The Moon butts up against the tip of one of the horns of Taurus early tomorrow. They’ll appear to almost touch as they climb into good view, around 2:30 or 3 a.m. They’ll be closest as viewed from the East Coast, especially the northeast. The tip of the horn is represented by Elnath. It’s the second-brightest star in the constellation. It’s outranked only by Aldebaran, the bull’s eye. Based on the calendar alone, Elnath is a youngster – roughly 100 million years old. That’s only about two percent the age of the Sun. But the star is well into middle age. That’s because it’s about five times the mass of the Sun. Heavier stars “burn” through their nuclear fuel much faster than lighter stars. So Elnath probably is about halfway through its prime phase of life. Right now, it’s fusing hydrogen to make helium. So is the Sun. The process is more complicated for heavier stars. But the result is the same: the nuclei of four hydrogen atoms fuse together to make one helium atom. Almost one percent of the mass of the hydrogen is converted to energy, making the star shine. The Sun converts more than four million tons of mass to energy every second. Elnath fuses its hydrogen at a much faster rate, and it has a lot more hydrogen to start with. So it converts hundreds of millions of tons of matter to energy per second – making “the butting one” almost 600 times brighter than the Sun. Script by Damond Benningfield

Planets can really get around. In the early days of our own solar system, for example, the giant outer planets may have moved toward or away from the Sun by hundreds of millions of miles. And many of the planets seen in other star systems probably have spiraled inward from their birthplaces. One example is a planet orbiting the star Gliese 1214. The star is smaller and less massive than the Sun, and just one-third of one percent as bright. The planet is a “mini-Neptune” – bigger and heavier than Earth. It’s so close to the star that it’s extremely hot – about 535 degrees Fahrenheit on the dayside, and 325 degrees on the nightside. Astronomers studied the planet a couple of years ago with Webb Space Telescope. They found that it’s blanketed by shiny clouds or haze. They reflect half of the starlight that strikes them back into space. The composition of that layer suggests the planet has gone through some changes during its long lifetime. It might have formed much farther from the star – out beyond the “snow line,” where there was a lot of frozen water and other ices. Over time, it spiraled inward and heated up. The heat changed its atmosphere, producing the hot, shiny brew seen today. Gliese 1214 is in Ophiuchus, which is high in the south at nightfall. But the star is much too faint to see without a telescope. Script by Damond Benningfield

A star system in the constellation Ophiuchus keeps blowing up. Every 15 years or so, it flares about 1500 times brighter than average. And it could be building up to an even bigger outburst – a final act that would make it shine billions of times brighter. RS Ophiuchi consists of two stars. One of them is a white dwarf – a small, hot stellar corpse. The other is a red giant – a dying star that’s much bigger than the Sun. Gas from the giant flows toward the white dwarf. It forms a swirling disk that’s millions of miles across. Gas in the disk spirals inward, and settles on the white dwarf. When enough gas builds up, it gets hot enough to trigger a nuclear explosion – a nova. Gas blasts outward at millions of miles an hour. That destroys the disk around the white dwarf – but only for a while. It regenerates in about nine months, starting the process all over again. Astronomers have recorded as many as nine outbursts from the system – the first in 1898, the most recent just four years ago. The gap between them has ranged from nine to 27 years, with an average of about 15. It’s possible that not all of the gas that piles up on the white dwarf gets blasted away, so the star keeps getting heavier. Eventually, it may pass the weight limit for such a star. If that happens, the white dwarf will blast itself to bits as a supernova – the final demise of a dead star. Script by Damond Benningfield

