Exocomets Seen Transiting Kepler’s Stars

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 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:

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.

Black Hole’s Personality Not as Magnetic as Expected

This 2015 NASA Swift observation of V404 Cygni shows the X-ray echoes bouncing off rings of dust surrounding the binary system after the X-ray nova (Andrew Beardmore/Univ. of Leicester/NASA/Swift)

In 2015, a stellar-mass black hole in a binary star system underwent an accretion event causing it to erupt brightly across the electromagnetic spectrum. Slurping down the plasma from its stellar partner — an unfortunate sun-like star — the eruption became a valuable observation for astronomers and, in a recent study, researchers have used the event to better understand the magnetic environment surrounding the black hole.

The binary system in question is V404 Cygni, located 7,795 light-years from Earth, and that 2015 outburst was an X-ray nova, an eruption that previously occurred in 1989. Detected by NASA’s Swift space observatory and the Japanese Monitor of All-sky X-ray Image (MAXI) on board the International Space Station, the event quickly dimmed, a sign that the black hole had consumed its stellar meal.

Combining these X-ray data with observations by radio, infrared and optical telescopes, an international team of astronomers were able to measure emissions from the plasma close to the black hole’s event horizon as it cooled.

The black hole was formed after a massive star ran out of fuel and exploded as a supernova. Much of the magnetism of the progenitor star would have been retained post-supernova, so by measuring the emissions from the highly charged plasma, astronomers have a tool to probe deep inside the black hole’s “corona.” Like the sun’s corona — which is a magnetically-dominated region where solar plasma interacts with our star’s magnetic field (producing the solar wind and solar flares, for example) — it’s predicted that there should be a powerful interplay between the accreting plasma and the black hole’s coronal magnetism.

As charged particles interact magnetic fields, they experience acceleration radially (i.e. they spin around the magnetic field lines that guide their direction of propagation) and, should the magnetism be extreme (in a solar or, indeed, black hole’s corona), this plasma can be accelerated to relativistic speeds. In this case, synchrotron radiation may be generated. By measuring the radiation across all wavelengths, astronomers can thereby probe the magnetic environment close to a black hole as this radiation is directly related to how powerful a magnetic field is generating it.

A black hole with a magnetic field threading through an accretion disk (ESO)

According to the study, published in the journal Science on Dec. 8, V404 Cygni’s hungry black hole has a much weaker magnetic field than theory would suggest. And that’s a bit of a problem.

The researchers write: “Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 461 ± 12 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems.”

Black holes are poorly understood, but with the advent of gravitational wave (and “multimessenger”) astronomy and the excitement surrounding the Event Horizon Telescope, in the next few years we’re going to get a lot more intimate with these gravitational enigmas. Why this particular black hole’s magnetic environment is weaker than what would be expected, however, suggests that our theories surrounding black hole evolution are incomplete, so there will likely be some surprises in store.

“We need to understand black holes in general,” said collaborator Chris Packham, associate professor of physics and astronomy at The University of Texas at San Antonio (UTSA), in a statement. “If we go back to the very earliest point in our universe, just after the Big Bang, there seems to have always been a strong correlation between black holes and galaxies. It seems that the birth and evolution of black holes and galaxies, our cosmic island, are intimately linked. Our results are surprising and one that we’re still trying to puzzle out.”

The Winter 2018 Edition of Mercury Magazine Is Now Live!

The front cover of the Winter 2018 edition of Mercury (vol. 47, No. 1)

As many of you know, I became editor of Mercury magazine last year and my first edition is now live!

Mercury is a publication by the Astronomical Society of the Pacific (ASP), an awesome non-profit organization based out of San Francisco that has been working for over 125 years to advance science education, science literacy and astronomy appreciation around the world. Mercury is a part of the ASP’s mission and has been in publication for members since 1972. I’m deeply honored that the ASP has entrusted me with the magazine.

