What Would The Sun Look Like From Jupiter Or Pluto?

A full halo surrounds the waxing gibbous moon early yesterday evening. At right is the planet Jupiter. Details: 16mm lens at f/5.6, 15 second exposure. Photo: Bob KingPhoto: Bob King

Beauty of a halo around the moon last night! Within its circumference were the Pleiades and Hyades star clusters, Aldebaran and Jupiter – by a hair. Halos form in high cirrostratus clouds around the moon and sun from light refracted (bent) by billions of extremely tiny six-sided, pencil-shaped ice crystals into a circle of 22 degrees radius. Sometime halos last for hours; other times like last night, the clouds blew out 10 minutes after the photo was taken. One of my favorite “sub-hobbies” in astronomy is seeing what gets snared by these occasional lunar lassos.

The sun's apparent size as seen from the planets and Pluto. The numbers show the sun's diameter which ranges from 1.3 degrees (nearly three times the size of the sun in Earth's sky) to 0.75 arc minutes for Pluto. 30 arc minutes equal 1/2 degree or the diameter of the sun and moon. Illustration created with Stellarium / Bob King

Yesterday we talked about Earth being closest to the sun in January versus July. The difference of a couple million miles causes the sun’s size to vary a minute amount not detectable with the naked eye. That got me to wondering about how big the sun would appear from the various planets in the solar system, so I worked up an illustration to give you and idea of the sun’s size in the sky seen from Mercury all the way out to Pluto, not an official planet, but widely beloved as one just the same.

The illustration above shows the sizes to a good approximation at the planets’ average distances from the sun. The sun on Mercury, the closest planet, would be very obviously larger and the heat rather unbearable. Venus’ sun would also be noticeably bigger if you could see it through the perpetual cloud cover. It begins shrinking at Mars and becomes positively tiny at Jupiter’s distance of almost half a billion miles. Still, if you examined the sun through a safe solar filter from an airship cruising just above the giant planet’s cloud deck, you’d be able to distinguish a tiny, brilliant circle of light one-fifth the size of the full moon.

The sun's disk from Earth is obvious at a glance and can be studied in detail using a safe solar filter. Photo: Bob King

Saturn would be more challenging with the sun half the size as viewed from Jupiter. The accepted human eye limit for discerning the shape of an object in the sky is one arc minute or 1/30 the size of the sun or full moon. Only the sharp-eyed among us would be able to see the sun as a disk from Uranus and Neptune, while Pluto would elude all.

Perhaps the most amazing thing about the shrinking sun is that it remains extremely brilliant right on out to Pluto. Not radiant like the way we see it from Earth of course, but brighter than you might suppose. At the dwarf planet’s distance of 3.6 billion miles, the sun shines at magnitude -19 or eight magnitudes fainter than here at home. Standing on Pluto’s methane frosted surface, it would shine about 240 times brighter than the full moon. That’s the power of a star.

72 Responses

  1. Travis Kitch

    Hi Bob,

    With Mercury being as close to the sun as it is, it really seems counterintuitive that there is a good chance of water ice being there. I think we need to change the question “where is there water?” to “where isn’t there water?”

    Your thoughts?

    Clear skies to you,

    1. astrobob

      Hi Travis,
      No one would have guessed at ice being there. Like you say, it doesn’t make sense intuitively, but the circumstantial evidence for ice is strong in deep, permanently-shadowed craters at the poles. You can read more about it here: http://goo.gl/5mGqW

  2. -19 m from Pluto? Our star is truly amazing (and it is just a yellow dwarf, I can’t imagine what fusion infernos giant stars are)! But really, when seeing comparisons like this, one can maybe begin to perceive the vastness of space.

    I wonder what it would be like from the surface of Sedna, when it is in aphelion? 😉

    1. astrobob

      Good question. I bet you could look at it for a short intervals at Pluto since it would appear as a star just MUCH, MUCH brighter. But honestly, I don’t know the answer.

      1. mattias

        The actual surface that you see is of the same brightness. its just the area in the sky that is decreasing. its when the area in the sky becomes smaller that the resolving limit of your sensor that you start actually seeing an decrease in brightness.

        So when standing on europa or io you will totally destroy your eyes. your eyes will be in night mode with fully open iris because the sourroundings are so dark. The sun is a really small circle in the sky but it will still be just as bright to the photoreceptive cells that have the misfortune of being in that small area being hit. the energy transmitted to those cells will be exactly the same as standing it will not be pretty.


