StarDate

The pure white ice of Antarctica is the best place on Earth to hunt for meteorites. Scientists have picked up about 50,000 of them there — almost two-thirds of all the meteorites ever found. And hundreds of thousands more may await discovery.

The process isn’t easy, though. An expedition takes months of planning and weeks of criss-crossing the ice on snowmobiles. But the hunters might have found a helper — the equivalent of a meteorite-sniffing hound dog: an artificial-intelligence technique known as machine learning.

Meteorites are bits of debris from asteroids and comets. Studying them helps scientists piece together the history of the solar system. And some of the meteorites come from the Moon and even Mars.

Meteorites are hard to find, though. Most of them look a lot like Earth rocks, so they blend in to the background. In Antarctica, they stand out.

Scientists fed information on where meteorites have been found in Antarctica into their computers. They also entered details on the ice, the weather, the contours of the rock below the ice, and other conditions. From that, the machines learned how to predict where meteorites are likely to be found.

The computers came up with 600 plots, each covering one and a half square miles. Comparing the map with known success rates in the plots that have already been scoured showed an accuracy of 80 percent. So the maps may yield better hunting for future expeditions.
 

Script by Damond Benningfield

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Modern astronomy is a data factory. Big surveys look at thousands or millions of objects. And even bigger surveys will observe even more objects in the decades ahead. Even with all the grad students in the world, though, there’s no way to look through all of those stars, galaxies, and other objects by hand.

Astronomers are using artificial intelligence for help. Clever algorithms and lots of computing power can sift through mountains of data to ID different types of objects. And they can point out the most interesting ones for detailed follow-up.

An example is a recent project by astronomers in India. They used machine learning to sift through 277,000 objects cataloged by an X-ray space telescope.

The astronomers fed all the details into their computers. They added some observations by other telescopes in space and on the ground. They then entered details about known X-ray objects. The computer software compared the known objects to those in the catalog. That taught it how to know what was what. With its new-found knowledge, it then categorized the objects in the catalog.

It identified 33,000 galaxies with giant black holes in their hearts; 16,000 X-ray stars; five thousand newly forming stars; plus dead stars, binary systems, and other objects. Astronomers can now use those objects in their studies of the X-ray universe — new raw materials from the astronomical data factory.

More about big data tomorrow.
 

Script by Damond Benningfield

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It takes a lot of help to study one of the biggest mysteries in the universe: dark energy. An experiment at McDonald Observatory, for example, has used three supercomputers and the eyes of 10,000 volunteers to sift through more than 60 terabytes of data. That’s resulted in the project’s first catalog — more than 200,000 objects.

HETDEX — the Hobby-Eberly Telescope Dark Energy Experiment — is looking at a million galaxies in a small patch of sky that includes the Big Dipper. The galaxies are giving birth to a lot of stars. They’re about 10 billion light-years away, so HETDEX sees them as they looked when the universe was young.

The goal is to see how fast the galaxies were moving away from us at the time. That will help scientists determine how the effect of dark energy has changed over time — and perhaps what dark energy is. Dark energy makes the universe expand faster as it ages. But scientists don’t know what it is.

The HETDEX catalog covers observations from the project’s start, in 2017, through the middle of 2020. It includes more than 50,000 of the type of galaxy the project is studying. But it also includes about 135,000 other galaxies and many other objects.

In addition, online volunteers around the world have classified a quarter of a million galaxies in the HETDEX observations — results for future catalogs.

We’ll talk about another big-data project tomorrow.
 

Script by Damond Benningfield

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Mars is named for the Roman god of war. That’s because the planet’s red color reminded Roman skywatchers of blood. But ancient Rome isn’t the only culture that named the planet for its vivid color. In ancient Egypt, it was “the Red One.” In China, it was “the fire star.” And in Arabia, it was simply “fire.”

Mars looks redder from afar than from up close. Pictures from orbiters and landers show that most of the surface has a more subtle hue: butterscotch. But big patches of it show other colors: gold, brown, tan, and even green. The color varies depending on the minerals at the surface.

