The 'sky' of a world refers to the view of the heavens from its surface. This view varies from world to world for many reasons. The most important factor in the appearance of a world's sky is its atmosphere, or the lack thereof. Depending on the atmosphere's density and chemical composition, a world's sky may be any number of colors. Clouds may or may not be present and they may also be noticeably colored. Another factor is the astronomical objects that may appear in a world's sky, such as the Sun, stars, moons, planets, and rings. For other uses, see Sky (disambiguation). ... Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. ... For other uses, see Atmosphere (disambiguation). ... The chemical composition of a substance refers to the elements of which the substance is composed. ... Color is an important part of the visual arts. ... hello--~~~~fake <gallery> poos[[kill]] </gallery> For other uses, see Cloud (disambiguation). ... Sol redirects here. ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made. ... The eight planets and three dwarf planets of the Solar System. ... A planetary ring is a ring of dust and other small particles orbiting around a planet in a flat disc-shaped region. ...

This article explains what an observer on various worlds in the solar system and beyond would see from their surfaces. Much of this material is duplicated from the entries on individual planets, moons, comets, asteroids, and other bodies but is assembled here for those interested in the general subject of extraterrestrial skies. This article is about the Solar System. ... The eight planets and three dwarf planets of the Solar System. ... This article is about Earths moon. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... 253 Mathilde, a C-type asteroid. ...

Mercury

Since Mercury has no atmosphere, its sky is always black. Mercury has a southern polar star, α Pictoris, a magnitude 3.2 star. It is fainter than Earth's Polaris (α Ursae Minoris). This article is about the planet. ... Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. ... For other uses of the words Pole star and Polestar see Polestar (disambiguation). ... Alpha Pictoris (α Pic / α Pictoris) is a star in the constellation Pictor. ... Polaris (α UMi / α Ursae Minoris / Alpha Ursae Minoris), more commonly known as The North Star or simply North Star, is the brightest star in the constellation Ursa Minor. ...

The Sun from Mercury

The visible diameter of the Sun on Mercury is 2.5 times larger than it appears from Earth on average, and more than 6 times brighter. However, because of its eccentric orbit the Sun's apparent size in the sky would vary from 2.2 times larger than on Earth (and 4.8 times brighter) at aphelion, to 3.2 times larger (and 10.2 times brighter) at perihelion. Sol redirects here. ... This article is about Earth as a planet. ... A diagram of Keplerian orbital elements. ... A diagram of Keplerian orbital elements. ...

Mercury has a 3:2 spin-orbit resonance. This means that although a sidereal day (the period of rotation) lasts ~58.7 Earth days, a solar day (the length between two meridian transits of the Sun) lasts ~176 Earth days. On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ... Solar time is based on the idea that, when the sun reaches its highest point in the sky, it is noon. ... This article is about the astronomical concept. ... 2003 Transit of Mercury The term transit or astronomical transit has two meanings in astronomy: A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, as seen by an observer at some particular vantage point. ...

Mercury's spin-orbit resonance generates an unusual effect in which the Sun appears to briefly reverse its usual east to west motion once every Mercurian year. The effect is visible wherever one happens to be on Mercury, but there are certain points on Mercury's surface where an observer would be able to see the Sun rise about halfway, reverse and set, and then rise again, all within the same Mercurian day. This is because approximately four days prior to perihelion, the angular speed of Mercury's orbit exactly equals its rotational velocity, so that the Sun's apparent motion ceases; at perihelion, Mercury's orbital angular velocity then exceeds the rotational velocity; thus, the Sun appears to be retrograde. Four days after perihelion, the Sun's normal apparent motion resumes. Because of its spin-orbit resonance, Mercury presents one of two spots of its surface to the Sun on alternate perihelia; one of these subsolar points is Caloris Planitia ("hot basin"), appropriately named because an observer near its centre would see the Sun loop around the zenith once per Mercurian day, and hence experience a very hot day indeed. If one were to look at the sun from Mercury, one's eyes would surely be instantly incinerated. A typical sunrise, in New Zealand A sunrise through clouds over Oakland, California. ... A composite image showing the terminator dividing night from day, running across Europe and Africa. ... In mathematics, two mathematical objects are considered equal if they are precisely the same in every way. ... Rotational speed (sometimes called speed of revolution) indicates, for example, how fast a motor is running. ... Apparent motion is used in at least two senses. ... This article is about retrograde motion. ... The Caloris Basin, also called Caloris Planitia, is an impact crater, on Mercury, which is ~1350km in diameter. ...

Other planets seen from Mercury

After the Sun, the second brightest object in the Mercurian sky is Venus, which is much brighter than for terrestrial observers. The reason for this is that when Venus is closest to Earth, it is between the Earth and the Sun, so we see only its night side. Indeed, even when Venus is brightest in the Earth's sky, we are actually seeing only a narrow crescent. For a Mercurian observer, on the other hand, Venus is closest when it is in opposition to the Sun and is showing its full disk. The apparent magnitude of Venus is approximately −6.6. ^{[citation needed]} (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... Opposition is a term used in positional astronomy and astrology. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ...

The Earth and the Moon are also very prominent, their apparent magnitudes being about −5.2 and −1.2 respectively. ^{[citation needed]} The maximum apparent distance between the Earth and the Moon is about 15′. All other planets are visible just as they are on Earth, but somewhat less bright at opposition. This article is about Earth as a planet. ... This article is about Earths moon. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ...

The zodiacal light is probably more prominent than it is from Earth. The zodiacal light in the eastern sky before the beginning of morning twilight. ...

Venus

The atmosphere of Venus is so thick that the Sun is not distinguishable in the daytime sky, and the stars are invisible at night. Color images taken by the Soviet Venera probes suggest that the sky on Venus is yellow-orange. If the Sun could be seen from Venus' surface, it would appear to rise and set in a 243 day cycle (Venus' synodic rotation period), and a Venus year would thus last 0.926 Venus "days". (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... Color image taken from the surface of Venus by the Soviet Venera 13 lander The Venera series of probes was developed by the USSR for the gathering of data from Venus. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ...