        1. mattias

          slipped on the keyboard in that last part…

          its supposed to be:

          …the energy transmitted to those misfortunate cells will be exactly the same as if you where standing here on earth with your iris totally open. it will not be pretty.


        2. Ameem

          Wouldn’t the illuminance be a lot less in farther planets? So the luminous intensity would probably be the same but there would be less light on your eyes. Imagine a high powered bulb lit in an otherwise dark big room. The closer you get, the more light you receive and gets unbearable at one point.

          1. sanj

            This answer is incorrect as far as I can see. A point source of light emits energy at a certain rate. The amount of sunlight collected by a photoreceptor depends on the angle subtended by the photoreceptor. At a given distance, this falls off as an inverse. In other words, the intensity is the ratio of the area of the photoreceptor to the area of the surface of a sphere around the sun with a radius equal to my distance from the sun.

            Now, it’s still an interesting argument, because my pupil will certainly be larger. And it’s not just the photoreceptor area that counts, but also the pupil area.

            For me to collect the same amount of light as on earth, my pupil will need to be somewhat larger. How big? Multiply the diameter of my pupil on earth, by the ratio of the pluto-sun distance to the earth-sun distance. In other words, the pupil needs to subtend the same (solid) angle on pluto, as it did on earth. Pluto is at 30AU. So my 5mm pupil would need to be 15 cm on Pluto – much bigger than my eye! You’d need a small telescope.

          2. astrobob

            I’m not sure I understand your point. Are you saying you’d need a telescope to see the Sun from Pluto? Or are you saying you’d need a telescope to resolve the Sun’s disk? You would need binoculars or a scope to see the Sun as a disk from Pluto, but the Sun would be brilliant – at least compared to the moon.

        3. sanj

          I was suggesting that there are two factors at play – first is that, as Mattias correctly said, fewer photoreceptors are active since the sun looks smaller. But second, that each photoreceptor receives less light too, because the pupil is a smaller proportion of the sphere, at that radius.

          I agree that magnitude -19 is still very bright. But I don’t think that the sun “will still be just as bright to the photoreceptive cells”. That’s just my thoughts and I’m not a physicist, so I’m happy to be corrected though!

  3. Dan

    Very nice explanations Bob and Mattias, I have been wondering about this for awhile now and you answered it. So given that the intensity is the same just the area occupied in the sky changes and therefore the ambient light, would it be a good analogy to think of it like watching arc-welding. So say from Io or Europa it you could not look directly at it but you would not have to shift your eyes much to get away from that intense light and then it would be safe?

    1. astrobob

      Hi Dan,
      Good question. The intensity of the sun’s light is not the same from Earth vs. Io vs. Pluto. It decreases with the square of the distance (inverse square law). The sun remains relatively brilliant from Pluto because Pluto is still close to the sun compared to the stars. From the nearest star Alpha Centauri (4.3 light years) it would be about as bright as Vega and be very easy to look at. Going back to arc welding. Up close, the intensity of the torch is ferocious and will damage your eyes. Now imagine looking at it from a mile away. At that distance it would appear as a small, bright but safe-to-look-at point of light. Does this help to explain?

    1. astrobob

      The sun would appear the same except whiter because there’s no atmosphere to give it the slight yellow tint we see from Earth. It would also appear in a black, star-filled sky – again, because there’s no atmosphere to scatter the light and make a blue sky like we have on Earth.

    1. astrobob

      Hi John,
      From the nearest star system, Alpha Centauri (4.5 light years away), the sun appears as a 1st magnitude star in the constellation Cassiopeia. It would shine as brightly as Deneb in the Northern Cross or Regulus in Leo. Since an object’s brightness is defined by the inverse square law – move a star twice as far away and it will appear four times fainter – the sun would shine at approximately 2.5 magnitude at 9 light years away and so on. At 25 light years it would definitely fade into the multitude of dimmer stars.

  4. argautreaux

    Hello, can you please tell me what size the Sun (in comparison to how we see it or say the Moon on Earth) would be if we viewed it from the surface of Europa? Rough estimates would be fine… Maybe two times the size of the Moon? Or a quarter the size of the Sun as we see it on Earth?

    I would be interested to know, thanks…

    1. astrobob

      Seen from the surface of Jupiter’s moon Europa, the sun would be 6 arc minutes across or 1/5 the diameter of the sun as seen from Earth.

  5. Thanks for your former answer.

    Continuing with comparing objects to that of the Sun or the Moon as viewed from Earths surface what would be the comparative size to Callisto as seen from the surface of Europa please?

