StarDate

The space around a black hole can be busy. As gas funnels into a black hole, it can form a disk that’s heated to millions of degrees. And the spin of the disk and the black hole can create a strong magnetic field. The field can sculpt powerful “jets” that shoot gas from the disk into space at almost the speed of light.

Astronomers should learn more about that process with a space telescope that’s scheduled for launch this fall. It’s called IXPE — the Imaging X-Ray Polarimetry Explorer.

The craft will carry three telescopes that are sensitive to X-rays, which are produced by some of the most powerful objects and events in the universe. The telescopes will feed light to instruments that will detect X-rays that have been polarized — they move through space in sync, like members of a marching band. The X-rays can be polarized by magnetic fields, so studying them reveals how the fields align, how they’re created, and more.

The list of targets includes black holes large and small, plus the remnants of exploded stars. Among those remnants are magnetars. These tiny, ultra-dense corpses produce magnetic fields that are trillions of times stronger than Earth’s. IXPE should map those fields, helping scientists determine how magnetars are born, how they evolve, and how they affect the space around them.

IXPE isn’t the only space telescope being prepared for launch. We’ll talk about a much bigger one tomorrow.

Script by Damond Benningfield

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Two celestial lightshows will compete with each other this week — the full Moon and the Orionid meteor shower. And there’s no mystery about which one will win: It’s the Moon all the way.

The Orionids are streaks of light caused by debris from Comet Halley. When the comet passes near the Sun, some of the ice at its surface vaporizes. That releases particles of rock and dirt into space. They spread out along the comet’s path. Earth plows through this path every October. As it does so, some of the comet dust slams into the atmosphere at almost 150,000 miles per hour.

A grain’s plunge into the atmosphere creates friction. That heats and erodes it. It also creates a trail of plasma — a super-heated gas that glows. And that’s what we see when a meteor streaks across the sky.

The Orionids are expected to reach their peak in the wee hours of Thursday morning. Under dark skies, away from the pesky glow of city lights, the shower usually produces up to a dozen or so meteors per hour.

Unfortunately, though, the Moon will be full on Wednesday morning. It’s the Hunter’s Moon — the full Moon after the Harvest Moon.

When the meteor shower hits its peak on Thursday, the Moon will still be almost full. It’ll be nice and bright, and in view all night long. Its brilliant glare will overpower all but the brightest meteors — making the Moon the hands-down winner in the pre-dawn sky.

Tomorrow: Studying magnets among the stars.

Script by Damond Benningfield

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The astronomers who study black holes have a bit of a problem. They’ve discovered lots of black holes that are fairly small — up to a few dozen times the mass of the Sun. And they’ve discovered many others that are jumbo — millions or billions of times the mass of the Sun. But they’ve discovered few black holes between those sizes. It’s like finding a lot of chihuahuas and great Danes, but no terriers.

One possible mid-sized black hole is in the galaxy NGC 3319. It’s in Ursa Major, the great bear, which dips low across the northern sky on October evenings.

The galaxy is about 47 million light-years away — close as galaxies go. That makes it easy to study. Like our home galaxy, the Milky Way, it’s a barred spiral. It has a long, skinny bar of stars in the middle, with beautiful spiral arms trailing off the ends of the bar. It’s not quite as big as the Milky Way, and it’s fairly faint.

A few years ago, astronomers reported the discovery of an intermediate-mass black hole in the heart of the galaxy. A study this year said the black hole is about 30,000 to 100,000 times the mass of the Sun. By comparison, the black hole at the center of the Milky Way is more than four million times the Sun’s mass.

The possible black hole produces a lot of X-rays. The energy probably comes from super-hot gas falling into the black hole. But more astronomers need to confirm the discovery of this busy “terrier” among black holes.

Script by Damond Benningfield

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Five of the stars of the Big Dipper are kindred spirits. They move through the Milky Way Galaxy together, and they may even share a birthplace. And they have some fellow travelers in other constellations.

Together, the stars form the Ursa Major Moving Group. It’s a stream of a few dozen stars. The most prominent are five members of Ursa Major, the great bear. They form all but the tip of the handle and the outer edge of the bowl of the Big Dipper, which makes up the bear’s body and tail.

