StarDate

PAO: The target for the Apollo 11 astronauts, the Moon, at liftoff will be at a distance of 218,096 miles away. LAUNCH CONTROL: Apollo 11, this is the Launch Operations Manager. The launch team wishes you good luck and godspeed.

Astronauts Neil Armstrong, Edwin Aldrin, and Michael Collins were ready for a summer getaway. Instead of heading for Florida, like many other Americans, they were heading away from it. Their destination? The Moon.

Armstrong and Aldrin were scheduled to become the first astronauts to set foot on our satellite world.

A million people were watching the launch from the Florida beaches. And hundreds of millions were watching on live television around the world.

PAO: Four, three, two, one, zero! All engine running. Liftoff! We have a liftoff, 32 minutes past the hour. Liftoff on Apollo 11!

The flight was the culmination of a long race against the Soviet Union. It required billions of dollars, and the efforts of many thousands of engineers, scientists, and others.

NASA had launched a couple of dozen robotic missions to the Moon to develop the technology, to pick landing sites, and to make sure the surface would support a lander. And two Apollo missions had checked out the lander and mothership in lunar orbit — setting the stage for the getaway of a lifetime.

Everything has a name, but we seldom spend much time thinking about what most names mean. Today is Monday, for example. It’s the first day of the work week. But the name means “Moon’s day.” In fact, all the days of the week are named for astronomical objects. Some of the names come from old English, while others come from their Scandinavian equivalents.

You might think of the connection to the Moon if you look at tonight’s sky, because the almost-full Moon arcs low across the south. It’s in the sky all night, and casts a brilliant glow across the summer landscape.

Each month’s full Moon has several names of its own. Most of the names were bestowed based on what was happening on Earth at that time of year. In July, for example, thunderstorms were common across parts of the present U.S., summer hay had been harvested, and big game was common. So the Moon was known as the Thunder Moon, Hay Moon, or Elk Moon.

The Moon has a close, bright companion tonight that has an impressive name of its own. The planet Saturn is named for the Roman god of agriculture and plenty, who was honored with one of the most important festivals of the year.

50 years ago tonight, three American astronauts — the crew of Apollo 11 — were preparing to ride a Saturn rocket to the Moon. In their honor, perhaps it’s fitting to add one more title to the list of names for July’s full Moon: the Apollo Moon.

More about Apollo 11 tomorrow.

Script by Damond Benningfield

The Sun is moving southward now — a migration that will continue until the winter solstice, in December. For the people of Hawaii, that brings a bit of an oddity. One day this month, at local noon, the Sun will stand directly overhead. At that moment, objects like telephone poles and standing people will cast no shadows.

For the last few decades, that moment has been known as Lahaina Noon. “Lahaina” is a native Hawaiian word that means “cruel Sun” — a reference to the Sun’s intensity when it’s high in the sky.

The Sun stands directly overhead across a limited range — from the Tropic of Cancer, at 23 and a half degrees north latitude, to the Tropic of Capricorn, at 23 and a half degrees south. Hawaii is the only American state within that band, so the rest of the country misses out on the experience.

Within that geographic range, the Sun passes overhead twice per year — once as it heads north, and again when it heads south. From Hawaii, the Sun stood overhead in May. And now, it’s doing it again, working its way across the islands from north to south. It hit the northern tip of the state a few days ago. It’ll stand above Honolulu on Tuesday, Hilo on the 24th, and the southern tip of the island of Hawaii on the 28th.

A sculpture in Honolulu celebrates the event. The wavy metal structure, called Sky Gate, casts a perfectly round shadow at that moment — the moment of Lahaina Noon.

Script by Damond Benningfield

The biggest fireworks we’ve ever seen in the solar system rocked the planet Jupiter 25 years ago this month. The fragments of a shattered comet slammed into the planet. The impacts created scars that lasted for months. And they created new urgency in the effort to find comets or asteroids that might hit Earth.

Comet Shoemaker-Levy 9 was orbiting Jupiter when the planet’s gravity ripped it apart, in 1992. The remains — a bright “string of pearls” — hit Jupiter two years later. The first of 21 impacts took place on July 16th, 1994.

