StarDate

The stars are vanishing. Don’t worry, they’re all still there. It’s just that most of us can’t see them. And a recent study says the problem is even worse than expected.

The problem is called skyglow. It’s a glare caused by streetlamps, billboards, and other outdoor light sources. A lot of their light shines up into the sky. It reflects off of molecules and particles in the atmosphere, filling the sky with light.

Scientists have used instruments aboard satellites to try to measure that light. In 2017, for example, a satellite found that light pollution around the world was increasing by about two percent per year.

But the satellite wasn’t sensitive to the wavelengths produced by LEDs, which today make up a huge fraction of the outdoor-lighting market. And the satellite couldn’t pick up the light that was being scattered from side to side.

So a scientist in Germany teamed up with Globe at Night — an online network of volunteers. They kept an eye on the night sky, and compared what they saw to charts showing different levels of skyglow. And what they reported was a lot worse than what the satellite saw. Around the world, skyglow is going up by almost 10 percent per year.

One researcher described it this way: If a child is born today in a city where you can see 250 stars at night, by the time it turns 18, it’ll see just 100 stars. The rest will be hidden by the glow of the not-so-dark night sky.
 

Script by Damond Benningfield

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In September of 2021, the Perseverance rover was working quietly on the surface of Mars when this happened: [AUDIO: dust devil]. It might not sound like much, but on Mars, it’s the most exciting thing you’re ever likely to see: a dust devil — a spinning column of air that’s like a mini-tornado. This one swept over the top of the rover, blowing away some of the dust that had settled on it.

Dust devils are common sights on Mars, just as they are in many regions of Earth. They form when the ground is warmed by the Sun, causing the air above it to rise. It forms a spinning vortex that crawls along the landscape. On Mars, dust devils can be more than a mile high and half a mile wide — much larger than on Earth. And as they blow the dust off the Martian rocks, they leave winding trails that look like abstract tattoos.

Dust devils may generate small crackles of electricity: lightning. They’re too small and faint to see. But giant dust storms may produce more powerful outbursts. Research says even those shouldn’t be strong enough to harm either people or their machines. But they might produce a soft glow around a storm — the glow of dust blowing in the Martian winds.

Look for Mars well up in the west at nightfall. It looks like a fairly bright orange star. Tonight, it lines up with the twins of Gemini. The stars are to the right of Mars, with brighter Pollux closer to it.
 

Script by Damond Benningfield

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Anyone who’s self-conscious about their weight might not want to visit Jupiter. Surface gravity on the solar system’s largest planet is more than twice as strong as Earth’s. So a person who weighs 150 pounds on Earth would weigh about 380 pounds on Jupiter.

Jupiter doesn’t actually have a surface for you to stand on. The planet is a big ball of gas, with nothing “solid” until you drop tens of thousands of miles below its cloud tops.

For comparison purposes, though, scientists have come up with a definition for the “surface” of Jupiter and the solar system’s other giant planets. It’s the depth in the atmosphere where the pressure is equal to the surface pressure on Earth.

That’s far below the tops of Jupiter’s highest clouds. But there are zones in the atmosphere where the clouds aren’t nearly as high, so the “surface” isn’t necessarily below them.

All of this means that no one will ever walk on Jupiter. It might still be possible to visit the planet, though. Visitors could float through the sky in balloons or blimps, or cruise in specially designed aircraft. But the seats would need to be well padded — to handle the passengers’ extra weight on the solar system’s largest planet.

Jupiter is just climbing into view in the eastern dawn sky. It looks like a bright star, but it’s so low that you need a clear horizon to spot it. It’s easier to pick out tomorrow because it’s a whisker away from the crescent Moon.
 

Script by Damond Benningfield

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Spaceflight is never easy. Just ask the folks who operated Skylab, the first American space station.

It launched on May 14th, 1973. Just a minute into the flight, though, it was in trouble. A protective shield ripped away. It took a solar panel with it, and jammed a second one shut. Without the shield and the panels, there wasn’t enough power to support the station, and the temperature inside the lab soared to 130 degrees. The launch of the first crew of astronauts had to be scrubbed.