An observer aloft in Venus' cloud tops, on the other hand, would whip around the planet in about four days and be treated to a sky in which Earth and the Moon shine brightly (about magnitudes −6.7 and −2.7, respectively) ^{[citation needed]} because their maximum approach occurs at opposition. Mercury would also be easier to spot, both because it is closer (and hence brighter, about magnitude -7), ^{[citation needed]} and because its maximum elongation from the Sun is considerably larger (40.5°) than when observed from Earth (28.3°). This diagram shows the elongations (or angle) of the Earths position from the Sun. ...

The Moon

The Moon has no atmosphere, so its sky is always black. However, the Sun is so bright that it is impossible to see stars during the daytime, unless the observer is well shielded from sunlight (direct or reflected from the ground). The Moon has a southern polar star, δ Doradus, a magnitude 4.34 star. It is better aligned than Earth's Polaris (α Ursae Minoris), but much fainter. This article is about Earths moon. ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... δ Doradus is a faint star in the Dorado constellation that has the distinction of being the Moons south pole star. ... Polaris (α UMi / α Ursae Minoris / Alpha Ursae Minoris), more commonly known as The North Star or simply North Star, is the brightest star in the constellation Ursa Minor. ...

The Sun from the Moon

The Sun looks the same from the Moon as it does from Earth, except that it is somewhat brighter (and colored pure white) due to the lack of atmospheric scattering and absorption, although the sun's appearance from the moon is identical to its appearance from earth orbit. Sol redirects here. ...

The Earth from the Moon

Apollo 17 commander Eugene Cernan on the Moon, with Earth visible in the sky

The most interesting feature of the Moon's sky is, of course, the Earth, spinning against the black backdrop of space. Its visible diameter (1.9°) is four times the diameter of the Moon as seen from the Earth, although because the Moon's orbit is eccentric, the Earth's apparent size in the sky varies slightly, by about 5% either way (between 1.8° and 2.0°). The Earth shows phases, just like the Moon for the terrestrial observer, but they are opposite: when the terrestrial observer sees the full Moon, the lunar observer sees a "new Earth", and vice versa. The Earth's albedo is three times as high as that of the Moon. The full Earth glows over 50 times brighter than the full Moon at zenith does for the terrestrial observer. Download high resolution version (900x938, 106 KB)Eugene Cernan on the Moon, with Earth in the sky http://www. ... Download high resolution version (900x938, 106 KB)Eugene Cernan on the Moon, with Earth in the sky http://www. ... This article is about Earth as a planet. ... Planetary phase is the term used to describe the appearance of the illuminated section of a planet. ... Albedo is the ratio of reflected to incident electromagnetic radiation. ...

As a result of the Moon's synchronous rotation, one side of the Moon (the "near side") is permanently turned towards Earth, and the other side, the "far side", mostly cannot be seen from Earth. This means, conversely, that the Earth can only be seen from the near side of the Moon, and would always be invisible from the far side. Due to synchronous rotation of their moon, the inhabitants of the central body will never be able to see its green side. ... Far side of the Moon. ...

If the Moon's rotation were purely synchronous, the Earth would not have any noticeable movement in the Moon's sky. However, due to the Moon's libration, the Earth does perform a slow and complex wobbling movement. Once a month, as seen from the Moon, the Earth traces out an approximate oval of diameter 18°. The exact shape and orientation of this oval depend on one's location on the Moon. As a result, near the boundary of the near and far sides of the Moon, the Earth is sometimes below the horizon, and sometimes above it. Not to be confused with Liberation. ... Horizon. ...

Eclipses from the Moon

The Earth and the Sun sometimes meet in the lunar sky, causing an eclipse. On the Earth, one then sees a lunar eclipse, in which the Moon passes through the Earth's shadow, but on the Moon, one would see the Sun go behind the Earth — causing a solar eclipse. As the apparent diameter of the Earth would be four times larger than that of the Sun, the Sun would hide behind the Earth for hours. The Earth's atmosphere would be visible as a reddish ring. An attempt was made to use the Apollo 15 Lunar Rover TV camera to view such an eclipse, but the camera or its power source failed after the astronauts left for Earth.^[1] This article is about astronomical eclipses. ... Time lapse movie of the 3 March 2007 lunar eclipse A lunar eclipse occurs whenever the Moon passes through some portion of the Earths shadow. ... Photo taken during the 1999 eclipse. ... “Air” redirects here. ...

Terrestrial solar eclipses, on the other hand, would not be spectacular for lunar observers, because the Moon's shadow nearly tapers out at the Earth's surface. Lunar observers with telescopes might simply see a small darkened spot travel across the full Earth's disk. Photo taken during the 1999 eclipse. ...

In summary, whenever an eclipse of some sort is occurring on the Earth, an eclipse of another sort is occurring on the Moon. Eclipses occur for both Earth and Lunar observers whenever the two bodies and the Sun align in a straight line.

Mars

Mars has only a thin atmosphere; however, it is extremely dusty and there is much light that is scattered about. The sky is thus rather bright during the daytime and stars are not visible. Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ...

