StarDate

Legend says that in centuries past, Scandinavian sailors plying the frigid waters between Norway and Iceland kept a close lookout for a monster from the deep: the kraken. It was said to be big enough to swallow men and ships alike.

Sailors may not find such a creature in the largest sea on the largest moon of Saturn — the Kraken Sea. But there’s plenty of room for it to hide in. Parts of the sea may be more than a thousand feet deep.

The Kraken Sea is on Titan, a world that’s half-again the size of our moon. It’s blanketed by a cold, thick atmosphere that’s topped by an organic haze. Liquid fills rivers, lakes, and seas on its surface — liquid hydrocarbons.

The Kraken Sea covers an area that’s about twice the size of all the Great Lakes combined. As the Cassini spacecraft neared the end of its mission a few years ago, scientists used its radar to peer through Titan’s haze and map the sea. They revealed the results of that scan a few months ago.

The beam reflected from both the surface and the bottom of the sea. The timing, and the way the beam was reflected, showed that the sea is mostly methane, chilled to 300 degrees below zero. And it revealed the depth of the sea: up to a thousand feet or more — a perfect place to hide a sea monster.

Saturn stands to the upper left of our moon at first light tomorrow. It looks like a bright golden star. Brighter Jupiter is off to their left. More about the giant planets tomorrow.

Script by Damond Benningfield

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A star system that flares up every couple of decades may be headed for an even brighter outburst by the end of the century.

MWC 560 is a binary system — two stars bound by their mutual gravity. One of them is a white dwarf — the hot, dead core of a once-normal star. Its companion is a red giant — an old, bloated star that’s on track to become a white dwarf itself.

The white dwarf “steals” gas from the companion. That forms a wide, hot disk around the white dwarf. Magnetic fields grab some of the gas and shoot it out into space in high-speed jets. One of those jets aims directly at Earth, giving astronomers a good look at what’s going on.

The system has flared up several times since it was discovered, most recently in 2016. The outbursts are powered by eruptions from the disk. The flow of gas from the red giant gets too thick for the disk to handle, so it erupts, spewing particles and energy into space.

After each outburst, the system stays a little brighter than it was after the previous one. That could mean that the disk is getting a little heavier. That’s led astronomers to speculate that the system could stage an even bigger eruption in a few decades. It might blast away the entire disk. That would form a nova — making the system shine tens of thousands of times brighter.

MWC 560 is in Monoceros, the unicorn. The constellation is in the south and southwest at nightfall, to the upper left of Orion’s Belt.

Script by Damond Benningfield

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Astronomy is planning ahead. Committees of the National Academy of Sciences are taking a look at big-ticket projects for the next decade and beyond. Their recommendations to NASA will help outline the agency’s priorities for a long time to come.

The work is mandated by Congress. Reviewers look at key scientific questions that need to be addressed, and how NASA can tackle those questions. Different panels look at different subject areas.

One, for example, is evaluating proposals for exploring the solar system. The last survey in that area was completed in 2011. Among its top priorities were a mission to Jupiter’s moon Europa, plus another to bring back samples from Mars. Both of those projects received a go-ahead from NASA.

This time around, the proposals include one that would study Enceladus, one of the moons of Saturn. An ocean below its crust appears to have all the ingredients needed for life.

Another proposed mission would put a craft in orbit around Titan, Saturn’s biggest moon. The craft would drop small probes to the surface, which is blanketed by a dense atmosphere made of hydrocarbons. And yet another mission would send an orbiter and probe to study Neptune and its biggest moon, Triton.

These and other missions would cost billions of dollars each. So evaluators will take a close look at each one before making their recommendations next year — helping astronomy plan for the next decade and beyond.

Script by Damond Benningfield

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When Comet Halley blazed across the night sky in 1910, many people tried to hide from it. They feared it might bring poisonous gases or plain old bad luck. But Nicholas Bobrovnikoff couldn’t get enough of it. The teenager watched the comet from his native Russia. And his interest led to a career in astronomy — and a new life in the United States.

