- **Boulders Escaping from Asteroid Dimorphos:** Astronomers have made fascinating discoveries about numerous boulders seen swarming around the asteroid moon Dimorphos. This intriguing phenomenon is believed to be a result of the Double Asteroid Redirection Test (DART) asteroid impact mission conducted last year.
- **New Discoveries in Black Holes:** Exciting news from the world of astronomy as scientists have identified a novel and captivating feature of black holes. This discovery, seemingly straight out of a science fiction movie, has sparked the imagination of researchers and the general public alike.
- **Communication Disruption between Houston and International Space Station:** A significant incident occurred when a power outage disrupted the communication between Mission Control in Houston and the crew aboard the International Space Station. This event underscores the challenges faced by space agencies in maintaining uninterrupted communication with astronauts in orbit.
- **August Skywatch:** In this episode, we delve into various celestial phenomena occurring in August. Our focus will be on Antares, a giant star, as well as Barnard's star, the second nearest star system to the Sun. Additionally, we will discuss the eagerly anticipated annual Perseids meteor shower.
#spacetime #space #astronomy #science #news #podcast
AI Transcript
STUART GARY: This is Spacetime series 26 episode 93 for broadcast on the fourth of August 2023. Coming up on Spacetime boulders discovered escaping from the asteroid dimorphic new features discovered in black holes and Houston. We have a problem all that and more coming up on space time.
Welcome to space time with Stuart Garry.
STUART GARY: Astronomers have discovered several dozen large boulders swarming around the asteroid moon dimorphic.
STUART GARY: Their detection comes in the wake of last year's Double Asteroid Redirection Test or DART asteroid impact mission. The mission was designed to see if NASA could nudge a potential earth impacting asteroid off course so that it would miss our planet. See, why would asteroids present a real collision hazard to earth.
STUART GARY: Scientists estimate that an asteroid measuring about 10 kilometers across, smashed into the earth 66 million years ago, wiping out 75% of all life on the planet, including all the non avian dinosaurs. But unlike the dinosaurs, humanity can avoid such a fate if we begin practicing.
STUART GARY: Now on how to knock earths approaching asteroids off course, trouble is this is far trickier than what's been depicted in Hollywood movies. See planetary scientists first need to know how the asteroid was assembled. Are we talking about flying piles of rubble?
STUART GARY: In other words, loosely agglomerated rocks or are we talking about something more substantial, a single solid boulder the size of a mountain? This information will help provide strategies on how to successfully deflect a menacing asteroid. As a first step NASA did an experiment last year smashing an impact of spacecraft called DART into an asteroid to see what would happen.
STUART GARY: The half ton impact of spacecraft smacked into the asteroid dimorphic on September 26th at approximately 23,000 kilometers per hour, the impact was so severe. It altered dimorphic orbit around the larger asteroid Diddy Mos by around half an hour.
STUART GARY: Astronomers using the Hubble space telescope have been continuing to follow the evolving aftermath of the collision and they've now discovered several dozen boulders were lifted off the asteroid following the smash up a report in the Astrophysical Journal letters claims the Hubble images show boulders looking like a swarm of bees very slowly moving away from the asteroid.
STUART GARY: This might mean that smacking an earth approaching asteroid itself could result in a cluster of threatening boulders heading in our direction. In other words, instead of one single big asteroid, you could have a whole bunch of little ones.
STUART GARY: Now based on Hubble photo Mery, the 37 free flung boulders range in size from around one to something like 8 m across. And although they're traveling with the asteroid. They're also slowly drifting away from it a little more than one kilometer per hour.
STUART GARY: The total mass of these detected boulders is thought to be about one per cent of the mass of dimorphic itself. The study's lead author David Joette from the University Of California, Los Angeles says it's a spectacular observation showing a cloud of boulders carrying mass and energy away from the impact target.
STUART GARY: And the numbers sizes and shapes of the boulders are all consistent with them having been knocked off the surface of dimorphic by the impact. Now, this tells scientists for the first time what happens when you hit an asteroid and see material coming off. It.
