StarDate

Every star is losing mass. Some are just a lot more serious about it.

An example is Aldebaran, the eye of the bull. The star is below the Moon as night falls, and to the left of the Moon as they set, before dawn.

Aldebaran has passed the end of its normal lifetime, so it’s puffed up to giant proportions — it’s about 45 times the diameter of the Sun. At that size, the gas at its surface is barely held in place by the star’s gravity.

In fact, a lot of it isn’t held in place — it’s blown into space as a high-speed wind. The wind carries away enough gas to make a planet as massive as Earth in about 300,000 years. That’s about 500 times the rate at which the Sun blows gas into space.

Much of the gas condenses to form grains of dust. They’re creating a hazy cloud around Aldebaran. When the star dies, it’ll expel all of its outer layers of gas into space. They’ll be moving much faster than the present-day wind. As they ram into the older gas and dust, they’ll create shock waves and sculpt “fingers” of dense material. The whole mixture of gas and dust will create a colorful bubble that will shine for tens of thousands of years.

That’s also in the future of the Sun. In about five billion years, it will puff up like Aldebaran has. The solar wind will get a lot thicker, surrounding the Sun with its own cocoon of gas and dust. Finally, the Sun will lose its outer layers and create its own bubble — the final outpouring of a star.
 

Script by Damond Benningfield

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Tycho Brahe, who was born 475 years ago this week, in Denmark, was one of the most accomplished astronomers in history — and one of the most colorful.

On the professional side, he was a great night-sky observer. Working before the invention of the telescope, he showed that a brilliant “new” star was far beyond Earth, for example — demonstrating that the heavens weren’t unchanging, as most astronomers of the time believed.

On the personal side, Tycho was larger than life. He was a descendant of several noble families, and was stolen away by his uncle when he was only two. In college, after a drunken argument over who was the best mathematician, he fought a sword duel with a cousin. He lost part of his nose, and wore a false nose — made of brass — the rest of his life.

In 1572, he became royal astronomer to the king of Denmark. The king gave him an island, where Tycho built a major observatory and teaching center. But he quarreled with the locals, who objected to his heavy demands.

After the king died, Tycho didn’t get along well with the new king, so he left his island. He became imperial astronomer to the Holy Roman Emperor Rudolph the Second, and set up a new observatory near Prague.

During a royal banquet, Tycho refused to leave the table to relieve himself. That caused a serious bladder problem. Tycho died from that problem days later — one final episode in the life of one of astronomy’s most colorful characters.
 

Script by Damond Benningfield

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Tycho Brahe was having a hard time deciding what to do with his life. He’d studied astronomy, but he was also interested in alchemy — changing one element into another — as well as other fields. It took an exploding star to make up his mind.

As he walked out of his laboratory one night in 1572, Tycho saw a brilliant new star in the sky — brighter than the planet Venus. He watched it for months. His work showed that the star was far from Earth. And that demonstrated that the heavens could change — an idea that went against the science of the day. That made him famous, and convinced him to concentrate on astronomy.

Tycho was born 475 years ago today, in Denmark. After his writings about the “new star” — known today as Tycho’s Supernova — he became royal astronomer to the king of Denmark. He built big observatories on an island. The telescope hadn’t been invented yet, so he used instruments that helped him plot the stars with his eyes alone. And he was good at it — perhaps the best naked-eye observer in history.

In addition to his work with stars, for example, Tycho showed that comets are far beyond Earth — not odd phenomena in the atmosphere, as most scientists thought.

Tycho’s observatory also was a center of learning, with dozens of students studying science and other fields. It remained busy until Tycho had a falling out with the new king. Yet his legacy was secure — as one of the great astronomers in history.

More tomorrow.
 

Script by Damond Benningfield

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A young star in Orion presents a mystery. More than a decade ago, it twice faded by a good bit, for several weeks each time. Astronomers had a possible explanation. But the star hasn’t faded that way again, so they need a new explanation.

PDS 110 is about a thousand light-years away. It stands close to Orion’s Belt, which is in good view in the east by about 8 p.m. And PDS 110 might be related to the stars of the belt — they probably all formed from the same cloud of gas and dust.