And even in the red areas — make that butterscotch — the color is only skin deep. The color comes from a layer of powdery dust that coats much of the surface. Across most of the planet, it’s only a few millimeters thick. And even at its deepest, it’s only a few feet thick.

The dust consists of iron oxides — rust. On Earth, rust usually forms in the presence of water. On Mars, though, it may form from reactions with the atmosphere, or even from erosion by the winds. The winds blow the dust around, and suspend a lot of it in the atmosphere — making it look yellow or red as well. Beneath that veneer, the rock tends to be darker — chasing away the “red” in the Red Planet.

Look for Mars quite close to the Moon this evening. It looks like a fairly bright star. The glare of the Moon washes out its color — whatever it is.
 

Script by Damond Benningfield

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The first discovery of the Space Age was two intense radiation belts that encircle Earth. They’re called the Van Allen Belts in honor of James Van Allen, the scientist who led the team that found them. And scientists are still learning about them today.

The belts contain charged particles that are trapped by Earth’s magnetic field. Some of the particles come from the solar wind. Others are created by interactions between cosmic rays and Earth’s atmosphere.

The inner belt stretches from altitudes of a few hundred to a few thousand miles. The outer belt extends far beyond that. Most of the time, there’s a gap of a few thousand miles between them.

But a few years ago, a pair of probes — also named for Van Allen — found that the belts are dynamic. They expand, contract, and vibrate in response to storms on the Sun. At times, the gap between them can fill in, creating a single super-belt. The inner belt can expand to within just a couple of hundred miles of Earth’s surface. And the mixture of particles in the belts can change.

Understanding the belts is important for space flight. Most satellites generally stay below the belts. But any craft that spends much time in the belts gets zapped with a hefty dose of radiation — enough to fry unprotected systems. So spacecraft operators need to know what to expect from the belts so they can shield their hardware — from one of the many hazards of space flight.
 

Script by Damond Benningfield

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As we move toward summer here in the northern hemisphere, we can look forward to longer, warmer days. Most of the other planets go through cycles of seasons as well. But not Venus. There’s nothing to cause the seasons to change. So the climate stays the same all year across the entire planet.

Venus is the brilliant “evening star.” It’s below the crescent Moon this evening. The star El Nath is closer above the Moon, with Aldebaran, the bright orange eye of the bull, well to the lower left of Venus.

The seasons on Earth are caused by our planet’s tilt on its axis. For part of the year, the north pole tips toward the Sun, bringing longer, warmer days to the northern hemisphere. And for the rest of the year, the south pole tips sunward, bringing light and heat to the southern hemisphere.

Venus is flipped upside down compared to Earth and most other planets. But its tilt relative to the Sun is tiny — not nearly enough to create seasons.

The seasons on some planets are also influenced by their distance from the Sun. Mars’s distance varies quite a bit, for example, making the seasons in the southern hemisphere more extreme than those in the north. Here again, though, Venus is well behaved. Its distance from the Sun varies by less than any other planet — not enough to create any seasonal changes.

So daylight stays the same across the entire planet all year ’round, and so do temperatures — about 860 degrees Fahrenheit.
 

Script by Damond Benningfield

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The Moon passes through some crowded territory the next couple of nights. Its most prominent companion is Venus, the beautiful “evening star.” Venus is close to the upper left of the Moon tonight. And a bright true star is a little farther to the left of the Moon: Aldebaran, the bright orange eye of Taurus, the bull.

And here’s something interesting about the trio — and about every other object in the night sky. We see all of them at the same moment in our own timeline — but not in theirs. We see the Moon, Venus, Aldebaran, and everything else as they looked at different moments in the past.

That’s because the universe has a speed limit — the speed of light. It’s 670 million miles per hour. But this speed limit is enforced by the laws of physics, so there’s no way to cheat and squeeze in a little extra.

As a result, it takes time for light to travel from a star or planet to our eyes. And the amount of time depends on its distance.

The Moon, for example, is a little less than a quarter of a million miles away, so the sunlight reflected from its surface takes about one and a third seconds to reach us.

