StarDate

The planet Vulcan, of “Star Trek” fame, is hot, rocky, and desolate — and a long, long way from Earth. But in the 1800s, many astronomers believed there really was a planet Vulcan. It, too, would have been hot, rocky, and desolate — but much closer to home. In fact, they suspected it was orbiting quite close to the Sun.

Astronomers got the idea that there must be another planet by plotting the orbit of Mercury, the closest planet to the Sun. Each time Mercury came closest to the Sun, it was a bit farther along in its orbit than the time before. Most of this change was caused by the tug of Venus, Earth, and other planets. But a tiny portion of it couldn’t be explained.

French astronomer Urbain Le Verrier said that an unseen planet or asteroid belt inside Mercury’s orbit was pulling at Mercury. His calculations had led to the discovery of Neptune, so astronomers took him seriously.

The planet was named Vulcan, for a Roman god of fire. It would be so small and so near the Sun that it would be visible only during a solar eclipse — when the Moon blocked the Sun from view — or when the planet passed directly in front of the Sun.

A solar eclipse in 1878 gave astronomers a chance to look for the planet. Despite their efforts, it was nowhere to be seen.

Vulcan was put to rest for good by Albert Einstein. He showed that the Sun warps the space around it — perfectly accounting for the discrepancies in Mercury’s orbit.
 

Script by Damond Benningfield

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If Earth’s radiation belts were as strong as those of Jupiter, we might never be able to leave our home planet. An astronaut flying through Jupiter’s belts could receive a fatal dose of radiation in just a few hours. And since it took Apollo astronauts longer than that to transit Earth’s belts, they couldn’t have lived through a trip to the Moon and back.

Jupiter is the largest and heaviest planet in the solar system. So perhaps it’s not surprising that it also has the strongest radiation belts. They’re produced by charged particles trapped in Jupiter’s magnetic field, which is also quite strong.

Some of the particles come from the solar wind — a steady flow of material from the Sun. But most of them come from Jupiter’s moon Io. It’s covered by hundreds of volcanoes. They blast sulfur dioxide and other molecules into space. Jupiter’s magnetic field rips the molecules apart, giving them an electric charge. It also accelerates them to extremely high speeds — turning them into “bullets” that could be deadly to any human visitors.

They’re not good for robots, either. The belts are especially strong around Jupiter’s equator, in the realm of the closest moons — just the region scientists want to study. So sensitive instruments need good shielding, such as lead boxes, to keep them safe.

Jupiter is close to the right of the gibbous Moon as darkness falls tonight. It looks like a brilliant star.
 

Script by Damond Benningfield

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There was something odd about the Cat’s Eye Nebula — a colorful bubble of gas blown by a dying star. Parts of the nebula have a greenish color. For decades, astronomers thought that glow was produced by a new chemical element. They called it nebulium.

An astronomer born 125 years ago today proved otherwise. Ira Sprague Bowen found that the green glow is produced not by a new element, but by a never-before-seen form of a common element: oxygen. The oxygen is “doubly ionized” — radiation from the star zaps the atoms, stripping away two of their electrons. Since Bowen’s discovery, it’s been found in the remains of many other dying stars.

Bowen specialized in studying the chemical elements — first in the lab, and later, in the stars and their remnants. He started his work at the University of Chicago, then continued at Caltech. He became director of the university’s Mount Wilson Observatory, and the first director of its new Palomar Observatory. He held the posts until he retired, in 1964. He died in 1973, at age 74.

The Cat’s Eye Nebula is several thousand light-years away, in Draco, the dragon. The nebula is in the north-northwest at nightfall. It continues to expand, as the dying star dumps 20 trillion tons of gas into space every second. That includes oxygen atoms that the star will then zap — creating the green glow once thought of as a new chemical element.
 

Script by Damond Benningfield

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Winter arrives in the northern hemisphere tomorrow night. That’s the time of the winter solstice. Tomorrow and Friday will be the shortest days of the year in the northern hemisphere.

