Massive, Long-Period Comets Are Way More Common Than We Thought


During the formation of the solar system, when the planets were molten messes and asteroid collisions (or “mudball” collisions, possibly) were commonplace, chunks of icy debris were flung away from the chaos surrounding our messy young star and relegated to a lifetime of solitude in the furthest-most reaches of the sun’s gravitational influence. This debris eventually settled and formed what is known as the Oort Cloud, a mysterious spherical shell of countless mountain-sized objects located nearly 200 billion miles away.

As the Oort Cloud is so distant, and there are no telescopes on Earth (or off-Earth) that can resolve these objects, we can only guess at how many icy lumps are out there lurking in the dark. But should a passing star cause a gravitational wobble in that region, a few of those ancient objects may be knocked off their delicate gravitational perches and they take the plunge back toward the sun, becoming what we humans call “long-period comets.” Only when we see these comets can we get a hint of the population of the Oort Cloud and the nature of long-period comets. But, as many of these deep space vagabonds have orbital periods of hundreds to millions of years, they are notoriously difficult to track.

A long period comet may appear in the sky tomorrow, but it may not return in Earth’s skies until the age of humanity is long gone and intelligent cockroaches roam the planet. It’s hard to keep track of comets with orbital periods longer than our lifespans, let alone the lifespan of our civilization.

So it may not come as a surprise that astronomers have woefully underestimated the number of long-period comets, according to a new study using observations from NASA’s Wide-field Infrared Survey Explorer, or WISE, mission. But not only that, these things are a lot bigger than we thought.

The study, which has been published in The Astrophysical Journal, found that WISE had detected three to five times more long-period comets pass the sun over an eight-month period than expected and revealed that there are seven-times more long-period comets at least 1 kilometer across.

“The number of comets speaks to the amount of material left over from the solar system’s formation,” said lead author James Bauer, of the University of Maryland, College Park, in a NASA statement. “We now know that there are more relatively large chunks of ancient material coming from the Oort Cloud than we thought.”

WISE completed its primary mission in 2011, but has now embarked on a new mission to look out for dim asteroids and comets that stray close to Earth, called NEOWISE (NEO is for “Near-Earth objects”). During its primary mission, WISE was tasked to observe the universe in infrared wavelengths — revealing the otherwise hidden secrets of distant galaxies and the faint glow of mysterious objects traveling through the solar system. Among these objects were a surprising number of long-period comets, objects that WISE was uniquely qualified to characterize.

When comets approach the sun, their ices sublimate, dust is blasted into space and they form their trademark coma (a gaseous “atmosphere”) and tails around their nuclei. These factors obscure the main mass of the comet; astronomers cannot directly see the icy nucleus through the gas and dust — astronomers therefore have a hard time estimating the size of the comet.

To gauge the size of a comet’s nucleus, WISE precisely measures the size of the comet’s coma and subtracts those measurements from dust models to reveal the nucleus’ size (NASA/JPL-Caltech)

But studying WISE’s precision infrared measurements of the comets’ comas, the researchers were able to deduce the actual nuclei sizes by subtracting observational data from theoretical models of the behavior of dust around a comet. In all, 56 long-period comets were studied and compared with observations of 95 “Jupiter family comets” — comets that have short orbital periods around the sun and are gravitationally influenced by Jupiter. This comparison between the two families of comets revealed that long-period comets aren’t only bigger than we expected, these monsters are up to twice the size of Jupiter family comets.

“Our results mean there’s an evolutionary difference between Jupiter family and long-period comets,” Bauer said.

The difference in comet sizes may not come as a surprise — Jupiter family comets have orbital periods less than 20 years and therefore spend much more time being heated by the sun. They lose mass through ice sublimation that, in turn, dislodges dust and other material, ultimately shedding mass. Long-period comets on the other hand are pristine having spend most of their lives in the deep space deep freeze, so they hold onto the material they were born with billions of years ago. Long-period comets are the epitome of primordial.

Naturally, no comet research would be complete without an Existential Reality Check™ and, as you may have guessed, this new research has a dark side.

“Comets travel much faster than asteroids, and some of them are very big,” said co-author Amy Mainzer, principal investigator of the NEOWISE mission at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Studies like this will help us define what kind of hazard long-period comets may pose.”


Great Balls of ‘Space Mud’ May Have Built Earth and Delivered Life’s Ingredients

Artist’s impression of the molten surface of early Earth (NASA)

When imagining how our planet formed 4.6 billion years ago from the protoplanetary disk surrounding our sun, images of large pieces of marauding space rock slamming into the molten surface of our proto-Earth likely come to mind.

But this conventional model of planetary creation may be missing a small, yet significant, detail. Those massive space rocks may not have been the conventional solid asteroids — they might have been massive balls of space mud.

