Beyond the Blue Skies

Our Solar System is the Sun and the planetary system around it. A “planetary system” is a group of non-stellar object (planets, dwarf planets, moons, asteroids, meteoroids, comets and cosmic dust) which orbit around a star.

The Solar System includes four terrestrial planets (composed of mostly rock and metal) and four gas giants (massive masses formed by mostly gaseous material). The four terrestrial planets are Mercury, Venus, Earth, and Mars, and the four gas giants are Jupiter, Saturn, Uranus, and Neptune. These names are derived from Roman gods and goddesses.  So how many planets have we mentioned thus far?

Eight!  Just seeing if you are still with me.  :)

Scientists believe that the Solar System formed about 4.6 billion years ago with the gravitational collapse of a cluster of gas and dust particles in space. The Sun formed out of the masses in the center, and the rest of the material slowly formed other non-stellar objects, like planets, moons, and asteroids. The Solar System has evolved considerably since, and is still continuing to evolve. It is said that the Sun is almost halfway in the cycle that began at its birth and ending with its final expansion and collapse as a red giant (the 10 billionth year mark of its life).

Not Just Planets

The Solar System also includes the planets’ satellites (moons), comets, asteroids, and meteoroids. Also, between Mars and Jupiter lies a small asteroid belt. Despite there being only eight planets, the Solar System actually contains hundreds of worlds, and we are talking minor planets and moons, some of which are larger than Mercury! Io has active volcanoes. Europa has a thick liquid water ocean layer, though covered by thick crusts of solid ice. Titan has lakes, rivers, and oceans of liquid Methane!

Beyond Neptune’s orbital path lie trans-Neptunian formations made of mostly iced water, ammonia, and methane, such as Ceres, Pluto, Haumea, Makemake, and Eris. These five formations are rounded by their own gravities like planets are; however, by scientific standards they are termed as “dwarf planets.”

Atmospheres, Rings, Magnetic fields

Nearly every planet, and some moons, is shrouded by an atmosphere of gases. Venus has a thick atmosphere of carbon dioxide and many toxic gases. Earth’s atmosphere consists of mostly nitrogen and oxygen. Mars’ atmosphere is mostly carbon dioxide and is very thin. The gas giants contain mostly hydrogen and helium in their atmospheres.

From the 17th century to the 1970s, astronomers believed that only Saturn had an outer ring. With the advent of modern telescopes, scientists can now study rings on Jupiter, Uranus, as well as Neptune, although these planets’ rings are not nearly as prominent as Saturn’s. What are seen as planetary rings are actually massive clusters of various particles ranging in size from dust-, to boulder-, and to house-like volumes!

Many planets in the Solar System have magnetic fields, spaces around planets and stars which sweep charged particles with them. The sun has a magnetic field called the heliosphere, which extends all throughout the Solar System.

The Sun

The Sun is the star at the center of the Solar System.  It consists of hot lava and a strong magnetic fields.  The energy from it comes from many hydrogen nuclear fusion reactions at its core.  The Sun holds about 99.86% of the mass in our Solar System, with the most of the rest belonging to Jupiter.  The Sun consists of about 70% hydrogen, 28% helium, and 2% of the remaining consists of carbon, oxygen, iron, neon, and other elements.

By classification the Sun is a yellow dwarf.  It is about the top 10th percentile in mass among all stars.  It has a surface temperature of about 5505 degrees Celsius.

The hot corona of the Sun is constantly expanding, thus producing the solar wind (charged particle stream that is emitted from the Sun’s upper atmosphere).  The solar wind is responsible for creating the heliosphere, which is a very, very large bubble that expands into the outer area of the Solar System known as the interstellar medium.  Phenomena such as geomagnetic storms can completely disrupt Earth’s power grid, Northern Lights, as well as comet plasma tails which are always aligned away from the Sun.

The Sun is often personified in many ancient cultures, more often than not it is a deity or god.  The ancient Egyptians knew it as the god Ra, the Greeks knew it as Helios, and the Romans knew it as Sol.

The Planets

Mercury
Mercury is the smallest and closest planet to the Sun. Mercury has no moons and has no special features other than impact craters and lobed ridges. Mercury’s thin atmosphere consists of particles blasted off by the solar wind from the Sun. It has a large iron core and a thin mantle layer, possibly due to constant impacts which prevent its layers from developing over time.

Venus
The second planet is slightly smaller than Earth. It has a dense atmosphere and an iron core. It is the hottest planet with blistering surface temperatures (over 400 degrees Celsius). Venus’ atmosphere is very toxic due to clouds of sulfuric acid. The planet may have had water at one point of time, but these have evaporated over time due to the extreme heat. Volcanic activity have been observed on Venus’ surfaces, though there have been no signs of lava flow.

Earth
Earth is the largest of the inner planets. It is one of the few, if not only, places in the universe where life exists. It has one moon, the Moon. Earth core is very active, and it is the only planet with tectonic plates. Earth’s biosphere has long since altered its atmosphere, creating more oxygen as well as an ozone layer to block harmful radiation from its surfaces.

Mars
This is the second largest planet and the fourth from the Sun. Mars has a carbon dioxide atmosphere. It has two moons: Deimos and Phobos. These are said to be captured asteroids. Its reddish color is due to the large amounts of iron-oxide on its surface. Its atmosphere is very thin and its surface is ridden with impact craters, like that of the Moon’s.

Jupiter
Jupiter is the size of 318 Earth masses. It is the largest planet in the Solar System with 2.5 the mass of all the other planets combined. It is composed of mostly hydrogen and helium. Jupiter has 63 known satellites. Jupiter has a rapid rotation which has caused it bulge slightly around its equator. The atmosphere of Jupiter creates lots of storms on its surface, the prominent result of which is the Great Red Spot, which is actually a continuous storm which has endured since the 17th century (when it was first observed by telescope).

Saturn
This planet is just beyond Jupiter and is known for its large ring, which actually consists of 9 bands of rings. Saturn is about 60% the volume of Jupiter and has the lowest density of all the planets. It has 62 satellites, including Titan and Enceladus. Saturn’s core consists of iron, nickel, silicon, and oxygen compounds, all surrounded by a thick layer of metallic hydrogen. The planetary magnetic field on Saturn has contributed to an electric current through the metallic hydrogen layer.

Uranus
Uranus is unique in that it orbits the sun on its side because of its axial tilt. Uranus has 27 known moons, including Titania, Oberon, Umbriel, Ariel, and Miranda. While Uranus is similar to Jupiter and Saturn in that its atmosphere contains hydrogen and helium, it also contains copious amounts of iced water, ammonia, and methane. Furthermore, it has the coldest atmosphere in the Solar System at -224 deg C. Uranus and Neptune are also termed “ice giants.”

Neptune
Neptune is smaller than Uranus but is denser. Neptune has 13 known satellites, including Triton. Neptune’s surface gravity is only surpassed by Jupiter, and the two are the only planets with surface gravities greater than Earth’s. Neptune contains iced compounds like those of Saturn’s as well as greater concentrations of volatile elements found on Jupiter and Saturn.

Pluto
Pluto used to be considered a planet in the sense that the Mercury or Jupiter is. However, it is now considered a dwarf planet because it lacks characteristics that define the planets in the Solar System.