StarDate

The Sun has been drowsy of late. Last year, it posted the equivalent of nine months without the dark magnetic storms known as sunspots. That’s the fourth-highest number in the last 170 years. This year began in similar fashion. And scientists expect the quiet times to continue.

The Sun goes through an 11-year cycle of magnetic activity. At the cycle’s peak, scores of spots mar the Sun’s surface. And big explosions send radiation and particles racing through the solar system. When they reach Earth, these outbursts create intense displays of the northern lights. They also can damage satellites, disrupt some radio communications, and cause power outages on the surface. But at the cycle’s low point, called solar minimum, the Sun produces fewer outbursts.

The current cycle began in 2008 and peaked in 2014. It was the quietest peak in decades. And the cycle has been especially quiet over the last couple of years. It produced no sunspots at all from November 14th through December 23rd — the longest spot-free span since 1996.

And forecasters predict the cycle will reach its minimum this month.

Some of the few sunspots that did appear late last year had an opposite magnetic polarity from those of the dying cycle. That suggests that the next cycle may be starting. Forecasters say the new cycle should peak in July 2025, at about the same level as the current one. So the Sun might stay drowsy for years to come.

Script by Damond Benningfield

Frank Drake picked two target stars for Project Ozma, the first search for extraterrestrial intelligence. The first to be scanned was Tau Ceti. And the second was Epsilon Eridani, a close neighbor — just 10 and a half light-years away.

It turns out, though, that Epsilon Eridani probably isn’t a good place to look for life. The star is young, so there hasn’t been much time for life to take hold. It probably produces a lot of ultraviolet and X-ray energy, which is dangerous. And its planets may face a steady barrage of space rocks.

Epsilon Eridani is a little smaller and less massive than the Sun, and just a third as bright. Most studies say it’s between 200 million and 800 million years old, which is quite young. Because of its youth, it spins rapidly — about twice as fast as the Sun does. That generates a strong magnetic field. The field creates big outbursts that would shower planets with deadly radiation.

Astronomers have discovered two possible planets in the system. But they’re bracketed by asteroid belts and a big “doughnut” of rocks and dust. Many of those space rocks fall toward the star. Some of them slam into the planets — making conditions especially hard for life.

Project Ozma found no signals from Epsilon Eridani when it scanned the system with a radio telescope in 1960. And Drake repeated the observations 10 years ago — again coming up empty. So there’s no hint of a civilization in this messy star system.

Script by Damond Benningfield

At least four planets orbit the star Tau Ceti, one of our closest neighbors. And two of those worlds are at the edges of the star’s habitable zone — the region that’s most comfortable for life. If civilizations inhabit those planets, though, they’re quiet. The first search for extraterrestrial intelligence scanned the planet, but didn’t hear a thing.

Tau Ceti is 12 light-years away — just down the block. The star is smaller and cooler than the Sun, and about half as bright. And it’s about a billion years older, so there’s been more time for life to take hold there.

But 60 years ago today, astronomer Frank Drake turned a radio telescope toward the system. It was one of two targets for Project Ozma — a hunt for other civilizations. In all, the telescope spent 200 hours scanning the two systems. But it found nothing out of the ordinary — ET wasn’t giving us a call.

Life in the system would face a big challenge. A disk of rocky debris surrounds the planets. It contains many times more material than the asteroid belt in our own solar system. Big rocks from the disk might fall inward, slamming into a planet. That could destroy life on the planet.

Project Ozma conducted only a short, narrow search for a specific sign of life at Tau Ceti. So despite the result, life could still exist on any or all of its planets. All we know for sure is that no one is beaming signals from Tau Ceti out into the galaxy.

We’ll talk about Ozma’s other target tomorrow.

Script by Damond Benningfield

One of the things that Earth and Mars have in common is the seasons. The two planets are tilted at almost the same angle. So the amount of sunlight received by their northern and southern hemispheres varies by quite a bit during the year.

And the seasons are changing on Mars this week. It’s the autumnal equinox — the beginning of autumn in the northern hemisphere, and spring in the southern hemisphere. The season will last until the winter solstice, on September 2nd.

