StarDate

The Sun’s closest planets will be playing a game of criss-cross in the evening sky the next few nights. They drop from view pretty early, though, so there’s not a lot of time to enjoy the show.

Venus is the brighter of the two worlds. It’s the brilliant “evening star.” It’s the second planet out from the Sun. Right now, it’s getting ready to cross between the Sun and Earth in early June, so it’s dropping lower in the sky each evening. It’ll vanish for a few days, then return to good view in the morning sky by the middle of the month.

The other world is Mercury, the Sun’s closest planet. It’s emerging from behind the Sun, so it will climb higher in the sky for several nights. It’ll remain in good view for about three weeks before it drops back into the twilight glare.

Mercury is only a fraction as bright as Venus. In part, that’s because it’s more than three times farther from us than Venus is. Mercury is smaller than Venus is, too, and its surface is much darker. As it climbs away from the Sun, though, it’ll look brighter, making it an easy target.

Tonight, look for Mercury below Venus not long after sunset. They set by about 10 o’clock. The planets will be closer together tomorrow night, with Mercury climbing just above Venus by Friday. And the crescent Moon will join them this weekend, creating a beautiful conjunction in the fading twilight.

Script by Damond Benningfield

Much of what we see in the night sky is an illusion. Some of the brighter stars aren’t really all that bright. They look impressive only because they’re close by. There’s one group of stars, though, where what you see is what you get.

Four stars in the constellation Corvus, the crow, form a small lopsided box that resembles a sail. It’s in the south as night falls. The star at the top left corner of the sail is known as Delta Corvi. Clockwise from there, the other stars are Gamma, Epsilon, and Beta Corvi.

To the eye alone, the most impressive member of the quartet is Gamma Corvi. And in this case, appearances aren’t deceiving. It’s the brightest, hottest, and most massive of the four.

The star is also known as Gienah, from an Arabic phrase that means “the wing of the crow.” It’s actually a system of two stars. One of them is small and unimpressive. But the other is quite impressive. It’s more than four times the mass of the Sun, about 330 times brighter, and thousands of degrees hotter.

And even though it’s only a few percent of the Sun’s age, Gamma Corvi’s bright star is nearing the end of its life. Because of its mass, it’s used up the original hydrogen in its core, which fueled its nuclear reactions. Now it’s going through some changes. Among other things, its outer layers have swollen to giant proportions. That makes the star easy to see, even though it’s more than 150 light-years away — the bright wing of the crow.

Script by Damond Benningfield

As the Sun rose on May 18th of 1980, Mount St. Helens was the fifth-tallest mountain in Washington State — almost 10,000 feet tall. By sunset, it didn’t even rank in the top 50. The volcano had staged a massive eruption. It chopped 1300 feet off its height — and blasted away one whole side of the mountain.

It was one of the most powerful and destructive eruptions in American history. It killed almost 60 people, and flattened dozens of square miles of forest. It melted tons of ice and snow and sent the water roaring down rivers. And it expelled a cloud of ash that turned day to night across much of Washington.

Mount St. Helens is a stratovolcano. Such peaks are the most dangerous volcanoes because they can erupt quickly and violently. They have much steeper sides than the shield volcanoes found in Hawaii.

Volcanoes have been seen on several other worlds of the solar system. Most of them are shield volcanoes. There’s evidence of a few stratovolcanoes on Mars, but it’s hard to tell for sure — it’s likely that none of them has erupted in millions of years or longer.

Mount St. Helens erupted a few more times in 1980, although none with the force of the initial blast. And it’s been active several more times since then — most recently in 2008. Today, it’s rated as a “very high threat” to eventually erupt again — perhaps knocking it even farther down the list of Washington’s tallest mountains.

Script by Damond Benningfield

You can never judge a star by its appearance alone. The four stars at the center of Hercules, for example, all look pretty much alike. But each is different from all the others.

The stars form a sort of lopsided square called the Keystone. It’s in the east-northeast at nightfall.

Its brightest star, at the upper right, is called Zeta Herculis. Moving clockwise, the other three are Epsilon, Pi, and Eta Herculis.

