StarDate

A brilliant star in the southern constellation Carina may be about to meet its doom. In fact, it may have done so already, but it’s so far away that its light hasn’t had time to reach us. But when it does, it’ll be quite a show.

The star is known as SBW1. It was discovered about a decade ago. It’s a blue supergiant. It’s probably about 20 times as massive as the Sun, many times wider, and tens of thousands of times brighter. Such a star is fated to explode as a supernova. That blasts its outer layers into space, and briefly makes the star shine as brightly as billions of normal stars.

One indication that such a blast is imminent is a ring of gas and dust around the star. It’s built like a string of beads, with not much between the beads. The material was ejected from the star’s equator, then formed the bead structure as it expanded and cooled.

A similar ring encircled the brightest supernova seen from Earth in the last few centuries — Supernova 1987A, in a companion galaxy to the Milky Way. The star itself was a near twin to SBW1.

Astronomers didn’t see the ring around 1987A until after the star blew itself to bits. But studies suggest that it was expelled about 10,000 years before the star exploded. And that suggests that SBW1 could be about to explode as well. In fact, since the star is more than 20,000 light-years from Earth, it could have exploded already, and the light from the blast is racing toward us even now.

Script by Damond Benningfield

When Matthew Vassar was setting up a new women’s college at the end of the Civil War, the first professor he wanted to hire was astronomer Maria Mitchell. She’d discovered a comet in 1847, bringing her international fame.

But Mitchell had some conditions: She wanted an observatory, complete with a good telescope and apartments for herself and her father. She got them. So Mitchell became the country’s first female astronomy professor.

Mitchell was born 200 years ago today, in Nantucket. Her father was an amateur astronomer, and he taught Maria how to use the telescope. Her comet discovery led to membership in several science organizations — the first woman to belong to any of them.

At Vassar, Mitchell established a busy astronomy program. Beginning in 1873, she and her students took daily photographs of the Sun — one of the earliest photographic records of sunspots. They also journeyed to solar eclipses.

Yet Mitchell’s most important contributions were social. She advocated women’s rights, and was a founder of the American Association for the Advancement of Women. She fought for equal pay — which she got — and encouraged her students to work part-time to help them be independent.

Mitchell died in 1889. But several of her students — and their students — made important contributions to astronomy. And although it no longer watches the stars, the observatory building she wanted still stands — the Maria Mitchell Observatory.

Script by Damond Benningfield

On a clear autumn night in 1847, Maria Mitchell excused herself from a party at her father’s house. The 29-year-old librarian then climbed onto the roof and scanned the skies with a telescope. Her observations revealed a small, fuzzy object she hadn’t seen before: a comet.

At the time, discovering a comet was a big deal. So Mitchell’s find brought many accolades, including a gold medal from the king of Denmark. The discovery also made her a celebrity, and kicked off a career in which she became the first American woman to serve as a professional astronomer.

Mitchell was born 200 years ago tomorrow, in the whaling village of Nantucket. Her parents were Quakers, who believed that both boys and girls should get an education. So Maria attended school during the day, and at night, her father taught her astronomy.

After she discovered “Miss Mitchell’s Comet,” the Navy’s Nautical Almanac Office hired her to help with astronomical calculations. And she became the first female member of the American Academy of Arts and Sciences. In the 1850s, she became the first woman ever to enter the Vatican Observatory -- although it took a couple of weeks of cajoling to get her inside.

At the end of the Civil War, Matthew Vassar was planning a new women’s college in Poughkeepsie, New York. And the first faculty member he hired was Maria Mitchell, making her the first female astronomy professor in the country. We’ll have more about that tomorrow.

Script by Damond Benningfield

In mythology, Icarus and his father tried to fly away from the island of Crete with wings made of wax and feathers. The father warned Icarus not to fly too close to the Sun. But Icarus ignored the advice and soared high into the sky. The Sun’s heat then melted his wings, so he plunged into the sea and drowned.

NASA is about to launch a mission that will venture far closer to the Sun than any other spacecraft to date. Unlike Icarus, though, it’s carrying protection: a shield that will keep its instruments as cool as a spring day.

