StarDate

Vega is already the fifth-brightest star in the night sky, and the second-brightest north of the celestial equator. But it’s going to get even brighter. It’s moving toward our solar system. And when it’s at its closest, it’ll appear almost four times brighter than it is now.

Vega is an impressive star. It’s more than twice the size and mass of the Sun, and about 40 times brighter. And it’s also a close neighbor — just 25 light-years away. That’s the main reason it looks so bright.

Like all the stars we see in the night sky, though, Vega is on the move. Right now, Vega and the Sun are moving roughly toward each other, at about 30,000 miles per hour. Considering the distance between them, that’s not very fast. Over the millennia, though, the change will add up. Vega will make its closest approach to the solar system in about 265,000 years, when it’ll be about half as far away as it is now.

Cutting the distance in half will make the star look four times brighter than it does now — as bright as Sirius, the night sky’s current leader.

During that interval, Vega will serve as the North Star 10 times. Earth wobbles on its axis, so its north pole points toward different stars at different times. It points to Vega every 26,000 years. The star’s next appearance as the North Star will be in about 12,000 years.

For now, look for Vega high in the sky as night falls, in Lyra. You just can’t miss it.

Script by Damond Benningfield

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A bright star crowns the sky this evening. Vega is the leading light of Lyra, the harp. It’s the fifth-brightest star in the entire night sky, so it’s hard to miss.

There’s a lot going on at Vega. The star itself is dynamic, and it’s encircled by a wide ring of dust — the likely aftermath of a big collision.

Vega is about twice the size and mass of the Sun. Perhaps because of its youth, though, the star spins more than a hundred times faster than the Sun does at the equator. That’s almost fast enough to rip the star apart. Instead, though, it causes Vega to bulge outward — it’s about 20 percent wider through the equator than through the poles.

Detailed observations have suggested that Vega’s brightness varies over a period of years — perhaps by a few percent. Different studies have come up with different results, though, so the matter isn’t settled.

Astronomers are sure that Vega is encircled by a wide disk of dust. It extends tens of billions of miles away from the star. Much of the dust probably resulted from the collision of two big asteroids or comets. The initial impact created a cloud of dust, plus several big fragments of the original bodies. They then had their own impacts, spewing more dust into space.

Vega could have planets as well as the dust. So far, there’s no solid evidence of any. But astronomers continue the search — looking for more activity in this busy star system.

More about Vega tomorrow.

Script by Damond Benningfield

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If you look toward Lyra, the harp, on a dark summer night, you might think you’re seeing double. And if you look with a telescope, you’ll see double double. That’s because one of the constellation’s stars is known as the Double Double. It consists of two pairs of stars that appear to be moving through the galaxy together.

The pairs are known as Epsilon 1 and Epsilon 2 Lyrae. At nightfall, they stand close to the lower left of Vega, one of summer’s brightest stars, which is high in the east. Those with good eyesight can just separate the two pairs, while a telescope splits each pair into its individual stars. Epsilon 2 is about twice as bright as Epsilon 1.

The stars of Epsilon 2 are so far apart that it takes them about 725 years to orbit each other. One of its stars appears to have a companion of its own. It’s so close in, though, that not even the biggest telescopes can spot it.

The stars of Epsilon 1 are a little farther apart. And their combined mass is a little less than those of Epsilon 2. So it takes them more than a thousand years to orbit each other.

The two systems are separated by a trillion miles or more. So it takes hundreds of thousands of years for the two pairs to complete a single orbit around each other. Astronomers need to see a good bit of an orbit to confirm that two objects are bound together. So we can’t be positive that the Double Double really is a single family, moving through the galaxy as one.

Script by Damond Benningfield

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Stars pass by each other without much effect. That’s because the average distance between stars is millions or billions of times the size of the stars themselves.

But it’s a different story with galaxies. These massive “cities” of stars are so big that there’s not a lot of space between them. As a result, they frequently sideswipe one another, or even collide head-on.

Many examples of interacting galaxies are found in the Hercules Cluster. It’s a collection of a couple of hundred galaxies that’s about 500 million light-years away. The cluster is in the constellation Hercules, which is high overhead at nightfall.