    (Again rough estimates are helpful as you stated before with the Sun being 1/5 is size seen on Earth as it would be seen upon Europas surface. This information is very helpful to me and compelling, thank you kindly Sir)

    1. astrobob

      Since they each have their own orbit around Jupiter their distances vary. At closest approach, Callisto would be about 0.1 degree of 1/5th the size of the moon as seen from Earth.

        1. astrobob

          The sizes imply it’s possible to see a total or near total eclipse of the sun by Callisto from Europa. I wonder how often that happens?

  6. AstroBob, that sounds really compelling to imagine what a Callisto-clipse would be like! I bet it would be beautiful in perspective purposes alone! And what of Ganymede-clipses or Io-clipses? Is it Occulting when a body like Europa for example get lined up by he shadows of other planetary bodies in there shadow or Jupiter orbiting infront of it? I wonder?

    1. Perhaps Sir I could ask the rest of my questions now since we have briefly engaged in an open dialogue as I’m sure you have other pressing questions to answer too.

      My other two questions regaring the Jupiter system is:

      What would be the comparative size to Ganymede as seen from the surface of Europa compared to how we see the Sun or the Moon from Earth?

      And also, what would be the size of Io comparitively speaking to oor view of the Sun and Moon on Earth as seen from Europa as well?

      I thank you for your assistance…

      1. astrobob

        When Europa is closest to Ganymede, Ganymede would measure .37 degrees (22 arc minutes) across or 2/3 the size of the full moon. When Europa is closest to Io, Io would be .41 degrees (25 arc minutes) or about 4/5th the size of the our moon.

  7. This is fantastic and helpful information, thank you kindly for your assitance. I really love the planetoid/moon Europa. I see it like a little siter planet to Earth or like a little niece or granddaughter to Earth because it looks so tiny in comparison and because it may harbor some type of life within it.

    I like the film Avatar and the concept of the varying degrees of lifeforces and influences upon the hypothetical scenario James Cameron proposed for the Padora Planet-Moon and the idea that in some way the planets themselves may have been capable of communicating with each other analogous to whales except these are communicating of vast ‘Oceans’ of space in song perhaps.

    There is the saying that the universe talks to us and I particularly like the Odyssey series of books by Aurthur C Clarke and how different moons and the Sun are seen from various points-of-view throught the Jovian-Terran systems/locations.

    Thank you again Sir.



    1. astrobob

      Glad to be of help, Art. I’m sure there’s something interesting going on beneath Europa’s icy crust. I’d like to think that life might be possible there, too.

  8. I love the 2001: A Space Odyssey (book/film), 2010: Odyssey Two/The Year We Make Contact (book/film), 2061: Odyssey Three and 3001: The final Odyssey novels. In them from the second book onwards the concept of Jupiter going nova and being converted into a mini star is explored in facinating detail to me. it makes me wonder what Earth would be like existing within in effect a binary star sytem and the light effects a Jupiter/Lucifer/(Sol 2) mini-sun would look like and how it would look from the point-of-view of Earth. How Jupiter as a hypothetical mini-star would appear and look (in comparison to our own Sun & Moon on Earth) from the surface of Europa. Also what would Our Skies be like when the actual Sun set and the (Sol 2)/Lucifarian set was still in the sky occupying the same space and area as the former Jupiter did?

    I would love to know of the various insights into this hypothetical scenario as well Sir. How big would a Jupiter-Mini-Sun look from the surface of the Earth compared to our Sun and Moon during various seasons ans cycles of night and day? Thank you.

    1. astrobob

      Hi Art,
      While it looks great in a movie, there’s no possibility of Jupiter becoming a mini-sun or exploding as a nova or supernova. It has far too little mass for that to happen. Likewise for the sun. Novas occur in binary star systems when matter is transferred to a white dwarf from a sun-like star in close orbit around it. Material accumulates on the dwarf’s surface until it burned off in an explosion that doesn’t destroy the star. By the way, I enjoyed those movies too!

  9. No, I know it won’t do so, I’m merely inquiring as to what size roughly would Jupiter mass-as-arelative simmilar occupied area as a stra would look like from Earth? Would it be a few moon sizes as seen from the surface of the Earth? Three even? I know it will never happen! I’m just curious, hypothetically what size it would appear from the point-of-view of earths Surface thats all. You read my question earlier, you know I was merely theorizing Bob…

    Your help and co-operation would be appriciated.

