StarDate

Few observatory directors have had as colorful a life as Otto Struve. By the time he was 24 years old, he’d survived having his horse shot from under him, had almost been hit by lightning, and almost starved as a war refugee.

Struve was born 125 years ago, in Ukraine — the fourth generation of an astronomical dynasty. He first accompanied his father to an observatory at age eight, and by 10 he was helping take observations.

In 1916, Struve joined the Russian army. He was sent to the Turkish front. His horse was shot from under him, and another bullet zipped through his coat sleeve.

Struve returned to his studies after the war. During the Russian revolution, though, he joined the White Army and fought against the communists. Afterward, he made his way to Turkey as a refugee. He spent a long, cold winter there, barely finding enough to eat.

In the spring, he went to Constantinople, where he got by with odd jobs. He was a lumberjack for a while, and was almost struck by lightning. By chance, Struve received a letter from the director of the University of Chicago’s Yerkes Observatory offering him a job. It took some doing, but Struve made his way to the U.S. in 1921.

Over the following decade, Struve worked his way up, becoming director of Yerkes in 1932. That same year, he also became the founding director of the brand-new McDonald Observatory in Texas — a new chapter in the colorful life of Otto Struve.
 

Script by Damond Benningfield

Support McDonald Observatory

Otto Struve knew an opportunity when he saw one.

The University of Chicago astronomer knew that his institution needed a big new telescope to supplement the 40-inch refractor at Chicago’s Yerkes Observatory in Wisconsin. Yet Chicago didn’t have the money to pay for one.

When William J. McDonald left his fortune to the University of Texas to build an observatory, Struve suggested a partnership: Texas would provide the observatory, and Chicago would provide the astronomers. Texas agreed, and the two universities signed a 30-year deal. Struve, recently promoted to the directorship of Yerkes, would also direct the new McDonald Observatory.

Struve was born 125 years ago today, in Ukraine. He was a fourth-generation astronomer. He served in the Russian army, then was offered a job with the University of Chicago. Struve arrived in 1921, earned a Ph.D., and worked his way up through the astronomy program.

Struve oversaw design and construction of McDonald Observatory’s 82-inch telescope — the second-largest telescope in the world. It was dedicated in 1939. Struve spent long hours using the telescope to study the stars, while building up the Chicago astronomy faculty.

Conflicts with his young scientists eventually led to Struve’s resignation. Yet his name continues to resound in West Texas: McDonald Observatory named the 82-inch telescope in his honor.
 

Script by Damond Benningfield

Support McDonald Observatory

This is a bad time for a full Moon that’s especially big and bright. That’s because a meteor shower will reach its peak over the next couple of nights. But a full Moon overpowers all but the brightest meteors. And a Moon that’s especially close — making it especially bright — is an even bigger hindrance. It reduces the number of meteors you might see to just a handful — even if you’re far away from city lights.

The Perseid shower is one of the more reliable meteor showers. At its peak, it usually produces a dozen or two “shooting stars” per hour, and sometimes a lot more. This year, though, the showing should be much weaker — the result of the pesky full Moon.

The Moon will reach its “full” phase this evening — about 30 hours after it passed closest to Earth for the month — 223,587 miles away. That’s the Moon’s third-closest approach of the year — about 15,000 miles closer than average. At that range, the Moon shines several percent brighter than average.

Some describe such a close Moon as a super-Moon, but others don’t. That’s because there’s no formal definition for a super-Moon. For some, it’s the closest full Moon of the year. For others, it’s any full Moon within a certain distance — although different groups use different distances.

Super-Moon or not, this month’s full Moon will be close, big, and bright — and it’ll block out most of the Perseid meteor shower.
 

Script by Damond Benningfield

Support McDonald Observatory

The Perseid meteor shower is building toward its peak. Tonight, you might see a few of its streaks of light, although the Moon will drown out all but the brightest of them.

But even the ones you do see through the moonlight can’t compare to a meteor that blazed across the sky 50 years ago. It was visible during broad daylight.

The fireball was first seen over Utah, during the afternoon of May 10th, 1972. Thousands watched it race across the sky. It vanished from sight over Alberta, Canada. Two people made home movies of it. And a spy satellite designed to look for nuclear test firings on Earth followed it for about two minutes.

