StarDate

If you have sharp eyes or good binoculars, you can sometimes see double in the night sky – two stars that are quite close together. In some cases, the stars really are close – they can be bound to each other by gravity, forming a binary.

In other cases, though, it’s just a coincidence. The stars are unrelated, but they just happen to line up in the same direction. These stars are known as optical doubles. And some of them are beautiful sights – especially when viewed through a telescope. The two members can show different colors, providing a nice contrast.

One of the best-known examples is Albireo. It marks the head of Cygnus, the swan, and it’s high overhead at nightfall. A small telescope reveals one blue star and one gold star. The best measurements to date indicate that the stars are about 30 light-years apart.

An example that’s visible to the eye alone is Algedi, in Capricornus. It’s due south at nightfall. The eye can just make it out as two separate points of light. The stars are hundreds of light-years apart.

Sometimes, it’s hard to tell if a double star is a binary or not. The best example is Mizar and Alcor, in the handle of the Big Dipper. It’s fairly easy to see the stars as two points of light. They actually move through space together, so they probably were born together. But astronomers aren’t sure if they’re a true binary – or just two related stars moving through space on their own.

Script by Damond Benningfield

Stars aren’t always good neighbors. They can drag away planets from other stars. In some cases, they grab the planets for themselves. In others, they fling the planets away, to wander through space alone. And they might even fling away two or more planets, which then move through space together as “Jumbos” – Jupiter-Mass Binary Objects.

Astronomers first reported these odd pairings a year ago. Webb Space Telescope found them in the Trapezium – a cluster of young stars in the Orion Nebula.

The nebula has given birth to a couple of thousand stars, all of which are no more than a couple of million years old. And the stars are tightly packed, so close encounters between them are common. During those encounters, one star can pull planets away from another. In fact, Webb revealed more than 500 giant planets that aren’t orbiting any star.

About one-tenth of the planets are in binaries – the Jumbos. A study a few months ago said that, if two planets in a star system are aligned in just the right way, a passing star could pull away both of them. But the planets would stay together – zipping through a cluster of young stars and stolen planets.

The Orion Nebula is visible to the unaided eye. It looks like a faint, fuzzy star – energized by the light of several brilliant stars in the Trapezium. The nebula climbs into good view after midnight. It stands high in the south-southwest at dawn, below the stars of Orion’s Belt.

Script by Damond Benningfield

This has been a big year for exploring the Moon. The highlight came in June, when a Chinese mission landed on the lunar farside – the side we never see from Earth. Chang’e 6 then scooped up some samples and brought them to Earth for study – the first samples ever collected from the farside.

A couple of less-ambitious missions touched down earlier in the year. Both landers tipped over, but they managed to transmit some pictures.

More lunar missions had been scheduled for later this year.

The headliner was a rover called Viper. It was designed to hunt for ice near the south pole, along with other materials that might help support future human bases on the Moon. Viper was scheduled to spend 100 days trundling across the surface, including some areas that receive little or no direct sunlight.

This summer, though, NASA canceled the mission. Viper had already cost $450 million during several years of development and testing. But it wasn’t ready for flight, and neither was its ride to the Moon. NASA decided it would be too expensive to finish out. Instead, it’ll use the rover’s instruments for other projects – possible highlights for lunar exploration in future years.

Look for the gibbous Moon rolling across the southern sky tonight. The planet Saturn is to the left of the Moon at nightfall, and looks like a bright star. Saturn will be a little closer to the upper right of the Moon tomorrow night.

Script by Damond Benningfield

By the early 17th century, European sailors were being guided through southern seas by several birds – not on the wing, but in the stars. Five southern constellations were named for birds: the peacock, toucan, crane, and bird of paradise, plus a mythological bird that’s well known to Harry Potter fans: the phoenix.

All of these constellations were outlined by Johannes Bayer in a star atlas published in the early 1600s.

Those parts of the sky were unknown to Europe until explorers began heading southward. They mapped the stars and brought their observations back to Europe. A Dutch astronomer connected the stellar dots to create a dozen constellations, which Bayer depicted in his atlas.