PDS 110 is only about 10 million years old. It may not even be a full-fledged star yet — it’s just entering the prime of life.

In 2008 and 2011, it faded by almost a third, for a few weeks each time. It was suggested that the star had a companion — a giant planet or a brown dwarf — that was encircled by a giant system of rings. When the companion was in the right place in its orbit, the rings passed in front of the star, blocking part of its light.

Astronomers expected to see a similar dimming in 2017. They watched PDS 110 for weeks from a dozen observatories. But nothing happened. They also looked up observations made up to 50 years earlier — again with no big fades.

Since the star is so young, it’s surrounded by dust left over from its formation. Big clumps of dust might have passed in front of the star during the earlier events. But astronomers are still trying to figure out for sure what caused the big fades from this young star.
 

Script by Damond Benningfield

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In the 1860s, a new meteor shower began to punctuate the December sky. And for more than a century afterwards, it got better and better. Now, it’s become the most reliable shower of the year.

The Geminid shower is at its best the next couple of nights. At its peak, it should produce a hundred or so meteors per hour. The Moon is in view for most of the night. But it sets early enough to provide a few good hours of meteor watching.

Geminid meteors are bits of dust from an asteroid. The dust grains spread out along the asteroid’s orbit. Earth intersects this path every December, so some of the grains ram into the upper atmosphere. They quickly vaporize, forming the glowing streaks of light known as meteors or shooting stars.

The path didn’t begin to intersect Earth’s orbit until the 1800s, so the Geminid shower is the youngest of all the big meteor showers. The rate of visible meteors has increased since its discovery. That’s because the gravity of Earth and Jupiter have shifted the path of the dust grains. Earth now plows more directly through that path — turning the Geminids into the year’s best meteor shower.

Look for the shower beginning in mid- to late evening. It usually produces a few especially bright meteors, so it’s worth a look even through the moonlight. And although its peak is brief, it can produce the odd bright meteor for a night or two after the peak — extra time to catch the fireworks.
 

Script by Damond Benningfield

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Summer is long gone, and winter’s just more than a week away. Yet one of the signature star patterns of summer is still in great view in the evening sky.

The Summer Triangle is well up in the west at nightfall. Its brightest point is the star Vega, about a third of the way up the sky. Deneb stands above it, with Altair well to the left of Vega.

Deneb represents the tail of Cygnus, the swan. At this time of year, the swan is nose-diving toward the horizon. In this position, the star pattern looks a lot like a crucifix, so it’s also known as the Northern Cross. It stands directly atop the horizon about 10 o’clock.

Every star and constellation has its own season. That’s because there’s a difference in the time it takes the Sun and the other stars to return to the same position in the sky.

The background stars — those we see at night — return to the same position every 23 hours and 56 minutes. But during that span, Earth moves a good distance in its orbit around the Sun. As a result, it takes four minutes longer for the Sun to return to the same position. The difference means that the distant stars all rise and set four minutes earlier each night, or two hours each month.

The Summer Triangle first appears at nightfall around the start of summer. Over the following months it climbs high overhead, then drops down the western sky in autumn and into early winter — a remnant of the warmer months of summer.
 

Script by Damond Benningfield

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To go to the stars, you need a starship. To power it, you need something other than rockets — like warp drive. And a recent study says building a warp drive might not be as tough as it first seemed.

The closest star other than the Sun is Proxima Centauri — about four light-years away. Yet with conventional rockets, it would take 50,000 years to get there. A research project is trying to use laser-powered sails to cut that to just 20 years — but only for spacecraft weighing just a few grams.

Warp drive would enfold a spacecraft inside a “bubble” of space-time — like being in its own universe. That bubble could travel at lightspeed or faster without violating the laws of physics. Early concepts, though, suggested it would take a non-existent form of energy to create the bubble.