The fireball was a small asteroid — a ball of rock and metal anywhere from 10 to 45 feet in diameter — that was being vaporized by friction with the atmosphere. It dropped to an altitude of just 35 miles. But it hit the atmosphere at a shallow angle, so it skipped back into space like a rock skipping across a pond.

If the asteroid had taken dead aim at Earth, it most likely would have exploded high in the sky. That might have caused some local damage — or no problems at all.

The passage vaporized most of the asteroid, cutting its diameter by at least half. It also slowed the asteroid, changing its orbit around the Sun. It may come close to Earth again in the future, but it’s not expected to “skip” off the atmosphere any time soon.

More about the Perseids tomorrow.
 

Script by Damond Benningfield

Support McDonald Observatory

Every 12 and a half months, Earth moves past the giant planet Saturn. And that’s about the best time all year to watch it. It rises around sunset, is in view all night, and shines brightest for the whole year.

That alignment is known as opposition, and it’s coming up on Saturday. But there’s not much difference in the view for days before and after opposition, so don’t wait for that moment to look for Saturn.

It takes Saturn about 29 years to orbit the Sun, compared to one year for Earth. So we “lap” Saturn every 12 and a half months. If we could watch the two planets from above at high speed, the process would look like a small car on the inside lane of a race track zipping past a big car over and over. For every lap by the big guy, the little guy would make 29.

Saturn is at its closest around opposition — one reason it’s so bright. But its brightness varies from one opposition to another. That’s largely because we see Saturn’s rings at different angles. When the rings are most tilted as seen from Earth, Saturn shines roughly twice as bright as when the rings are seen edge-on. This year, they’re about half way between — adding to the luster of this plodding giant.

Look for Saturn low in the east-southeast at nightfall, and arcing across the south later on. It looks like a bright golden star. It’s well to the lower left of the Moon tonight, but the Moon will catch up to it over the next two nights.
 

Script by Damond Benningfield

Support McDonald Observatory

An unsettled Sun may have a big impact on some of the biggest weather-makers on Earth: El Niño and La Niña. These alternating events in the Pacific Ocean can bring floods to some parts of the world and droughts to others, and alter global temperatures for months or years. And a recent study found a strong correlation between the cycles of El Niño and La Niña and the magnetic cycle of the Sun.

The solar cycle lasts about 11 years. At its peak, it produces many sunspots — dark magnetic storms on the surface of the Sun — as well as big outbursts of radiation and particles. And at the cycle’s low point, the Sun is quiet, with few if any magnetic storms.

Researchers looked at records of solar activity from 1900 to 2018. They compared that to records of El Niño and La Niña over the same period. And they found a match. When solar activity was high, the temperature of the North Pacific was high as well. That correlated to longer and stronger bouts of El Niño. And when the Sun was quiet, Pacific temperatures were lower and La Niña was more likely to appear.

The extra energy during the Sun’s high point may first warm a layer of Earth’s upper atmosphere. That warms the air below, changing a large circulation pattern. And that warms the North Pacific, which in turn warms the Central Pacific — the birthplace of many El Niño and La Niña events. So to get a general idea of what to expect here on Earth, we may want to look to the Sun.
 

Script by Damond Benningfield

Support McDonald Observatory

The brightest star in the night sky has played a key role in the calendars of many cultures. In ancient Egypt, for example, its first appearance in the dawn sky marked the beginning of a new year, and heralded the annual flooding of the Nile. And in Greece and Rome, that dawn showing ushered in the Dog Days — the most sweltering time of year. It’s a phrase we still use today.

When the phrase was coined, the star Sirius first climbed into view around the end of June — at the start of summer and a long run of hot, humid days. Sirius is the brightest star of the constellation Canis Major, the big dog. So it’s known as the Dog Star. People associated the star with the climate, so they called that time of year the Dog Days.

Thanks to an effect known as precession, though, the stars gradually shift position relative to the Sun. So now, Sirius doesn’t peek into view in the dawn sky until August. From the southern states of the U.S., it’s appearing right about now. It won’t emerge from the Sun’s glare from more northerly latitudes for another week or so. For those who can see it, it’s in the east-southeast, almost directly below the line of stars that marks Orion’s Belt.