Most of the birds are so far south that they’re impossible for most American skywatchers to see. But one of them strides low across the south on October evenings: Grus, the crane.

If you’re south of about Denver, look for the crane strolling along the horizon in early evening, with its neck extending low into the sky.

The star that marks the crane’s head is visible from most of the country. It stands due south about 10 o’clock, almost directly below the gibbous Moon. The farther south you are, the higher the star appears. Known as Gamma Gruis, the star is much bigger, brighter, and heavier than the Sun. It shines at us across more than 200 light-years of space – the bright eye of a beautiful southern bird.

Script by Damond Benningfield

Many of the ingredients for life here on Earth may have come from beyond Earth – delivered by asteroids or comets that hit our planet when it was young. And early analysis of samples of an ancient asteroid support that idea.

A mission called Osiris-Rex collected about four ounces of dust and pebbles from the surface of Bennu. The asteroid is about a third of a mile in diameter. Its orbit brings it close to Earth, making it a good target for study.

Osiris-Rex delivered the samples to Earth more than a year ago. Scores of scientists have been studying the samples.

They’ve found that the samples contain lots of carbon, nitrogen, and organic compounds – key ingredients for life. The samples also contain certain types of phosphates, which are part of the chemistry of all life on our planet.

Bennu’s minerals formed in the presence of water. Their composition is a lot like the material at mid-ocean ridges on Earth, where molten rock is bubbling up to form new crust. Those minerals suggest that Bennu is a chip off a larger object – an ocean world. The parent body was blasted apart by a collision with another asteroid. Some of the debris stuck together to form Bennu.

The early results are only a first step. Many more scientists around the world will study fragments of Bennu over the coming months and years. Their work will tell us more about the birth and evolution of this tiny world – as well as our own.

Script by Damond Benningfield

A star in Cassiopeia refuses to die. If astronomers are correct, it was “born” from the merger of two corpses. Such a collision usually blasts both stars to bits, but not this time. The combined star survived – also as a corpse. But it may not be completely dead. It’s producing a strong wind – a sign of possible rejuvenation.

The star appears to be the remnant of a supernova that was seen in the year 1181. It remained visible for six months.

The supernova may have formed from the merger of two white dwarfs – dead stars that are the final act for stars like the Sun. In most cases, such a merger makes the combined stars too massive to survive. The merged object blasts itself to cosmic dust.

In this case, though, only a fraction of the mass of the two stars was blasted away. The rest formed a white dwarf heavier than the Sun. It’s the hottest star yet seen – hundreds of thousands of degrees hotter than the Sun.

A recent study showed that the star is blowing a “wind” of particles into space at about five percent of the speed of light. The types of particles indicate that nuclear fusion has fired up in a thin layer around the core of the white dwarf – new life for a star that refuses to die.

Cassiopeia is in the northeast at nightfall. It looks like a sideways letter W. The possible supernova remnant is near the tip of the bottom left point of the W – about 7500 light-years away.

Script by Damond Benningfield

Europa may have the best skincare routine in the solar system. Its surface is smoother than that of any other known solid body – in part because the surface is quite young.

Europa is one of the four big moons of Jupiter. It’s a ball of ice and rock slightly smaller than our moon. Its crust is a fairly thin shell of ice. Below that, there appears to be a global ocean of liquid water dozens of miles deep. Fountains of hot water at the bottom of the ocean could provide key ingredients for life, including energy and the right chemical compounds.

The hidden ocean appears to play an important role in keeping the surface of Europa young and smooth.

Water and warm ice may reach the surface along narrow stripes that can stretch for hundreds of miles. The stripes may be like the mid-ocean ridges on Earth, where new crust is formed. Europa’s ice may slide apart there, allowing fresh material to fill in. At the same time, older ice may slide back down toward the ocean, where it can be recycled.

