Planets are making the news: Saturn’s rings are bigger than previously thought. Pluto is about to be visited for the first time. The Messenger spacecraft crashed into Mercury. But thus far, these have been treats for our minds. We weren’t there to see it.
So let’s change that. The two brightest stars in the night sky – Jupiter and Venus, which of course are planets, not stars – are now coming together in grand fashion. And the Crescent Moon is joining them to form a dazzling triangle.
The next clear evening, take a look between 9 and 10 p.m. in the fading twilight. Venus is the very brightest and Jupiter’s the second-brightest “star” in the sky. Jupiter is higher and left of Venus. On Saturday night, we get the year’s best conjunction. A gorgeous triangle stands there in the west in fading twilight and right into the first hours of full darkness. The three most brilliant objects of the night all meet together.
This is a don’t-miss event. If it’s clear on Saturday evening, be sure to take a look. If it’s cloudy, peek the next night, even though the Moon will have shifted to the left and no longer forms the tight triangle.
Each evening you’ll see that Venus has shifted closer to Jupiter. During the final day of June and first evening of July, they’ll be almost touching: another don’t-miss event.
This all happens against the faint stars of the constellation Cancer, which looks like a crab only to those with vivid imaginations. But Leo’s blue star Regulus is just to the left of the conjunction, though not as luminous as the three protagonists.
It would be amazing if the Sun went out all of a sudden while you were watching this trio in the twilight. First Venus would vanish. Then, a split second later, we’d lose the Moon and the colors of dusk. But Jupiter would still linger for another 90 minutes, as “old” sunlight continues on, then reflects off its enormous gassy surface and back to our eyes.
If you’re pointing out these easy planets this weekend, it’s good to have a dramatic fact about each on hand, as gee-whiz material. For Venus, it’s the fact that of all the objects in the known universe, this planet comes closest to not spinning at all. It rotates only every 243 days – so slowly that a person walking briskly along the Equator could keep night from ever falling.
For Jupiter, maybe it’s best to puncture the “almost a star” or “failed star” myth that one hears so often. Even if Jupiter had 50 times more mass than it does, pressures at its core wouldn’t reach the point where nuclear fusion could ever begin. It’s a planet, period, albeit so massive – 318 times heavier than Earth – that all the others combined and doubled wouldn’t equal its weight alone.
I also like to visualize Jupiter’s ultrastrong magnetic field that traps and holds lethal radiation belts. This magnetosphere is the largest structure in the solar system. If magnetism were visible to the naked eye, it would appear larger than the Sun, even though it’s five times farther away from us. Its sizzling radiation provides a barrier that discourages any potential visitors.
We can’t touch. But this weekend we sure can look.
Want to know more? To read Bob’s previous “Night Sky” columns, visit our Almanac Weekly website at HudsonValleyAlmanacWeekly.com.