Space Today Online - Moons of the Solar System SPACE TODAY ONLINE ~~ COVERING SPACE FROM EARTH TO THE EDGE OF THE UNIVERSE Moons of the Solar System Massive planet Jupiter below the moon Io click NASA image to enlarge A moon is a natural satellite rotating around a planet. While moons vary in size, each moon is much smaller than its planet. Almost 140 moons are known in the Solar System. Several moons are larger than the planet Pluto and two moons are larger than the planet Mercury. There also are many small moons that may be asteroids captured by their planets. Only Mercury and Venus do not have any moons. By comparison, Earth has one moon and Mars has two. Jupiter has the most of any planet. Saturn is second. Pictures taken by the Hubble Space Telescope suggest there may be even more moons around those outer planets. earth's moon » Largest. The largest moon is Ganymede with a diameter of 3,280 miles, even larger than either of the planets Mercury and Pluto. Saturn's moon Titan is the second largest in the Solar System with a diameter of 3,200 miles, half again as large as Earth's Moon.

The Planets and Their Moons PLANET Jupiter 62 Io, Europa, Ganymede, Callisto, Amalthea, Himalia, Elara, Pasiphae, Sinope, Lysithea, Carme, Ananke, Leda, Metis, Adrastea, Thebe, Callirrhoe, Themisto, Kalyke, Iocaste, Erinome, Harpalyke, Isonoe, Praxidike, Megaclite, Taygete, Chaldene, Autonoe, Thyone, Hermippe, Eurydome, Sponde, Pasithee, Euanthe, Kale, Orthosie, Euporie, Aitne, plus others yet to receive names Saturn 33 Titan, Rhea, Iapetus, Dione, Tethys, Enceladus, Mimas, Hyperion, Prometheus, Pandora, Phoebe, Janus, Epimetheus, Helene, Telesto, Calypso, Atlas, Pan, Ymir, Paaliaq, Siarnaq, Tarvos, Kiviuq, Ijiraq, Thrym, Skadi, Mundilfari,

 Erriapo, Albiorix, Suttung, plus others yet to receive names Uranus 27 Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck, Miranda, Ariel, Umbriel, Titania, Oberon, Caliban, Sycorax, Prospero, Setebos, Stephano, Trinculo, plus others yet to receive names Neptune Triton, Nereid, Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, plus others yet to receive names Pluto 139 Saturn.

When the Cassini spacecraft from Earth arrived at Saturn in 2004, it promptly found two previously unseen moons. They turned out to be the smallest bodies seen until then around the ringed planet. The tiny natural satellites are about 2 miles and 2.5 miles in diameter. That's smaller than the city of Boulder, Colorado. Previously, the smallest moons seen around Saturn were are about 12 miles across. The moons are 120,000 miles and 131,000 miles from the center of planet Saturn between the moons Mimas and Enceladus. The newly discovered bodies were labeled S/2004 S1 and S/2004 S2. Later, they will be given names. The NASA JPL team wondered if S/2004 S1 might not be an object called S/1981 S14 that had turned up in a 1981 Voyager image. Saturn moons » Smallest.

The smallest moon is Deimos, at Mars, only seven miles in diameter, although its size now is rivaled by the small shepherd moons discovered by Cassini at Saturn and by others yet to be counted and named in the rings around Jupiter, Saturn and other giant gas planets in the outer Solar System. There may be tiny moons as small as only around a mile across. Pluto. Charon is the moon closest in size to its planet, Pluto. Earth's Moon is second in that comparison. Neptune. The interplanetary probe Voyager 2 in 1989 found six previously-unknown moons orbiting Neptune. They ranged in diameter from 33 miles to 250 miles. In 1991, they were named Naiad, Thalassa, Despina, Galatea, Larissa, Proteus. The names Galatea and Larissa were controversial since asteroids previously had been given those names. Names are assigned by the nomenclature committee of the International Astronomical Union (IAU). Triton. Before Voyager 2, astronomers knew Neptune had two moons, Triton and Nereid.

With a surface temperature of –391 degrees, Triton was found by Voyager 2 to have a thin veneer of methane and nitrogen on top of water ice on its surface. Triton had been thought to have a diameter of 2,361 miles, close in size to Earth's Moon, but turned out to be smaller, around 1,690 miles. Nereid is 210 miles in diameter. Pan. A new moon only 12 miles in diameter was discovered in 1990 circling the planet Saturn. It was Saturn's 18th and most distant moon. Photos of the planet, moons and rings, left over from the 1981 Saturn flyby by Voyager 2, had been filed away at NASA's Ames Research Center in Mountain View, California, for a decade. A planetary scientist was tipped off to Pan's presence by a disturbance in a 200-mi.-wide gap — Encke's Gap — in Saturn's outermost A ring. Pan's gravity moved particles in the large A ring, creating a gap with waves along the edges like the wake of a motorboat.