The Winter 2018 edition, which can now be downloaded via the members’ portal, is packed with great articles and columns by astronomers, science writers and education professionals, tackling everything from the Event Horizon Telescope to how the Arecibo Observatory is recovering after Hurricane Maria. We also have more on gravitational waves and multimessenger astronomy, doomed dwarf galaxies, mysteries in the galactic halo, sunspot history, interstellar asteroids, how to teach astronomy in a world filled with misinformation and news from the ASP’s annual conference in St. Louis.

To read this edition and be involved in the ASP’s mission, you have to be a member, but for a sneak peek of what is waiting for you inside this quarter’s edition of Mercury and my first as editor, you can review the contents and read some select excerpts here.

I’m excited to embark on this new adventure and can’t wait to begin planning for the Spring edition!

Tabby’s Star Dust-Up: There’s No Alien Megastructure

Sadly, not aliens (NASA/Getty/Ian O’Neill)

If you were hoping that the bizarre transit signals coming from Tabby’s Star were signs of a massive alien construction site, you’d better sit down.

A new study published in Astrophysical Journal Letters today documents a highly-detailed astronomical study of the star, concluding that this stellar oddity is driven by natural phenomena and most likely not caused by an extraterrestrial intelligence.

Since citizen scientists of the exoplanet project Planet Hunters identified the odd transit signal of KIC 8462852 from publicly-available data collected by NASA’s Kepler Space Telescope in 2015, the world has been captivated by what it means. Though KIC 8462852 is a fairly average star as stars go, it exhibited inexplicable dimming events that have never been seen before.

Finding something extraordinary in deep space is often followed by extraordinary explanations, including the possibility that some super-advanced alien civilization is building a “megastructure” around its star. Over time, more rational hypotheses have been ruled out, but how do you rule out aliens fiddling with their star’s brightness? Well, that’s taken a little more time.

Now, thanks to a study headed by astronomer Tabetha Boyajian of Louisiana State University in Baton Rouge, it seems the alien megastructure hypothesis has bitten the dust, literally.

“Dust is most likely the reason why the star’s light appears to dim and brighten,” Boyajian said in a statement. “The new data shows that different colors of light are being blocked at different intensities. Therefore, whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure.”

As you’d expect, if something solid (like a massive Alien Made™ solar energy collector) were to pass in front of a star, all wavelengths of light would be stopped at the same time. The fact that the dimming events are wavelength (brightness) dependent suggests that whatever is blocking the starlight isn’t a solid mass.

Boyajian, Tabby’s Star’s namesake who led the team that discovered the stellar dimming phenomenon, and her team of over 100 astronomers carried out an unprecedented observation campaign on the star from March 2016 to December 2017 using the Las Cumbres Observatory network. The project was supported by a Kickstarter campaign that raised $100,000 from 1,700 backers.

During the campaign, four distinct dimming events were detected at Tabby’s Star and each were given names by the project’s crowdfunding community. Starting in May 2017, the first two dips were named “Elsie” and “Celeste,” and the second two were named after the lost cities of Scotland’s “Scara Brae” and Cambodia’s “Angkor.”

“They’re ancient; we are watching things that happened more than 1,000 years ago. They’re almost certainly caused by something ordinary, at least on a cosmic scale. And yet that makes them more interesting, not less. But most of all, they’re mysterious.” — from “The First Post-Kepler Brightness Dips of KIC 8462852,” ApJL, 2018

Although the story of the alien megastructure may be coming to an end, this astronomical saga has been an incredible success for science outreach and public engagement with citizen science projects, like Planet Hunters. In this incredible age of astronomy where there’s simply too much data to analyse, scientists are increasingly turning to the public for help in making groundbreaking discoveries.

“If it wasn’t for people with an unbiased look on our universe, this unusual star would have been overlooked,” added Boyajian. “Again, without the public support for this dedicated observing run, we would not have this large amount of data.”