The Sun will rise farthest south for the year as well. Over the millennia, many cultures built observatories or temples to watch that sunrise. Doors, windows, or walls were aligned to frame the rising Sun. The alignments often honored the gods, and commemorated the fact that the Sun would be headed northward, bringing longer days.

An early example is the Temple of Karnak in Egypt. It was built in Thebes, which was one of ancient Egypt’s most important cities. The temple was established about 4,000 years ago, by the pharaoh Senusret I.

On the winter solstice, the Sun rose through a narrow passage between high walls. It beamed into a sanctuary dedicated to Amun, the creator god and one of the most important gods of Egypt.

The sunrise alignment was perpendicular to the path of the nearby Nile River, giving it extra significance. Several kings added to the temple in ways that emphasized the alignment. And over the centuries, many other temples were built in the complex. Almost all of them kept that same alignment — to the rising Sun on the winter solstice.

The exact time of the solstice is 9:27 p.m. Central Standard Time tomorrow — the start of winter, which continues until the spring equinox, in March.
 

Script by Damond Benningfield

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Scientists often say they hope their experiments produce unexpected results, because that gives them something new to think about. If that’s so, then the scientists who study the birth of galaxies should be ecstatic these days. Observations by Webb Space Telescope have revealed many more galaxies in the early universe than current models had suggested.

Webb sees the early universe more clearly than other telescopes — a combination of its large mirror and its position in space, which allows it to study the light coming from the first stars and galaxies.

One of its discoveries is known as Maisie’s Galaxy. It’s named for the daughter of Steven Finkelstein, who leads a team that’s looking at early galaxies, because it was discovered on her birthday.

A first look suggested that we see the galaxy as it looked when the universe was about 300 million years old, making it the oldest galaxy yet seen. Follow-up observations added about a hundred million years to the estimate. Even so, it’s still among the most-distant galaxies seen so far.

The galaxy is less massive than our home galaxy, the Milky Way. But it’s giving birth to more stars — a vigorous young galaxy not long after the dawn of time.

Maisie’s Galaxy is near the Big Dipper, which is low in the north at nightfall, and high in the north at first light. But you can’t see Maisie’s Galaxy without the power of Webb Space Telescope.
 

Script by Damond Benningfield

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Webb Space Telescope is getting ready to wrap up an ambitious early project: Cosmos-Web — the Cosmic Evolution Survey. It’s designed to tell astronomers about the very early universe.

It’s not easy to study that era. Earth’s atmosphere absorbs some of the wavelengths of light astronomers want to study. And earlier space telescopes haven’t been big enough to see that deeply into space very clearly. Webb combines a large telescope with instruments that are sensitive to the infrared wavelengths.

Cosmos-Web is looking for some of the earliest galaxies in the universe. It’s also looking at how dark matter was distributed when the universe was young, and much more.

The project is looking at a million galaxies, some of them as they looked just a few hundred million years after the Big Bang. Webb is scheduled to start the project’s third and final set of observations this month.

The viewing area covers three times the size of the full Moon. It’s in the middle of the area of a similar Hubble telescope project about 20 years ago. That area has few stars or clouds of gas and dust, making it easier for the telescope to see deep into the universe.

That area is along the celestial equator, in Sextans. The faint constellation climbs into view by midnight, to the lower right of the bright star Regulus, the heart of the lion. It’s a region that’s getting one more “deep look” by Webb Space Telescope.

More about the telescope tomorrow.
 

Script by Damond Benningfield

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It’s a long time between birthdays on Saturn. That’s because a year on the giant planet lasts about 29 and a half Earth years. That’s how long it takes the planet to complete a single orbit around the Sun. That adds up to a lot of days — more than 24 thousand sunrises and sunsets between birthday cakes.

The exact number of days has been a little unclear. Because Saturn is a big ball of gas, it’s hard to measure the length of its day. There aren’t any mountains or lakes or continents to track as the planet rotates. And different latitudes and depths can rotate at different rates.

Without solid landmarks, planetary scientists use other methods to measure the length of a day. They track features in the planet’s clouds, which give an approximate length. They look at features in Saturn’s rings, which are pulled along by the planet’s gravity. And they use spacecraft to track radio waves produced by Saturn's magnetic field.