Checking the wavy edges, he calculated the probable position and mass of the moon and compared them with Voyager 2 positions and camera angles in 1980-81. When finally uncovered, the moon stood out as a small bright spot in 11 pictures among 30,000 photos scanned by a computer. In 1991, the moon officially was named Pan. It was the second time since Neptune was discovered in 1894 that a gravity disturbance had been used to pinpoint a previously-unknown Solar System body. Inner Solar System. The inner Solar System includes the planets Mercury, Venus, Earth and Mars. Of all the known moons in our Solar System, only three are in the inner region. Mars has two. Earth has one. Mercury and Venus are the only planets without moons. The outer Solar System includes Jupiter, Saturn, Uranus, Neptune and Pluto and the rest of the moons. More moons are discovered each year in the outer Solar System by astronomers using ever more powerful equipment. Atmospheres. Most moons are airless, but Jupiter's Io, Saturn's Titan and Neptune's Triton seem to have atmospheres. Titan may be flooded with an ocean of liquid ethane.

Triton may be covered by an ocean of liquid nitrogen. Io seems to have a thin sulphur dioxide atmosphere from volcanos. Titan. Titan appears to have an organic chemistry in its atmosphere which may resemble the primitive Earth before the dawn of life. It is the only moon known to have a thick, organic-rich nitrogen atmosphere. Surface temperature is around –290 degrees Fahrenheit. Solar System's moons are listed below: Exploring the Moons of the Outer Solar System The moons of the outer planets are popular targets with planners of future spaceflights. Jupiter has more moons than any other planet. Its best known moons are the four large planet-sized bodies Io, Europa, Ganymede and Callisto. jupiter » Callisto is the outermost of the four and the most heavily cratered body in the Solar System. It may have a vast water ocean indside. Io is innermost of the four. This sulfurous moon is the most volcanic world in our Solar System. It is peppered with hundreds of volcanoes, several of which might be active at any given moment. Europa has an icy surface that may hide a layer of warm slush or even liquid water.

That would make it one of the few places in the Solar System with that life-sustaining liquid. Ganymede is the largest moon of Jupiter and the largest moon in the Solar System. In fact, Ganymede is larger in diameter than the planet Mercury and much larger than the planet Pluto. Ganymede has its own magnetic field. Saturn has some unique moons. Here are some examples: Titan is Saturn's largest moon. Mimas has an enormous crater – probably a hole caused by a meteorite. Enceladus has a very bright surface. It may have active water volcanoes. Tethys has a canyon running three-quarters of the way around its surface. That means it may once have been split almost in half. Dione and Rhea have wispy white markings on one side. Hyperion is oddly shaped and the length of its day is constantly changing. Iapetus is half bright and half dark. Pan, by comparison, is a very tiny moon. Its diameter is only 20 km, which on the sale above would be only half the size of a BB. Uranus' moons are eye-openers. They have statuesque mountains towering more than ten miles high. Incredibly deep valleys.

Vast plains, some with a mysterious dark surface. Moon diameters range from a bit fatter than 25 miles up to about 1,100 miles. The Solar System: Pictures and Information on the Sun, Moon, Moon Phases, Planets Pictures & Information on the Sun, Moon & Eight Planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) Information on our Solar System There are now officially only eight planets in our solar system (in 2006 the International Astronomical Union changed the definition of 'planet' so that Pluto no longer qualifies). The Solar System consists of the Sun and the other celestial objects gravitationally bound to it: eight planets, their 165 known moons, three dwarf planets (including Pluto) and their four known moons, and billions of small bodies (which includes asteroids, comets, meteoroids). Our Solar System - Eight planets orbit the Sun Animated View of our Solar System The display advances at the rate of about 3 days per second. Click on a planet to view its fact sheet.

In order of their distances from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Six of the eight planets are in turn orbited by moons. All the planets except Earth are named after gods and goddesses from Greco-Roman mythology. The Sun The Sun is by far the largest object in the solar system. It is the star at the center of the Solar System. The Earth and other matter (including other planets, asteroids, meteoroids, comets and dust) orbit the Sun. Energy from the Sun (sunlight) supports almost all life on Earth via photosynthesis, and drives the Earth's climate and weather. The Sun contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest). At present, the mass of the Sun is about 70% hydrogen, 28% helium by mass, other metals amount to less than 2%. This changes slowly over time as the Sun converts hydrogen to helium in its core. The Sun's energy output (3.86e33 ergs/second or 386 billion billion megawatts) is produced by nuclear fusion reactions.

As it travels out toward the surface, the energy is continuously absorbed and re-emitted at lower and lower temperatures so that by the time it reaches the surface, it is primarily visible light. Mercury Mercury is the innermost and smallest planet in the solar system, orbiting the Sun once every 88 days. It can only be seen in morning or evening twilight. Physically, Mercury is similar in appearance to the Moon as it is heavily cratered. It has no natural satellites and no substantial atmosphere. The planet has a large iron core which generates a magnetic field about 0.1% as strong as that of the Earth. Mercury is one of the four terrestrial planets, being a rocky body like the Earth. It consists of approximately 70% metallic and 30% silicate material. The density of the planet is the second-highest in the solar system at 5.43 g/cm³, only slightly less than Earth’s density. Venus Venus is the second planet from the Sun and the sixth largest. Venus' orbit is the most circular of that of any planet, with an eccentricity of less than 1%.