Venus is almost a hundred million miles away right now — almost nine minutes at lightspeed. And Aldebaran is four million times farther than that. It takes light 65 years to cross that immense gulf — a distance of 65 light-years.

We’ll have more about the Moon and its companions tomorrow.
 

Script by Damond Benningfield

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A meteor shower that’s been around for at least 2700 years is at its best the next couple of nights. It’s best viewed between about midnight and dawn. And the Moon sets early, so it won’t interfere with the sparklers.

The Lyrid shower was first recorded by Chinese astronomers in 687 BC. That’s farther back than any other current shower.

Over the centuries, showers come and go. They’re produced by tiny grains of rock and dirt shed by comets or asteroids. That debris spreads out along the parent body’s orbital path. Earth flies through this path every April. The particles ram into our atmosphere at more than a hundred thousand miles per hour. They vaporize, forming the glowing streaks of light known as meteors or shooting stars.

But meteor showers don’t last forever. The orbits of Earth and the parent comets and asteroids naturally move out of sync. In addition, the comets and asteroids can be pushed around by the gravity of Jupiter and other planets. That changes their paths. So over time, meteor showers come and go. But the Lyrids have stuck around longer than any other shower yet recorded.

The Lyrids are named for Lyra, the harp. That’s because the meteors all appear to “rain” into the sky from near the constellation’s brightest star, Vega. They can zip across any part of the sky, though, so you don’t need to look at Lyra to see them. But the view is best after Lyra rises to prominence, around midnight.
 

Script by Damond Benningfield

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M87 is a beast. The galaxy is bigger than our home galaxy, the Milky Way. It contains many more stars than the Milky Way — trillions in all — and has a total mass up to a couple of hundred times the Milky Way’s. And the black hole in its center may be a thousand times the mass of the Milky Way’s.

One thing that M87 doesn’t have is good looks. Instead of a beautiful spiral, it’s an elliptical galaxy. It looks like a fat yellow rugby ball, with a bright middle surrounded by a hazy puffball of stars. Astronomers aren’t sure how M87 got that shape, but they’re working on it.

Unlike spiral galaxies, where the stars all move in an orderly fashion, the stars in ellipticals move pretty much randomly. The stars’ orbits are stretched out. And ellipticals contain little gas for making more stars.

That may mean the galaxies formed from the mergers or two or more giant spirals. A merger could stir up the stars in the original galaxies, and trigger a huge outburst of star formation as clouds of gas ram together. The remaining gas would then be blown out of the galaxy.

On the other hand, ellipticals could have formed from the collapse of massive clouds of gas. That would give birth to many stars, which then blow away the remaining gas — creating plain but “beastly” galaxies.

M87 is well up in the east-southeast at nightfall, in the middle of a triangle formed by the bright stars Denebola, Arcturus, and Spica.
 

Script by Damond Benningfield

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A rare type of solar eclipse will play out tonight on American clocks, but few people will get to enjoy it. It’ll follow a narrow path from the Indian Ocean to the Pacific. The path will just nick the northwestern corner of Australia and the western tip of Indonesia. Most of it will cross open ocean.

The eclipse is a hybrid — a cross between an annular eclipse and a total eclipse.

All solar eclipses take place when the new Moon passes directly across the face of the Sun. In a total eclipse, the Moon completely covers the Sun, turning the sky dark. In an annular eclipse, the Moon is a little farther from Earth than average, so its disk isn’t quite big enough to completely block the Sun. Instead, a thin ring of sunlight surrounds the Moon.

The first and last hours of this eclipse will be annular. Between those periods, though, it’ll be total, with the Moon barely big enough to cloak the entire Sun. The eclipse gets under way at 9:37 p.m. Central Time, and ends more than four hours later. Viewers flanking the main pathway will see a partial eclipse, with the Moon covering a portion of the Sun.

Those of us in the United States won’t see a thing. But our time is coming. An annular eclipse will sweep across the western and southwestern U.S. on October 14th. Even better, a total eclipse will grace our skies next April 8th, along a path from Texas to Maine. So mark your calendars for these cosmic spectacles.
 

Script by Damond Benningfield

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