A spacecraft that’s orbiting Jupiter recently discovered a spot where water might have reached the surface fairly recently. It’s in a region of “chaos” terrain – a jumble of ridges, ice blocks, and low mounds. The feature covers more than a thousand square miles. It looks like a “pool” where salty water from the ocean could bubble to the surface – helping Europa keep its smooth, youthful appearance.

Script by Damond Benningfield

If scientists took bets on where we might find life elsewhere in the solar system, the odds-on favorite almost certainly would be Europa, one of the large moons of Jupiter. It appears to have all the ingredients for life: water, energy, and chemistry.

Europa is a bit smaller than our own moon. And it’s a bit farther from Jupiter than the Moon is from Earth. Most intriguingly, it appears to have an ocean of liquid water below its surface. The ocean could be dozens of miles deep, and contain more than twice as much water as all the oceans on Earth combined.

Europa is locked in by Jupiter’s gravity so the same hemisphere of Europa always faces the giant planet. But as Jupiter’s other big moons move past Europa, they tug at it. That stretches and squeezes Europa’s interior, heating it up. There appears to be enough heat to melt some of the ice below the surface, creating the ocean.

There could be “vents” of hot water on the ocean floor. They’d provide both energy and minerals. Added to the water, that gives Europa all the major ingredients for microscopic life. That doesn’t mean there is life on Europa – only that it’s the most likely place to find it elsewhere in the solar system.

Look for Jupiter climbing into good view in the eastern sky by about 11 p.m. It looks like a bright star, so you can’t miss it. Binoculars will reveal its four largest moons, including Europa.

We’ll have more about Europa tomorrow.

Script by Damond Benningfield

The Moon huddles quite close to Antares this evening. The star represents the heart of the scorpion. They’re low in the southwest at nightfall.

The Moon and Antares both played important roles in the astronomy and skylore of many cultures. And in at least one case, they may have overlapped.

Close encounters between them – especially at full Moon – may be recorded in grooves carved on the island of Gotland. It’s in the Baltic Sea, off the southeastern coast of Sweden. There’s evidence that it was inhabited thousands of years ago.

Archaeologists have charted about 3600 grooves. Some are carved into the bedrock, but most are found on boulders. The grooves are up to a few feet long, a few inches wide, and one or two inches deep. They’re found in groups.

The grooves in a group follow slightly different alignments. A study a couple of decades ago suggested those alignments were astronomical – they pointed toward the rising and setting points of the full Moon at certain times of the year.

In particular, the study found possible alignments in the largest set of grooves – 32 in all. Calculations revealed that they lined up with the Moon when it passed Antares at 19-year intervals – an important cycle in the Moon’s path along the horizon. The series could have started at the spring equinox almost 5200 years ago, and continued for centuries – a possible record of lunar encounters with the scorpion.

Script by Damond Benningfield

Our concepts of the cosmos can change in a hurry. A good example is Venus, which comes closer to us than any other planet. Over the past seven decades, our ideas about the planet have changed a lot. And they’re still evolving.

Venus is blanketed by clouds, which hide the surface. So as recently as the 1950s, some scientists thought the surface could be covered by oceans and by jungles teeming with life.

In the 1960s, though, the first spacecraft scanned Venus from up close. They found that its atmosphere is extremely hot, dense, and toxic – not a pleasant abode for life.

Later missions used radar to see through the clouds and map the surface. They found thousands of volcanic features. It looked like the planet had been repaved by molten rock hundreds of millions of years ago, then fell silent. But more recent studies appear to tell us that Venus could be as volcanically active as Earth.

There are even suggestions that microscopic life could live high in the sky, inside clouds made of sulfuric acid. But those ideas are still being debated. So our concepts of Venus could change even more in the decades ahead.

Venus is climbing into better view as the “evening star.” It’s quite low in the southwest as night falls. Tonight, it’s to the right or lower right of the Moon. Antares, the brightest star of Scorpius, is a bit closer to the upper left of the Moon. More about the Moon and Antares tomorrow.

Script by Damond Benningfield