Venus (Greek: Aphrodite; Babylonian: Ishtar) is the goddess of love and beauty. The planet is so named probably because it is the brightest of the planets known to the ancients. The phases of Venus can be viewed with a telescope from Earth. Galileo's observation of this phenomenon was important evidence in favor of Copernicus's heliocentric theory of the solar system. Venus' rotation is very slow (243 Earth days per Venus day). In addition, the periods of Venus' rotation and of its orbit are synchronized such that it always presents the same face toward Earth when the two planets are at their closest approach. Venus is sometimes regarded as Earth's sister planet. In some ways they are very similar: * Venus is only slightly smaller than Earth (95% of Earth's diameter, 80% of Earth's mass). * Both have few craters indicating relatively young surfaces. * Their densities and chemical compositions are similar. Earth Earth is the third planet from the Sun and the fifth largest. Home to the human species, it is also referred to as "Planet Earth", "Gaia", "Terra", and "the World". 71% of the Earth's surface is covered with water.

The Earth is the first planet known to have liquid water on the surface and is the only place in the universe known to harbor life. The heat capacity of the oceans is also very important in keeping the Earth's temperature relatively stable. The Earth formed around 4.57 billion years ago. At present, the Earth orbits the Sun once for every 366.26 times it rotates about its axis (which is equal to 365.26 solar days). The Earth's axis of rotation is tilted 23.5° (away from the perpendicular to its orbital plane), producing seasonal variations on the planet's surface. The Earth is divided into several layers which have distinct chemical and seismic properties. The crust varies considerably in thickness, it is thinner under the oceans, thicker under the continents. Unlike the other terrestrial planets, Earth's crust is divided into several separate solid plates which float around independently on top of the hot mantle below. The Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and water. Earth has a magnetic field that, together with a primarily nitrogen-oxygen atmosphere, protects the surface from radiation that is harmful to life.

Mercury, Venus, Earth & Mars The Earth's Moon The Moon makes a complete orbit around the Earth every 27.3 days, and the periodic variations in the geometry of the Earth - Moon - Sun system are responsible for the lunar phases that repeat every 29.5 days. The gravitational attraction, and the centrifugal forces generated by the rotation of the Moon and Earth around a common axis, the barycentre, is largely responsible for the tides on Earth. The Moon is the only celestial body that humans have travelled to and landed on. The US Apollo program has achieved the first (and only) manned missions to date, resulting in six landings between 1969 and 1972. Phases of the Earth's Moon The Lunar phase refers to the appearance of the illuminated portion of the Moon as seen by an observer on Earth. The Moon exhibits different phases as the relative geometry of the Sun, Earth and Moon change, appearing as a full moon when the Sun and Moon are on opposite sides of the Earth, and becoming invisible as a new moon (also named dark moon) when they are on the same side.

Lunar phases of the moon - A full moon is when the sun and moon are on opposite sides of the Earth Mars Mars is the fourth planet from the Sun in the Solar System. The planet is named after Mars, the Roman god of war. It is also referred to as the "Red Planet" because of its reddish appearance as seen from Earth. Mars has a thin atmosphere and some of the most varied and interesting terrain of any of the terrestrial planets. It is the site of Olympus Mons, the highest known mountain in the solar system, and of Valles Marineris, the largest canyon. In addition to its geographical features, Mars’ rotational period and seasonal cycles are likewise similar to those of the Earth. Of all the planets in our solar system, Mars is the most likely, other than Earth, to harbor liquid water, and perhaps life. Mars can be seen from Earth with the naked eye, a brightness surpassed only by Venus, the Moon, and the Sun (and at times Jupiter). Jupiter Jupiter is the fifth planet from the Sun and by far the largest. Jupiter is more than twice as massive as all the other planets combined (the mass of Jupiter is 318 times that of Earth).

Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus). In 1610 Galileo first pointed a telescope at the sky and discovered Jupiter's four moons Io, Europa, Ganymede and Callisto (now known as the Galilean moons) and recorded their motions back and forth around Jupiter. This was the first discovery of a center of motion not apparently centered on the Earth. It was a major point in favor of Copernicus's heliocentric theory of the motions of the planets. Jupiter, along with Saturn, Uranus, and Neptune, is classified as a gas giant. It is not primarily composed of solid matter but is 93% hydrogen and 7% helium; it may also have a rocky core of heavier elements. Because of its rapid rotation the planet is an oblate spheroid (it possesses a slight but noticeable bulge around the equator). Saturn Saturn is the sixth planet from the Sun and the second largest. Galileo was the first to observe it with a telescope in 1610; he noted its odd appearance but was confused by it.

