StarDate

Planetary scientists caused a bit of a stir last year when they reported finding phosphine in the atmosphere of Venus. Here on Earth, the compound is produced only by living organisms or in the lab. So the finding suggested that microbes could be living in Venus’s clouds.

Later reports have cast doubt on the finding. But no one is giving up on the possibility that microbes might inhabit the clouds.

The surface of Venus isn’t a nice place. It’s hot enough to melt lead, and the pressure is like being at a depth of two-thirds of a mile in Earth’s oceans.

And at first glance, the clouds don’t sound much better — they’re made of sulfuric acid. Yet there’s a layer in the clouds where the temperature and pressure could be comfortable for life. And orbiting spacecraft have detected a possible hint of life within that layer.

One recent study said that microbes could be protected inside droplets of sulfuric acid mixed with water. When the droplets get heavy enough, they’d drop to lower altitudes and evaporate. The microbes would dry out and shut down. Eventually, though, they’d be mixed back up into the clouds, where they’d be encased in new droplets — restoring them to life.

It’ll take new missions to the planet to settle the question of whether anything is living in Venus’s clouds.

And Venus is in the early evening sky right now. Its clouds make it shine brilliantly as the “evening star.” Tonight, it’s next to the crescent Moon.

Script by Damond Benningfield

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Few sights are more relaxing than a field of stars twinkling through a dark night sky — at least for most of us. For astronomers, “twinkling” just makes life harder. It blurs the light of distant stars and galaxies. So instead of a sharp pinpoint of light, a telescope sees a star as a fuzzy blob.

Astronomers have developed some techniques to sharpen the view. They use small mirrors that move to compensate for the shifting light coming from a bright star in the telescope’s field of view, for example.

Such techniques have improved the view dramatically. But they have some drawbacks. So a team of astronomers has proposed a new way to sharpen the view: with lasers aboard small satellites.

The team is led by John Mather. He’s a Nobel Prize winner, and chief scientist for the next big space telescope. The team proposes launching one or more small, inexpensive satellites. The satellites would follow orbits that could keep them in view of a single telescope for hours — or even permanently.

A satellite would beam a laser toward the telescope. An improved set of mirrors would bring that beam to a sharp focus. That would sharpen the telescope’s entire field of view. The technique could be especially valuable for a new generation of giant telescopes.

The team says the system could be developed fairly quickly and inexpensively — allowing telescopes on the ground to see the universe as clearly as those in space.
 

Script by Damond Benningfield

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A “ring of fire” will pass across the top of the world early tomorrow — an annular solar eclipse. It occurs as the new Moon crosses between Earth and the Sun, so the shadow of the Moon passes across our planet. A partial eclipse will be visible across a wedge of the United States.

An annular eclipse takes place when the Moon is a little farther from Earth than average. That makes it appear a little smaller than average, so it’s not quite wide enough to cover the entire solar disk, as it does during a total eclipse. As a result, a bright “ring of fire” surrounds the intervening Moon. For this eclipse, the Moon will cover almost 90 percent of the Sun.

The annular eclipse begins over southern Ontario at 5:50 a.m. local time. The lunar shadow will move northwestward, then curl over the north pole before disappearing over Siberia. The path of the annular eclipse will be up to about 330 miles wide. And the Moon will remain encircled by the Sun for a maximum of less than four minutes.

A partial eclipse will cover a wider area, with the Moon covering at least a fraction of the Sun. This portion of the eclipse will be visible as the Sun rises over roughly the northeastern third of the United States. The Sun will be too bright to look at directly, though, so use eclipse glasses or other safe screening to protect your eyes. Or you can watch the entire event online.

Tomorrow: a telescope that’s on the ground and in space.
 

Script by Damond Benningfield

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NGC 7027 is blowing itself apart. A dying star has ejected its outer layers into space, surrounding itself with a colorful cocoon of gas and dust. That’s earned the nebula a nickname: the Jewel Bug, after a small insect with a beautiful shell. But the nebula won’t last long. It’s expanding into space. And it’s being eroded by jets of gas from the star.

