Our closest neighbor star is a bare cosmic ember. It’s much lighter and smaller than the Sun, and less than one ten-thousandth as bright. Yet the star produces giant explosions that are much more powerful than anything ever seen from the Sun. An outburst two years ago, in fact, was the brightest from any star at some wavelengths. Proxima Centauri is just four-and-quarter light-years away, but it’s too faint to see without a telescope. The star is put together a little differently from the Sun. A conveyor-belt effect carries hot gas from the core to the surface, where it cools and falls back toward the core. This motion generates a powerful magnetic field. As the star spins, the lines of magnetic force get tangled. When they cross, they snap, producing massive eruptions. Proxima has produced many such outbursts over the years. But one in May of 2019 beat them all. Astronomers recorded a flare that lasted just seven seconds. At visible wavelengths, though, it was a hundred times brighter than any flare seen from the Sun. And it was even brighter in X-rays and ultraviolet light — the brightest ever seen from any star. Two planets orbit Proxima Centauri. One of them is at a comfortable distance from the star for life. But getting zapped by such powerful radiation is dangerous. So if anything lives on the planet, it most likely would have to be quite different from life on Earth to survive such powerful outbursts.  Script by Damond Benningfield Support McDonald Observatory

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Dangerous Neighborhood

Our planet appears to be in one of the safest neighborhoods in the Milky Way Galaxy. We’re away from the regions where deadly exploding stars are most common. That’s the finding of a study released this year. Researchers in Italy looked at the number of supernovas and gamma-ray bursts over the entire history of the galaxy. A supernova is the death of a star. It fills its region of space with radiation and particles. They can sterilize nearby planets, and be harmful at distances of dozens of light-years. A gamma-ray burst is also an exploding star. But it emits powerful beams from its poles that can zap life thousands of light-years away. The researchers found that early on, the safest region of the Milky Way was its rim, far beyond Earth. There were fewer exploding stars out there. Earth’s region, about halfway out to the edge, was a little more dangerous. Over time, though, the “safe” zone moved inward. And over the last half-billion years, we’ve been at the outer edge of that zone. There have been more supernovas closer to the center, and more gamma-ray bursts out on the rim. In the future, the number of exploding stars in our neighborhood should keep going down — making it even safer. The Milky Way arches across the eastern evening sky now. The center of the galaxy is in the south, above the “spout” of the teapot formed by the stars of Sagittarius. That’s the galaxy’s danger zone — a neighborhood to avoid.  Script by Damond Benningfield Support McDonald Observatory

Safe Neighborhood

Monster black holes were forming when the universe was young — just a few percent of its current age. And that’s a problem. Most ideas of how supermassive black holes form can’t explain such a rapid birth. But a new idea says the black holes could have had some help: the gravitational pull of dark matter. Supermassive black holes are millions or billions of times as massive as the Sun. They inhabit the cores of most large galaxies, including our own. And they’ve been seen in galaxies that were forming as little as 800 million years after the Big Bang — 13 billion years ago. One idea says that such monster black holes formed from the collapse of giant clouds of gas and dust. Another says that smaller black holes merged to form the supermassive ones. But neither process could form a giant black hole quickly enough to match what astronomers see. The new idea says these early galaxies formed around clouds of dark matter. Dark matter produces no energy, but we see its gravitational pull on the “normal” matter around it. If there was enough dark matter, it could pull in huge amounts of normal matter in a short time. The combined matter then would collapse to form a supermassive black hole. According to this idea, supermassive black holes would form quickly — even before their home galaxies could fully take shape. So the dark monsters at the hearts of galaxies could have formed under the influence of dark matter.  Script by Damond Benningfield Support McDonald Observatory

Dark Monsters

The Moon shines big and bright tonight. It climbs into good view by about 11 p.m., and is well up in the southwest at first light tomorrow. And it has a big and bright companion: the planet Jupiter. It looks like a brilliant star to the upper left of the Moon as they rise, and to the right of the Moon at dawn. By that time, the Moon will be about two and a half days past full. So for American skywatchers, the Sun will light up about 93 or 94 percent of the lunar disk. You might think that means the Moon will be 93 or 94 percent as bright as the full Moon. And your eyes might seem to agree — since the Moon looks almost full, it must be almost as bright. This is one of those times that you can’t trust your lying eyes, though. The pre-dawn Moon will be only half as bright as a full Moon. By comparison, when the Sun lights up half of the disk, it’s only one-sixth as bright as a full Moon. One reason is that the lunar surface reflects sunlight most efficiently when the Moon lines up opposite the Sun — when it’s full. The main reason, though, is that when the Moon is full, we don’t see many shadows — the central portion of the disk is in direct sunlight. At other times, though, the Sun is at a lower angle. Mountains, the rims of craters, and even big boulders cast shadows that make the surface appear darker. And the farther the Moon is from full, the longer the shadows — and the darker the Moon looks in our sky.  Script by Damond Benningfield Support McDonald Observatory