So, the search continues and I, for one, am excited for the next “alien megastructure” mystery …

Read more: The ‘Alien Megastructure’ Star Is Doing Weird Things Again

When Physics and Art Collide: The Story Behind My First Science Tattoo

From left to right: The LHC’s CMS detector, a simulation of a Higgs event in the ATLAS detector and the intricate design work by Daniel Meyer on my right arm inspired by the science of the LHC (CERN/LHC/CMS/ATLAS/LEITBILD)

On July 4, 2012, I was watching a live video feed from Europe, excited for an announcement that was about to make physics history.

Until that day, I had written dozens of blogs and articles about the Higgs boson and the drama coming from the Large Hadron Collider (LHC) construction and start-up. It was one of those rare and exciting times when world was excited for a — let’s face it — crazy complex physics theory, stirring a public frenzy for any news related to the “God Particle” and how it would transform our understanding of the universe.

Physicists were, naturally, more reserved, but the fact that the LHC was revving up and generating tiny “Big Bangs” with every particle collision inside its complex, building-sized detectors, even the most conservative physics researchers couldn’t help but express their anticipation for a new age of particle physics. The LHC was (and still is) the most complex machine built by humankind, after all.

Theorist Prof. Peter Higgs celebrates with his colleagues at CERN on July 4, 2012, after high-energy physicists announced their discovery of the Higgs boson (CERN)

All the while, we science writers were trying to keep up, finding analogies for what the LHC was really doing, explaining in plain terms what the hell physicists were looking for and why Professor Brian Cox was arguing with politicians on prime-time TV. Good times.

Personally, I was enthralled (and still am). I can’t believe that only five short years after the Higgs discovery announcement that particle physicists are carrying out cutting-edge science at the LHC and even referring to future high-energy accelerators as “Higgs boson factories.” The Higgs discovery was just the beginning, but in 2012 it felt like the end of a decades-long odyssey seeking out an elusive theoretical particle that mediates mass in our universe and the “last piece” of the Standard Model puzzle — indeed, its discovery resulted in the 2013 Nobel Prize for Physics for François Englert and Peter W. Higgs who, in the 1960’s, developed the theoretical framework for the Higgs mechanism.

The Higgs boson discovery was huge and, along with the first detection of gravitational waves, it’s the biggest story I’ve covered.

The beautifully complex CMS detector in the LHC (CERN/LHC/CMS)

But, I found myself asking after turning off the live feed from CERN in the summer of 2012, how would I commemorate the story of the Higgs boson? Would I just resign it to memory and move on with the next big thing in science? Or would I do something else?

Soon after, I started to bounce an idea off my wife, friends, family members, colleagues and associates. That period of my professional life with Discovery News was too big for me to forget. I wanted to make a permanent memorial to the physics, engineering, ingenuity and scientists behind that historic discovery.

I had to get a tattoo.

In the years since 2012, I became aware of many science communicators with awesome science-related tattoos, so I did a lot of research around what I wanted my tattoo to be, who would do it and when. By 2015 I promised myself it would happen (to a probability of “3-sigma,” at least) and I started investigating artists and, although I came across an ocean of stunning talent and fantastic concepts, it wasn’t until September of this year that I stumbled on work that truly resonated with me. By September I was at “5-sigma.”

simulated-production-of-a-higgs-event-in-atlas (1)
Simulated production of a Higgs event in the LHC’s ATLAS detector (CERN)

I came across Daniel Meyer’s (LEITBILD) work on Instagram and I was hooked, so I made an appointment and sent him some concept images. He was particularly inspired by the circular cross section of the LHC’s CMS detector and the particle jets in a simulation of a Higgs event (pictured above), so he got to work on the design and, after a three month wait, I got to see the final design and loved it. By the end of Friday, my first tattoo was on my right arm after a fantastic day of conversations about science, art and life.