The pieces of the comet ranged up to about a mile in diameter. And they were traveling at 125,000 miles per hour. So the impacts generated huge fireballs. The largest, in fact, produced as much energy as six million megatons of TNT — hundreds of times more power than all the H-bombs on Earth combined.

Shoemaker-Levy 9 dramatized the fact that comets and asteroids hit planets fairly often. So a few years later, Congress directed NASA to start looking for objects that are potential threats to Earth. And in 2016, the agency opened a new office to coordinate the searches, and to develop plans for deflecting an object that might threaten us.

So far, no known objects are on a collision course. But as the fireworks of 25 years ago show, no planet is safe from the hazards of the solar system.

Look for Jupiter quite close to the Moon tonight, shining like a brilliant star.

Script by Damond Benningfield

Our eyes are perfectly adapted for life under the Sun. Our star radiates most of its light at a narrow range of wavelengths — those that we can see. So that range is known as visible light.

Those wavelengths make up only a narrow slice of the total range of electromagnetic energy, though. The other wavelengths are well outside the range of human vision. And even if we could see them, most of them are blocked by Earth’s atmosphere.

That includes the infrared — wavelengths that are longer than the eye can see. Water vapor absorbs most infrared wavelengths. So to see the infrared sky, astronomers must place their telescopes up high — on mountains, balloons, aircraft, or spacecraft.

One major infrared target is Antares, the brightest star of Scorpius, the scorpion. The star stands below the Moon as night falls this evening. Brighter Jupiter, the largest planet in the solar system, is about the same distance to the lower left of the Moon. We’ll have more about Jupiter tomorrow.

Antares is a supergiant — it’s much bigger and heavier than the Sun. And at visible wavelengths, it shines about 10,000 times brighter.

But the surface of Antares is much cooler than the Sun. To the eye alone, that makes it look reddish orange. But cooler stars emit a lot of their energy in the infrared. So when you add in those wavelengths, Antares is about 60,000 times brighter than the Sun — a brilliance that’s lost on the human eye.

Script by Damond Benningfield

Six million years ago, a brilliant star suddenly vanished from view. The star could no longer produce energy in its core to counteract the inward pull of gravity, so it collapsed. Its great mass was crushed to an infinitely small point, then hidden from the outside universe — behind the event horizon of a black hole.

Although it produces no energy at all, this black hole is one of the most intensely studied objects in the galaxy. It’s known as Cygnus X-1 — the first source of X-rays discovered in the constellation Cygnus.

The X-rays come not from the black hole, but from gas that’s been stripped from a bright companion star. As the gas spirals toward the black hole, it’s heated to hundreds of millions of degrees, so it produces copious amounts of X-rays.

Astronomers have been studying the system for almost half a century. But it wasn’t until this decade that they nailed down the details.

They measured the distance to Cygnus X-1 at 6,000 light-years. That allowed them to accurately measure the mass of the black hole — 15 times as massive as the Sun. And they also measured how fast the black hole is spinning — about 800 times per second.

Those numbers helped astronomers calculate when the black hole was born, which indicated how it was born. The original star probably didn’t explode as a supernova, which is the birth process for many black holes. Instead, it simply collapsed — giving birth to a black hole.

Script by Damond Benningfield

One of the favorite constellations of summer soars high across the sky this month: Cygnus, the swan. It stretches across the east and northeast at nightfall. Its brightest stars form a pattern that really does look like a graceful swan, soaring through the glow of the Milky Way.

Its brightest star is Deneb, at the swan’s tail. It’s one of the most impressive stars in the galaxy — it’s far bigger, heavier, and brighter than the Sun.

But no less impressive is the star that marks the center of the swan, where its outstretched wings meet its long body. It’s called Sadr, a name that means “the hen’s breast.”

Like Deneb, it’s a supergiant. It’s about a dozen times as massive as the Sun, hundreds of times wider, and about 35,000 times brighter. That makes it easy to pick out even though it’s around 1800 light-years away.

Supergiants are the biggest and most massive of all the stars. They “burn” through their hydrogen fuel in a hurry, so they live short lives — in the millions of years, versus billions of years for stars like the Sun.