Moon and Jupiter

Jupiter and Saturn are the largest planets in the solar system. Jupiter is about 11 times the diameter of Earth, while Saturn is almost 10 times Earth’s diameter. Despite their size, though, they spin faster than any other planets — 10 hours for Jupiter, a bit longer for Saturn. That’s compared to 24 hours for Earth. You might wonder why these giants turn so fast. But scientists wonder why they aren’t faster. They should have spun a lot faster when they were born, but they slowed down. A study a couple of years ago proposed a solution. Jupiter and Saturn grew so big by gobbling up huge amounts of gas from a disk around the newborn Sun. As the gas fell onto the planets, it caused them to spin faster. Eventually, they should have been spun once every few hours — so fast that they were about to break apart. But some of the gas was directed back outward, forming a disk around each planet. The planets’ magnetic fields grabbed onto the gas. That acted like a brake, slowing each planet to a much slower rate than we see today. Their own gravity quickly caused the planets to shrink, which made them spin faster — the same way a skater spins faster by pulling in its arms. That set up the rates we see today — fast or slow. Jupiter and Saturn form a wide triangle with the Moon tonight. As they climb into view in late evening, bright Jupiter is to the left of the Moon, with fainter Saturn to the upper right.  Script by Damond Benningfield Support McDonald Observatory

Moon and Planets

The Moon and Titan, the largest moon of Saturn, have something in common: The best places to get wet are at the poles. The Moon has lots of water ice. And Titan has actual liquid — lakes and seas filled not with water, but with hydrocarbons. On the Moon, the ice is mixed with dirt at the bottoms of deep craters. Sunlight never hits the crater floors, so the ice remains frozen. A recent study suggested there’s more than a billion tons of ice around the poles, with most of it near the south pole. Because of that, most lunar exploration over the coming years will be targeted at the south pole. Robotic landers will sniff out and study the ice. And human explorers may use the ice for water, oxygen, and rocket fuel. On Titan, most of the wet stuff is near the north pole — about 95 percent. The largest body of liquid, the Kraken Sea, holds more than all the Great Lakes combined. Differences in climate and landscape account for some of the imbalance between the poles. But one study says the major difference is that the southern landscape is more porous. The liquid ethane and methane can drain away to lower latitudes, where they evaporate — leaving the south pole much drier than the north. And Saturn appears close to our Moon the next couple of nights. Tonight, it’s to the left of the Moon as they climb into good view by 10 o’clock, and above the Moon at first light. The giant planet looks like a bright star.  Script by Damond Benningfield Support McDonald Observatory

Moon and Saturn

The galaxy IC 10 is small but busy. It’s only a few thousand light-years across — a small fraction of the size of the Milky Way. But pound for pound, it’s giving birth to more stars than the Milky Way is. Many of those stars are big, bright, and heavy. At the ends of their short lives, they’ll explode. The cores of some of those stars will collapse to form black holes. One system in the galaxy consists of a current black hole and a future one. IC 10 X-1 was the first source of X-rays discovered in the galaxy. The X-rays come from a “wind” of hot gas from the bright star, plus a disk of hot gas around the black hole. Early observations indicated the black hole was about 15 times the mass of the Sun, with its companion about 25 times the Sun’s mass. But more recent work has found the masses a little tougher to pin down. The companion appears to be heavy enough to explode as a supernova, leaving behind a second black hole. The blast may send the star and the current black hole racing away from each other. If they stick together, though, in a few billion years they’ll merge — forming an especially heavy black hole. IC 10 is in Cassiopeia, which is low in the northeast in early evening and overhead at first light. IC 10 is near the top right point of the “W” that outlines the queen. The galaxy is a couple of million light-years away — quite close as galaxies go. But it’s so faint that you need a telescope to see it.  Script by Damond Benningfield Support McDonald Observatory

IC 10 X-1

[Double booms] MISSION CONTROL: Piercing the pre-dawn skies, the space shuttle announces its arrival at the launch site with its signature sound of twin sonic booms, having gone subsonic for the last time. The space shuttle program rolled to a halt 10 years ago today. Atlantis completed the 135th shuttle mission, 30 years after the first. The shuttle had been intended to replace almost all of America’s rockets. NASA promised to launch up to a flight a week. But shuttles were harder to maintain than expected. So launches were separated by months, not days. Still, the shuttle was a remarkable machine. Its crews launched and repaired satellites, including Hubble Space Telescope. They conducted experiments. And they built most of the International Space Station. But after the shuttle Columbia was destroyed during re-entry in 2003, NASA decided to ground the fleet after the space station was done. For the final flight, Atlantis carried up spare parts and scientific equipment. Then it headed home. AUDIO: three bells. ISS: Atlantis departing the International Space Station for the last time. It landed at Kennedy Space Center on July 21st, 2011. MISSION CONTROL: Nose-gear touchdown. ... Having fired the imagination of a generation, a ship like no other, its place in history secured, the space shuttle pulls into port for the last time—its voyage at an end.  Script by Damond Benningfield Support McDonald Observatory

