THE 8 PLANETS
NEXT STOP: VENUS!
An inferno fireball on the inside, a smooth yellow marble on the outside. Venus, the two-faced planet known as “heaven and hell.” Beautiful yet dangerous, Venus is rightfully named after the Roman goddess of love and beauty. In modern culture, people associate Venus with beauty products… and Venus Williams, the world champion tennis player.
Shrouded by its thick sulfuric cloud atmosphere, Venus is the second planet from the Sun and the hottest planet on average in the solar system. Also known as the Morning Star or Evening Star, Venus reflects sun light strongly, with a high albedo. Because Venus’ size is similar to Earth’s, Venus is sometimes to referred to as “Earth’s twin” or “Earth’s sister.” Other than size, however, Venus and Earth have nothing in common. Venus’ atmosphere rains sulfuric acid on the dry dessert-like surface! Its thick atmosphere (90 times thicker than Earth’s) composed of mainly CO2 traps carbon dioxide (greenhouse effect) and maintains a searing temperature on Venus. Venus may have harbored water once, but rising temperatures evaporated all liquid water, leaving a volcanically active surface. Mapped in 1990-1991 by Project Magellan, Venus’ surface comprises of 80% smooth, volcanic plains (70% plains with wrinkled ridges and 10% smooth plains) and 20% two highland “continents” Aphrodite Terra and Ishtar Terra. Venus has little impact craters but various volcanic features such as “novae” (star-like fracture systems) and “arachnoids” (spider-web-like fractures). Scientists know little about Venus’ interior without seismic data, but Venus’ size and density suggest an interior similar to Earth’s. Scientists have attempted to build probes to land on Venus’ surface, but all attempts failed (most only enter Venus’ atmosphere then burn up and crash). Venus’ clouds reflect and scatter 90% of sunlight, so scientists can only map its surface with radar. In fact, Venus’ atmosphere has an ozone layer and its clouds can produce lightning! Unlike any other planet, Venus spins from east to west, in a retrograde motion. Because Venus spins backward, its rotational period is longer than its orbital period; a day on Venus is longer than a year! Unlike Earth, Venus has a negligible magnetic field, unable to divert most solar wind. Like Mercury, Venus undergoes phases as seen from Earth. When Venus is in a crescent phase observers can actually see a mysterious ashen light. In the 17th century, Galileo proved the heliocentric theory with observations of Venus’ phases. Though Venus has no moons, scientists believe the planet had at least one that crashed into its surface. 10 million years after the collision, another impact changed Venus’ spin. Another possibility is that strong solar tides can disturb large satellites. Recently, the Transit of Venus occurred in June, when the planet crossed over the Sun.
MISSIONS: Venera, Sputnik, Mariner, Cosmos, Vega, Pioneer Venus, Magellan, Cassini, MESSENGER, Venus Express
*Many of these missions (Sputnik, Mariner) are series with only some successful and some only fly-bys; Venera is exclusive for Venus
- Order in Solar System: #2
- Number of Moons: 0
- Orbital Period: 225 days
- Rotational Period: 243 days
- Mass: 4.8685 x 10^24 kg (0.815 Earths)
- Volume: 9.28 x 10^11 km³ (0.866 Earths)
- Radius: 6,052 km (0.9499 Earths)
- Surface Area: 4.60 x 10^8 km² (0.902 Earths)
- Density: 5.243 g/cm
- Surface Pressure: 9.3 MPa
- Eccentricity of Orbit: 0.2
- Surface Temperature (Average): 735 K
- Escape Velocity: 10.36 km/s
- Apparent Magnitude: -4.9 (crescent) to -3.8 (full)
On December 3, 2012, the planets Mercury, Venus, and Saturn will align with the Giza Pyramids in Egypt. This will be the first planetary/pyramid alignment in 2,737 years! Now, the three Giza pyramids are also in perfect alignment with the three stars of Orion’s belt. In 1983, Robert Bauval proposed this Orion correlation theory and published this idea in Discussions in Egyptology in 1989. The Giza pyramids were built in the 3rd millennium B.C. The alignment is very curious. Could the Egyptians have built the Giza pyramids that way on purpose?
- Eccentricity of Orbit: measures the ellipticity of orbit (ranges 0-1, with 0 as spherical and 1 as very elliptical)
- Density: mass per unit volume; mass in grams and volume in cubic centimeters
- Oblateness: measures how much the middle section of the planet bulges
- Surface Gravity: the larger the surface gravity, the thicker the atmosphere as gravity pulls in more gases
- Albedo: measures the fraction of light reflected compared to the amount of light received from the Sun; the higher the albedo, the more reflective the surface
- Escape Velocity: minimum speed or velocity needed to escape the planet’s gravitational pull
- Rotation: most planets rotate in counter-clockwise direction (prograde); others rotate in the clockwise direction (retrograde)
- Rotational period is shortest for gaseous planets and longest for Venus
- Roche Limit: about two and a half times the radius of the planet; within the Roche Limit, matter cannot accretes to form moons because the tidal force of the planet tears matter apart to form rings
Giant Planets: Giant planets have lighter elements such as hydrogen and helium in their atmospheres. They have stronger gravity and are at larger distances from the Sun. Jupiter, Saturn, and Neptune are stormy with great spots of lasting storms and belts and zones. However, Uranus is comparatively bland and uniform. All giant planets are home to convection, or hot gases rising and cold gases falling.
Terrestrial Planets: Terrestrial planets have heavier elements such as carbon, oxygen, and nitrogen. Mercury is most heavily cratered while Earth is least cratered. Larger terrestrial planets have plate tectonics. Earth has a sizable magnetic fields that can protect it from solar wind particles and Van Allen Belts. Earth has the “Goldilocks phenomenon,” or the right conditions for the development of life.
“The Planets” sub-page under the “The Solar System” page has now been complete and updated with pictures and additional information. Part I includes the terrestrial planets: Mercury, Venus, Earth, and Mars! See the page here.
The Transit of Venus is set to occur on June 12, 2012 in the late afternoon. Venus will appear as a black dot on the sun. This rare event will not occur for another 105 years.