NGC 7027 is about 3,000 light-years away, in Cygnus. As night falls it’s low in the northeast, below Deneb, the swan’s brightest star.

When the star at the center of the nebula was born, it was several times the mass of the Sun. At the end of its life, the nuclear reactions in its core began to shut down. As a result, the star sloughed off shells of gas from its surface. The shells are expanding into space.

Then not much more than a thousand years ago as seen from Earth, the star began ejecting a lot more gas — and much faster — creating a thicker cloud. And high-speed “jets” of gas appear to be shooting away from the star, punching through everything else.

So today, the nebula looks like a series of rings around a pillow, with spikes from the pillow’s ends. A companion star may be helping to sculpt those shapes. But it’s also possible that the dying star has already swallowed the companion.

Before long, the dying star will shut down. It’ll become a white dwarf — a hot but tiny corpse. Its cocoon will drift away into space — and the Jewel Bug will disappear.
 

Script by Damond Benningfield

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Earth’s magnetic field is like a big bar magnet, with a north pole and a south pole. But Earth’s magnetic field does something no bar magnet ever does: it changes polarity — the north and south poles switch places.

The most recent flip began about 42,000 years ago, and lasted for a thousand years. Geologists have had a tough time nailing down the consequences of the change, though. In part, that’s because it’s hard to sync up the observations they’ve made in different parts of the world.

But the new study reports a way to calibrate all of that work. Researchers looked at rings in kauri trees from New Zealand. The trees were alive at the time of the field reversal, and lived for up to 1700 years. When they died, they were preserved in peat bogs. The trees allow scientists to compare the results of the tree-ring analysis with other studies.

Scientists examined each year’s rings for carbon-14 — a radioactive element that’s more abundant when the magnetic field weakens. They found that carbon-14 went way up as the field reversed — suggesting the field was much weaker.

The weaker field let in more cosmic rays — heavy particles from the galaxy. That could have led to an ice age, massive lightning storms, and even extinctions.

Earth’s magnetic field is overdue for another flip. That doesn’t mean we’ll see a reversal anytime soon. But when the next one happens, it could have some unhappy consequences.
 

Script by Damond Benningfield

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Watching Mars over the last few months has been like watching the taillight of a car disappearing slowly into the distance. Last October, it was the third-brightest object in the night sky — a brilliant orange beacon that was in view all night. But it’s been driving away from us ever since then. So now, it’s only about two percent as bright. It’s still easy to see, but it’s harder to separate from the distant traffic.

Mars is a bit easier to see the next few nights, though, because it lines up with two other lights that are roughly the same brightness: Pollux and Castor, the “twin” stars of Gemini.

Mars was so spectacular last fall because it was passing opposite the Sun in our sky, so it was quite close — less than 40 million miles away. Now, though, it’s on the other side of the Sun from us — more than 200 million miles away.

The extra distance accounts for most of the difference in brightness, but not all. When a planet is opposite the Sun, it reflects more of the sunlight that strikes it in our direction. Put the two factors together, and they add up to one thing: Mars is fading fast.

Look for it low in the west-northwest not long after sunset. It looks like a moderately bright star. The twins are to the right of Mars, with brighter Pollux closer to it. Mars will form an almost perfect line with them tomorrow and Tuesday. After that, the stars will drop away from Mars as the Red Planet slowly drives into the sunset.
 

Script by Damond Benningfield

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When you look at some of the bright stars in June’s evening sky, you’re seeing double. That’s because the stars are binaries — two stars bound by their mutual gravity. The list includes Antares, which is low in the southeast after nightfall; Spica, which is higher in the south; and Regulus, over in the west.

In fact, most of the stars in the galaxy are members of binaries. The stars in a binary were born together, from the same cloud of gas and dust, so they’re siblings. And it’s easier to measure the masses of binaries than single stars, so they’re popular targets for astronomers.

One recent study, for example, identified 1.3 million binaries within about 3,000 light-years of Earth — many times more systems than were known before.

They were found by Kareem El-Badry, a graduate student at UC-Berkeley. He sifted through observations from the Gaia space telescope. He was looking for binaries where the two stars are far apart — at least 10 times the distance from Earth to the Sun. It’s easier to see their individual stars than in systems where the stars are close together.