This strange detail of planetary evolution is described in a new study published in the American Association for the Advancement of Science (AAAS) journal Science Advances and it kinda makes logical sense.

Using the wonderfully-named Mars and Asteroids Global Hydrology Numerical Model (or “MAGHNUM”), planetary scientists Phil Bland (Cornell University) and Bryan Travis (Planetary Science Institute) simulated the movement of material inside primordial carbonaceous chondrite asteroids — i.e. the earliest asteroids that formed from the sun’s protoplanetary disk that eventually went on to become the building blocks for Earth.

A simulated cross section of a 200-meter wide asteroid showing its internal temperature profile and convection currents (temperatures in Celsius). Credit: PSI

It turns out that these first asteroids weren’t cold and solid lumps of rock at all. By simulating the distribution of rock grains inside these asteroids, the researchers realized that the internal heat of the objects would have melted the icy volatiles inside, which then mixed with the fine dust particles. Convection would have then dominated a large portion of these asteroids, causing continuous mixing of water and dust. Like a child squishing a puddle of dirt to create sloppy “mud pies,” this convection would have formed a ball of, you guessed it, space mud.

Travis points out that “these bodies would have accreted as a high-porosity aggregate of igneous clasts and fine-grained primordial dust, with ice filling much of the pore space. Mud would have formed when the ice melted from heat released from decay of radioactive isotopes, and the resulting water mixed with fine-grained dust.”

In other words: balls of mud held together by mutual gravity, gently convected by the heat produced by the natural decay of radioactive materials.

Should this model hold up to further scrutiny, it has obvious implications for the genesis of life on Earth and could impact the study of exoplanets and their habitable potential. The ingredients for life on Earth originated in the primordial protoplanetary soup, but until now the assumption has been that the space rocks carrying water and other chemicals were solid and frozen. If they were in fact churning away in space as dynamic mud asteroids, they could have been the “pressure cookers” that delivered those ingredients to Earth’s surface.

So the next question would be: how did these exotic asteroids shape life on Earth?

MU69: New Horizons’ Next Kuiper Belt Target Is One Big Mystery

Not as advertised? 2014 MU69 could be one big Kuiper Belt mess (NASA/JHU-APL/SwRI/Steve Gribben)

“All bound for Mu Mu Land” — The KLF, ‘Justified and Ancient’ (seems appropriate)

After visiting Pluto on July 14, 2015, NASA’s epic New Horizons mission soared into the great unknown, a.k.a. the Kuiper Belt. This strange region, which extends beyond Pluto’s orbit, is known to be populated with dwarf planets, comets, asteroids and junk that was left behind after the solar system’s formation, five billion years ago.

In an effort to better understand the solar system’s boondocks, New Horizons is on a trajectory that will create a second flyby opportunity. On New Year’s Day 2019, the spacecraft will buzz a mysterious object called 2014 MU69. But although we know this Kuiper Belt Object is out there, astronomers aren’t entirely sure what it is. And that’s a bit of a problem.

For two seconds on June 3, astronomers were presented with an opportunity to better observe MU69, but instead of clearing up its mystery the occultation event has created more questions than answers.

An occultation is when an object, like a distant asteroid, drifts in front of a background star. If astronomers time it perfectly, they can observe the star at the time of occultation in a bid to image the tiny shadow that will rapidly speed across our planet. And in the case of the June 3 event, dozens of mission team members and collaborators were ready and waiting along the predicted shadow track in South Africa and Argentina. In all, 100,000 images were taken of the star during the rapid occultation.

What they saw — or, indeed, didn’t see — is a bit of a conundrum.

“These data show that MU69 might not be as dark or as large as some expected,” said Marc Buie, a New Horizons science team member and occultation team leader from Southwest Research Institute (SwRI) in Boulder, Colo., in a statement.

Observations by the Hubble Space Telescope had previously estimated that MU69 is between 12- to 25-miles wide. That might be a pretty big overestimation by all accounts. And it may not be a single object at all.

“These results are telling us something really interesting,” said Alan Stern, New Horizons Principal Investigator also of SwRI. “The fact that we accomplished the occultation observations from every planned observing site but didn’t detect the object itself likely means that either MU69 is highly reflective and smaller than some expected, or it may be a binary or even a swarm of smaller bodies left from the time when the planets in our solar system formed.”

If it’s the latter, this could pose a problem for New Horizons.

Before the mission encountered Pluto in 2015, there was concern that the dwarf planet’s neighborhood might have been filled with debris. This concern was heightened after Pluto’s moons Styx and Kerberos were revealed by Hubble in 2011, only four years before New Horizons was set to barrel through the system. If there were more sub-resolution chunks near Pluto, they would have been regarded as collision risks.

