If Aliens Pilot Interstellar Object ‘Oumuamua, They Snubbed Us

The Seti Institute has monitored the object for radio transmissions, just in case it isn’t natural

We humans are a sensitive bunch. We keep pondering the question: “are we alone?” If we consider the answer is a “yes,” we then start having an existential crisis over our place in the universe. But if the answer is a “no,” a can of worms open and we start asking even more questions. “If they’re out there, where are they?” “Isn’t it a bit weird we haven’t heard from our extraterrestrial neighbors?” “Are they just too far away for us to communicate?” and my personal favorite: “Have they consciously decided not to communicate with us because we’re considered not worth communicating with?!” The Fermi Paradox is certainly as paradoxical as they come.

Cue a random object that cruised through our solar system last year. The interstellar visitor zoomed right into our interplanetary neighborhood, used the Sun’s gravity for a cheeky course correction, and then slingshotted itself back out into deep space. The whole thing happened so quickly that astronomers only noticed when the thing was speeding away from us at high speed.

Naturally, we took a hint from science fiction, remembering Arthur C. Clarke’s classic novel “Rendezvous With Rama” — when a huge artificial object appears from interstellar space and a brave team of astronauts are sent to intercept it. Might this interstellar object also be artificial? After all, it has an odd, tumbling shape (like a spinning cigar) and the precision at which it flew past us with the trajectory it did (using the Sun to change its direction and speed of travel) just feels artificial.

So, with the help of the SETI Institute’s Allen Telescope Array (ATA) in California, astronomers decided to take aim at the departing object from 
Nov. 23 and Dec. 5, 2017, when it was 170 million miles from Earth. The objective was to listen out for artificial radio transmissions that might reveal any kind of extraterrestrial intelligence. By monitoring frequencies from 1 to 10 GHz (at 100 MHz intervals), the ATA would be able to detect a very low powered onmidirectional transmitter, with a transmitting power as low as 10 Watts — the approximate equivalent to a citizen band radio.

According to the SETI study to be published in the February 2019 issue of Acta Astronautica, no signals were detected. Though this is obviously a blow for working out whether this thing was being actively piloted by some kind of intelligence, it does narrow down the true nature of the object, that has since been named ‘Oumuamua — which, in Hawaiian, roughly means “scout,” or “messenger.”

“We were looking for a signal that would prove that this object incorporates some technology — that it was of artificial origin,” said Gerry Harp, lead author of the study, in a SETI Institute statement. “We didn’t find any such emissions, despite a quite sensitive search. While our observations don’t conclusively rule out a non-natural origin for ‘Oumuamua, they constitute important data in assessing its likely makeup.”

Although this doesn’t prove ‘Oumuamua isn’t an alien spacecraft, it does put limits on the frequencies it could be transmitting on, if it is transmitting. And even if it isn’t transmitting, it doesn’t mean it’s not artificial. Could it be an ancient spacecraft that’s been sailing the interstellar seas for millions or billions of years, long after its intelligent occupants have died? Or long after its artificial intelligence has run out of energy? 

Or — and this is the big one — did it zoom through our solar system, aware of our presence, and not bother communicating with us? If that scenario played out, we need to re-open that can o’ worms and try to understand where we stand in the universal ecosystem of competing intelligences. Perhaps we are the cosmic equivalent of an ant colony; our intelligence just isn’t worth the time when compared with the unimaginable alien intelligences that have the technology to send ‘Oumuamuas to probe distant star systems for life.

Alas, it’s probably a case of Occam’s razor, where the simplest explanation is most likely the correct one: ‘Oumuamua is probably a strange-looking asteroid or ancient comet that was randomly shot at us by some distant star system and astronomers were lucky to detect it. But, we still need to ponder the least likely explanations, you just never know…

Voyager 2 Has Left the (Interplanetary) Building

The NASA probe was launched in 1977 and has now joined its twin, Voyager 1, to begin a new chapter of interstellar discovery

Both Voyager 1 and 2 are sampling particles from the interstellar medium, becoming humanity’s furthest-flung missions into deep space [NASA/JPL-Caltech]

Carolyn Porco, planetary scientist and lead of the NASA Cassini mission imaging team, probably said it best:

Voyager 1 made us an interstellar species; 6 yrs later, Voyager 2 makes it look easy. While these are historic, soul-stirring achievements, I am most happy right now that Ed Stone, the best Project Scientist who ever lived, lived to see this moment. 

via Twitter

It can be easy to lump today’s announcement about Voyager 2 entering interstellar space as “simply” another magnificent science achievement for NASA — but that would be too narrow; the Voyager spacecraft have become so much more. They represent humanity at our best; our will to explore, our need to push boundaries, our excitement for expanding the human experience far beyond terrestrial shores. They also act as a means to understand the sheer scale of our solar system. And what better way to measure that scale than with a human life. 