The color of the Martian sky

Mars' sky turned violet by water ice clouds

Mars sky at noon as imaged by Mars Pathfinder

Mars sky at sunset, as imaged by Mars Pathfinder

Close-up of Mars sky at sunset, showing more color variation, as imaged by Mars Pathfinder

Generating accurate true-color images from Mars' surface is surprisingly complicated.^[2] To give but one aspect to consider, there is the Purkinje effect: the human eye's response to color depends on the level of ambient light — red objects appear to darken faster than blue objects as the level of illumination goes down. There is much variation in the color of the sky as reproduced in published images, since many of those images are using filters to maximize their science value and are not trying to show true color. For many years, the sky on Mars was thought to be more pinkish than it is now believed to be. Courtesy: NASA/JPL The usually pinkish-red color of Marss sky turns a violet color on occasion, due to the presence of water ice clouds with very small ice particles. ... Courtesy: NASA/JPL The usually pinkish-red color of Marss sky turns a violet color on occasion, due to the presence of water ice clouds with very small ice particles. ... Download high resolution version (982x236, 13 KB)Courtesy: NASA/JPL-Caltech The Martian sky at noon is yellow-brown, which contrasts with its pinkish-red color at sunset. ... Download high resolution version (982x236, 13 KB)Courtesy: NASA/JPL-Caltech The Martian sky at noon is yellow-brown, which contrasts with its pinkish-red color at sunset. ... The Mars Pathfinder was launched on December 4, 1996 by NASA aboard a Delta II just a month after the Mars Global Surveyor was launched. ... Download high resolution version (2853x699, 47 KB)Courtesy: NASA/JPL-Caltech Sunset on Mars, as imaged by Mars Pathfinder. ... Download high resolution version (2853x699, 47 KB)Courtesy: NASA/JPL-Caltech Sunset on Mars, as imaged by Mars Pathfinder. ... The Mars Pathfinder was launched on December 4, 1996 by NASA aboard a Delta II just a month after the Mars Global Surveyor was launched. ... Courtesy: NASA/JPL-Caltech Sunset on Mars as imaged by Mars Pathfinder This is a close-up of the sunset on Sol 24 as seen by the Imager for Mars Pathfinder. ... Courtesy: NASA/JPL-Caltech Sunset on Mars as imaged by Mars Pathfinder This is a close-up of the sunset on Sol 24 as seen by the Imager for Mars Pathfinder. ... The Mars Pathfinder was launched on December 4, 1996 by NASA aboard a Delta II just a month after the Mars Global Surveyor was launched. ... The Purkinje effect (sometimes called the Purkinje shift, or dark adaptation) is the tendency for the peak sensitivity of the human eye to shift toward the blue end of the color spectrum at low illumination levels. ...

It is now known that during the Martian day, the sky is a yellow-brown, butterscotch color. Around sunset and sunrise, sky is pinkish-red in colour, but in the vicinity of the setting Sun it is blue. This is the exact polar opposite of the situation on Earth. At times, the sky takes on a purplish color, due to the scattering of light by very small water ice particles in clouds.^[3] Twilight lasts a long time after the Sun has set and before it rises, because of the dust high in Mars' atmosphere.

On Mars, Rayleigh scattering is usually a very weak effect; it is believed that the color of the sky is caused by the presence of 1% by volume of magnetite in the airborne dust particles. Rayleigh scattering causing the blue hue of the sky and the reddening at sunset Rayleigh scattering (named after Lord Rayleigh) is the scattering of light, or other electromagnetic radiation, by particles much smaller than the wavelength of the light. ... // Headline text Magnetite is a ferrimagnetic mineral form of iron(II,III) oxide, with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. ...

The Sun from Mars

The Sun as seen from Mars is seen 1.6 times smaller (0.35°) than on Earth, and sends 2.5 times less light. A detailed analysis of the Sun's movements as seen from Mars can be found in the article on timekeeping on Mars. Sol redirects here. ... Various schemes have been used or proposed to keep track of time and date on the planet Mars independently of Earth time and calendars. ...

Mars' moons as seen from Mars

Phobos transits the Sun, as seen by Mars Rover Opportunity on March 10, 2004

Mars has two small moons: Phobos and Deimos. From the Martian surface, Phobos has one-third to half the angular diameter of the Sun, but Deimos is barely more than a dot (only 2' angular diameter). The apparent motion of Phobos is in reverse, due to its fast orbital motion: it rises in the west and sets in the east. Phobos orbits so close (in a low-inclination equatorial orbit) that it cannot be seen north of 70.4°N or south of 70.4°S latitude; high-latitude observers would also notice a decrease in Phobos' apparent size, the additional distance being non-negligible. Phobos' apparent size varies by up to 45% as it passes overhead, due to its proximity to Mars' surface. For an equatorial observer, for example, Phobos is about 0.14° upon rising and swells to 0.20° by the time it reaches the zenith. It crosses the sky swiftly, in about 4.24 hours, every 11.11 hours. Credit: NASA/JPL/Cornell [1] A transit of Phobos from Mars: Phobos is in transit across the Sun, as seen from Mars by Mars Rover Opportunity on March 10, 2004 at 07:36:38 UTC Earth time. ... Credit: NASA/JPL/Cornell [1] A transit of Phobos from Mars: Phobos is in transit across the Sun, as seen from Mars by Mars Rover Opportunity on March 10, 2004 at 07:36:38 UTC Earth time. ... 2003 Transit of Mercury The term transit or astronomical transit has two meanings in astronomy: A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, as seen by an observer at some particular vantage point. ... Sol redirects here. ... MER-B (Opportunity) is the second of the two rovers of NASAs Mars Exploration Rover Mission. ... March 10 is the 69th day of the year (70th in leap years) in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Phobos (IPA: or [ˈfoÊŠ.bÉ™s]) (systematic designation: ) is the larger and closer of Mars two moons (the other being Deimos). ... Deimos (IPA or ; Greek Δείμος: Dread), is the smaller and outermost of Mars’ two moons, named after Deimos from Greek Mythology. ... The angular diameter of an object as seen from a given position is the diameter measured as an angle. ...

Deimos rises in the east and sets in the west, like a "normal" moon, although its appearance is star-like (angular diameter between 1.8' and 2.1'). Its brightness would vary between that of Venus and of the star Vega (as seen from Earth). Being relatively close to Mars, Deimos cannot be seen from Martian latitudes greater than 82.7°. Finally, Deimos' orbital period of about 30.3 hours exceeds the Martian rotation period (of about 24.6 hours) by such a small amount that it rises every 5.5 days and takes 2.5 days between rising and setting for an equatorial observer. Thus Phobos crosses the Martian skies nearly 12 times whilst Deimos crosses them just once. For other uses, see Vega (disambiguation). ...

