On July 12th, 2018 we learned about

Looking for light in Antarctic ice has revealed a source of otherwise untraceable cosmic particles

Around four billion light years away, just to the left of the constellation Orion, an active galactic nucleus is blasting ultrahigh-energy cosmic rays and neutrinos right at us. This jet of particles and energy is the by-product of that galaxy’s central black hole shredding and consuming captured objects. As intense as such a stream of energy may be, this particular nucleus, named TXS 0506+056, appears even brighter than usual because it’s aimed straight at Earth, qualifying it as a blazar. The weird part of all this is that even though astronomers have long been able to detect the energy from this blazar across all bands of the electromagnetic spectrum, we’ve only just been able to trace the stream of particles it sends out for the first time.

Tracking the paths of particles

The two types of particles blasting out of TXS 0506+056 are cosmic rays and high-energy neutrinos, and both carry their own challenges for detection. The cosmic rays are mostly super-charged protons, which are known to be flying all around the universe. They can and do collide with other particles which makes their detection a bit easier, but because they are positively charged particles, their paths get bent and reshaped by every magnetic field they fly through. As such, even when you detect a cosmic ray, it’s nearly impossible to know where it came from on.

Neutrinos can help solve that problem, but not without creating challenges of their own. These tiny particles are sort of a neutral version of a proton, generally created when protons have been smashed and accelerated in the same conditions that would create cosmic rays. As their name implies, they are electromagnetically neutral and thus can fly through the cosmos without interacting with magnetic fields. This means that if they’re detected, you can count on them to have been moving in a straight line, creating a traceable path back to their source. However, detecting them is very difficult, because they’re so small, fast and neutral that they can fly through objects without interacting with anything. To really try to figure out where in space these super-fast particles, scientists had to build a very specialized detector in the ice of Antarctica.

Illumination in the ice

The IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station has turned a cubic kilometer of ice into the world’s best neutrino detector. Over 5,000 light sensors have been embedded in the ice in a grid formation. When a neutrino does happen to collide with atoms in the clear ice, it releases a cone of blue light that the detectors can then measure. By measuring which detectors see the brightest light, the original trajectory of the neutrino can be pieced together. After checking to eliminate collisions from slower neutrinos created by comic rays hitting Earth’s atmosphere, coordination begins with astronomers around the world to verify the high-energy neutrino’s suspected point of origin.

On September 22, 2017, a collision was detected in the ice that had the signature of galaxy-crossing, high-energy neutrino. An alert was then sent out to various telescopes around the world as quickly as possible so that they could look for any cosmic activity that could explain the neutrino’s trajectory. NASA’s orbiting Fermi Gamma-ray Space Telescope and the Major Atmospheric Gamma Imaging Cherenkov Telescope, or MAGIC, converged on the aforementioned TXS 0506+056 blazar. Researchers then looked at data from previous years to see if this trajectory was part of a possible pattern, and were able to find more instances of neutrino and gamma ray activity that also shared that point of origin. More data is obviously desired to really confirm these findings, but right now this all strongly suggests that we finally traced a high-energy neutrino back to its source.

A whole new way to know what’s in space

The idea that a blazar like TXS 0506+056 could pump out neutrinos and cosmic rays isn’t a shock. The energy necessary to get a neutrino and comic ray to be traveling close to the speed of light isn’t easy to come by, and something as violent as a blazar or galaxy collision would fit the bill. Learning more about such an object is obviously exciting, but the real significance of this detection is how it opens up a new way to study space and astrophysics. For the most part, everything we know about the universe outside our solar system has depended on measuring some portion of the electromagnetic spectrum, from radio waves to light to gamma rays. That energy can’t always be found though, and so tracking neutrinos gives us a whole new way to collect data on the universe. Coupled with the recent detection of gravity waves, scientists are comparing this so-called ‘multi-messenger’ detection to suddenly developing a new sensory organ in your body. We’ve long been able to see into space, but now we’ve gained a new way to touch it as well.


My fourth-grader asked: So if a neutrino can go through big objects without hitting them, can they pass through a black hole?

As the IceCube detector demonstrates, neutrinos can hit other atoms, but their speed, size and lack of charge helps them avoid doing so most of the time. None of those things offer a way to avoid the bent space-time of a black hole though, which can famously capture light which moves faster and has less mass than a neutrino. So while a black hole can help produce neutrinos and spray them into space, none of those neutrinos would be going anywhere if they’re aimed at the black hole itself.

