EVSN - Luminous Kilonova Challenges Gamma-ray Burst Theories

Catching the birth of a magnetar

0:00It's the 365 Days of Astronomy podcast, coming in 3, 2, 1. This is the Daily Space for today, Friday, November 13th, 2020.

0:31I am your host, Beth Johnson, and I am here to put science in your brain. Unfortunately, Dr. Pamela is dealing with a host of grant deadlines, so I'm flying solo today. And now, the science.

0:47Sometimes in astronomy, you get lucky. The sky is big, and many astronomically interesting events are extremely rare and brief. This means you have to be looking at exactly the right place, at the right time, and with the right instrument to detect key events. We can increase our chances of catching rare events by keeping survey scopes crawling the sky for flickers of light. And today we have observatories like SWIFT that are keeping watch in gamma ray light, and the Zwicky Transient Facility is out there watching invisible light. At the same time, many of the world's telescopes have agreements in place that say, in case of something awesome, drop what you're doing and go look.

1:25And back in May, this combination of watching with SWIFT and dropping everything to go look with just about everything else may have allowed the astronomical community to catch the birth of a magnetar. A special kind of neutron star that has a massive magnetic field capable of releasing tremendous bursts of energy. It all started with a short flash of gamma rays. Short gamma ray bursts, events that release massive amounts of energy for less than two seconds, are caused by two neutron stars merging into a new, single object.

1:59These events are called kilonovae, and back in August 2017, one such event was observed in light, gravitational waves, and neutrinos. That historic event produced a black hole, but it now appears that in some instances, the merging neutron stars take a different, more luminous path. When the SWIFT telescope spotted that new short gamma ray burst in May, it triggered a myriad of telescopes to redirect their efforts to its location on the sky. From Hubble to VLA to Keck, these scopes and many more all measured everything they could.

2:35And because Hubble was able to be involved, observing team quickly realized that the afterglow of light was ten times more luminous than expected. If these merging objects had formed a black hole, the only sources of light would have been the warm material shocked during the kilonova. If the merging neutron stars were small enough, however, they could instead form a new, larger neutron star, which would not only be glowing hot, but we'd be transferring energy to surrounding material via its strong magnetic field.

3:05According to study co-author Tan Moilaskar, you basically have these magnetic field lines that are anchored to the star that are whipping around at about a thousand times a second, and this produces a magnetized wind. These spinning field lines extract the rotational energy of the neutron star formed in the merger, and deposit that energy into the ejecta from the blast, causing the material to glow even brighter. Magnetars are fairly rare objects that are thought to most often form via the death of a single massive star.

3:36This event, the merger of two smaller neutron stars, shows that magnetars can form in more than one way. It's thought that this is a more rare way for magnetars to form, but we will need to keep looking and keep getting lucky in order to get a better understanding of the real statistics. For now, this research is published in the Astronomical Journal with lead author Wen-Fai Fong.

4:02From getting lucky to getting creative, our stories run the gamut of space science today.

Water loss on Venus and Mars

4:07My next two deal with water on Venus and Mars, and both are the product of graduate students. Moa Persson, of the Swedish Institute of Space Physics, or IRF, and Ulmeo University, is defending her doctoral thesis on the subject of just how much water has escaped from Venus' once-tempered surface out into space. And she has found that the amount is not that much, relatively speaking. Persson analyzed data collected by IRF's instrument on Venus Express, Aspera IV, to determine how many ions were collecting around Venus.

4:41These ions turned out to be, on average, one oxygen atom for every two protons, which indicates water. Ionized hydrogen, of course, is one proton. Persson then noted that the level of ion escape varied with the solar cycle. And if something does a thing now, it likely has done a thing in the past. When the sun is quieter, during solar minimum, more protons escape the atmosphere. During solar maximum, the solar winds are stronger, and the protons end up back in the atmosphere more than they escape.