Phobos and Deimos can both eclipse the Sun as seen from Mars, although neither can completely cover its disk and so the event is in fact a transit, rather than an eclipse. For a detailed description of such events see the articles Transit of Phobos from Mars and Transit of Deimos from Mars. This article is about astronomical eclipses. ... 2003 Transit of Mercury The term transit or astronomical transit has two meanings in astronomy: A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, as seen by an observer at some particular vantage point. ... Phobos transits the Sun, as seen by Mars Rover Opportunity on March 10, 2004 A transit of Phobos across the Sun as seen from Mars takes place when Phobos passes directly between the Sun and a point on the surface of Mars, obscuring a large part of the Suns... Deimos transits the Sun, as seen by Mars Rover Opportunity on March 4, 2004 A transit of Deimos across the Sun as seen from Mars takes place when Deimos passes directly between the Sun and a point on the surface of Mars, obscuring a small part of the Suns...

Earth from Mars

The Earth is visible from Mars as a double star; the Moon would be visible alongside it as a fainter companion. The maximum visible distance between the Earth and the Moon would be about 25′. At maximum elongation (47.4°), Earth and Moon would shine at apparent magnitudes −3.2 and +0.8, respectively. ^{[citation needed]} At inferior conjunction of the Earth and the Sun —for the terrestrial observer it will be opposition of Mars and the Sun. This article is about Earth as a planet. ... Conjunction is a term used in positional astronomy and astrology. ... Opposition is a term used in positional astronomy and astrology. ...

The skies of Mars' moons

From Phobos, Mars appears 6,400 times larger and 2,500 times brighter than the full Moon as seen from Earth, taking up a quarter of the width of a celestial hemisphere.

From Deimos, Mars appears 1,000 times larger and 400 times brighter than the full Moon as seen from Earth, taking up an eleventh of the width of a celestial hemisphere.

Asteroids

The asteroid belt is sparsely populated and most asteroids are very small, so that an observer situated on one asteroid would be unlikely to be able to see another without the aid of a telescope. Occasional "close approaches" do occur, but these are spread out over eons. One movie to accurately show this is 2001: A Space Odyssey.

Some asteroids that cross the orbits of planets may occasionally get close enough to a planet or asteroid so that an observer from that asteroid can make out the disc of the nearby object without the aid of binoculars or a telescope. For example, in September 2004, 4179 Toutatis came about four times the distance from the Earth than the Moon does. At its closest point in its encounter, the Earth would have appeared about the same size that the Moon appears from Earth. The Moon would also be easily visible as a small shape in Toutatis's sky at that time. The asteroid 4179 Toutatis (too-ta-tis) is an Apollo, an Alinda and a Mars-crosser asteroid with a chaotic orbit produced by a 3:1 resonance with the planet Jupiter. ... This article is about Earth as a planet. ... This article is about Earths moon. ...

Asteroids with unusual orbits also offer a lot to the imagination. For instance, the asteroid (or more likely, extinct comet) 3200 Phaethon has one of the most eccentric orbits; its distance from the Sun varies between 0.14 and 2.4 AUs. At perhelion, the Sun would loom over 7 times larger than it does in our sky, and blast the surface with over 50 times as much energy; at aphelion, the Sun would shrink to less than half its apparent diameter on Earth, and give little more than a sixth as much illumination. Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... 3200 Phaethon (sometimes incorrectly spelled Phaeton) is an Apollo and Mercury-, Venus- and Mars_crosser asteroid with unusual properties, and may be an extinct comet. ... Look up Au, au in Wiktionary, the free dictionary. ...

87 Sylvia and its moons Romulus and Remus

From the surface of the asteroid 87 Sylvia, its two moons Romulus and Remus would appear roughly the same size. Romulus, the farther one, would be about 0.89° across, slightly bigger than the closer but smaller Remus, which would be about 0.78° across. Because Sylvia is far from spherical, these values can vary by about a little more than 10%, depending on where the observer is on Sylvia's surface. Since the two asteroidal moons appear to orbit (as best we can tell) in the same plane, they would occult each other once every 2.2 days. When the season is right, twice during Sylvia's 6.52 year orbital period, they would eclipse the Sun, which, at 0.15° across, is much smaller than when seen from Earth (0.53°). From Remus, the inner moon, Sylvia is huge, roughly 30°×18° across, while its view of Romulus varies between 1.59 and 0.50° across. From Romulus, Sylvia measures 16°×10° across, while Remus varies between 0.62° and 0.19°. 87 Sylvia (sil-vee-a) is one of the largest main belt asteroids. ... Sylvia and Romulus Romulus is the outer and larger moon of the main belt asteroid 87 Sylvia, not to be confused with the directly Sun-orbiting asteroid 10386 Romulus. ... Remus is the inner and smaller moon of the main belt asteroid 87 Sylvia. ...

Jupiter

Although no images from within Jupiter's atmosphere have ever been taken, artistic representations typically assume that the planet's sky is blue, at least in the upper reaches of the atmosphere. The planet's narrow rings might be faintly visible from latitudes above the equator. Further down into the atmosphere, the Sun would be obscured by clouds and haze of various colors, most commonly blue, brown, and red. While theories abound on the cause of the colors, there is currently no clear answer. Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... A planetary ring is a ring of dust and other small particles orbiting around a planet in a flat disc-shaped region. ...

From Jupiter, the Sun appears to cover only 5 arc minutes, less than a quarter of its size as seen from Earth.