Source: More than century-old riddle resolved—a blazar is a source of high-energy neutrinos by University of Wisconsin-Madison, Phys.org

On July 8th, 2018 we learned about

Triple star system demonstrates that gravity is agnostic to the density of neutron stars

To test an idea scientifically, you should aim to have an experimental condition that you can compare to a control. So for example, if you want to see if food coloring helps your flowers grow faster, you’d want to grow the same kind of flowers without food coloring for comparison. Now, setting up experimental conditions isn’t so tough when you’re talking about small plants in a flowerbed, but what if you’re interested in something that could only be observed in some of the most extreme conditions in the universe? Maybe something like the nature of gravity in ultra-dense neutron stars? In that case, you may need to get lucky and find PSR J0337+1715, a star system apparently ready-made for exactly those kinds of questions.

Different types of dying stars

The unfortunately-named PSR J0337+1715 is a triple star system some 4,200 light years from Earth. Two of these stars are white dwarfs, meaning they’re the decaying cores of larger stars from long ago. They no longer have the temperatures needed to enable nuclear fusion and push their mass outwards, and as such are collapsing back into themselves. This means that a white dwarf with the mass of our Sun would be only have the volume of Earth, making these stars significantly more dense than what’s in our solar system, although a lot of their shrinkage is thanks to material being lost altogether.

While this is clearly different from our Sun, in the case of PSR J0337+1715 the white dwarfs are providing the normal baseline for researchers’ observations. The neutron star, on the other hand, is where the major questions lie. Instead of slowly degrading like a white dwarf, a neutron star is the result of a much larger star collapsing all at once. It packs a lot more mass into a lot less space, leaving it with an incredible density, gravitational and magnetic fields. The gravitational field is so strong that an object falling from three feet above a neutron star’s surface would instantly fall at over three million miles per hour while also being spaghettified due to tidal forces. There was also a chance that these extremes would cause the whole neutron star to interact with gravity as a whole in a different way than less-dense objects, such as some conveniently-positioned white dwarf stars.

Detailed tracking of next to no deviation

As it happened, the neutron star of PSR J0337+1715 is paired with one of the white dwarf stars in its orbit around the second white dwarf. This means that researchers could track how both each of these dead stars moved around the same object, looking for differences in their acceleration that would point a difference in how gravity was affecting the neutron star. If that weren’t convenient enough, this particular neutron star was actually a pulsar, meaning it was emitting a strong blast of radio waves 366 times per second. This broadcast could then be used like a tracking device, allowing the Green Bank Telescope to follow the neutron star’s movement with incredible fidelity. Even though it was over 4,000 light years away, the neutron star’s location could be tracked to within a few hundred feet. While they couldn’t say that the neutron star’s orbit behaved in absolutely the same manner as its white dwarf partner, researchers could at least be confident any variation would be less than three parts per million.

As perfect as this triple star system was for measuring this kind of movement in a neutron star, none of this data is particularly surprising. While there have been proposals that super-dense objects like neutron stars would bend the rules of gravity, the observations from PSR J0337+1715 basically support predictions Albert Einstein made in his general theory of relativity. Known as the Equivalence Principle, the idea is that all objects interact with gravity in the same way, even if the mass involved is dense enough to crush and strip an object into goo at over three million miles an hour.

Source: Even phenomenally dense neutron stars fall like a feather by Green Bank Observatory, Science Daily

On May 10th, 2018 we learned about

Evidence related to the early days of our solar system found in an out-of-place asteroid

Found: Lost asteroid, spotted in the Kuiper belt, past Pluto

No collar or leash, but answers to the name 2004 EW95, and spots of  ferric oxides and phyllosilicates seem to be from asteroid belt near Mars. Please contact the Astrophysics Research Centre at the Queen’s University Belfast, UK if it’s yours.

Identifying an errant asteroid

Obviously, nobody is likely to respond to the above, because among other factors, nobody knew this asteroid was missing. When astronomers found the carbon-rich rock in the darkness of the Kuiper belt, they weren’t even sure of what they were seeing, as very little light can really be reflected off an 186-mile-long object 2,788,674,218 miles from the Sun. Still, it a wider range of light than its neighboring pieces of ice and rock, which is why researchers started to suspect that it wasn’t originally from that part of the solar system.

