Solar System

MILKY WAY 200 billion stars Diameter LY Height at center LY Solar System is LY from center

in 1999 the Hubble Space Telescope estimated that there were 125 billion galaxies in the universe, and recently with the new camera HST has observed 3,000 visible galaxies. visible

The Local Group is the group of galaxies that includes our galaxy, the Milky Way. The group comprises over 30 galaxies, with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy groupgalaxiesMilky WayAndromeda GalaxygroupgalaxiesMilky WayAndromeda Galaxy

Our solar system consists of: – an average star: the Sun, Sun – the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. –satellites of the planets. –comets (coma, tail)مذنبات comets –asteroids (minor planets, larger than meteoroids but smaller than planets)كويكبات asteroids –meteoroids (small rocks in space)شهب ونيازك –the interplanetary medium (energy, dust, gas)

Comparison

Composition Of The Solar System Sun: 99.85% Planets: 0.135% Comets: 0.01% ? Satellites: % asteroids : % ? Meteoroids: % ? Interplanetary Medium: % ?

The Terrestrial Planets the four innermost planets in the solar system, Mercury, Venus, Earth and Mars. MercuryVenusEarthMars MercuryVenusEarthMars They are called terrestrial because they have a compact, rocky surface like the Earth's. The planets, Venus, Earth, and Mars have significant atmospheres while Mercury has almost none.

The Jovian Planets (Giant Gases) JupiterJupiter, Saturn, Uranus, and Neptune are known as the Jovian (Jupiter-like) planets, because they are all gigantic compared with Earth, and they have a gaseous nature like Jupiter's. SaturnUranusNeptune JupiterSaturnUranusNeptune The Jovian planets are also referred to as the gas giants, although some or all of them might have small solid cores.

Revolution The motion of planets around the sun in their orbits. Rotation The spinning of the planet.

ecliptic The plane of Earth's orbit about the Sun

inclination The inclination of a planet's orbit is the angle between the plane of its orbit and the ecliptic.

Distanc e (AU)AU Radius (Earth's ) Mass (Earth 's) Rotation (Earth 's) # Moons Orbital Inclination Orbital Eccentricity ObliquityDensity (g/cm 3 ) Sun , * Mercury °5.43 Venus °5.25 Earth °5.52 Mars °3.95 Jupiter °1.33 Saturn °0.69 Uranus °1.29 Neptune °1.64 Pluto °2.03

Orbital Period Earth years Avg. Temp. Mercury to 430 Venus Earth1-89 to 58 Mars to 0 Jupiter Saturn Uranus Neptune Age In... You would be... years old. Mercury years Venus years Earth years Mars years Jupiter years 1.85 Saturn years 0.75 Uranus years Neptune years Pluto years Your Age on Other Planets

Obliquity is the angle between a planet's equatorial plane and its orbital plane.

Orbital Eccentricity A value that defines the shape of an ellipse or planetary orbit; the ratio of the distance between the foci and the major axis. plersLaws/index.html plersLaws/index.html

the shape of the ellipse (eccentricity) varies from less eliptical to more elliptical back to less elliptical and take about 100,000 years to complete this cycle. currently, we are in an orbit of low eccentricity (near circular).

Comparisons Mercury: 0.24 days Venus: y Earth: 1 y Mars: 1.88 y Jupiter: 11.8 y Saturn: 29.4 y Uranus: 84 y Neptune: 164 y Pluto: 248 y

Asteroids الكويكبات Asteroids are small rocky objects that move in elliptical orbits in the asteroid belt between the orbits of Mars and Jupiter. asteroid beltasteroid belt Their average distance from the Sun is about 2.9 astronomical units (A.U.) Asteroids are also called minor planets.

asteroids Around 200 asteroids have diameters of more than 100 km. There are thousands of smaller asteroids. There are thousands of smaller asteroids. More than 10,000 asteroids have been cataloged and named so far. All the asteroids in the solar system together weigh much less than the Moon. et/asteroidfact.html et/asteroidfact.html

Kuiper Belt

Ida: 56 x 24 x 21 kilometres video

Meteoroid. When a piece of debris, later to enter the Earth's atmosphere, is traveling through space towards our planet, the object is called a meteoroid. Meteoroid

Meteor The brief flash of light we see in the night sky and caused not by the material "burning" with friction from the atmosphere, but rather from the atoms which have been excited in the air from the object's high speed.

Meteorite The name given to the relatively small number of objects which are not completely destroyed in the upper atmosphere, but survive to the ground.

Scientists estimate the impact by an asteroid even as small as 0.5 km could cause a global climate change due to atmospheric debris restricting sunlight. Impacts by objects 1 to 2 km in size could therefore result in significant loss of life.

Comets The center or nucleus is believed to consist of dust and rock particles held together with ices such as water ice and carbon dioxide ice. Far away from the Sun, the comet is cold, and to an observer close by it would appear as nothing more than a fairly small dead chunk of material. However, as the comet approaches the Sun, it begins to heat up. The ices start to melt, and gases begin to escape from the body, surrounding the nucleus with a glowing cloud called a coma, which may measure more than 100,000 km across (in comparison to the nucleus which may only be a few km in diameter). However, as the comet approaches the Sun, it begins to heat up. The ices start to melt, and gases begin to escape from the body, surrounding the nucleus with a glowing cloud called a coma, which may measure more than 100,000 km across (in comparison to the nucleus which may only be a few km in diameter).

What is next? The distance from the Sun to Proxima Centauri is 4.22 LY. Our fastest space probes would take years to travel this distance.

Are there any objects between the edge of the solar system and the nearest star? There are certainly many asteroids just beyond the orbit of Pluto. This is called the Kuiper belt and may contain tens of thousands of asteroids.