A hundred years ago today, the New York Times reported that Edwin Hubble had made a big discovery. He confirmed that many of the spiral objects known as nebulae were really separate galaxies – “island universes” of stars far outside the Milky Way. The story ran on page six, and it misspelled Hubble’s name. But it was the first public announcement of one of the greatest scientific findings of the 20th century. The discovery dramatically expanded the known universe. Instead of consisting of the Milky Way alone, the universe contained billions of galaxies, spread across billions of light-years of space. Hubble studied a class of stars in two spiral nebulae – Andromeda and M33. Called Cepheid variables, the stars pulse in and out. Measuring the length of its pulses and other details reveals the star’s true brightness. From that, astronomers can calculate the star’s distance. Hubble calculated that Andromeda was about 860,000 light-years away, and M33 a bit farther. Modern calculations show that they’re about three times farther than Hubble thought. Still, the concept was proved: the universe extends far beyond our galactic home – a concept revealed a century ago. Andromeda – now known as the Andromeda Galaxy – is in the east-northeast at nightfall. Under dark skies, it’s visible to the eye alone – 2.5 million light-years away. We’ll talk about the most famous Cepheid tomorrow. Script by Damond Benningfield
The stars of the Big Dipper dip quite low at nightfall at this time of year. In fact, from south of about Kansas City, one or more of its stars dip below the horizon and out of view. And from south of about Dallas, the entire dipper vanishes. Like all the stars north of the celestial equator, the stars of the dipper circle around the north celestial pole, which is marked by the star Polaris. How high or low the dipper stands depends on your latitude. From the northern half of the United States, the stars are “circumpolar.” That means they never set – they’re always above the horizon, both night and day. In many cultures, such stars were described as “eternal” or “undying.” That made them especially important in the skylore and mythology of those cultures. From the southern half of the country, the dipper isn’t circumpolar – not all of it, anyway. From some locations, one or two stars drop below the horizon. From others, the entire dipper sets. Even from those spots, though, it climbs back into view within a few hours. So the dipper is in sight for at least part of the night every night of the year. As twilight fades this evening, viewers at northern latitudes can see the dipper roughly parallel to the northern horizon. From southern latitudes, it might be hidden. But it will climb back into view after midnight. And no matter where you are, the Big Dipper will stand high in the sky at dawn. Script by Damond Benningfield
For the Moon, it’s another night, another bright companion. After passing close to the brightest star of Gemini and the planet Mars over the past couple of nights, tonight it takes aim at Regulus, the heart of the lion. The star climbs into good view directly below the Moon after midnight. The Moon will move toward the star during the night, so they’ll be much closer at dawn. The Moon passes near these bright lights because, just like the Moon, they all stay close to the ecliptic. That’s an invisible line that marks the Sun’s annual path across the sky. The stars all maintain a fixed position relative to the ecliptic – at least on human timescales. Over the millennia, the ecliptic itself actually shifts a little – the result of a slow wobble in Earth’s axis. The orbits of the Moon and planets are tilted a bit. That causes those bodies to move back and forth across the ecliptic. The planets cross the ecliptic every few months or years. But the Moon crosses every couple of weeks. It spends two weeks to the north of the ecliptic, then two weeks to the south of it. Tonight, it’s a few degrees to the north. Early Monday, though, it will cross to the southern side. And that will set up an especially close encounter with the next bright light along the ecliptic: Spica the brightest star of Virgo. In fact, the Moon will pass directly in front of the star early Wednesday. We’ll tell you all about that next week. Script by Damond Benningfield