The stars in the group move through the galaxy in the same direction, and at about the same speed. That suggests they’re roughly bound together by their gravitational pull — or they were in the past. And they’re all about the same age — a few hundred million years. For stars, that’s quite young.

The members of the group also have about the same chemical composition. That could mean they were born from the same cloud of gas and dust. But a study a couple of years ago noted that many other stars of the same age have a similar make-up. So while the stars of the Ursa Major Moving Group may be kindred spirits, they may not be actual kin.

Look for the Big Dipper low in the northern sky at nightfall this month, roughly parallel to the horizon. Some of the other members of the moving group are in the adjoining constellations Draco, which is above the dipper, and Boötes, to the left of the dipper.

We’ll have more about Ursa Major tomorrow.

Script by Damond Benningfield

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Jupiter leads the Moon across the sky tonight like a dog on a leash. And it’s a dog with a big bite. The planet had a big influence on the formation of the other worlds of the solar system — perhaps even the Moon.

Jupiter is heavier than all the other planets and moons in the solar system combined. That gives it a strong gravitational pull. And that’s the key to its effect on other worlds.

When the solar system was young, Jupiter probably moved closer to the Sun, then back out again. Its gravity may have cleared out much of the planet-making material closer to the Sun. Studies say Jupiter could have pushed many asteroids out of the asteroid belt and stirred up the ones that remained, keeping them from forming a planet.

Jupiter also may have cleared out material in the region that was giving birth to Mars. That kept the planet small — about half the size of Earth.

And a recent study said that, although it’s unlikely, Jupiter could have helped create the Moon. It could have moved toward the Sun fairly quickly, pushing things around in the inner solar system. That could have caused a collision between Earth and another planet — perhaps one as big as the original Earth. The impact destroyed both planets. But the debris might have reassembled to form Earth and the Moon — part of the influence of a giant.

Jupiter stands to the upper right of the Moon at nightfall, and looks like a brilliant star.

Script by Damond Benningfield

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The early evening sky serves up a couple of nice matchups. One will disappear not long after the sky gets fully dark. But the other will stick around until after midnight.

The match-up that vanishes early consists of the planet Venus and the star Antares. Venus is the spectacular “evening star,” so you can’t miss it, even though it’s low in the sky as darkness falls. Antares — a true star — is to the left of Venus. It’s less than one percent as bright as Venus, but its pairing with the bright planet will help it stand out.

Venus and Antares will move a little closer together over the next couple of nights. They’ll be at their closest on Saturday, when Venus will pass over the top of Antares. After that, Venus will pull away, leaving the heart of the scorpion behind.

The other match-up is even easier to find. It’s the Moon and the planets Jupiter and Saturn — the giants of the solar system. Jupiter — the Sun’s biggest planet — stands to the upper left of the Moon, and is quite bright — only the Moon and Venus outshine it.

Saturn is a little farther to the upper right of the Moon. It’s not as bright as Jupiter, but still easy to find. All three bodies wheel low across the south during the night, and set after midnight, with Saturn leading the way.

The Moon will slide well to the east by tomorrow night, but will still form a nice grouping with the two bright planets. We’ll have more about that tomorrow.

Script by Damond Benningfield

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The Moon probably formed after Earth got a big whack. A body as big as Mars slammed into our planet, blasting molten rock and other debris into space. Much of this material then came together to form the Moon.

Many other bodies in the solar system have suffered big whacks of their own. Three likely examples are found among the more than 80 known moons of Saturn, which is close to the upper left of the Moon this evening and looks like a bright star.

Tethys is about 660 miles across. Its major feature is Odysseus Crater, which is more than a third of the diameter of the moon itself. The impact that gouged it was so powerful that it would have shattered a solid body. That suggests that Tethys was still partially molten when it got hit. That provided enough “cushion” to keep Tethys from flying apart.

Mimas is smaller than Tethys, but it has a crater of about the same proportions. Known as Herschel, it’s fresher and deeper than Odysseus. It makes the little moon look like a Star Wars death star.