STUART GARY: Duet says it opens up a new dimension for studying the aftermath of the DART experiment using the European Space Agency's upcoming Hera spacecraft which will arrive at the binary asteroid system in 2026. Hera will perform a detailed post impact survey of the target asteroid and the boulder cloud will still be in the process of dispersing when Hera arrives.
STUART GARY: Duet says it's like a very slowly expanding swarm of bees that eventually will spread along the binary pair's orbit around the Sun. He says the boulders are most likely not shattered pieces of the asteroid caused by the impact, but rather they were boulders already scattered on the asteroid surface.
STUART GARY: The type seen during the last close up images taken by the DART spacecraft just two seconds before the collision when it was about 10 kilometers above the surface. Joette estimates that the impact shook about two per cent of the boulders off the asteroid surface.
STUART GARY: He says the boulder observations by Hubble also give an estimate for the size of the DART impact crater. He says the boulders could have been excavated from a circle about 50 m across on the surface of dimorphic. Hero will eventually determine the actual size of the crater.
STUART GARY: Long ago, dimorphic may have been formed from material shed into space by the larger asteroid dimos.
STUART GARY: The parent body may have spun up too quickly or it could have lost material through a Glans in collision with another object. The ejected material then formed a ring that gravitationally coalesced over time to form dimorphic and this would make dimorphic a flying rubble pile of rocky debris loosely held together by the relatively weak pull of gravity.
STUART GARY: Therefore, Duet says the interior is probably not solid but is a structure more like a bunch of grapes. It's not clear how the bowlers were lifted off the asteroid surface.
STUART GARY: They could have been part of an ejector plume that was photographed by Hubble and other observatories during the DART impact or a seismic wave from the impact could have rattled through the asteroid sort of like hitting a bell with a hammer shaking loose the surface rubble.
STUART GARY: Duet says that monitoring the boulder's future movements may provide enough data to pin down their precise trajectories and that will allow scientists to determine in which directions they were launched from the surface. This is space time still to come.
STUART GARY: Astronomers have identified a new feature of black holes. It sounds like it may have come straight out of a science fiction novel. And Houston, we have a problem, the blackout that affected the Johnson Space Center, all that and more still to come on space time.
STUART GARY: Astronomers have identified a new feature of black holes that sounds like it may have come straight out of a science fiction novel. They've detected a quasi periodic oscillation signal embedded deep in the micro quasar beaming out of a distant black hole, black holes are immense gravitational wells created by the death of massive stars in core collapsed supernova explosions.
STUART GARY: The gravitational force of these objects is so strong that the escape velocity from a black hole would exceed the speed of light. And since nothing can travel faster than light, nothing, not even light can escape a black hole. Hence the name, once beyond the black hole's event horizon, a sort of point of no return matter and energy will fall forever towards the black hole's singularity.
STUART GARY: However, outside this event horizon material can still escape when material comes into contact with the area around the black hole, it's scooped up into an accretion disk where immense gravitational forces crush and rip it apart, releasing vast amounts of energy and material.
STUART GARY: These are guided by powerful magnetic forces into beams traveling perpendicular to the accretion disk often at superluminal speeds, the most powerful of these beams which emerge from super massive black holes millions to billions of times the size of their stellar counterparts. And found that the centers of most Galaxies form quasars bright enough to be seen across the other side of the universe.
STUART GARY: But a subset of accreting stellar mass black holes can also launch jets of highly magnetized plasma referred to as micro quasars. Now, a report in the journal nature studying a galactic micro quasar cataloged as GS 1915 plus 105 has discovered features in the quasar that have never been detected before using the 500 m aperture spherical radio telescope. In China.
STUART GARY: Astronomers have for the first time detected a quasi periodic oscillation signal in the radio band of the quasar quasi periodic oscillation signals are a phenomenon that astronomers use to understand how stellar systems like black holes function. And while they've been observed in x rays from micro quasars, their discovery in radio emissions in the quasar is unique.