There’s no liquid water on the surface of Mars. But if you could squeeze the planet like a damp sponge, a lot of water might ooze out. Observations by a Mars lander suggest that huge amounts of water might lurk below the surface – enough to cover the entire planet with an ocean a mile deep. Mars was much warmer and wetter in the distant past. Rivers flowed across the surface, feeding into lakes and perhaps a giant ocean. Most of that water has vanished. There’s some frozen water in the polar ice caps and in slabs below the surface, but no liquid water. Scientists have been trying to figure out what happened to the rest of the water. Some of it was lost to space. But some could have trickled below the surface, in either liquid or frozen form. The InSight lander listened for “marsquakes” for four years. The way sound rumbles through the planet reveals details about what’s below the surface. A recent look at those observations suggested there could be a lot of water more than seven miles down. It would be contained in cracks and pores in volcanic rock – not as underground reservoirs. Still, it’s more than enough water to account for the ancient lakes and ocean – now hidden far below the Martian dunes. Look for Mars close to the upper right of the Moon as they climb into good view in late evening. The planet looks like a bright orange star. We’ll talk about the Moon and another bright light tomorrow. Script by Damond Benningfield
When astronomers compare the brightness of different stars, they use a scale known as absolute magnitude. That’s how bright the stars would look if they were lined up at the same distance: 10 parsecs, which is 32.6 light-years. One star they’d barely have to nudge is Pollux, the brightest star of Gemini. It’s only one light-year farther than that distance. So if it moved to exactly 10 parsecs, you’d have a hard time telling any difference in its appearance. That includes its color. Its orange glow tells us that its surface is thousands of degrees cooler than the surface of the Sun. Originally, Pollux would have shined almost pure white – an indication that its surface was much hotter than it is today. But the star used up the hydrogen fuel in its core. That triggered a series of changes that caused its outer layers to puff up to giant proportions. As the gas expanded, it cooled, making the star orange. Today, Pollux is the closest giant star to the Sun – a bit more than 10 parsecs away. Pollux is close to the Moon as they climb into good view by about 10 o’clock tonight. The moonlight will wash out some of the star’s color. Gemini’s other twin, the star Castor, will stand farther to the upper left of the Moon. They’ll be high in the sky at first light. By then, the Moon will line up half way between Pollux and an even brighter orange light: the planet Mars. We’ll have more about Mars and the Moon tomorrow. Script by Damond Benningfield
This has been a busy year for the Sun. It’s near the peak of its 11-year magnetic cycle, so it’s produced some big eruptions of energy and charged particles. Some of those outbursts have caused troubles here on Earth. And future storms could cause even bigger troubles, with some cities facing a greater threat than others. Solar outbursts are triggered by storms on the surface of the Sun. Lines of magnetic force become tangled and twisted. Eventually, they snap, then reconnect. That blasts energy and particles throughout the solar system. When these waves hit Earth, they can create brilliant auroras that appear much farther south than usual. On the downside, they can damage or destroy orbiting satellites, knock out some radio communications, and force airlines to reroute flights. And they can knock out power grids on the surface. An especially powerful storm could disrupt a grid for weeks. Scientists in Britain have been looking at the likelihood of such outages. They’ve considered many factors: the layout of power grids, how well the ground in a region conducts electricity, and how close to the surface auroras might come, among others. In the United States, the cities at greatest risk appear to be Milwaukee and Washington, D.C. The researchers are looking at those and other cities in more detail. That should allow them to come up with a better understanding of the risks we all face from our “stormy” star. Script by Damond Benningfield
Jupiter is the “big brother” of the solar system in more ways than one. It’s more than twice as massive as all the other planets and moons combined. That makes its gravity especially strong, so it can push around the little guys. What’s more, Jupiter likely is the oldest of the Sun’s planets. Like all the planets, Jupiter probably was born from a disk of gas and dust around the young Sun. It began to grow in the cold outer regions of the solar system. Bits of ice, rock, and metal stuck together. By the time the Sun was perhaps one or two million years old, Jupiter had already grown to about 20 times the mass of the present-day Earth. Jupiter then began to gobble up vast amounts of gas. After another two or three million years, it was several dozen times Earth’s mass. It pulled in so much material that it cleared a wide gap in the disk around the Sun. And it blocked the stuff that was outside its orbit from drifting inward. That may have prevented the birth of anything more massive than Earth closer to the Sun. Earth, by the way, wasn’t born until the Sun was about 50 million years old – a younger brother to giant Jupiter. Look for Jupiter to the upper right of the Moon as they climb into view this evening. It looks like a brilliant star. The true star Aldebaran – the eye of the bull – is farther along that line. And fainter Elnath – the tip of the bull’s horn – is quite close above the Moon. Script by Damond Benningfield