Ed Stone started working on the Voyager Program in 1972 as a project scientist. Now, at 82 years old, he’s still working on the Voyagers nearly half a century later as they continue to send back data from the frontier beyond our solar system. When we start measuring space missions in half-centuries, or missions that have lasted entire careers, it becomes clear how far we’ve come. Not only does NASA build really tough space robots that surpass expectations routinely, returning new discoveries and revelations about the universe that surrounds us, the Voyagers have become a monument to the essence of being human, something with which Stone would probably agree.

Although most of the instruments aboard the Voyagers are no longer functional, both missions are still returning data from the shores of the interstellar ocean and, on Nov. 5, mission controllers noticed that one of Voyager 2’s instruments, the Plasma Science Experiment (PSE), had detected a rapid change in its surrounding environment. Used to being immersed the comparatively warm and tenuous solar wind flowing past it, its plasma measurements detected a change. The spacecraft had passed into a region of space where the plasma was now denser and cooler. Three other particle experiments also detected a dramatic change; solar wind particle counts were down, but cosmic ray counts precipitously increased. Voyager 1’s PSE failed in 1980, so couldn’t measure this boundary when it entered interstellar space in 2012, so Voyager 2 is adding more detail about what we can expect happens when a spacecraft travels from the heliosphere, through the heliopause and into interstellar space. 

[NASA/JPL-Caltech]

“There is still a lot to learn about the region of interstellar space immediately beyond the heliopause,” said Stone in a NASA statement.

The heliosphere can be imagined as a vast magnetized bubble that is generated by the Sun. This bubble is inflated by the solar wind, a persistent stream of solar particles that ebb and flow with the Sun’s 11-year cycle. When the Sun is at its most active, the bubble expands; at its least active, it contracts. This dynamic solar sphere of influence affects the flux of high-energy cosmic rays entering the inner solar system, but the physics at this enigmatic boundary is poorly understood. With the help of the Voyagers, however, we’re getting an in-situ feel for the plasma environment at the boundary of where the Sun’s magnetism hits the interstellar medium.

To achieve this, however, we had to rely on two spacecraft that were launched before I was born, in 1977. Voyager 2 is now 11 billion miles away (Voyager 1 is further away, at nearly 14 billion miles) and it took the probe 41 years just to reach our interstellar doorstep. Neither Voyagers have “left” the solar system, not by a long shot. The gravitational boundary of the solar system is thought to lie some 100,000 AU (astronomical units, where one AU is the average distance from the Earth to the Sun), the outermost limit to the Oort Cloud — a region surrounding the solar system that contains countless billions of icy objects, some of which become the long-period comets that intermittently careen through the inner solar system. Voyager 2 is barely 120 AU from Earth, so as you can see, it has a long way to go (probably another 30,000 years) before it really leaves the solar system — despite what the BBC tells us.

So, tonight, as we ponder our existence on this tiny pale blue dot, look up and think of the two space robot pioneers that are still returning valuable data despite being in deep space for over four decades. I hope their legacy lives on well beyond the life of their radioactive generators, and that the next interstellar spacecraft (no pressure, New Horizons) lives as long, if not longer, than the Voyagers.

Read more about today’s news in my article for HowStuffWorks.com.

  

Did a Solar Storm Detonate Dozens of Vietnam War Mines?

Some 25 underwater mines mysteriously exploded in the summer of 1972. A newly declassified report points its finger at a surprising culprit: the sun.

[NASA/SDO]

Something very strange happened on Aug. 4, 1972 in the waters near Vietnam. Dozens of undersea mines detonated for seemingly no reason. The matter was classified, as was a report trying to get to the bottom of what happened. Initial hypotheses focused on a malfunctioning self-destruct feature meant to prevent lost mines from posing an underwater hazard for decades after hostilities were over, but there was no corroborating evidence. Soviet subs might have accounted for one or two, but not systematic detonations across the whole minefield, not to mention their defensive countermeasures.

But one of the suggestions seemed to very neatly explain the observed phenomenon. The mines were magnetic, meaning that they reacted to the natural magnetism of metals in ships’ hulls and the changes in the strengths of their magnetic fields as those ships approached. It was an old, reliable technology and it would’ve taken a massive magnetic event to have set them off. And wouldn’t you know it, some of the most intense solar activity on record happened in that exact time frame, causing numerous power surges and telegraph outages across North America.

On the day Navy aircraft saw the mines go off, the sun erupted in what’s known as an X-class flare, a burst of energy more than 10,000 times more powerful than the high end of typical solar emissions. With the path to Earth cleared by supercharged solar winds, the resulting coronal mass ejection hit Earth in just 14.6 hours instead of the typical three days and caused massive magnetic and electrical disruptions in the atmosphere, quite possibly powerful enough to set off detectors on the underwater mines off the coast of Hon La Port as the plasma slammed into our planet.

