Jupiter Is Outstanding at Opposition

Prime-time Jupiter viewing kicks off this month when the planet reaches opposition on June 10th. 

Jupiter cruises Ophiuchus

Jupiter calls Ophiuchus home this summer. It's currently moving westward in retrograde motion and remains low in the south, around declination –22°, throughout its current apparition.
Stellarium

Over the past few weeks Jupiter has glared seductively in the southeastern sky. Before going to bed I'd gaze in its direction and debate taking out the telescope but stop short, convincing myself it was still too low for a good look. I finally caved this past weekend and observed it two nights in a row. Ha — the views were absolutely horrible! The big yellow planet rippled in the turbulent air like a flag in the wind, but that didn't matter. I finally had to respond to its invitation.

On June 10th, Jupiter will be at opposition and its brightest and closest to the Earth for the year. Shining at magnitude –2.6, it sports a plump equatorial diameter of 46″, only 4.1″ shy of its maximum apparent size. In observational astronomy, bigger and brighter almost always means better, the reason the next few months are the best time of year to swing your telescope the giant planet's way. Though it rises around sunset, it still takes time to climb high enough for a good view. For now, that's around 11:30 p.m. local time but come the end of the month, Jupiter stands 20° high before twilight ends.

It southerly declination this season means that low-altitude turbulence will hamper viewing for observers in mid-northern latitudes. Try to observe it every clear night if you can, the better to catch  nights of calm and steady seeing when the planet sits rock-steady and sharp.

Jupiter horses around

Jupiter dominates the southern sky in this photo taken on June 1st around 11:30 p.m. from northern Minnesota. It's currently shining from the "front leg" of the Great Dark Horse, a conglomeration of dark nebulae that resembles a horse tipped on its side, seen in the center of the image.
Bob King

Something for everyone

In steadily-held 10× binoculars you can pretend you're Galileo and rediscover its four brightest moons — Io, Europa, Ganymede, and Callisto. They look like tiny stars "sticking" to either side of the planet. If you don't have a way to mount binoculars on a tripod, use the roof of your car or pivot them against a corner of a building to keep your glass steady.

Jovian system

Jupiter's four brightest moons are easy to spot in a small telescope or binoculars. Don't expect to see all four all the time as one or other often pass in front or behind the planet. 
Bob King

Jupiter truly shines in a telescope, and you don't necessarily need a big one to see a lot. Etched in my brain cells is an image of a sharp, gleaming disk striped with two dark belts and accompanied by four star-like moons through my 2.4-inch refractor in the winter of 1966. A 6-inch reflector will make you privy to nearly all of the planet's secrets.

When the air calms and seeing conditions allow, you can make out the prominent North and South Equatorial Belts (NEB / SEB) plus a half-dozen narrower cloud belts and the brighter zones that separate them. They're all nearly parallel, making the planet look like a slice of Greek baklava pastry, one of my favorite desserts. Zones define regions of colder air topped by white-colored ammonia ice clouds. Descending gas defines the darker belts; their dark red color is believed to be caused by trace amounts of sulfur, phosphorus, and other organic compounds.

Jupiter's Belts and Zones

Jupiter's cloud pattern of belts and zones has remained remarkably constant over the last century. Yet when seen at high magnification, the various regions display an ever-changing array of small wisps, spots, and whorls, a dynamic weather system driven by high-speed winds.
S&T

Jupiter's iconic Great Red Spot (GRS) has been shrinking over the past several decades and currently spans about 1.3 Earths, but it remains colorful and easy to see at 100× and higher in good seeing. This season, jet streams in the SEB and South Temperate Zone (STZ) have been peeling away at the GRS the way you might peel an orange. More on that in a moment.

Jupiter has no solid surface. Nothing but clouds and weather, so you never know exactly what you'll see when eye meets eyepiece. That's the planet's charm, and it's aided by the antics of its moons. When magnified at 150× or higher they lose their star-like appearance and show disks that range in size from 1.0″ to 1.7″ (current opposition). Europa's the smallest and Ganymede largest.