Most asteroids in the Kuiper belt are rather dull to look at. They don’t offer much variation in the frequencies of light they reflect off their surfaces. 2004 EW95, on the other hand, reflected light spectra consistent with  ferric oxides and phyllosilicates, minerals that would have originated closer to the Sun when our solar system was forming. Subsequent observations and careful analysis eventually confirmed this composition, strongly indicating that 2004 EW95 had been formed in the asteroid belt, not the Kuiper belt.

Launched by planets on the loose

This then raises the question of how this particular asteroid would have ended up so far from home, although that’s a question astronomers are happy to answer. Multiple models of the formation of our solar system include a period of time when the gas giant planets, like Saturn and Jupiter, were not in stable orbits around the Sun. The extreme mass and therefore gravity of these planets would have shoved and smashed smaller objects around them, possibly even clearing the inner solar system of many of the asteroids that were once closer to the Sun. If these models were true, it would be likely that some objects would have been launched by the gas giants’ gravity into deeper space. So the likely relocation of 2004 EW95 in the Kuiper belt is the first direct evidence to support these models.

Since Jupiter, Saturn and Uranus now have more stable orbits, 2004 EW95 probably won’t get pulled back to the asteroid belt any time soon. However, it may not be too lonely (do asteroids get lonely?) as astronomers have spotted other rocks that probably immigrated to the Kuiper belt before. However, the size, distance and darkness make confirming an asteroid’s composition difficult, which is why 2004 EW95 is the first time we’ve been able to more thoroughly vet what one of these lost rocks was made of.

Source: Exiled asteroid discovered in outer reaches of solar system, EurekAlert!

On May 8th, 2018 we learned about

Astronomers make sense of how stars like our Sun will glow when they eventually go to pieces

My five-year-old still struggles with idea that his older sister will someday want to live on her own (or that he might!), but he has seemed to finally come to terms with the fact that the Sun will eventually destroy the Earth. He’s certainly not the only kid I’ve met who has had to really grapple with this idea; obviously the Sun is supposed to always be up there in the sky keeping us warm, not tearing itself apart before collapsing into a smaller star in five billion years. It’s a lot to take in, but kids aren’t alone in wondering about this scenario. In fact, astronomers have only recently made sense of some aspects of our Sun’s eventual demise, since the models we had to explain a star’s life cycle didn’t always match what was being observed in space.

Shattered, but sparkling, stars

As a star begins to run out of fuel for its continuous chain of fusion reactions, one of the more dramatic steps of its decline is to become a planetary nebula. This process involves a star ejecting as much as half its mass into space in the form of gas and dust, leaving a smaller core behind. That core, as my third grader was happy to inform me, will then be a white dwarf, making for a significantly chillier solar system. However, the precise nature of the ejected gas and dust is what had astronomers scratching their heads, because they all seem to be too uniformly bright when we see planetary nebulae in other solar systems.

While our own Sun thankfully has a lot of life left in it, we have found planetary nebulae in other solar systems in other galaxies. For a period of around ten thousand years, they emit enough light to be detected, although those light levels oddly don’t vary all that much. According to our calculations, smaller stars should become smaller, dimmer planetary nebulae, but that wasn’t what astronomers were observing. Instead, the light was so consistently bright from these ejected debris fields that we could use the measured light levels to estimate how far away a galaxy was. So why weren’t older, smaller stars as dim as we thought they should be?

Too small to shine

The answer seems to be that, in a way, we were actually over-estimating smaller stars’ brightness. It’s not that lower mass stars are emitting too much light, but that they actually don’t emit much light at all. The bright lights we were seeing were all coming from planetary nebulae over a minimum mass, which is why they were all emitted a minimum amount of light. The truly petite planetary nebulae never got bright enough to see, even accounting for newer understandings of how quickly the ejected debris can heat up. In short, the glow of a planetary nebulae has a minimum mass threshold to emit a detectable amount of light.

As it turns out, that minimum mass seems to be just around the size of our own Sun. If our Sun were just a few percent smaller, its transition into a planetary nebula would be a much dimmer affair. For better or for worse, our Sun’s collapse will be a big enough event to be observed from distant galaxies.


