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Venus, Jupiter, crescent moon meeting up this weekend

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Look to the west after sunset Sunday night and, unless clouds impede the view, you’ll see three worlds.

One is the moon, a thin crescent, upturned like a smiley face. The second is Jupiter, a gas giant reduced by distance to a bright dot. It’ll be just to the left of the lunar smile, like a beauty mark.

Above the moon and Jupiter, about a fist’s distance away on an outstretched arm, will be Venus, beaming like a headlight.

The last four weeks or so have been a spectacular time for stargazers, or, more precisely, planet-watchers. Venus and Jupiter have had a conjunction, and on March 13 passed so close to each other in the night sky that they could have exchanged business cards. Throw in the moon on Sunday and Monday nights and it’s a must-look situation.

“When you get a configuration like this, people who don’t normally look up above the horizon find that their eyeballs are being hijacked,” said Alan MacRobert, an amateur astronomer and senior editor at Sky & Telescope magazine.

More news is on the horizon: On June 5, Venus will transit the sun, the last such transit until 2117. With a safe solar filter, the tiny black dot of Venus will be visible as it gradually moves across the sun’s face.

Meanwhile, the sun is acting up. We’re building to a solar maximum, which means lots of solar flares, coronal mass ejections, northern lights and the potential for damage to satellites or the power grid.

And by the way, there’s a new theory afoot that the Titanic was sunk by an iceberg sent into the shipping lanes by tides associated with a rare arrangement of the sun, Earth and moon.

Dare it be said: The solar system is trending.

What’s unfolding Sunday and Monday nights is a reprise of what happened Feb. 25 and 26, when the crescent moon slipped past Jupiter and Venus. The two planets have a conjunction like this about once every 24 years, said Geoff Chester, spokesman for the U.S. Naval Observatory.

This is what’s known as an evening apparition of Venus (it can be a morning star or an evening star), and it has been particularly sublime because the planet is relatively high in the sky. The second rock from the sun is near its greatest “elongation” — as far as it ever gets from the sun as seen from Earth — and so it’s up in the sky for a long time before it sets.

It’s also preposterously brilliant. Its magnitude is almost at the maximum for Venus — minus 4.4. (The lower the magnitude, the brighter the object.) On a moonless night in a dark place, you can see your shadow in Venusian light, Chester said.

“The circumstances for this evening apparition are about as good as they get,” Chester said. “Then you throw Jupiter into the mix, which is usually the second brightest planet, then you’ve got a couple months when the moon is playing footsie with them. And that’s what makes it particularly interesting.”

Those unfamiliar with such things should be warned that planet-watching is a subtle pleasure, enhanced by the right attitude. Not much actually happens. The planets don’t zoom around. Nothing collides or explodes. There are no cameo appearances by comets. The moon and planets will drop below the horizon by late evening and some people may feel the need to find an after-party.

The action in the sky, gentle though it may be, incited among ancient people some of the first stirrings of scientific inquiry. They didn’t know what a planet was, fundamentally. “Planets” comes from an ancient Greek term meaning “wandering star,” and thus describes the behavior of the objects rather than their nature.

In ancient times, the heavens clearly revolved around the Earth, wheeling nightly on an axis pointed in the northern hemisphere toward the star Polaris. But anomalies among the planets required explanation and investigation. Mars, for example, had the perplexing habit of migrating east across the firmament and then reversing direction for a couple of months before reversing yet again.

Not until the 1500s did astronomers, led by Copernicus, put together a fairly accurate model of the solar system (minus planets yet to be discovered), with the sun at the center rather than the Earth. Only then did it become clear that the retrograde motion of Mars is due to the Earth passing it on the inside lane of the orbital speedway.

The irony of the Information Age is that people have forgotten so much of what their forebears knew. This is an era in which people talk of TMI — too much information — even as they couldn’t name a single star in the sky. Many people would no more learn the names of the stars than figure out how to boil lye to make soap.

“All this stuff was common knowledge among ancient people. Even people just a few hundred years ago, your average farmer would be keeping a very close eye on the season, they’d be keeping a very close eye on the moons,” Chester said. And yes, “moons,” plural. The moons had names. The last full moon, for example, was the Full Worm Moon, because it’s the time of year when the worms start moving around in the soil, Chester said.

Owen Gingerich, a professor emeritus of astronomy at the Harvard-Smithsonian Center for Astrophysics, said that the spectacle in the western sky is so beguiling that “even our graduate students are aware of what’s happening.”

That’s an inside joke because graduate students in astronomy do all their work now on computers and with equations and don’t spend a lot of time acting like Galileo and looking through telescopes.

In certain respects, the planets are old news. The cutting edge in astronomy is the search for extrasolar planets — which orbit distant stars — and the investigation of the mysterious dark matter that is indirectly detected through study of the motion of galaxies. Cosmologists hope to understand the “dark energy” that is causing an acceleration of the expansion of the universe.

But the nearby planets still have surprises. A probe orbiting Mercury discovered evidence of ice at the poles of the little planet that is seemingly fried by the sun.

And this past week, scientists announced that they’d come up with a better measurement of the width of the sun, achieved by studying two transits of Mercury. The sun is 865,374 miles in diameter, plus or minus 40 miles.

Now, about the Titanic. The ship hit an iceberg late on the evening of April 14, 1912. Where did the iceberg come from? The authors of an article in the latest issue of Sky & Telescope contend that an unusual abundance of icebergs in the shipping lanes that year may have had an astronomical explanation.

According to Donald Olson, a professor at Texas State University and the article’s co-author, on Jan. 4, 1912, the moon was at its closest approach to the Earth even as the Earth was at its closest approach to the sun (the orbits are not perfectly circular but rather are elliptical). This created powerful tides noted around the world.

Icebergs calved in Greenland would normally have grounded in shallow water along the coasts of Labrador and Newfoundland, Olson said. But those unusually high tides would have dislodged the icebergs, and sent them on a roughly three-month journey down to the shipping lanes, where one of them greeted the great ocean liner. That’s the hypothesis.

“We can’t prove it conclusively because we don’t know where the Titanic iceberg was precisely in January 1912,” he said.

But his larger point is that astronomy can provide information about historical or cultural events. Olson has also studied Van Gogh’s painting “Road With Cypress and Star.” The painting shows a crescent moon close in the sky to a bright star. Look closely, and there’s another star, much smaller. Olson’s research suggests that the bright star was Venus and the smaller one Mercury.

There’s actually a fourth world in that picture, one that will also be on view in the coming nights as the moon, Venus and Jupiter dance in the western sky. The fourth world is obvious yet subtle: It’s the one we’re standing on, the one that, in Van Gogh’s painting, grows a magnificent cypress tree.

You can even see the Earth in the sky, sort of. In a good location with a dark sky and little light pollution from the city, you’ll see the “dark” part of the crescent moon illuminated in an ashen light known as earthshine. That’s sunlight that has bounced off the Earth (which would be nearly a “full Earth” if seen by a moon walker) to light up the night on the surface of the moon.

Olson said he and his students will be looking at this weekend’s grouping of celestial objects through the clear air of central Texas. He expects it to be spectacular and memorable.

And also inspiring — perhaps for the next Van Gogh.

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