The mighty planet Jupiter is at its best of the year, an easy and brilliant sight, for these next few weeks. Jupiter also spends one night, especially grand, near June’s full moon.
This is good news for skywatchers. But we also have the very rare case of some bad news in the column today. One potentially bad thing is that we just might be seeing the death — after hundreds or even millions of years — of the second-most spectacular individual feature on a planet in our solar system.
Jupiter at its yearly best: Jupiter is normally the brightest planet except for Venus. But Venus can never be observed all night long or high in a midnight sky. This month, Venus is rising so soon before the sun that it can hardly be glimpsed, very low in bright morning twilight. In contrast, these next two weeks are the ones of 2019 when Jupiter rises around sunset, is highest in the middle of the night, and sets around sunrise. This positioning of Jupiter in relation to the sun and Earth is called “opposition” (opposite from the Sun in our sky). And it is also the positioning where we get a line-up in space of Sun-Earth-Jupiter, placing Jupiter at its closest to us of the whole year.
Closest to us means Jupiter appears its biggest in telescopes and its brightest in our sky. Even if you are a novice skywatcher, you should have no trouble finding Jupiter on these June nights. As darkness starts to fall, Jupiter is still low in the southeast. But later in the night it hangs like a glowing beacon in the south, outshining any other point of light in the sky.
Jupiter’s nearness to Antares, Saturn and the full moon: You may notice a star that is bright — though far dimmer than Jupiter — a bit more than one width of your fist at arm’s length to the right of Jupiter. This is the star Antares (an-TAIR-eez), which marks the heart of Scorpius the Scorpion and has a campfire-colored (orange-gold) light. Note that yellow-white Jupiter, being a planet and having a sizable disk in telescopes, shines with a steady light, compared to the twinkling of stars.
Another bright object is about three fist-widths at arm’s length to the lower left of Jupiter around midnight. This is the planet Saturn, which will have a truly close pairing with Jupiter next year.
The most impressive and close pairing of Jupiter this month is the one it has with the full moon on the night of Sunday, June 16 into Monday, June 17.
Wonders of Jupiter in the telescope: Even a very small telescope can show you up to four points of light very near Jupiter — Jupiter’s four “Galilean moons” (discovered by Galileo), giant moons called Io, Europa, Ganymede and Callisto. In a medium-size amateur telescope you can see at least the darkest horizontal “belts” in the atmosphere of Jupiter. We can never see through Jupiter’s vast atmosphere to any surface, but there are features other than the belts we can detect in the planet’s clouds. The most famous of these features is the GRS — the Great Red Spot.
Is the Great Red Spot unraveling? The Great Red Spot is somewhat like a storm in the atmosphere of Jupiter, with winds of about 300 mph around its periphery. But this “storm” has been visible since the making of the first good telescopes — more than 300 years ago — and might actually be thousands or even millions of years old. Far more amazing is the fact that the eye-shaped Great Red Spot was about three times wider than the planet Earth — until it started shrinking in recent years. And now, in just the past few weeks, vast arcs of reddish gas have been detaching from the Great Red Spot — bringing its size down to about that of Earth. Will this process continue until the GRS is no more? For a photographic update, check out the planets section of “This Week’s Sky at a Glance” at skyandtelescope.com.
Next column: The Greatest Danger Ever to Stargazing.