So, case closed? Not exactly. We measure the intensity of the disruption in the Earth’s magnetic field caused by solar storms in negative nTs, or nano-Teslas. By itself, a nano-Tesla isn’t much. Your run of the mill fridge magnet is a million times stronger, although it’s only spread over tens of square centimeters, instead of millions of square kilometers like the fraction of a coronal mass ejection that hits Earth and lingers in the upper layers of the atmosphere. In 2003, a massive flare hit us with a magnetic disruption measuring almost -400 nT without melting anything down, although it did cause problems with air traffic.

By comparison, the ejection in 1972 measured a third of that at just -125 nT. Was it really strong enough to set off underwater mines? We’ll probably never know for sure, but it’s still entirely possible. Over the decades, we’ve learned much more about solar storms and what they can do, developed better shielding and early warning systems, more sophisticated equipment, and unwittingly created a shield of radio emissions to reroute charged particles from Earth. It’s quite plausible that older, less insulated technology was more sensitive to major solar storms and the trigger mechanisms for those mines were just one example.

[This article originally appeared on World of Weird Things]

Water Could Kill Life On Mars

A view from the Viking 1 deck, showing trenches its robotic arm dug out to acquire samples for testing [NASA/JPL-Caltech/Roel van der Hoorn]

When rains came to one of the driest places on Earth, an unprecedented mass extinction ensued.

The assumption was that this rainfall would turn this remote region of the Atacama Desert in Chile into a wondrous, floral haven — dormant seeds hidden in the parched landscape would suddenly awake, triggered by the “life-giving” substance they hadn’t seen for centuries — but it instead decimated over three quarters of the native bacterial life, microbes that shun water in favor of the nitrogen-rich compounds the region has locked in its dry soil.

In other words, death fell from the skies.

“We were hoping for majestic blooms and deserts springing to life. Instead, we learned the contrary, as we found that rain in the hyperarid core of the Atacama Desert caused a massive extinction of most of the indigenous microbial species there,” said astrobiologist Alberto Fairen, who works at Cornell Cornell University and the Centro de Astrobiología, Madrid. Fairien is co-author of a new study published in Nature’s Scientific Reports.

“The hyperdry soils before the rains were inhabited by up to 16 different, ancient microbe species. After it rained, there were only two to four microbe species found in the lagoons,” he added in a statement. “The extinction event was massive.”

El Valle de la Luna (Valley of the Moon) near San Pedro de Atacama looks very Mars-like [photo taken during #MeetESO in 2016, Ian O’Neill]

Climate models suggest that these rains shouldn’t hit the core regions of Atacama more than once every century, though there is little evidence of rainfall for at least 500 years. Because of the changing climate over the Pacific Ocean, however, modern weather patterns have shifted, causing the weird rain events of March 25 and Aug. 9, 2015. It also rained more recently, on June 7, 2017. Besides being yet another reminder about how climate change impacts some of the most delicate ecosystems on our planet, this new research could have some surprise implications for our search for life on Mars.

Over forty years ago, NASA carried out a profound experiment on the Martian surface: the Viking 1 and 2 landers had instruments on board that would explicitly search for life. After scooping Mars regolith samples into their chemical labs and adding a nutrient-rich water mix, one test detected a sudden release of carbon dioxide laced with carbon-14, a radioisotope that was added to the mix. This result alone pointed to signs that Martian microbes in the regolith could be metabolizing the mixture, belching out the CO2.

Alas, the result couldn’t be replicated and other tests threw negative results for biological activity. Scientists have suggested that this false positive was caused by inorganic reactions, especially as, in 2008, NASA’s Phoenix Mars lander discovered toxic and highly reactive perchlorates is likely common all over Mars. Since Viking, no other mission has attempted a direct search for life on Mars and the missions since have focused on seeking out water and past habitable environments rather than directly testing for Mars germs living on modern Mars.

With this in mind, the new Atacama microbe study could shed some light on the Viking tests. Though the out-gassing result was likely a false positive, even if all the samples collected by the two landers contained microscopic Martians, the addition of the liquid mix may well have sterilized the samples — the sudden addition of a large quantity of water is no friend to microbial life that has adapted to such an arid environment.

“Our results show for the first time that providing suddenly large amounts of water to microorganisms — exquisitely adapted to extract meager and elusive moisture from the most hyperdry environments — will kill them from osmotic shock,” said Fairen.

Another interesting twist to this research is that NASA’s Mars rover Curiosity discovered nitrate-rich deposits in the ancient lakebed in Gale Crater. These deposits might provide sustenance to Mars bacteria (and may be a byproduct of their metabolic activity), like their interplanetary alien cousins in Atacama.

As water-loving organisms, humans have traditionally assumed life elsewhere will bare similar traits to life as we know it. But as this study shows, some life on Earth can appear quite alien; the mass extinction event in the high deserts of Chile could teach us about how to (and how not to) seek out microbes on other planets.