My kids asked: Would people be able to move to Jupiter to be safe?

Well, Jupiter probably wouldn’t work as a gas giant, but what about a moon like Europa? That may actually be too close to the Sun as well, although the issue would arise before we have a planetary nebulae. In around four billion years, our Sun is expected to start expanding into a red giant, vaporizing all the planets up to the Earth in the process. Technically, this will also mean that the Sun’s surface will cool a bit, but even then Mars and Jupiter would both be too close to have habitable temperatures. The moons of Saturn, Uranus or Neptune might work though, assuming life forms in a few billion years could make that trip but not handle the journey to a younger star altogether.

Source: What will happen when our sun dies? by University of Manchester, Science Daily

On April 25th, 2018 we learned about

Mini model meteorites demonstrate how well hot rocks can deliver water to dry planets

While we live on an impressively wet planet today, the Earth probably didn’t start out with our lush collections of rivers, lakes and oceans. With no obvious way for the planet’s iron and other minerals to have spontaneously transmuted into H2O billions of years ago, scientists have long suspected that our water was instead delivered from space via icy objects like comets. Further research found that our water looked more like the water found on icy asteroids like Ceres, which was clearly abundant in the asteroid belt, but it still posed a problem. Asteroids tend to burn and explode a lot when they get too close to the Earth, so how would any of their water survived long enough to help soak our planet?

Proxy-asteroid projectiles

With no asteroids or spare planets at their disposal, researchers from Brown University turned to the Vertical Gun Range at the NASA Ames Research Center to simulate icy impactors. Marble-sized projectiles were fabricated to match the composition of carbonaceous chondrites, or meteorites suspected of being formed in ancient, icy asteroids. The miniature proxy-meteors were then fired at a chunk of dry pumice powder, which served as their stand-in for the once-parched surface of the Earth.

The small impactors hit their targets at more than 11,000 miles-per-hour, releasing heat and an impressive amount of debris in all directions. As with real asteroid impacts, enough heat was generated in these collisions to outright destroy some material, including some of the water ice. However, some of the mineral content also melted, which weirdly enough was key to some of the water’s survival. Because the rock melted and re-cooled so quickly, it could capture some of the water inside the resulting glass, keeping it “safe” from vaporizing. Additional water was similarly captured by flying breccias— random debris thrown and heated by the impact that were hot enough to become “welded” together.

Making sense of previous predictions

This experiment not only helps explain some of the water on Earth, but also some of the confusing H2O around the solar system. Since previous estimates found that asteroid impacts should vaporize water, researchers had a hard time explaining the presence of water in impact craters on places like the Moon and Mercury. The physical test proved that those estimates hadn’t captured the full complexity of such an impact, and that delivering water via screamingly-fast hunks of icy rock is apparently more practical than you might think.


My five-year-old asked: What does the Vertical Gun Range look like?

“Gun” may be a misleading term here, because the equipment in question doesn’t really look much like pistol, rifle or cannon, at least outside science fiction. A large barrel launches a projectile into an enclosed, reinforced chamber. That chamber is outfitted with a number of sensors and cameras so that researchers can learn more details about the behavior of whatever collision is being studied. NASA has more on the AVGR in this handy PDF.

Source: Projectile cannon experiments show how asteroids can deliver water by Brown University, Phys.org

On April 19th, 2018 we learned about

A meteorite delivered diamonds carrying traces of our solar system’s less successful protoplanets

Building a planet out of dust isn’t easy. Sure, the recipe basically requires innate forces like gravity to do a lot of the work, but not every clump of debris successfully forms into a durable planet. Those first steps are called protoplanets, and while we’ve seen them around other stars, we’ve only recently found evidence of the protoplanets that helped build the planets in our own solar system.

Learning from dirty diamonds

The evidence found in diamonds carried to Earth in a meteorite that struck the Earth in 2008. Those diamonds carried small bits of other metals and minerals that were present when the diamond was formed. The composition and structure of this extra material, known as inclusions, can tell us a lot about the conditions that created the diamond.

In this case, the structure of the diamond indicates that it was formed as an achondrite— a rock formed in an object large and hot enough to create a metallic core inside a layer of rock. That could include very large asteroids, but other features of these diamonds make it more likely to have been formed in a larger protoplanet instead. The inclusions also show that these diamonds were formed under at least 20 gigapascals of pressure, well beyond diamond’s normal elastic breaking point. With that reference point, geophysicists can estimate that the protoplanet that created these diamonds was somewhere between the size of Mercury and Mars.