Early observations of Saturn were complicated by the fact that the Earth passes through the plane of Saturn's rings every few years as Saturn moves in its orbit. A low resolution image of Saturn therefore changes drastically. It was not until 1659 that Christiaan Huygens correctly inferred the geometry of the rings. Like Jupiter, Saturn is about 75% hydrogen and 25% helium with traces of water, methane, ammonia and "rock". Two prominent rings (A and B) and one faint ring (C) can be seen from the Earth. Though they look continuous from the Earth, the rings are actually composed of innumerable small particles each in an independent orbit. They range in size from a centimeter or so to several meters. The rings are extraordinarily thin: though they're 250,000 km or more in diameter they're less than one kilometer thick. The ring particles seem to be composed primarily of water ice, but they may also include rocky particles with icy coatings. The rings of Saturn When it is in the nighttime sky, Saturn is easily visible to the unaided eye.

Though it is not nearly as bright as Jupiter, it is easy to identify as a planet because it doesn't 'twinkle' like the stars do. The rings and the larger satellites are visible with a small astronomical telescope. Uranus Uranus named after the Greek god of the sky, is the seventh planet from the Sun. It is a gas giant, the third largest by diameter and fourth largest by mass. Uranus, the first planet discovered in modern times, was discovered by William Herschel while systematically searching the sky with his telescope on March 13, 1781. Most of the planets spin on an axis nearly perpendicular to the plane of the ecliptic but Uranus' axis is almost parallel to the ecliptic. At the time of Voyager 2's passage, Uranus' south pole was pointed almost directly at the Sun. This results in the odd fact that Uranus' polar regions receive more energy input from the Sun than do its equatorial regions. Uranus is nevertheless hotter at its equator than at its poles. Uranus is composed primarily of rock and various ices, with only about 15% hydrogen and a little helium.

Its atmosphere is about 83% hydrogen, 15% helium and 2% methane. Uranus' blue color is the result of absorption of red light by methane in the upper atmosphere. There may be colored bands like Jupiter's but they are hidden from view by the overlaying methane layer. Like the other gas planets, Uranus has rings. Like Jupiter's, they are very dark but like Saturn's they are composed of fairly large particles ranging up to 10 meters in diameter in addition to fine dust. There are 11 known rings, all very faint; Neptune Neptune is the eighth and farthest known planet from the Sun in the Solar System. It is the fourth largest planet by diameter and the third largest by mass; 17 times the mass of Earth. The planet is named after the Roman god of the sea. Neptune's atmosphere is primarily composed of hydrogen and helium, with traces of methane that account for the planet's blue appearance. Neptune's blue colour is much more vivid than that of Uranus, which has a similar amount of methane, so an unknown component is presumed to cause Neptune's intense colour.

Neptune's temperature at its cloud tops is usually close to -218 °C, one of the coldest in the solar system, due to its long distance from the sun. However, Neptune's centre is about 7,000 °C (13,000 °F), hotter than the sun's surface. This is due to extremely hot gases and rock in the center. After the discovery of Uranus, it was noticed that its orbit was not as it should be in accordance with Newton's laws. It was therefore predicted that another more distant planet must be perturbing Uranus' orbit. Neptune was first observed by Galle and d'Arrest on 1846 Sept 23 from mathematical calculations. Pluto Poor Pluto is no longer considered a planet in our solar system. Pluto orbits beyond the orbit of Neptune. It is much smaller than any of the official planets and now classified as a "dwarf planet". Pluto (on the left) compared in size to the Earth In Roman mythology, Pluto (Greek: Hades) is the god of the underworld. Pluto was discovered in 1930 by accident.

Calculations which later turned out to be in error had predicted a planet beyond Neptune, based on the motions of Uranus and Neptune. Not knowing of the error, Clyde W. Tombaugh at Lowell Observatory in Arizona did a very careful sky survey which turned up Pluto. After the discovery of Pluto, it was quickly determined that Pluto was too small to account for the discrepancies in the orbits of the other planets. The search for Planet X continued but nothing was found. Pluto's orbit is highly eccentric. At times it is closer to the Sun than Neptune (as it was from January 1979 thru February 11 1999). Pluto rotates in the opposite direction from most of the other planets.

Pluto's composition is unknown, but its density (about 2 gm/cm3) indicates that it is probably a mixture of 70% rock and 30% water ice much like Triton The Solar System Pictures & Information on the Sun, Moon & Eight Planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune Planets Planets Mercury | Venus | Earth | Mars | Jupiter | Saturn | Uranus | Neptune |* Pluto Traditional Definition Etymology: Middle English planete, from Old French, from Late Latin planeta, modification of Greek planEt-, planEs, literally, wanderer, from planasthai to wander. any of the seven celestial bodies: Sun, Moon, Venus, Jupiter, Mars, Mercury, and Saturn that in ancient belief have motions of their own among the fixed stars. any of the large bodies that revolve around the Sun in the solar system. [see IAU resolutions below] a similar body associated with another star. EARTH -- usually used with "the".

a celestial body held to influence the fate of human beings a person or thing of great importance : LUMINARY - plan�et�like /-"lIk/ adjective * The IAU [ International Astronomical Union ] officially designates planets within our solar system. STATUS February 2, 2006 "The IAU notes the very rapid pace of discovery of bodies within the Solar system over the last decade and so our understanding of the Trans-Neptunian Region is therefore still evolving very rapidly. This is in serious contrast to the situation when Pluto was discovered. As a consequence, The IAU has established a Working Group to consider the definition of a minimum size for a Planet.

