StarDate Podcast

Planetary systems can be dangerous. Like race cars zipping around a track, planets can ram into each other. That can destroy one or both of the planets, and create massive piles of debris. Some of that debris may then fall onto the parent star. Astronomers have seen the likely aftermath of several such collisions. The most recent is in a star system in Auriga. The charioteer climbs into view in the northeast by about 10 p.m. It’s marked by the bright star Capella. Astronomers have been...

Saturn is the second-largest planet in the solar system — only mighty Jupiter outranks it. And it generates the second-largest magnetic “bubble” — a region of space dominated by Saturn’s magnetic field. It’s molded into a “teardrop” by the solar wind. Saturn’s magnetic field is generated deep inside the planet. A core of rock and metal probably is surrounded by a layer of metallic hydrogen. The core and the hydrogen rotate at different rates. That creates a dynamo effect, like an electric...

Many constellations have a star that represents its character’s tail. And the names of many of those stars begin with the Arabic word for tail, Deneb. The most famous are the tail of the swan, known simply as Deneb, and the tail of the lion, Denebola. Two lesser-known tail stars are in the southern sky this evening: Deneb Algedi, in Capricornus, the sea-goat, and Deneb Kaitos, in Cetus, the whale. Deneb Algedi is a good bit bigger and hotter than the Sun, and much farther along in life....

The hub of a galactic empire climbs the eastern sky on October evenings. M31, the Andromeda galaxy, is well up in the east-northeast at nightfall. Under dark skies, it looks like a smudge of light. But it’s actually a family of hundreds of billions of stars. It’s two and a half million light-years away — the farthest object that’s easily visible to the eye alone. About three dozen other galaxies orbit M31. A couple of them are impressive on their own. But most of them are little more than...

A half-century ago, the Moon Race was entering its final lap. Three American astronauts were about to ride an Apollo spacecraft into orbit — its first manned flight. The race had stalled almost two years earlier. The crew of Apollo 1 had died in a fire inside the spacecraft. And the first flight of the Soviet Soyuz spacecraft ended with a fatal crash. But on October 11th of 1968, the crew of Apollo 7 was standing by at Cape Kennedy, ready to head for Earth orbit: Wally Schirra, one of...

An interloper from another galaxy scoots low across the south on October evenings. It’s a tight family of stars — hundreds of thousands of them. The stars probably belonged to another galaxy that was consumed by the Milky Way in the distant past. Messier 30 is in the lower left corner of Capricornus. It’s low in the south at nightfall. The sea-goat’s brightest stars form a wide triangle. And bright orange Mars is passing through the constellation right now, making it easier to...

Despite its fame as a member of the zodiac, Capricornus is a bit tough to find. It’s the smallest member of the zodiac, and one of the faintest. It forms a distinctive pattern, though — like the bottom of a bikini bathing suit. So under dark skies, you can pick it out. The constellation represents a sea-goat. In Greek mythology, though, it was associated with the god Pan. During a battle with the Titans, he had to jump into the Nile to escape. When he did, the bottom half of his body was...

An unpredictable meteor shower should be at its best tonight. It could even produce a rare outburst, with hundreds or more “shooting stars.” A meteor forms when bits of dust and rock burn up in the atmosphere. Most of these particles are tiny, but they hit the air so fast that they vaporize, producing streaks of light. Tonight’s meteor shower is known as the Draconids, because the paths of the meteors trace back to the constellation Draco. But you don’t need to know where the dragon is...

The Sun is moving across the constellation Virgo this week. Right now, in fact, it’s not far from Spica, Virgo’s brightest star. We can’t see that, of course, because of Earth’s blue skies. The atmosphere scatters blue wavelengths, creating a curtain of light that blocks the view of the stars. If you look at the sky at local midnight six months from now, though, you’ll see the configuration of today’s noontime stars — what the sky would look like if the Sun weren’t in the way. The change...

The Big Dipper is plunging toward the northern horizon as night falls now, as if it’s about to dip into a pail of cool water. Line up the stars at the leading edge of the dipper’s bowl, and follow that line to the upper right. The first moderately bright star you come to is Polaris, the Pole Star or North Star. Earth’s north pole aims toward it, so Polaris forms the hub of the northern sky — all the other stars appear to rotate around it. And it’s always at the same point above the horizon...