Mars will be moving closer to the Sun throughout the season. It’ll be closest to the Sun around the start of southern summer. So the southern hemisphere will be warming up in a hurry. It’ll still be icy cold by Earthly standards. But the extra heat is enough to trigger big dust storms. And some of them can get big enough to cover the entire planet.

The extra heat also causes part of the southern polar ice cap to vanish. Carbon dioxide atop the ice cap vaporizes and enters the atmosphere. That causes the air pressure to go up a bit across the entire planet. Later, as the hemisphere cools, the CO2 recondenses on the ice cap, making it bigger and thicker — one of the cycles of the Martian seasons.

And Mars remains in good view in the early morning sky now. It forms the lower left end of a lineup of three planets at first light. Saturn is to the upper right of orange Mars, with brilliant Jupiter farther along the same line.

Tomorrow: listening in on a nearby star.

Script by Damond Benningfield

A brilliant point of light in the western evening sky is sweeping past one that’s merely bright.

The brilliant light is Venus, the “evening star.” It’s the brightest object in the night sky other than the Moon, so you can’t miss it. Despite its nickname, though, it’s not a star at all — it’s a planet. It’s the closest planet to Earth. And in some ways, it’s a near twin to our world. It’s about the same size, and it probably has a similar composition — a rocky crust and mantle around a dense core made of metal.

In other ways, though, Venus is quite different. Its atmosphere is far hotter and denser than Earth’s. And it’s topped by an unbroken layer of clouds made of sulfuric acid.

The merely bright light is Aldebaran, the ruddy eye of Taurus, the bull. It’s off to the left of Venus. And for the next two or three nights, it’s a little higher in the sky.

Aldebaran looks less impressive than Venus, but that’s an illusion — a result of its great distance. Instead, it’s a giant star — dozens of times the diameter of the Sun. If it took the Sun’s place, it would incinerate Venus and turn Earth into a burned-out cinder.

Watch Aldebaran and Venus over the next few nights. They’ll stand at about the same height on Wednesday or Thursday, depending on your latitude, before Venus pulls away. They’ll vanish from the evening sky later in the spring, then re-emerge in the morning sky — much closer together than they are now — in early July.

Script by Damond Benningfield

Canes Venatici, the hunting dogs, is awash in beautiful galaxies. In fact, four of the most prominent galaxies in our night sky congregate in one quadrant of the constellation. All four of them are spiral galaxies, like our own Milky Way.

The most famous member of that quartet is M51, the Whirlpool Galaxy. It actually consists of two galaxies. One is a bright spiral that we see face on. It’s about half the diameter of the Milky Way. The second galaxy is much smaller — a yellow blob of stars. It’s flying past the bigger galaxy, pulling out a great ribbon of material — and triggering the birth of many new stars.

M94 is near Cor Caroli, the constellation’s brightest star. It, too, is a busy star factory. It’s giving birth to millions of new stars in a ring outside its core.

New stars are also taking shape in M63. Its arms aren’t sharp and well defined like those of the other galaxies, though. Instead, they look like strings of cotton balls.

M106 is the largest of the quadrant’s bright galaxies — wider than the Milky Way. A supermassive black hole sits at its heart. It’s encircled by a disk of hot gas. Radiation from the gas sets off a chain of events that produces an extra set of spiral arms, which wrap above the galaxy’s bright disk.

Canes Venatici is in the east-northeast as night falls, to the right and lower right of the Big Dipper. All four of its prominent galaxies are visible through small telescopes.

Script by Damond Benningfield

Regulus, the bright heart of Leo, the lion, shines close to the right or upper right of the Moon as night falls this evening. And it’ll be to the lower right of the Moon as they set, a couple of hours before sunrise.

Because it was the brightest member of a prominent constellation, Regulus played a major role in the astronomy and skylore of many cultures. And they gave it names to match. In fact, the name “Regulus” means “the little king.”

The name was bestowed by Nicolaus Copernicus, the 16th-century astronomer who showed that Earth orbits the Sun, not the other way around. He adapted the name from an earlier one, Rex, which means “the king.”

Less than a century after Copernicus came up with Regulus, German astronomer Johann Bayer devised another name that’s also still in common use: Alpha Leonis, indicating that it’s the brightest or most important star of Leo.