Bobrovnikoff was born 125 years ago today. He first studied mining, then joined the Russian infantry, in 1917. When civil war broke out, he became an officer in the Russian White army. He was severely wounded during the war, and suffered from typhus.

When his side lost to the Red army, he escaped to Cyprus and resumed his studies — this time in astronomy. And in 1924, he was offered a position with the University of Chicago astronomy program. Its director, Edwin Frost, had already brought another former Russian officer to Chicago: Otto Struve, who later became the first director of McDonald Observatory.

In the U.S., Bobrovnikoff studied comets. In particular, he gathered every scrap he could find on Halley’s comet — hundreds of photographs and piles of other data. And in 1930, he published a 177-page report — the most extensive report on a single comet anyone had ever done.

Later, Bobrovnikoff spent two decades as director of Perkins Observatory in Ohio. And in 1986, he got to see Halley’s Comet once again — a beautiful iceball that sparked a career in astronomy.

Script by Damond Benningfield

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Compared to most of the stars in the galaxy, our Sun is a giant. It’s bigger and heavier than perhaps 90 percent of the stars in the Milky Way. It’s so big that you could fit more than a million Earths inside it.

Yet when it’s compared to some of the biggest stars of all, the Sun is a mere bit of cosmic flotsam — like a BB compared to a bowling ball.

A prime example is Antares, the leading light of Scorpius. The bright orange star is close to the lower right of the Moon as they climb into good view by midnight, and directly below the Moon at first light.

Antares is at least 15 times as massive as the Sun. That great heft squeezes its core far more tightly than the core of the Sun. That boosts the core’s temperature, which revs up the nuclear reactions that power the star. The radiation from those reactions pushes outward, making the star’s outer layers puff up like a giant hot-air balloon.

The result of all of this is that Antares is hundreds of times wider than the Sun. In fact, if it took the Sun’s place in our own solar system, it would extend beyond the asteroid belt, engulfing Earth and the other inner planets.

That’s an astounding volume of space — more than 100 septillion cubic miles — a one followed by 26 zeroes. Or to look at it another way, this supergiant star is big enough to swallow several hundred million Suns — a monster star on any scale.

Script by Damond Benningfield

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IC 1101 is the king of the mega-merger. It’s not listed on any stock exchange, though. Instead, it appears to be the biggest galaxy yet seen — a monster that makes the Milky Way look puny by comparison.

All big galaxies get big through a series of mergers. At first, the merging galaxies are fairly small but busy — they’re giving birth to many new stars. As a galaxy grows, however, most of the mergers become one-sided — a big galaxy takes over a smaller one. The Milky Way, for example, probably has gobbled up dozens of small galaxies over the eons.

But a few of the mergers are major — both of the galaxies are big. And that seems to be the case with IC 1101. A study a few years ago suggested that it’s undergone 10 to 20 mergers with other big galaxies.

And that’s made it huge. Its “halo” of gas and old stars may span five million light-years — several times the size of the Milky Way. And the galaxy tips the scales at many times the mass of the Milky Way.

At least part of the galaxy appears to be below average, though. Its middle has far fewer stars than expected for such a giant. And that, too, may be a result of its mergers. Each galaxy involved in the big mergers had a supermassive black hole at its heart. The black holes spiraled around each other, then they merged as well. But the motions of the black holes may have kicked out many of the stars in the center of IC 1101 — a “light-hearted” monster of a galaxy.

Script by Damond Benningfield

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The two smallest, faintest galaxies yet seen are companions of our home galaxy, the Milky Way. And both of them are cosmic fossils — they’ve changed very little since they were born back when the universe was young.

Segue 1 and 2 were discovered more than a decade ago. They’re named for the project that found them.

Both galaxies are about half a million times as massive as the Sun, with Segue 1 slightly heavier than 2. Yet each galaxy contains no more than about a thousand stars. Segue 1, in fact, shines only about 300 times brighter than the Sun — far fainter than some individual stars in the Milky Way. That suggests that both galaxies consist mainly of dark matter. It doesn’t produce any energy, but its gravity pulls on the normal matter around it.