Many of the binaries include at least one white dwarf — the “corpse” of a once-normal star. It’s easier to measure the age of a white dwarf than other types of stars, which then reveals the age of the companion. Having the masses of the stars and other details helps astronomers understand how all stars evolve — a big advantage to seeing double.
 

Script by Damond Benningfield

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A dead star about 4500 light-years from Earth is blasting away its companion. Before long, the companion may disappear completely — the victim of a black widow.

The “dead” star is a pulsar — the crushed core of a once mighty star. It spins hundreds of times per second, beaming energy in our direction with each turn. That makes the star appear to “pulse” on and off.

Its companion is a small ball of gas — mainly helium. It’s only about eight times as heavy as Jupiter, the largest planet in the solar system — roughly a tenth of the minimum mass of a star.

The object may well have been a true star in the past. But it’s so close to the pulsar that the pulsar blasts away the former star’s outer layers. That makes the pulsar a “black widow” — a star that devours its mate. It’s the most extreme black widow yet seen.

The pulsar continues to erode the tiny companion today. Some of the gas falls onto the pulsar, making it heavier. In fact, it’s the most massive pulsar yet discovered — at least 2.1 times the mass of the Sun. The rest of the companion’s gas simply blows out into space — the remnants of a disappearing star.

The system is known as J1311-3430. It’s in Centaurus, the centaur, which is low in the south as night falls. Although the system is much too faint to see without a big telescope, you can pick out its location. It’s at the centaur’s northern edge, above one of its brighter stars, Iota Centaurus.
 

Script by Damond Benningfield

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The first black hole ever discovered has gotten bigger. In part, that’s because it’s pulling in gas from a companion. Mainly, though, it’s because astronomers recently found that it’s farther away than expected. That means it’s more massive than thought, too.

Cygnus X-1 was discovered by an X-ray detector lofted into space in 1964. In fact, its name indicates that it was the first source of X-rays discovered in the constellation Cygnus.

Over the years, astronomers figured out its true nature. It’s a binary — two objects bound by gravity. One of them is a hot, massive star. The other is a black hole — the corpse of a star that was more impressive than its companion. The black hole pulls gas from the companion, forming a disk around the black hole. The disk is extremely hot, so it emits a lot of energy — especially X-rays.

A team recently used an array of radio telescopes to measure the system. The team compared those observations to similar ones made a decade earlier. That produced the best measurement of the distance to Cygnus X-1: 7200 light-years.

From that, the team recalculated the system’s details. The companion is about 40 times the mass of the Sun, while the black hole is about 20 times the Sun’s mass — the heavy corpse of a once-mighty star.

Cygnus is low in the northeast at nightfall. Although Cygnus X-1 is too faint to see, it’s about half way between the swan’s bill and the intersection of its body and wings.

Script by Damond Benningfield

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A planet in the heart of M13, the Hercules Cluster, would never see the dark of night. The cluster contains hundreds of thousands of stars, all packed into a ball only about 150 light-years across. So while the Sun’s nearest neighbor is more than four light-years away, a star in M13 would have thousands of neighbors that were much closer. That means the night sky of a planet in the cluster would boast thousands of stars that are more brilliant than the brightest star in our own night sky.

M13 is in the constellation Hercules, which is well up in the east and northeast as night falls. Look for a lopsided square of four modestly bright stars known as the Keystone. M13 lies between the two stars at the top of the Keystone. Under especially dark skies, it’s just visible to the unaided eye as a faint, fuzzy star.

M13 is a globular cluster. Such clusters were born at the same time as the galaxy itself. So the stars in a globular are perhaps 12 billion years old or older — almost three times the age of the Sun.

Because of the cluster’s extreme age, there’s been plenty of time for life to develop there — including intelligent life. So more than 40 years ago, a team of scientists beamed a radio message toward the cluster — a greeting to any civilization there. Because of the cluster’s great distance, though, it’ll take a while to get there — about 25,000 years.

Tomorrow: a black hole gets heavier.

Script by Damond Benningfield

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