End of the Shuttle

Making a mirror for a giant telescope requires a long-term commitment. Back in March, for example, GMT — the Giant Magellan Telescope — began work on the sixth of its mirrors. It’ll take about three years to finish the job. GMT will use a total of seven mirrors. They’ll work together to act as a single mirror about 80 feet in diameter — far larger than any current telescope. That will allow GMT to see stars and galaxies that are much fainter and farther, greatly expanding our view of the universe. Each mirror is cast in a circular furnace at the University of Arizona. About 20 tons of a special glass is heated to more than 2100 degrees. The furnace rotates, sculpting the molten glass to the proper shape. It takes about three months for the mirror to cool. Technicians then spend more than two years grinding and polishing it. The surface has to be smooth to within a millionth of an inch. Buddy Martin, who leads the process, described that level of accuracy during a March press conference. MARTIN: If the mirror were expanded to the size of North America, 3500 miles in diameter, then the average hill would be two-thirds of an inch tall and the average valley two-thirds of an inch deep. That’s how smooth this mirror has to be for it to make the sharpest images that nature will allow. All the mirrors are scheduled to be sent to GMT’s mountaintop site, in Chile, late in the decade.  Script by Damond Benningfield Support McDonald Observatory

Long-Term Commitment

For most stars, life seems to happen in slow motion — it takes a long time for them to change. One exception appears near the Moon tonight. Over the last 25 years it’s gotten a lot brighter, and it’s created a “pancake” of gas and dust around itself. Delta Scorpii is close to the lower right of the Moon as night falls. It’s the middle star in the “head” of the scorpion. The scorpion’s brightest star, Antares, is farther to the lower left of the Moon. Delta Scorpii is about 450 light-years away. It consists of two stars. One of them is about 14 times the mass of the Sun. The other is about two-thirds as heavy. The stars orbit each other once every 11 years. The orbit is stretched out, so most of the time the stars are a long way apart. At their closest, though, they’re closer than Earth is to the Sun. By the time of a close approach in 2000, the bigger star had surrounded itself with the pancake — something that hadn’t been seen before. The star is big and puffy, and it spins in a hurry. That appears to be throwing gas from its equator, forming the disk. As the smaller star moves inward, it may stir and heat the disk, making the system shine brighter. In fact, it got roughly twice as bright early in this century. The stars made their last close approach 10 years ago this month, so they’ll get close again next year. Astronomers will be watching to learn more about this rapidly changing system.  Script by Damond Benningfield Support McDonald Observatory

Moon and the Scorpion

AUDIO: Godspeed, John Glenn. 10, ... On the morning of February 20th, 1962, John Glenn became an American icon. LAUNCH CONTROL: 3, 2, 1, zero. GLENN: Roger, the clock is operating. We’re under way. Glenn became the first American to orbit Earth. He circled the planet three times aboard his tiny capsule, Friendship 7. Then came parades, a reception at the White House, and other honors. Glenn was born 100 years ago today, in Ohio. He was an outgoing athlete in high school, and earned a pilot’s license while in college. During World War II, he became a fighter pilot. He flew combat missions during that war and in Korea. Glenn then became a test pilot. And in 1959, he was picked as one of America’s first astronauts — the Mercury Seven. During their introduction at a press conference, Glenn emerged as the favorite. GLENN: Well, my wife made a remark the other day, I’ve been out of this world for a long time, I might as well go on out there. After his flight, NASA didn’t want to risk its most popular astronaut, so it grounded him. Glenn turned to politics, and was elected to the U.S. Senate. But he never lost the desire to fly in space again. He convinced NASA to launch him on a space shuttle, in 1998. LAUNCH CONTROL: 3, 2, 1, booster ignition and liftoff of Discovery with a crew of six astronaut heroes and one American legend. Glenn died in 2016, at age 95 — still an American legend. AUDIO: Godspeed, John Glenn.  Script by Damond Benningfield Support McDonald Observatory