Left: Double shadow transit of Ganymede (top) and Io in January 2013. Right: Diagram showing the mechanics of shadow transits, eclipses, and occultations viewed from above Jupiter's north pole.
Damian Peach (left); Bob King, (after an Encyclopedia Britannica diagram)

Ganymede also casts the largest shadow on the planet's cloud tops when it transits in front of Jupiter. Shadow transits are visible at least once a week with "double transits" — two moons casting shadows simultaneously — occurring once or twice a month. Ganymede's shadow looks like a bullet hole, while little Europa's more resembles a pinprick. Moons also fade away and then reappear over several minutes when they enter and exit Jupiter's shadow during eclipse. Or a moon may be occulted by the Jovian disk and hover at the planet's edge like a pearl before fading from sight.

You'll find a complete list of all eclipses, transits, and occultations for 2019 by downloading Sky & Telescope's Phenomena of Jupiter's Moons pdf. You can also gets daily predictions for the moons and a diagram showing their relative positions by consulting the online Jupiter's Moons Observing Tool. To predict when the Great Red Spot is best visible go to Transit Times of Jupiter's Great Red Spot.

Flakey Red Spot

On June 1, 2019, Jupiter displayed a prominent, dark NEB, a butterscotch-colored EZ, multiple bands in the SEB, and the Great Red Spot. A chunk of red cloud is visible adjacent to the GRS along its southeastern side (lower right). It may be material cleaved from the spot. The moon Io and its shadow appear at upper right. The current System II longitude of the GRS is about 308°. North is up.
Christopher Go

Jupiter's a colorful planet with belts various shades of red, rust, and gray. The Equatorial Zone (EZ) is normally white but is experiencing a clearing event this season that exposes a lower level of pale brown clouds. Using a magnification of 100× or higher, keep a lookout for dark festoons that resemble commas extending from the inner edge of the (very dark) NEB southward into the EZ. At first glance, the NEB might appear dark gray to your eye, but if you examine it closely at medium to high magnification you'll notice that it's actually a dark rust or even brick red.

Round and round the Red Spot

You can see subtle changes in and around the Great Red Spot in this sequence of images taken over the past 5 years. The wraparound cloud shaped like a spoon appears to have formed sometime last spring.
Christopher Go

The Great Red Spot maintains its orange-red hue as in recent years, a color shared by the sulfur-encrusted, volcanic moon Io, the only of Jupiter's bright satellites to show a distinctive color. In poor seeing the GRS is just an orangey smudge and looks rather small. But in calm air you'll spy the "moat" of lighter clouds called the Red Spot Hollow around it. Preceding the spot (celestial west), the SEB divides into 3–4 closely-spaced parallel belts, but following the spot (east), we currently see one prominent belt riddled with turbulent textures paralleled by a thinner stripe to its north.

This diagram by Clyde Foster notes details seen around the Great Red Spot from late May 2019.

Changes in the Great Red Spot

Jet streams in the SEB and South Temperate Zone have been shredding bits and pieces from the GRS for the past few weeks, distorting the spot's shape from time to time. As of June 2nd, winds are carrying a snip or "flake" of the GRS to its southeast. While astronomers have observed activity like this before, it's happening at a much faster rate than usual. Combined with the spot's shrinkage, some of us wonder whether this centuries-old storm's days are numbered.

Larger telescopes show more details within and between the cloud belts and make it easier to see the moons themselves as they transit Jupiter's disk. If you own a 12-inch or larger scope, try to spot a 5th moon — Himalia. Himalia is Jupiter's 6th largest moon at 170 kilometers across but only reaches magnitude 15.0 at this opposition. Its extended and tilted orbit (29.6° to Jupiter's equator) puts it a long way out from the planet. On opposition night, the moon lies about 17 arcminutes south of Jupiter and is difficult to make out in the planet's glare. Wait till late July when its separation increases to around nearly 1° to have a go at it.

Way-out Himalia

Jupiter's outer moon Himalia, visible in larger amateur telescopes, swings far from the planet. Here we see it in relation to Jupiter on July 20, 2019.
Stellarium

To find Himalia, create a map using a sky-charting software program like Stellarium. If you use that particular program, be sure to download the additional star catalogs to expand its magnitude range to 15.