Until the report of this Working Group is received, all objects discovered at a distance from the Sun greater than 40 AU will continue to be regarded as part of the Trans-Neptunian population." UPDATE August 24, 2006 RESOLUTION 5A The IAU therefore resolves that planets and other bodies in our Solar System be defined into three distinct categories in the following way: (1) A planet1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. (2) A dwarf planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. (3) All other objects3 orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

1The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. 2An IAU process will be established to assign borderline objects into either dwarf planet and other categories. 3These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies. Relative sizes of the planets and stars by Dave Jarvis . Smallest Planets The Solar System: Venus | The Institute for Creation Research The Solar System: Venus Resources › Physical Sciences Resources › Astronomy For millennia, people have enjoyed the sight of the “evening star” shining brightly in the western sky shortly after sunset. Outshining all other stars, this remarkable beacon seems to brighten to unbelievable glory as twilight fades to night. It rises higher night after night and then stops and begins to sink lower each evening until it vanishes below the horizon. Sometime later, it reappears just before sunrise in the eastern sky as the bright “morning star.” What did the ancient astronomers think about this magnificent object and its peculiar celestial dance?

They called it “Venus,” after the Roman goddess of love and beauty.1 Physical Properties With modern technology, we have learned a great deal about Venus. It’s not a “star” at all, but a planet—a small rocky world that shines only by reflected sunlight.2 In fact, Venus is about the same size as Earth.3 So when we look at Venus, it’s fun to think that this is also how tiny Earth would appear if viewed from Venus. The composition of Venus is also similar to Earth, and its orbit is physically closest to Earth’s of all the planets. For these reasons Venus is sometimes referred to as “Earth’s sister” or “Earth’s twin.”4 But there are far more differences than similarities. An examination of the surface of Venus has proved quite challenging because Venus is permanently enshrouded in thick clouds of sulfuric acid and toxic sulfur dioxide, masking all surface features. The atmosphere is comprised mainly of carbon dioxide and is the thickest atmosphere of the four terrestrial planets. At the surface, Venus has a crushing air pressure that is 92 times greater than Earth’s! This thick atmosphere acts like a blanket, trapping solar energy and warming the planet to unbelievable temperatures.

And since Venus orbits 26 million miles closer to the sun than Earth does, Venus already endures nearly twice the solar energy. The greenhouse effect causes the surface temperature of Venus to approach 900°F—the hottest of any planet in our solar system. In 1990, the NASA spacecraft Magellan was inserted into orbit around Venus and began systematically mapping the surface using radar. Since radar is not blocked by clouds, Magellan was able to map the topography of Venus in unprecedented detail. The four-year-long mission revealed that Venus has many of the same geological features found on Earth, including mountains, valleys, canyons, volcanos, lava flows, craters, and plains. Venus also has two major “continents”—Ishtar Terra and Aphrodite Terra. But since there is no liquid water on Venus, these “continents” are recognized only by their high elevations. Venus also has geological features not found on Earth, such as arachnoids, novae, tesserae, coronae, and pancake domes. Arachnoids are regions where the terrain has been folded and broken into a gossamer-looking structure resembling a spider web.

Novae are “radially fractured centers” between 60 and 200 miles in diameter. Sixty-four novae have been discovered on Venus.5 Tesserae are complex ridged terrains found on plateaus. “Corona” is from the Latin meaning “crown.”6 They are oval-shape features thought to be produced by plumes of upwelling magma that cause the surface to bulge and then collapse in the center, forming a crown-like ring. Pancake domes are similar in most respects to shield volcanoes on Earth, such as Mauna Loa in Hawaii. However, pancake domes are flatter and broader than their terrestrial counterparts. Venus has no moons and virtually no magnetic field. Such similarity, yet with differences, is consistent with the nature of God. God is the source of creativity and has created a diversity of objects within the universe, and yet there are similarities since the entire universe was created and is upheld by the same God. Differences and similarities are seen in the biological world, the world of particle physics, and in the solar system as well. But in the secular view, how can we make sense of this?

Earth and Venus are nearly identical in size and bulk composition and have similar orbits. In the secular view, they have a similar history too. So why would Earth’s “sister” be so radically different from Earth? There are secular speculations for such things—but such diversity is expected in the Christian worldview. A Day on Venus Venus has the most circular orbit of any planet in the solar system. Its axial tilt is only three degrees, so there are no seasons on Venus. Since it orbits closer to the sun than Earth does, Venus orbits faster and completes a circuit every 7.4 months. But its day is much longer than Earth’s. Venus rotates once every eight months, so its day is actually longer than its year. This is the sidereal day—the rotation of Venus relative to the stars.7 What is even more intriguing is that Venus rotates backward. All eight planets orbit the sun counterclockwise, as viewed from the solar system’s North Pole. Most of the planets also rotate counterclockwise,8 but Venus is the exception.9 On Venus, the sun would rise in the west and set in the east—although it would be difficult to see the sun in such overcast skies.

