StarDate

Archaeologists recently released pictures of a hidden chamber inside the pyramid of Khufu, the largest of the Great Pyramids of Giza. The chamber was discovered with cosmic “X-rays.”

Cosmic rays are particles from exploding stars and other powerful events. When they strike atoms and molecules in Earth’s atmosphere, they create showers of other particles, including muons. They zip through solid matter — including the pyramid, which was built more than 4500 years ago. Detectors placed around the pyramid picked up the muons, providing a 3D view of its interior — revealing the 30-foot-long chamber.

The X-rays aren’t the pyramid’s only connection to the stars. It was laid out with the help of the North Star. And a shaft inside the pyramid points to another star.

When the pyramids were built, north was marked not by today’s North Star, Polaris, but by Thuban, a star in Draco. Under dark skies, it’s visible along the line between Polaris and the tip of the handle of the Big Dipper. The change is the result of a wobble in Earth’s axis. Guided by Thuban, architects aligned the pyramid with the cardinal directions with amazing precision.

The pyramid also contains a shaft that aims at Orion’s Belt. In ancient Egypt, the stars of Orion represented Osiris, the god of the underworld. A dead king joined Osiris as one of the stars in that part of the sky. So the shaft provided a path from this world to the next.
 

Script by Damond Benningfield

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Our solar system is heading into the aftermath of a stellar breakup — a ribbon of stars that split away from a big family of stars. One of the brightest members of the ribbon stands high overhead at midnight: Alphecca, the brightest star of Corona Borealis, the northern crown.

The stars in the ribbon were once members of a good-sized cluster. Today, though, the cluster’s been whittled down to only about a dozen stars, including five stars of the Big Dipper.

The cluster is being torn apart by the gravitational tug of other stars, plus giant clouds of gas and dust. Dozens of stars that once belonged to the cluster are now moving through the galaxy on their own. They form a ribbon that spans hundreds of light-years. The Sun is on the outskirts of the ribbon, but it’s moving in a different direction.

Astronomers are pretty sure of the origin of the stars in the stream because they still move in the same speed and direction as the cluster’s core. The stars are all about the same age, too. And they have the same chemical composition — good indications that they’re all members of the same stellar family.

Alphecca is 75 light-years away — about the same distance as the cluster’s core. It’s in a pretty semicircle of stars that’s high in the east at sunset, and passes across the top of the sky around midnight. Alphecca is at the middle of the semicircle — a member of a big stellar family that’s heading off on its own.
 

Script by Damond Benningfield

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The bright heart of the lion beats near the Moon this evening. Regulus, the star that marks the heart of Leo, stands quite close to the lower left of the Moon at nightfall.

And Regulus is a strong heart. It’s much bigger, brighter, and more massive than the Sun. And it spins about 15 times faster — more than 700,000 miles per hour at the equator.

Regulus whirls around so fast because it “stole” a lot of gas from a nearby companion star. As the gas poured in, Regulus twirled faster and faster. Today, it spins so fast that it bulges outward at the equator, so it looks like a smashed beachball.

If Regulus were to spin just 10 percent faster, it would rip itself apart. That’s unlikely to happen — for one thing, it’s already pulled in all of the available gas from its companion.

But some other stars are seen to spin much closer to that edge. Gas squirts away from such a star’s equator, forming a disk around it.

As the gas moves out, it can come together to form tiny grains of dust. The stardust absorbs some of the star’s light — especially blue light. That can make the star look much redder than it really is. In the 1800s, for example, astronomer John Russell Hind watched as one star changed from red to blue in a matter of weeks. The most likely explanation is that the star had spun off a shell of gas and dust, making it look red. The shell soon dissipated, though, allowing the star’s true color to shine through.
 

Script by Damond Benningfield

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LAUNCH CONTROL: T-minus 30 seconds, and the countdown continuing to go smoothly. ...

Skylab — the first American space station — was going to be a fixer-upper. It was damaged during launch on May 14th, 1973. So when the first team of astronauts headed for the station 50 years ago today, it had a lot of work to do.

LAUNCH CONTROL: 5, 4, 3, engine sequence start, 2, 1, zero. We have launch commit, and we have liftoff! The clock is running, and Skylab has cleared the tower. CONRAD: Houston, Skylab 2. We fix anything!