5:12As Persson states, the surface of Venus today is comparable to hell. It is extremely dry and has a temperature of 460 degrees. But historically, the surface was more hospitable with a wealth of water that could reach a depth of several hundreds of meters if spread equally over the surface. This water has disappeared from Venus. My thesis shows that only a few decimeters of this water has escaped to space. Note, a decimeter is one-tenth of a meter. This research has implications for other planets like Earth and even Mars, which once held liquid water itself and can be used for comparison to similar studies.

5:48And speaking of Mars, University of Arizona researchers have discovered a surprisingly large amount of water in the upper atmosphere, being rapidly destroyed. Another graduate student, Shane Stone, has analyzed data taken by NASA's MAVEN mission. He explains, We know that billions of years ago, there was liquid water on the surface of Mars. There must have been a thicker atmosphere, so we know that Mars somehow lost the majority of its atmosphere to space. MAVEN is trying to characterize the processes responsible for this loss, and one portion of that is understanding exactly how Mars lost its water.

6:24As MAVEN orbits Mars, it dips into the planet's atmosphere every few hours. The on-board neutral gas and ion mass spectrometer instrument measures the abundance of water ions in the upper atmosphere, 100 miles up from the surface. This measurement allows scientists to infer how much water is present. Mars' water loss, it turns out, is mostly affected by the seasons on Mars itself. During the Martian summer in the Southern Hemisphere, Mars is closest to the Sun and warms up accordingly.

6:54At this time, more water changes from ice to vapor and rises into the atmosphere. Regional dust storms that occur about every 10 years cause even more heating and more water loss. Stone goes on to further explain, This is important because we didn't expect to see any water in the upper atmosphere of Mars at all. If we compare Mars to Earth, water on Earth is confined close to the surface because of something called the hygropause. It's just a layer in the atmosphere that's cold enough to condense and therefore stop any water vapor traveling upward.

7:26The hygropause on Mars, it seems, is too warm to prevent the water vapor from escaping to the upper atmosphere, and once there, the process is simple for breaking the vapor into ions. The research team then extrapolated these findings back 1 billion years and found that they can account for the loss of a global ocean about 17 inches deep. And those dust storms could have caused the loss of an additional 6.7 inches of ocean depth, which could explain why Mars is so cold and dry compared to Earth. Prior to 1 billion years ago, the hygropause on Mars may have been stronger,

7:59so there is still more to be learned about the red planet and its relationship with water.

Radioactive elements and planet habitability

8:06Liquid water, it turns out, is no longer the only criteria considered important for the habitability of a world. Scientists at the University of California Santa Cruz have found that the amount of radioactive elements, particularly the longer-lived ones, incorporated into rocky planets may be a crucial factor in the potential for life. Radioactive decay of heavy elements such as thorium and uranium in the core of Earth drives our plate tectonics and might even contribute to the generation of our magnetic field. That magnetic field helps protect us from dangerous solar and cosmic rays,

8:40which helps life survive on the surface. The new findings, published this week in Astrophysical Journal Letters, show that the supply of radioactive elements in the Earth's core generates more than enough heat to drive the geodynamo that creates our magnetic field. First author Francis Nimmo explained, What we realized was that different planets accumulate different amounts of these radioactive elements that ultimately power geological activity and the magnetic field. So we took a model of the Earth and dialed the amount of internal radiogenic heat production

9:11up and down to see what happens. It turns out that if a planet has too much radiogenic heating, it cannot sustain a dynamo, because the heavier elements end up in the mantle, and a hotter mantle becomes an insulator, preventing the core from losing enough heat quickly enough to generate the convection necessary for a magnetic field. You also end up turning the volcanism to full blast and cause more extinction events. On the other hand, if the planet doesn't have enough radiogenic heating,

9:42the planet has no volcanism and is geologically dead. Nimmo goes on to note, Just by changing this one variable, you sweep through these different scenarios from geologically dead to Earth-like to extremely volcanic without a dynamo. Now that we see the important implications of varying the amount of radiogenic heating, the simplified model that we used should be checked by more detailed calculations. So, how does a geodynamo add to habitability? Scientist and exoplanet expert Natalie Batalia explains,

10:13It has long been speculated that internal heating drives plate tectonics, which creates carbon cycling and geological activity like volcanism, which produces an atmosphere, and the ability to retain an atmosphere is related to the magnetic field, which is also driven by eternal heating. Once again, we add more pieces to the puzzle of what drives life.

