This month promises planetary observers their best views of Jupiter and Saturn for the year as both worlds reach opposition within a week of one another. Earth first moves directly between Jupiter and the Sun on July 14, then between Saturn and the Sun on the 20th. Come opposition, the gas giants will be at their closest and brightest for the year. But opposition is more than a moment in time; it is a chance to seek out those brief windows when the atmosphere allows us to see fine details — the most these planets can display each year.
NASA’s New Horizons spacecraft looked back at Pluto after its closest approach on July 14, 2015, and snapped this photo of the planet’s hazy, layered atmosphere. On the sunlit side (right), the smooth expanse of Sputnik Planum is flanked to the west (above, in this orientation) by rugged mountains up to 3,500 meters high.
NASA / JHUAPL /APL / SRI
Jupiter’s Equatorial Zone normally appears white due to extensive high cloud cover. Every six or seven years (though not always), the zone’s high ammonia clouds clear out, changing the region’s color to ochre. The disturbance usually lasts between 12 and 18 months, allowing telescopic observers a rare chance to see details deeper in the planet’s atmosphere, normally hidden by those high clouds. We are currently in that window of opportunity, as the next clearing has been predicted to occur between 2019 and 2021.
To get the most out of observing Jupiter at opposition, concentrate on the midnight hour, when the planet appears highest in the sky and its detail is most rewarding. And no planet shows more detail than Jupiter, especially when observing with powers up to 75x per inch of aperture. This July, Jupiter’s disk measures 48″ across, only 2.1″ less than its maximum apparent size. Fine details then will be near their best.
Thank You to Stephen James O’Meara in ASTONOMY for the majority of content in this Post.
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