      1. astrobob

        Since Jupiter can’t become a star I can’t really speculate. I wouldn’t be giving you accurate information.

  10. What creates the situation for a yo-yo planet? Does it get gravitationally perturbed out from its stable, jupiter-like orbit by another body another planet or nearby star by proximity and send it rebounding back and forth around its parent star?

    1. astrobob

      We’re learning that some extrasolar planets have orbits that are more elongated (cigar-shaped) compared to our solar system’s planets. A close-approaching star could do that but planets can also perturb other planets into a variety of orbits as a solar system evolves into a stable configuration.

  11. Bhargav

    Hi everyone, from the article it is evident that the sun would not be discernible to the naked eye from the methane frosted surface of Pluto.

    1) Would it still be dangerous to look in the direction of our star with an unaided eye from that distance?

    2) Would Charon be a brighter object than the sun in Pluto’s sky?

    3) Which of the planets would be visible without a telescope from Pluto?

    1. astrobob

      1. I’m not sure why you say the sun wouldn’t be seen with the naked eye. It would be by far the most brilliant thing in Pluto’s sky – 250 times brighter than the full moon appears from Earth. But it that light would be crunched into a tiny (incredibly brilliant) point of light. I’m not positive but I think the sun would still be dangerous to stare at for a long time.

      2. Charon would be considerably fainter than the sun but I don’t know what its magnitude would be.

      3. Great question. Neptune for sure and probably Uranus, Saturn and Jupiter though I would have to do the math to know for sure. All the inner planets would be too faint and also very near the sun.

      Anyone else care to calculate?

  12. Joe

    Earth has a day and night where the brightness of the day is markedly different than night. How “bright” is the day of the planets beyond Mars? I imagine daylight on Saturn as similar to dusk or dawn on Earth. At what distance would the Sun no longer be able to produce a noticable “daytime” on the planet/exoplanet in question?

    1. astrobob

      You can use the inverse square law to figure out brightness at varying distances. The Earth is 1 a.u. from the sun and Saturn is 10 (one a.u. or astronomical unit = 93 million miles). Since it’s 10x farther away it’s 1 over 10 squared or 1/100 as bright. That translates to 5 magnitudes dimmer than seen from Earth or about -21 magnitude — still very bright at least at the cloudtops of the Saturn. Even at Pluto (39 a.u.) the sun is more than 250 times brighter than the full moon though very tiny. To the eye it would look like an incredibly intense star, but you’d be able to get around just fine. It would look something like bright twilight. At 80 times the Earth’s distance from the sun, the sun would still be more than 60x brighter than the full moon. At 1000 a.u., the sun would be just 0.4x as bright as the full moon, providing a reasonably dark night. 1000 a.u. equals 93 billion miles or .0155 light years (3.5% the distance to Alpha Centauri).

      1. Joe

        I think you answered my question; daytime on Mercury would be hard on the eyes without sunglasses; and the Sun is bright enough to produce a noticeable daytime even on Pluto.

      2. jeff

        I think one of your numbers is off by an order of magnitude, as Alpha Centauri is about 4.4 light years distant. Thanks!

        1. astrobob

          Hi Jeff,
          I’m unclear on your comment. I made no mention of Alpha Centauri in the article. Did you see something in another blog?

          1. jeff

            Astrobob: I was referring to your reply to Joe, in which you wrote: “1000 a.u. equals 93 billion miles or .0155 light years (3.5% the distance to Alpha Centauri). ”



          2. astrobob

            Hi Jeff,
            Thanks for pointing that out. You’re right. My flub – the decimal was off. It’s 0.155 light years but the percent distance to Alpha Centauri (3.5%) is correct.

  13. Sira Sudhindranath

    This question is somewhat tangential. Up to what distance would Jupiter be visible to the naked eye? [assuming Earth-like viewing conditions] My rough calculation gives me about 600AU. Is that right?

    1. astrobob

      Hi Sira,
      I get half that value or about 300 A.U. At this distance Jupiter would be about 6th magnitude, the typical naked eye limit.

    1. astrobob

      Hi Hannah,
      The sun would be 6 arc minutes 1/10 of one degree) in diameter or 1/5 the size of the sun as we see it from Earth.