Jupiter's moons as seen from Jupiter

Simulated view of Io, Europa, and the rings of Jupiter seen from their parent planet

Aside from the Sun, the most prominent objects in Jupiter's sky are the four Galilean moons. Io, the nearest to the planet, would be slightly larger than the full Moon in Earth's sky, though less bright. The considerably higher albedo of Europa would not overcome its greater distance from Jupiter, so it would not outshine Io. In fact, the low solar constant at Jupiter's distance (3.7% Earth's) ensures that none of the Galilean satellites would be as bright as the full Moon is on Earth; from Io to Callisto their apparent magnitudes would be: -11.2, -9.7, -9.4, and -7.0 ^{[citation needed]}. Image File history File links Download high resolution version (1024x692, 21 KB)Simulated view of Io (below) and Europa as seen from a position high in Jupiters atmosphere. ... Image File history File links Download high resolution version (1024x692, 21 KB)Simulated view of Io (below) and Europa as seen from a position high in Jupiters atmosphere. ... Jupiters 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). ... Atmosphere Surface pressure: trace Composition: 90% sulfur dioxide Io (eye-oe, IPA: , Greek Ῑώ) is the innermost of the four Galilean moons of Jupiter and, with a diameter of 3,642 kilometers, is the fourth largest moon in the Solar System. ... Apparent magnitude: 5. ... Solar irradiance spectrum at top of atmosphere. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ...

Ganymede, the largest moon and third from Jupiter, is almost as bright as Io and Europa, but appears only half the size of Io. Callisto, still further out, is only a quarter the size of the full Moon. All four Galilean moons also stand out because of the swiftness of their motion, compared to our Moon. They are all also large enough to fully eclipse the Sun. This article or section does not adequately cite its references or sources. ... There is also an asteroid named 204 Kallisto. ... This article is about astronomical eclipses. ...

Jupiter's small inner moons appear only as starlike points, and most of the outer moons would be invisible to the naked eye.

The skies of Jupiter's moons

None of Jupiter's moons have more than traces of atmosphere, so their skies are black or very nearly so. For an observer on one of the moons, the most prominent feature of the sky would be, of course, Jupiter. For an observer on Io, the closest large moon to the planet, Jupiter's apparent diameter would be about 20° (38 times the visible diameter of our Moon, covering 1% of Io's sky). An observer on Metis, the innermost moon, would see Jupiter's apparent diameter bloated to a stupefying 68° (130 times the visible diameter of our Moon, covering 18% of Metis' sky); no other known moon of the solar system enjoys a more awe-inspiring spectacle. A "full Jupiter" over Metis shines with about 4% of the Sun's brightness (our full Moon is 400 thousand times dimmer than the Sun). Atmosphere Surface pressure: trace Composition: 90% sulfur dioxide Io (eye-oe, IPA: , Greek Ῑώ) is the innermost of the four Galilean moons of Jupiter and, with a diameter of 3,642 kilometers, is the fourth largest moon in the Solar System. ... Atmospheric pressure 0 kPa Metis (mee-tÉ™s, IPA: , Greek Μήτις), or Jupiter XVI, is the innermost member of the Jupiters small inner moons and thus Jupiters innermost moon. ...

Since the inner moons of Jupiter are in synchronous rotation around Jupiter, the planet always appears in nearly the same spot in their skies (Jupiter would wiggle a bit because of the non-zero eccentricities). Observers on the sides of the Galilean satellites facing away from the planet would never see Jupiter, for instance. Due to synchronous rotation of their moon, the inhabitants of the central body will never be able to see its green side. ... Jupiters 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). ...

From the moons of Jupiter, solar eclipses caused by the Galilean satellites would be spectacular, as an observer would see the circular shadow of the eclipsing moon travel across Jupiter's face. Photo taken during the 1999 eclipse. ...

Saturn

View of Saturn's rings seen from its equator

View of Saturn's rings seen from a latitude above its equator

The sky in the upper reaches of Saturn's atmosphere is probably blue, but the predominant color of its cloud decks suggests that it may be yellowish further down. The rings of Saturn are almost certainly visible from the upper reaches of its atmosphere. The rings are so thin that from a position on Saturn's equator, they would be almost invisible. From anywhere else on the planet, they could be seen as a spectacular arc stretching across half the celestial hemisphere. Download high resolution version (1024x692, 16 KB)Simulated view of the rings of Saturn at sunset, as seen from a position on Saturns equator; the rings are barely visible as a thin line. ... Download high resolution version (1024x692, 16 KB)Simulated view of the rings of Saturn at sunset, as seen from a position on Saturns equator; the rings are barely visible as a thin line. ... Download high resolution version (1024x692, 24 KB)Simulated view of the rings of Saturn, as seen from a position high in Saturns atmosphere. ... Download high resolution version (1024x692, 24 KB)Simulated view of the rings of Saturn, as seen from a position high in Saturns atmosphere. ... Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... The full set of rings, as photographed by the Cassini spacecraft on September 15, 2006 (brightness has been exaggerated in this image). ...

Saturn's moons would not look particularly impressive in its sky, as most are fairly small, and the largest are a long way from the planet. Even Titan, the largest moon of Saturn, appears only half the size of Earth's moon. Here are the approximate angular diameters of the main moons (for comparison, Earth's moon has an angular diameter of 31'): Mimas: 5-10', Enceladus: 5-9', Tethys: 8-12', Dione: 8-12', Rhea: 8-11', Titan: 14-15', Iapetus: 1'. The angular diameter of an object as seen from a given position is the diameter measured as an angle. ...

Saturn has a southern polar star, δ Octantis, a magnitude 4.3 star. It is much fainter than Earth's Polaris (α Ursae Minoris). Delta Octantis has the distinction of being Saturns southern pole star. ... Polaris (α UMi / α Ursae Minoris / Alpha Ursae Minoris), more commonly known as The North Star or simply North Star, is the brightest star in the constellation Ursa Minor. ...

The skies of Saturn's moons

Since the inner moons of Saturn are all in synchronous rotation, the planet always appears in the same spot in their skies. Observers on the sides of those satellites facing away from the planet would never see Saturn. Due to synchronous rotation of their moon, the inhabitants of the central body will never be able to see its green side. ...