Secularists do not have a good explanation for the backward rotation of Venus. In the secular scenario, the solar system is supposed to have formed from the collapse of a rotating nebula. The natural expectation of this would be that all planets would rotate in the same direction at about the same rate, and they would all have very little axial tilt. Venus is the worst offender to this concept, since it rotates exactly the opposite of what the evolutionary models require. But we expect such diversity in the biblical view. The backward rotation of Venus causes its solar day to be much shorter than its sidereal day—a unique phenomenon in the solar system. Recall that the solar day is the average time from one sunrise to the next as viewed from a planet’s surface (e.g., 24 hours for Earth). This is different (and normally slightly longer) from the sidereal day because planets orbit the sun and not the stars. Since Venus rotates in the opposite direction, its solar day is reduced to 3.8 months. Strangely, this is shorter than Mercury’s solar day, even though Venus physically rotates slower than Mercury. Phases and the Nature of the Solar System Venus is a great target for telescope beginners.

Its brightness makes it easy to find, and its size and proximity to Earth allow viewers to discern its shape through even a small, inexpensive telescope. Although the clouds on Venus prevent observations of any surface features, observers will immediately notice that Venus has phases; it is not uniformly illuminated, but appears bright on one side and dark on the other. Viewers sometime describe it as a tiny craterless “moon,” since the moon is the only other object that we readily recognize as going through phases. Just like the moon, Venus goes through new, crescent, quarter, gibbous, and full phases.10 And like the moon, these phases make it obvious to the eye that Venus is spherical, not a flat disk. But there are three differences in the phases of Venus compared to the moon. First, the moon takes roughly one month to go through its phases, whereas Venus takes over 19 months. Since Venus orbits the sun faster than Earth does, it physically overtakes and passes the Earth every 19 months. This is called the synodic period of Venus. Since the phase of Venus as seen from Earth depends on the relative positions of Earth, Venus, and the sun, phases correlate with the synodic period.

Second, whereas the moon remains approximately the same apparent size as it goes through its phases, Venus does not. Venus appears very small when in its gibbous phase (nearly full) and appears very large when in its crescent phase.11 This is because Venus orbits the sun, not the Earth. Hence, when Venus is nearly in-between the sun and Earth and we are viewing only a thin sliver of the illuminated side, Venus is nearly as close to Earth as it gets. Conversely, when Venus is on the far side of the sun, we see it nearly fully illuminated. Galileo was the first person to observe and document this effect. His telescopic observations of Venus led him to realize that planets orbit the sun—not the earth. This was in contrast to the prevailing scientific view of the day. The earth-centered (geocentric) solar system predicts that Venus will only appear as a crescent. The sun-centered (heliocentric) model can make sense of the phases of Venus and their correlation with its apparent size. Finally, the phases of Venus (and Mercury) are reversed relative to the moon.

In other words, when the moon is illuminated on the right side (toward the western horizon), it is in a waxing phase and will appear more illuminated on the following night. But when Venus is illuminated on the right side, it is in a waning phase and will appear less illuminated over the following weeks. Both Venus and the moon orbit in the same direction. So how can this be? The difference is because Venus orbits the sun, whereas the moon orbits Earth. So when the moon is in-between Earth and the sun, it is moving to the left (eastward). But when Venus is in between the sun and Earth, it is moving to the right (westward). From our perspective on Earth, Venus stands out as a pure white light, superior in splendor and luminance. Venus is mentioned in Scripture as the “morning star,” where its brilliance is used as a symbol for Christ ( Revelation 2:28 ; 22:16).12 None of the other nighttime stars can compete with Venus, so it is a fitting symbol of the beauty and glory of our Lord. References Venus is the second-brightest regular object in our night sky. Only the moon is brighter.

Venus is not a star in the modern sense of the word. However, the ancient term for star (aster in Greek, kowkab in Hebrew) includes both stars and planets. A planet is a “wandering star”—a star that moves relative to the majority of fixed stars. Venus is 95 percent as large as Earth in diameter. Though they do have the same Father ( James 1:17 ), they cannot be “twins” because Earth is three days older than Venus ( Genesis 1:1 , 14-19). Krassilnikov, A. S. and J. W. Head. 2003. Novae on Venus: Geology, Classification, and Evolution. Journal of Geophysical Research: Planets (1991-2012). 108 (E9): 1-48. Coronae are found only on Venus and Uranus’ moon Miranda. See the Mercury article for a discussion of sidereal versus solar days: Lisle, J. 2013. The Solar System: Mercury . Acts & Facts. 42 (8) 10-12.