STUART GARY: The study's lead author Wei Wang from Wuhan University says the quasi periodic oscillation signal had a rough period of about 0.2 seconds. That's a frequency of about five Hertz. Now, such a signal doesn't always exist and only shows up under special physical conditions. The authors were lucky enough to catch the signal twice once in January 2021. And again in June 2022.
STUART GARY: This unique feature may provide the first evidence of activity from a jet launched by a stellar mass black hole. Now, under the right conditions, some black holes in binary systems will launch a jet, a mixture of parallel beams of charged matter, magnetic material that's moving at close to the speed of light. The detailed mechanism to induce this temporal modulation in a relativistic jet hasn't been identified.
STUART GARY: However, one plausible mechanism would involve the jet's direction regularly changing and then returning to the original direction. Once every 0.2 seconds, a misalignment between the spin axes of the black hole and its accretion disk could cause this effect which would be a natural consequence of the dragging of space time near a rapidly spinning black hole.
STUART GARY: What astronomers and physicists refer to as frame dragging. It's a fascinating prospect this space time still to come, Houston, we have a problem. A blackout hits the Johnson Space Center in Houston, Texas. And we look at the giant star, Antares the second nearest star system to the Sun Barnard star and the annual Perseids meteor shower, all that and more coming up on August sky watch.
STUART GARY: Well, it was very much a case of Houston. We have a problem when a power outage disrupted communications between Mission Control and the crew aboard the International Space Station.
STUART GARY: The sudden blackout during work to upgrade other equipment at the Johnson Space Center prevented mission managers from sending commands to the space station or talking with the orbiting crew while the crew worried no danger during the outage, it still took 90 minutes for backup power to come online.
STUART GARY: The on station crew were told of the problem by Russian mission managers at their control center in Moscow about 20 minutes into the failure. It's the first time NASA's had to fire up the back up systems to take control something which should take place instantaneously when power is accidentally lost.
STUART GARY: NASA also maintains a back up control center on the outskirts of Houston in the event of a hurricane or other disaster requiring evacuations from the Johnson Space Center.
STUART GARY: That mission managers did need to move this time as the lights and air conditioning kept working because they were on a different circuit. This is space time and time now to turn our eyes to the skies and check out the celestial sphere for August on Skywatch.
STUART GARY: August is the eighth month of the year in the Julian Eggo calendars. It was originally named six Tillerson Latin because it was the sixth month of the original 10 month roaming calendar under Romulus in 7 53 BCE.
STUART GARY: When the year started in March, it only became the eighth month when January and February were added to the start of the year in the year eight BC. It was renamed in honor of the Roman statesman and military leader Augustus who had achieved several military victories including the conquest of Egypt during the month.
STUART GARY: Ok. Turning to the heavens and the constellation Scorpius, the Scorpion is high overhead this time of year covering almost a third of the August night skies. At the heart of Scorpius, located some 470 light years away is the red super giant Antares.
STUART GARY: A light year is a distance of about 10 trillion kilometers. The distance a photon can travel in a year at 300,000 kilometers per second. The speed of light in a vacuum and the ultimate speed limit of the universe, red super giants have the largest diameters of any known star.
STUART GARY: They evolve out of main sequence stars with more than eight times the mass of the Sun. A main sequence star is a star using hydrogen into helium in its core.
STUART GARY: When stars stop fusing hydrogen into helium in their core, the balancing act between gravity, pushing a star's mass down towards the center and energy from nuclear fusion in the core, pushing outwards ceases and gravity winds causing the star to begin to collapse inwards, crushing the stellar core until the increase in pressures and temperatures trigger helium fusion.
STUART GARY: At the same time, a shell of hydrogen around the core begins to fuse causing the star's outer gases envelope to expand out into a bloated giant. And now being further away from the core, the stellar surface starts to cool down becoming redder in color. While sunlike stars will become red giants, those that are far bigger eight times or more the mass of the Sun become red.