That shift has changed the way we think of the Dog Days. In early times, the phrase referred to a specific time of year — generally from early July to about mid-August. Today, though, it refers simply to the hottest period of the year — the Dog Days of summer.
 

Script by Damond Benningfield

Support McDonald Observatory

The star Antares is orange. That means its surface is thousands of degrees cooler than the Sun’s. Deep inside, though, it’s a different story. The temperature in the core of Antares is at least 180 million degrees, compared to 27 million for the Sun.

Antares is hotter because it’s roughly a dozen times the mass of the Sun — and for a star, mass is everything. Gravity squeezes gas in the core tightly, making it hot enough to produce nuclear fusion. In the Sun, hydrogen atoms fuse together to make helium, releasing energy. As the energy radiates toward the surface, it pushes outward on the star’s surrounding layers of gas.

As a star’s mass increases, so does its gravity. It squeezes the core even tighter, making it even hotter. A hotter core “burns” the hydrogen more quickly, so it uses it up in a hurry. It then moves on to fusing the helium to make even heavier elements. Radiation from the hotter core causes the outer layers to puff up to amazing proportions. Antares, for example, is hundreds of times wider than the Sun. That makes its outer layers cooler and redder.

Antares should spend a total of about a million years in this phase of life before moving on to fuse other elements. When it can’t continue that process, the core will collapse and the outer layers will explode — sometime in the next million years.

Look for Antares close to the lower left of the Moon at nightfall, and a little closer as they set.
 

Script by Damond Benningfield

Support McDonald Observatory

Mars is tough on wheels. The metallic wheels on the Curiosity rover, for example, look like they have more holes and tears than tread. In fact, flight controllers recently had to abandon an area they wanted to explore because it was covered in sharp rocks described as “gator backs.”

That’s one of the few things that’s slowed the rover, which arrived at Mars 10 years ago tonight. In its decade of travels, it’s covered more than 17 miles, and climbed up and down several hills.

When it landed, Curiosity was the biggest and most sophisticated Mars rover yet. The nuclear-powered craft was as big as a minivan. It was bristling with cameras, and it carried a chemical laboratory for analyzing the rocks and dirt. It also had a laser to “zap” the rocks, allowing its instruments to study the vaporized debris.

Curiosity landed in Gale Crater — an ancient impact crater with a tall mountain at its middle. Curiosity’s main mission was to find out whether the site had once had comfortable conditions for life.

And it quickly found that it probably did. Water once filled the crater. Despite years of trying, though, it hasn’t found any evidence of life itself — at least not in the rocks. It has detected methane gas wafting through the crater. On Earth, methane most commonly is produced by life. But there’s no confirmation that anything is living in Gale Crater — or ever has.
 

Script by Damond Benningfield

Support McDonald Observatory

A spectacular storm on the Sun erupted 50 years ago this week — one of the most powerful ever seen. It produced several giant outbursts, and shot a cloud of charged particles toward Earth. When the cloud got here, it created all kinds of problems. Among other things, it apparently triggered sea mines in a harbor in Vietnam.

The storm began on August 2nd, 1972. The big cloud followed later, and it reached Earth in record time — less than 15 hours. That means it was traveling at more than six million miles per hour.

When the cloud reached Earth, on August 4th, it created auroras that were bright enough to read by. It caused problems with power grids and communications networks in the United States. And it shorted out a Defense Department satellite.

According to the Navy, it also set off magnetic mines in Hai Phong harbor in Vietnam. Naval aircraft recorded a couple of dozen explosions in just two minutes.

The mines were set to explode when they “felt” sharp changes in the magnetic field. The solar storm produced several of those spikes — strong enough, the Navy concluded, to trigger the explosions.

The Navy quickly changed the design of its mines to prevent a repeat. But big solar storms continue to cause big problems. And because we depend on so much more technology today, a storm like the one in 1972 could cause massive damage. But it probably wouldn’t set off any more mines.
 

Script by Damond Benningfield

Support McDonald Observatory