As Jupiter reaches its closest point to Earth for the year, observers are reporting that its famous Great Red Spot is rapidly shrinking.The giant planet reaches opposition – when it’s opposite the Sun in the sky – on 10 June 2019, and is actually closest on 12 June. This is the time when observers get their best view of the planet. However, this year it’s very low in the sky as seen from the UK, down close to the horizon. As a result, the turbulence of our own atmosphere makes a mess of the image, so we get a rather blurry view. Jupiter is due south at about 1 am, so is a feature of the late night sky, though if you don’t have a good southern horizon you might not notice it.
The Great Red Spot has been a major feature of the planet since it suddenly appeared in its present form in 1878. It is absent from drawings made in previous years. At that time it was enormous, some 40,000 km in extent, and throughout the 20th century it dominated the planet, though its colour changed noticeably from strongly brick-red to a paler pink, sometimes being hardly noticeable.
Since 2000 it has been shrinking more rapidly, and observations this year show that its rate of shrinkage has increased. Bits seems to be breaking off and becoming absorbed into Jupiter’s atmosphere, as seen on a remarkable video made by Italian observer Marco Vedovato, which you can view here, along with graphs of the shrinkage. Also look at our Planetary Section report for more details.
So take a look if you have a telescope – no-one knows what will happen next. Fortunately the Spot is now more strongly coloured than it has been in the past, so it should be visible with a telescope as small as 100 mm aperture or less under good conditions. Jupiter is best seen from about 11 pm to 3.30 am BST. You can get predictions for the times when the Great Red Spot will be on the disc using www.calsky.com – go to Planets, Jupiter then Apparent View/Data to see a graphical output of the predicted appearance of the planet at any time, or Great Red Spot to find when it will be centrally placed on the planet. It will be central on the disc at the following times before 1 am BST, and you’ll need to look within an hour of that time to see the spot reasonably well:
11 June 22:27
14 June 00:05
18 June 23:12
21 June 00:51
23 June 22:20