Skylab was as roomy as a three-bedroom house. It was designed to house three astronauts for up to two months at a time. They would watch Earth and the Sun, conduct experiments, and study how their bodies adapted to life in orbit. Unless engineers could find a way to fix the problems, though, the station would have to be abandoned.

It took a few days, but they worked out a plan. An astronaut would stand in the hatch of his Apollo spacecraft. He would use a pair of bolt cutters on a long pole to free the jammed solar panel. Later, another astronaut would poke a parasol through an airlock on the back of the station. It would open up and reflect the sunlight, bringing down the temperature.

And it worked. The first crew made the repairs, then started on its main mission. Two other crews followed. The last remained aboard for 84 days — a record that stood for several years — thanks to the efforts of the engineers who saved Skylab.
 

Script by Damond Benningfield

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LAUNCH CONTROL: T-minus 20 seconds, and the countdown continues to go smoothly.

Skylab, the first American space station, launched from Cape Kennedy 50 years ago today.

LAUNCH CONTROL: We have, ignition sequence has started. 6, 5, 4, 3, 2, 1, zero. And we have a lift-off. The Skylab lifting off the pad now, moving up....

Skylab used the third stage of a Saturn Moon rocket. It was as roomy as a three-bedroom house. Crews of three astronauts would fly up separately, and spend up to two months at a time aboard the station. They would look at Earth and the Sun, conduct experiments, and study how their own bodies adapted to long stretches of weightlessness.

From the beginning, though, the station was in trouble.

MISSION CONTROL: Skylab space station now in orbit. Still some doubt in the minds of flight controllers here in Mission Control as to whether the main solar panels on the workshop have indeed deployed. ...

A minute after launch, a shield designed to protect the station from tiny space rocks ripped away. It took one of two electricity producing solar panels with it, and jammed the other one shut. Without that second panel, there wouldn’t be enough power to support Skylab’s work.

The first crew was already on the launch pad, ready to head for orbit shortly after Skylab itself. But the astronauts had to stand down while engineers tried to understand the problem — and see if there was a way to save the first American space station.

More tomorrow.

Script by Damond Benningfield

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What would you do if you found yourself with a few extra Moon rockets? NASA faced that situation in the early 1970s. The Nixon Administration cut its budget, so NASA cancelled the final three planned Apollo missions to the Moon. But the agency had already bought the rockets. It turned one of them into the first American space station, Skylab.

The station used the third stage of the Saturn 5 booster. Engineers stripped out the engines and fuel tanks. They installed living quarters, lab equipment, Earth-watching cameras, and a Sun-watching telescope — the most powerful up to that time. Crews of astronauts would spend up to two months aboard the station.

Skylab was launched 50 years ago tomorrow. It quickly ran into trouble. Engineers worked out solutions, though, saving the station. The other Saturn rockets became exhibits in museums, where they remain today.

The change in plans meant NASA had to abandon three possible sites on the Moon — all with high scientific value. The exact sites hadn’t been locked in. But some possibilities included the large craters Tycho and Copernicus. They formed fairly recently, so they would have provided different kinds of materials from most of the Apollo sites.

Copernicus is about 60 miles across. If you look at the Moon early tomorrow, the crater’s near the middle of the line that separates night from day — a lost opportunity that gave NASA a spare Moon rocket.

More about Skylab tomorrow.

Script by Damond Benningfield

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What time is it?

To answer that, you’d probably look at your smartphone or a watch linked to your phone. And using orbiting satellites, those devices would provide the time with an accuracy of a few billionths of a second.

With dozens of missions planned for the next few years, scientists are looking at setting up a similar system for the Moon. It would provide precise timing for probes and astronauts in orbit and on the surface. That would help with navigation, science observations, and more. To make it work, though, everyone will have to agree on some basics of time.

One question is whether the entire Moon should be one big time zone, so clocks would read the same around the entire world. Another is whether lunar time should be linked to an earthly time system.