In the skies of Saturn's inner moons, Saturn is an enormous object. For instance, Saturn seen from Pan has an apparent diameter of ~50°, 104 times larger than our Moon and occupying 11% of Pan's sky. Because Pan orbits along the Encke division within Saturn's rings, they are visible from anywhere on Pan, even on its side facing away from Saturn. Atmosphere none Pan (pan, Greek Πάν) is a moon of Saturn, named after the god Pan. ... The Encke Division in closeup The Encke Division, also called the Encke Gap, is a perceived gap within Saturns A Ring. ...

The rings from Saturn's moons

Saturn's rings would not be prominent from most of the moons. This is because the rings, though wide, are not very thick, and most of the moons orbit almost exactly (within 1.5°) in the planet's ring plane. Thus, the rings are edge-on and practically invisible from the inner moons. From the outer moons, starting with Iapetus, a more oblique view of the rings would be available, although the greater distance would make Saturn appear smaller in the sky; from Phoebe, the largest of Saturn's outermost moons, Saturn would appear only as big as the full Moon does from Earth. The play of distance and angle is quite sensitive to the values used, but calculations show the best view of the rings would be achieved from the inner moon Mimas, which lies a full 1.5° off Saturn's equatorial plane and is fairly near the rings. At their widest opening, when Mimas is at its maximum distance from Saturn's equatorial plane, the edges of the rings (from B to A) would be separated by 2.7 degrees. The co-orbitals Epimetheus and Janus would also get a good view, with maximum opening angles ranging between 1.5 and 2.9°. Tethys gets the next best view, with nearly half a degree. Iapetus achieves 0.20°, which is more than any of the outer moons can claim. Iapetus (eye-ap-É™-tÉ™s, IPA , Greek Ιαπετός) is the third-largest moon of Saturn, discovered by Giovanni Domenico Cassini in 1671. ... For other meanings see Phoebe. ... Mimas (mee-mÉ™s or mye-mÉ™s, IPA: , Greek Μίμᾱς, rarely Μίμανς) is a moon of Saturn that was discovered in 1789 by William Herschel. ... Epimetheus (ep-i-mee-thee-us, Greek Επιμηθεύς) is a moon of Saturn. ... Janus (jay-nus, Greek Ιανός) is a moon of Saturn. ... Atmosphere none Tethys (tee-thÉ™s or teth-É™s, IPA , Greek Τηθύς) is a moon of Saturn that was discovered by Giovanni Domenico Cassini in 1684. ...

The sky of Titan

Image of the surface of Titan from the Huygens probe

Titan is the only moon in the solar system to have a thick atmosphere. Images from the Huygens probe show that the Titanian sky is a light tangerine color. It seems likely that Saturn is permanently invisible behind orange smog, and even the Sun would only be a lighter patch in the haze. However, in the upper atmosphere, the sky would have a blue color and Saturn would be visible.^[4] Download high resolution version (316x630, 38 KB)Image of Titans surface taken by the Huygens lander on January 14, 2005; the simulated colour is based on spectral measurements taken by the probe. ... Download high resolution version (316x630, 38 KB)Image of Titans surface taken by the Huygens lander on January 14, 2005; the simulated colour is based on spectral measurements taken by the probe. ... Titan (, from Ancient Greek Τῑτάν) or Saturn VI is the largest moon of Saturn and the only moon known to have a dense atmosphere. ... The Huygens probe, supplied by the European Space Agency (ESA) and named after the Dutch 17th century astronomer Christiaan Huygens, is an atmospheric entry probe carried to Saturns moon Titan as part of the Cassini-Huygens mission. ...

The sky of Enceladus

Figure 15: An artist's view of Enceladus' sky.

Seen from Enceladus, Saturn would have a visible diameter of almost 30°, sixty times more than the Moon visible from Earth. Moreover, since Enceladus rotates synchronously with its orbital period and therefore keeps one face pointed toward Saturn, the planet never moves in Enceladus' sky (albeit with slight variations coming from the orbit's eccentricity), and cannot be seen from the far side of the satellite. Image File history File links Saturn_seen_from_Enceladus_(artist_concept). ... Image File history File links Saturn_seen_from_Enceladus_(artist_concept). ... Atmosphere Surface pressure: trace, significant spatial variability[8][9] Composition: 91% Water vapour 4% Nitrogen 3. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ...

Saturn's rings would be seen from an angle of only 0.019° and would be almost invisible, but their shadow on Saturn's disk would be clearly distinguishable. Like our own Moon from Earth, Saturn itself would show regular phases. From Enceladus, the Sun would have a diameter of only 3.5 minutes of arc, nine times smaller than that of the Moon as seen from Earth. Lunar phase refers to the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. ...

An observer located on Enceladus could also observe Mimas (the biggest satellite located inside Enceladus' orbit) transit in front of Saturn every 72 hours on average. Its apparent size would be at most 26 minutes of arc, about the same size as the Moon seen from Earth. Pallene and Methone would appear nearly star-like (maximum 30 seconds of arc). Tethys, visible from Enceladus' anti-Saturnian side, would reach a maximum apparent size of about 64 minutes of arc, about twice the Moon as seen from the Earth. Mimas (mee-məs or mye-məs, IPA: , Greek Μίμᾱς, rarely Μίμανς) is a moon of Saturn that was discovered in 1789 by William Herschel. ... Discovery image of Pallene Pallene (pa-lee-nee, Greek Παλλήνη) is a natural satellite of Saturn. ... Discovery image of Methone Methone (me-thoe-nee, Greek Μεθωνη) is a natural satellite of Saturn. ... Atmosphere none Tethys (tee-thəs or teth-əs, IPA , Greek Τηθύς) is a moon of Saturn that was discovered by Giovanni Domenico Cassini in 1684. ...