STUART GARY: Super giants, super giants will fuse all their core helium into carbon and oxygen within just a few million years, they'll then begin fusing this core carbon and oxygen into progressively heavier and heavier elements until they eventually begin to produce iron in their core.
STUART GARY: Now, no star, no matter how massive it is, is big enough to fuse iron into heavier elements. And so then the star will collapse catastrophically in what's known as a core collapse supernova, an explosion bright enough to outshine an entire galaxy.
STUART GARY: The end result of this core collapse supernova will be the creation of either a neutron star or a black hole depending on the progenitor star's mass. The name Antares means rival of Mars. And indeed, when they're close together in the sky, they do look very similar Antares or alpha scorpions.
STUART GARY: It's sometimes called, has some 12.4 times the mass and an incredible 450 times the diameter of our Sun and is one of the largest known stars in the universe. Antares is so big that we're a place where the Sun is at the center of our solar system.
STUART GARY: It would engulf all the inner planets, mercury Venus earth and Mars, its outer surface would reach almost as far as the orbit of Jupiter. Antares is a binary system. There's a companion star orbiting with it called Antares B.
STUART GARY: A massive spectral type B blue white star at least 7.2 times the mass and 5.2 times the radius of the Sun. It's located about 224 astronomical units beyond the primary star. An astronomical unit is the average distance between the Sun and the earth about 150 million kilometers or 8.3 light minutes.
STUART GARY: Astronomers describe stars in terms of spectral types, a classification system based on temperature and characteristics. The hottest, most massive and most luminous stars are known as spectral type O blue stars.
STUART GARY: They're closely followed by spectra type B, blue, white stars, N spectral type A white stars, spectra type F, whitish yellow stars, spectra type G yellow starss. That's where our Sun fits in spectra type K orange stars and the coolest and least massive of all stars are spectra type M red stars commonly referred to as red dwarfs.
STUART GARY: Now its spectra classification is further subdivided using a numeric digit to represent temperature with zero being the hottest and nine, the coolest and A Roman numeral to represent luminosity. Now put all that together and our Sun is a spectral type G two V or G 25 yellow dwarf star.
STUART GARY: Also included in the stellar classification system are spectral types LT and Y which are assigned to failed stars known as brown dwarves, some of which were actually born as spectral type M red dwarf stars but became brown dwarves after losing some of them mass brown dwarfs fit into a category between the largest planets which are about 13 times the mass of Jupiter and the smallest spectral type M red dwarf stars, which are about 75 to 80 times the mass of Jupiter or 0.08 solar masses located near Antares is the spectacular globular cluster Messier Four or M four.
STUART GARY: For short, named after the 18th century French astronomer and comet Hunter Charles Messier. It's one of a catalog of 103 fuzzy objects which weren't comets and so were of no interest to messier. And so he made a list of them. So he didn't waste his time looking at them.
STUART GARY: Other astronomers have since added further celestial objects to the catalog, bringing the turtle to around 110 located some 7000 light years away.
STUART GARY: Messier Four can be seen through a pair of binoculars making it one of the closest globular clusters to earth globular clusters are densely packed spheres containing thousands to millions of gravitationally bounced stars, which it's thought were either originally all born at the same time in the same stellar nursery or are the surviving core of Galaxies that have been cannibalized by larger Galaxies.
STUART GARY: They're almost always found orbiting the halo of Galaxies. The Milky way has about 150 of them and they're all usually very ancient, some dating back to around 12 billion years located just below the Sting of Scorpios are two open star clusters.
STUART GARY: M Six and M seven M seven's. The nearer of the two located about 800 light years away. While M Six is a more distant 2000 light years, open clusters are less densely packed than their globular cluster counterparts.
STUART GARY: With the stars inside them less gravitationally bound and more prone to drifting away over time. Another open star cluster in Scorpius is NGC 62 31 located about 6500 light years away just near the star Zeta Scorpio NGC.
