StarDate

Our planet’s north magnetic pole is on a journey across the top of the world. But it’s slowing down. Over the past five years, it’s put on the brakes – its position has changed much more slowly than over the previous couple of decades.

Earth’s magnetic field acts like a giant bar magnet, with north and south poles. The poles aren’t tied to the geographic poles – they wander.

The north magnetic pole was discovered in 1831. At the time, it was centered over northwestern Canada. It moved farther south, then made a big turn, toward Siberia. In all, it’s moved almost 700 miles since it was discovered.

For a couple of decades, it was moving at more than 30 miles per year. More recently, though, it’s slowed to about 22 miles a year – the biggest slowdown ever recorded. Scientists are trying to understand why.

The magnetic field is generated by motions of molten rock in Earth’s outer core. Those motions produce electric currents, which create the magnetic field. So the changing position and rate of motion are telling us something about what’s going on deep inside our planet.

The change in the magnetic pole has important practical implications as well as scientific ones. GPS, aircraft, the military, and others use magnetic north for navigation. So maps of Earth’s magnetic field are updated every few years to show the change in the pole’s location – keeping everyone headed in the right direction.

Script by Damond Benningfield

The full Moon achieves a sort of celestial balance tonight. It’s passing across Libra, the balance scales – a symbol of justice. But the proper names of the constellation’s brightest stars have nothing to do with balance, justice, or anything similar. Instead, the names mean “the claws” – of nearby Scorpius, the scorpion.

Originally, the stars did belong to Scorpius. But thousands of years ago, they were severed from the scorpion and placed in a new constellation.

As night falls, one of the claws stands to the upper left of the Moon. Called Zubenelgenubi, it represents the southern claw. It’s the second-brightest star of Libra, and it’s about 75 light-years away.

Like many of the stars in the night sky, Zubenelgenubi is deceiving. To the eye alone, it looks like a single point of light. Scan it with binoculars, though, and you’ll see two stars. They appear to be moving through space together, so they might be orbiting each other. But they’re so far apart that it takes the light from each star a month to reach the other one. At that separation, they might not be held together by gravity – their close appearance might be just a coincidence.

Each of the two stars is actually a binary in its own right. In both cases, the stars are so close together that even giant telescopes can’t see them as individual stars. But we see the “fingerprints” of two stars in the light from each half of the southern claw.

Script by Damond Benningfield

As World War II wound to an end, President Franklin Roosevelt asked his top scientific advisor a question: How could the type of research that helped win the war be applied to peacetime? The advisor suggested a new agency to support basic research at colleges and universities. It took a few years to work out the details. But 75 years ago today, President Harry Truman signed the law establishing that agency: the National Science Foundation.

Over the decades, its mission has expanded into many fields, from chemistry and physics to computers and materials science.

The list also includes astronomy. NSF established the first national observatories in 1956 – optical telescopes in Arizona, and radio telescopes in West Virginia. Today, NSF-supported facilities span the globe. They include observatories that no one was even dreaming of when the agency started. They hunt for the ghostly particles known as neutrinos, and listen for gravitational waves from merging black holes and neutron stars.

NSF also is a partner in the Vera Rubin Observatory, which is scheduled to take its first peek at the universe this summer. Its giant telescope will scan a wide slice of the sky every night. It will discover exploding stars, asteroids, and other objects. It will map the Milky Way Galaxy. And it’ll provide new information about dark energy and dark matter – basic research that will teach us much more about the universe.

Script by Damond Benningfield

The star Spica, which is quite close to the Moon tonight, is quite different from the Sun. It consists of two stars, not one. Both stars are many times bigger and heavier than the Sun. And their surfaces are tens of thousands of degrees hotter, so the stars shine blue-white.

On the other hand, the Sun and Spica are made of almost exactly the same ingredients: mainly hydrogen and helium, with only a smattering of heavier elements. That composition was figured out by an astronomer who was born 125 years ago tomorrow, in England.