The cluster is a bit unusual.

Most clusters in the nearby universe contain many big, dull galaxies known as ellipticals. These galaxies are dominated by old, faint stars. And they have little gas and dust for giving birth to new stars, so not much happens in them.

The Hercules Cluster, though, is dominated by spiral galaxies, which are similar to our own Milky Way. These galaxies have many hot, young stars, plus the raw material for many new stars. As a result, they’re bright and vigorous.

Many of the cluster’s galaxies are interacting. Groups of two or three galaxies are passing so close together that their gravity rips out big ribbons of stars, and causes clouds of gas and dust to collapse to create more stars. So even though the Hercules Cluster isn’t all that big, it’s one of the busiest clusters around.

Script by Damond Benningfield

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Astronomers are following the trail to Planet Nine. The trail is marked by chunks of ice and rock far from the Sun. The way their orbits line up suggests they’re being “herded” by the gravity of a planet. It would be tens of billions of miles from the Sun, and up to about 10 times as massive as Earth.

Astronomers have used a similar technique to track down other worlds — or at least try to.

The best-known success story came in 1846, with the discovery of Neptune, the eighth planet from the Sun. Some odd things about the orbit of Uranus, the seventh planet, hinted that a more-distant world was tugging at it. Two astronomers predicted where that world might be found — and they were right.

Flush with that success, astronomers tried to find another planet. They’d plotted some odd things about the orbit of Mercury, the Sun’s closest planet — suggesting there might be a planet even closer to the Sun. They called it Vulcan, and looked for it for decades. But it’s just not there. Instead, Mercury’s orbit is being dragged by a “warp” in space caused by the Sun’s gravity.

And a couple of decades ago, a team looked at the orbits of a class of comets. Many of the comets looked like they were lined up by the gravity of a giant planet or a “failed star” far from the Sun. So far, though, no one has seen such a body.

So the search for Planet Nine continues — a world that might be herding smaller bodies in the outer solar system.

Script by Damond Benningfield

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The issue of Life magazine published 75 years ago today featured an amazing story. German scientists, it said, had been working on placing a giant mirror in space. The mirror would reflect the Sun’s rays to the surface below — starting wide-spread fires or incinerating cities.

The project never got far, of course. But by the time the article appeared, some of the Germans who’d worked on such high-tech projects had been captured by the Americans.

Many of them were brought to the U.S. under a project that was authorized just days before the Life magazine issue appeared. It first was known at Operation Overcast, but later was changed to Operation Paperclip.

In all, about 1600 German scientists, engineers, and technicians were brought to the U.S. They’d worked on rockets and other weapons. Many were directly involved in war-time atrocities. But American intelligence agencies hushed up their histories. They reasoned that it was more important to have the knowledge of the German scientists — and to keep it out of the hands of the Soviets.

The most famous group was headed by Wernher von Braun, who led development of the V-2 rocket — a weapon built with slave labor. He and his team spent five years working on rockets in West Texas and New Mexico.

Later, the team moved to Alabama. There, it built the rocket that launched America’s first satellite, as well as the giant Saturn V — the rocket that sent astronauts to the Moon.

Script by Damond Benningfield

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The young solar system was a dangerous place for planets. Several of today’s worlds got blasted by other planets. Earth was hit by a planet as big as Mars, giving birth to the Moon. And Uranus was hit by an even bigger planet, knocking it over on its side.

Mercury probably got hit, too. The Sun’s closest planet is also the smallest. Yet it’s quite heavy. It has a big, dense iron core wrapped in fairly thin layers of rock. That suggests that something big hit the planet when it was quite young, blasting away most of its outer layers.

One problem with that idea is that most models say the debris should fall back onto Mercury within a million years or so. Yet that clearly didn’t happen. And a recent study suggested a possible reason why.

The young Sun was more magnetically active than it is today. That produced a faster, thicker “wind” of charged particles.