But the “fixing” wasn’t easy. Astronauts Pete Conrad, Joseph Kerwin, and Paul Weitz set out to repair their damaged home. It had lost a protective shield and one of two solar panels, with the other one jammed shut. If the astronauts couldn’t fix the problems, they’d have to come home and let the next crew take a shot.

And at first, things didn’t go well. A tool designed to free the jammed solar panel didn’t work. And at the end of the first day in orbit, their Apollo spacecraft wouldn’t link up with the station. They had to take the docking system apart to fix the problem.

The crew moved into Skylab, then deployed a cover to bring down the temperatures. And ground controllers eventually worked out a way to fix the balky solar panel. So the mission continued. The astronauts studied Earth, the Sun, and how their bodies reacted to a record 28 days in orbit — a record that stood until the next Skylab mission later that year.
 

Script by Damond Benningfield

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The western sky is pretty crowded tonight. The Moon and the planets Venus and Mars join the usual lineup of stars, including the twins of Gemini and a busy star cluster known as the Beehive.

As darkness falls, the Moon stands pretty much due west, more than a third of the way up the sky. Mars is close below it, and looks like a fairly bright orange star. Venus is off to their lower right — the brilliant “evening star.”

All three of these bodies are in constant motion against the background of stars, which are much, much farther away. The Moon’s motion is obvious from one night to the next — it moves by more than the width of your fist held at arm’s length. Tonight, the star cluster M44 is close to its left. Through binoculars or a telescope, the cluster looks like a bunch of angry bees buzzing around their hive, so it’s also known as the Beehive. By tomorrow night, the Moon will have moved well away from the cluster.

Venus and Mars move more slowly, but it doesn’t take long to notice a difference — especially when they’re close to such prominent stars as Pollux and Castor, the twins of Gemini.

Pollux is directly above Venus tonight, with Castor to its right. By late next week, though, Venus will line up side by side with the bright stars. At the same time, Mars will be passing directly in front of the Beehive — a long way from its current location.

Tomorrow: Patching up the first American space station.
 

Script by Damond Benningfield

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The twins of Gemini are pretty popular among the worlds of the solar system right now. Mars lined up side by side with them last week, and Venus will join them next week. But tonight, it’s the Moon’s turn. Pollux and Castor stand to the Moon’s right and upper right this evening, with Pollux closer to the Moon. And to spice things up a bit, Venus is close below them — the brilliant “evening star.”

All of the close encounters are made possible by the location of the twins. They’re not far from the ecliptic — the Sun’s path across the sky. The Moon and planets travel close to the ecliptic as well. So when they slide through Gemini, they’re naturally going to pass near the twins — with Pollux always the closer one.

As the seasons change, though, so do the timing of those encounters. That’s because Earth basically has two “days” — one related to the Sun, and the other related to the rest of the stars.

It takes our planet 23 hours and 56 minutes to make one full turn relative to the panoply of stars. But during that time, Earth moves about one degree in its orbit around the Sun. So our planet has to rotate an extra four minutes to bring the Sun back to the same position in the sky — giving us a 24-hour day. On that clock, all the other stars rise and set four minutes earlier each day. So as the seasons change, the stars move across the sky — changing the timing of their encounters with the Moon and planets.
 

Script by Damond Benningfield

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The Moon and four other bright objects look like they’re having a block party the next few evenings. The Moon looks up at its companions tonight, stands in the middle of them tomorrow night, and waves goodbye on Wednesday.

The brightest member of the quartet is Venus, the “evening star.” It far outshines everything else in the night sky other than the Moon, so you can’t miss it. It’s also by far the closest member of the quartet now, at a distance of about 75 million miles. The planet will move even closer well into August, when it will cross between Earth and the Sun. It’ll reach a minimum distance of just 27 million miles — closer than any other planet ever gets.

Mars, on the other hand, is moving away from us. It was at its closest and brightest in December, when it shined brilliantly. As it retreats, though, it’s fading. This month, it looks like a modest orange star, well to the upper left of Venus.

