StarDate

A hard-to-see fox trots high across the sky on autumn evenings: the constellation Vulpecula. It’s not very big, and its stars are all faint. But it was the site of one of the most famous discoveries in astronomy history — one that briefly looked like it might be a sign of alien life.

The constellation was first drawn in the late 1600s. It filled a void between several prominent constellations. Originally, it was known as Vulpecula et Anser — the little fox and the goose. Later, the goose was dropped from the name.

Instead, “Anser” was assigned to Vulpecula’s brightest star. It’s a giant — much bigger and brighter than the Sun. From its distance of about 300 light-years, though, it’s so faint that you can’t see it from a light-polluted city.

In 1967, British graduate student Jocelyn Bell discovered odd pulses of radio waves coming from Vulpecula. They repeated every one and a third seconds. At first, no one could figure out what was causing them. Bell and her advisor, Antony Hewish, even considered the source might be an alien civilization.

Astronomers eventually determined, though, that the pulses came from a spinning neutron star — the super-dense corpse of a once powerful star. As it spins, it beams out energy like a lighthouse. That makes it a pulsar — the first one ever seen.

The fox is high in the sky at nightfall. It’s near the middle of the Summer Triangle, which is outlined by three bright stars.

 
Script by Damond Benningfield

Even if you have cloudless evening skies at this time of year, a watery view awaits you — a stretch of constellations associated with water. Together, they’re known as the “celestial sea.” They stretch across the southeastern sky in early evening, and across the entire southern sky by midnight.

Much of the association with water comes from the time of year: Autumn was a rainy season for much of the Mediterranean, where the modern constellations were named.

As the sky gets dark, look about a third of the way up the southern sky for Capricornus, the sea-goat. Its stars aren’t especially bright. But they form a distinctive pattern. And under dark skies, it’s fairly easy to pick out — a triangle that’s often compared to the bottom of a bikini bathing suit.

Aquarius the water bearer wraps above and to the left of Capricornus. And the only really bright star in the entire “sea” is below them: Fomalhaut, which represents the mouth of Piscis Austrinus, the southern fish. And the other fish, Pisces, is in the east and southeast — a V-shaped pattern with a pentagon at the right point of the V.

By midnight, these constellations have rolled far to the west. The last two members of the sea climb up behind them — Cetus, the sea monster, and a long, ragged trail of stars known as Eridanus, the river.

These constellations will grace the evening sky for months — stars that sparkle through the cool nights of autumn and into the colder nights of winter.

Script by Damond Benningfield

Day and night will be just about equal the next few days — for the entire world. That’s because fall arrives in the northern hemisphere late tonight. It’s the September equinox — the moment the Sun crosses the equator from north to south.

At that moment, the Sun stands directly above the equator. So no matter where you are, the Sun rises due east and sets due west.

“Equinox” means “equal nights.” That tells us that day and night should be the same length. But that’s not quite the case. Daytime — the interval from sunrise to sunset — lasts a few minutes longer than nighttime. Here in the northern hemisphere, they won’t balance out until a few days after the equinox.

One reason for the difference is the way we figure the moments of sunrise and sunset. For the day and night to be equal, we’d have to think of them as the time the Sun is bisected by the equator — when half is in view, and half is below the horizon.

Instead, of course, we consider sunrise as the moment the top of the Sun first peeks into view. And sunset is the moment when the Sun fully disappears. That adds a minute or so to the “daytime” side of the equation.

And we don’t actually see the Sun rise and set — at least not live. Earth’s atmosphere bends the Sun’s rays around the planet. So by the time you see the setting Sun touch the western horizon, it’s actually already set. You’re seeing an extended version of things — stretching the daylight over a few extra minutes.

Script by Damond Benningfield

Mars doesn’t have much air left, and it’s losing what little it has. It’s being sheared away by the Sun — a process that’s trimmed the atmosphere to almost nothing.

Planetary scientists have been watching that process in action through a spacecraft called MAVEN. It entered orbit around Mars five years ago today. And it’s still going.