This is relative to the North Pole of the solar system. Alternatively, we could define the North Pole of a planet as the pole under which the planet rotates counterclockwise. By this definition, all planets rotate in the same direction and Venus is merely “upside down.” There is no physical difference between Venus being tilted 3° and rotating backward (clockwise), as opposed to Venus being tilted 177° and rotating forward (counterclockwise). Both conventions are used in astronomy. Since the planet Uranus is tilted 97°, it too could be considered a backward-rotator with a tilt of 83°. However, since this is nearly a right angle, it makes little difference. The outer planets can only be seen in gibbous and full phases. This is because quarter and crescent phases require the planet to be closer to the sun than the observer is. This can never occur for an outer planet as seen from Earth. This effect is also visible in the planet Mercury for the same reason. However, the effect is much less noticeable on Mercury since its distance from Earth does not vary as much.

Also, Mercury is much smaller than Venus and closer in angle to the sun, making observations of its apparent diameter far more difficult. In some English translations, Lucifer is called the morning star in Isaiah 14:12 . It may bother some people that the same symbol is used for Christ, but Isaiah 14:12 may simply indicate that Lucifer was one of the most glorious angels before he rebelled. Satan attempts to parrot Christ in some ways—Christ is the Lion of Judah ( Revelation 5:5 ), and Satan prowls about as a roaring lion ( 1 Peter 5:8 ). We note that the word “star” does not appear in the Hebrew text of Isaiah 14:12 . “Son of the morning” or “son of the dawn” appears to be a more literal translation from the original text. * Dr. Lisle is Director of Physical Sciences at the Institute for Creation Research and received his Ph.D. in Astrophysics from the University of Colorado. Cite this article: Lisle, J. 2013. The Solar System: Venus. Acts & Facts. 42 (9): 10-12.

StarTeach Astronomy Education you are here > Our Solar System Our Solar System Our solar system consists of various bodies of different sizes which orbit the sun. The planets are the most important of these orbiting objects, and are arrayed in this order (first is closest to the sun): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. The SUN, which is actually just an ordinary star, lies at the center of our solar system. What makes the sun so special to us is simply the fact that it is so close to the Earth, only 93 million (92,960,000) miles away. This distance may seem huge, but when you realize that the closest star to us besides the sun is 25.3 trillion (25,300,000,000,000) miles away, you can see how giant space really is. Besides the obvious effects the sun has on our lives, solar activity also contributes to weather patterns on Earth. For instance, between the years 1640 and 1710, there were almost no sunspots on the surface of the sun.

This coincided with a period of very cold weather on Earth known as the "Little Ice Age." Solar eclipses are particularly fascinating to watch. During a solar eclipse, the moon, the Earth, and the sun line up so that the moon lies between the sun and Earth. From our point of view on Earth, the sun is blocked completely by the moon for a few minutes. Another beautiful sight visible from Earth are the aurorae, or northern lights. These brightly colored bands usually appear in the sky in locations near the north and south poles. The bright colors occur when high-energy particles from the sun are swept into our atmosphere and make the atoms there glow. The sun gets its energy from nuclear fusion, which is a nuclear process where four hydrogen atoms are converted into one helium atom. Since the total atomic mass of four hydrogen atoms is 0.7 percent more than the atomic mass of the helium atom, there is a little bit of extra mass left over at the end of this conversion process. In his famous E = mc^2 equation, Einstein proved that mass and energy are transferable. The extra mass created in the nuclear process described above is converted into energy.

This nuclear fusion occurs in the central core of the sun, where the temperature is about 15 million degrees Fahrenheit and the pressure is 250 billion times the pressure of the Earth's atmosphere. MERCURY is the closest planet to the sun, and so it is also the fastest moving, orbiting the sun at 107,136 mph. This fast speed led the Romans to name it after Mercury, who was the speedy messenger of the Roman gods. Since Mercury is so close to the sun, it is difficult to see from Earth. It is visible only right after sunset or right before sunrise. Mercury has no moons. Nearly 4,000 of the best photographs of Mercury were taken by the Mariner 10 space mission in 1974. Those pictures show that Mercury is a small rock that resembles the moon. However, it has long cliffs and shallow craters instead of the deep craters found on the moon. At the center of the planet is a large iron core. One year on Mercury is only 88 Earth days long, while one day on Mercury is equal to 59 days on Earth!

This means that since Mercury has no atmosphere, and the sun shines continuously on the surface for 59 Earth days in a row, the daytime temperatures on Mercury can reach as high as 800 degrees Fahrenheit, under which conditions even metals such as lead would be melted! When it is nighttime on the surface, the temperature is -250 degrees Fahrenheit! VENUS is the closest planet to Earth, and is the third brightest object in our sky after the sun and moon. Although it is similar to our planet in size, mass, and density, its surface environment is quite different. The atmosphere is made up of 96% carbon dioxide and small amounts of acids. One feature of the atmosphere is the greenhouse effect, in which heat (infrared radiation) is trapped near the surface because it gets reflected back down by the clouds. Venus is therefore very hot, approximately 900 degrees Fahrenheit. The surface has been studied by the Pioneer Venus 1 and Magellan spacecrafts, which used radar to peer through the clouds and make maps. They found that most of the surface is covered by craters and hills. There are also indications that Venus had a lot of volcanic activity in the past.