Clocks on the Moon tick at a different rate than those on Earth. GPS satellites compensate for the effects of Earth’s gravity and their own speed. But the Moon’s gravitational pull is weaker than Earth’s, and satellites move slower. That means a clock on the Moon gains about 56 millionths of a second per day relative to clocks on Earth. For precise navigation and science, that’s critical — a big difference in the ticking of a lunar clock.

The Moon is in the early morning sky right now. Tomorrow, it climbs into good view by a couple of hours before sunrise. And it has a close companion — the planet Saturn looks like a bright star to the upper left of the Moon.
 

Script by Damond Benningfield

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Getting a space telescope ready to fly takes a lot of testing. But there’s no “once-size-fits-all” test rack. In many cases, scientists have to create new equipment just to check things out. And sometimes, that equipment can be adapted for other uses.

Consider NICER, an X-ray telescope that’s been operating aboard the International Space Station since 2017. It studies neutron stars, black holes, and other extreme objects.

One of NICER’s tools is recording extremely fast changes in brightness — as little as millionths of a second. Before it was launched, though, there was no way to produce such quick X-ray flashes for testing. So mission scientists invented their own X-ray machines — small instruments that could produce pulses of a few millionths of a second or longer.

A researcher at Massachusetts General Hospital heard about the new invention, and saw an opportunity. Conventional cat-scan machines are big and heavy, and they have to move around to provide 3D X-rays. But he adapted the NICER test devices to provide a stationary ring. It was smaller than conventional machines, and it could focus its X-rays on areas that doctors really wanted to see. It would require smaller doses of X-rays, and it had the potential to be less expensive.

In early small-scale tests, the new scanner worked well. So today, researchers are scaling it up — looking into the human body with machines designed to look into dead stars.
 

Script by Damond Benningfield

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A neutron star is among the most extreme objects in the universe. It’s so densely packed that a teaspoon of its matter would weight 10 million tons. Its gravity is so strong that an object dropped from shoulder height would smash into its surface at a few percent of the speed of light. And its magnetic field can be strong enough to rip away your wristwatch from as far away as the Moon.

But it’s also tiny — no bigger than the size of a city. And that’s a problem for the scientists who study neutron stars. They’re so small that they’re hard to measure. And without an accurate idea of a neutron star’s size, scientists can’t be sure what’s going on inside it.

One tool for finding out is NICER — the Neutron Star Interior Composition Explorer. It’s an X-ray telescope that’s been on the International Space Station since 2017.

The interior of a neutron star marks the final step before matter is basically crushed out of existence to form a black hole. So it’s unlike anything else in the universe.

It could be a big ball of neutrons. Or the neutrons could have dissolved into a “soup” of smaller particles. NICER’s observations have already helped scientists rule out some of the possibilities. But it’s looking at even more neutron stars to help scientists narrow down the options of what’s happening inside these amazing objects.

NICER technology is also helping look inside the human body; more about that tomorrow.
 

Script by Damond Benningfield

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In 2011, MIT scientist Rainer Weiss was inspecting his brainchild: LIGO, an observatory for catching gravitational waves — tiny ripples in spacetime created by the motions of massive objects. It hadn’t yet found anything. But Weiss mused about what he hoped it would find.

WEISS: The thing that I’m hoping for — I hope I’m still alive when it happens — is that we detect a black hole either in its formation or in a coalescence of black holes. That, to me, would be the most remarkable output of this whole project.

LIGO hasn’t caught the birth of a black hole, but it has discovered 90 gravitational-wave events — almost all of them the mergers of black holes. The discoveries confirmed the existence of black holes and gravitational waves. And they earned Weiss and two colleagues the 2017 Nobel Prize in Physics.

The observatory has two sites, one in southern Washington and the other in Louisiana. They use long vacuum tunnels, lasers, and ultra-precise mirrors to “hear” the waves, which are smaller than the particles in the nucleus of an atom.

LIGO shut down when Covid hit, but it’s ready to get back to work this month. It’s been upgraded, making it much more sensitive. And it’ll team with observatories in Japan and Italy, making it even more sensitive. So scientists expect to find many more merging black holes and other objects, out to ranges of billions of light-years — remarkable discoveries from a prize-winning observatory.
 

Script by Damond Benningfield

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