StarDate

The Moon and three other bright lights form a beautiful diamond in tomorrow’s dawn sky. Going clockwise from the Moon, the points of the diamond are the planet Jupiter, which is the brightest of the three; the planet Mars; and the star Elnath, the tip of one of the horns of Taurus.

The Sun illuminates about a third of the side of the Moon that’s facing our way. The most prominent feature in the sunlight is a giant dark patch known as the Ocean of Storms. It’s one of the largest features on the Moon. It covers one and a half million square miles – about one-tenth of the Moon’s entire surface.

A half dozen probes have landed in that vast region, including the Apollo 12 mission in 1969.

The most recent lander was Chang’e 5. The Chinese mission brought about four pounds of rocks and dirt back to Earth, in 2020. The samples indicated that the “ocean” formed about two billion years ago, when the Moon was about half of its current age. That makes the Ocean of Storms the youngest of the Moon’s big volcanic plains.

The feature may have formed when molten rock pushed its way to the surface through long, wide cracks. But the origin is still being debated. Some scientists say it formed after a massive asteroid slammed into the Moon. The impact gouged a wide crater that later filled with lava – forming a giant “ocean” on the Moon.

The Moon will stand close to Mars on Wednesday; more about that tomorrow.

Script by Damond Benningfield

The Sun has been feisty this year. It’s produced some monster storms that have pelted Earth with radiation and charged particles. That’s disrupted some communications, air travel, and other daily activities.

There’s evidence that the Sun has been much feistier in centuries past. If such major outbursts happened today, they could be really bad for modern technology. But the big ones in the past are good for archaeology. They’re helping scientists nail down the dates of some ancient human activities.

The Sun is especially active every 11 years or so. It blasts out giant clouds of charged particles. When the particles hit the atmosphere, they create cascades of other particles. That includes a radioactive form of carbon. Trees take up some of this carbon. The more active the Sun is, the more they absorb.

By analyzing the ratio of different forms of carbon in tree rings, scientists can determine which years were especially “stormy.” And that gives them a way to date human settlements.

Earlier this year, for example, a team studied rings in logs that were used to make houses and other structures at a site in Greece. The scientists found rings that recorded a busy year for solar activity. It corresponded to a previously discovered peak, in 5259 BC. Counting all of the tree rings showed the site had been inhabited for at least a couple of hundred years – including a time with an especially feisty Sun.

Script by Damond Benningfield

Stars aren’t always what they seem. Consider the two brightest stars of Lyra. The constellation’s leading light is Vega. It looks 20 times brighter than the second-ranked star, Sulafat. But that’s only because Vega’s much closer. If you lined them up at the same distance, Sulafat would look 60 times brighter than Vega.

The difference is caused by their stage in life. Vega’s in the prime of life. It’s “fusing” the hydrogen atoms in its core to make helium, releasing energy in the process. Vega is more massive than the Sun, so those reactions happen at a much faster rate – making Vega about 40 times brighter than the Sun.

Sulafat has moved into the next stage of life. It’s converted the hydrogen in its core to helium. Now, it’s fusing hydrogen in a thin layer around the core. That’s caused its outer layers to puff up, helping the star shine about 2400 times brighter than the Sun.

Eventually, Sulafat will start fusing the helium in its core. That’ll make it even bigger and brighter. Then it’ll shed its outer layers, leaving only its dead core. Vega will experience the same fate – more than a billion years from now.

Lyra is high overhead at nightfall. It’s easy to spot because Vega’s one of the brighter stars in the night sky. Four stars outline a tilted, flat box to the lower right of Vega. Sulafat is at the corner of the box that’s farthest from Vega.

Script by Damond Benningfield

In the early 20th century, much of the world had “Mars fever.” Percival Lowell had mapped what he called “canals” on Mars, built by a dying civilization. H.G. Wells published “War of the Worlds,” about a Martian invasion. Inventor Nicola Tesla reported hearing possible signals from Mars. So there was a lot of interest in the Red Planet. In 1901, Richard Taylor wrote this march to capture the enthusiasm – “A Signal From Mars.”

