StarDate

The three brightest objects in the night sky team up during the early morning twilight tomorrow: the Moon and the planets Venus and Jupiter. Venus is the “morning star,” to the upper right of the Moon. Slightly fainter Jupiter is to the lower left of the Moon. It’s quite low, so you need a clear horizon to spot it.

Venus and Jupiter are siblings – they were born from the same disk of material around the newborn Sun. So were Earth and the solar system’s other planets. Besides their parentage, though, Venus and Jupiter don’t have a lot in common.

Venus is a ball of rock a little smaller than Earth. It’s topped by clouds of sulfuric acid. They reflect most of the sunlight that strikes them, which is one reason Venus is so bright.

Another is its proximity: Venus is the second planet from the Sun, while Earth is the third. So Venus passes closer to us than any other planet.

Because Venus and Earth formed so close to the Sun, they’re made mainly of rock and metal. The young Sun blew away most of the lighter materials – gas and ice. So Venus is dense and heavy.

Jupiter formed much farther from the Sun, where it was much colder. It built a big core of heavy materials, then swept up a lot of gas, dust, and ice. It became the largest planet in the solar system – a dozen times the diameter of Venus, and almost 400 times its mass – the “big brother” to the rest of the planets.

More tomorrow.

Script by Damond Benningfield

Since the start of the Space Age, we’ve learned a lot about the other planets of the solar system. But perhaps we’ve learned the most about Venus. That’s a bit of a surprise when you consider that Venus passes closer to Earth than any other planet.

Venus is the brilliant “morning star.” It lines up close to the crescent Moon before dawn the next couple of days.

Venus looks so bright in part because it’s blanketed by clouds that hide the surface. And that’s the main reason we’ve had so much to learn about the planet.

Without any landmarks to go by, astronomers couldn’t even tell the length of the planet’s day. They didn’t figure it out until the early 1960s. They used radio telescopes to bounce waves off the surface. The echoes revealed that a day on Venus lasts 243 Earth days.

For a long time, scientists thought the clouds were made of water vapor, just like the clouds on Earth. That led to speculation that Venus was warm and wet, with giant oceans and dense jungles. Instead, the clouds are made of sulfuric acid. And they hide a surface that’s hot enough to melt lead, with not a drop of water.

Today, planetary scientists are still learning about Venus. It appears to be volcanically active, for example – perhaps one of the most active worlds in the solar system. So, many more surprises could lurk below the clouds of our brilliant neighbor.

Script by Damond Benningfield

The Moon and the Seven Sisters huddle up in the wee hours of tomorrow morning. The Moon will “occult” the sisters – the brightest stars of the Pleiades star cluster. The stars form a tiny dipper that marks the shoulder of Taurus, the bull.

Occultations have been useful scientific tools. The way a star vanishes, then reappears, can reveal details about both the star and the Moon.

If the star fades in steps, that probably means it’s a binary – two stars that orbit each other. The Moon covers up one star a moment before it hides the second one. Several binary systems were discovered this way. Watching an occultation at different wavelengths also reveals details about the individual stars, such as their brightness and temperature.

Occultations also have helped map the lunar surface. The Moon isn’t smooth – it’s marked by rugged impact craters, canyons, and mountains. The precise timing of the occultation reveals whether the star was blocked by one of these features.

Occultations aren’t quite as important to scientists as they once were. But they’re still interesting to watch – as the Moon “hides” a star.

This occultation will be in good view from the central and western parts of the United States, although it occurs a little late for most of the eastern part of the country. The exact timing depends on your location

Script by Damond Benningfield

There are several ways to envision the celestial scorpion. The main way is to look for the outline of the scorpion, which is low in the south at nightfall at this time of year. Its curving body really does resemble the nasty little arachnids. Its head is to the upper right of the body, the tail and stinger to the lower left, with the bright orange star Antares between them.

Then there’s the scientific way. Astronomers have divided the sky into 88 official constellations, including Scorpius. Each one has precisely defined borders. Scorpius, for example, is bounded by 18 facets. So the constellation looks a bit like an off-center tower of boxes.

