StarDate

A recently discovered planet in a star system 130 light-years away is on the border — the dividing line between a planet and a brown dwarf.

HD 206893c is the third member of its system. The main member is a star that’s bigger and heavier than the Sun. It has a distant companion known as a brown dwarf — an object that’s more massive than a planet but not massive enough to shine as a star.

The planet was hinted at by Gaia, a space telescope that’s observing more than a billion stars. A big telescope on the ground provided more details on the system, and even snapped the planet’s picture.

HD 206893c is a little bigger than Jupiter, the giant of our own solar system — and almost 13 times as heavy. That puts it on a border line. Anything less massive is definitely a planet, while anything heavier is most likely a brown dwarf.

Yet the planet is much brighter than most big planets. That suggests that it’s “fusing” a form of hydrogen in its core — something that usually happens in light-weight brown dwarfs. So studying this odd object may help scientists nail down the definitions of both planets and brown dwarfs — and the dividing line between them.

HD 206893 is low in the southeast at nightfall, and is bright enough to see through binoculars. It’s in the constellation Capricornus, not far to the upper right of the planet Saturn, which looks like a bright golden star.
 

Script by Damond Benningfield

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The first of two American solar eclipses is just a month away. It’s an annular eclipse. That means the Moon won’t completely cover the Sun. Instead, sunlight will outline the Moon — a bright “ring of fire.”

The eclipse is annular because the Moon will be several thousand miles farther from Earth than average. At that range, it won’t be quite large enough to totally block the Sun from view.

Eventually, that’s what all solar eclipses will look like. The Moon is moving away from Earth, at about an inch and a half per year. In half a billion years or so, it’ll be so far that it’ll never again completely obscure the Sun. Total solar eclipses will vanish, replaced by annular eclipses with ever-larger rings of sunlight around the Moon.

Annular eclipses still offer a beautiful experience, though. The sky turns dusky, the air cools, and trees produce ring-shaped shadows. And viewed with the proper eye protection, the eclipse itself is quite a sight.

The October 14th eclipse will sweep ashore on the coast of Oregon, then slide southeastward. It’ll pass across six other states before heading into the Gulf of Mexico, near Corpus Christi, Texas, around noon Central Time.

Except for Hawaii, all of the U.S. outside the path of annularity will see a partial eclipse, with the Moon blocking a smaller fraction of the Sun.

The second American eclipse will be an even greater spectacle — a total eclipse, coming up on April 8th.
 

Script by Damond Benningfield

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If you can escape the glow of city lights, this is a great evening to watch the Milky Way. It forms a hazy band of light that stretches high across the sky. It arcs from Scorpius and Sagittarius in the south; through the Summer Triangle, high overhead; then down to W-shaped Cassiopeia, in the northeast.

That band of light is the glow of millions of stars in the disk of the Milky Way Galaxy.

If we could view the galaxy from afar, we’d see several bright, beautiful spiral arms wrapping through the disk. The arms aren’t permanent structures. Stars that are closer to the center of the galaxy take less time to complete an orbit than stars that are farther out. So if an arm was a permanent structure, it would either rip itself apart or wrap tighter and tighter around the galaxy’s core.

Instead, each arm may represent the crest of a wave. The wave circles around the galaxy like a wave of water on the ocean. In a galaxy, the wave squeezes giant clouds of gas and dust ahead of it. The clouds then give birth to new stars. Many of the stars are big, heavy, and bright, so they help outline the spiral arms. A wave also carries along lots of smaller stars, enhancing the spiral arm even more.

As the wave moves along, it compresses a new region of the galaxy. The stars in its wake spread out, and the brightest of them quickly expire. But new stars take their place — riding a wave through our beautiful galactic home.|
 

Script by Damond Benningfield

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Scientists have identified about 200 impact craters on Earth — the aftermath of high-speed collisions with big space rocks known as asteroids. Most of the craters were gouged when the asteroids hit the surface. But in some cases, the asteroids exploded high in the sky. Such a blast can carve a shallow crater and litter the landscape with debris. In fact, we know of several big airbursts that took place above Russia since the start of the 20th century.

