StarDate

Carbon is the second-most-abundant element in the human body. In fact, it’s the element that makes life on Earth possible. And every single atom of it was produced in the heart of a dying star.

For most of its life, a star shines by “burning” the hydrogen in its core. It fuses the atoms together to make helium, releasing energy in the process.

As the star uses up the hydrogen, its core gets smaller and hotter. Eventually, the temperature reaches a couple of hundred million degrees Fahrenheit — several times the present-day temperature in the heart of the Sun. At that temperature, helium atoms fuse together to produce carbon.

As that happens, the star’s outer layers expand and cool, turning the star into a red giant. A conveyor-belt process dredges material from the core — including carbon. Powerful “winds” blow some of that material out into space.

Later, nuclear fusion in the core shuts down. The core collapses to form a white dwarf. And the star’s outer layers are expelled into space. Carbon and other elements in those layers fly out into the galaxy, where they can be incorporated into new stars, planets — and perhaps living organisms.

One star that will add to the carbon supply soon is Aldebaran, the eye of Taurus, the bull. The bright orange star rises just below the last-quarter Moon, after midnight. It’s already a red giant, and it’ll begin making carbon before long — a key ingredient for life as we know it.
 

Script by Damond Benningfield

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One of the signs that autumn is nigh is the appearance of Pegasus in the evening sky. It’s low in the east as night falls. Its most prominent feature is the Great Square — four moderately bright stars that outline the body of the flying horse.

The brightest of the four is Alpheratz, at the lower left corner of the square in early evening. The star at the opposite corner is Markab — from an Arabic name that means “the shoulder of the horse.”

Astronomers have been a little confused about Markab. They know that it’s bigger, heavier, and much brighter than the Sun. They also know that it’s around the end of its “normal” lifetime — the long span when it fuses the hydrogen in its core to make helium.

At the end of that phase, a star begins fusing the hydrogen in a thin shell around the core. The core shrinks and gets hotter. That eventually ignites fusion in the helium. As those changes take place, the star’s outer layers expand and cool, turning the star from a “dwarf” to a “giant.”

And that’s where the confusion about Markab has come in. Researchers have classified the star in different ways. The most recent work says it’s at the end of its main phase of life. Some older studies have said it’s just moving into the next phase, as a sub-giant. And still others have put it in the full-on giant phase.

Regardless of which one is correct, there’s no doubt that big changes are taking place in the shoulder of the flying horse.
 

Script by Damond Benningfield

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On the first day of the 19th century, Giuseppi Piazzi discovered a new body orbiting the Sun. He named it Ceres, after a goddess of grain. He thought it might be a planet. Instead, it was the first member of the asteroid belt — a band of debris between Mars and Jupiter.

Piazzi’s discovery opened a new realm in the solar system. It was an important finding. And it made him famous not only in the field of astronomy, but to the rest of the world as well. In fact, the people of his home town, in Italy, dedicated a statue of him 150 years ago today — 70 years after his discovery.

Statues and sculptures of astronomers are rare, but there are a few.

Nicolaus Copernicus, who demonstrated that Earth is not the center of the universe, is displayed in Warsaw and Chicago, among other locations. Galileo Galilei, who provided some of the proof of Copernicus’ idea, can be found in Florence, Oxford, and elsewhere. And both of them are on a monument at the Griffith Observatory in Los Angeles, along with four other giants of astronomy — one of whom was sculpted by the artist who created the Oscar statuette.

The brother-and-sister team of William and Caroline Herschel, from the 18th and 19th centuries, are found in the garden of their home in England. And a statue of Benjamin Banneker, the first African-American to publish astronomical works, resides in Washington, D.C. — a rare acknowledgment for an astronomer.
 

Script by Damond Benningfield

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In the summer of 1946, Harvey Nininger packed his family and his meteorites and headed west — or farther west. He moved from Denver to a sandstone-brick house on Route 66, near the Barringer Meteor Crater in Arizona — the most impressive crater on Earth. And he set up the first museum dedicated to space rocks: the American Meteorite Museum.

Nininger was the leader in the collection and study of meteorites. He’d been teaching biology at a college in Kansas when he saw a bright meteor in 1923. It inspired him to change careers. There were no jobs in the field, though, so he struck off on his own. By 1946, he’d gathered thousands of meteorites. And he’d studied their composition, formation, and more.

His collection had been housed in Denver. But, at age 59, he decided to move to Arizona, where he could study the crater. At the time, not everyone agreed it was the result of an impact — some said it was formed by a volcanic eruption. Nininger’s work supported the impact theory.

Thousands of visitors stopped by his museum. He charged a small admission fee and sold meteorites. A couple of years later, though, the road was moved, so business plummeted.

At the same time, relations with the owners of the crater soured. So Nininger moved away, then sold his collection. Today, his museum is a crumbled ruin off the road to the crater — the home of the first meteorite museum, established 75 years ago.
 

Script by Damond Benningfield

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The seasons on Mars are like exaggerated versions of those on Earth. They have the same cause: their planet’s tilt on its axis. And they have the same cadence: summer in the northern hemisphere is longer than summer in the south. But they’re a whole lot longer.

Today marks the start of northern summer on Mars. It will last 183 Earth days. By comparison, southern summer lasts only 158 Earth days.

Both Earth and Mars are tilted at an angle of about 23 degrees. So as they orbit the Sun, their poles take turns dipping toward the Sun. It’s summer for the hemisphere that nods toward the Sun, and winter for the hemisphere that tilts away from it.

Earth and Mars follow stretched out orbits. Each planet is closest to the Sun in northern summer, and farthest during southern summer. A planet moves more slowly when it’s farther from the Sun, stretching the season that’s in progress then: in this case, northern summer.

One difference between the seasons on Earth and Mars is that Mars’s orbit is much more lopsided, so there’s a much bigger swing in seasonal temperatures. On Mars, summers in the northern hemisphere are cooler than those in the south. And northern winters are much warmer. So if you’re looking for more temperate conditions on Mars, the northern hemisphere is the place to be.

Mars is lost in the Sun’s glare now. It’ll pass behind the Sun in October, then return to view in the dawn sky around Thanksgiving.
 

Script by Damond Benningfield

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You might think it’s not possible for a star to be too bright for astronomers. After all, they’re always developing new telescopes and instruments to bring in more light from the stars. But a few stars are too bright for some telescopes.

An example is Deneb, the leading light of Cygnus, the swan. It’s too bright for Gaia, a space telescope. Gaia’s detectors are designed to plot the locations and motions of more than a billion stars. Most of those stars are far and faint. Deneb is brilliant by comparison, so it would overwhelm Gaia’s detectors.

That’s too bad, because astronomers would really like to know Deneb’s distance. It’s one of the biggest, brightest, and heaviest stars in our region of the galaxy. And it’s likely to end its life as a supernova — a blast that’ll rip the star to bits. But without a precise distance, all the other numbers are wobbly.

Estimates put the distance at roughly 1500 to 3,000 light-years. At the larger distance, it would have to be much bigger and brighter to look so bright in our sky.

The best numbers say Deneb is about 20 times the mass of the Sun and 200 times the Sun’s diameter. That puts the star at up to 200 thousand times the Sun’s brightness — enough light to overwhelm a telescope.

Deneb is high in the east-northeast at nightfall. It marks one point of the Summer Triangle. It’s below the triangle’s brightest star, Vega — a remote but brilliant light for summer nights.

Script by Damond Benningfield

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If you don’t like long silences, you probably don’t want to get involved in the Voyager missions. The two probes are so far away that it takes a day and a half or longer to send a message to them and get a response.

Both craft were launched in the summer of 1977. And both of them flew past the planets Jupiter and Saturn. Voyager 2 then flew past Uranus and Neptune. And it’s still the only spacecraft to visit either of those worlds.

After that, the Voyagers just kept on going. And within the last decade, they’ve reached interstellar space — outside the Sun’s “bubble” of influence.

The craft are still operating. Voyager 1 is more than 14 billion miles away. At that range, it takes about 42 hours and 20 minutes to send it a message and receive a reply. Voyager 2 is less than 12 billion miles, so NASA hears from it in a bit more than 35 hours.

Several of their instruments are still working. So they beam us information on conditions in the region between stars. The signals are so weak that it takes NASA’s largest tracking antennas — 230 feet in diameter — to hear them.

And the signals keep getting weaker. In part, that’s because of the increasing distance. But it’s also because the plutonium that powers them is decaying. Within a few years, the craft won’t produce enough energy to operate their transmitters. So the Voyagers will go silent — half a century after leaving Earth.
 

Script by Damond Benningfield

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An old friend is rising into view in the early morning sky, as it does every year at this time. It’s so bright that it’s easy to spot even through the light of the bright Moon.

Orion the hunter climbs into good view in the eastern sky by about 4:30 or 5. Look for its “belt” of three stars. They form a short line that points up from the horizon.

The belt is surrounded by a tilted box of four stars. Bright orange Betelgeuse is at one corner of the box, to the left of the belt. Blue-white Rigel is at the opposite corner of the box, to the right of the belt.

Like all the stars in the night sky, those of Orion rise about four minutes earlier each night. Orion pops into good view in the morning sky in late July and early August, and rises earlier day by day. By November, it’ll rise before midnight. And by Christmas, the hunter will be in view all night.

The change is caused by Earth’s motion around the Sun. It takes our planet 23 hours and 56 minutes to make one turn relative to the background of stars. In other words, if you look at a specific star, it’ll appear in the same spot in the sky every 23 hours and 56 minutes.

But it takes an extra four minutes for the Sun to return to the same spot in the sky. So our viewing angle on the background stars moves a bit as a result. That causes the stars to rise and set four minutes earlier each day — allowing them to slowly drift through the seasons.
 

Script by Damond Benningfield

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Jupiter, the Sun’s largest planet, doesn’t have a solid surface. So we won’t find any critters walking or crawling across it. But it’s not out of the question that life could exist in the outer atmosphere — especially microscopic life.

Jupiter is a big ball of gas. The gases get hotter and denser as you drop deeper into the planet. In the top few hundred miles, though, conditions could be acceptable for life.

45 years ago, astronomers Carl Sagan and Edwin Salpeter suggested that a whole ecosystem might inhabit that zone, in and around Jupiter’s massive clouds. They envisioned miles-wide “floaters” — gas-filled bags that look like jellyfish. And they suggested that nimble “hunters” might prey on the floaters — like sharks eating other fish in the oceans.

Today, large organisms are considered highly unlikely. Among other problems, the atmosphere is so turbulent that it would push them too high or too low to survive.

Yet it’s possible that microbes could live in the atmosphere. There’s a good supply of the chemistry needed for life. And sunlight and powerful lightning could supply the energy. So while it’s not likely, it is possible that we might someday find life on the solar system’s biggest planet.

And Jupiter is putting in a big appearance. It rises at sunset and is in view all night. It looks like a brilliant star, low in the east-southeast at nightfall. Tonight, it’s quite close to the full Moon.
 

Script by Damond Benningfield

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The Moon and two planets form a bright triangle tonight. Saturn is above the Moon as night falls, with brighter Jupiter farther to the left of the Moon.

These three bodies are a long way apart — they’re separated by hundreds of millions of miles. And there’s no shuttle service between them. Yet the Moon and some of the moons of the two planets may have traded a lot of stuff over the eons. So may many other planets and moons — including our own.

The exchange is powered by impacts — giant space rocks slamming into planets or moons. Such a collision blasts out huge amounts of debris. Some of it moves fast enough to escape into space. And over time, bits of the debris settle on the other worlds. Here on Earth, for example, we’ve found confirmed pieces of Mars, the Moon, and some asteroids. And scientists suspect they’ve found pieces of other worlds as well.

Spacecraft traveling to Mars and other planets and moons are sterilized to prevent them from carrying microorganisms. And samples from those other worlds are isolated for a while to protect us from deadly bugs. But some scientists argue that the regular exchange means we shouldn’t worry too much about that. They say that pieces are shooting back and forth all the time — and have been for billions of years.

Still, the policies on protecting the worlds of the solar system from each other aren’t likely to change anytime soon.

More about the Moon and Jupiter tomorrow.
 

Script by Damond Benningfield

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