Uranus

Judging by the colour of its atmosphere, the sky of Uranus is likely greenish-blue. It is probable that the planet's rings can't be seen from its surface, as they are very thin and dark. Uranus has a northern polar star, Sabik (η Ophiuchi), a magnitude 2.4 star. Uranus also has a southern polar star, 15 Orionis, an unremarkable magnitude 4.8 star. Both are fainter than Earth's Polaris (α Ursae Minoris), although Sabik is only slightly fainter. Atmospheric characteristics Atmospheric pressure 120 kPa Hydrogen 83% Helium 15% Methane 1. ... Sabik is the proper name of the star &#951; Ophiuchi in the constellation Ophiuchus. ... 15 Orionis has the distinction of being the southern pole star of Uranus. ... Polaris (α UMi / α Ursae Minoris / Alpha Ursae Minoris), more commonly known as The North Star or simply North Star, is the brightest star in the constellation Ursa Minor. ...

Uranus is unusual in that the obliquity of its ecliptic is 82° (angle between the orbital and rotational poles). The North Pole of Uranus points to somewhere near η Ophiuchi, about 15° northeast of Antares and thus its South Pole halfway between Betelgeuse and Aldebaran. Uranus' "tropics" lie at 82° latitude and its "arctic circles" at 8° latitude. On December 17, 2007, the Sun passes the Uranian celestial equator to the North and in 2029 the North Pole of Uranus will be nearly pointed at the Sun. Sabik is the proper name of the star &#951; Ophiuchi in the constellation Ophiuchus. ... This article or section does not cite its references or sources. ... This article is about the star. ... Aldebaran from the Arabic (الدبران al-dabarān) meaning the follower, (α Tau / α Tauri / Alpha Tauri) is the brightest star in the constellation Taurus and one of the brightest stars in the nighttime sky. ... December 17 is the 351st day of the year (352nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... 2029 (MMXXIX) will be a common year starting on Monday of the Gregorian calendar. ...

Uranus' moons would not look very large from the surface of their parent planet. The angular diameters of the five large moons are as follows (for comparison, Earth's moon measures 31' for terrestrial observers): Miranda: 11-15', Ariel: 18-22', Umbriel: 14-16', Titania: 11-13', Oberon: 8-9'. The small inner moons would appear as starlike points, and the outer irregular moons would not be visible to the naked eye. The angular diameter of an object as seen from a given position is the diameter measured as an angle. ...

Neptune

Judging by the color of its atmosphere, the sky of Neptune is likely blue. It is probable that the planet's rings can't be seen from its surface, as they are very thin and dark. Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ...

Aside from the Sun, the most impressive object in Neptune's sky is its large moon Triton, which would appear slightly smaller than a full Moon on Earth. It moves more swiftly than our Moon, because of its shorter period (5.8 days) compounded by its retrograde orbit. The smaller moon Proteus would show a disk about half the size of the full Moon. Neptune's small inner moons, and its large outer satellite, Nereid, would appear as starlike points, and its irregular outer satellites would not be visible to the naked eye. Triton (trye-tÉ™n, IPA: , Greek Τρίτων), or Neptune I, is the planet Neptunes largest moon. ... This article is about retrograde motion. ... Atmospheric pressure 0 kPa Proteus (proe-tee-us, Greek Πρωτέας) is one of Neptunes moons. ... Nereid (IPA: , IPA: , Greek Νηρηίδα), or Neptune II, is a moon of Neptune. ...

The sky of Triton

Simulated view of Neptune in the sky of Triton

Triton, Neptune's largest moon, has an atmosphere, but it is so thin that the moon's sky is still black, perhaps with some pale haze at the horizon. Because Triton orbits with synchronous rotation, Neptune always appears in the same position in its sky. Triton's rotation axis is inclined 130° to Neptune's orbital plane and thus points within 40° of the Sun twice per Neptunian year, much like Uranus'. As Neptune orbits the Sun, Triton's polar regions take turns facing the Sun for 82 years at a stretch, resulting in radical seasonal changes as one pole then the other moves into the sunlight. Download high resolution version (1024x692, 16 KB)Simulated view of Neptune as seen from the surface of Triton. ... Download high resolution version (1024x692, 16 KB)Simulated view of Neptune as seen from the surface of Triton. ... Triton (trye-tÉ™n, IPA: , Greek Τρίτων), or Neptune I, is the planet Neptunes largest moon. ... Due to synchronous rotation of their moon, the inhabitants of the central body will never be able to see its green side. ... Sol redirects here. ... Atmospheric characteristics Atmospheric pressure 120 kPa Hydrogen 83% Helium 15% Methane 1. ...

Pluto and Charon

Artist's concept of the surface of Pluto's small satellite Hydra. Pluto & Charon (right) & Nix (bright dot on left).

Pluto, accompanied by its largest moon Charon, orbits the sun at a distance usually outside the orbit of Neptune except for a twenty-year period in each orbit. Image File history File linksMetadata Download high resolution version (4000x3000, 1051 KB)The artists concept above shows the Pluto system from the surface of one of the candidate moons. ... Image File history File linksMetadata Download high resolution version (4000x3000, 1051 KB)The artists concept above shows the Pluto system from the surface of one of the candidate moons. ... Hydra (formerly known as S/2005 P 1) is a natural satellite of Pluto. ... Adjectives: Plutonian Atmosphere Surface pressure: 0. ... Charon (shair-ən or kair-ən (key), IPA , Greek Χάρων), discovered in 1978, is, depending on the definition employed, either the largest moon of Pluto or one member of a double dwarf planet with Pluto being the other member. ... Nix (formerly known as S/2005 P 2), is a natural satellite of Pluto. ... Atmospheric characteristics Atmospheric pressure 0. ... Charon (shair-ən or kair-ən (key), IPA , Greek Χάρων), discovered in 1978, is, depending on the definition employed, either the largest moon of Pluto or one member of a double dwarf planet with Pluto being the other member. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ...

From Pluto, the Sun is still very bright, having a magnitude between roughly 150 and 450 times that of the full Moon from Earth (the variability being due to the eccentricity of Pluto's orbit). Nonetheless, human observers would find a large decrease in available light.