This may seem like a crazy amount of information to infer from a single space rock, but we’ve been reading history from diamonds here on Earth for years. Actually, we’ve been getting history out of the Earth, as diamonds are known to carry information about the formation and movement of materials deep under the Earth’s crust, carrying them to the surface like shiny time-capsules, including deposits of water over a 100 miles below the Earth’s surface.

Potential planets from the past

None of this suggests that we have a new planet forming next door. Simulations of our solar system’s formation predicted that multiple protoplanets formed within 10 million years of our Sun’s formation. While at least eight of those objects managed to survive long enough to become the planets we know today, the diamonds found in the 2008 meteorite are probably just pieces of some of the other protoplanets that were destroyed in collisions in a more crowded solar system.

 

Source: Diamonds in Meteorite May Hail from Our Ancient Solar System by Doris Elin Slazar, Space.com

On April 8th, 2018 we learned about

Investigating the likelyhood of microbial life existing in Venus’ upper atmosphere

You don’t want to live on Venus, but there are a lot of places you don’t want to live on Earth as well. Hydrothermal vents, acidic lakes and the cold reaches of the upper atmosphere are all pretty inhospitable plants and animals alike, but that doesn’t mean that they’re not home to life. As we look closer at the nastiest, hottest, most acidic bits of real estate on the planet, the more bacteria we find adapted to these extreme conditions. This has scientists excited, because if life is in the market for these spots on Earth, there’s a small but real chance that it might love what’s available on Venus.

Too hostile to be a home?

Don’t feel bad if you’re not familiar with the brutal conditions on Venus. It’s such a rough part of the solar system that the probes we’ve sent to the second planet generally don’t last very long; the Soviet Venera 13 set records by surviving for a whole 127 minutes. Aside from a few photographs, we have been able to determine that the surface of Venus gets up to 863º Fahrenheit, and the air pressure is between 17 to 20 times as strong as on Earth. With the wind and acidic chemistry in the air, even the heartiest Earth-born bacteria couldn’t survive on Venus’ surface. On the other hand, the upper atmosphere may be just gentle enough to allow microbes a small chance at survival.

The upper layers of clouds on Venus are reflective and acidic, made mostly of carbon dioxide, water and sulfuric acid. It doesn’t sound pleasant, but the temperatures are low enough that life as we know it could exist there. What’s more, the sulfuric acid may even be a byproduct of microbial metabolisms– species on Earth are already known to do that (often with unfortunate consequences for their surroundings.) What’s more, observations from space have noted unexplained dark patches in these Venusian clouds, most of which are within the size range of bacteria on our own planet. This isn’t proof of alien life, but since we’ve never tested specifically for organic chemistry in Venus’ upper atmosphere, we can’t rule out the possibility of microbes without getting more information.

While spacecraft are circling Venus in space, none of them are in a position to sample these dark spots in the planet’s clouds. One proposed design is the Venus Atmospheric Maneuverable Platform (VAMP), which would fly through caustic clouds for as long as a year. With the right set of sensors, like mass spectrometers and microscopes to examine airborne samples, researchers would be in a better position to identify potentially organic materials in the atmosphere.

Originating from the past, or other planets

As hard as it is to picture life on such a harsh planet, there are actually a few possibilities for how bacteria could end up there. The first option is that the bacteria migrated from the ground, since Venus was probably a nice place 2.9 billion years ago. At that time, there’s a fair chance that the planet was a tepid 51° Fahrenheit on the surface, giving microbes a chance to evolve before the upper atmosphere was the only place left to go. Alternatively, the clouds could have been seeded by a place like Earth, as high-speed dust moving through the solar system has been calculated to be able to knock microbes in our atmosphere clear into space. So if life didn’t arise on Venus on its own, there’s still a chance that other Earthlings simply beat us to the punch of traveling to another planet.