Source: Cornell University

Hitching a Ride on an ‘Evolving Asteroid’ to Travel to the Stars

evolvingaste
The interstellar asteroid spaceship concept that would contain all the resources required to maintain a generations of star travelers (Nils Faber & Angelo Vermeulen)

When ʻOumuamua visited our solar system last year, the world’s collective interest (and imagination) was firing on all cylinders. Despite astronomers’ insistence that asteroids from other star systems likely zip through the solar system all the time (and the reason why we spotted this one is because our survey telescopes are getting better), there was that nagging sci-fi possibility that ʻOumuamua wasn’t a natural event; perhaps it was an interstellar spaceship piloted by (or at least once piloted by) some kind of extraterrestrial — “Rendezvous With Rama“-esque — intelligence. Alas, any evidence for this possibility has not been forthcoming despite the multifaceted observation campaigns that followed the interstellar vagabond’s dazzling discovery.

Still, I ponder that interstellar visitor. It’s not that I think it’s piloted by aliens, though that would be awesome, I’m more interested in the possibilities such objects could provide humanity in the future. But let’s put ʻOumuamua to one side for now and discuss a pretty nifty project that’s currently in the works and how I think it could make use of asteroids from other stars.

Asteroid Starships Ahoy!

As recently announced by the European Space Agency, researchers at Delft University of Technology, Netherlands, are designing a starship. But this isn’t your run-of-the-mill solar sail or “warpship.” The TU Delft Starship Team, or DSTART, aims to bring together many science disciplines to begin the ground-work for constructing an interstellar vehicle hollowed out of an asteroid.

Obviously, this is a long-term goal; humanity is currently having a hard enough time becoming a multiplanetary species, let alone a multistellar species. But from projects like these, new technologies may be developed to solve big problems and those technologies may have novel applications for society today. Central to ESA’s role in the project is an exciting regenerative life-support technology that is inspired by nature, a technology that could reap huge benefits not only for our future hypothetical interstellar space fliers.

Called the MELiSSA (Micro-Ecological Life Support System Alternative) program, scientists are developing a system that mimics aquatic ecosystems on Earth. A MELiSSA pilot plant in Barcelona is capable of keeping rat “crews” alive for months at a time inside an airtight habitat. Inside the habitat is a multi-compartment loop with a “bioreactor” at its core, which consists of algae that produces oxygen (useful for keeping the rats breathing) while scrubbing the air of carbon dioxide (which the rats exhale). The bioreactor was recently tested aboard the International Space Station, demonstrating that the system could be applied to a microgravity environment.

Disclaimer: Space Is Really Big

Assuming that humanity isn’t going to discover faster-than-light (FTL) travel any time soon, we’re pretty much stuck with very pedestrian sub-light-speed travel times to the nearest stars. Even if we assume some sensible iterative developments in propulsion technologies, the most optimistic projections in travel time to the stars is many decades to several centuries. While this is a drag for our biological selves, other research groups have shown that robotic (un-crewed) missions could be done now — after all, Voyager 1 is currently chalking up some mileage in interstellar space and that spacecraft was launched in the 1970’s! But here’s the kicker: Voyager 1 is slow (even if it’s the fastest and only interstellar vehicle humanity has built to date). If Voyager 1 was aimed at our closest star Proxima Centauri (which it’s not), it would take tens of thousands of years to get there.

But say if we could send a faster probe into interstellar space? Projects like Icarus Interstellar and Breakthrough Starshot are approaching this challenge with different solutions, using technology we have today (or technologies that will likely be available pretty soon) to get that travel time down to less than one hundred years.

One… hundred… years.

Sending robots to other stars is hard and it would take generations of scientists to see an interstellar mission through from launch to arrival — which is an interesting situation to ponder. But add human travelers to the mix? The problems just multiplied.

The idea of “worldships” (or generation ships) have been around for many years; basically vast self-sustaining spaceships that allow their passengers to live out their lives and pass on their knowledge (and mission) to the next generation. These ships would have to be massive and contain everything that each generation needs. It’s hard to comprehend what that starship would look like, though DSTART’s concept of hollowing out an asteroid to convert it into an interstellar vehicle doesn’t sound so outlandish. To hollow out an asteroid and bootstrap a self-sustaining society inside, however, is a headache. Granted, DSTART isn’t saying that they are actually going to build this thing (their project website even states: “DSTART is not developing hardware, nor is it building an actual spacecraft”), but they do assume some magic is going to have to happen before it’s even a remote possibility — such as transformative developments in nanotechnology, for example. The life-support system, however, would need to be inspired by nature, so ESA and DSTART scientists are going to continue to help develop this technology for self-sustaining, long-duration missions, though not necessarily for a massive interstellar spaceship.

Hyperbolic Space Rocks, Batman!