Finally, Dione appears to have been spun halfway around its axis. It has more craters on its trailing hemisphere than on its leading hemisphere — just the opposite of what you’d expect. A possible explanation is that a good-sized impact spun it around. But it seems odd that Dione would have been turned precisely 180 degrees. So scientists are still looking into the history of this little moon that might have gotten a big whack.

Script by Damond Benningfield

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A spacecraft scheduled for launch as early as this week is designed to study two clumps of asteroids that have been trapped since the solar system was young. Its observations could provide new details on how the planets were born. It might also tell us about the origin of Earth’s organic compounds — the chemical building blocks of life.

The main targets for Lucy are Trojan asteroids. These chunks of ice and rock share the orbit of Jupiter, but they’re nowhere near the giant planet. One clump is 60 degrees ahead of Jupiter, the other 60 degrees behind. They’re held in place by the gravity of Jupiter and the Sun. And there could be millions of them.

Trojans probably are “leftovers” from the birth of the solar system. They contain the same materials that were incorporated into the planets, so studying them should tell scientists more about how the planets formed.

In addition, many Trojans contain organic compounds. Similar compounds could have been incorporated into the young Earth, so the Trojans could tell us more about the development of life on our planet — and the possibility of life on other worlds of the solar system.

Lucy is scheduled to fly past one asteroid in the asteroid belt, between the orbits of Mars and Jupiter. It’ll reach one group of Trojans in 2027, and eventually swing by five of its members. It’ll then skip past Earth, using our planet’s gravity to reach the other clump in 2033.

Script by Damond Benningfield

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One of the most extreme stars in the galaxy is extremely busy. Every few decades, it puffs out a giant blob of hot gas. The blob cools and condenses to form a cloud of dust. The cloud then passes in front of the star, making it look much fainter.

VY Canis Majoris is in Canis Major, the big dog, which is in the south at dawn this month. The constellation hosts the brightest star in the night sky, Sirius.

VY Canis Majoris is much fainter — to the eye, anyway. It’s actually one of the brighter stars in the entire Milky Way Galaxy — more than a quarter of a million times as bright as the Sun. The star also is about 1400 times wider than the Sun. If it took the Sun’s place, it would extend beyond the orbit of Jupiter, the fifth planet out. It’s also much more massive than the Sun.

We can’t see the star because of its activity. It’s late in life, in a phase where bubbles of gas as big as the Sun percolate toward the surface. When they reach the surface, some of the gas flies out into space. It eventually cools and forms a cloud of dark dust.

That appears to have happened at least four times in the last 250 years. Each time, the star grew much fainter. The most recent event has obscured the star so much that it’s too faint to see without a telescope.

This phase might not last long. Soon, VY Canis Majoris might get smaller and hotter. Eventually, it might collapse to form a black hole — a dark remnant of a mighty star.
 

Script by Damond Benningfield

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Neptune, the Sun’s most remote major planet, was discovered in September of 1846. And just 17 days later, British astronomer William Lassell discovered the planet’s biggest moon, Triton — 175 years ago today.

Triton is one of the most interesting moons in the solar system. It has a thin atmosphere and volcanic activity. And geysers of dark ice squirt up to five miles high, depositing material up to a hundred miles away.

Triton is a little smaller than our own moon. It’s the only major moon that orbits backwards — in the opposite direction from the rotation of its planet. And it’s the coldest major body yet measured in the solar system — colder even than Pluto, which is farther from the Sun.

Our only close look at Triton came from Voyager 2, which flew past it in 1989. Its pictures showed that Triton has a young surface. Instead of being scarred by ancient impact craters, it’s covered by young volcanic plains. Much of the surface looks like the skin of a cantaloupe.

Voyager also found that Triton has an atmosphere. It’s extremely thin, but it’s thick enough to support plumes from the geysers. The geysers may form as sunlight warms ices below a layer of frozen nitrogen. The ices expand, then burst through the nitrogen and climb high into the sky.

The gravity of nearby Neptune could heat frozen water below Triton’s surface, creating an ocean of liquid water — one more intriguing feature on this distant moon.
 

Script by Damond Benningfield

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