Another possible airburst could have created the Taihu Lake basin, in southeastern China. The basin is about 40 miles wide, but only six or seven feet deep.

Geologists have debated its origin for decades. In the 1990s, some suggested an impact origin. But the basin doesn’t quite fit the profile. It’s not deep enough, and the rocks below it don’t have most of the telltale signs of an impact.

One team recently proposed an alternative: an airburst. The stress of plowing through the atmosphere could have caused an asteroid to explode high in the sky. The shockwave could have scooped out the basin.

The team found evidence of an airburst in a layer of sediments from 7,000 years ago. It contains a lot of iron-rich blobs. Many of them are spheres, cones, or rods — shapes that could have been sculpted as blobs of molten rock blasted through the sky at high speed.

The scenario hasn’t been confirmed. Still, it suggests that asteroids don’t have to hit the ground to be dangerous.
 

Script by Damond Benningfield

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When most of us move, we pick existing houses or apartments instead of building from scratch. And that could be an option for future explorers on the Moon. Scientists have identified some structures that could be entryways to roomy accommodations. They’re not secret bases built by aliens. Instead, they’re holes in the ground — “pit” craters that could link up with long, deep caves.

Living on the Moon would be dangerous. There’s no air, the temperatures range from extremely hot to extremely cold, and the surface is pelted by radiation and space rocks. A habitat inside a cave would offer protection from those hazards.

Scientists have identified almost 300 pit craters. Most of them link to underground tubes, which once carried molten lava. When the lava went away, parts of the tubes collapsed, forming the pits. But parts of the tubes remain intact, creating caves that could go on for miles.

A team recently picked out four pit craters that are especially interesting. Their caves could make good habitats for lunar explorers, and provide a lot of information about the Moon’s geologic history.

The leading candidate is in the Marius Hills, on the Moon’s Ocean of Storms. The others are in the Sea of Tranquility, Sea of Cleverness, and Lake of Death — possible addresses for lunar explorers.

The crescent Moon is low in the sky at dawn tomorrow. And it has a brilliant companion: Venus — the “morning star.”

Script by Damond Benningfield

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Navy pilots took to the air 100 years ago today to view one of nature’s most amazing sights: a total solar eclipse. It was the first time that airplanes had been used to study an eclipse. In fact, it was the first attempt at airborne astronomy — studying the universe from above as much of the atmosphere as possible.

Most of the eclipse path was over the Pacific Ocean. But it clipped some islands in southwestern California, then continued across northern Mexico.

Astronomers from around the world set up bases to watch the eclipse — projects that involved years of preparation, dozens of people, and massive logistics efforts. But when the eclipse rolled around, most of them were stymied by clouds.

The U.S. Navy sent up 16 airplanes to watch the eclipse — biplanes with open cockpits. Their main goal was to plot the centerline of the eclipse. That would help astronomers refine their calculations of the Moon’s orbit. A second goal was to snap pictures of the Sun’s corona — its hot, thin outer atmosphere.

Pilots flew at altitudes of one to three miles, across California, Mexico, and the Pacific. They made important observations of the shadow, but none of their pictures worked out — the film was too slow, the airplanes too jittery, the skies too cloudy. But more successful eclipse flights would follow in the coming decades — watching cosmic spectacles from on high.
 

Script by Damond Benningfield

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125 years ago today, the Sun made a big nuisance of itself. A giant storm peppered Earth with radiation and charged particles. That disrupted the telegraph wires across most of the United States for several hours. It also blacked out some phone lines in other parts of the world. On the other hand, it also produced some dazzling auroras — the northern and southern lights.

At the time, people blamed the disruptions on the auroras. Instead, both were caused by a solar storm. A giant sunspot — a dark magnetic storm — scarred the surface of the Sun. An explosion of particles related to the sunspot raced out into the solar system.

When they reached Earth, the particles zapped atoms and molecules in the upper atmosphere, causing them to glow — creating auroras that were bright enough to see during the day. Other particles made it to the surface. They created electric currents that traveled through the telegraph and telephone wires.