Take a look at what it looked like in the studio before it was wrapped:

Daniel Meyer/LEITBILD

It’s been a long journey since I first decided I wanted a tattoo and I’m overjoyed to have found Daniel’s work. Be sure to check out more of his art on his website and on Instagram. Once my arm has properly healed, I’ll post some more pics, the detail is incredible.

Gravitational Waves Might Reveal Primordial Black Hole Mergers Just After the Big Bang


Imagine the early universe: The first massive stars sparked to life and rapidly consumed their supply of hydrogen. These “metal poor” stars lived hard and died fast, burning quickly and then exploding as powerful supernovas. This first population of stars seeded the universe with heavier elements (i.e. elements heavier than helium, elements known as “metals” by astronomers) and their deaths created the first stellar-mass black holes.

But say if there were black holes bumbling around the universe before the first supernovae? Where the heck did they come from?

Quantum Fluctuations

Some models of universal evolution suggests that immediately after the Big Bang, some 13.82 billion years ago, quantum fluctuations created pockets of dense matter as the universe started to expand. As inflation occurred and the universe cooled, these density fluctuations formed the vast large-scale structure of the universe that we observe today. These cosmological models suggest the early quantum density fluctuations may have been dramatic enough to create black holes — known as primordial black holes — and these ancient Big Bang remnants may still exist to this day.

The theoretical models surrounding the genesis of primordial black holes, however, are hard to test as observing the universe immediately after the Big Bang is, needless to say, very difficult. But now we know gravitational waves exist and physicists have detected the space-time ripples generated by the collision and merger of stellar-mass black holes and neutron stars, astronomers have an observational tool at their disposal.

Simple Idea, Not-So-Simple Implementation

In a new study published in Physical Review Letters, researchers have proposed that if we have the ability to detect gravitational waves produced before the first stars died, we may be able to carry out astronomical archaeological dig of sorts to possibly find evidence of these ancient black holes.

“The idea is very simple,” said physicist Savvas Koushiappas, of Brown University, in a statement. “With future gravitational wave experiments, we’ll be able to look back to a time before the formation of the first stars. So if we see black hole merger events before stars existed, then we’ll know that those black holes are not of stellar origin.”

Primordial black holes were first theorized by Stephen Hawking and others in the 1970’s, but it’s still unknown if they exist or whether we could even distinguish the primordial ones from the garden variety of stellar-mass black holes (it’s worth noting, however, that primordial black holes would have a range of masses and not restricted to stellar masses). Now we can detect gravitational waves, however, this could change as gravitational wave detector sensitivity increases, scientists will probe more distant (and therefore more ancient) black hole mergers. And, if we can detect gravitational waves originating from black hole mergers younger than 65 million years after the Big Bang, the researchers say, those black holes wouldn’t have a stellar origin as the first stars haven’t yet died — they could have only been born from the quantum mess immediately after the birth of our universe.

Read more about this fascinating line of investigation in the Brown University press release.

It’s a Trap: Extraterrestrial Ozone May be Hidden at Exoplanets’ Equators

eso1736a-rotated (1)

Fortunately for life on Earth, our planet has an ozone layer. This high-altitude gas performs an invaluable service to biology, acting as a kind of global “sunscreen” that blocks the most damaging forms of ultraviolet radiation. Early in the evolution of terrestrial life, if there were no ozone layer, life would have found it difficult to gain a foothold.

So, in our effort to seek out exoplanets that are suitable for life, future telescopes will seek out so-called “biosignatures” in the atmospheres of alien worlds. Astrobiologists would be excited to find ozone in particular — not only for its biology-friendly, UV-blocking abilities, but also because the molecule’s building blocks (three oxygen atoms) can originate from biological activity on the planet’s surface.

But in a new study published Wednesday (Nov. 29) in the journal Monthly Notices of the Royal Astronomical Society, researchers modeling atmospheric dynamics on tidally-locked “habitable zone” exoplanets have concluded that finding ozone in these exo-atmospheres may be a lot more challenging than we thought.