The bright Moon has some bright companions tonight: the planet Jupiter and the stars Aldebaran and Elnath. But the Moon washes out some fainter lights: the Leonid meteor shower. The shower is expected to reach its peak late tonight – perhaps 15 or 20 meteors per hour. But only the brightest of them will shine through the glare of the just-past-full Moon. The nearby planet and stars will be much easier to see – especially Jupiter, which will stand below the Moon as they climb into good view. It’s the brightest pinpoint of light in the sky for most of the night. Jupiter is so bright for several reasons. For one, it’s the largest planet in the solar system – 11 times the diameter of Earth. For another, it’s blanketed by clouds that reflect most of the sunlight that strikes them. And finally, the planet is especially close now – less than 400 million miles away. It’ll be at its closest early next month. Aldebaran is to the lower right of the Moon. It’s Taurus’s brightest star. It represents the bull’s eye. It shines bright orange, but the color might be muted by the nearby Moon. Elnath is the second-brightest star of Taurus. It’s at the tip of one of the bull’s horns. It, too, is washed out by the moonlight. Even so, it should still be pretty easy to pick out – part of a beautiful arc around the gibbous Moon. Jupiter and Elnath will be even closer to the Moon tomorrow night. More about that tomorrow. Script by Damond Benningfield
The first intentional message to other civilizations was beamed into the galaxy 50 years ago tomorrow. There wasn’t much to it – just 1,679 bits of data. When properly decoded, the message yields a picture – stick-figure outlines of a person and the message’s planet of origin, for example. The image also features the facility that beamed it into space: the giant Arecibo radio telescope, which collapsed a few years ago. The Arecibo message was conceived by Frank Drake. He was a pioneer in SETI – the search for extraterrestrial intelligence. He’d conducted the first search for radio signals just 15 years earlier. One of his collaborators was celebrity astronomer Carl Sagan. The message was intended primarily as a publicity stunt. Arecibo had just received a major upgrade, and astronomers wanted to show it off. So the message was transmitted just once – it wasn’t repeated. Other messages have followed, from radio telescopes around the world. Today, though, scientists and others are debating the wisdom of alerting the rest of the galaxy to our presence. They wonder whether messages to the stars might bring an unpleasant response. The target for the Arecibo message was M13, a giant star cluster in Hercules. It’s in the west-northwest at nightfall, and it’s an easy target for binoculars or a small telescope. But it’s so far away that the message won’t get there for another 25,000 years. Script by Damond Benningfield
Half of the planets discovered in other star systems are about the same size and mass as Uranus and Neptune, two of the giants of our own solar system. But we don’t know much about these exoplanets – in part because we don’t know much about Uranus and Neptune themselves. They’re billions of miles away, and only one mission has visited either planet. But scientists hope to learn more around the middle of the century. A panel of scientists recommended a “flagship” mission to Uranus as NASA’s next big project for planetary exploration. An orbiter would loop around Uranus and its moons for years, while a probe would parachute into the planet’s atmosphere. Uranus is an oddball. It lies on its side – probably the result of a collision with another planet when it was young. Scientists would like to know more about the impact and how it affected the planet’s interior. The sideways orientation also gives Uranus a cycle of seasons unlike that of any other planet. And some of the planet’s moons could have oceans of liquid water below their icy crusts. NASA hasn’t yet started on the mission – in part because it’s working on a lot of other big-ticket items. So it’ll be a while before we get a close look at this common type of giant planet. Right now, Uranus is low in the east as darkness falls. Tonight, it’s not too far to the lower left of the Moon. But it’s so faint that you need binoculars or a telescope to see it. Script by Damond Benningfield
