StarDate

You won’t find a much quieter place in the solar system than the far side of the Moon. The Moon doesn’t produce any radio noise, and it blocks radio signals from Earth. That could make it a good site for radio telescopes. But it’ll take a lot of work to build them — and to keep the farside nice and quiet.

Radio telescopes are needed to study the Dark Ages — the period in the early universe when the first stars and galaxies were taking shape. The energy from that era is visible mainly at radio wavelengths. But Earth produces huge amounts of interference — from cell phones to orbiting satellites to microwave ovens. That overwhelms the whispers of the universe.

So astronomers are drafting plans for radio telescopes on the Moon. But the farside is about to get a lot louder. New orbiters and landers will broadcast from there, making it much less favorable for astronomy.

Scientists are trying to get international treaties to limit farside broadcasts. They want to set up a “quiet zone” where no signals at scientifically interesting wavelengths would be allowed. No one knows yet if they’ll succeed at keeping the far side of the Moon quiet.

The Moon is just a couple of days past full tonight, so it’s nice and bright. The star Aldebaran, the eye of the bull, rises close to its lower right, and will be to the lower left of the Moon at dawn.

More about the Moon, Aldebaran, and another bright companion tomorrow.

Script by Damond Benningfield

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Thousands of planets have been found in other star systems. They’re all so far away, though, that most are no more than squiggly lines on a computer screen. Yet scientists are slowly teasing the details out of the squiggles.

To understand how difficult the problem is, consider that there’s still a lot to learn about the planets of our own solar system.

One mystery, for example, is why the planet Uranus radiates very little energy into space.

The four outermost planets — Jupiter, Saturn, Uranus, and Neptune — are all giants. They’re so massive that gravity tightly squeezes their insides, producing heat that radiates into space. In fact, three of the four emit a lot more energy than they receive from the Sun. The exception is Uranus, where the energy is roughly balanced — and scientists are trying to figure out why.

Another mystery is the planet’s climate. Uranus lies on its side, with each pole receiving 42 years of sunlight followed by 42 years of darkness. Astronomers are watching how the climate changes with the seasons — one of the mysteries of a world in our own neighborhood.

Uranus is passing closest to Earth about now, so it’s biggest and brightest for the year. Even so, you need binoculars to spot it — especially tonight. It’s low in the east as night falls, close to the upper right of the full Moon.

We’ll talk about the Moon and a much brighter companion tomorrow.

Script by Damond Benningfield

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For the third November in a row, Earth, Moon, and Sun will achieve syzygy — a perfect alignment. The Moon will pass through Earth’s shadow, creating a total lunar eclipse. All or most of the eclipse will be visible from the entire United States.

“Syzygy” comes from a Greek word that means a union — like when two horses or oxen are yoked side by side. And several times each year, Earth, Moon, and Sun are locked in a precise alignment — a “union” that results in either a lunar or solar eclipse.

This eclipse gets underway shortly after 3 a.m. Central Time. That’s when the edge of the Moon begins to enter Earth’s dark inner shadow, known as the umbra. That begins a partial eclipse, with the Moon partially in the shadow and partially bathed in sunlight.

The Moon will be fully immersed in the shadow — beginning the total eclipse — a little more than an hour later. Totality will last for almost an hour and a half. After that, the eclipse will become partial again as the Moon begins to leave the shadow behind. It ends a few minutes before 7.

Skywatchers west of a line from the southern tip of Texas to the western tip of Lake Superior — including all of Alaska and Hawaii — will see the entire total eclipse and most of the partial. Most of those to the east of that line will see all of the total eclipse, but the Moon will set during the partial phase — the end of a perfect alignment.

Script by Damond Benningfield

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It’s eclipse season! There was a partial solar eclipse a couple of weeks ago. And on Monday night, we’ll have a total lunar eclipse. That one will be visible across all of the United States.

It’s not a coincidence that the eclipses are taking place two weeks apart. In fact, eclipses always come in pairs — unless they come in threes — and always two weeks apart.