Though interesting, my reservation about the whole thing is simple: even if we did build an asteroid spaceship, how the heck would we accelerate the thing? This asteroid would have to be big and probably picked out of the asteroid belt. The energy required to move it would be extreme; to propel it clear of the sun’s gravity (potentially via a series of gravitational assists of other planets) could rip it apart.

So, back to ʻOumuamua.

The reason why astronomers knew ʻOumuamua wasn’t from ’round these parts was that it was moving really, really fast and on a hyperbolic trajectory. It basically barreled into our inner star system, swung off our sun’s gravitational field and slingshotted itself back toward the interstellar abyss. So, could these interstellar asteroids, which astronomers estimate are not uncommon occurrences, be used in the future as vehicles to escape our sun’s gravitational domain?

Assuming a little more science fiction magic, we could have extremely advanced survey telescopes tasked with finding and characterizing hyperbolic asteroids that could spot them coming with years of notice. Then, we could send our wannabe interstellar explorers via rendezvous spacecraft capable of accelerating to great speeds to these asteroids with all the technology they’d need to land on and convert the asteroid into an interstellar spaceship. The momentum that these asteroids would have, because they’re not gravitationally bound to the sun, could be used as the oomph to achieve escape velocity and, once setting up home on the rock, propulsion equipment would be constructed to further accelerate and, perhaps, steer it to a distant target.

If anything, it’s a fun idea for a sci-fi story.

I get really excited about projects like DSTART; they push the limits of human ingenuity and force us to find answers to seemingly insurmountable challenges. Inevitably, these answers can fuel new ideas and inspire younger generations to be bolder and braver. And when these projects start partnering with space agencies to develop existing tech, who knows where they will lead.

Proxima Centauri Unleashes ‘Doomsday’ Flare

Proxima b just got roasted.

flarestar
Proxima b weather report: Sunny with the chance of a flare of doom (NASA)

Having a bad day? Well, spare a thought for any hypothetical aliens living on Proxima b.

Proxima Centauri is a small, dim M dwarf—commonly known as a red dwarf—located approximately 4.2 light-years away. Over the last couple of years, this diminutive star has spent a lot of time in the headlines after the discovery of a small rocky world, called Proxima b, inside the star’s habitable zone.

With the knowledge that there’s a potentially temperate world on our cosmic doorstep, speculation started to fly that this exoplanet could become a future interstellar destination for humanity or that it’s not just a “habitable” world, perhaps it’s inhabited, too.

Putting aside the fact that we have no idea whether this interesting exoplanet possesses water of any kind, let alone if it even has an atmosphere (two pretty important ingredients for life as we know it), it is certainly an incredible find. But there are some caveats to Proxima b’s habitability and the main one is the unpredictability of its star.

The problem with red dwarfs is that they are angry little stars. In fact, they have long been known as “flare stars” as, well, they produce flares. What they lack in energy output they certainly make up for in explosions. Really, really big explosions.

Last March, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile detected a cataclysmic stellar flare erupting from Proxima Centauri, and this thing put anything our Sun can produce to shame.

“March 24, 2017, was no ordinary day for Proxima Cen,” said astronomer Meredith MacGregor, of the Carnegie Institution for Science in Washington D.C., in a statement.

Over just ten seconds on that special day, a powerful flare boosted Proxima Centauri’s brightness by over 1,000 times greater than normal. This mega-flare event was preceded by a smaller flare event and both flares occurred over a two minute period.

nrao18cb03b
The brightness of Proxima Centauri as observed by ALMA over the two minutes of the event on March 24, 2017 (Meredith MacGregor, Carnegie)

Although astronomers have little idea where Proxima b was in relation to the flaring site, it would have undoubtedly received one hell of a radiation dose from the eruption.

“It’s likely that Proxima b was blasted by high energy radiation during this flare,” said MacGregor. “Over the billions of years since Proxima b formed, flares like this one could have evaporated any atmosphere or ocean and sterilized the surface, suggesting that habitability may involve more than just being the right distance from the host star to have liquid water.”

The habitable zone around any star is the distance at which a world must orbit to receive just the right amount of energy to maintain water in a liquid state. Liquid water, as we all know, is necessary for life (as we know it) to evolve. Whereas the Earth orbits the Sun at an average distance of nearly 100 million miles (a distance that unsurprisingly puts us inside our star’s habitable zone), for a star as cool as Proxima Centauri, its habitable zone is closer. Much, much closer. This means Proxima b, with an orbital distance of approximately 4.6 million miles, is nearly 22 times closer to its star than the Earth is to the Sun. Orbiting so close to a star pumping out a flare ten times more powerful than the largest flare our Sun can generate is the space weather equivalent of sitting inside the blast zone of a nuclear weapon.