Finally, there’s the astrological way – the sign of Scorpio. It’s one of the signs of the zodiac – sections of the Sun’s path across the sky.

About 2500 years ago, the astrologers of ancient Babylon split the zodiac into 12 signs, all of the same width. So the Sun spent roughly the same amount of time in each sign. It was “in” Scorpio from about October 23rd to November 21st. And at the time, that was a fairly close match to the physical pattern of the scorpion.

Over the centuries, though, the dates at which the Sun appears in front of a given star pattern have changed. Today, the Sun enters Scorpius several weeks later than it did centuries ago. But the astrological signs have remained fixed – away from the constellations for which they’re named.

Script by Damond Benningfield

Astronauts and cosmonauts have been sharing time in orbit for three decades. But their first mission together began much earlier, with the Apollo-Soyuz Test Project. An Apollo spacecraft linked up with a Soviet Soyuz capsule in 1975.

The craft had launched on July 15th. First up were two cosmonauts aboard the Soyuz, followed by three astronauts aboard the final Apollo.

And 50 years ago today, the two spacecraft came together. Cosmonaut Alexei Leonov congratulated astronaut Tom Stafford, who’d flown the docking.

LEONOV: Well done, Tom. It was a good show!

The space travelers stayed together for two days. They shook hands, conducted some maneuvers, did some experiments, and took part in a lot of ceremonies, including a phone call from President Gerald Ford.

FORD: Your flight is a momentous event and a very great achievement, not only for the five of you, but also for the thousands of American and Soviet scientists and technicians who have worked together to ensure the success of this very historic and very successful experiment in international cooperation.

It took years to get the next joint mission off the ground. But today, despite wars, upheavals, and political chaos, American astronauts and Russian cosmonauts continue to meet in space.

Script by Damond Benningfield

An astronomical trio lines up low in the east at first light tomorrow. Two of its members are easy to pick out: Venus, the brilliant “morning star,” with the true star Aldebaran close to its right. But to see the third member, you need to pull out your binoculars.

NGC 1647 is just to the right of Venus, much closer than Aldebaran is. It’s a star cluster – a tightly packed family of hundreds of stars. Most of the cluster’s details are a bit fuzzy, though. Estimates of its age, distance, and the number of stars vary by quite a bit.

In part, that’s because the cluster is behind a cloud of dust, which absorbs some of its light. But it’s also because NGC 1647 hasn’t received a lot of attention.

Measurements put the cluster’s distance at about 1800 to 2,000 light-years. One study said the cluster has at least 600 member stars, while another puts the number at 1300 or more. And estimates of its age range from about 120 million years to more than 260 million.

Based on the structure of NGC 1647, it appears that no matter how old it is, it may not last much longer. The cluster may be losing its grip on the stars outside its dense core. The stars are being pulled away by the gravitational tug of the rest of the galaxy. Soon, many of them could drift away – leaving a much smaller family of stars.

Tomorrow: shaking hands.

Script by Damond Benningfield

If you ever find yourself floating above the clouds of Saturn, gazing upon the planet’s magnificent rings, you might feel like you need to get your eyes checked. Even at noon, when the Sun is highest in the sky, the view will look as dim as the minutes before sunrise or after sunset here on Earth.

That’s because Saturn is almost 10 times farther from the Sun than Earth is. At that distance, the Sun shines only about one percent as bright as it does on Earth. And that presents some problems for spacecraft that travel to Saturn.

For one thing, they can’t use solar power. They’d need huge arrays of solar cells, which would make a craft far too heavy and expensive. Instead, Saturn-bound missions are nuclear powered.

For another, it’s hard to take good pictures. A craft has to leave the shutter open for a long time to properly expose an image. At the speeds a craft is moving, that blurs the shot. The solution is to turn either the camera or the entire spacecraft to stay focused on the target.

No spacecraft are operating at Saturn now. The next one is scheduled for launch in a few years. It’ll ferry a small helicopter to Saturn’s big moon Titan – under the faint light of the distant Sun.