STUART GARY: 62 31 is a bright open star cluster containing around 100 and 20 stars, including a significant population of highly luminous super giants, numerous white yellow stars and at least two wolf rayt stars, wolf rays are extremely luminous evolved stars reaching the ends of their lives, having run out of hydrogen for core fusion.
STUART GARY: They're no longer on the main sequence and are instead fusing progressively heavier and heavier elements in their cores. This causes them to have surface temperatures of up to 200,000 degrees Celsius.
STUART GARY: And such extreme temperatures generate powerful stellar winds just behind Scorpius is the constellation Sagittarius, the half man, half horse of Greek mythology. And as we mentioned in last month's Skywatch, the center of the Milky way galaxy is found in Sagittarius, roughly 27,000 light years away.
STUART GARY: The name Sagittarius can be traced back beyond the Greeks to the ancient Mesopotamian Archer, God, Norgle. Sagittarius is known for its many nebula and clusters more than any other constellation. One of the largest and brightest is the globular cluster.
STUART GARY: M 22 big enough to be visible to the unaided eye located about 10,600 light years away near the galactic bulge. M 22 is more elliptical than most globular clusters. It's located just south of the ecliptic, the plane in the sky upon which all the planets orbit the Sun and it contains over 70,000 stars covering an area of around 100 light years.
STUART GARY: It also contains at least two black holes and is one of only a handful of globular clusters known to contain planetary nebulae. The puffed off outer gasses envelopes of dead Sun like stars located in the sky next to Scorpius in the West and Sagittarius in the east is the constellation of Eus.
STUART GARY: The healer or serpent bearer often portrayed as a snake curled around a man in Greek mythology. Ofus raises a R from the dead after he was bitten by Scorpius.
STUART GARY: Oye contains several star clusters and other interesting features including Barnard star. Barnard star is the second nearest star system to the Sun beaten only by the Artur Centauri triple star system located some 5.9 light years away. Barnard's star is a spectral type M red dwarf about 0.144 times the mass of the Sun.
STUART GARY: Our Sun is around 4.6 billion years old at between seven and 12 billion years of age. Barnard's star is considerably older than the Sun and may be among the oldest stars in the Milky way galaxy.
STUART GARY: It's lost a great deal of rotational energy and its periodic slight changes in brightness indicate that it's rotating about once every 130 days. By comparison, our Sun rotates roughly once every 29 days given its age. Barnard star was long assumed to be quiescent in terms of stellar activity.
STUART GARY: But in 1998 astronomers observed an intense stellar flare, indicating that Barnard star is indeed a flare star, flare stars are variable stars. They can undergo unpredictable, dramatic increases in brightness lasting a few minutes.
STUART GARY: It's believed that the flares of flare stars are analogous to solar flares in the Sun in that they're generated by stellar magnetic energy stored in the star's atmosphere lying just to the West of the Scorpion is the constellation Libra. The scales in Greek mythology, Libra represents the cause of Scorpius, the Scorpion.
STUART GARY: However, the Romans considered Libra a distinct separate constellation from Scorpius and thought them to be the scales symbolizing the equinoxes the times of the year in March and September when the earth gets equal lengths of day and night.
STUART GARY: That's because 2000 years ago, when all this was made up, the Sun moved into Libra at the time of the September equinox. But due to recession, as the earth's spin axes wobbles in direction, this point in time has now moved into the adjoining constellation of Virgo.
STUART GARY: If you look to the south and the southern cross, that's the constellation Centaurus, another half man, half horse mythical beast, Centaurus was the teacher of many of the Greek gods and heroes. He was placed among the stars in the heavens after accidentally being cured by a poison arrow fired by Hercules close to the point of star nearest the southern cross.
STUART GARY: Beta Centauri lies NGC 51 39 Omega Centauri, the largest and brightest globular cluster in the visible sky because of its brightness. The ancient Greek mathematician and astronomer Claudius Tole originally thought Omega Centauri was a star. It has a diameter of more than 100 and 50 light years and contains an estimated 10 million stars giving it some 4 million times the mass of our Sun located some 15,800 light years away.
