stars appearing in the sky. When the orbit of Venus overtakes Earth’s orbit, it
changes from being visible at sunrise to being visible at sunset. They were known as
Phosphorus and Hesperus by the Greeks, and Lucifer and Vesper by the Romans.
One day on Venus is longer than one year. Due to the slow rotation on its axis, it
takes 243 Earth-days to complete one rotation. The orbit of the planet takes 225
Earth-days – making a year on Venus shorter on day on Venus.
Venus is named after the Roman goddess of love and beauty. This may be, in
part, due the brightness of the planet and may date back to the Babylonians in 1581
who referred to Venus as “bright queen of the sky”.
11. Venus is sometimes called Earth’s sister planet. This is because their size is very
similar (there is only a 638 km different in diameter) and Venus has around 81% of
Earth’s mass. They are also similarly located with Venus being the closest planet to
Earth. Both planets also have a central core, a molten mantle and a crust.
Venus has no moons nor rings.
Billions of years ago, the climate of Venus may been similar to that of Earth and
scientists believe that Venus once possessed large amounts of water or oceans.
However, due to the high temperatures produce from the extreme greenhouse
effect, this water boiled off long ago and the surface of the planet is now too hot
and hostile to sustain life.
Venus rotate in the opposite direction to other planets. Most other planets
rotate counter-clockwise on their axis, however Venus, like Uranus, rotates
clockwise. This is known as a retrograde rotation and may have been caused by a
collision with an asteroid or other object which caused the planet to change its
rotational path.
12. Venus is the hottest planet in the solar system with an average surface
temperature of 462°C (863°F). Also, Venus doesn’t tilt on its axis which means there
are no seasons either. The atmosphere is a dense 96.5% carbon dioxide which traps
heat and caused the greenhouse effect which evaporated any water sources billions
of years ago.
The temperature on Venus doesn’t vary much between the night and day. This is
due to the slow movement of the solar winds across the surface of the planet.
The estimated age of the Venusian surface is around 300-400 million years
old. By comparison, the surface of the Earth is about 100 million years old.
Venus has a very weak magnetic field. This surprised scientists, who expected
Venus to have a magnetic field similar in strength to Earth’s. One possible reason for
this is that Venus has no solid inner core, or that its core is not cooling.
Venus is the only planet in the Solar System to be named after a female figure.
13. Mass: 4,867,320,000,000,000 billion kg
(0.815 x Earth)
Equatorial Diameter: 12,104 km
Polar Diameter: 12,104 km
Equatorial Circumference: 38,025 km
Known Moons: None
Notable Moons: None
Orbit Distance: 108,209,475 km (0.73 AU)
Orbit Period: 224.70 Earth days
Surface Temperature: 462° C
First Record: 14th Century BC
Recorded By: Babylonian astronomers
14. MARS
Mars is the fourth planet from the Sun and last of
the terrestrial planets . Like the rest of the planets in the
solar system (except Earth), Mars is named after a
mythological figure - the Roman god of war. In addition to
its official name, Mars is sometimes called the Red
Planet because of the brownish-red color of its surface.
Mars is the third smallest planet in the solar system after
Mercury.
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16. Mars is the fourth planet from the Sun and last of the terrestrial planets
and is around 227,940,000 km from the Sun.
The planet is named after Mars, the Roman god of war. It was known to
the ancient Greeks as Ares, their god of war. This is thought to be because
of the blood-red color of the planet which was also used by other ancient
cultures. Chinese astronomers call Mars the “fire star” while ancient
Egyptian priests called it “Her Desher” meaning “the red one”.
Pieces of Mars have been found on Earth. It is believed that trace
amounts of the Martian atmosphere were within meteorites that the
planet ejected. These meteorites then orbited the solar system for millions
of years amongst the other objects and solar debris before eventually
entering the Earth’s atmosphere and crashing to the ground. The study of
this material has allowed scientists to discover more about Mars before
launching space missions
17. The tallest mountain known in the solar system is on Mars. Olympus Mons is a
21 km high and 600 km diameter shield volcano that was formed billions of years
ago. Scientists have found a lot of recent evidence of volcanic lava which suggests
Olympus Mons may still be active. It is the second highest mountain in the entire
solar system, topped only by the Rheasilvia central peak on the asteroid Vesta,
which is 22 km high.
Mars experiences huge dust storms – the largest in our solar system. This is due
to the elliptical shape of the planet’s orbit path around the Sun. The orbit path is
more elongated than many of the other planets and this oval shaped orbit results in
fierce dust storms that cover the entire planet and can last for many months.