Source: Is there life adrift in the clouds of Venus? by University of Wisconsin-Madison, Science Daily

On April 3rd, 2018 we learned about

Strangely slow galaxy attributed to missing dark matter

Some missing dark matter may help confirm that this invisible substance exists. Dark matter is as-of-yet theoretical form of matter that doesn’t interact with light as we know it, making it invisible or dark to our various probes and sensors studying the universe. It does seem to interact with gravity like other matter does though, and so most of our ideas about it come from watching how normal objects move and react to the pull of something that’s otherwise undetectable. Of course, since as much as 80 percent of the mass of the universe is actually dark, studying what is does and doesn’t do isn’t easy.

Luckily, dark matter doesn’t seem to be equally distributed. Galaxy NGC 1052–DF2, a cluster of stars 65 million light-years away from Earth, may lack dark matter entirely. NGC 1052–DF2 looks pretty normal at any given moment, but the over time the motion of some bundles of stars, called globular clusters, has turned out to be too slow. For the amount of mass we can see, the galaxy should have around 60 billion times our own Sun’s mass in dark matter. The total mass of normal and dark matter would then require the globular clusters to move much faster than they’ve been observed. The orbital speeds that have been seen only make sense if there’s no dark matter there at all.

How could the dark matter be missing?

This is weird, to say the least. Galaxies are thought to form around the gravitational well created by clumps of dark matter, so this finding raises questions about how NGC 1052–DF2 ever came together in the first place. One possibility is that the dark matter has been stolen by some of its neighbors. Some galaxies have been found with extra dark matter, and so there’s a chance that NGC 1052–DF2 lost its invisible mass to the stronger gravitational pull of another galaxy.

The last option is that there was never dark matter in NGC 1052–DF2, or anywhere else for that matter. Some researchers suggest that the best way to make sense of the movement of large galaxies is with modified Newtonian dynamics, or MOND. In this model, the physics we’re used to just aren’t correct on the scale of a galaxy, and thus need adjusting so that they make sense with what we’ve observed. However, the weird speeds of NGC 1052–DF2 are strengthening doubts about MOND, since even modified dynamics should be consistent in every galaxy. It’s then easier to imagine one weird galaxy missing its dark matter than figuring out some other caveat to explain why the math behind MOND would need further adjustments in just this case.

Source: Dark matter is MIA in this strange galaxy by Emily Conover, Science News

On March 29th, 2018 we learned about

Kepler telescope finds that short-lived supernovae are likely the result of a dispersed layer of glowing debris

Exploding stars should be easy to spot. Aside from the release of as much energy as our Sun will produce in its entire lifetime, these massive explosions light up their surroundings for weeks as all the nearby debris cools down over time. If you somehow did miss spotting a particular supernova, you might not have to wait long for the next one, as one star is probably exploding every second somewhere in the universe. Despite all this, astronomers were still having trouble with a particular kind of explosion, which broke some of these rules and would instead flicker brightly for just a couple of days then go dark. Unless we knew exactly where to expect such an event, they were often over before any telescope could find them.

Finally seeing a star’s final flicker

The mystery of Fast-Evolving Luminous Transient (FELT) supernovae has been nagging astronomers for over a decade. Many hypotheses were suggested, ranging from gamma-ray bursts to magnetar-boosted supernovae, but every idea was hard to test against such fleeting opportunities to actually observe the event in the first place. Even in cases were a telescope did capture the first flash of light from a FELT, subsequent observations usually wouldn’t be taken until 24 hours later, missing a lot of important details about how these flashes take place.

Enter the Kepler space telescope. This spacecraft was originally designed to hunt for exoplanets by detecting small, short changes in light levels around distant stars, making it a great way to gather data on a FELT-friendly timescale. Instead of detecting small dips in a star’s light as exoplanets pass in front of them, Kepler was able to observe the bursts and quick decay of light from FELT supernovae, getting a snapshot of data every 30 minutes. This allowed astronomers to discard many of their hypotheses about FELT explosions, leading them to a new model that’s apparently a bit more than a single explosion.

A glow from a globe of dust

Based on the details gathered by Kepler, researchers now believe FELT explosions get started before a star is really ready to blow up. As the start begins its final collapse, it may eject a layer of dense dust that ends up orbiting the star as a sort of shell. Once the star does finally pop, close to a year later in this case, its blast wave of kinetic energy hits the dust in the shell, causing it to quickly light up all at once. In these observations, the brightness peaked in a period of just over two days, making it fast even by FELT standards. Less energy will be emitted in that last burst, allowing the visible light to drop off much more quickly than in a “standard” star explosion.