Although New Horizons survived the Pluto encounter, if MU69 is a swarm of debris and not a solid object, mission scientists will have to assess the impact risk once again when New Horizons attempts its second flyby in 2019.

More occultations are forecast for July 10 and July 17, and NASA will also be flying its airborne observatory SOFIA through the occultation path on July 10 in hopes of better resolving MU69’s true nature.

So, as New Horizons speeds toward MU69, one of the most ancient objects in our sun’s domain, mystery and potential danger awaits.

Battlestar Galactica’s “Twelve Colonies of Kobol” Star System Found?

An image at radio wavelengths of a young stellar quadruplet. Credit: CfA/Nature/Pineda
An image at radio wavelengths of a young stellar quadruplet. Credit: CfA/Nature/Pineda

825 light-years away, in the constellation of Perseus, hides one protostar and three previously unseen gas concentrations that are undergoing gravitational collapse — basically embryos of soon-to-be baby stars. Found through the analysis of data from radio telescopes by astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA), this tiny cluster of baby stars occupy a small volume only 10,000 AU across — meaning that they’d all easily fit within the confines of the boundaries of our solar system (yes, the Oort Cloud is the solar system’s outermost boundary).

This is exciting for a couple of reasons. Firstly, this little ‘stellar womb’ has given astronomers an opportunity to study the genesis of a multi-star system. Indeed, most stars in our galaxy belong to multi-star systems, whether that be binary or greater, and astronomers are currently trying to figure out whether they were born this way or whether, over time, stars jostled around and eventually became gravitationally bound. After analysis of the velocities of the protostar and stellar embryos, it appears that the masses are gravitationally interacting. In other words, it has the potential to mature into a quadruple star system in around 40,000 years, a minute amount of time in cosmic timescales. Although it is likely that the system will become unstable, possibly ejecting one or two of the stars in the process, it does provide observational evidence that multi-star systems can be born in a gravitational embrace.

A map of the Twelve Colonies via
A map of the Twelve Colonies via

But as I have a habit of linking astrophysical studies with science fiction imaginings, when I first saw this research, I immediately thought of the awesome re-imagined series’ Battlestar Galactica and Caprica.

Battlestar Galactica is set in the years following the Cylon attack on the Twelve Colonies of Kobol, which almost wiped out humanity in this far-flung part of the galaxy. The remaining survivors, headed by William Adama (Edward James Olmos), take to the stars in a fleet of ragtag spaceships in search of the fabled Earth. One of my favorite scifi storylines and favorite scfi TV shows. But I digress.

The Twelve Colonies consist of four stars — Helios Alpha, Helios Beta, Helios Delta and Helios Gamma — each with their own systems of planets, 12 in total, including capital world Caprica.

So that poses a question: Just because Battlestar Galactica imagines a quadruple star system (well, two binary systems in a mutual orbit), is it possible to have such a stable system of planets evolve in a multi-star system? Or are the gravitational interactions too complex for anything to coalesce and slot into stable orbits? Well, by understanding how multi-star systems evolve by finding examples like this embedded inside star forming molecular clouds, we may start to appreciate how common and how stable they are and whether accompanying planetary systems are a reality or something that will forever be confined to the Twelve Colonies.

READ MORE: Star Quadruplets Spied Growing Inside Stellar Womb (Discovery News)

Was Voyager 2 Hijacked by Aliens? No.

The Voyager 2 spacecraft has been speeding through the Solar System since 1977 and it’s seen a lot. Besides scooting past Jupiter, Saturn, Uranus and Neptune, the probe is now passing through the very limit of the heliosphere (called the heliopause) where it has begun to detect a magnetic field beyond the Solar System. The fact we have man-made objects exiting our star system is something that makes me goosebumpily.

For some perspective, Voyager 2 is so far away from Earth that it takes nearly 13 hours for commands sent from Earth to reach the probe.

After decades of travel, the NASA spacecraft continues to relay data back to us, making it one of the most profound and exciting space missions ever launched. Perhaps unsurprisingly, the aging explorer recently experienced a glitch and the data received by NASA was rather garbled.

Naturally, the conspiracy theorists were out in force quickly pointing their sticky fingers at a possible encounter of the 3rd kind. How these ‘aliens’ found the probe in the first place and reprogrammed the transmission for it to appear corrupt Earth-side is beyond me, but according to an ‘expert’ in Germany, aliens (with an aptitude for reprogramming 30 year old Earth hardware, presumably) were obviously to blame.

One of the alien implication articles came from yet another classic ‘science’ post thrown together by the UK’s Telegraph where they decided to take the word of a UFO expert (obviously a viable source) without any kind of counter-argument from a real expert of real science. (But this is the same publication that brought us other classics such as the skull on Mars and the Doomsday Turkey, so it’s not too surprising.)

