Join the Summer Twilight Dance

August opens with a bang with a total solar eclipse on the 1st. But there’s a whimper too: you have to be in China, Mongolia, arctic Canada, Greenland or Siberia to see it. In our hemisphere we don’t get to see as much as a sliver, and will have to make do with webcasts. The same is true for the partial lunar eclipse on the 16th, visible from parts of every continent ... except North America.

Saturn is low in the evening twilight sky, and starting about a week into August, it takes part in a dance with Venus and Mercury. First Venus approaches, climbing upward in the sky to meet almost Saturn on the night of the 12th, when the pair will be separated by only about half a degree. They slip past each other the next morning (ambitious observers might want to try for them in the morning – they’ll be only a fifth of a degree apart). By the night of the 13th they’re back to the half-degree separation of the previous night, but with their positions reversed.

Meanwhile, while Venus and Saturn are dancing, Mercury waits in the wings. Having followed Venus in its rise out of the twilight glare, it’s a bit under three degrees away while its larger and brighter cohorts make their close pass. But Mercury gets a turn with Saturn too: on the night of the 15th it passes Saturn with a separation of about three-quarters of a degree, then pulls nearly even with Venus by the 19th. The two promenade for about a week from Leo into Virgo, staying about a degree apart, until by the month’s end Mercury finally begins to pull slowly away. (But keep watching as September opens: the pair will be joined by a slim crescent moon on September 1.)

Even aside from its nice dance with Saturn and Venus, this is the best evening look at Mercury we’ll get all year, lasting through at least the first half of September.

Mars, too, is in the picture: all this time it’s been hovering in eastern Virgo, waiting for its turn to dance with Venus and Mercury (a turn that will come in early September, starting on the first when all three planets plus a slim crescent moon come together). Mars is quite distant and small now, so it will be hard to see much detail on the planet, but it can still give us some lovely low-power and naked eye views.

While all this twilight dancing is going on, of course the real shallow show is Jupiter, a month past opposition and hanging bright in the southern sky all evening. It won’t ever get high during this pass – this month it’s just 30° up at its highest – but you can still see plenty of detail in the swirls of its bands, as well as watch another dance, that of its four bright Galilean moons.

Neptune reaches opposition on the 15th of August and is available all month for observers wanting an outer solar system fix. You probably won’t want to go after it on the 15th, with the moon one day short of full and hanging only a few degrees away, but by later in the month its small blue disk should make a fine target. Uranus is not so easily placed: it lags a couple of hours behind Neptune in Aquarius, and doesn’t transit until 3am, though its larger, brighter green disk should be findable even before it’s high in the sky. Pluto is in northwestern Scorpius, in the heart of the Milky Way ... you’ll have plenty of field stars to compare with, but also plenty of field stars to confuse with Pluto! But if you get frustrated, at least there are plenty other objects to look at during your Pluto hunt.