The craft’s major goals are to measure Mars’s atmosphere and its interaction with the solar wind — a flow of charged particles from the Sun. It’s found that the solar wind strips away hydrogen from the top of the atmosphere — a result that was expected. But it also found something that wasn’t expected: about 10 times more material is stripped away when Mars is closest to the Sun than when it’s farthest.

When Mars was young, it had a much thicker atmosphere. That kept the planet warm enough for liquid water to flow across its surface. But the water has long since disappeared. MAVEN found that most of the atmosphere was gone by 3.7 billion years ago, leaving it too thin to retain the planet’s water. Today, the atmosphere is less than one percent as thick as Earth’s — leaving Mars dry, cold, and desolate.

MAVEN is expected to keep an eye on the Martian atmosphere for quite a while — it has enough propellant to keep going until at least 2030. In the meantime, it’s getting ready for a second mission. It’ll serve as a relay station for the next Mars rover, which is scheduled for launch next year.

Script by Damond Benningfield

Time travel has two vocabularies. For most of us, it’s Tardises, DeLoreans, and time turners. For scientists, though, it’s wormholes, naked singularities, and closed time-like curves.

Physicists will be tossing those terms around next week at a conference in Italy. They probably won’t come up with a new device for heading back in time. But they may come up with a better understanding of the science behind time travel.

Traveling through time is allowed by General Relativity, Albert Einstein’s theory of gravity.

A naked singularity, for example, would be like the center of a black hole without the surrounding black hole. That would allow you to pass near the dense concentration of matter without getting trapped. Instead, it might fling you elsewhere in time.

A wormhole is like a tunnel — a shortcut connecting not only different points in space, but different points in time. In fact, if wormholes exist, they must be time machines.

A closed time-like curve would bring an object that followed that curve back to its starting point in space and time. In effect, the object would move back in time.

There are many problems with time travel, though. It violates the idea that things should happen in a certain order; we’re born before we die, for example. And there are practical considerations. Most concepts of time travel require huge amounts of energy, or non-existent forms of matter. Still, they’re not ruled out by the laws of physics, so they’re worth spending a little time on.

Script by Damond Benningfield

A bright star follows the gibbous Moon across the sky late tonight. That seems appropriate, since the star’s name means “the Follower.”

Aldebaran is the bright orange eye of Taurus, the bull. It’ll stand to the lower left of the Moon as they climb into good view, after midnight, and even closer to the Moon at first light.

The name “Aldebaran” is from an ancient Arabic phrase that meant “the Follower.” The star was called that because it follows the Pleiades — a star cluster that looks like a tiny dipper. It’s to the right of Aldebaran and the Moon at dawn, leading them across the sky.

Aldebaran isn’t the only name for this bright, beautiful star. In fact, it has quite a few.

As the leading light of Taurus, for example, it’s assigned the first letter of the Greek alphabet, so it’s known as Alpha Tauri.

Many of its designations come from catalogs. Astronomers have compiled many different star catalogs, based on different traits. The Henry Draper catalog, for example, lists stars based on the breakdown of their light. The Gliese catalog lists the stars that are close by. And the Hipparcos catalog lists the more than 100,000 stars that had their distances measured by a space telescope.

In these catalogs, Aldebaran is listed as HD 29139, GJ 9159, and HIP 21421. They’re not the most poetic or inspiring names, but they help astronomers fit Aldebaran into the scheme of things — finding its place among the stars.

Script by Damond Benningfield

The names of 72 giants of French science, engineering, and mathematics are engraved on the Eiffel Tower. Two of them were born less than a week apart. For a while, they were colleagues. In scientific circles, though, they’re probably best known for similar experiments they conducted apart: measuring the speed of light.

León Foucault was born 200 years ago today. Hippolyte Fizeau came along five days later.

Foucault originally planned to become a doctor. But he fainted at the sight of blood. So he switched to physics. He was especially interested in the properties of light. And he devised a basic device which confirmed that Earth turns on its axis: the Foucault pendulum.

Fizeau was planning to become a doctor as well. In medical school, though, he developed severe migraines. He traveled for a while, which helped his health. Then, like Foucault, he turned to physics.