As I discussed in a recent CRI English radio debate with Beyond Beijing hosts Chris Gelken and Xu Qinduo, the Voyager-alien implication is beyond funny; an entertaining sideline to poke fun at while NASA worked out what actually went wrong. But the big difference was that Chris and Xu had invited Seth Shostak (from the SETI Institute) and Douglas C. Lin (from the Kavli Institute for Astronomy and Astrophysics at Peking University) to join the fun. No UFO expert in sight, so the discussion was biased toward science and logic, not crazy talk.

(It was an awesome show by the way, and you can check out the recording via my Discovery News article.)

So what did happen to Voyager 2? It turns out that aliens are not required to answer this cosmic mystery.

On Tuesday, NASA announced that Voyager 2 had flipped one of its bits of memory the wrong way. “A value in a single memory location was changed from a 0 to a 1,” said JPL’s Veronia McGregor.

This glitch was thought to occur in the flight data system, which formats information for transmission to Earth. Should something go wonky in its memory allocation, the stuff it transmits can be turned into gibberish.

Although it isn’t known how this single bit was flipped (and we may never know, as Voyager 2 is an awful long way from home), it sounds very much like a cosmic ray event interfering with the onboard electronics. As cosmic rays are highly energetic charged particles, they can penetrate deep into computer systems, causing an error in calculations.

And this situation isn’t without precedent either. Recently, NASA’s Mars Reconnaissance Orbiter (MRO) was hit by a cosmic ray event, causing the onboard computer to switch to “safe mode.” Also, Voyager 2 is beginning to exit the Sun’s outermost sphere of influence, where turbulence and confused magnetic fields rule. If I had to guess, I’d say — statistically-speaking — the probe might have a greater chance of being hit by the most energetic cosmic rays from deep space.

Just because something “mysterious” happens in space doesn’t mean aliens, the Illuminati or some half-baked doomsday phenomenon caused it. Before jumping to conclusions it would be nice if certain newspapers and UFO experts alike could look at the most likely explanation before pulling the alien card.

Alas, I suspect that some things will never change.

Where is Planet X? Where is Nemesis?

Artists impression of the hypothetical star, Nemesis (Anynobody on Wikipedia)

Before Pluto was discovered, the world’s astronomers were captivated by the possibility of finding another massive planet beyond the orbit of Neptune. In 1930, Pluto was discovered lurking in what was considered to be the edge of the Solar System. However, it quickly became apparent that Pluto was tiny; it wasn’t the Planet X we were looking for. For the last 80 years, astronomers have been looking for a large planet that might go to some way of explaining interplanetary features such as the “Kuiper Cliff”, but Planet X has not been found. Unfortunately, the word “Planet X” has now become synonymous with conspiracy theories and doomsday, almost as notorious as the word “Nemesis”.

Nemesis is another unanswered question hanging over Solar System evolution: does the Sun have a binary twin? Is there a second, dim, hidden “sun” stalking it’s brighter counterpart from over a light year away? Some scientists have come forward to suggest that the existence of a hypothetical second sun — embodied as a brown dwarf or red dwarf — could explain some cyclical effects here on Earth (i.e. mass extinctions occurring with a strange regularity). Naturally, the discussion about Nemesis (like the discussion about the possibility of a massive Planet X) is purely academic, and only based on indirect observations and anecdotal evidence. Just because they might exist, doesn’t mean they do.

In a publication recently published to the arXiv database, one Italian researcher has dusted off this topic and asked a very basic question: Can we constrain the possible locations of Nemesis and/or Planet X if they did exist? His results are fascinating…
Continue reading “Where is Planet X? Where is Nemesis?”

Tune into Paranormal Radio with Captain Jack Tonight at 9pm (EST): 10 Mysteries of the Solar System

Paranormal Radio with Captain Jack logo
Paranormal Radio with Captain Jack logo

For my fourth appearance on Captain Jack’s Paranormal Radio show, I’ve been invited back to discuss a recent Universe Today article I wrote detailing some of my favourite Solar System mysteries. These mysteries include the coronal heating problem, the “Mars Curse” and Uranus’ tilt. I don’t have many answers, but there should be some surprises thrown in. Most likely Jack and I will meander into different topics, so it should be fun to listen in!

For more information on the show, see tonight’s profile. Remember, the show will be airing live over several US cities, satellite radio and the Internet. For more information on where it will be airing, check out the Paranormal Radio homepage. To listen to the live podcast, starting at 6pm (PST), 9pm (EST) or 2am (GMT), download the .pls file to activate your podcast-listening software, or use the popup Media Player (plugin needed).

Cheers! Ian