It’s cold in the outer solar system. The planet Uranus, for example, is 20 times farther from the Sun than Earth is. As a result, its 28 known moons all shiver at hundreds of degrees below zero. Yet several of the planet’s bigger moons might have active volcanoes. Instead of molten rock, they’d belch out molten ice – a slushy brew from buried oceans of liquid water. We don’t know for sure if any of the moons have ice volcanoes, but there’s evidence that they do. The surfaces of the moons are fairly young, for example. That suggests that something is renewing them – like material from the interior. And a couple of the moons appear to be pumping material into the space around Uranus. Recent observations by Webb Space Telescope found additional evidence for an ocean on the moon Ariel. It’s coated with frozen carbon dioxide. Webb found the layer of C-O-2 is especially thick. And it’s mixed with carbon monoxide. Both compounds should quickly vaporize and drift off into space. Their presence suggests the supply is being renewed – perhaps by volcanoes belching ice from a hidden ocean. Uranus is putting in its best appearance of the year. The giant planet rises around sunset and is in view all night. It’s brightest for the year, too, although you still need binoculars to pick it out. Tonight, it lines up about half way between the almost-full Moon and the bright planet Jupiter. We’ll have more about Uranus tomorrow. Script by Damond Benningfield
Polar vortex has entered the American lexicon with a fury in recent years. It’s used to describe especially bitter outbreaks of winter weather. The northern hemisphere actually has two polar vortexes. The one that gives us the extreme cold is fairly low in the atmosphere. It’s formed by jet streams that encircle the pole that sometimes plunge southward. The other is much higher in the atmosphere. The higher vortexes are seen on every planet and moon in the solar system with much of an atmosphere. That includes Uranus, the third-largest planet. Scientists found evidence to confirm the vortex last year. Hints of a vortex around the north pole were seen in 2015. More recently, scientists looked at the pole with a giant radio telescope in New Mexico. They saw an especially bright area at the pole itself, with a dark ring around it. The bright region was warmer than the surrounding atmosphere. The combination provides strong evidence of a polar vortex. Air in the upper atmosphere moves toward the poles. It’s deflected by the planet’s high-speed rotation – forming a “vortex” around the north pole. Uranus is putting in its best appearance of the year. It’s lining up opposite the Sun, so it rises around sunset and is in view all night. It’s brightest for the year as well. But you still need binoculars or a telescope to see it, along the border between Taurus and Aries. We’ll have more about Uranus tomorrow. Script by Damond Benningfield
It’s springtime – on Mars, anyway – because today is the spring equinox for the Red Planet’s northern hemisphere. Like the seasons on Earth, the seasons on Mars are the result of the planet’s tilt on its axis. In fact, the two planets are tilted at almost the same angle. So the north pole dips toward the Sun at the start of northern summer, while the south pole dips sunward at the start of northern winter. The equinoxes are half way between those points. But there are some differences between the seasons on Earth and Mars. Mars’s orbit is more stretched out than Earth’s orbit, so there’s a bigger difference in the planet’s distance from the Sun. Mars’s distance varies by about 26 million miles. That has a couple of effects. For one thing, it creates a big disparity between the seasons in the northern and southern hemispheres. Mars is farthest from the Sun during southern winter, and closest during summer. That means southern winters are colder than northern winters, while summers are warmer. And second, Mars moves fastest when it’s close to the Sun, and slowest when it’s far away. That causes a big difference in the length of the seasons. Northern spring is the longest – it lasts 194 Mars days. Northern fall is the shortest – just 142 days. Look for bright orange Mars climbing into good view in late evening, and high in the southwest at first light – a world that’s springing into a new season. Script by Damond Benningfield