As MacGregor argues, Proxima Centauri is known to generate these kinds of flares, and Proxima b has been bathed in its radiation for eons. It doesn’t seem likely that the exoplanet would be able to form an atmosphere, let alone hold onto one.

So, what of Proxima b’s hypothetical aliens? Well, unless they’ve found a niche deep under layers of ice and/or rock, it seems that this “habitable” world is anything but.

For more on why Proxima b would be a bad place to take your honeymoon, read
Sorry, Proxima Centauri Is Probably a Hellhole, Too.

Exocomets Seen Transiting Kepler’s Stars

exocomets
ESO/L. Calçada

If you thought detecting small planets orbiting stars dozens of light-years distant was impressive, imagine trying to “see” individual comets zoom around their star. Well, astronomers have done just that after poring over 201,250 targets in the Kepler dataset.

NASA’s Kepler mission has been taking observational data since 2009, staring unblinkingly at a small area of sky in the direction of the constellation Cygnus until it transitioned into the K2 mission in 2013. In total, the space telescope has discovered over 2,500 confirmed exoplanets (and over 5,000 candidate exoplanets), transforming our understanding of the incredible menagerie of alien worlds in our galaxy. After including discoveries by other observatories, we know of over 3,500 exoplanets that are out there.

kepler-exoplanets
Kepler looks for very slight dips in light as exoplanets pass in front of their stars to detect alien worlds (NASA/JPL-Caltech)

Kepler detects exoplanets by watching out for periodic dips in the brightness of stars in its field of view. Should a slight dip in brightness be detected, it could mean that there’s an exoplanet orbiting in front of its host star—an event known as a “transit.” While these transits can help astronomers learn about the physical size of exoplanets and the period of their orbits, for example, there’s much more information in the transit data than initially meets the eye.

In a new study to be published in the journal Monthly Notices of the Royal Astronomical Society on Feb. 21, a team of researchers are reporting that they have found evidence for individual comets transiting in front of two stars. They detected six individual transits at the star KIC 3542116, which is located approximately 800 light-years from Earth, and one transit at KIC 11084727. Both stars of a similar type (F2V) and are quite bright.

Though other observations have revealed dusty evidence of cometary activity in other star systems before, this is the first time individual comets have been found leaving their own transit signal in Kepler data. And it turns out that their transit fingerprint is a little bit special:

comet-transits
One comet’s three transits around its host star, KIC 3542116. Credit: Rappaport et al. MNRAS 474, 1453, 2018.

“The transits have a distinct asymmetric shape with a steeper ingress and slower egress that can be ascribed to objects with a trailing dust tail passing over the stellar disk,” the astronomers write in their paper (arXiv preprint). “There are three deeper transits with depths of ≃ 0.1 percent that last for about a day, and three that are several times more shallow and of shorter duration.”

In other words, when compared with the transit of an exoplanet, comet transits appear wonky (or asymmetric). This is because comets possess tails of gas and dust that trail the nucleus; as the comet passes in front of its star, starlight is quickly blocked, but as it drifts by in its orbit, the dusty tail will act as a starlight dimmer, gradually allowing more starlight to be seen by Kepler. An exoplanet—or, indeed, any spherical object without a dusty tail—will create a symmetrical dip in the transit signal. Other possible causes of this unique transit signal (such as starspots and instrumental error) were systematically ruled out. (Interestingly, in a 1999 Astronomy & Astrophysics paper, this asymmetric comet transit signal was predicted by another team of researchers, giving this current work some extra certainty.)

But just because there was evidence of six comet transits at KIC 3542116, it doesn’t mean there were six comets. Some of those transits could have been caused by the same comet, so the researchers have hedged their bets, writing: “We have tentatively postulated that these are due to between 2 and 6 distinct comet-like bodies in the system.”

Using these transit data, the study also takes a stab at how big these comets are and even estimates their orbital velocities. The researchers calculate that these comets have masses that are comparable to Halley’s Comet, the famous short-period comet that orbits the sun every 74-79 years and was last visible from Earth in 1986. For the deeper transits (for KIC 3542116 and the single transit at KIC 11084727), they estimate that the comets causing those transits are travelling at speeds of between 35 to 50 kilometers per second (22 to 31 miles per second). For the shallow, narrow transits at KIC 3542116, the inferred speeds are between 75 to 90 kilometers per second (47 to 56 miles per second).

“From these speeds we can surmise that the corresponding orbital periods are ⪆ 90 days (and most probably, much longer) for the deeper transits, and ⪆ 50 days for the shorter events,” they write.

But the fact that comets were detected at two similar F2V-type stars gives the researchers pause. Is there something special about these stars that means there’s more likelihood of possessing comets? Or is it just chance? Also, the fact that these comet transits were identified by visually analyzing the Kepler datasets suggests that there are likely many more transits hiding in the archived Kepler observations.

