On October 11th, 2018 we learned about

Moonmoons: scientists look at the likelyhood of moons of moons

Moons can be inert pieces of rock, hunks of ice or volcanically active. They can be caught in slow death spirals or potential homes to life. Atmospheres can be thick, thin or non-existent. Even size doesn’t matter all the much, as long as the moon is relatively small enough to be held by a planet’s gravitational pull. This is because the only real rules about being a moon are that the object is naturally occurring (ruling out the International Space Station, for instance) and that they orbit a planet specifically (ensuring that planets aren’t moons of their local stars). It all seems logical enough from our single-mooned planet, but since these satellites could potentially be large enough to trap objects in their own orbit, it raises questions about why we’ve defined moons like this, and if secondary moons of moons are even a possibility to consider.

Optimal orbits

Even with just a handful of planets, our solar system is still home to hundreds of moons. Making up the lack of moons around the inner planets, a gas giant like Jupiter has at least 78 moons in orbit. The more we look, the more we seem to find, indicating that a big planet doesn’t have a lot of trouble scooping up satellites. The lack of moons around those moons indicates that the latter relationship is much harder to maintain. This is essentially due to the limited range where a smaller object can fall into orbit around a moon without being pulled towards the larger planet nearby. Called the Hill sphere, this distance is highly dependent on the relative size and distance of the larger body in the equation, meaning the Earth’s smaller size and proximity to the Sun give our planet a smaller Hill sphere than Jupiter.

Even if an object does fall into a consistent orbit around a planet or moon, there’s also the issue of tidal forces. On Earth, the Moon ends up “pulling” more on the axis that is pointed at the Moon, which gives us high and low tides as the planet’s water essentially shifts around to always be aligned with the Moon. On a planet-wide scale, this results in internal friction and the release of heat, slowing the rotational speed of the objects in question. Over the course of millions of years, an orbiting object is then likely to be slowed enough to fall out of its orbit altogether. Combined with an already tight Hill sphere, this further reduces the odds of finding a moon of a moon.

Models for moonmoons

This isn’t to say that these moons are impossible. Researchers recently modeled a number of scenarios and believe that moons-of-moons are likely to eventually be found around planets in other solar systems (or even around some of the many moons of Jupiter and Saturn!) Naturally, if these objects are going to be found and studied, it would help to define them, starting with a name. Some people are advocating for terms like “sub-moons” or “mini-moons,” but a standout contender may actually be based on a weird meme about werewolf names: moonmoons. Moonmoons may not be the most descriptive term out there it certainly makes a yet-unseen form of space rock seem very endearing. Sometimes even science is subject to popularity contests (just ask Opisthoteuthis adorabilis).

Source: Can moons have moons? (Intermediate) by Sabrina Stierwalt, Ask an Astronomer

On August 21st, 2018 we learned about

The Chandrayaan-1 spacecraft confirms relatively accessible supplies of ice on the Moon’s surface

If humans get thirsty on their way to Mars, it looks like we’ll be able to stop for drinks on our own Moon. Despite its reputation for being nothing more than a dusty target for asteroid strikes, researchers are solidly convinced that the Moon’s north and south poles are both home to water ice. If there proves to be a significant amount of frozen water, it could be a crucial resource for humans or spacecraft spending time in space.

Cold craters as ice cube trays

While the Moon’s surface is generally a dry, inhospitable place, it’s actually fairly conceivable to find water ice at the north and south poles. The Moon rotates with hardly any tilt to its axis, only 1.54 degrees, compared to the Earth’s 23.5-degree tilt, so the north and south poles don’t experience seasonal changes in their exposure to the Sun. With the Sun never being “overhead” at these locations, deeper craters can cast constant shadows on their interiors, maintaining temperatures below -250 degrees Fahrenheit. At this time, it’s unknown if this water was originally delivered by an icy comet or some other means, but there’s a good chance that it has remained frozen in these craters for a very long time.

The origin of the water might be revealed once a physical sample can be acquired. For now, the ice has been identified by examining a number of features with the Moon Mineralogy Mapper (M3) instrument aboard the Chandrayaan-1 spacecraft. Even with the dust and darkness in these polar craters, the M3 was able to measure the reflectivity, infrared light absorption and other properties that all point to frozen H2O being on the Moon.

Accessible ice

There’s likely more ice buried deeper in the Moon, but these patches are exciting thanks to how close they are to the surface. Even though it likely has a lot of dirt mixed into it, it would still be accessible enough to be of use to humans or robots visiting the Moon in the future. Water is pretty heavy to get off the Earth, so any supplies of water for drinking, irrigating or even splitting to gain access to oxygen, would be a welcome resource for astronauts traveling outside low Earth orbit.