With the exception of Earth, Mars is the most hospitable to life – a number of
space missions are planning for the next decade the further increase our
understanding of Mars and when it has the potential for extraterrestrial life, as well
as whether it may be a viable planet for a colony.
It takes Mars 687 Earth days to orbit the Sun with its orbit radius of 227,840,000
km.
18. Mass: 641,693,000,000,000 billion kg (0.107 x
Earth)
Equatorial Diameter: 6,805 km
Polar Diameter: 6,755 km
Equatorial Circumference: 21,297 km
Known Moons: 2
Notable Moons: Phobos & Deimos
Orbit Distance: 227,943,824 km (1.38 AU)
Orbit Period: 686.98 Earth days (1.88 Earth years)
Surface Temperature: -87 to -5 °C
First Record: 2nd Millenium BC
19. JUPITER
Named after the Roman king of the gods, Jupiter is fitting of its
name. With a mass of 1.90 x 1027 kg and a mean diameter of
139,822 km, Jupiter is easily the largest and most massive planet
in the Solar System. To put this in perspective, it would take
11 Earths lined up next to each other to stretch from one side of
Jupiter to the other and it would take 317 Earths to equal the mass
of Jupiter.
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21. Jupiter has 67 confirmed moons orbiting the planet. These moons are
separated into three groups:
Inner moons. These orbit the closest to Jupiter and are sometimes called
the Amalthea group. The names of the inner moons of Jupiter are Metis,
Adrastea, Amalthea, and Thebe.
The first recorded sighting of Jupiter were by the ancient Babylonians in
around 7th or 8th BC. It is named for Jupiter, the king of the Roman gods and
god of the Sky. The Greek equivalent is Zeus, god of thunder. For the
Mesopotamians, he was the god Marduk and patron of the city of Babylon.
Germanic tribes saw the planet as Donar, also known as Thor.
Jupiter has the shortest day of the eight planets. The planet rotates very
Jupiter rotates very quickly, turning on its axis once every 9 hours and 55
minutes. This rapid rotation is also what causes the flattening effect of the
planet, which is why it has an oblate shape.
22. One orbit of the Sun takes Jupiter 11.86 Earth years.This means that when viewed from
Earth, the planet appears to move very slowly in the sky. It takes months for Jupiter to move
from one constellation to the next.
Jupiter has a faint ring system around it. Its ring is mostly comprised of dust particles
from some of Jupiter’s moons during impacts from comets and asteroids. The ring system
begins about 92,000 km above Jupiter’s clouds and reaches more than 225,000 km from the
planet. The rings are somewhere between 2,000-12,500 km thick.
Jupiter has at least 67 moons in satellite around the planet. This includes the four large
moons called the Galilean moons that were first discovered by Galileo Galilei in 1610.
The largest of Jupiter’s moons, Ganymede is the largest moon in the solar system. The
moons are sometimes called the Jovian satellites and the largest of them
are Ganymede, Callisto, Io and Europa. Ganymede is larger than the planet Mercury with a
diameter of around 5,268 km.
Jupiter has a very strong magnetic field. This is around 14 times stronger than the
magnetic field found on Earth – the largest of any planet in the solar system.
23. Jupiter does not experience seasons like other planets such as Earth
and Mars. This is because the axis is only tilted by 3.13 degrees.
Jupiter’s Great Red Spot is an enormous storm that has been raging
for over 300 years. This storm is so wide that three Earth’s would fit
inside of it.
Jupiter is the fourth brightest object in our solar system. After the
Sun, the Moon and Venus, Jupiter is the brightest and is one of five
planets which can be seen by naked eye from Earth.
Jupiter has a very strong magnetic field. This is around 14 times
stronger than the magnetic field found on Earth – the largest of any
planet in the solar system.
24. Mass: 1,898,130,000,000,000,000 billion kg (317.83 x
Earth)
Equatorial Diameter: 142,984 km
Polar Diameter: 133,709 km
Equatorial Circumference: 439,264 km
Known Moons: 67
Notable Moons: Io, Europa, Ganymede, &Callisto
Known Rings: 4
Orbit Distance: 778,340,821 km (5.20 AU)
Orbit Period: 4,332.82 Earth days (11.86 Earth years)
Surface Temperature: -108°C
First Record: 7th or 8th Century BC
Recorded By: Babylonian astronomers