Foucault and Fizeau began working together in the late 1830s. They improved the photographic technique of the day, and used it to snap the first photo of the Sun.

Working independently, the two scientists worked on measuring the speed of light. In 1849, Fizeau came up with a number that was the best of its time — off by only five percent.

A couple of years later, Foucault proved that light travels faster through air than through water. And in 1862, he made his own measurement of lightspeed. It was off by only half a percent — by far the best measurement of the time.

Script by Damond Benningfield

In its first fraction of a fraction of a fraction of a second, the universe expanded and cooled in a hurry. That may have caused it to “crack.” And the cracks may still ripple through the universe — as cosmic strings.

If they exist, the strings would be narrower than a proton — one of the parts of an atom. But they could be light-years long. In fact, some could extend across the entire universe. And they’d be heavy, too: A segment of string a few inches long could weigh more than a mountain.

Theory says the strings probably would have been created an instant after the Big Bang. The universe went through a “phase transition” then — like water freezing to make ice. And just as a piece of ice can have cracks if it freezes too quickly, the change in the state of the universe created cracks in space-time. As the universe continued to expand, those cracks may have expanded right along with it.

Many ideas about how the universe was born suggest that cosmic strings must have been part of the process. So far, though, no one has seen any evidence of them.

But that could change. If two strings cross, or if one string doubles back on itself, a piece of the string could break off as a loop — like a stretchy rubber band. The creation of a loop — or any “wiggles” produced as a string moves through space — could create gravitational waves. And current or future detectors might be able to pick up those waves — revealing “cracks” in the universe.

Script by Damond Benningfield

A galaxy a billion light-years away is firing a beam of energy in our direction. Fortunately, it’s not an intergalactic weapon. Instead, it’s a “jet” that’s powered by a supermassive black hole.

BL Lacertae is in the faint constellation Lacerta, the lizard, which is high in the northeast at nightfall.

When it was discovered, in 1929, astronomers thought it was a faint star inside the Milky Way Galaxy. Decades later, though, they were able to measure its distance. At a billion light-years, the object must be extremely powerful. It’s also compact, because its light can vary over a period of hours or even minutes — something that can’t happen for large objects.

It turns out that BL Lacertae is powered by a black hole at the heart of a galaxy. The black hole is hundreds of millions of times the mass of the Sun. Gas and dust form a wide, flat disk around the black hole. Material in the disk spirals inward.

Not all of it enters the black hole, though. Radiation and powerful magnetic fields funnel some of the material into narrow jets. They shoot into space from above the poles of the black hole at almost the speed of light. We happen to align with one of the jets, so BL Lacertae shines brightly.

Astronomers have discovered hundreds of similar objects. Since BL Lacertae was the first, it’s the prototype for the entire class — giant black holes that are shooting beams of energy far into space.

Tomorrow: Stringing the universe along.

Script by Damond Benningfield

A star doesn’t have to be big to be brash. Indeed, some of the most active stars are also some of the smallest.

An example is in Lacerta, the lizard. The constellation is high in the northeast at nightfall. It’s not much to look at — only a few puny stars outline the lizard’s profile.

But about a decade ago, one of its stars really showed off. It produced the most powerful stellar flare seen to that time — thousands of times more powerful than anything the Sun has generated.

Flares are massive explosions. They occur when lines of magnetic force get tangled, then snap. Some of the biggest happen in little stars.

EV Lacertae, for example, is a red dwarf. It’s only about a third as massive as the Sun, and just one percent as bright. A red dwarf is different from stars like the Sun. Hot gas bubbles from its core all the way to the surface. The gas is electrically charged. So as it churns, it generates a strong magnetic field. And EV Lacertae is quite young, so it spins faster than the Sun does. That amps up the magnetic field even more.

With a faster-spinning magnetic field, the lines are bound to get more tangled. And when they snap, they do so with a jolt — a giant flare. It blasts energy and particles into space.

If the Sun zapped Earth with such a flare, it could knock out everything from cell phones to power grids — decimating our technology in an instant.

We’ll talk about an even more powerful object in Lacerta tomorrow.

Script by Damond Benningfield