Zeta is the closest of the four, just 35 light-years away. It actually consists of two stars. One of them is bigger, heavier, and brighter than the Sun, while the other is smaller, lighter, and fainter. The larger one is nearing the end of its life, so it’s undergoing some changes. They’ve caused it to puff up and shine even brighter.

Epsilon probably also is a binary. And it may even have three stars. Some studies indicate the presence of a third star, but others show only two. Like the Sun, the system’s main star is in the stellar equivalent of middle age.

Pi is the most impressive member of the Keystone. It’s about 375 light-years away — more than 10 times farther than Zeta. It’s so large that it would just about fill the orbit of Mercury, the closest planet to the Sun. And even though it’s just a small fraction of the Sun’s age, it won’t live much longer.

And finally, Eta is also more impressive than the Sun. And it, too, is nearing the end of its life — a stage the Sun won’t enter for billions of years.

Script by Damond Benningfield

Max Planck was in a bad way. The German physicist was the leader in the field of quantum theory – understanding the universe on the tiniest of scales. As World War II in Europe ground to its end, though, the 87-year-old scientist and his wife were hiding in a one-room farmhouse. Germany had surrendered, and desperate soldiers were scavenging through the countryside. At the same time, the Soviet army was approaching from the east, killing or mistreating its prisoners.

On the other side of the Elbe River from the farmhouse, an American soldier heard rumors that Planck was close by.

Gerard Kuiper was a researcher with the McDonald and Yerkes observatories. As part of his wartime duties, he’d taught celestial navigation and worked on radar. Posted to Europe, he was part of a team that assessed the progress of Germany’s atom-bomb effort.

75 years ago today, Kuiper commandeered a Jeep and a couple of troops and headed across the Elbe, where the American advance had stopped.

Kuiper found Planck and his wife at the farmhouse. They hopped in the Jeep and dodged Russian patrols – an excruciating journey for Planck, who suffered severe back pain.

They returned to the American lines safely. Planck was taken to a hospital, where he recovered enough to resume his research. Kuiper returned to the U.S., and spent 10 years as director of McDonald and Yerkes – after his rescue of one of the giants of 20th-century science.

Script by Damond Benningfield

Father Maximilian Hell had received an offer he couldn’t refuse. King Christian VII of Denmark and Norway had invited him to lead an expedition to observe a transit of Venus across the Sun in 1769. Hell had already declined a couple of other offers. But this one was too good to pass up. So he began preparing for one of his top accomplishments – and biggest controversies.

Hell was born 300 years ago today, in modern-day Hungary. His father was chief engineer for the local mines, so science and math were a constant part of his upbringing. After he joined the Jesuit order, the queen of Austria and Hungary appointed him astronomer royal. He built a new observatory, in Vienna, and directed it for most of the rest of his life.

His transit expedition took him to a small island off the coast of Norway. He took three telescopes, two clocks, and a raft of other instruments. The goal was to measure the timing of Venus’s passage across the Sun. By combining observations from different locations on Earth, astronomers hoped to calculate the exact distance to the Sun.

Hell made good observations of the transit. But he didn’t report them to other scientists for many months. That raised suspicions that he’d changed them to match those of others.

The controversy continued until the late 1800s, when a top astronomer found that Hell’s reports were genuine – confirming Father Hell’s status as one of the leading astronomers of the 18th century.

Script by Damond Benningfield

Most of the stars in the Milky Way Galaxy move at speeds that depend on how far they are from the galaxy’s heart. But some stars strike out on their own. They can zip along many times faster than the others — and in all different directions.

Most of these stars move at up a few hundred thousand miles per hour relative to the stars around them. The fastest tops out at about four million miles per hour. Some of these stars are moving fast enough to leave the Milky Way behind — and streak into the space between galaxies.

Astronomers have identified at least three ways to give a star such a strong kick.

One is an encounter with the supermassive black hole at the center of the Milky Way. It’s four million times the mass of the Sun, with a powerful gravitational pull. As a binary star system approaches it, the black hole may grab one of the stars and give the other a boost away from it.