Those methods have produced different results, ranging from about 10 hours and 14 minutes to 10 hours and 45 minutes. The best average is about 10 and a half hours — giving Saturn some pretty short days.

Saturn is in great view tonight. It looks like a bright star quite close to the Moon. They’re in the south-southwest as night falls, and set in late evening.
 

Script by Damond Benningfield

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Canterbury Cathedral is one of the most historic buildings in England. That history isn’t limited to assassination, civil war, and famous novels. It preserves some of the history of the solar system as well.

And scientists are literally vacuuming it up. They’re scouring the roof of Canterbury and other cathedrals for bits of space dust.

Most of the bits are pieces of asteroids — large rocks that orbit the Sun. Collisions between them create clouds of dust. Thousands of tons of the dust grains fall to Earth every year.

They’re hard to find, though, because they’re mixed with all the dust produced here on Earth. So researchers from the University of Kent decided to look on cathedral roofs. There’s a lot of area to search, the roofs are seldom touched, and the cathedrals maintain good records of construction and maintenance.

The scientists vacuum up the dust. They use several techniques to sift through it to find the bits from space. In particular, they look for tiny spheres that melted then resolidified as they plunged through the atmosphere. Some of them contain magnetic minerals, and they show signs of exposure to radiation.

Some of the grains contain water and organic compounds — the building blocks of life. Asteroids may have supplied Earth’s original water and organics. So studying these bits of space dust can help scientists learn more about Earth’s ancient history — long before England’s great cathedrals.
 

Script by Damond Benningfield

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Our sedate, middle-aged Sun spins on its axis about once a month. This leisurely rate keeps the Sun nice and round, like a beachball. But some stars rotate much faster. In fact, some spin so fast that they flatten themselves out, like a squashed beachball.

An example is Gomeisa, the second-brightest star of Canis Minor, the little dog. It’s quite low in the east by about 9 o’clock. It’s above Procyon, the constellation’s brightest star.

Gomeisa is several times as massive as the Sun, and several times wider. And it spins much faster than the Sun does — about once per day. Since a star is made of gas, that high-speed rotation forces material outward at Gomeisa’s equator, giving the star its compressed appearance.

The rotation has another important effect. Gas at the equator is moving at more than half a million miles per hour. And since the equator is bulging outward, it “feels” less of a gravitational grip than material at the poles. So some of the hydrogen gas at the equator gets flung out into space, like water whirling away from a spinning lawn sprinkler. That surrounds Gomeisa with a disk of gas that’s several times wider than the star.

If you could get close to Gomeisa, you’d see one other odd effect. Because the gas at the poles is closer to the center of the star, it’s much hotter than gas at the equator. So the star’s poles are brighter than its equator — a two-toned appearance for a flattened star.
 

Script by Damond Benningfield

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The Big Dog trots across the southern sky on December nights. It’s easy to spot because it’s home to Sirius, the brightest star in the night sky. Sirius rises in the southeast in mid-evening, with the rest of the constellation below it and to the sides.

Sirius really is a fairly bright star. But it’s a mere firefly compared to some of the other stars of Canis Major. One example stands close to the right or upper right of Sirius during the evening.

Mirzam looks much fainter than Sirius, but that’s a bit of a trick. The star is really thousands of times brighter. But it’s also much farther — about 500 light-years, versus less than nine light-years for Sirius.

That means that Mirzam is quite a stunner. When you add up all forms of energy, it’s thousands of times brighter than Sirius, and tens of thousands of times brighter than the Sun.

The key to its brightness is the star’s mass. It’s so heavy that its gravity squeezes its core tightly. That’s like mashing your foot down on your car’s accelerator — it revs up the reactions in the star’s core. As a result, the core produces much more energy. But also like a gas-powered car, mashing down the pedal uses up the fuel much more quickly. So Mirzam will live about one-tenth of one percent as long as the Sun will. When its time is up, it’ll explode as a supernova — a brilliant ending for a brilliant star.

We’ll talk about an impressive star in the Little Dog tomorrow.
 

Script by Damond Benningfield

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