People listened for signals 100 years ago this week. Mars was passing especially close to Earth. Astronomer David Todd thought Martians might try to contact us. So he organized a campaign to listen for radio transmissions.

Among others, he worked with Charles F. Jenkins, who’d built a device that could transmit photographs via radio. Jenkins later developed early forms of television.

Starting on August 21st, 1924, Jenkins recorded radio waves on a roll of photographic paper whenever Mars was in the sky – more than 20 hours in all. Todd said he saw faces in the squiggles on the paper. But Jenkins thought it was nothing but noise.

Technicians at some radio stations reported hearing odd sounds during the hunt. Most of the sounds came from Earth, although some might have been natural radio waves from astronomical objects.

But none of them came from the Red Planet. There were no signals from Mars.

Script by Damond Benningfield

Army and Navy radio stations around the world had something extra to listen for 100 years ago this week: Mars. The Red Planet was passing closer to Earth than it had in centuries. A retired astronomer thought that Martians might take advantage of the encounter to beam greetings to the neighbors. So he organized an effort to hear the transmissions.

David Todd had led the astronomy program at Amherst College in Massachusetts. Most scientists of the day said there was no chance of a Martian civilization, but Todd disagreed.

Radio pioneers Nicola Tesla and Guglielmo Marconi had reported hearing odd signals from space several years earlier. Some interpreted the signals as broadcasts from Mars. And Percival Lowell had created maps of Martian “canals” – built to bring water from the polar ice caps to a dying civilization. All of that convinced Todd that it was worth listening for Martian broadcasts.

Todd asked radio stations to go silent for five minutes of every hour for several nights. Only one complied – station WRC, in Washington, D.C. But technicians at other stations listened for odd signals. The military instructed its radio operators to listen as well, but only if it didn’t interfere with normal operations. And it made its leading cryptographer available to decode any Martian messages.

Todd also enlisted the help of a television pioneer, and we’ll have more about that tomorrow.

Script by Damond Benningfield

A century ago, most scientists thought Mars was devoid of animal life. Many thought it might contain plants, or at least primitive life such as lichens.

But in popular culture, Mars was abuzz with life. That was thanks to Percival Lowell. He saw “canals” crisscrossing the planet – structures built to save a dying civilization.

Lowell was born to a distinguished family in Boston. He worked in the family business, then traveled around Asia. But during that time he developed an interest in Mars. In the late 1800s, he built his own observatory to study Mars, in Flagstaff, Arizona.

During an especially close passage of Mars, in 1877, an Italian astronomer had described some lines he saw on the planet as “channels” – natural features. But Lowell thought of them as “canals” – created by living beings.

In Lowell’s reckoning, Mars was losing its atmosphere and getting colder. That turned it into a desert. Survivors built the canals to sustain their cities. Lowell’s books and lectures about Mars were popular, so the general public thought of Mars as inhabited.

But by 1924, it was clear to most scientists that Mars was too cold and dry to support much life. But one thought a civilization could still exist – perhaps supported by Lowell’s canals. So during another close passage of Mars, a century ago this week, he launched a project to listen for Martian radio broadcasts. More about that tomorrow.

Script by Damond Benningfield

The Moon will squeeze past the planet Saturn tonight. They climb into view about 9:30 or 10. Saturn looks like a bright star. As seen from most of the United States, it’ll pass just a fraction of a degree from the Moon.

One of Saturn’s moons is one of the more interesting objects in the solar system. Geysers of water and ice erupt from cracks in its crust. The geysers feed one of Saturn’s rings. And the source of the geysers – a global ocean of liquid water – is considered one of the best places to look for life.

Enceladus isn’t very big – a bit more than 300 miles in diameter. It’s caught in a gravitational tug-of-war between Saturn and another moon. That stretches and squeezes Enceladus, generating heat. The heat has melted some of its ice, creating a global ocean well below the surface. The ocean could be several miles deep.

Some of the ocean’s water escapes through cracks in the crust near the south pole. Known as “tiger stripes,” they’re warmer than the surrounding landscape. They spew enough water and ice to fill up an Olympic swimming pool in less than an hour. Some of the ejected material enters orbit around Saturn, forming a wide but faint ring.