There’s obviously more to learn about FELT supernovae, such as how the outer shell of material interacts with the core that will eventually burst altogether. Fortunately, the fact that the Kepler telescope was able to find this brief event while just looking at one small patch of sky suggests that these types of explosions aren’t horribly rare either. It will hopefully be relatively easy to collect more data and confirm more details about how these stars flicker before going dark forever.

 

Source: Kepler Solves Mystery of Fast and Furious Explosions by Armin Rest , Hubblesite

On March 18th, 2018 we learned about

Calculating what kind of push could prevent a large asteroid from colliding with the Earth

Kids supposedly want to know why the sky is blue, but that question doesn’t grip their imaginations like potentially being killed by an asteroid hitting the Earth. It’s not illogical, since knowing that giant dinosaurs were driven extinct by an asteroid strike 65 million years ago makes it clear that such an event is a severe and nearly hopeless scenario. Factor in how hard it is to explain the statistical unlikelihood that a world-ending asteroid would hit the Earth, and it’s easy to see how a kid might think that adults are weird for not worrying about suffering the same fate as the dinosaurs. Thankfully, some adults are thinking about rocks falling from space, and working out possible responses to larger asteroids that might be headed our way.

Bumping asteroids without breaking them

101955 Bennu is an 87-million-ton asteroid that passes by the Earth every six years. It’s close enough that we can track it with some certainty, and have realized that it does stand a chance of hitting our planet on September 25, 2135. At this point there’s only a 1 in 2,700 chance that it will actually collide with Earth, which is four-times lower than your odds of dying in a car crash in the next year, but it’s a good target to explore potential safety measures that could shield us from being hit.

With an object as large as Bennu, there’s already consensus that we need to nudge it, not blow it to pieces. Aside from the difficulty of really obliterating that much mass, exploding a large asteroid would probably just mean the Earth got hit by lots of smaller rocks instead of one big one. That’s arguably better nothing, but an early adjustment to the asteroid’s orbit would be preferable, and given enough time, a tad more practical.

Adjusting orbits with HAMMERs and explosions

To alter Bennu’s orbit, one proposal is to basically launch a large, Delta IV rocket at it, tipped with a 8.8-ton spacecraft called HAMMER (Hypervelocity Asteroid Mitigation Mission for Emergency Response vehicle). As you might guess, HAMMER would fly into an asteroid like Bennu to try to slow it down and alter its orbital path a small amount. If done early enough, even a small push can lead to big shifts in the asteroid’s trajectory years later. It’s a sensible plan until you work through all the math, at which point it becomes clear that 8.8 tons isn’t going push a big asteroid far enough on its own, even if they collide years in advance. One estimate found that 34 to 53 HAMMER spacecraft would be needed to move Bennu to a safer orbit if given a 10 year lead time. If the project started 25 years before 2135, the orbit could be sufficiently adjusted with only 7 to 11 spacecraft, although that still requires an enormous amount of resources with little room for error. Developing HAMMER spacecraft isn’t a totally lost cause though, as one such craft could probably divert a 295-foot asteroid if given a 10-year head start.

If HAMMER doesn’t look practical right now, an alternative idea is to deflect asteroids like Bennu with a nuclear explosion. Again, the goal wouldn’t be to destroy the rock, but to divert it before it gets to Earth. With that in mind, a warhead would be detonated near the incoming rock, hitting one side of the asteroid with radiation. That radiation could vaporize the surface of the asteroid, essentially turning that entire face into a giant, if gentle, thruster. As vaporized rock pushes off the asteroid, it would push Bennu in the opposite direction, hopefully nudging it over just enough to miss the Earth years later.

Planning for all the possibilities

Hopefully this will all be academic by 2135. As that date approaches, astronomers will track Bennu’s orbit and be able to refine their predictions about its eventual path. Even if it never intersects the Earth, figuring out responses is still worth while though. Bennu is one of 10,000 objects that NASA tracks at this point, but they can’t see everything. It’s possible that a ten-year head start to build a response will be all our planet gets, in which case these early planning exercises will save us all a bit of very precious time.

Source: Scientists design conceptual asteroid deflector and evaluate it against massive potential threat by Lawrence Livermore National Laboratory, Phys.org