John Glenn

There’s more than one way to see the stars — or at least the patterns of stars. In western culture, for example, the stars of the Big Dipper and those around it form the great bear, Ursa Major. The dipper outlines his body and tail, while three faint pairs of stars represent his feet. In ancient Arabia, though, those pairs represented the leaps of a gazelle, and they’re named accordingly. The first pair is known as Alula Borealis and Alula Australis — the northern and southern halves of the first leap. The second pair is Tania Borealis and Australis — the second leap. And the third pair is known by the name of its brighter star, Talitha — the third leap. The stars in the three pairs are unrelated — they’re all at different distances from Earth. They just happen to line up in such a way that they form close pairs as we look toward them. Perhaps the most impressive of all the “leaping” stars is Alula Borealis. It’s a red giant — a star that’s puffed up at the end of its life. It’s about 70 times wider than the Sun, and more than a thousand times brighter — bright enough that it’s visible across more than 400 light-years of space. The gazelle leaps across the northwest as night falls. The first leap is well to the lower left of the bowl of the Big Dipper. The second leap is to the lower right of the first, with the final leap farther to its lower right — the leaps of a gazelle in the footprints of the great bear.  Script by Damond Benningfield Support McDonald Observatory

Leaping Gazelle

A bright star that follows the Moon this evening shows how tough it is to know what’s happening inside a star. Spica is the leading light of Virgo. It’s to the lower left of the Moon as night falls. It’s one of the brighter stars in the night sky, so astronomers have paid a lot of attention to it over the centuries. And they know a lot about it. For example, they know that it’s a binary — two stars locked in a mutual orbit around each other. Astronomers can plot the orbit, which tells them how far apart the stars are. It also gives them the masses of the two stars. The bigger star — Spica A — is about 10 times the mass of the Sun. The other star isn’t quite as big, but it’s still impressive. Studying the individual wavelengths of light from the stars reveals their composition and temperature. Combined with their masses, that tells us about each star’s phase of life. Spica A is going through a transition. It’s completing its primary phase of life, the main sequence. That’s caused its core to shrink and get hotter, which has made the star bigger and brighter. But astronomers aren’t sure exactly where it is in the transition. It could be just finishing it up. On the other hand, it could have finished the transition fairly recently, and is now moving full-on into the next phase of life — puffing up to become a giant. Continued studies might help resolve the question of what’s happening inside this big, bright star.  Script by Damond Benningfield Support McDonald Observatory

Moon and Spica

Pluto shines at its best this week. It lines up opposite the Sun, so it rises near sunset and stays in view all night. It’s brightest for the year as well. Don’t bother looking for it, though; to be visible to the eye alone, it would have to shine at least a couple of thousand times brighter. But you can spot Pluto’s location. It’s about half way between the bright planet Saturn, which is low in the east-southeast this evening, and the “teapot” outlined by the stars of Sagittarius, to Saturn’s upper right. Pluto is hard to see because it’s tiny — only about two-thirds the size of the Moon — and because it’s a long way from the Sun — about three billion miles. Its orbit is lopsided, though. So for the next century, Pluto will move even farther from the Sun, heading for a maximum distance of 4.6 billion miles. Pluto’s orbit was one reason the little world was dropped from the list of the Sun’s major planets. The orbit is more stretched out than any other planet’s. It’s also more tilted. Finally, Pluto is locked in a “resonance” with Neptune, the farthest of the major planets. Pluto completes two orbits for every three made by Neptune. That suggests that Pluto is being herded along by giant Neptune — just like many other bodies in the outer solar system. The combination spurred Pluto’s reclassification — as the Sun’s best-known dwarf planet. Tomorrow: looking into the heart of a star.  Script by Damond Benningfield Support McDonald Observatory

Pluto at Opposition

An ocean of liquid water might lurk below the icy crust of Pluto. And it might have been around since the little planet was born. Scientists have based those conclusions in part on Pluto’s most prominent feature — a heart-shaped basin called Sputnik Planitia. It was discovered by the New Horizons spacecraft, which flew past Pluto six years ago. The basin probably formed billions of years ago, when a giant asteroid hit the young world. The hole gouged by the collision most likely filled with water from the ocean, then was coated with ice when some of the atmosphere froze atop it. New Horizons discovered a jumbled landscape on the other side of Pluto — a region of big ridges and cracks. The area might have been mangled by vibrations from the impact moving all the way through Pluto. But a study suggests that to form such a large area of mangled terrain, Pluto must have had a deep but hidden ocean at the time of the impact. And the only way to keep the ocean from freezing was for Pluto to have formed quickly — in less than 30,000 years. The fast build-up would have made Pluto’s interior hot. As the heat worked its way outward, it would have kept the ocean warm and wet. The ocean has undergone many changes over the eons. It’s not as deep now, and it’s probably slushy. But it appears to still be there — helping make Pluto a dynamic little world. Pluto is at its best for the year this week, and we’ll talk about that tomorrow.  Script by Damond Benningfield Support McDonald Observatory

Deep Ocean

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