A second way is a bit of gravitational acrobatics among three or more stars. That can juggle the orbits of some of the stars, but shove one of them away from the others.

And the third way involves a stellar explosion. When a massive star explodes as a supernova, it loses most of its mass. That means its gravity isn’t as strong. So a companion star could zip off in a straight line — away from the explosion. And the shockwave from the explosion could add to the kick — perhaps punting the companion out of the galaxy.

Script by Damond Benningfield

Walking across the largest moon of Mars might be quite a jolt. Mars would spread out just 3800 miles away. A strong jump could push you out into space. And the moon’s nightside might create electric shocks — not enough to hurt a person, but enough to damage equipment.

Phobos looks like a potato with a bite nipped off one end. On average, it’s about 14 miles in diameter — the size of a small city.

Escape velocity from the little moon is just 25 miles per hour — less than the top speed of sprinter Usain Bolt. That low gravitational pull could someday make Phobos a good spot for a base — it would take little fuel to land and take off.

But a trek across Phobos could create an electric charge. A study a couple of years ago found that a strong charge may build up on the little moon’s nightside — a result of the solar wind.

The wind contains particles with both positive and negative electric charges. But more negative particles may hit the nightside than the dayside. So anyone who walks across the nightside might build up a static charge — like walking across a carpet in your socks. Touching any metal could then cause a discharge — perhaps strong enough to damage scientific instruments or other equipment — a bit of a “jolt” on this odd little moon.

Mars is near our own Moon the next couple of mornings. The planet looks like a fairly bright orange star. It’s to the left of the Moon at first light tomorrow, and a bit closer above the Moon on Friday.

Script by Damond Benningfield

Big planets do things in a big way. Consider Saturn, the second-largest planet in the solar system.

A couple of years ago, astronomers tracked four storms in its northern hemisphere. They weren’t like other storms on the planet. They were bigger than the average storm, but smaller than the giants that break out every few decades — they were right in the middle. This being a giant planet, though, “mid-sized” is a whole different concept: The storms ranged from 2500 to 5,000 miles long, and lasted for up to seven months.

Saturn’s outer atmosphere is hundreds of miles thick. It’s stretched into planet-circling bands by Saturn’s high-speed rotation. The bands are colored in shades of yellow, white, and tan.

Occasionally, a storm breaks out — an explosion of water clouds driven by heat from inside Saturn. Most of the storms are hundreds of miles across. Every once in a while, though, a monster breaks out. It can stretch most of the way around the planet — tens of thousands of miles.

A recent study says the new storms could have been trying to build to giant proportions. But a monster storm a decade ago could have robbed their part of the atmosphere of energy — leaving them at mid-sized proportions.

Saturn stands to the upper right of the Moon at first light tomorrow, and looks like a bright star. The even brighter planet Jupiter is to the right of Saturn. And Mars is well to the left of the Moon. More about that tomorrow.

Script by Damond Benningfield

Ancient skywatchers gave the planets personalities. Jupiter, for example, represented the king of the gods of Olympus, with all the qualities that suggests — strength and courage, among others. If the modern world associated the planets with heroic beings, it might still be Olympians — but of the athletic kind. Mercury might be a sprinter, and Saturn a marathoner. And Jupiter would be king of the shot-put.

Jupiter is the giant of the solar system — it’s more massive than all the other planets put together. That gives it a powerful gravitational field, which has a big influence on the space around it.

When the solar system was young, it was filled with billions of small chunks of rock and ice known as planetesimals — the building blocks of the planets. Jupiter’s gravity ejected many of them from the solar system, into deep space. Jupiter also pushed around planetesimals in a broad band between Jupiter and Mars, preventing them from forming a planet. Today, that band is the asteroid belt.

Jupiter continues to push around smaller bodies even now. Encounters with comets or asteroids can shove them into different orbits. It can even kick them out of the solar system entirely — long-distance shot-puts for a true Olympian.

Jupiter rises quite close to the Moon in the wee hours of the morning, and is above the Moon at first light. It looks like a brilliant star. The planet Saturn is nearby, and we’ll have more about that tomorrow.

Script by Damond Benningfield