Red Dwarf Hellholes

Recently, two exoplanets have taken the science news cycle by storm. The first, Proxima b, is touted as the closest temperate exoplanet beyond our solar system. Located a mere 4.22 light-years from Earth, this (presumably) rocky world orbits its star, Proxima Centauri, at just the right distance within the habitable zone. Should this world possess an atmosphere, it would receive just the right amount of energy for any water on its surface to exist in a liquid state. As liquid water is essential for life on Earth, logic dictates that life may be possible there too.

Whether or not Proxima b has the right orbit about its star is academic; there are many other factors to consider before calling it “Earth-like.” For starters, habitable zone exoplanets around red dwarfs will be “tidally locked.” Tidal locking occurs because red dwarf habitable zones are very close to the cool star; so to receive the same amount of heating as our (obviously) habitable Earth, habitable exoplanets around red dwarfs need to cuddle up close. And because they are so close, the same hemisphere will always face the star, while the other hemisphere will always face away. These strange worlds are anything but “Earth-like.”

Also, Proxima Centauri is an angry little star, blasting its locale with regular flares, irradiating its interplanetary space with X-rays, UV and high-energy particles — things that will strip atmospheres from planets and drench planetary surfaces with biology-wrecking radiation. As I’ve previously written, Proxima b is likely a hellhole. And things don’t bode well for that other “habitable” exoplanet TRAPPIST-1d, either.

It’s a Trap

But let’s just say, for astrobiology-sake, that a tidally-locked world orbiting a red dwarf does host an atmosphere and an alien biosphere has managed to evolve despite these stellar challenges. This biosphere is also pretty Earth-like in that oxygen-producing lifeforms are there and the planetary atmosphere has its own ozone layer. As previously mentioned, ozone would be a pretty awesome molecule to find (in conjunction with other biosignatures). But what if no ozone is detected? Well, according to Ludmila Carone, of the Max Planck Institute for Astronomy in Germany, and her team, not finding detecting ozone doesn’t necessarily mean it’s not there, it’s just that the atmospheric dynamics of tidally-locked worlds are very different to Earth’s.

“Absence of traces of ozone in future observations does not have to mean there is no oxygen at all,” said Carone in a statement. “It might be found in different places than on Earth, or it might be very well hidden.”

Earth’s ozone is predominantly produced at the equator where sun-driven chemical reactions occur high in the atmosphere. Atmospheric flows then transport chemicals like ozone toward the poles, giving our planet a global distribution. When carrying out simulations of tidally-locked worlds, however, Carone’s team found that atmospheric flows may operate in reverse, where atmospheric flows travel from the poles to the equator. Therefore, any ozone produced at the equator will become trapped there, greatly reducing our ability to detect it.

“In principle, an exoplanet with an ozone layer that covers only the equatorial region may still be habitable,” added Carone. “Proxima b and TRAPPIST-1d orbit red dwarfs, reddish stars that emit very little harmful UV light to begin with. On the other hand, these stars can be very temperamental, and prone to violent outbursts of harmful radiation including UV.”

So the upshot is, until we have observatories powerful enough to study these hypothetical exoplanetary atmospheres — such as NASA’s James Webb Space Telescope (JWST) or the ESO’s Extremely Large Telescope (ELT) — we won’t know. But modelling the hypothetical atmospheres of these very alien worlds will help us understand what we will, or won’t, see in the not-so-distant future.

“We all knew from the beginning that the hunt for alien life will be a challenge,” said Carone. “As it turns out, we are only just scratching the surface of how difficult it really will be.”

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

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

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.

Antimatter Angst: The Universe Shouldn’t Exist

The Veil Nebula as seen by Hubble. Because it looks cool (NASA, ESA, Hubble Heritage Team)

The universe shouldn’t exist, according to new ultra-precise measurements of anti-protons.

But the fact that I’m typing this article and you’re reading it, however, suggests that we are here, so something must be awry with our understanding of the physics the universe is governed by.

