StarDate PodcastAuthor: McDonald Observatory
23 Feb 2019

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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    Abu Simbel

    Abu Simbel, in southern Egypt, is a masterpiece of design and construction — times two. The temple was built more than 32 centuries ago to honor Ramses II, one of the greatest of all pharaohs. And it was rebuilt just half a century ago to save it from the Nile. Both projects were guided in part by the rising Sun.

    The complex consists of two temples. One honors Ramses himself, while a smaller one honors his Great Royal Wife, Nefertari. The temples were carved into the base of a cliff above the Nile at the southern border of ancient Egypt.

    Four giant statues of Ramses guard the entrance to his temple. It consists of several chambers, which reach 185 feet into the cliff. The chamber at the back is the smallest. It houses the seated figures of Ramses and the gods Amon-Re, Re-Horakhte, and Ptah.

    Twice each year — on February 22nd and October 22nd — the rays of the rising Sun shine down the long hallway and into the rear chamber. The sunlight illuminates all of the seated figures except Ptah. Since he was a god of the underworld, he was intentionally left in the dark.

    When a dam was built along the upper Nile in the last century, the river’s rising waters endangered Abu Simbel. So the complex was cut apart and reassembled a couple of hundred feet higher. The reconstruction maintained the solar alignment. So Ramses and the two forms of the Sun god Re still receive the Sun’s life-giving rays at the same time each year.

    Script by Damond Benningfield

  • Posted on 22 Feb 2019

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    Rocket to Nowhere

    One of the most powerful rockets ever built made its first flight 50 years ago today. It was designed to carry cosmonauts to the Moon. Instead, it was a rocket to nowhere. All four of its test flights failed, and the remaining boosters were scrapped.

    The N1 was the Soviet Union’s answer to the American Saturn 5 Moon rocket. But its development was plagued by problems. Soviet leadership didn’t provide enough money, and often meddled in the space program. The agencies that built rockets and spacecraft fought with each other, with their leaders trying to sabotage the others.

    So when the first N1 stood on its launchpad in Kazakhstan, it wasn’t ready to fly. But America had already sent three astronauts around the Moon, and was planning to land on the Moon in a few months. So the Soviets didn’t want to fall too far behind.

    The first stage of the N1 was powered by 30 engines, which proved to be a problem. When the first model lifted off, on February 21st, 1969, two engines shut down within seconds. Vibrations damaged another engine, which began leaking. Seconds later, another leak developed, filling the engine compartment with propellants, which caught fire. The control system shut down the other engines just 68 seconds after launch. The dead booster hit the ground two minutes later.

    Three other test flights failed as well. The N1 was done — and so was the Soviet Union’s effort to send cosmonauts to the Moon.

    Script by Damond Benningfield

  • Posted on 21 Feb 2019

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    In late 2011, physicist Rainer Weiss was checking out an instrument in Washington state that he’d helped create. It was one of two sites of LIGO — an observatory designed to “listen” for gravitational waves — tiny ripples in space-time. The project was in its early stages, and Weiss was pondering what it might find.

    Weiss got what he asked for, and not just once. As of the end of last year, scientists had reported the discovery of 10 sets of merging black holes. The discoveries confirmed one of the predictions in Albert Einstein’s theory of gravity — and helped earn Weiss a share of the 2017 Nobel Prize in Physics.

    Detailed analysis of the waves revealed the distances to the black holes. They also revealed the masses of the black holes, both before and after they merged. The heaviest merged black hole was about 80 times the mass of the Sun.

    And scientists could be hearing the “chirp” of merging black holes more often in the future. LIGO is scheduled to return to work this month after an upgrade. It’s also working with a European project, called VIRGO. That should make it possible to detect merging black holes that are farther away. It could also allow the observatories to detect other sources of the waves — more ripples in the universe.

    Script by Damond Benningfield

  • Posted on 20 Feb 2019

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    A buzzing insect, a speeding locomotive, and a pair of merging black holes have something in common: They all produce gravitational waves. These “wiggles” in space-time are so puny, though, that only those produced by the black holes are detectable. In fact, by the end of last year, scientists had detected the waves from 10 black-hole mergers.

    Those detections were made with LIGO — a pair of observatories in Louisiana and Washington state. And the last few detections were aided by an observatory in Europe.

    Gravitational waves are produced by moving objects. They’re incredibly tiny, though, so they’re incredibly hard to find. It takes a massive object moving at extremely high speed to produce waves that are big enough to detect.

    Each of LIGO’s detectors consists of mirrors placed at the ends of two vacuum chambers that are more than two miles long. A laser beam is split in two and reflects back and forth off the mirrors.

    If a gravitational wave passes by, it compresses one of the arms by about one ten-thousandth the width of a proton. That’s enough to be recorded by sensitive detectors. The event must be “seen” by both LIGO sites to be considered a true detection.

    Merging black holes are good targets because they’re small but heavy. And just before they merge, they’re moving at a good fraction of the speed of light. That whips up space-time, producing waves that are just big enough for LIGO to record.

    More tomorrow.

    Script by Damond Benningfield

  • Posted on 19 Feb 2019

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    Moon and Regulus

    When you look into the night sky, all of those little pinpoints of light look pretty much the same. A few are brighter than the others, and a few show some color. But otherwise, there’s little to tell them apart.

    From up close, though, it’s a different story. Consider Regulus, the bright heart of Leo, the lion. It rises below the full Moon this evening and follows the Moon across the sky later on.

    To the eye alone, Regulus is simply an especially bright star. But telescopes reveal that Regulus is actually two stars — the big, bright one that we can see, plus a tiny stellar corpse known as a white dwarf. And the bright star is quite different from our own Sun; instead of being nice and round, it’s about a third bigger through the equator than through the poles.

    That shape is caused by the star’s rotation: It makes one full turn every 16 hours, compared to almost a month for the smaller Sun. That rapid spin may be the result of interactions with its tiny companion.

    The companion probably began life as the bigger and heavier star. Because of its greater mass, it aged more rapidly, puffing up to giant proportions. As it grew, it began dumping gas on the bright star we see as Regulus. That made Regulus heavier, causing it to spin faster. Regulus eventually took most of the other star’s gas, leaving a small white dwarf — and a star system that’s quite different from most of the others that twinkle through the night sky.

    Script by Damond Benningfield

  • Posted on 18 Feb 2019


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