For a few weeks in the spring of 1764, Charles Messier was a star-cluster-discovering machine. He found five globular clusters in Ophiuchus, the serpent bearer. He cataloged them as Messier 9, 10, 12, 14, and 19. Messier wasn’t interested in the clusters – or even in the stars. Instead, he was looking for comets. At the time, finding a comet was a way to fame and fortune. Kings offered prizes to those who found comets. And comets were named for their discoverers – a bit of immortality. But Messier and others kept coming across fuzzy objects that resembled comets. Figuring out if they really were comets wasted time. So the French astronomer decided to compile a catalog of these distractions. He logged more than a hundred objects. They included star clusters, galaxies, stellar nurseries, and the final gasps of dying stars. Today, Messier’s list is the most famous of all astronomical catalogs. The globular clusters all look about the same. They’re tight balls of stars. Today, we know that the typical globular contains a hundred thousand stars or more. And they’re among the oldest residents of the Milky Way – more than 10 billion years old. Ophiuchus is a large constellation that stands well up in the southern sky at nightfall. Messier’s globulars are scattered across it. They’re all visible through binoculars – just don’t mistake them for comets. Script by Damond Benningfield

Barnard 68 is one of the darkest objects in our section of the galaxy. It’s a small cloud that absorbs the light of the stars behind it, so it looks like a dark “hole” in the Milky Way. Before long, though, that void may shine with the warmth of newly forming stars. Barnard 68 is a Bok globule – a small, dark sphere of gas and dust. It’s about 500 light-years away, half a light-year wide, and about three times the mass of the Sun. It’s part of a complex of dark clouds that stands in front of the glowing band of the Milky Way. Barnard 68 is so dark because it’s quite cold – temperatures at its center are close to absolute zero. But that may be about to change. The globule has been stable for millions of years. But there’s evidence that it’s recently been hit by a cosmic “bullet” – a smaller clump of gas and dust. That appears to be causing Barnard 68 to collapse. As it collapses, the cloud will get denser and hotter, and perhaps split into several smaller clumps. Within a few hundred thousand years, the clumps could be well on their way to becoming new stars – glowing balls of gas born from a dark “hole” in the Milky Way. Barnard 68 is in Ophiuchus, the serpent bearer, which is in the southern sky at nightfall. The Milky Way runs through a corner of the constellation. Several clouds darken the Milky Way – birthplaces of future stars. Script by Damond Benningfield

The gods of ancient Greece had complicated relationships. As an example, consider Ophiuchus. He’s represented by a constellation that passes across the southern sky on summer evenings. The constellation represented Asclepius, the god of medicine and the son of the god Apollo. In one version of the story, Asclepius killed a snake with his staff. But another snake dropped some herbs on the dead one, bringing it back to life. Asclepius then used those herbs to resurrect the son of King Minos. Business was so good for Asclepius that fewer people were entering the underworld. So Hades, the god of the underworld, complained to Zeus, the king of the gods. Zeus then killed Asclepius with a lightning bolt. But that didn’t sit well with Apollo. To appease him, Zeus placed Asclepius in the sky. Today, those stars are known as Ophiuchus, the serpent bearer. He’s depicted with a snake wrapped around his waist. And that’s why the symbol for modern medicine is a pair of snakes wrapped around a staff – it represents the story of Ophiuchus. Look for the serpent bearer high in the south as night falls. Its stars are faint. Under a dark sky, though, they form a pattern that resembles a coffee urn. It stands upright in early evening, but lies on its side later on. The constellation’s brightest star is at the top of the coffee pot – the “head of the serpent bearer.” More about Ophiuchus tomorrow. Script by Damond Benningfield

Earth has something in common with Titan, the largest moon of Saturn. They’re the only two bodies in the solar system with liquids flowing and ponding on the surface. In the case of Earth, that liquid is water. But on frigid Titan, it’s liquid hydrocarbons – methane and ethane. Titan is the second-largest moon in the solar system – a bit bigger than the planet Mercury. Its surface is extremely cold – hundreds of degrees below zero. Its atmosphere is thicker than Earth’s, and it’s topped by a dense layer of smog. The Cassini spacecraft used radar to peer through the clouds. And its findings were remarkable. It discovered rivers flowing across the surface, emptying into lakes and seas. It also found clouds, which occasionally produce rain. Everything we can see on Titan contains a lot of carbon-based compounds – some of the raw building blocks of life. That’s led to speculation that Titan might have the precursors to life – or even life itself – hidden in a giant ocean below the crust. To be clear, there’s no evidence of life. But future missions to Titan will sniff around for such evidence – perhaps adding to the list of things that Earth and Titan have in common. Saturn appears quite close to our own moon tonight. It looks like a bright star to the lower left of the Moon as they climb into good view, by about 11 o’clock. But you’ll need a small telescope to pick out Titan. Script by Damond Benningfield