The launch window for Parker Solar Probe opens tomorrow. The craft will orbit the Sun 24 times, eventually dropping to within four million miles of the surface. Temperatures on the leading edge of its heat shield will reach 2500 degrees Fahrenheit. But behind the shield, everything will be nice and cool.

The probe is named for Eugene Parker -- the first NASA spacecraft named for a living person. In the 1950s, Parker proposed that a complex interplay of hot gas and magnetic fields on the Sun produces a “wind” of charged particles. Spacecraft discovered the solar wind in the ’60s.

Parker Solar Probe will study how and where that wind is generated, and how it’s accelerated to millions of miles per hour. It’ll also study the Sun’s outer atmosphere, the corona, which is much hotter than the surface of the Sun. The observations should help scientists better understand our star -- without risking life and limb.

Script by Damond Benningfield

Vindemiatrix, the third-brightest star of Virgo, is in the southwest at nightfall. It’s far to the upper right of Spica, Virgo’s brightest star.

Vindemiatrix is a giant -- a bloated star that’s completed the “normal” portion of its life. It’s more than 10 times the diameter of the Sun. It’s almost three times heavier than the Sun, and almost 80 times brighter.

Astronomers know these details because they know the star’s distance -- more than 100 light-years. Without the distance, we can’t know a star’s true brightness, which is one of the keys to learning its full story.

Measuring a star’s distance isn’t easy, though. For most stars, astronomers use a technique called parallax. They measure the star’s position when Earth is on opposite sides of the Sun. That’s like holding a finger out at arm’s length and looking at it with one eye, then the other -- the finger appears to move a bit compared to the background. And the same thing happens with a star -- it appears to shift back and forth a bit compared to the stars around it.

The angles are tiny, so they’re tough to measure. That’s especially true from the ground, because the atmosphere makes a star look like a fuzzy blob.

The best measurements come from spacecraft. Gaia, a European craft, has measured the parallaxes of more than a billion stars. Its work shows that Vindemiatrix is 106 and two-thirds light-years away -- what should be the best measurement ever of the distance to this bloated star.

Script by Damond Benningfield

For most birds, the beautiful feathers get most of the attention. And that’s pretty much the case for Cygnus, the celestial swan. To the eye alone, its most impressive sight is Deneb, the bright star that represents its tail feathers.

If you look more closely, though, the swan’s fainter beak is far more colorful. Through a telescope, that single pinpoint becomes double. One of the stars is golden orange, the other is blue-white. That contrast makes Albireo a favorite target for many double-star watchers.

The golden star is actually two or more stars on its own. They’re so close together that they can’t be separated even through a telescope. The main star -- the star we see -- is an orange giant. It has at least one companion, and perhaps two.

The other visible member of Albireo is thousands of degrees hotter than the Sun, hence the blue-white color.

It’s not clear whether the two visible components are a true binary or just happen to line up in the same direction. Astronomers determine if two stars form a binary by measuring their relative motions across the sky. If the stars are bound, then their paths curve around each other. But the stars of Albireo are so far apart that there hasn’t been enough time to determine whether that’s happening.

Albireo is in good view on summer nights. Cygnus is high in the east at nightfall, with its body parallel to the horizon. Brilliant Deneb is at the left end of the body, with Albireo at the right.

Script by Damond Benningfield

Mars and the full Moon stick close together tonight. Mars looks like a brilliant orange star, outshining all but the Moon and the planet Venus. In fact, it’s at its brightest for the next few years. It’s close to the lower right of the Moon at nightfall.

Mars is abristle with visitors from Earth right now -- six working orbiters and two rovers. And more missions are scheduled to head that way in the next few years. That includes a mission from a country that has yet to launch a single spacecraft: the United Arab Emirates.

The mission is known as Al-Amal -- Arabic for “Hope.” The orbiter is scheduled to launch in July 2020 and arrive at Mars the following year. It will study the Martian atmosphere and climate. And it’ll give the country experience to pursue even grander plans -- building colonies on Mars in the 22nd century.

Toward that end, the UAE has announced plans to build a simulated Mars colony in the desert, near Dubai. Known as Mars Science City, it’ll consist of several domes, all with self-sustaining ecologies. One of its labs will be dedicated to agriculture -- learning how to grow crops on the Red Planet. Among other things, it’ll grow lettuce, strawberries, and a staple of the desert, date palms.

