StarDate PodcastAuthor: McDonald Observatory
08 Mar 2021

StarDate Podcast

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StarDate, the longest-running national radio science feature in the U.S., tells listeners what to look for in the night sky.

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    Denebola

    For the constellation Leo, its bright heart — the star Regulus — gets the lion’s share of attention. But the lion’s tail is no slouch, either. The star is bigger and brighter than the Sun. And it’s a lot younger — although there’s disagreement on just how young.

    Denebola is low in the east as night falls now, far to the lower left of Regulus. It’s bright enough to see from all but the most light-polluted cities. Its name comes from a longer Arabic name — Dhanab Al-Asad — “the tail of the lion.”

    The star is pretty impressive. It’s about three-quarters again the size and mass of the Sun. It’s about 15 times brighter than the Sun. And its surface is thousands of degrees hotter than the Sun’s, so the star shines pure white.

    Denebola is encircled by bands of dust. The way the bands are distributed may indicate that planets orbit between them. So far, though, no planets have been seen.

    Estimates of Denebola’s age vary by hundreds of millions of years. Most estimates, however, say it’s especially young. A few studies put its age at a hundred million years. A couple of others say Denebola is even younger — just 45 million years. That would make it just one percent the age of the Sun — a bright youngster at the tail of the lion.

    Again, look for Denebola low in the east as darkness falls and climbing high across the sky during the night. It’ll rise a little earlier each evening as we head into spring.


    Script by Damond Benningfield

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  • Posted on 07 Mar 2021

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    Mystery Explosion

    When it comes to understanding an exploding star, one number trumps all: distance. If astronomers don’t know the distance to a dying star, they can’t be sure how the star is going out.

    That may be the case with CK Vulpecula. Normally, it’s too faint to see with the eye alone. But centuries ago, it flared up. It first grew bright enough to see in 1670. Then it grew brighter still in March of 1671 — 350 years ago this month.

    The leading idea has been that the flare-up was produced by the collision and merger of two stars. Different models have come up with different types of stars, but the basic idea has stayed the same.

    A recent study, though, found that CK Vulpecula may be five times farther than shown by earlier measurements — about 10,000 light-years. If so, then the outburst was about twenty-five times brighter than thought.

    A collision between two stars wouldn’t be powerful enough to make the star shine that brightly. Yet the outburst wouldn’t have been bright enough to be the result of a supernova — a titanic explosion that rips a star to bits. So CK Vulpecula may be an in-betweener — a type of explosion that can’t yet be explained.

    CK Vulpecula is far too faint to see without a telescope. Yet its location is easy to pick out. It’s in Vulpecula, the fox. It stands near the middle of the bright Summer Triangle, which is high in the eastern sky at first light on March mornings.


    Script by Damond Benningfield

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  • Posted on 06 Mar 2021

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    Magnetic Bursts

    One of the big astronomical mysteries of the last decade or so has been the origin of fast radio bursts. In recent months, though, astronomers have found that at least some of them may be powered by magnetars — the super-magnetized remnants of exploded stars.

    A fast radio burst lasts about a thousandth of a second. In that instant, though, it emits more energy than the Sun produces in several days. But most bursts are in other galaxies, so they’re hard to study.

    Last April, though, a burst was recorded inside our home galaxy, the Milky Way. It came from a known magnetar.

    A magnetar is the ultra-dense corpse of a star that exploded as a supernova. It’s heavier than the Sun, but only a few miles across. And it has a magnetic field that can be a trillion times as powerful as Earth’s.

    Starting on April 27th, X-ray telescopes in space saw the magnetar produce a series of outbursts. After a few hours, it produced an especially powerful burst — a fast radio burst.

    Astronomers aren’t sure just how a magnetar produces such an event. One study says it may begin with a “quake” — a crack in the magnetar’s crust. That shoots out a magnetic bubble that disrupts the surrounding magnetic field. The field reconnects behind the bubble, triggering a short but powerful burst of energy.

    There could be more than one way to make fast radio bursts. But last April’s event suggests that at least some of them could come from super-magnetic stars.


    Script by Damond Benningfield

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  • Posted on 05 Mar 2021

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    Magnetic Merger

    The merger of two neutron stars produces quite the fireworks. It creates most of the gold, silver, uranium, and certain other heavy elements in the universe. It causes space and time to “jiggle.” And it usually results in the birth of a black hole. But a merger seen last spring may have created something just as exotic: a magnetar.

    A neutron star is the corpse of an exploded star. It’s more massive than the Sun, but only the size of a small city. A magnetar is a neutron star with an ultra-powerful magnetic field — a trillion or more times the strength of Earth’s magnetic field.

    On May 22nd, space telescopes detected a brilliant outburst from a galaxy at the southwestern corner of Pisces, which is disappearing in the evening twilight now. The galaxy is more than five billion light-years away. The burst lasted just half a second. Yet it carried more energy than the Sun will produce in its entire 10-billion-year lifetime.

    From the details of the outburst, astronomers concluded that it was produced by the merger of two neutron stars. Yet the afterglow was too bright to come from a black hole. That suggests the merger created a magnetar.

    Astronomers aren’t certain that that’s what happened. But if it is, the magnetar should produce a lot of radio waves in anywhere from a few months to a few years. So they’ll aim their radio telescopes its way to try to confirm the birth of a magnetar.

    More about magnetars tomorrow.

     
    Script by Damond Benningfield

    Support McDonald Observatory


  • Posted on 04 Mar 2021

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    All Full

    With a waiting list of more than 90,000 customers, Pan American World Airways might have needed a name change — to Pan American Out-of-this-World Airways. That’s because the waiting list was for flights to the Moon.

    The list began in 1964, when a man in Austria called a travel agency and asked to book a trip. The agency referred him to Pan Am, one of the world’s leading airlines. Pan Am politely put him on a waiting list.

    When word about the list got out, a few hundred others added their names to it over the next few years. But the list took off in late 1968, when Apollo 8 put the first astronauts in lunar orbit. And it got even bigger a few months later, when Neil Armstrong and Buzz Aldrin became the first to land on the Moon.

    Pan Am never took money or issued reservations. Instead, those on the list became members of the First Moon Flights Club, and received a numbered membership card. The club was so popular that Stanley Kubrick featured Pan Am space shuttles in the movie 2001: A Space Odyssey. And Pan Am even promoted the club in its advertising.

    The list grew so long that the airline closed it 50 years ago today. But it told those already on the list that it was still planning to send them to the Moon as soon as possible.

    It was not to be, though. Pan Am went bankrupt in 1991. Members of the First Moon Flights Club were left with their membership cards — and thoughts of what might have been.


    Script by Damond Benningfield

    Support McDonald Observatory


  • Posted on 03 Mar 2021

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