Bayer labeled more than 1500 stars. He used a letter of the Greek alphabet followed by the name of the star’s constellation. “Alpha” usually was applied to the constellation’s brightest star, but not always. Sometimes, Bayer labeled the stars based on their location, not their brightness.

Regulus qualifies as the “alpha” star both ways. Not only is it the lion’s leading light, but it’s also at the bottom of a pattern that outlines the lion’s head and mane. So this “royal” star is the most prominent member of a royal constellation: Leo, the king of the beasts.

Script by Damond Benningfield

Two of the great beauties of the night sky, Venus and the Pleiades, will slide past each other the next few nights. Venus is the brilliant “evening star,” high in the west at nightfall. The Pleiades is a star cluster that forms a tiny dipper. It’s above Venus this evening. But Venus will stand directly beside the cluster’s brightest star tomorrow night.

Astronomers can tell you the distance to Venus to within a few miles. But the Pleiades is another story. Different studies over the last couple of decades, using different techniques and equipment, have yielded estimates that vary by about 50 light-years.

For a long time, most estimates said the distance was about 440 light-years. But a space telescope designed to make the most accurate measurements up to that time disagreed. It came up with a distance of only 390 light-years. Astronomers recalibrated the satellite’s observations a few years later and came up with a slightly greater distance.

A new and more accurate space telescope is measuring stellar distances even now. Its early look at the Pleiades puts the cluster back in the range of 440 light-years — just as it was before space telescopes.

The difference doesn’t mean much to casual skywatchers. But it’s crucial to astronomers. They use clusters like the Pleiades to study how stars evolve. To do so, they need to know how far away the stars are, which reveals how bright they are — a key measurement in understanding the stars.

Script by Damond Benningfield

Until 1845, almost no one had seen the Sun as anything other than a bright disk in the daytime sky. A few astronomers had looked at it with special telescopes, or traced its projected image on a piece of paper. But that was about it.

That changed 175 years ago today, when two French scientists snapped the first large photograph of the Sun. It was published in a book about astronomy, and later in other places — giving the world a close-up look at our star.

Armand Fizeau and Leon Foucault were young scientists fresh out of college. They were interested in the daguerreotype process — the first successful technique for taking photographs. It involved coating a copper plate with light-sensitive chemicals, exposing the plate, then using other chemicals to reveal the image.

Fizeau and Foucault refined the technique, then snapped a series of pictures of the Sun. Those images were tiny, though — the Sun was only about half an inch across — so they revealed almost no detail.

But on April 2nd of 1845, they took a much larger picture — the Sun measured about four and a half inches across. It showed two groups of sunspots, as well as some of the “bumpiness” on the Sun’s surface.

Fizeau and Foucault each spent a lot more time studying the Sun. And each of them used their observations to calculate the speed of light. They came up with numbers that were within a few percent of the true value — all from watching the Sun.

Script by Damond Benningfield

A possible moon in a distant star system wouldn’t be a good place for an evening stroll. If astronomers are right, its surface is covered with molten rock, and giant volcanoes belch hot gas out into space.

The moon is in a system known as WASP-49, which is about 550 light-years away. The central star is about the same size, mass, and temperature as the Sun.

The star is orbited by a planet that’s as big as Jupiter, the giant of our own solar system, but only a third of Jupiter’s mass. It’s so puffed up in part because it’s quite close to the star — far closer than any of the planets in our own solar system.

Those details about the system are pretty well established. The moon, on the other hand, hasn’t been confirmed. Its existence is based on circumstantial evidence. That evidence includes a “doughnut” of sodium and potassium around the planet. A team of European researchers concluded that the material is too far out to come from the planet itself. Instead, they reported, it’s probably pumped into space by volcanoes on a hot moon.

Finding moons in other star systems is hard, though. Astronomers have discovered a couple of candidates, but not one has been confirmed. So it could take a while to confirm the presence of this possible moon.

Incidentally, the system is in Lepus, the hare, which is below the feet of Orion. WASP-49 is low in the southwest at nightfall. It’s far too faint, though, to see without a telescope.

Script by Damond Benningfield