Extinction events and dinosaur rise

10:35On the other side of the coin, we have processes that have caused the destruction of life. In fact, there have been multiple extinction events in Earth's past, including the largest such event, the end Permian extinction, which wiped out 95% of all marine species on Earth. Not long after that, scientists have found a smaller but nonetheless impactful extinction event called the Carnian Pluvial Episode, or CPE. And they have been working to understand that smaller event that came during a time period

11:06when our planet was in the midst of recovering from the end Permian. The CPE was not a stunning swift die-off like the other event I already mentioned or the later dinosaur-killing event, and it took scientists working across multiple disciplines to piece together an overview. As they've grown to understand the CPE, it turns out that, number one, it's a bigger extinction event than previously thought, and number two, it directly led to the ascendancy of the dinosaurs. This most recent work, published in Science Advances,

11:37looked at the rainfall from this event. Per the press release, the CPE is named for the stage of the late Triassic in which it occurred, the Carnian, and for its signature feature, rain. A lot of rain, in four main pulses lasting over a million years, fell across much of the supercontinent of Pangaea. Along with all the rain, there was global warming, as well as ocean anoxia and acidification, killing off a third of the marine species that were left, or rose after the end of Permian, and leading to further diversification

12:07of the remaining species. Study co-author Mike Benton noted that this period led to the rise of modern reefs and plankton in the oceans, and the rise of modern petropod groups like frogs, lizards, turtles, crocodilians, dinosaurs, and mammals, along with some important plant groups such as conifers, and some new groups of insects. Dinosaurs are the forerunners of modern-day birds, so this little-known extinction event actually played a key role in modern ecosystems. One more piece of the puzzle for life here on Earth.

12:40Okay, enough death and destruction, let's take a look at a pretty picture.

Galaxy clusters and the Perseus images

12:44You can see this on dailyspace.org. Astronomers used the Very Large Array to look at how crowding affects the galaxies in the Perseus Cluster, which is about 240 million light-years from Earth. The results of these observations are published in the monthly notices of the Royal Astronomical Society. On the left is NGC 1275, which is at the core of the cluster and seen in detail, including a newly revealed complex filamentary structure in its lobes. The center image shows galaxy NGC 1265

13:15and the effects of its motion through the material between the galaxies. You can see its radio jets are bent backward and merge into a single broad tail, which is further bent. Finally, on the right, the jets of the galaxy IC 310 are bent backward, similarly to the center galaxy. Marie-Lou Gendra Marsole, an ESO ALMA fellow in Santiago, Chile, said, These images show us previously unseen structures and details, and that helps our effort to determine the nature of these objects.

13:48From Pretty Pictures, we turn to a quick rundown of some interesting items

SpaceX certification and Crew-1 launch

13:52in our press release file. First, Earth has captured a tiny object from its orbit around the sun and will keep it as a temporary satellite for a few months before it escapes again. The cool thing here is that the object is not an asteroid, but probably the Centaur upper-stage rocket booster that helped lift NASA's ill-fated Surveyor 2 spacecraft toward the moon in 1966. Scientists using the Pan-STARS-1 Survey Telescope and the Center for Near-Earth Object Studies made the determination.

14:23Per the press release, the Surveyor 2 lunar lander was launched toward the moon on September 20, 1966 on an Atlas Centaur rocket. The mission was designed to reconnoiter the lunar surface ahead of the Apollo missions that led to the first crewed lunar landing in 1969. Shortly after liftoff, Surveyor 2 separated from its Centaur upper-stage booster as intended, but control of the spacecraft was lost a day later when one of its thrusters failed to ignite, throwing it into a spin. The spacecraft crashed into the moon

14:53just southeast of Copernicus Crater on September 23, 1966. The spent Centaur upper-stage rocket, meanwhile, sailed past the moon and disappeared into an unknown orbit about the sun.