Cecilia Payne caught the astronomy bug when she saw a lecture by Arthur Eddington, one of the world’s leading astronomers. She started her education in England, then finished in the United States. She earned a Ph.D. in 1925. And her doctoral thesis shook up the field. Decades later, in fact, Otto Struve, the first director of McDonald Observatory, called it the most brilliant thesis ever written in the field.

Astronomers already had the techniques for measuring what stars are made of. Their work led them to believe that stars contain the same mixture of elements as Earth. But Payne used a new way to analyze the readings, taking into account the charge of atoms. She concluded that stars were made mainly of hydrogen and helium – elements formed in the Big Bang.

By a few years later, just about everyone accepted her analysis – completely changing our concept of the stars.

Script by Damond Benningfield

The surface of the Sun is like a pot of boiling water. Millions of bubbles of hot gas churn across it, constantly rising and falling. But the bubbles are a little bigger than those on your stovetop.

The bubbles are known as granules. They form as energy from deep inside the Sun works its way to the surface. That heats the gas in the Sun’s top layer, forming bubbles. As they reach the surface, their gas cools and drops back into the Sun. This non-stop activity creates an easy-to-see pattern of bright blobs – the hot gas – with dark lanes between them – the cooler gas.

The size of the granules varies from about a hundred miles to more than a thousand – big enough to swallow Texas. And each granule lasts for no more than about 20 minutes.

A recent study said the granulation changes a bit during the Sun’s 11-year cycle of magnetic activity. Just after the peak of the cycle, there are slightly more granules than average, but they’re a little smaller than average.

Other stars are so far away that we can’t see the granulation on most of them. But several types of observations confirm that they, too, are boiling away. Astronomers have seen granulation on a few stars. The stars are much bigger than the Sun. And they’re late in life, so they’re undergoing big changes. The granules on those stars are tens of millions of miles across – dozens of times the diameter of the Sun – giant bubbles of hot gas on giant stars.

Script by Damond Benningfield

The Gaia spacecraft took its final look at the stars in January. But its work is far from over. Its observations will be producing new discoveries for decades.

Above Earth’s blurring atmosphere, the space telescope kept a sharp eye on the heavens for more than a decade. It studied about two billion objects – mostly stars. It measured their temperature, composition, and motion. And it plotted their positions with amazing precision. That’s allowed astronomers to produce the best 3-D maps of the Milky Way Galaxy to date – by far.

Those maps have helped plot the origins of many stars – the remains of star clusters or even small galaxies pulled in by the Milky Way. And that’s revealed a lot more about the history of the entire galaxy.

Gaia also looked at other galaxies, at asteroids and comets in the solar system, and many other objects. It even helped reveal a couple of planets in other star systems.

The craft ran out of the gas it used to keep its telescope on target, bringing its mission to an end. But it takes a lot of time to process Gaia’s observations and release them for study. There have been three big batches so far, which have yielded more than 13,000 scientific papers. The next big release is scheduled for late next year. And the final release – everything Gaia saw and reported – won’t be ready until late 2030 at the earliest – a treasure trove that astronomers will be poking through for decades.

Script by Damond Benningfield

The gusty winds of spring make it a good season for flying a kite. But you might not want to try it on the planet Wasp-127 b – it would be hard to hang on. Winds high above the surface blow at an astounding 20,000 miles per hour – a hundred times faster than winds in the strongest category five hurricanes on Earth.

The star – Wasp-127 – is a lot like the Sun. But the planet isn’t much like any planet in the solar system. It’s much wider than Jupiter, the largest planet. But it’s only one-sixth of Jupiter’s mass. That makes it one of the “puffiest” planets yet seen.

Wasp-127 b was discovered because it passes in front of its parent star every four days. As it does so, starlight filters through the atmosphere. Astronomers use that effect to learn something about the atmosphere.