Growing crops on Mars won’t be easy. The Martian dirt contains compounds that are toxic to plants. But experiments like the one planned by the UAE could help pave the way for colonists to survive on our planetary neighbor.

Script by Damond Benningfield

The Moon will pass through Earth’s shadow tomorrow, creating a beautiful eclipse. In fact, the Moon will remain fully immersed in the shadow for an hour and 43 minutes -- longer than any other lunar eclipse of this century. The Moon will turn dark red or orange -- color from sunlight filtering through Earth’s atmosphere. At least part of the eclipse will be visible from almost the entire planet. The only exception is North America.

Our consolation is that the Moon will be close to the planet Mars, which is shining brighter than it will for several years. It looks like a brilliant orange star, to the lower left of the Moon at nightfall.

A lunar eclipse occurs when the Moon passes through Earth’s long shadow. But not all eclipses are the same. The length of an eclipse varies depending on the Moon’s position within the shadow, and the Moon’s distance from Earth. For tomorrow’s eclipse, the Moon will pass through the heart of the shadow. And it will be near its farthest point from Earth, so it will move slowly, extending its time in the shadow.

The total eclipse begins at 2:30 p.m. Central Time, when the Moon completely enters Earth’s dark inner shadow. It ends when the Moon begins to exit the shadow, 103 minutes later. Although it won’t be visible from the United States, it’ll play out on several web sites, so we can at least get a second-hand view of this beautiful astronomical alignment.

More about the Moon and Mars tomorrow.

Script by Damond Benningfield

Back in April, a German greenhouse produced its first crops: eight pounds of salad greens, 18 cucumbers, and 70 radishes. What makes that remarkable is that the greenhouse is in Antarctica. And it’s designed in part to help scientists learn how to grow produce on the planet Mars.

Martian colonists will need to live off the land -- it’s just too expensive to ship everything from Earth. They’ll probably use underground deposits of ice for drinking water, oxygen, and rocket fuel. And they’ll need to grow crops using the Martian soil.

That won’t be easy, though. The powdery Martian dirt contains compounds that are toxic to many plants. So colonists will have to process the dirt, or dig deep to find deposits that are friendlier to life.

As in the movie “The Martian,” one crop they’re likely to grow is potatoes. Here on Earth, they’re grown in all kinds of environments, from tropical to arctic, and at elevations from sea level to more than two miles high. Potatoes are highly productive, too -- you can grow a lot of them with little water and land. And they’re highly nutritious.

Scientists in Peru recently grew potatoes in soil from the Pampas de la Joya Desert, which resembles Martian dirt. But only about 40 percent of the varieties they planted survived, and those that did make it were scrawny.

For now, look for Mars low in the southeast as night falls. It looks like a brilliant orange star, outshining all but the Moon and the planet Venus.

Script by Damond Benningfield

The solar system offers up some amazing treats tonight. First, there’s a conjunction between the Moon and the planet Saturn. And second, the planet Mars is just about at its closest to Earth for the entire year, so it looks like a brilliant orange star.

Saturn is the bright object just below the Moon as night falls. It’s the second-largest planet in the solar system, which is one reason it shines so brightly. Another is that its broad, bright rings are tilted into good view, so they reflect a lot of sunlight. But it’s about 800 million miles away -- a distance that dulls its luster a bit.

Mars, on the other hand, is less than 36 million miles away -- just about as close as it ever gets. So it shines much brighter than Saturn, even though it’s only about one-twentieth the diameter of Saturn.

Mars is not only closer to Earth, but it’s also closer to the Sun than Saturn is. As a result, sunlight at Mars is about 40 times more intense than it is at Saturn. That’s a lot more light for Mars to reflect back in our direction.

Mars looks orange because much of its surface is coated by a powdery orange dust. That dust contains a lot of iron oxide -- the compound that makes up the rust on your iron pipes. The fine dust grains blow across much of the planet, covering vast plains and filling basins and craters. And sometimes, it forms giant storms that can cover the entire planet.

We’ll have more about Mars tomorrow.

Script by Damond Benningfield