The final members of the quartet are Pollux and Castor, the brightest stars of Gemini. The twins maintain the same brightness all the time. They’re so far away that a few million miles in either direction just doesn’t matter. Pollux is about 34 light-years off, while Castor is about 50 percent farther.

Venus will line up with the twins in late May and early June, while Mars will leave them behind as it moves eastward against the background of stars.

More about the Moon and twins tomorrow.
 

Script by Damond Benningfield

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Mercury is just peeking into the dawn sky now. But it stays quite low, so you need a clear horizon to see it — and binoculars wouldn’t hurt.

Mercury is the Sun’s closest and smallest major planet. And if people ever colonize the solar system, it probably won’t be a popular posting.

For one thing, it has no atmosphere, so you’d need spacesuits to get around. Temperatures at the equator can soar to 800 degrees Fahrenheit. And a day on Mercury lasts 176 Earth days. On average, that means you’d have three months of daylight followed by three months of darkness.

You’d be a lot older on Mercury, too. Mercury orbits the Sun four times for every orbit that Earth makes, giving it four “years” for every one on Earth. So your birthday cake would need four times as many candles. Of course, you’d also get four times as many cakes.

The extra cake wouldn’t add much to your weight, though; if you weigh 150 pounds on Earth, you’d weigh just 57 pounds on Mercury.

The best places to hang out on Mercury would be its poles. The bottoms of some craters at the poles never see the Sun, so they may contain big deposits of ice — a way to keep the punch cold for those frequent birthday parties.

Again, look for Mercury quite low in the east before sunrise. It looks like a fairly bright star, below brilliant Jupiter. It will get a little higher and brighter in the coming days, but will remain a tough target.
 

Script by Damond Benningfield

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Some stars are classified as “peculiar.” That’s because they show odd mixtures of chemical elements. They have higher amounts of radioactive elements and of rare earths — the kinds of things used in electric-car batteries.

One star stands out as the most peculiar of all: Przybylski’s Star, named for the astronomer who discovered its bizarre nature. It’s about 350 light-years away, in Centaurus, which pokes above the southern horizon at nightfall.

Some elements are common among the stars, while others are quite rare. And Przybylski’s Star shows a complicated brew of elements unlike any other star’s.

It has very low levels of iron, nickel, and other metals — as little as one-tenth the level seen in the Sun. But it has high levels of “rare earths” — elements that just don’t show up in other stars. It also appears to have high levels of some radioactive elements that decay in a few thousand years or less. Such elements should have long since vanished from Przybylski’s Star, which is about a billion and a half years old.

Scientists haven’t yet explained what’s going on. One possibility is found in the star’s rare combination of qualities: It’s hot, it has a strong magnetic field, and it spins very slowly. That could “levitate” atoms that normally would be mixed inside the star, bringing them to the surface where we can see them.

Whatever the explanation, Przybylski’s Star will remain perhaps the most peculiar of all stars.

Script by Damond Benningfield

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A cosmic jellyfish floats through a giant cluster of galaxies. It has a twisting “tentacle” that’s 200,000 light-years long — a trail of gas that’s given birth to hundreds of thousands of stars.

Galaxy D100 is in the Coma Cluster, a collection of thousands of galaxies. It’s classified as a “jellyfish” galaxy. Astronomers have discovered dozens of them. All of them are wide, thin disks, with tentacles of gas dangling behind them. And all of them are members of big clusters.

A galaxy turns into a jellyfish as gravity pulls it toward the center of a cluster at millions of miles per hour. The falling galaxy plows through massive amounts of gas between the cluster’s galaxies. That forces gas out of its own disk. The gas forms long ribbons behind the galaxy — the tentacles of the jellyfish. Gas in the tentacles clumps together, giving birth to bright new stars and setting the tentacles aglow.

D100 began forming its tentacle about 300 million years ago. As gas was ripped from its disk, star formation shut down in the disk and began in the tentacle. Stars are being born in clumps that are a few hundred light-years wide. The largest clump is just outside the disk, and contains about 200,000 stars.

The Coma Cluster is in the constellation Coma Berenices, which is high in the sky at nightfall. D100 is plunging toward the center of the cluster, leaving a trail of young stars behind it.
 

Script by Damond Benningfield

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