The ocean appears to contain all the ingredients for life: water, a source of energy, and a good mix of chemicals. Future missions may fly through the geyser plumes to hunt for microscopic life.

We’ll talk about a search for intelligent life tomorrow.

Script by Damond Benningfield

A European mission to study the moons of Jupiter is getting some help. Even though it was launched on Europe’s most powerful rocket, it’s so heavy that it needs some extra “kicks” to reach the Jovian system. It’ll get two of those kicks this week – one from the Moon, the other from Earth.

The mission is JUICE – Jupiter Icy Moons Explorer. It’ll study Jupiter’s largest moons – Ganymede, Callisto, and Europa. All three are made of ice and rock, with vast oceans of liquid water below their crusts. Europa’s ocean is closer to the surface than the other two. And it’s considered a possible habitat for microscopic life.

JUICE will make a total of 35 close passes by the three moons. After that, it’ll settle into orbit around the largest moon, Ganymede.

To reach Jupiter and its moons, the craft will make several close passes by other bodies – the Moon, Earth, and Venus. During each encounter, it’ll “steal” a bit of gravitational energy. That acts like a slingshot, accelerating the craft.

This week’s encounters are the first. JUICE will fly past the Moon, then swing by Earth just a day and a half later. Along with three more encounters in the coming years, that will help JUICE reach Jupiter in the summer of 2031 – beginning a long reconnaissance of some icy moons.

We’ll talk about another intriguing icy moon tomorrow.

Script by Damond Benningfield

Jupiter stands high in the east at daybreak. It’s the brightest point of light in the sky at that hour, so you can’t miss it.

Jupiter’s moon Io is the most volcanic world in the solar system. But some planets in other star systems could give Io some competition. Their daysides could feature hundreds of giant volcanoes, and be paved with molten rock.

One example is LP 791-18d. It’s about the same size and mass as Earth. It orbits a small, cool star. But it’s so close to the star that its surface is extremely hot. And it’s made even hotter by the gravitational tug of two other worlds. They squeeze and stretch the planet’s interior, heating it enough to create volcanoes.

A recent study says that volcanic gases could form an atmosphere. As the air circulates to the nightside, water could condense and fall to the surface – perhaps making that side an abode for life.

Webb Space Telescope recently found evidence of a thick atmosphere around another volcanic world, HD 104067d. The planet is bigger and heavier than Earth. Like the other volcanic planet, it’s quite close to its star. And it’s tugged by the gravity of other planets in the system, heating its interior and forming volcanoes.

Its atmosphere appears to carry a lot of heat from the dayside to the nightside. So the planet isn’t a likely home for life – a hellish world of giant volcanoes.

Tomorrow: helping hands.

Script by Damond Benningfield

The stars of the Summer Triangle look a lot alike. Vega, Deneb, and Altair are among the 20 brightest stars in the night sky, and they all shine almost pure white. Vega and Altair really are alike. But except for the way it looks to our eyes, Deneb is nothing like the other two.

The triangle is high in the eastern sky at nightfall. It’s easy to see even through the glare of the almost-full Moon. Vega is the highest and brightest of the three stars. Deneb stands to the lower left of Vega, with Altair farther to the lower right.

Vega and Altair are both about twice the size and mass of the Sun, and a good bit brighter. And both of them spin rapidly – so fast that they bulge outward at the equator. Vega is farther along in its evolution than Altair is. Because of their mass, both stars will spend about a billion years in the “prime” phase of life. That’s compared to about 10 billion years for the Sun.

Deneb is a supergiant – one of the bigger and heavier stars in the galaxy. Some of its details are unclear because its distance is uncertain. It could be about 1500 light-years away, or about 2600. Either way, we know that it’s about 20 times the mass of the Sun, and up to 200 thousand times the Sun’s brightness. It’s no more than 10 million years old, with almost no time left. Before long, it’ll explode as a supernova, then fade away – and the Summer Triangle will disappear.

Script by Damond Benningfield