One of the best-known meteor showers will be at its best the next couple of nights. Unfortunately, the gibbous Moon will be in the sky during the best hours for meteor watching. That will spoil the view of all but the brightest meteors. Perseid meteors are spawned by Comet Swift-Tuttle. The comet orbits the Sun once every 133 years or so. As it plies the interplanetary space lanes, it sheds tiny bits of rock and dust. The grains spread along the comet’s path. Earth flies through this path every August. The particles ram into the atmosphere at more than 130,000 miles per hour. They heat the air in front of them to thousands of degrees, forming the glowing streaks known as “shooting stars.” Swift-Tuttle is an especially big comet – about 16 miles in diameter. And its orbit sometimes brings it close to Earth. In August of 2126, for example, it’ll pass just 14 million miles away. And about 900 years later, it’ll miss by just one million miles. It’s hard to project the comet’s orbit more than a few thousand years into the future. So it’s possible that it could someday hit Earth – a collision that would wipe out most of the life on our fragile planet. Perseid meteors are best seen between midnight and dawn. Find a safe viewing site away from city lights, block out the Moon as much as you can, and scan the sky for the celestial fireworks. Script by Damond Benningfield

Social media may go wild the next few days – filled with reports of UFOs in the early morning sky. Ignore them. The objects are fully identified. They’re the planets Venus and Jupiter – the brightest objects in the night sky after the Moon. They’re crossing paths, as Jupiter pulls away from the Sun as seen from Earth, and Venus drops toward it. Venus is the brighter of the two. Venus and Jupiter could have a big influence on our own planet – not astrologically, but gravitationally. The planets all probably moved around a lot when the solar system was young. Today, their configuration is stable. And it should remain stable for hundreds of millions of years. But it’s impossible to predict beyond that. Tiny differences in a planet’s current orbit could have a big impact on its position in the far distant future. As a planet moves toward or away from the Sun, its gravity pushes and pulls the other planets, changing their location. Earth is most influenced by the gravity of Venus – which passes closer to us than any other world – and Jupiter – the most massive planet. They squeeze and stretch Earth’s orbit over a cycle of about 400,000 years. In the distant future, they could destabilize the orbit – dramatically changing Earth’s place in the solar system. Look for these “influential” planets beginning a couple of hours before sunrise. They remain visible deep into the dawn twilight. Script by Damond Benningfield

Based on how bright the stars look to our eyes alone, Deneb ranks among the 20 brightest stars in the night sky. Because the stars are at different distances, though, that ranking is a little misleading. If we could arrange them based on their true brightness, Deneb would outshine them all. In fact, it might be the brightest of all the stars that are easily visible to the unaided eye. Deneb is high in the east-northeast at nightfall, at the lower left corner of the bright Summer Triangle. Deneb is a blue supergiant – it’s much bigger, heavier, and hotter than the Sun. And it’s much, much brighter. Exactly how much brighter isn’t certain. That’s because there’s disagreement about the star’s distance. Astronomers have measured the distance with several techniques. Some are more direct, while others are based on models of different types of stars. That’s yielded estimates of about 1400 to 2600 light-years. And that makes a big difference. At the greater distance, Deneb would be almost four times brighter than at the smaller one. So Deneb’s true luminosity – the value when you add up all wavelengths of light – is somewhere between 50,000 and 200,000 times the Sun’s. If the high end of that range is correct, then Deneb is one of the brighter stars in the entire galaxy – and perhaps the brightest star that’s easily seen with the eye alone. Script by Damond Benningfield