Pluto and Charon are tidally locked to each other. This means that Charon always presents the same face to Pluto, and Pluto also always presents the same face to Charon. Observers on the far side of Charon from Pluto would never see the dwarf planet; observers on the far side of Pluto from Charon would never see the moon. Every 124 years, for several years it is mutual eclipse season, when Pluto and Charon each eclipse the Sun for the other, at intervals of 3.2 days. Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ...

Comets

The sky of a comet changes dramatically as it nears the Sun. During perihelion, a comet's ices begin to sublime from its surface, forming tails of gas and dust, and a coma. An observer on a comet nearing the Sun might see the stars slightly obscured by a milky haze, which could create interesting halo effects around the Sun and other bright objects. Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... Sublimation of an element or substance is a conversion between the solid and the gas phases with no intermediate liquid stage. ... The comet Ikeya-Zhang exhibiting a bright, condensed coma (march 2002) In astronomy, the nebulous envelope around the nucleus of a comet is called its coma (from the Latin word for hair). It is formed when the comet passes close to the sun on its highly elliptical orbit; as the... It has been suggested that Moon dog be merged into this article or section. ...

Extrasolar planets

For observers on extrasolar planets, the constellations would be quite different. The Sun would be visible to the naked human eye only at distances below 20–25 parsecs (65–80 light years). The star β Comae Berenices is slightly more luminous than the Sun, but even over its relatively close distance of 27 light years, appears quite faint in our sky. An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... This article does not cite any references or sources. ... Sol redirects here. ... The naked eye is a figure of speech referring to human visual perception that is unaided by enhancing equipment, such as a telescope or binoculars. ... A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond. ... Coma Berenices (IPA: , Latin: ) is a traditional asterism that has since become a constellation. ...

If the Sun were observed from the Alpha Centauri system, the nearest star system to ours, it would appear to be a bright star in the constellation Cassiopeia. It would be almost as bright as Capella is in our sky. Alpha Centauri (α Cen / α Centauri, also known as Rigil Kentaurus), is the brightest star system in the southern constellation of Centaurus. ... A star system or stellar system is a small number of stars that orbit each other,[1] bound by gravitational attraction. ... Cassiopeia (IPA: ) is a northern constellation which Greek mythology considered to represent a vain queen who boasted about her unrivaled beauty. ... Capella (α Aur / α Aurigae / Alpha Aurigae) is the brightest star in the constellation Auriga and sixth brightest star in the sky. ...

A hypothetical planet around either α Centauri A or B would see the other star as a very bright secondary. For example, an Earth-like planet at 1.25 Astronomical Units from α Cen A (with a revolution period of 1.34 a) would get Sun-like illumination from its primary, and α Cen B would appear 5.7 to 8.6 magnitudes dimmer (−21.0 to −18.2), 190 to 2700 times dimmer than α Cen A but still 29 to 9 times brighter than the full Moon. Conversely, an Earth-like planet at 0.71 AUs from α Cen B (with a revolution period of 0.63 a) would get Sun-like illumination from its primary, and α Cen A would appear 4.6 to 7.3 magnitudes dimmer (−22.1 to −19.4), 70 to 840 times dimmer than α Cen B but still 45 to 15 times brighter than the full Moon. In both cases the secondary sun would, in the course of the planet's year, appear to circle the sky. It would start off right beside the primary and end up, half a period later, opposite it in the sky (a "midnight sun"). After another half period, it would complete the cycle. Other planets orbiting one member of a binary system would enjoy similar skies. The astronomical unit (AU or au or a. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ...

From 40 Eridani, 16 light years away, the Sun would be an average looking star of about apparent magnitude 3.3 in the constellation Serpens Caput. At this distance most of the stars nearest to us would be in different locations than in our sky, including Alpha Centauri and Sirius. 40 Eridani (also known as Omicron 2 Eridani, or Keid, from the Arabic word qayd (egg) shells) is a triple star system less than 16. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... Serpens (the snake) is one of the 88 modern constellations, and was also one of the 48 listed by Ptolemy. ... This list of the nearest stars to Earth is ordered by increasing distance out to a maximum of 5 parsecs (16. ... Alpha Centauri (α Cen / α Centauri, also known as Rigil Kentaurus), is the brightest star system in the southern constellation of Centaurus. ... Sirius B redirects here. ...

From a planet orbiting Aldebaran, 65 light years away, the Sun would appear slightly above Antares of our constellation Scorpio, and at magnitude 6.4 would barely be visible to the naked eye. Constellations made of bright, far-away stars would look very similar (such as Orion), but much of the night sky would seem unfamilliar to someone from Earth. Aldebaran from the Arabic (الدبران al-dabarān) meaning the follower, (α Tau / α Tauri / Alpha Tauri) is the brightest star in the constellation Taurus and one of the brightest stars in the nighttime sky. ... This article or section does not cite its references or sources. ... Scorpius (Latin for scorpion, symbol , Unicode ♏) is one of the constellations of the zodiac. ... Orion (IPA: ), a constellation often referred to as The Hunter, is a prominent constellation, one of the largest and perhaps the best-known and most conspicuous in the sky[1]. Its brilliant stars are found on the celestial equator and are visible throughout the world, making this constellation globally recognized. ...

A note on calculating apparent magnitudes

The brightness of an object varies (approximately, due to the curvature of spacetime on huge scales as given in general relativity) as the inverse square of the distance. The apparent magnitude scale varies as -2.5 times the (base-10) log of the brightness. Thus if an object has apparent magnitude m₁ at distance d₁ from the observer, then all other things being equal, it will have magnitude at distance d₂.^{[citation needed]}

References

External links

• Essay on the possible sky colours of alien worlds
• 3D Universe - The Universe as seen from other places and other times.
• Phases of Charon as seen from Pluto
• Rene Pascal - Renderings of the colours of Titan's sky from the surface to the upper levels of the atmosphere