Giant planet, dwarf planet

Ceres is easy to find shining at magnitude 7 above the head of Scorpius this month. Positions are marked every 3 nights for 10 p.m. CDT. Because the dwarf planet moves relatively slowly, the positions are good for many time zones. Stars are shown to magnitude 7.5.
Chris Marriott’s SkyMap with additions by the author

How about a little bonus while you're in the neighborhood? The brightest and easiest-to-see dwarf planet, Ceres, is only a week past opposition and shines at magnitude 7 some 15° west of Jupiter in Scorpius. You can easily find it in binoculars just a few degrees north of the beautiful double star Beta (β) Scorpii (a.k.a. Graffias) using the provided map.

Lather on the mosquito repellent and enjoy a peaceful night at Jupiter's knee.

27 thoughts on “Jupiter Is Outstanding at Opposition

  1. RodRod

    Bob – excellent! Late night 03-Jun and early morning 04-Jun (New Moon period) I was out observing Jupiter 🙂 It was great! The night was clear with temperature 50F/10C. Here is a note from my log:

    [Observed Io shadow eclipse at 0310 UT on 04-Jun-19 or 2310 EDT 03-Jun-19. I viewed Jupiter using the 90-mm refractor and my 10-inch telescope. Io eclipse viewed using the 10-inch at 154x with 14-mm eyepiece and 1.8x barlow lens (worked well with my eyeglasses). I used #12 Yellow filter. Jupiter very bright in the 10-inch and many cloud bands visible. Near 2310 EDT according to my cell phone time, Io disappeared in eclipse, see June Sky & Telescope published Phenomena of Jupiter’s Moons, p.51. Tonight, I enjoyed views of Jupiter from 31x to 214x. The 10-inch view using #58 Green filter is still a bright image. The 14-mm eyepiece with 2.5x barlow lens worked will with my eyeglasses (214x view). One star, HIP84543 visible between two of the Galilean moons (Ganymede side). The star is also HD 156182 on the SIMBAD portal, spectral class G3V, mv +9.33. This was easy to see in the 10-inch telescope view of Jupiter. Jupiter retrograding in Ophiuchus and putting on the show as it approaches opposition on 10-Jun-19. The earth’s rotation obvious when viewing Jupiter, especially at high power views. HIP84543 star compared to the Galilean moons apparent magnitude was about 33x fainter.]

    The star HIP84543 was some 470-500 light-years away compared to Jupiter and the Galilean moons visible (closer to 4.3 AU distance). Bob – viewing Jupiter is fun 🙂

    1. Bob KingBob King Post author

      Rod,
      “Viewing Jupiter is fun.” I agree wholeheartedly. Cool that you got an extra if temporary “Galilean moon.” After my mushy weekend-viewing of the planet we had perfect seeing last night. Great views in the 10-inch scope at 214x. The yellow-brown color of the equatorial region is very obvious compared to other years. I missed the GRS, but the main SEB (SEBs) is very dark and narrow compared to the chunkier NEB. A couple other faint belts were visible in the polar regions, the most obvious being the North Temperate Belt. Crossing my fingers for good seeing and a happy transit of the GRS.

      1. RodRod

        Bob, thanks. Recently I reviewed some of the history of astronomy measuring the Earth-Sun distance (ancient Greeks through Tycho Brahe efforts to measure the parallax of Mars and 1672 Cassini telescope observations for the parallax of Mars) and the stellar parallax obtained in 1838 for the star 61 Cygni. Viewing Jupiter, the Galilean moons, and a faint star in the field of view near Ganymede, I have greater appreciation for the hard work of past astronomers who labored to achieve the results we understand today concerning the dimensions of the solar system and distances to the stars when I see configurations like this using my telescopes.

      2. RLCLARK21157@Gmail.com

        On naked eye Jupiter Disk: I don’t think that arguments about distance between eye cones has much to do with it! The eye (actually the brain) integrates. The focal length of the individual eye matters. see article in ATM. Some folks have “longer” eyes than others.
        The most important reason for not seeing Jupiter as non-point is brightness!!! Make a hole in a business card with a thumb tack (a little bigger than a pin hole). Place it CLOSE to your eye. The resulting high f ratio dulls the view and masks out lots of surface errors of your eye. Even my aged eyes.

  2. Kerbal9

    Thank you for article. Few days ago i’d observing transit Ganymede and shadow. For my place Jupiter have only 10° above horizon at culmination and this is pain 🙂

  3. Anthony BarreiroAnthony Barreiro

    Thanks Bob.