Recent observations revealed that material in the upper atmosphere is moving extremely fast – blown by the fastest winds yet seen on any planet. The observations also suggested that there’s a big temperature difference between the dawn and evening skies – more than 300 degrees Fahrenheit – one more reason the planet isn’t a good place to fly a kite.

The Wasp-127 system is in the constellation Sextans, the sextant. This evening, it’s well to the lower right of the Moon. But the system is more than 500 light-years away, so the star is too faint to see without a telescope.

Script by Damond Benningfield

Over the millennia, every culture has named the bright stars. The names represented characters from mythology, things from the natural world, human traits and values, and more. Different cultures seldom agreed on what to call an individual star. But one exception seems to be Regulus, the brightest star of Leo. Just about everybody saw the star as a symbol of strength and power.

The name “Regulus” means “the little king.” The name made its debut in the early 16th century – translated from the Greek name with the same meaning.

It’s not hard to see why Regulus was held in such high esteem. It’s quite bright – only a couple of dozen stars and planets outshine it, and many of those just barely top it.

And Regulus lies near the ecliptic – the Sun’s path across the sky. Any star close to that path has always received special attention. And there aren’t many bright stars close to Regulus – especially along the ecliptic. So Regulus has held a lofty position in the sky stories of many cultures – a “little king” at the heart of the lion.

Regulus appears quite near the Moon as night falls this evening, and a bit farther from the Moon as they set in the wee hours of the morning. Although it loses a bit of its luster in the glare of the Moon, the star is always a beautiful sight.

Script by Damond Benningfield

No one has seen Comet Halley in decades. Even so, it’s reminding us of its presence about now. That’s because it’s responsible for the Eta Aquarid meteor shower. The shower is predicted to reach its peak tomorrow night, with top rates of about 40 or 50 meteors per hour.

A meteor shower occurs when Earth passes through the orbital path of a comet. As a comet nears the Sun, some of the ice at its surface vaporizes in the heat. That releases small bits of rock and dust. Over time, this “comet dust” spreads out along the comet’s orbit. When Earth intersects the orbit, some of the debris slams into the atmosphere at tens of thousands of miles per hour – forming the glowing streaks known as meteors.

The Eta Aquarids are one of two showers that are caused by Halley. The other takes place in October. Our planet passes a little deeper into the debris field in May, so this shower is better. Yet we’re a long way from the center of Halley’s trail – catching the fringe of a trail of comet dust.

The shower is in better view from the southern half of the country. That’s because the point at which the meteors appear to “rain” into the atmosphere stays low in the south. To see the Eta Aquarids, find a dark, safe skywatching site, away from city lights. The best view comes in the wee hours of the morning.

The Moon will be out of the way then, making it easier to see the “shooting stars” from Halley’s Comet.

Script by Damond Benningfield

The Moon and Mars are flirting with danger – they’re sneaking up on the Beehive star cluster, in the constellation Cancer. The cluster doesn’t have much of a “sting,” though – it’s about 600 light-years away.

The Beehive contains about a thousand stars, which are maybe 700 million years old – fairly young in astronomical terms. That means the Beehive maintains a mixture of stars of different masses.

Its heaviest stars have burned out, leaving only their dead cores. About two-thirds of the remaining stars are red dwarfs – cool, faint embers only a fraction of the mass of the Sun. About a third are similar to the Sun. And about two percent are heavier than the Sun. Because more-massive stars burn through their nuclear fuel more quickly, those stars will expire first.

The cluster’s brightest star is Epsilon Cancri. Although it looks like a single point of light, instruments reveal that it consists of at least three stars. All three are more than twice as massive as the Sun, so they’re nearing the end of the prime phase of life. Soon, they’ll puff up to giant proportions. After that, they’ll blow away their outer layers, exposing their dead cores – and the Beehive will lose some of its luster.

The Beehive is close to the lower left of the Moon at nightfall, and is an easy target for binoculars. Mars looks like an orange star below the Moon. It’ll slip past the cluster over the next couple of days.

Script by Damond Benningfield