Saturn appears near our own Moon early tomorrow. It looks like a bright star, standing just below the Moon at dawn. The planet fades from view as the sky brightens – under the full glory of the nearby Sun.

Script by Damond Benningfield

Only about one in five Americans was born before the “Mars Era” – before the first spacecraft visited the Red Planet. That first encounter took place 60 years ago today, beginning six decades of Mars exploration.

Mariner 4 was launched in late 1964. A sister craft had failed. And early Soviet efforts failed as well. That inspired jokes about a “great galactic ghoul” eating Mars-bound probes.

Mariner 4 had eluded the ghoul for seven months. AUDIO: Then, July 14th: Encounter Day. This is Mariner control. All systems are green. And as this NASA film explained, they stayed green. AUDIO: The shutter is operating, the TV sees the planet, the recorder is working.

Mariner skimmed just 6100 miles from Mars. It snapped 21 pictures. The images depicted a landscape of craters and volcanic plains. They made Mars look like a dead planet.

Yet Mars exploration continued. Later missions revealed that Mariner 4 was unlucky – it scanned an unusually desolate strip. Today, we know that Mars has an active atmosphere. Ice lurks just below its surface. And it once was warm and wet, with rivers flowing across its surface, perhaps filling a giant ocean – making Mars a possible home for life.

Today, a half-dozen orbiters and rovers are exploring the planet. And others are being planned – extending a legacy of exploration that began six decades ago.

Script by Damond Benningfield

A brilliant “new” star blazed into view more than a thousand years ago. It’s the brightest star ever recorded, and may be the brightest ever seen by human eyes.

Supernova 1006 first appeared in late April of the year 1006. For a few weeks it shined many times brighter than Venus, which is the brightest object in the night sky after the Moon. It was bright enough to see during the day, and remained visible at night for more than two years. It was recorded by cultures around the world.

At the time, nobody knew what the star actually was. Today, though, we know it was a supernova.

It formed in a binary system. At least one of the two stars was a white dwarf – a stellar corpse. It might have pulled gas from a living companion star. Or perhaps the companion was another white dwarf, and the two stars rammed together. Either way, a white dwarf was pushed beyond its critical weight limit. That caused a runaway nuclear explosion that blasted the star to bits.

Debris from the blast continues to race outward at millions of miles per hour. Astronomers watch this debris, mainly in radio waves and X-rays, to learn more about the star and its demise.

Supernova 1006 was along the border between the constellations Lupus and Centaurus. The spot is low in the south-southwest at nightfall. But the residue of this brilliant outburst has faded away. Large telescopes reveal only a colorful ribbon at the edge of the expanding bubble.

Script by Damond Benningfield

A couple of bright cousins of Antares, the heart of the scorpion, skitter to its lower right on July evenings. They’re the brightest stars of Lupus, the wolf.

The stars of Lupus originally formed part of the adjoining constellation Centaurus. But they were split off to form a new constellation a couple of thousand years ago.

The wolf’s brightest stars are Alpha and Beta Lupi. Both stars belong to the Scorpius-Centaurus O-B association – a complex of stars and star-making ingredients that spans hundreds of light-years.

The first stars in the association were born about 25 million years ago. Beta Lupi probably was one of those stars. Winds from the earliest stars, along with shockwaves from exploding stars, probably triggered a major round of starbirth about five million years later. And two more big rounds followed, spaced about five million years apart. Alpha Lupi probably was born during one of those peaks, no more than 20 million years ago.

Alpha Lupi is about 10 times the mass of the Sun. So despite its young age, it’s nearing the end. It will explode as a supernova within the next few million years. Beta Lupi is a little less massive. So it might explode as well. But it’s possible that it faces a less dramatic fate, ending its life as a small, faint ember – a meek end for a mighty star.

Lupus is quite low in the south at nightfall. You need to be south of about Dallas or Phoenix to see its brightest stars.

More about the wolf tomorrow.

Script by Damond Benningfield