The few stars in the galaxies appear to be at least 12 billion years old — almost three times the age of the Sun. They formed when the universe was less than two billion years old. And nothing much has happened in either galaxy since then.

Something may have happened to the galaxies, though: They entered the influence of the Milky Way. There’s evidence that the galaxies were born on their own. But billions of years ago they wandered close to the Milky Way — and were captured by its powerful gravity.

Segue 1 is in Leo, the lion, which springs high across the south on April nights. Segue 2 is in Aries, which hides in the Sun’s glare for the next few weeks.

Script by Damond Benningfield

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The second-biggest storm on Jupiter has an amazing history. It formed from the merger of three smaller storms. It turned bright red a few years later, then faded to white. And it’s survived several close encounters with Jupiter’s biggest storm.

Oval BA started forming in 1998, when two storms merged. A third joined with them two years later. The combined storm is more than half the size of Earth. Its winds spiral in the opposite direction from hurricanes here on Earth, at speeds that are up to twice as fast.

In 2005, Oval BA turned red. Since Jupiter’s biggest storm is the Great Red Spot, scientists began calling the smaller one the Little Red Spot or Red Junior. But while the great spot has stayed red for more than a century and a half, Red Junior soon began fading. By a few years ago, it had turned white. And scientists are still trying to figure out what caused both of its color changes.

Oval BA passes just south of the Great Red Spot every couple of years. During an early encounter, scientists thought the great spot might gobble up the smaller storm. Instead, though, it’s survived every encounter, including one last summer — continuing its travels through Jupiter’s amazing atmosphere.

Jupiter is low in the southeast at first light now. The solar system’s biggest planet looks like a brilliant star. The Great Red Spot is easy to spot through small telescopes, but Oval BA takes a bit more work.

Script by Damond Benningfield

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Here on Earth, storm systems come and go over a period of days or weeks. On other planets, though, they can last a lot longer. But they can change dramatically.

The best example is the Great Red Spot, on Jupiter, the giant of the solar system. The storm has been around for at least a century and a half, and perhaps a lot longer. In the last few decades, though, it’s gotten smaller — a process that’s picking up speed.

The Great Red Spot is an anticyclone — a high-pressure system. It spins in the opposite direction from hurricanes, which are low-pressure systems.

When first seen, the oval storm spanned about three times the width of Earth from east to west. By 1980, it had dropped to about half that size. And since then, its width has dropped another 40 percent — including 20 percent in just the last decade.

A recent study found that winds on the storm’s edge appear to have increased by five to ten percent — topping out at hundreds of miles per hour.

The results are still being verified. But they suggest that the Great Red Spot could be getting more intense. That could cause it to spin faster, the way a skater spins faster as it pulls in its arms. So in the coming years, the storm could get smaller but more powerful — with an uncertain fate at the end of that process.

We’ll talk about another storm on Jupiter tomorrow. In the meantime, look for Jupiter low in the southeast at first light. It looks like a brilliant star.

Script by Damond Benningfield

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The universe was born in the Big Bang — a single moment in which matter, energy, and even space and time sprang into existence. And in recent decades, scientists have been zeroing in on just when the Big Bang took place. Their conclusion: about 13.8 billion years ago.

Several lines of evidence support that age.

One is the rate at which the universe is expanding as a result of the Big Bang — and how that rate has changed over time. If you know how fast things are moving apart, then you can “rewind” the clock and figure out when they started moving apart. Measuring the expansion rate isn’t easy, though. And astronomers still aren’t in full agreement on what the rate really is.

Another line of evidence is the ages of stars. The oldest stars were born at least 13 billion years ago. So the universe must be older than that.

And yet another bit of evidence is the chemistry of the universe. The Big Bang created hydrogen and helium, plus a tiny smattering of a couple of other elements. Everything else was forged in the hearts of stars. Astronomers know how quickly that happens. So they can calculate how long it should take to build up the amounts of oxygen, carbon, and other elements we see in the present-day universe. And the result lines up well with the other lines of evidence.

Together, these and other bits of evidence tell us that the universe is about 13.8 billion years old.

Script by Damond Benningfield

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