The atmospheric pressure at the surface is 90 times Earth's pressure! Venus does not have any moons. Our planet, EARTH, is very unique. The environment is rich enough to support life, and many life forms thrive. Unlike any of the other planets, Earth is covered by vast quantities of water. In fact, more than 70% of the surface is under the ocean. Temperatures on Earth are very moderate compared to the other planets. Humans can live relatively comfortably at almost any location on the surface. Our only moon is a quarter the size of Earth. It rotates on its axis at exactly the same rate that it orbits the Earth, and so we always see the same side of the moon. There is no air or water on the surface of the moon, and there is also no geological activity. The moon is the only other place in the universe that people have traveled to. MARS is a rocky red planet about half the size of Earth. It orbits the sun every 1.88 Earth years, and a day on Mars lasts about as long as one on Earth does. The planet's axis of rotation is also similar to the Earth's, which means that Mars experiences seasons as well.

One unique feature is the polar ice caps, which are a combination of water ice and frozen carbon dioxide. The ice caps melt and rebuild according to the seasons, just as they do on Earth. The surface features on Mars are huge: the Valles Marinaris is a valley longer than the whole United States, and Olympus Mons is a volcano larger than Arizona and three times higher than the Hawaiian Island volcanoes. Three spacecraft have landed on Mars, and they have sent back pictures of a relatively flat surface covered with red rocks. Mars has two moons, Phobos and Deimos, which are probably asteroids captured by Mars' orbit long ago. The ASTEROID BELT lies between Mars and Jupiter. The first asteroids, or minor planets, were discovered in the very early 1800s. Eventually over 4,000 of them were found. Astronomers had calculated that another planet should lie between Mars and Jupiter, and the asteroid belt seemed to solve this problem. Asteroids are composed of raw material from the creation of our solar system. For some reason, this material did not come together to form one planet. Asteroids are the source of most meteors that have hit the Earth.

JUPITER is named after the king of the Roman gods. It is the largest planet, yet it spins very quickly on its axis- one day is about 10 Earth hours. The atmosphere is composed mainly of hydrogen and helium, although it is the small amounts of gases like ammonia and methane which make the bands on Jupiter look so colorful. It is very turbulent in the atmosphere, with huge storms frequently lasting years. The Great Red Spot is a storm which has been in existence for 300 years, and covers an area larger than Earth! Jupiter is a gas giant with a very faint ring system. The atmosphere is so thick that it is impossible to see the rocky core that is probably at the center of this huge body. There are 16 moons orbiting Jupiter. The four brightest ones- Io, Europa, Ganymede, and Callisto- are visible from Earth through a small telescope. They were first discovered in 1610 by Galileo, who was using a telescope that he built. These four moons are therefore called the Galilean satellites. SATURN is one of the most beautiful and unusual sights in the sky. It is a giant gas planet about ten times the size of Earth.

Its density is so low that it would float in a (very) big dish of water. Like Jupiter, Saturn has an atmosphere of hydrogen and helium and is often very stormy. The most unique feature of Saturn is its bright and colorful ring system, which is easily visible from Earth with a small telescope. The rings are composed of billions of small rock and ice particles which reflect the sunlight and are held together by gravity and a few of Saturn's moons. The dark separation between the two main rings is called the Cassini division. Saturn has 18 moons. The largest is Titan, which is actually larger than Mercury and Pluto. URANUS was found in 1781 by the astronomer William Herschel. Like Saturn and Jupiter, Uranus is a gas giant with a helium and hydrogen atmosphere. Uranus has a faint ring system that cannot be seen from Earth except with a very large telescope. The rings were discovered only 23 years ago, when Uranus passed in front of a star, which appeared to blink as it passed the rings. Uranus has at least 15 moons, some of which are probably captured asteroids.

NEPTUNE was discovered in 1846, after astronomers calculated where its orbit should be in order to cause strange motions in Uranus' orbit. Neptune's atmosphere is also composed of hydrogen and helium, and it has a very faint ring system that cannot be seen from Earth. For 20 years out of every 248 years (one orbit of Pluto), Neptune is actually the farthest planet from the sun. This was the case from 1979 until 1999. Pluto is now once again the last planet in the solar system. Neptune has eight moons. PLUTO is usually (see 'Neptune' above) the farthest planet from the sun. It was found in 1930. Pluto is quite different from the other gas giants in the outer reaches of the solar system. In fact, it is simply a rock composed of frozen methane. There is an on-going debate about whether Pluto should be considered a planet, since it more closely resembles an asteroid or moon. Some astronomers believe that it is an escaped moon of Neptune, and others believe that it could be the remains of a large comet.

Pluto is extremely cold, with a surface temperature of only about -360 degrees Fahrenheit. Pluto's only moon, Charon, was discovered in 1978. REFERENCES FOR THIS PAGE:

Question: Venus and which other planet in our solar system has no moon?
Answer: Mercury