    For the past few weeks I’ve been enjoying watching Ceres moving retrograde from Ophiuchus toward Scorpius, through binoculars. That stretch of milky way has plenty of sixth- and seventh-magnitude stars to serve as waystations from Nu Scorpii.

    I find it easier to observe Jupiter around the quadratures, when Jupiter is 90 degrees from the Sun in the sky, more so than around opposition. Jupiter is always big and bright, and it’s easier to get the telescope out around dawn and dusk than around midnight. Around quadrature Jupiter’s shadow falls farthest from the planet as seen from Earth, and that makes for dramatic eclipses of the Galilean moons.

    Last Saturday night at my astronomy club’s monthly members night star party on Mount Tamalpais I was using a 60 mm f/5.5 refractor. Jupiter was low in the sky and the seeing was poor. The little telescope provided noticeably better views than much bigger telescopes. Sometimes smaller is better.

    1. RodRod

      Anthony, glad to hear you enjoy viewing Jupiter using a 60-mm refractor. When I viewed earlier this week I used my 90-mm refractor and 10-inch Newtonian, comparing the views at different powers. Both telescopes gave excellent views of Jupiter, the 10-inch much brighter. At my location, Jupiter is close to 29 degrees altitude in the south sky near 0100 EDT (I am close to 38.8 N latitude in Maryland along the Patuxent river farms and area in rural zones-horse farms and alpaca farms). Bob King’s report and the June issue of Sky & Telescope show the Galilean moons will be visible to small telescopes as moons. I noticed this when viewing Ganymede especially at 154x and 214x. No longer a point source of light and my 90-mm at 200x does the same. I checked out Mount Tamalpais area on Google 🙂 It looks like a very nice area for stargazing so enjoy the skies. Today I have clouds in Maryland through early next week with likely rain on the way. Jupiter viewing will have to enter a holding pattern for me 🙂

  4. benjaminjg

    Thank you for the in-depth article. Some articles I’ve read in “regular” news publications mention that Earth will technically be closest to Jupiter on 6/12/19 around 11 PM due to the shape of Jupiter’s and our orbit. Can you shed some light on the validity of this calculation? Thanks!

    1. Bob KingBob King Post author

      You’re welcome, Benjamin. Although Jupiter is a tiny bit closer on the 12th, the article refers to its closest approach in a broader way, ie. at and around opposition. Thanks for your comment.

  5. RodRod

    benjaminjg, I checked the June issue of Sky & Telescope, Planetary Almanac, Stellarium, and Starry Night. None show Jupiter closer to earth on 12-Jun-19 at 2300 hours compared to the 10th. Jupiter is just a tiny *bit* farther away as measured from the center of the earth on the night of the 12th.

    1. Joe StieberJoe Stieber

      I just checked for the closest approach with the United States Naval Observatory’s MICA software (my canonical reference for such things). Jupiter will be closest for this 2019 opposition on June 12, about 03:05 UT (4.283896404 au). For those of us in the USA, closest approach will therefore be on June 11, 11:05 pm EDT or 8:05 pm PDT. Indeed, the difference between the opposition distance and the distance at closest approach 1.5 days later is miniscule.

      1. RodRod

        Joe Stieber et al, the USNO software looks the best and an excellent system of record (SOR) 🙂 Today at 2045 EDT or 0045 on 11-Jun-19, Starry Night shows Jupiter 0.284 AU from earth and so does Stellarium 0.19.0. This is slightly better than the June Sky & Telescope ephemeris, Planetary Almanac on page 44 of the issue.

  6. alanadler

    Hello Bob,
    Thank you for your fine article on Jupiter, a favorite of mine. But I’m taking a minute to expand reader’s viewing opportunities. You suggested a “clear night”. But the very best photo I ever shot of Jupiter and of Clavius (on the Moon) was shot through thin clouds. The cloud dimmed my targets slightly, but they dampened the turbulent atmosphere. Sky and Tel published that Clavius shot several times.
    Regards,
    Alan

