With Jupiter we are really beginning to move into the outer solar system. Jupiter is a long way from the Earth, even at opposition (~390 million miles/626 million km), but it is so big (11 times the diameter of the Earth) that is the largest planet you will observe or image with a telescope. Small planets such as Mars are best viewed within a few weeks of their opposition, but Jupiter is worth a look as long as you can see it in the night or morning sky.
Jupiter has 53 confirmed satellites/moons (as many as 16 more are awaiting confirmation), but only the largest four, first observed by Galileo over 400 years ago, are routinely visible in amateur telescopes.
When you look at Jupiter, you are not seeing the solid surface of the planet. Instead, you are looking at the the very high tops of clouds that essentially block any view of what lies beneath. However, those clouds are highly varied and dynamic and well-worth observing. What you are seeing is a grand case of weather, a global heat machine unrivaled in the solar system.The modest heat from the sun combines with the very significant internal heat of the planet itself to keep the atmosphere continuous churning, while the very fast rotational speed (a day on Jupiter is only about ten hours long) adds to the mix of forces acting on the atmosphere. The broad latitudinal bands of clouds owe their color differences to the mix of gasses and although the bands are usually somewhat stable, even they can change with time. The largest single storm on the planet, the Great Red Spot, is a hurricane-like weather system the size of the Earth which has persisted (at varying intensity) for several centuries. Click on Jupiter on the [NASA Solar System Exploration] page for much more information on this giant of the Solar System.
Best of the 2017 Apparition
This image was obtained one day after opposition in 2017 and on the actual day of closest approach to the Earth. The Long-awaited OMC200 telescope was still weeks from delivery and this image was obtained using a 180 mm Maksutov/Cassegrain (f/17) marketed by [Orion Telescopes and Binoculars] in California. If you are looking for an excellent serious starter instrument for Lunar and Planetary imaging, you cannot get a better price/performance ratio. This image clearly shows a great deal of cloud detail, the Great Red Spot, and Europa and Ganymede, two of the Galilean satellites. The diameter of Ganymede is approximately 1.7 times larger than that of Europa – a difference clearly evident in the image.
“First-light” image of Jupiter following the installation of the Orion Optics UK OMC200 instrument. The difference in relative size of the image disc is a consequence of the larger focal ratio of the OMC200 (f/20) compared to that of the 180 mm Maksutov (f/17).
2018 Jupiter Apparition
Jupiter will reach opposition with the Earth (essentially its closest approach for the year) on 09 May 2018. Jupiter is large enough that it should provide excellent views for several months on either side of opposition. As new images are acquired, starting this Spring, they will be posted here. Although it would be nice if all of the images were of very high quality, in the real world they will range from a very few fine images to a larger number that are distinctly mediocre, primarily due to variations in “seeing” on the various dates.
For the first half of the apparition (from March until opposition at my site), I posted a total of 12 images, quite a few of which were of marginal quality. Given that opposition occurred early this morning, it is time to boil the dozen images down to the top three:
This is an unusual image involving the moon Io. When a moon orbits in front of the planetary disc it is called a transit and here Io is caught starting such a transit across the face of the planet. At some angles, the shadow of a moon can be seen moving across the face of the planet, even when the moon is not in transit. These are called “shadow transits”. Here we also have the shadow of Io, so we have Io in transit and a shadow transit!