StarDate PodcastAuthor: McDonald Observatory
14 Jun 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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    Moon and Companions

    A couple of prominent companions huddle near the crescent Moon this evening. The planet Mars is close below the Moon. And the Beehive star cluster is about the same distance to the left of the Moon. The view is best after the sky gets nice and dark; binoculars will enhance the view.

    Through binoculars, you’ll be able to pick out all the notable features on the entire lunar disk — including the dark part, where it’s night. That’s because a gibbous Earth hangs in the lunar sky right now. It’s many times brighter than a full Moon, so it washes the Moon in reflected sunlight. So even to the eye alone, the dark portion of the Moon is easily visible — it has a pale ghostly appearance.

    Binoculars don’t do much to enhance Mars. It looks like a moderately bright star either with or without them. Binoculars ought to show off its color a bit better, though.

    But they will make a difference with the Beehive. Without the binoculars, it looks like a hazy patch of light, with perhaps a few individual stars visible to those with sharp eyes. But through binoculars it more closely resembles its name — it looks like a bunch of stellar bees buzzing through the night.

    And as a bonus, there’s one bright object that’s visible in the fading twilight: Venus, the brilliant “evening star.” It’s well to the lower right of the Moon, and drops from sight by about the time the sky gets fully dark.

    Tomorrow: a nuke for NASA.
     

    Script by Damond Benningfield

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  • Posted on 13 Jun 2021

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    Jhelum Stream

    Most of the stars of the Milky Way were born here. But quite a few were born in other galaxies that were gobbled up by the Milky Way. Some of the remnants of those galaxies form long ribbons of stars, which makes them easier to find.

    One of the most recent discoveries is known as the Jhelum Stream. It was discovered in 2018, by an observatory in Chile, and is named for a river in India. The stream runs across the constellation Grus, the crane, which is so far south that it’s not visible from most of the United States.

    Jhelum is centered about 40,000 light-years from Earth. It’s in the Milky Way’s halo, which is far outside the galaxy’s disk. It’s hundreds of light-years long. And it appears to split into two ribbons. One is short and skinny, while the other is longer and wider. They move through space together, though, suggesting they have a common origin.

    Astronomers are still trying to figure out just what that origin is. Most money says that both ribbons are remnants of a single small galaxy. It was a few million times the mass of the Sun. Although that sounds pretty heavy, it’s tiny compared to the mass of the Milky Way.

    As the little galaxy approached the Milky Way, billions of years ago, it was captured by our galaxy’s powerful gravity. As it orbited the center of the galaxy, it was pulled apart. And today, its remaining stars form ribbons around the Milky Way — the remnants of a small but independent galaxy.

    Script by Damond Benningfield

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  • Posted on 12 Jun 2021

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    Odd Ophiuchus

    Half of the constellations of the zodiac line up across the south as night falls this evening like charms on a bracelet. The lineup begins with Gemini, which is quite low in the west-northwest. Both the crescent Moon and Venus, the “evening star,” are within its borders. Cancer is to the upper left of the twins. Then the lineup arcs across the south to include Leo, Virgo, Libra, and finally Scorpius, low in the southeast.

    In ancient times, skywatchers assigned special meaning to these constellations because they’re on the ecliptic — the Sun’s path across the sky — so the Sun moves across them each year.

    Another constellation also lies along this path, but it’s not a member of the zodiac. Ophiuchus is to the upper left of Scorpius at nightfall. Its brightest members form the faint, wide-spread outline of an old coffee urn.

    Ophiuchus isn’t an official member of the zodiac because the Sun doesn’t cross the urn itself. Instead, it just nips the southern edge of the modern version of the constellation, which includes a wide area around the classical outline.

    All of the modern constellations have well-defined borders. That turns the sky into a giant quilt with 88 patches. They’re of many different sizes and shapes. Some are simple rectangles, but most have odd outlines to hold the classical star pictures. In fact, the border of Ophiuchus consists of 38 segments — an oddly shaped patch that just intersects the ecliptic.

    Script by Damond Benningfield

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  • Posted on 12 Jun 2021

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    Moon and Venus

    Planetary scientists caused a bit of a stir last year when they reported finding phosphine in the atmosphere of Venus. Here on Earth, the compound is produced only by living organisms or in the lab. So the finding suggested that microbes could be living in Venus’s clouds.

    Later reports have cast doubt on the finding. But no one is giving up on the possibility that microbes might inhabit the clouds.

    The surface of Venus isn’t a nice place. It’s hot enough to melt lead, and the pressure is like being at a depth of two-thirds of a mile in Earth’s oceans.

    And at first glance, the clouds don’t sound much better — they’re made of sulfuric acid. Yet there’s a layer in the clouds where the temperature and pressure could be comfortable for life. And orbiting spacecraft have detected a possible hint of life within that layer.

    One recent study said that microbes could be protected inside droplets of sulfuric acid mixed with water. When the droplets get heavy enough, they’d drop to lower altitudes and evaporate. The microbes would dry out and shut down. Eventually, though, they’d be mixed back up into the clouds, where they’d be encased in new droplets — restoring them to life.

    It’ll take new missions to the planet to settle the question of whether anything is living in Venus’s clouds.

    And Venus is in the early evening sky right now. Its clouds make it shine brilliantly as the “evening star.” Tonight, it’s next to the crescent Moon.

    Script by Damond Benningfield

    Support McDonald Observatory


  • Posted on 11 Jun 2021

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    Sharper View

    Few sights are more relaxing than a field of stars twinkling through a dark night sky — at least for most of us. For astronomers, “twinkling” just makes life harder. It blurs the light of distant stars and galaxies. So instead of a sharp pinpoint of light, a telescope sees a star as a fuzzy blob.

    Astronomers have developed some techniques to sharpen the view. They use small mirrors that move to compensate for the shifting light coming from a bright star in the telescope’s field of view, for example.

    Such techniques have improved the view dramatically. But they have some drawbacks. So a team of astronomers has proposed a new way to sharpen the view: with lasers aboard small satellites.

    The team is led by John Mather. He’s a Nobel Prize winner, and chief scientist for the next big space telescope. The team proposes launching one or more small, inexpensive satellites. The satellites would follow orbits that could keep them in view of a single telescope for hours — or even permanently.

    A satellite would beam a laser toward the telescope. An improved set of mirrors would bring that beam to a sharp focus. That would sharpen the telescope’s entire field of view. The technique could be especially valuable for a new generation of giant telescopes.

    The team says the system could be developed fairly quickly and inexpensively — allowing telescopes on the ground to see the universe as clearly as those in space.
     

    Script by Damond Benningfield

    Support McDonald Observatory


  • Posted on 10 Jun 2021

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