One thing’s for sure: this is a mind-blowing discovery that underscores just how valuable exoplanet-hunting missions are for probing the environment around other stars and not just for discovering strange new worlds. I’m excited for what other discoveries are waiting in Kepler transit data and for future exoplanet-hunting missions such as NASA’s Transiting Exoplanet Survey Satellite (TESS) that is scheduled for launch this year.

‘Crasher Asteroids’ Photobomb Hubble’s Deep Gaze Into the Universe

asteroid-trails
NASA, ESA, and B. Sunnquist and J. Mack (STScI)

Like the infamous “Crasher Squirrel” that launched one of the most prolific memes in online history, “crasher asteroids” have photobombed the Hubble Space Telescope’s otherwise uninterrupted view of the ancient universe.

While carrying out its Frontier Fields survey of a random postage stamp-sized part of the sky in the direction of the galaxy cluster Abell 370, Hubble imaged many galaxies located at different distances over different epochs in time.

Visible in the observation are elliptical galaxies and spiral galaxies. Many are bright and bluish, but the vast majority are dim and reddish. The reddest blobs are the most distant galaxies in our observable universe; their light has been stretched (red-shifted) after traveling for billions of years through an expanding cosmos. These galaxies are the most ancient galaxies that formed within a billion years after the Big Bang.

But mixed in with this Hubble view of ancient light are bright arcs and dashes — tracks carved out by the rocky junk in our own solar system that is drifting in Hubble’s field of view, located a mere 160 million miles from Earth (on average). It’s sobering to think that the light from the reddest galaxies is nearly three times older than these asteroids.*

Abel 370 is located along the solar system’s ecliptic plane, around which the planets orbit the sun and the majority of asteroids in the asteroid belt between Mars and Jupiter are located. So, like looking through a swarm of bees, Hubble has captured the trails of asteroids in the foreground.

The trails themselves are created not by the motion of the asteroids, however, but by the motion of Hubble. While fixing its gaze on distant galaxies for hours at a time as it orbits Earth, Hubble’s position changes and, through an observational effect known as parallax, the positions of those asteroids appear to trace an arc when compared with the stationary background of galaxies billions of light-years distant.

As Hubble scanned its field of view, it revealed 20 asteroid trails, seven of which are unique objects (some of the asteroid trails were repeated observations of the same object, just captured at different times in Hubble’s orbit). Only two of these asteroids were previously discovered, the other five are newly discovered objects that were too faint for other observatories to detect.

So it goes to show that photobombing asteroids are useful for science and, though Hubble was observing the most distant objects in the cosmos, it was able to see a few of the rocks in our cosmic backyard.

*NOTE: Asteroids formed around the time our solar system first started creating planets, some 4.6 billion years ago. The most ancient galaxies are located over 13 billion light-years away, meaning the ancient light from those galaxies was produced 13 billion years ago.

Friday Flashback: Banff Ground Squirrel Witnessed Apollo 11 Landing (2009)

Buzz Aldrin poses for Armstrong's camera in 1969. Little did the astronauts realize... they were being watched... (NASA/NatGeo/Ian O'Neill)
Buzz Aldrin poses for Armstrong’s camera in 1969. Little did the astronauts realize… they were being watched… (NASA/NatGeo/Ian O’Neill)

The Solar System Just Had an Interstellar Visitor. Now It’s Gone

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Hello, goodbye interstellar comet. The hyperbolic orbit of Comet C/2017 C1 as plotted by JPL’s Small-Body Database Browser (NASA/JPL-Caltech)

Update: At original time of writing, C/2017 U1 was assumed to be a comet. But Followup observations by the Very Large Telescope in Chile on Oct. 25 found no trace of cometary activity. The object’s name has now been officially changed to A/2017 U1 as it is more likely an interstellar asteroid, not a comet.

Astronomers using the PanSTARRS 1 telescope in Maui may have discovered an alien comet.

Comets and asteroids usually originate from the outermost reaches of the solar system — they’re the ancient rocky, icy debris left over from the formation of the planets 4.6 billion years ago.

However, astronomers have long speculated that comets and asteroids originating from other stars might escape their stars, traverse interstellar distances and occasionally pay our solar system a visit. And looking at C/2017 U1’s extreme hyperbolic trajectory, it looks very likely it’s not from around these parts.

“If further observations confirm the unusual nature of this orbit this object may be the first clear case of an interstellar comet,” said Gareth Williams, associate director of the International Astronomical Union’s Minor Planet Center (MPC). A preliminary study of C/2017 U1 was published earlier today. (Since this statement, followup observations have indicated that the object might be an asteroid and not a comet.)

According to Sky & Telescope, the object entered the solar system at the extreme speed of 16 miles (26 kilometers) per second, meaning that it is capable of traveling a distance of 850 light-years over 10 million years, a comparatively short period in cosmic timescales.