If Mercury got hit during the Sun’s first 10 million years, the wind probably blew the debris away from the Sun. In fact, some of that material could have been incorporated into the young Earth. If the impact came a little later, though, then the debris would have been pulled into the Sun. Either way, the young planet was stripped of its outer layers — leaving it small but heavy.

And Mercury is just peeking into view in the dawn sky. It looks like a moderately bright star quite low in the east-northeast as twilight paints the sky. It’s well to the lower left of Venus, the “morning star.”

Script by Damond Benningfield

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A comet that defied the odds is in view in the evening sky. It’s fairly bright, although you need binoculars to get the best view.

Comet C/2020 F3 NeoWise was discovered on March 27th by a NASA spacecraft. The comet passed closest to the Sun on July 3rd — about 27 million miles. Many comets disintegrate during such close passes. In fact, that’s what happened to two comets that were forecast to become naked-eye objects earlier this year. But NeoWise survived.

The Sun’s heat vaporized some of the ice at the surface of the comet. The gas boiled away into space. That freed small grains of rock and dirt, which flew away as well. The Sun’s light and magnetic field sculpt the dust into a long, glowing tail, and the gas into a shorter tail.

The comet’s closest approach to Earth is about 64 million miles, so it’s no threat to our planet.

NeoWise will be on display in the second half of July and into August. It’ll be in the northwest as darkness falls, passing below and then beside the Big Dipper. It may be visible to the unaided eye, but you’ll probably need binoculars to see its tail. The view will be better from the northern states, where the comet will pass a little higher across the sky and remain in view most of the night.

NeoWise will disappear from sight in a few weeks as it moves away from the Sun. And you won’t get another chance to see it — it won’t return to the inner solar system for almost 6800 years.

Script by Damond Benningfield

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Saturn continues to shine at its best. The planet is low in the southeast at nightfall, to the lower left of brilliant Jupiter. Saturn looks like a bright golden star, and it’s in view all night.

Saturn looks so bright in part because of its rings. They’re tilted toward Earth right now, so they reflect more sunlight our way than the planet itself.

It’s easy to think of the rings as a single piece — like a spinning DVD or phonograph record. That’s far from the case, though. The rings consist of trillions of small bits of ice and rock. Each particle orbits the planet like a tiny moon.

That means the particles in different rings move at different speeds. The bits that are closer to Saturn move faster than those that are farther away.

The inner edge of the closest major ring, the C ring, is about 4,000 miles above the planet’s clouds. At that distance, a ring particle moves at about 53,000 miles per hour. That’s three times faster than the International Space Station orbits Earth. But a particle at the outer edge of the outermost major ring, the A ring, is about 50,000 miles from Saturn. At that distance, it orbits at 36,000 miles per hour.

So if you could paint a big red stripe across the top of the rings, from inner edge to outer edge, then watch what happened, the stripe wouldn’t last for long. The particles would quickly form an ever-tightening spiral — tiny moons spinning around a giant planet.

Script by Damond Benningfield

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Every planet orbits the Sun in the same direction. If you viewed the solar system from above the Sun’s north pole, they’d all be moving counterclockwise.

But what we see doesn’t always reflect that. Right now, for example, the giant planets Jupiter and Saturn are moving backwards — a motion known as retrograde. That doesn’t mean the planets have reversed direction, though. Instead, it’s caused by Earth’s motion relative to the two planets.

Earth is closer to the Sun, so it moves faster in its orbit. Once every year or so, it passes Jupiter and Saturn. As it does so, they appear to move in reverse for a while. Instead of their usual eastward motion against the background of stars, they move westward for a while.

Think of driving down the highway. The cars that are well ahead of you appear to be moving forward against the background of buildings and trees. If you zoom past them, though, they briefly appear to move backward against the background. Then, as you pull away, they appear to resume their normal forward motion.

Saturn began the year in Capricornus. As Earth began overtaking the planet, though, it moved in reverse, into Sagittarius, where it is now. It’ll soon resume its forward motion, though, and be back in Capricornus in December.

Jupiter and Saturn are in the southeast as night falls. Jupiter looks like a brilliant star, with not-as-bright Saturn to its lower left. They’re in view all night long.

More tomorrow.

Script by Damond Benningfield

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