The Moon will stage a pair of cover-ups over the next couple of nights. The first happens tonight, when the Moon covers up the planet Saturn. And the second happens just 24 hours later, when it covers the planet Neptune. The cover-ups are known as occultations. They occur because the Moon and planets all stay close to the ecliptic – the Sun’s path across the sky. But they all stray a few degrees to either side of the ecliptic. So most months, the alignment is off by a bit, so the Moon just misses the planets. At times, though, the geometry is just right, as it is now – at least for parts of the world. Tonight, for example, the occultation of Saturn will be visible from a bit of South America, most of Central America, and the southern half of Florida. There, Saturn will disappear at about 9:20 p.m. It’ll remain out of sight for about 45 minutes. Because Saturn forms a tiny disk in our sky, it’ll take a few seconds for the planet to disappear and reappear – it won’t instantly blink off and back on. The rest of the United States will see an especially close encounter between Saturn and the Moon. Saturn looks like a bright star, and will pass just a fraction of a degree from the Moon. Tomorrow night, it’s Neptune’s turn. The path of the occultation will cross most of the United States. But Neptune is so faint that you need a telescope to watch the giant planet vanish – another cover-up for the gibbous Moon. Script by Damond Benningfield
The bright Moon washes out the fainter stars tonight. One that shines through is Hamal, the leading light of Aries, the ram. It’s in the east at nightfall. It’s about 65 light-years away. And it’s a giant – bigger, heavier, and brighter than the Sun. The other stars of Aries are tougher to see. And some stars that once formed separate constellations around it are impossible to see. In fact, they were tough to spot even when they were first outlined. To the left of Hamal is Triangulum Minus, the little triangle. It was created by German astronomer Johannes Hevelius, in 1687. Its three stars are all quite faint. So even without the moonlight, they’re visible only under dark skies, away from city lights. Below Hamal is Musca Borealis, the northern fly. It consists of four faint stars. The constellation was created by Petrus Plancius, in 1612. His original name for it was Apes, the bees. Later, another astronomer called it Vespa, the wasp. Hevelius then took over. He kept the buzzy theme, but he went with Musca, the fly. But there was already a fly in the southern hemisphere, so astronomers clarified matters by adding “northern” to the name. In 1930, the International Astronomical Union adopted 88 official constellations, all with well-defined borders. The little triangle was incorporated into Triangulum. And the stars of the northern fly became part of Aries – buzzing around the rump of the ram. Script by Damond Benningfield
Capella is a big mismatch. It’s a system of four stars, divided into two widely separated pairs. The members of one pair are both about two and a half times the mass of the Sun. But the members of the other pair are only about half the Sun’s mass. As a result, the two pairs face quite different futures. Capella is the brightest star of Auriga, the charioteer, and the sixth-brightest star in the entire night sky. It climbs into good view in the northeast in early evening and soars high overhead during the night. The system appears to be about 600 million years old – four billion years younger than the Sun. Yet the stars in the heavier pair are both at the end of life. They’ve burned through the original hydrogen fuel in their cores. That’s made them puff up to giant proportions. Before long, both stars will shed their outer layers. The stars are close enough together that the expelled gas should act like a brake, causing the stars to spiral close together. But as the gas disperses, the stars will be much lighter. That will loosen their grip on each other, causing them to move farther apart. So no one is quite sure what the system’s final configuration will look like. The smaller stars, on the other hand, will remain in the prime phase of life for tens of billions of years longer. But as the heavier stars trim down, the two pairs are likely to drift apart – splitting up a stellar quartet. Script by Damond Benningfield
Scientists don’t have a crystal ball to help them foretell the future of the universe. But they can devise ideas about the future based on their understanding of the history of the universe and the laws of nature. Based on that, perhaps the leading idea about the fate of the universe is the Big Freeze: The universe will get colder and darker, and eventually disintegrate into a soup of particles. The key ingredient of the Big Freeze is dark energy. Scientists don’t yet understand its nature. But it causes the universe to expand faster as it ages. And if it keeps its foot on the accelerator, the universe faces a bleak future. Hundreds of billions of years from now, the expansion rate will outpace the speed of light. Galaxies will disappear from each other – their light won’t move fast enough to reach most of the other galaxies. The final stars will be born in a few trillion years. By then, most stars will have expired. Galaxies will consist mainly of the corpses of stars, plus some faint stars and smaller objects. Over the eons, all the stars will die, and the stellar corpses will evaporate. And after trillions upon trillions of years, even black holes will vanish. Only ghostly particles will remain. This future is far from certain. Scientists have many questions about dark energy and more. They’ll need to peer deeper into their crystal balls – the laws of nature – to tell us whether the universe will die in a Big Freeze. Script by Damond Benningfield