Spotted on Oct. 18 as a very dim 20th magnitude object, astronomers calculated its trajectory and realized that it was departing the solar system after surviving a close encounter with the sun on Sept. 9, coming within 23.4 million miles (0.25 AU). Comets would vaporize at that distance from the sun, but as C/2017 U1’s speed is so extreme, it didn’t have time to heat up.

“It went past the sun really fast and may not have had time to heat up enough to break apart,” said dynamicist Bill Gray. Gray estimates that the comet is approximately 160 meters wide with a surface reflectivity of 10 percent.

But probably the coolest factor about this discovery is the possible origin of C/2017 U1. After calculating the direction at which the comet entered the solar system, it appears to have come from the constellation of Lyra and not so far from the star Vega. For science fiction fans this holds special meaning — that’s the star system where the SETI transmission originated in the Jodie Foster movie Contact.

For more on this neat discovery, check out the Sky & Telescope article.

Spinning Comet Slams its Brakes as It Makes Earth Flyby

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Images of Comet 41P/Tuttle-Giacobini-Kresak’s jets as observed by the Discovery Channel Telescope on March 19, 2017 (Schleicher/Lowell Observatory)

Although comets are static lumps of ancient ice for most of their lives, their personalities can rapidly change with a little heat from the sun. Now, astronomers have witnessed just how dynamic comets can be, seeing one dramatically slow its rate of rotation to the point where it may even reverse its spin.

Comets are the leftover detritus of planetary formation that were sprinkled around our sun 4.6 billion years ago. These primordial icy remains collected in the outermost reaches of the solar system and that’s where they stay until they get knocked off their gravitational perches to begin an interplanetary roller coaster ride. Some are unlucky and end up diving straight to a fiery, solar death. But others set up in stable orbits, making regular passes through the inner solar system, dazzling observers with their beautiful tails formed through heating by the sun.

One mile-wide short-period comet is called 41P/Tuttle-Giacobini-Kresak and it’s a slippery celestial object. First discovered in 1858 by U.S. astronomer Horace Parnell Tuttle, it disappeared soon after. But in 1907, French astronomer Michael Giacobini “rediscovered” the comet, only for it to disappear once again. Then, in 1951, Slovak astronomer Ľubor Kresák made the final “discovery” and now astronomers know exactly where to find it and when it will turn up in our night skies.

Its name, Tuttle-Giacobini-Kresak, reflects the wonderful 100-year discovery and rediscovery history of astronomy’s quest to keep tabs on the comet’s whereabouts.

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Comet 41P/Tuttle-Giacobini-Kresak as observed on March 22, 2017 (Kees Scherer/Knight Observatory, Tomar)

Now, 41P is the focus of an interesting cometary discovery. Taking 5.4 years to complete an orbit around the sun, 41P came within 13-million miles to Earth earlier this year, the closest it has come to our planet since it was first discovered by Tuttle. So, astronomers at Lowell Observatory, near Flagstaff, Ariz., used the 4.3-meter Discovery Channel Telescope near Happy Jack, the 1.1-meter Hall telescope and the 0.9-meter Robotic telescope on Anderson Mesa, to zoom-in on the interplanetary vagabond to measure its rotational speed.

Comets can be unpredictable beasts. Composed of rock and icy volatiles, when they are slowly heated by the sun as they approach perihelion (the closest point in their orbit to the sun), these ices sublimate (i.e. turn from ice to vapor without melting into a liquid), blasting gas and dust into space.

Over time, these jets are known to have a gradual effect the comet’s trajectory and rotation, but, over an astonishing observation run, Lowell astronomers saw a dramatic change in this comet’s spin. Over a short six-week period, the comet’s rate of rotation slowed from one rotation every 24 hours to once every 48 hours — its rate of rotation had halved. This is the most dramatic change in comet rotation speed ever recorded — and erupting jets from the comet’s surface are what slammed on the brakes.

This was confirmed by observing cyanogen gas, a common molecule found on comets that is composed of one carbon atom and one nitrogen atom, being ejected into space as the comet was being heated by sunlight.

“While we expected to observe cyanogen jets and be able to determine the rotation period, we did not anticipate detecting a change in the rotation period in such a short time interval,” said Lowell astronomer David Schleicher, who led the project, in a statement. “It turned out to be the largest change in the rotational period ever measured, more than a factor of ten greater than found in any other comet.”

For this rapid slowdown to occur, the researchers think that 41P must have a very elongated shape and be of very low density. In this scenario, if the jets are located near the end of its length, enough torque could be applied to cause the slowdown. If this continues, the researchers predict that the direction of rotation may even reverse.

“If future observations can accurately measure the dimensions of the nucleus, then the observed rotation period change would set limits on the comet’s density and internal strength,” added collaborator Matthew Knight. “Such detailed knowledge of a comet is usually only obtained by a dedicated spacecraft mission like the recently completed Rosetta mission to comet 67P/Churyumov-Gerasimenko.”