15:08Next up, a little light news. Researchers have measured what is now the shortest time ever, 247 zepto-seconds. It is the amount of time it takes for a photon to get from one side of a hydrogen atom to the other side. A zepto-second is a trillionth of a billionth of a second. In somewhat more understandable terms, quote, there are as many zepto-seconds in one second as there are seconds in 2,500 times the age of the universe, which is about 13.8 billion years old.

15:40End quote. How did they get this measurement? They bombarded hydrogen gas with x-ray light. As the x-ray photons hit the hydrogen atoms, it ejected first one electron and then another. These two electrons caused a wave in the gas, spreading out like ripples in a pond. Since they each started a wave pattern, the patterns overlapped and created an interference pattern. Had the electrons been ejected at the same time, the pattern would have been symmetrical around the center of the H2 molecule. However,

16:10the electron waves were slightly off from one another and the time lag was what gave the researchers the 247 zepto-seconds measurement. All of this was done using a reaction microscope and the results were published in Science.

16:25Speaking of science, the groundbreaking science book Philosophe Naturalis Principia Mathematica, or Newton's Principia, was first published in 1687. A team at Caltech recently completed a new census of copies of that first edition, and in very good news, they more than doubled the number cataloged in the previous census done in 1953. That brings the total number of surviving first editions to 386, and they estimate that another 200 or so are still out there uncataloged

16:56in private collections. Even more interesting, quote, by analyzing ownership marks and notes scribbled in the margins of some of the books in addition to related letters and other documents, the researchers found evidence that the Principia, once thought to be reserved for only a select group of expert mathematicians, was more widely read and comprehended than previously thought. Unquote. A portion of the newly cataloged copies were found in Eastern Europe, which would have been behind the Iron Curtain when the last census was done. First edition copies

17:27sell for anywhere from $300,000 to $3 million, and they were originally published thanks to funding from fellow scientist Edmund Haley of Haley's Comet fame. You can get your own modern version of Principia at local and online bookstores for far less, though.

17:45Finally, we are pleased to announce that SpaceX has received the first certification of a human-rated commercial space system in time for this weekend's Crew-1 launch to the International Space Station. NASA Administrator Jim Bridenstine said, I'm extremely proud to say we are returning regular human spaceflight launches to American soil on an American rocket and spacecraft. This certification milestone is an incredible achievement from NASA and SpaceX that highlights the progress we can make working together with commercial industry.

18:16And, weather permitting, we will be bringing coverage of the Crew-1 launch to you live, starting at 4.30 p.m. Pacific Standard Time, 7.30 p.m. Eastern Standard Time, 24.30 UTC, on our Twitch channel, twitch.tv slash CosmoQuestX. Please join us for all the launch festivities. This has been The Daily Space. Today's episode was written by Dr. Pamela Gay and Beth Johnson. Engineering is provided by Ali Pelfrey and web content is produced by Beth Johnson.

18:47You can get a complete transcript, show notes, and see images related to each of our stories at our website, dailyspace.org. We are a production of the Planetary Science Institute, a 501c3 non-profit dedicated to exploring our solar system and beyond. We are here thanks to the generous contributions of people like you. To learn more and donate today, please visit our website, CosmoQuest.org.

19:18You are listening to the 365 Days of Astronomy podcast. The 365 Days of Astronomy podcast is produced by the Planetary Science Institute. Audio post-production is by me, Richard Drumm. Project management is by Aviva Yamani.

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20:20we won't be able to share the stories that inspire the worlds. We invite you to join our community of storytellers and share your voice with the listeners worldwide. As we wrap up today's episode, we're looking forward to unraveling more stories from the universe. With every new discovery from ground-based and space-based observatories and each milestone in space exploration, we come closer to understanding the cosmos and our place within it. Until next time, let the stars

20:50guide your curiosity. Curiosity o, the stars.

20:55I'll see you next time.