That’s because eclipses require precise alignments of Earth, Sun, and the new or full Moon. But the Moon’s orbit around Earth is tilted a bit compared to Earth’s orbit around the Sun. So most months, when the new or full Moon crosses Earth’s orbit it’s either above or below the point where it would create an eclipse.

When the Moon crosses Earth’s orbit at just the right time, though, it brings Moon, Earth, and Sun into alignment. In fact, the alignment happens twice, about two weeks apart — an eclipse season. One alignment creates a solar eclipse, while the other creates a lunar eclipse. They can happen in either order. And the cycle repeats roughly six months later.

The total length of an eclipse season is about five weeks. So if there’s an eclipse early in that period, there can be a third eclipse at its end — usually two poor eclipses flanking one good one. And if the year’s first eclipse season begins in early January, there can be three of them during the year — producing as many as seven eclipses — which will happen in 2038.

More about the upcoming eclipse tomorrow.

Script by Damond Benningfield

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Black swifts love moonlight — the brighter the better. A recent study found that the birds climbed to their highest altitudes when the Moon was full. But when the moonlight was blocked by an eclipse, they dropped in a hurry.

Researchers attached small trackers to a group of black swifts in Colorado. They then tracked the birds during their 4,000-mile migration to the Amazon Basin in Brazil. It took about eight months for the small birds to make the trip — with more than 99 percent of their time spent in the air.

During the day, and on nights with little moonlight, the birds stayed at altitudes of a few hundred to a few thousand feet. When the Moon was full though, they soared to two or three miles — possibly to grab high-flying insects.

On the night of January 20th, 2019, the birds were flying when the Moon was eclipsed. And they didn’t seem to like it. They quickly dropped thousands of feet. And when the eclipse ended, they climbed higher again.

This isn’t the first time animals have been seen to change behavior during an eclipse. Animals that like the light tend to slow down—including mosquitoes—while those that prefer the dark tend to get more active.

The black swifts usually head southward around September. So depending on where they are right now, they might experience that roller-coaster ride again soon. That’s because there’s a lunar eclipse coming up on Monday night. More about that tomorrow.

Script by Damond Benningfield

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Jupiter has a bulging waistline. The planet is almost 6,000 miles thicker through the equator than through the poles — the result of diet and activity.

Jupiter is the largest planet in the solar system. It’s 11 times the diameter of Earth, and more massive than all the other planets combined.

Jupiter grew so large because it was born far from the Sun. At that distance, it was cold enough for the planet’s growing center to incorporate a lot of ice in addition to rock, so it grew big and heavy. And that gave it a strong gravitational pull.

Jupiter used that gravity to suck in a lot of hydrogen and helium gas that were left over from the birth of the Sun — gas that wasn’t available closer to the Sun. Hydrogen and helium are the lightest of all chemical elements, so while they helped make Jupiter big, they didn’t make it very dense.

And Jupiter spins on its axis faster than any other planet — one turn in less than 10 hours. That high-speed rotation pushes the lightweight hydrogen and helium gas outward. And that gives the giant planet a giant waistline.

That equatorial bulge is easy to see through a telescope — Jupiter definitely looks squished.

You can’t see the bulge with the eye alone, but Jupiter itself is especially easy to pick out tonight. It stands close above the Moon at nightfall. And it looks like a brilliant star. In all the night sky right now, only the Moon outshines it.

Script by Damond Benningfield

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The planet Jupiter is tough to explore — especially from close range. For one thing, it’s a long way off — an average of almost half a billion miles from Earth — so it takes a long time to get there. And it’s surrounded by powerful radiation belts that can damage a spacecraft that gets too close.

Still, several craft have survived the trip. They’ve flown past Jupiter or entered orbit. In fact, the Juno spacecraft has been orbiting the giant planet since 2016, and it’s expected to keep going for at least three years longer.

No craft has ever landed on Jupiter — because there’s nothing to land on. Jupiter doesn’t have a solid surface, so a craft would just plummet into the atmosphere before being destroyed by heat and pressure. One probe did parachute into Jupiter, providing readings on the atmosphere for several hours before it succumbed.