But a study by Erik Lentz, of a physics institute in Germany, suggested otherwise. Lentz did new calculations based on the theories of relativity. And he found that it could be possible to create a warp bubble with “normal” energy. And it could be done so that time would pass at the same rate for people inside the bubble as those on the outside.

It would take ridiculous amounts of energy to create a bubble the size of a football field — smaller than any version of the starship Enterprise. But other studies have suggested ways to cut the energy needs — perhaps to a scale that could be powered by a nuclear reactor — carrying a starship at warp speeds.
 

Script by Damond Benningfield

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If you’re going to move to another star system, you might as well go big. That’s the idea behind worldships — starships that would carry everything you’d need to set up a colony at another star.

Worldships came from science fiction. But a few scientists and engineers have studied how they might work.

They’d carry thousands of people — maybe tens of thousands. That means they’d be many miles long. And they’d carry everything needed to sustain the people on board for the trip.

And it would be a long one. Many concepts of worldships envision peak speeds of maybe one percent of the speed of light. At that speed it would take more than 400 years to reach the closest star other than the Sun, Proxima Centauri.

A ship would need to be shielded from radiation and collisions with space rocks, and it would have to be able to repair itself.

The main challenge, though, might be social. The trip would last for generations — plenty of time for social order to break down. So the way the society is organized and controlled would need a lot of thought and T-L-C.

A recent study said it could be centuries before the global economy could pay for a worldship. And it pointed out a possible problem that also shows up in science fiction: When a worldship reaches its destination, it might find the place already inhabited — by people traveling in faster starships invented long after the worldship left Earth.

More about star travel tomorrow.
 

Script by Damond Benningfield

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After slipping past Venus and Saturn the last couple of evenings, the Moon hangs out with one more planetary companion the next couple of nights: Jupiter, the giant of the solar system. The brilliant planet stands above the Moon as night falls tonight, and to the right of the Moon tomorrow night.

Jupiter’s most obvious feature is the Great Red Spot — a giant storm system. It towers high above the surrounding clouds, and it’s been around for at least 150 years — and perhaps much longer. Compounds dredged up from deep below the storm color it in shades of red and orange.

The Great Red Spot has received a lot of attention in recent years because it’s been shrinking. A hundred and fifty years ago, it was between two and three times the diameter of Earth. Today, though, it’s only about one-and-a-quarter times the size of Earth — about 10,000 miles across.

A recent study found that the storm’s winds are changing, too.

Hubble Space Telescope keeps a regular eye on Jupiter. Scientists use it to track the winds across the planet — especially in the Great Red Spot. They found that, from 2009 to 2020, the wind at the rim of the storm sped up by about eight percent. It blows at a brisk 400 miles per hour — more than twice the speed of the most powerful hurricane ever recorded on Earth.

On the other hand, winds at the center of the storm have slowed down — adding to the intrigue about this amazing storm.
 

Script by Damond Benningfield

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The giant planets of the outer solar system have giant families of moons. Saturn, for example, has more than 80 known moons. The planets protect the moons by enfolding them in their own magnetic fields — some of the time.

Saturn’s magnetic field is generated deep within the planet. Saturn’s core is made of rock and metal. It’s surrounded by a thick layer of hydrogen. That layer is squeezed so tightly that it acts like a metal. The core and the metallic hydrogen rotate at different rates. That produces an electric dynamo that generates the magnetic field.

Saturn’s magnetic field is hundreds of times stronger than Earth’s. It deflects much of the solar wind — a flow of charged particles from the Sun — as well as cosmic rays, which are particles from outside the solar system.

But the solar wind sculpts the magnetic field into a teardrop shape. The region that faces the Sun is squeezed in toward Saturn. The region away from the Sun forms a tapered tail that extends millions of miles into space.

So depending on how far it is from Saturn, a moon may be protected when it’s on one side of the planet, but unprotected on the other — and subject to the full force of the solar wind.

Look for Saturn near our own moon tonight. It looks like a bright star, just above the Moon at nightfall. They’re flanked by two brighter planets — Venus to the lower right, and Jupiter to the upper left. More about the Moon and Jupiter tomorrow.
 

Script by Damond Benningfield

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