A star that’s a popular location for mythologists old and new leads the Moon into the sky early tomorrow. Regulus represents the heart of Leo, the lion. The bright star will stand to the upper right of the crescent Moon at first light. Regulus is a system of at least four stars. But only one of them is visible to the unaided eye. It is bigger, heavier, and brighter than the Sun. And it’s a whisker less than 80 light-years away. That’s quite close on the astronomical scale. Regulus is not...

Getting to Mercury isn’t easy. The next mission to the Sun’s closest planet will need seven years to arrive and enter orbit. And to achieve that orbit, it’ll have to fly past Earth once, Venus twice, and Mercury six times. BepiColombo is scheduled for launch later this month. The mission is a joint project of Europe and Japan. It’s named for Giuseppe Colombo, a scientist who studied Mercury and worked on Europe’s mission to Comet Halley. The mission will consist of two spacecraft. They’ll...

The space close to Earth is getting crowded. It’s filling up with spacecraft, old rocket stages, and lots of other debris. The space a million miles behind Earth is getting crowded, too. It’s filling up with space telescopes. That point is known as L2. The gravity of Earth and the Sun are balanced there. So any spacecraft that goes there stays there. It’s a good spot for telescopes because their view isn’t blocked by Earth. They can be kept cooler there, too. That allows them to study...

The most successful technique for finding planets in other star systems is known as the transit method. Astronomers watch for a star to fade a tiny bit as a planet passes in front of it. The method finds planets only in star systems with the right geometry. Even so, it’s yielded thousands of discoveries. And it doesn’t require big telescopes to work. In fact, small telescopes are better for the job. They can watch a larger patch of sky, improving the odds of seeing a transit. And...

The closest exoplanet is Proxima Centauri b — just four and a quarter light-years away. Its parent star, Proxima Centauri, is less than one percent as bright as the Sun. Every once in a while, though, it unleashes a huge outburst of energy and particles. And more than two years ago, astronomers saw the most powerful one yet. Such “superflares” should happen several times a year. And that’s bad news for the planet. If it has an atmosphere, the flares could strip away any ozone atop it,...

Our galaxy is a giant spiral. Most of its stars — including the Sun — reside in a thin disk that resembles a pancake. But the Milky Way isn’t entirely flat. Instead, a “bulge” of stars in the middle juts above and below the pancake. A spiral galaxy in Draco, the dragon, is much flatter than ours. In fact, it has no central bulge at all. Instead, nearly all of its light comes from the disk. NGC 5907 is about 55 million light-years away. Because it’s both flat and edge-on, astronomers get a...

The Moon passes especially close to the bull’s bright orange “eye” tonight. Aldebaran is just an eyelash away from the Moon as they rise in late evening. Over the following hours, the Moon will pass even closer to the bright star, before they begin to pull apart. Aldebaran looks so bright because it’s a giant star that’s close by. At visible wavelengths, it shines about 150 times brighter than the Sun. But Aldebaran’s surface is thousands of degrees cooler than the Sun’s. Because of...

Sixty-five years ago, in a speech to the United Nations, President Dwight Eisenhower urged the world to abandon atomic weapons and use the atom for peaceful purposes. The speech became known as “Atoms-for-Peace.” And it inspired astronomers to name a galaxy for it. So NGC 7252 became known as the Atoms for Peace galaxy. It was picked because it looks electrons orbiting the nucleus of an atom. The galaxy got that shape because it’s the aftermath of a collision between at least two galaxies....

Astronomers are developing bigger and bigger arrays of radio telescopes. By combining the signals from dozens or hundreds of antennas, they can produce extremely sharp images of the universe — far more detailed than possible with any single telescope. That technique was pioneered by British astronomer Martin Ryle, who was born 100 years ago today. After earning a degree in physics from Oxford, Ryle helped develop radar during World War II. After the war, there was lots of surplus military...

Dozens of galaxies orbit our own, but none compares to the Magellanic Clouds. These two galaxies are so bright and vibrant that they’re visible to the eye alone — but only from the southern hemisphere. Hubble Space Telescope has tracked the motions of stars inside the smaller of the two galaxies. The observations suggest that it’s in serious trouble — the result of a recent collision with its brighter neighbor, the Large Magellanic Cloud. The Small Magellanic Cloud is 200,000 light-years...