STUART GARY: Omega Centauri is another very ancient globular cluster around 12 billion years old and it contains many so-called population two stars. These are the second generation of stars to have formed and were created directly out of the remains of the very first stars in the universe. Stars in the core of Omega Centauri are so crowded. They're estimated to average only 0.1 light years away from each other.
STUART GARY: And that compares to the nearest start Our Sun Proxima Centauri, which is some 4.2 light years distant, located close to Mega Centauri in the sky is the giant lenticular galaxy NGC 5128 Centaurus A which we see looking like it's split in half by a thick band of dust. The galaxy was discovered in 18 26 by astronomer James Dunlop from his home in what is now the Sydney suburb of Parramatta.
STUART GARY: A time long before the bright lights of a modern city would make such a discovery impossible. Located some 13 million light years away. Centaurus Sea is one of the strongest radio sources in the sky and is thought to be the result of a merger between an elliptical and a spiral galaxy. It can be easily seen using a pair of binoculars, but you'll need a telescope to make out its spectacular dust lanes.
STUART GARY: August is also the time of the peak of the annual Perseids meteor shower. The Meteors are the debris trail ejected by the comet swift tuttle as it travels along its 133 year orbit through the solar system. As its name suggests, the Perseid's radiant, that is the point of the sky from which the Meteors appear to originate lies in the constellation of perseus.
STUART GARY: The Perseids are one of the oldest known meteor showers with early Chinese historical records of its activity going back almost 2000 years. They're active between July the 17th and August the 24th with a peak on August 12th with around 60 Meteors an hour being visible.
STUART GARY: The Perseids are very bright and fast moving Meteors traveling at speeds of 59 kilometers per second. They're best seen between midnight and just before dawn producing long bright trails and some fireballs. Most Perseids burn up in the atmosphere at altitudes of over 80 kilometers. They're best seen from the northern hemisphere.
STUART GARY: So for southern hemisphere skywatchers look to the north with the radiant below the northern horizon, there are two full moons in August. The first occurred on August the first, it was a perigee full moon or super moon because it was a bit closer to the earth than average and consequently appeared slightly larger.
STUART GARY: Although you wouldn't have noticed it in real life. By the way, this was the fourth super moon in a row and the biggest and brightest super moon of the year. Now, the farmers' Orman Act also listed this full moon as a Sturgeon moon named after North America's biggest fish because large numbers of sturgeons are found in the Great Lakes this time of year in other parts of the world.
STUART GARY: It's often referred to as a green moon, a corn moon, a les moon and even a lightning moon. So you've got plenty of names to choose from. The second full moon of the month will be on August, the 30th and that will make it a blue moon according to some definitions.
STUART GARY: However, NASA says the traditional definition of a blue moon refers not to the second full moon of the month, but the third full moon in a season that has four full moons turning to the planets now and Venice and Jupiter have both dropped into the solar glare ending their lengthy rains as evening stars, mercury remains above the horizon in the western evening twilight at magnitude zero with Mars six times fainter than mercury hovering just above it.
STUART GARY: On August the ninth, the moon will form a pre dawn conjunction with Jupiter. And on August 20th, Venus will rise before dawn becoming the morning star for coming months. On August the 27th, Satin will arrive at opposition its brightest of the year. This means it'll be directly opposite in the sky from the Sun, making a spectacular night time observational target.
STUART GARY: Satin now rises at sunset and remains out all night. And on August, the 30Th Satin will hover just above the full moon after nightfall and as Satin is at its best right now, it'll be easy to identify by using the full moon as a guide.
STUART GARY: This is space time and that's the show for now. Spacetime is available every Monday, Wednesday and Friday through Apple Podcasts, itunes, Stitcher, Google Podcast, pocket casts, Spotify, a Cast Amazon music bites dot com, Soundcloud, YouTube, your favorite podcast download provider and from space time with Stewart Gary dot com.
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