Source: Ice Confirmed at the Moon's Poles, Jet Propulsion Laboratory News

On August 15th, 2018 we learned about

The edge of our solar system is likely marked by light from particle collisions

My nine-year-old daughter can’t get over the fact that, as of now, we can’t detect any boundary to the universe. Sounding a bit like a mesmerized stoner, she rarely misses an opportunity to mention how much it blows her mind to try to imagine a borderless universe. So she’ll be either relieved or disappointed to learn that unlike the vast expanse of the entire universe, our solar system does have a border. What’s more, unlike the imaginary political borders humans draw on maps, our solar system’s edge is likely defined by a physical ‘wall’ of faintly-glowing hydrogen atoms.

The space filled by solar wind

This model is based on the idea that our Sun is constantly emitting not just light and heat, but charged particles as well. These high-speed protons, electrons and other ions that are blasted out of the Sun’s corona are collectively called solar wind. Solar wind isn’t emitted at a perfectly regular rate, but there’s enough of it being pushed out across the solar system that it’s almost like the Sun is inflating a large bubble from the inside.

That bubble is called the heliosphere, and seems to have a definable edge. 100 times further than the Earth is from the Sun, solar wind starts to encounter stray hydrogen atoms from outside the solar system. These neutral, interstellar atoms provide just a bit of resistance to the solar wind, and the two types of particles collide often enough to create a detectable amount of ultra-violet light. The meeting area between stray particles probably isn’t the most clear-cut boundary you might imagine, but the area where our Sun’s output meets objects from outer space should at least be directly observable.

Spotted by spacecraft

This light from the edge of the heliosphere, or heliopause, was first detected by the Voyager 1 spacecraft 30 years ago when that craft exited the solar system. Voyager 2 is seeing similar evidence, although it won’t actually cross the heliopause until 2030. The New Horizons spacecraft has started picking up traces of evidence that further support those observations, even though it’s still in the Kuiper belt.

The clearest proof of this model would be attainable when a spacecraft passes through the heliopause. Once on the other side, the ultraviolet light would immediately drop off, sitting squarely behind something like Voyager 2 as it continues to travel away from the Sun. Scientist note that this may not turn out to be the case, and that there may be an unknown source of ultraviolet light in the space beyond our solar system. However, with New Horizons backing up what has previously been found by Voyager 1 and 2, there is a strong likelihood that our Sun’s sphere of influence does a pretty good job of marking itself at the edge of the solar system.

Source: New Horizons may have seen a glow at the solar system’s edge by Lisa Grossman, Science News

On July 24th, 2018 we learned about

The Andromeda galaxy’s past and future growth is fueled by collisions with its cosmic kin

The Earth is currently flying around the Sun at around 70,000 miles-per-hour. The Sun is dragging our solar system through the Milky Way galaxy at around 450,000 miles-per-hour. The Milky Way, though composed of 150 to 250 billion different stars, is moving through a cluster of galaxies known as the Local Group at around 250,000 miles-per-hour. While there’s enough open space in space to allow our solar system room to maneuver, it seems like massive galaxies flying around would likely lead to some kind of collision. As it turns out, intuition is actually correct in this case, as researchers have calculated that nearby galaxies have recently crashed into each other in the not too distant past, and more collisions are expected in the future.

Andromeda’s acquisitions

The largest galaxy in the Local Group is Andromeda, which is estimated to be home to around a trillion stars. It wasn’t always that big though, as astronomers believe it has a long history of colliding with, and consuming, smaller galaxies in its path. Two billion years ago, it likely gobbled up what would have been the third-largest galaxy in the Local Group, the blandly-named M32 galaxy. Based on the age of the stars M32 stars still clustered together in Andromeda, researchers believe this collision was substantial. The jump in Andromeda’s celestial population was probably 20 times greater than any acquisitions in the past.

The simulations that lead to those figures match up well with other research teams’ observations, who also determined that Andromeda experienced a major collision between 1.8 and 3 billion years ago. The one major surprise in all this is how these collisions haven’t reshaped Andromeda more dramatically. Researchers expected that sucking up so many new stars would force Andromeda to adopt a smoother oval shape, but somehow the galaxy has retained a spiral, suggesting we don’t fully understand how these shapes are formed.

Milky Way Merger

If any humans are still around in four billion years, we may be able to find out more about that process from front row seats here on Earth. Andromeda’s next acquisition has been calculated to be our very own Milky Way galaxy. The Milky Way is the second-largest galaxy in the local group, and also a spiral galaxy, so the merger of these two massive galaxies should be quite impressive. As far as we know, it would be the largest restructuring the Milky Way has ever experienced, and will take around two billion years to complete.

If you have a distant relative still on this planet somehow, they’ll have plenty to watch, but not directly experience. The night sky will start to fill with stars from Andromeda’s core, and new stars will start popping up as various forms of mass merge together. Our solar system probably won’t be subject to any violent collisions though, instead being pushed towards the outer edge of the resulting “Milkomeda” galaxy. Granted, our own Sun will likely prevent this from being much of a concern as it should be expanding into an Earth-consuming red giant in the middle of all this, but at least the view from our solar system’s gas giants will be impressive.

Source: The Milky Way Had a Big Sibling Long Ago — And Andromeda Ate It by Mike Wall, Space.com

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