Test: The Earth In The Solar System

• There are eight planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
• The International Astronomical Union (IAU) downgraded the status of Pluto to that of a dwarf planet because it did not meet the three criteria the IAU uses to define a full-sized planet. Essentially Pluto meets all the criteria except one—it “has not cleared its neighbouring region of other objects.”

The Earth and Venus do often get called planetary twins because:

• They are very close to being the same mass.
• Both are rocky planets, therefore they have effectively the same density and resulting very close resemblance of physical size.
• They have significant atmospheres surrounded their surfaces.

The moon orbits the Earth once every 27.322 days. It also takes approximately 27 days for the moon to rotate once on its axis.
As a result, the moon does not seem to be spinning but appears to observers from Earth to be keeping almost perfectly still.

Earth has been called the "Blue Planet" due to the abundant water on its surface i.e. two-third of its surface.
Only 2.5–2.75% is freshwater of which 1.75–2.00% is Frozen in glaciers and ice caps and the rest is available for human use and is available as ground freshwater.

• Planets pull on each other and the Sun also exerts a gravitational pull on them.
• This has the effect of squashing orbits that one might expect to be circular in a closed system resulting in an elliptical shape.

► The Earth spins on its “axis “if we followed this axis out into space from northern hemisphere on Earth, it would point towards a particular star in the sky which is known as the ‘North star’ since it sits in the direction that the spin axis from the northern hemisphere of Earth point.

Early in the history of the solar system, the gravity of newly formed Jupiter brought an end to the formation of planetary bodies in this region and caused the small bodies to collide with one another, fragmenting them into the asteroids we observe today. They lie between Mars and Jupiter.

A constellation is a group of stars that appears to form a pattern or picture. They are easily recognizable patterns that help people orient themselves using the night sky. There are 88 “official” constellations. 

Earth revolves around the sun in 365 days, 5 hours, 59 minutes and 16 seconds.

A group of stars forming various patterns is called a constellation. A huge system of stars is called a galaxy.

A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems.