StarDate

The first living things to fly to the Moon and back weren’t astronauts, cosmonauts, or even chimpanzees. They were two tortoises, some flies, and some meal worms. They completed their trip 50 years ago today aboard Zond 5 — the first spacecraft to safely complete a round-trip to the Moon and back.

Zond 5 was a test of the hardware designed to send cosmonauts on a trip around the Moon, perhaps as early as the end of 1968. They wouldn’t land or enter orbit, but their flight would beat America to the Moon.

But things hadn’t been going well. The Zond 4 mission, in March, was off course as it returned to Earth, so it blew itself up. And a test rocket blew up on the launch pad in July.

Zond 5 took off on September 14th, 1968. It passed just 1200 miles above the lunar surface a few days later, then returned to Earth. Because of a failure in its guidance system, it made an uncomfortable re-entry, but capsule and passengers survived.

The CIA had learned about the Soviet lunar missions. It alerted NASA, which decided to send the second Apollo to orbit the Moon in December.

The Soviets kept working on their mission, which they’d pushed back to 1969. But the next unmanned test flight suffered serious problems. The cabin depressurized, and the parachute system failed, so the capsule crashed.

When Apollo 8 made its lunar-orbital mission as planned, the Soviets abandoned their plans for trips around the Moon. The Moon Race was all but over.

Script by Damond Benningfield

Fall arrives in the northern hemisphere this weekend. It’s the autumnal equinox — the point at which the Sun crosses the equator from north to south.

You probably noticed that we used two names for the season: fall and autumn. In the modern world, it’s the only season with more than one common name.

According to language experts, the season didn’t have any names until fairly recently. In fact, there wasn’t much of a concept of the season itself. In the western world, most cultures thought mainly of winter and summer — the two extremes. The transition periods between them received less attention.

By the 12th or 13th century, though, the word “harvest” first appeared as a name for the transition from summer to winter.

“Autumn” turned up a century or two later. It was adopted from a similar word in French, or from the even earlier Latin word “autumnus.” And the phrases “spring of the year” and “fall of the year” appeared a century or two after that — marking times of warmth and growth on one hand, and cold and decay on the other. Those phrases soon were shortened to just “spring” and “fall.”

Even then, there wasn’t much agreement on just what the fall season encompassed. It could start in August or September and end during November or December. A precise definition didn’t come along until we started relying on the positions of the Sun. So now, fall — or autumn — begins on the September equinox — coming up at 8:54 p.m. Central Time on Saturday.

Script by Damond Benningfield

A star system in the constellation Andromeda is always hoppin’. Its two stars interact with each other, triggering brilliant outbursts.

Z Andromedae consists of two stars locked in a mutual orbit. In fact, it’s the prototype of a broad class of binaries, known as symbiotes because they interact with each other.

One of the stars is a red giant — an old, bloated star that’s about a thousand times brighter than the Sun. The other is a white dwarf — the exposed core of a once-normal star. Unlike most white dwarfs, it’s “burning” a thin layer of hydrogen on its surface. Because of that, it’s also a thousand times brighter than the Sun.

Occasionally, though, Z Andromedae gets much brighter. What’s happening isn’t fully understood. But one scenario goes something like this.

The red giant spews a strong wind of charged particles. Some of the particles go into orbit around the white dwarf, forming a wide disk. Material in the inner part of the disk falls on the surface of the white dwarf.

Every decade or two, the wind gets thicker, perhaps because of higher magnetic activity on the giant star. That creates an outburst in the outer part of the disk. More material then falls on the white dwarf, stoking its nuclear fires and making it shine much brighter. That disrupts the inner part of the disk, creating high-speed “jets” of particles that shoot out into space.

All that activity causes the system to flare up — calling attention to this busy symbiote.

Script by Damond Benningfield

The Milky Way galaxy and its nearest big neighbor, the Andromeda galaxy, are like two children on a see-saw: They’re up and down.

Both are giant spiral galaxies. Andromeda is about two-and-a-half million light-years away, in the constellation Andromeda. Under dark skies, it’s just visible as a hazy smudge of light — the farthest object that most people can see with their eyes alone.

Over the last few decades, astronomers have measured the mass of the two galaxies many times. But they keep coming up with different answers for which is the heaviest — one goes up, the other comes down. Most efforts have given the nod to Andromeda. But a few have said its the Milky Way.

The problem is, it’s hard to measure either galaxy. We’re inside the Milky Way, so we can’t see the whole thing. And even though Andromeda is quite close, it requires a high degree of precision to measure its size and mass.

A recent study, by astronomers in Australia, measured the motions of some dying stars. From those motions, the team calculated how fast a star must move to escape the galaxy. That revealed the galaxy’s total mass — all of its stars, gas, and dark matter: about 800 billion times the mass of the Sun — quite similar to the Milky Way.

The study makes some assumptions about Andromeda, and there’s some wiggle room in its numbers. But if they’re right, then the Milky Way and Andromeda are equals — neither one up or down on the galactic see-saw.

Script by Damond Benningfield

One of the most elaborate stories in the night sky offers vanity, love, a big dose of adventure, and a Hollywood-style rescue.

The central character in the story is Andromeda, the princess. Her constellation is in the east and northeast as the sky gets dark on September nights. It’s not all that bright, but you can find it by looking to the lower left of the Great Square of Pegasus.

The myth says that Andromeda was the daughter of Cepheus and Cassiopeia, the king and queen of Ethiopia. Cassiopeia was beautiful but vain — she boasted that she was more beautiful than the sea nymphs. So they went to Poseidon, the god of the sea, in search of vengeance. He sent the monster Cetus to attack Ethiopia.

To appease the gods, Cepheus ordered Andromeda chained at the ocean’s edge as a sacrifice. At the last minute, though, Perseus saved the day. He flashed the head of Medusa at the monster, turning Cetus to stone.

The original story doesn’t include Pegasus, but modern versions do. They say that Perseus rode the winged horse when he fought Cetus — adding another player to a grand story in the stars.

Perseus is to the lower left of Andromeda during the evening. W-shaped Cassiopeia is to her upper left, with Cepheus farther in the same direction. Cetus is a couple of constellations to the lower right and rises a little later — a safe distance from the princess.

One of the treasures of Andromeda is the spiral galaxy M31; more about that tomorrow.

Script by Damond Benningfield

The jewels of the solar system may not have been in the family for long. Observations by the Cassini spacecraft suggest the rings of Saturn could have formed within the last couple of hundred million years.

For a long time, astronomers thought the rings formed at the same time as Saturn itself — about four and a half billion years ago. Over the last few decades, though, there have been indications that the rings are much younger.

The latest came during Cassini’s final months. By flying between Saturn and the inner edge of the rings, it found that the rings aren’t as massive as many had expected — there’s just not much to them. And it found that if the rings were very old, they should have been darkened by a steady “rain” of dust.

According to Cassini scientists, the fact that the rings are still quite bright means they could have formed as recently as a hundred million years ago. They could have been born when a passing comet or asteroid pulverized a small moon. Or the gravity of the Sun could have pushed two moons off track, causing them to ram together and destroying both of them.

Not everyone accepts the young age for the rings, though. So it probably will take a bit more study to solve the mystery of the age of Saturn’s rings.

Look for Saturn near the Moon the next couple of nights. It looks like a bright golden star to the left of the Moon tonight, and closer to the lower right of the Moon tomorrow night.

Script by Damond Benningfield

Antares is much more than just bright and beautiful. The orange heart of the scorpion is among the biggest and heaviest stars in the galaxy. And it’s the dominant member of a vast complex of stars, gas, and dust.

The complex is known as the Scorpius-Centaurus OB Association. It consists of three big clumps. Each clump contains thousands of stars, of all sizes. But the clumps are dominated by classes O and B — hence the association’s name. These are the hottest, brightest, and most massive of all stars, shining blue and white. They burn out in a hurry, so they die young. Many of them explode as supernovae.

The clumps range in age from about 10 million to 17 million years. Each one consists of several smaller groups of stars that were born together.

The earliest groups may have helped give birth to later groups. Strong winds from the hot, young stars, along with shock waves from the supernovae, could have squeezed nearby clouds of gas and dust. That would have caused the clouds to break into smaller clumps, which then collapsed to form stars.

Antares was born as a class O star. But it’s nearing the end of its life. As a result, it’s puffed up to gigantic proportions. That’s caused its outer layers to get cool and red, so now it’s class “M.” Even so, it’s still the most impressive member of an impressive collection of stars.

Look for Antares directly below the Moon as darkness falls — an orange supergiant at the heart of Scorpius.

Script by Damond Benningfield

What jiggles the universe, briefly outshines a whole galaxy of stars, and leaves both sparkly and dark remnants? The answer appears to be the merger of two neutron stars — the ultra-dense corpses of once mighty stars.

Astronomers observed such a merger late last year. It produced an outburst of gravitational waves, which “jiggled” space and time. Special observatories detected those waves, which produced a quick “chirp.” Less than two seconds later, telescopes in space and on the ground also saw the merger, as dazzling outbursts of X-rays and other forms of energy.

Continued observations showed that debris from the merger contained huge amounts of gold, silver, and similar elements — enough to make several planets as massive as Earth. That suggests that most of those elements are produced by such mergers.

And one study concluded that the merger produced a black hole. It’s the smallest yet seen, at about 2.7 times the mass of the Sun.

The study team observed the merger with Chandra X-Ray Observatory, a space telescope. If the merger had produced a heavy neutron star instead of a black hole, the star should have produced far more X-rays than the telescope saw. Instead, the X-rays probably were produced as debris from the outburst rammed into gas and dust around the merged stars.

More observations over the next couple of years should settle the question — perhaps confirming the birth of a black hole.

Script by Damond Benningfield

Jupiter is the biggest, heaviest planet in the solar system. It’s about 11 times the diameter of Earth, and it’s more massive than all the other planets and moons combined.

Jupiter is also the fastest planet — it takes less than 10 hours to make one full turn on its axis. That means the clouds at its equator rotate at about 28,000 miles per hour, compared to one thousand miles per hour here on Earth.

Actually, the top of Jupiter’s atmosphere rotates at different rates. The clouds near the poles are a bit faster than those at the equator. But once you drop about 2,000 miles below the clouds, the rest of the planet all spins at about the same rate.

A recent study came up with a model to explain Jupiter’s high-speed rotation. It says that, as Jupiter formed, a strong magnetic field actually acted as a brake for a while. That slowed the planet down and kept it from spinning so fast that it flew apart.

After about 25,000 years, though, Jupiter began to speed up. It pulled in vast amounts of hydrogen and helium. As the material fell inward, it transferred momentum to the planet. Later, Jupiter’s own gravity caused the planet to shrink. Like a skater pulling in his arms, that sped up the rotation — just about matching what we see today.

And Jupiter is in great view tonight. The planet is quite close below or to the lower left of the crescent Moon as darkness falls — a giant world spinning through the solar system.

Script by Damond Benningfield

The Moon forms a beautiful triangle with two brilliant planets this evening. Venus, the “evening star,” is close to the lower left of the Moon, with fainter Jupiter farther to the upper left.

The gravitational influence of the two planets may play a big role in changes in Earth’s orbit. Their pull is stronger than those of the other planets because Venus is our closest neighbor, while Jupiter is the heaviest planet in the solar system.

Their combined pull may cause Earth’s orbit to change over a period of about 400,000 years. At one extreme in that cycle, the orbit would be almost circular, with little variation in our distance from the Sun. At the other extreme, the orbit would be more stretched out, so our distance from the Sun would vary by about 10 million miles. Today, we’re between those extremes, with the distance varying by three million miles.

Scientists recently found new evidence of this cycle in rock cores from Arizona. Previous studies had found similar evidence in other locations. But the new study had better evidence, and extended the record back to more than 200 million years ago.

Scientists say the variations in Earth’s orbit would magnify the effects of smaller climate cycles. Wet periods would get wetter, for example, or cold periods colder. And the variations could have caused a delay in the time it took the dinosaurs to become the dominant life on Earth — variations pumped up by two bright planets.

Script by Damond Benningfield