A faint glow fills the entire universe – the “afterglow” of the Big Bang. The glow was created when the first atoms formed – 380,000 years after the Big Bang. But the glow isn’t smooth – it has tiny ripples and bumps. That’s because the universe itself wasn’t smooth – there were slight differences in the density of matter. Without those differences, we wouldn’t exist. The denser regions had a slightly stronger gravitational pull, so they drew in the material to make the first stars and galaxies. The first stars were born in as little as a hundred million years. They were made almost entirely of hydrogen and helium, which were created in the Big Bang. The stars probably were quite heavy, so they burned out in a hurry. They forged heavier elements in their cores, then blasted them into space when they died. Some of those elements were incorporated into later generations of stars. Those stars created more heavy elements and flung them into space as well, and so on. The heavier elements are the ingredients for planets and everything on them – including us. Galaxies began to form about four hundred million years after the Big Bang, as stars and gas clouds clumped together. More stars and galaxies are being born today, but not as many. In fact, most of the stars and galaxies that will ever be born have already taken shape. So the universe may face a cold, dark fate, and we’ll talk about that tomorrow. Script by Damond Benningfield
Our universe has a long and complicated history. And scientists are still trying to understand it all. The general picture says the universe was born 13.8 billion years ago, in the Big Bang. For the first tiny fraction of a second, the universe expanded at many times the speed of light – an epoch known as cosmic inflation. When inflation ended, the expansion slowed dramatically. But a lot happened over the following few minutes. During the first second, the basic forces of nature took shape: gravity, electromagnetism, and the forces that bind matter together. These forces made it possible to forge protons and neutrons. By about three minutes, the universe had expanded and cooled enough for these particles to stick together. They formed the nuclei of the first elements – mainly hydrogen and helium. The universe was still extremely hot and dense. And it was “foggy,” so we can’t see anything from that era. By about 380,000 years, though, the fog began to clear. Electrons latched on to the nuclei to form complete atoms. That process left a faint “afterglow” that we see across the entire universe. There are lots of questions about the details of this picture. And some scientists aren’t convinced about the overall outline – they have different views about the age of the universe, whether inflation ever happened, and more. There’s a little more agreement about what came next, and we’ll talk about that tomorrow. Script by Damond Benningfield
It’s hard to imagine a less comfortable place for life than the clouds of Venus. They’re made mainly of sulfuric acid – something you wouldn’t want to dip your fingers into. Yet studies in the past few years are raising at least the possibility that microscopic life could inhabit those clouds. There’s almost no way for anything to live on the surface of the planet. The atmosphere is too hot, dense, and toxic. But the clouds are about 30 miles high, where the conditions are more like those on Earth. A few years ago, scientists reported finding phosphine in the clouds. On Earth, it’s a compound that’s almost always produced by living organisms. Other studies have found no trace of it. But earlier this year, astronomers reported finding new evidence of the compound. Another study this year reported finding ammonia. On Earth, it’s produced mainly by living organisms and industrial processes. And yet another study said that some of the key building blocks in amino acids could survive in a high concentration of sulfuric acid. None of that means that anything actually lives in the clouds. But it does mean that scientists will be taking a much closer look at Venus’s clouds in the years ahead. Venus is the brilliant “evening star.” It’s quite low in the southwest as night falls. Tonight, it’s close to the upper right of the crescent Moon. It’ll be a little farther to the lower right of the Moon tomorrow night. Script by Damond Benningfield
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