The universe is the embodiment of an epic battle between matter and antimatter that occurred immediately after the Big Bang, 13.82 billion years ago. Evidently, matter won — because there are galaxies, stars, planets, you, me, hamsters, long walks on sandy beaches and beer — but how matter won is one of the biggest mysteries hanging over physics.

It is predicted that equal amounts of matter and antimatter were produced in the primordial universe (a basic prediction by the Standard Model of physics), but if that’s the case, all matter in the universe should have been annihilated when it came into contact with its antimatter counterpart — a Big Bang followed by a big disappointment.

This physics conundrum focuses on the idea that all particles have their antimatter twin with the same quantum numbers, only the exact opposite. Protons have anti-protons, electrons have positrons, neutrinos have anti-neutrinos etc.; a beautiful example of symmetry in the quantum world. But should one of these quantum numbers be very slightly different between matter and antimatter particles, it might explain why matter became the dominant “stuff” of the universe.

So, in an attempt to measure one of the quantum states of particles, physicists of CERN’s Baryon–Antibaryon Symmetry Experiment (BASE), located near Geneva, Switzerland, have made the most precise measurement of the anti-proton’s magnetic moment. BASE is a complex piece of hardware that can precisely measure the magnetic moments of protons and anti-protons in an attempt to detect an extremely small difference between the two. Should there be a difference, this might explain why matter is more dominant than antimatter.

However, this latest measurement of the magnetic moment of anti-protons has revealed that the magnetic moments of both protons and anti-protons are exactly the same to a record-breaking level of precision. In fact, the anti-proton measurement is even more precise than our measurements of the magnetic moment of a proton — a stunning feat considering how difficult anti-protons are to study.

“It is probably the first time that physicists get a more precise measurement for antimatter than for matter, which demonstrates the extraordinary progress accomplished at CERN’s Antiproton Decelerator,” said physicist Christian Smorra in a CERN statement. The Antiproton Decelerator is a machine that can capture antiparticles (created from particle collisions that occur at CERN’s Proton Synchrotron) and funnel them to other experiments, like BASE.

Antimatter is very tricky to observe and measure. Should these antiparticles come into contact with particles, they annihilate — you can’t simply shove a bunch of anti-protons into a flask and expect them to play nice. So, to prevent antimatter from making contact with matter, physicists have to create magnetic vacuum “traps” that can quarantine anti-protons from touching matter, thereby allowing further study.

A major area of research has been to develop ever more sophisticated magnetic traps; the slightest imperfections in a trap’s magnetic field containing the antimatter can allow particles to leak. The more perfect the magnetic field, the less chance there is of leakage and the longer antimatter remains levitating away from matter. Over the years, physicists have achieved longer and longer antimatter containment records.

In this new study, published in the journal Nature on Oct. 18, researchers used a combination of two cryogenically-cooled Penning traps that held anti-protons in place for a record-breaking 405 days. In that time they were able to apply another magnetic field to the antimatter, forcing quantum jumps in the particles’ spin. By doing this, they could measure their magnetic moments to astonishing accuracy.

According to their study, anti-protons have a magnetic moment of −2.792847344142 μN (where μN is the nuclear magneton, a physical constant). The proton’s magnetic moment is 2.7928473509 μN, almost exactly the same — the slight difference is well within the experiment’s error margin. As a consequence, if there’s a difference between the magnetic moment of protons and anti-protons, it must be much smaller than the experiment can currently detect.

These tiny measurements have huge — you could say: universal — implications.

“All of our observations find a complete symmetry between matter and antimatter, which is why the universe should not actually exist,” added Smorra. “An asymmetry must exist here somewhere but we simply do not understand where the difference is.”

Now the plan is to improve methods of capturing antimatter particles, pushing BASE to even higher precision, to see if there really is an asymmetry in magnetic moment between protons and anti-protons. If there’s not, well, physicists will need to find their asymmetry elsewhere.