  14. Gison

    Thanks for this cool article. I’m curious about direct and ambient light produced by the sun on Jupiter’s moons. Someone asked this about Saturn and I understand the math you gave in response but I was hoping you could elaborate what it would “feel” like on Jupiter’s surface or on one of its moons. Say on Europa : how brightly would the sun light the landscape? Would it still feel like “daytime” to us? I understand the atmosphere is different but for argument’s sake let’s say it had an atmosphere like earth, would you get a blue sky and hard shadows from the sun?
    Once I saw a partial solar eclipse where the sun was about 75% covered and it was still very much daytime, even though there was a bit of a “faded photograph” effect all around. Hard shadows, blue sky, etc. Is that what it would be like on a moon near Jupiter with an earthlike atmosphere? Or would it be more like a bright full moon?

    1. astrobob

      I’ve read that on Saturn’s moon Titan, it would only be as bright as twilight here on Earth, so it would take some getting used finding your way around. From Europa, Jupiter would be the most prominent object in the night sky at 16 degrees across. But it would only be visible on side of the moon because it’s rotation is synchronously-locked to Jupiter like the moon is to Earth. Since the angular size of the sun at Europa/Jupiter’s distance is 1/5 that at Earth, shadows would be noticeably sharper. Europa’s sky is black but assuming an atmosphere similar to Earth’s, the sky would be deep blue. As for how bright it would look at the surface, sunlight is 27 times fainter at Europa/Jupiter than Earth, my educated guess is that it would appear similar to near sunset with clouds blocking the sun.

  15. AstroBob: Can the sun really be seen from Jupiter? The clouds are very thick and dense.

    One artist’s conception I saw of Jupiter was of a black sky constantly crackling with lightning, along with crashing “ocean” waves, as Jupiter probably has no real “surface”.

    1. astrobob

      Hi Richard,
      Yes, it can but only from orbit and within the upper cloud layer. Further down the sky would be black with with occasional lightning/thunderstorms. After traveling through thousands of miles of clouds, a visitor would encounter a thick layer of liquid metallic hydrogen and finally a core of heavier elements. Bottom line: no where to stand on the planet.

  16. P.

    Hi astrobob,

    I have a related question that’s crossed my mind now and again. If the Earth orbited a larger star like Sirius, at what distance would we need to be in order to receive the same amount of solar radiation that we now do from the Sun? And at that distance, how would the apparent size of Sirius compare to that of our Sun?

    Or, here’s a more general way of framing the question: if a star appears to be the same size as the Sun in a planet’s sky (whether it’s as big as Sirius or as small as a red dwarf), then is that planet receiving a comparable amount of radiation vs. Earth and Sol? Would any star that looked as big as the sun in our sky give us a Sol-like amount of light and heat?

    1. astrobob

      These are great questions. I’m not a math guy, but Sirius is 20 times more luminous than the Sun and 1.75 times larger. If you put Earth in orbit around Sirius and not quite double its distance to about 160 million miles, Sirius would appear about as large as the Sun. Brightness decreases with the square of the distance, so a doubling of distance would mean Sirius would still shine about 4 times brighter than the Sun. This implies that no, even when we move away from Sirius to make it same size as the Sun, it’s still brighter. Those with a greater knowledge of math may want to check my figures! It would seem then that we’d have to move approximately another Earth-Sun distance (93 million miles) from Sirius for its brightness to be the same, which in turn would make it smaller in apparent size than the Sun.
      More on the inverse square law here: http://www.ifa.hawaii.edu/~barnes/ASTR110L_S03/inversesquare.html

      1. P.

        Hi astrobob,

        Many thanks for your thoughtful and detailed reply! Someday I’d love to see a post summarizing how far we’d have to be from any given star to experience Earth-like conditions (acknowledging that different stars have different spectra), and how large that star would appear in our sky. The numbers for Betelgeuse or VY Canis Majoris would be very interesting indeed.

  17. Beverly Wright

    Relatively speaking, what would the earth look like from the sun? My rough equivalency calculation: If the sun were one meter away, the earth would be a tiny dot, 0.008mm in size. This compares the distance to the sun and the diameter of the earth.

    I saw the “Pale Blue Dot” on the show Cosmos. Makes you think!

    1. astrobob

      Hi Beverly
      That sounds about right. It would look exactly like a star with the naked eye. At full earth phase, the Earth’s disk would be about 16″ across seen from the Sun. In strong binoculars it would start to show a round shape but you’d really need a telescope to distinguish it clearly.

        1. astrobob

          Hi Carol,
          The maximum diameter of Mercury from Earth is 13″. From the Sun it would be 33″, so you’d still need a telescope to see its shape.

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