Scientists would love to get samples of that atmosphere for analysis here on Earth. But that’s another challenge. Jupiter’s gravity is so powerful that a craft would need to travel at about 135,000 miles per hour to get away from it — about five and a half times the escape velocity on Earth. So for now, we’ll have to settle for studying Jupiter from afar.

The planet hangs out near the Moon the next couple of nights. It looks like a brilliant star. It’s well to the left of the Moon as darkness falls tonight, but quite close above the Moon tomorrow night.

Script by Damond Benningfield

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The stars that mark the outer edge of the Little Dipper are known as the Guardians of the Pole. That’s because they’re not far from the Pole Star, Polaris. They circle around it all night, every night — like guards on patrol.

But a couple of thousand years ago, one of those stars didn’t just guard the pole — it was the pole. Kochab was closer to the celestial pole than any other bright star beginning in about 1500 BC and continuing for two millennia.

The pole star changes because of an effect known as precession. Earth wobbles on its axis like a spinning gyroscope that’s running down. It takes 26,000 years to complete a single wobble. During that time, Earth’s axis draws a big circle on the northern sky, so different stars take turns marking the pole.

Polaris is less than a degree away from the true celestial pole, which makes it a great pole star. Kochab was a good bit farther from the pole, so it wasn’t as good a marker. Still, it got the job done for 2,000 years.

You can find Kochab in the northern sky tonight. It stands almost directly to the left of Polaris as night falls, well above the bowl of the Big Dipper. It’s only a bit fainter than Polaris, so if you can find the current Pole Star, you shouldn’t have any trouble finding its predecessor. The other guardian, Pherkad, is to Kochab’s upper left, at the opposite corner of the Little Dipper’s bowl. They march around the north pole throughout the night.

Script by Damond Benningfield

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Saturn has it all — bright, beautiful rings and interesting moons. And the two appear to be related — the rings and moons are made of the same stuff. That raises an interesting possibility: Either the rings gave birth to the moons, or the moons gave birth to the rings.

There’s no doubt that the rings and moons are interacting with each other. Material chipped off the surfaces of some of the moons adds to the rings. And some of the stuff in the rings is glomming onto the moons.

One indication of which came first is the age of the rings — or it would be if scientists were sure of the number. Some studies say the rings are about as old as Saturn itself — more than four billion years. If so, they might have formed when a giant moon broke apart when Saturn was young. In that case, the ring material could have come together to form today’s moons.

But other studies say the rings formed recently — perhaps within the past hundred million years. In that case, the rings could have formed from the moons — perhaps from debris left over after big collisions, from a constant “chipping away” from smaller impacts, or from eruptions on the moons themselves.

So until scientists can agree on the age of Saturn’s rings, they won’t be able to say which came first — its amazing moons or its brilliant rings.

Saturn is easy to spot tonight. It stands directly above our Moon at nightfall, and looks like a bright star.

Script by Damond Benningfield

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If you need some extra chills to go along with your trick-or-treating or other Halloween fun tonight, just look into the sky. It’s filled with ghosts, witches, and Gorgons — the snaked-headed sisters of mythology who turned anyone who looked at them to stone.

The Gorgons are four stars in Perseus, low in the northeast as night falls. The brightest of the four represents Medusa, one of the sisters. The other three arc to its right. The bright one is Algol, from an Arabic phrase that means “the demon’s head.” It may have received the name because it fades dramatically every three days or so — the result of a fainter star passing in front of a brighter one.

The Skull Nebula — the final gasp of a dying star — is in the southeast, in Cetus — the sea monster. And the Witch Head Nebula — a giant cloud of gas and dust — climbs into view before midnight, close to Rigel, the bright foot of Orion. It looks like the profile of the wicked witch in “The Wizard of Oz.”

Two nebulas are called “the Ghost,” and both are high in the northern sky. One is near the “house” outlined by the stars of Cepheus the king. The other is near the “W” outlined by the stars of his wife, Cassiopeia. Both are clouds of gas and dust. Part of the outline of the “kingly” ghost looks like demons with horns. And the outline of the “queenly” one looks like a ghostly sheet blowing on the wind — among the spooky sights in the sky on Halloween night.
 

Script by Damond Benningfield

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