  7. RodRod

    Bob King et al. Last night and early this morning Jupiter put on a double shadow transit show by Io and Ganymede. I observed from 2150 EDT until 0100 EDT, when more cirrus clouds moved in from the west so I went in. I wanted to observe the Great Red Spot rotate into view and transit near 0307 EDT but clouds did not cooperate. It was great viewing Jupiter using my 10-inch telescope and 90-mm refractor, 86x and 200x views and with the 10-inch, #58 Green filter. Io and Ganymede approached Jupiter’s limb as I observed near 2150 EDT like two fighter jets in close formation. The moons moved across the face of Jupiter. Both shadows visible and distinct as they orbited Jupiter (many cloud bands on Jupiter too). Both moons looked like small disk shape, especially near the limb of Jupiter and Ganymede easily a small, round moon shape or disk (200x views). Ganymede’s shadow was larger than Io so easy to see in both telescopes. This was a double solar eclipse event day at Jupiter I viewed put on by Io and Ganymede – great outdoor fun with temperature in upper 50s. Near the limbs of Jupiter, I could see Io and its shadow and Ganymede and its shadow moving slowly above the cloud tops of Jupiter. Really cool stuff 🙂

  8. Russell SampsonRussell Sampson

    Excellent article with lots to challenge the Jovaphile. Here’s a naked eye challenge for those observers wishing to push their observing skills and acuity to their limit.

    At its current opposition Jupiter’s angular diameter is about 46-arcseconds. The naked-eye resolving limit of the eye’s fovea, assuming photopic vision (i.e. cones), is about 30-arcseconds*. This is determined by the angular separation of two adjacent cones at the center of our vision. Jupiter is bright enough to assume photopic vision and thus maximal resolution of the eye. Therefore, for someone with good vision – or properly corrected vision – the planet should appear non-point-like. Jupiter should appear as a tiny disk. I have been testing this hypothesis for the past two oppositions and it appears to be true.

    Here is what I’ve observed. The optimal time for observations is in twilight, just as Jupiter is rising into the Earth’s shadow. This is the time when the eye’s distortion “spikes” are minimized. These spikes are produced by astigmatic distortions of the eye and appear as flares around the image of the planet. As the sky grows darker these spikes appear to increase and mask the planet’s shape. Also, this opposition has Jupiter only about 10-degrees east of Antares and once this star is visible Antares’ point-like appearance can be quickly compared to Jupiter.

    On June 11 around 20:55 EDT (00:55 UT June 12) from my eastern Connecticut location I could easily distinguish the apparent difference between Jupiter and Antares. Jupiter appeared to have a distinctive shape while Antares appeared more obviously point-like. I was wearing glasses at the time and my corrected vision is a little better than 20/20.

    *http://faculty.virginia.edu/ASTR3130/lectures/humaneye/humaneye.html

    1. Bob KingBob King Post author

      Hi Russell — I understand you’re having difficulty accessing comments. Thank you for sending along your response, which I will post for you (see below).

      From Russell Sampson to Rod and Bob:

      The presence of the Galilean moons may have an effect if they were visible to the unaided eye at the time of the observations. Since the perception of the disk of Jupiter took place in bright twilight, the naked eye visibility of a 4th or 5th magnitude moon would have been very difficult. I even checked with my binoculars and the moons were not visible in binoculars until well after I perceived the naked-eye disk of Jupiter.

      By the way, Rod thanks for the fascinating note on Tycho’s attempt to measure the diurnal parallax of Mars. Was the 4.5-arcminute threshold a combination of instrumental error and visual resolution?

      Bob, as for the difference between resolving a 30-arcsecond separation of two objects versus the resolving of a 30-arcsecond disk – I am also uncertain of the distinction – hence one of the reasons for this experiment.

      The first time I perceived the naked-eye disk of Jupiter was around the previous opposition (2018) and it occurred by accident. I was simply trying to observe the rising of Jupiter in the twilight and when it first appeared, its un-point-like shape surprised me. It was only afterwards that I checked to see if Jupiter at opposition was within the resolving ability of the human eye. This would suggest that it might not have been what psychologists call “Observer’s Bias” – seeing what one expects to see.

      Since the appearance of the disk of Jupiter occurs when the contrast between the sky and the planet are low (i.e. when the sky is bright), this would appear to suggest that the effect is not produced by a kind of retinal “blooming” akin to the effect we see in overexposed star images on film and CCD detectors.