Reports at the time said telegraph service was disrupted for hours, across all of the country west of the Rockies. The disruptions came in waves. Most of them lasted for a few minutes, although one kept the lines out of service for an hour.

Bright auroras were reported in the U.S., Europe, and the southern hemisphere. And a scientist in New Zealand said his phone service was wonky at the same time — disrupted by the unruly Sun.
 

Script by Damond Benningfield

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Radio telescopes around the world are listening for the whispers of other civilizations. That includes the Very Large Array — a set of 27 radio dishes that acts as a single giant telescope.

The VLA is conducting a survey of most of the sky. And a few months ago, scientists who are hunting for civilizations in other star systems began tapping into that survey. They’re looking at narrow sets of frequencies that are the most likely to have an intelligent origin.

Scientists also are pondering whether other civilizations could hear us. We produce a constant radio “haze,” including the drone of billions of cell phone calls. And a team recently looked at whether any close-by civilization might be able to “eavesdrop” on those calls.

The team looked at the radio waves that leak into space from some of the most powerful cell-phone towers. It calculated whether that leakage could be picked up by Earth-like radio telescopes at three nearby star systems, including the two closest, Alpha Centauri and Barnard’s Star.

The team found that the signals fade away before they reach any of those stars — you’d need more advanced technology to hear them. But the team is extending its work to include other types of Earthly transmissions, including military radar, orbiting satellites, the network that talks to deep-space missions, and future cell towers. That should tell us whether Earth is loud enough to be heard by ET.
 

Script by Damond Benningfield

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55 Cancri is a busy star system. It consists of two stars and at least five planets. None of the planets is a good home for life, although there could be undiscovered planets that are more welcoming.

The planets have a couple of sets of names. Their scientific designations are 55 Cancri b, c, d, e, and f. But a few years back, the IAU — the International Astronomical Union — gave them proper names: Galileo, Brahe, Lipperhey, Janssen, and Harriot. They’re named for astronomers, or for lensmakers involved in creating early telescopes.

Astronomers have discovered more than 5,000 planets in other star systems. And hundreds more are added to the list every year. That’s a lot of worlds to name.

The scientific designations take the name of the star — a proper name or a catalog name — and add a letter, starting with b. The letters are applied based on the order in which the planets were discovered.

The IAU has held several contests to pick proper names, and it’s adopted about 150 of the suggestions. They come from scores of countries and cultures — named for people, places, animals, and other sources. And if a system has more than one planet, a single theme is applied to all of the planets — like the planets of 55 Cancri.

The system is in the constellation Cancer, which is in the east at first light. The crab is easy to pick out because it spreads to the upper left of Venus, the “morning star.”
 

Script by Damond Benningfield

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The two brightest stars of Taurus, the bull, flank the Moon late tonight. The brighter of the two, Aldebaran, is off to the right of the Moon as they climb into good view, about 1 a.m. The second-brightest star, El Nath, is closer to the left or lower left of the Moon. And it’ll stand even closer to the Moon at first light.

Aldebaran and El Nath are in the same stage of life — they’re giants. Through nuclear fusion, each has burned through the original hydrogen fuel in its core, converting it to helium. Now, it’s burning the hydrogen in a thin shell around the core. At the same time, the core is getting smaller and hotter. Eventually, it’ll get so hot that fusion reactions will fire up in the helium, making the star even bigger and brighter.

Nuclear fusion combines lighter elements to make heavier ones. The process releases energy — a lot of it. The core of the Sun, for example, “fuses” 700 million tons of hydrogen every second, producing 695 million tons of helium. The other five million tons are converted to energy — and that’s what makes the Sun shine.

Even at that rate of consumption, the Sun has so much hydrogen in its core that it won’t run out any time soon. It’s been burning through the hydrogen for four and a half billion years, and it’ll keep doing so for at least five billion years longer — powered by its own giant nuclear reactor.

Tomorrow: naming the planets in other star systems.
 

Script by Damond Benningfield

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