And when they die, they go out with a titanic explosion known as a supernova. And if the estimates of Sadr’s mass are correct, that’s exactly the fate that awaits it, sometime in the next few million years.

So look for Cygnus flying high across the sky tonight, with its brightest star, Deneb, at the northeastern point of the Summer Triangle. More about Cygnus tomorrow.

Script by Damond Benningfield

The planet Saturn gives more than it gets. It radiates almost twice as much energy into space as it receives from the Sun. That internal heat powers most of the planet’s complicated weather.

Saturn is nine and a half times farther from the Sun than Earth is, so each square foot of the giant planet receives only about one percent as much sunlight. That’s not enough energy to power the storms seen in Saturn’s thick atmosphere. So most of the energy has to come from inside.

There are a couple of leading ideas for the sources of Saturn’s internal heat. One is that at least some of it is left over from Saturn’s formation, stored in its core.

The other says there’s a “rain” of liquid helium. As the droplets descend through Saturn’s great bulk, they pick up speed. As they move into denser layers, friction slows them down, which generates heat. The heat rises back toward the surface, where it powers big storms and some of the fastest jet streams in the solar system. Every few decades, a monster storm breaks out. It can cover an area many times bigger than Earth, and last for months — all powered by Saturn’s own heat source.

And right now, you can’t tell that Saturn receives little sunlight just by looking at it. The planet is shining like a bright golden star. In fact, it’s at its brightest for the entire year. Saturn is low in the southeast as night falls, scoots across the south during the night, and sets around sunrise.

 
Script by Damond Benningfield

As far as anyone knows, Galileo Galilei was the first person to look at Saturn through a telescope. And the sight was astounding. He saw what looked like “bumps” on either side of the planet. He thought they were giant moons.

A half-century later, in 1659, Christiaan Huygens looked at the planet with a better telescope. He saw some space between Saturn and the bumps. He suggested that the bumps weren’t moons, but instead were formed by a wide, flat ring around the planet.

We’ve been learning about the rings ever since. Better telescopes allowed astronomers to see them in more detail. And spacecraft have provided even more detail.

The first new detail was seen by Jean-Dominique Cassini, who discovered a dark gap in the ring. That indicated that there’s more than one ring. In fact, thanks to visits by spacecraft, today we know that there are thousands of them. Some are braided, and some form “ringlets” instead of complete rings.

The rings are held in place by the gravity of small moons orbiting within the rings. And the rings consist mainly of small bits of ice, with some rock and dust mixed in — beautiful features for a well-studied planet.

And Saturn is well placed for more studies. It’s lining up opposite the Sun, so it’s in view all night. It’s brightest for the year, too. It looks like a bright star low in the southeast at nightfall, and crawling across the south during the night.

More about Saturn tomorrow.

Script by Damond Benningfield

Saturn is shining at its absolute best right now. The planet lines up opposite the Sun, so it rises around sunset and remains in the sky all night. It’s passing closest to us for the year as well, so it shines at its brightest. It’s low in the southeast as darkness falls. It looks like a golden star, outshined by only a handful of other nightlights.

Saturn is a giant — almost 10 times Earth’s diameter. It’s topped by layers of clouds in shades of yellow, white, and tan. Some of the clouds form whirling vortexes that can be thousands of miles across.

The most impressive of these are anchored to Saturn’s poles. The system at the north pole has six sides, which may stretch hundreds of miles high. The one at the south pole looks like a hurricane, with an “eye” that’s more than half as big as Earth.

The north-pole hexagon has remained stable since it was first seen four decades ago. Each side is wider than Earth. The structure may be a type of wave that circulates around the top of the planet. Another hexagon appeared above it a couple of years ago. That could mean the hexagon towers hundreds of miles high.

The storm at the south pole looks like an earthly hurricane. It has a couple of spiral arms wrapped around a large eye. And like hurricanes, there’s a wall of clouds around the eye. The clouds are dozens of miles tall — outlining a steady “eye” at Saturn’s south pole.

We’ll have more about Saturn tomorrow.

Script by Damond Benningfield