      Also, since my corrected vision is better than 20/20, it would be expected that not every observer would be able to perceive the naked-eye disk of Jupiter. Nonetheless, even a negative result is an important result since one of the reasons we observe the sky is to better understand what can be seen.

      1. RodRod

        Bob/Russell, fascinating here. Tycho Brahe naked eye instruments attempted one arcminute resolution and corrections from what I have read researching past astronomical journals published on NASA ADS Abstract service. The Mars parallax of 4.5 arcminute was something predicted by Copernicus and Tycho wanted to refute Copernicus. Ptolemy geocentric astronomy apparently always showed Mars was farther away from earth than the Sun, Copernicus corrected this. The big question – where in astronomical history do we have solid documentation showing naked eye astronomers like Tycho Brahe could see Jupiter as a disk shaped planet when it is < 1 arcminute size?

        1. RodRod

          FYI. This is an interesting report on Tycho Brahe ability to measure arcminute size using naked eye astronomy and the instruments he designed and used. “Tycho Brahe’s Copernican campaign.”, https://ui.adsabs.harvard.edu/abs/1998JHA….29….1G/abstract

          The 34 page PDF report attached indicates Tycho would have trouble measuring angles smaller than 3 arcminute size for the Mars parallax campaign he conducted against Copernicus and the heliocentric solar system model, under development in those days.

      2. RodRod

        Bob King et al. One more note on this interesting discussion. Here is another reference “Dividing the circle. The development of critical angular measurement in astronomy 1500 – 1850.”, https://ui.adsabs.harvard.edu/abs/1995dcdc.book…..C/abstract, “Publication: Dividing the circle. The development of critical angular measurement in astronomy 1500 – 1850., by Chapman, A.. Wiley, Chichester (UK), 1995, 215 p., ISBN 0-471-96169-8, Price £ 24.95.”

        There is a long history of astronomical effort to measure very small angles, the sizes of the planets, and parallax for Mars, Venus, Mercury, the solar parallax and later, stellar parallax. Observing and measuring accurately the angular size of planets is an important part of the debate between geocentric astronomy vs. heliocentric solar system astronomy.

  9. RodRod

    I wonder if the difference between Jupiter and Antares observed naked eye near opposition of Jupiter is because of the Galilean moons. Sometimes they can be 3-4 arcminutes from Jupiter. Tycho Brahe in the 1580s attempted to observe the parallax of Mars in efforts to overthrow Copernicus. Tycho thought at opposition, Mars parallax would be near 4.5 arcminute – the threshold for his naked eye observations. Cassini and Richer measured the parallax of Mars in 1672 using telescopes, the parallax of Mars was much smaller than 4.5 arcminutes. The dimension of the solar system started being worked out including the astronomical unit, distance between earth and the sun after the 1672 measurements obtained using telescopes. Prior to 1672, geocentric astronomy taught a large earth with small distances between earth, the planets, the Sun and the stars. Claudius Ptolemy geocentric astronomy taught the outer sphere of stars were only 20,000 earth radii from earth or about 0.85 au of the modern distance measurement for the astronomical unit. Tycho Brahe and other geocentric astronomers thought the universe was much smaller and closer to a large earth, thus Jupiter was much closer too than the modern, heliocentric solar system distances.

    1. Bob KingBob King Post author

      Thank you, Russell. You make a good argument, and dusk or dawn would seem to be the best time to attempt to discern Jupiter’s disk, but I’ve always heard that our eyes can only resolve objects of 1 arc minute across or larger. Jupiter is under that limit. The article you referenced is an excellent one. I see where cone-spacing is discussed with a 30″ separation between cones. What I’m wondering is if that applies to a single object (resolving a disk down to 30″) or a 30″ separation between two objects.

  10. RodRod

    Bob King et al. When it comes to naked eye astronomy, I think using double stars is the best method. Here is a past report from Bob King 🙂 https://www.skyandtelescope.com/astronomy-news/observing-news/see-summers-best-naked-eye-double-stars-07092014/

    What was Tycho Brahe’s double star observation limit? I am not aware of naked eye astronomers splitting a double star 1 arcminute angular separation in the night sky. I know when I viewed Jupiter near 46 arcseconds on the night of 11 and early morning 12th of June, I did not see Jupiter as a disk. My two telescopes did however 🙂

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