Forecasting the End: The Science of Rogue Planets

21 03 2013

ftefbook2I’m pleased to report that I had the opportunity to consult on (and occasionally appear in) an astronomy/geoscience/climate science crossover project for the Weather Channel this past year, entitled, Forecasting the End.

The show, which premiers this evening, uses extremely-low-probability astronomical or geophysical disasters as a hook to explore and present astronomy, geology, meteorology, and physics concepts in a novel (and admittedly fantastic) way.

Of the six-episode series, the first deals with the concept of so-called “rogue” planets, a timely subject of recent research.

What is a Rogue Planet?

Many astrophysicists, astronomers, and exoplanetologists have set their research sights on puzzling out exactly how it is that new star systems go about forming planets, (in this case “exoplanets,” or planets outside our solar system).  Interestingly, the fruits of their labor have in recent years led to the realization that the process is a frequently violent one.  -So violent, in fact, that during the gravity tango performed between a fledgling solar system’s new planets, one of these “dancers” is thrown right off of the dance floor.

In other words, it seems that planets are often ejected from their home star system in the chaos surrounding a newly-formed star.  This actually serves to help the “dance” between the rest of the worlds calm into a more stable, final set of orbits, perhaps turning it into more of a “march.”

Any one of these escaped exoplanets, then, becomes a “rogue” planet – left to wander the cosmos along its lonely escape trajectory for billions of years.

-And to confirm that this knowledge is more than just theoretical, astronomers revealed last November that they captured what looks for all the world to be a rogue planet in the flesh a mere 75 light-years away:

Infrared image of rogue planet CFBDSIR2149. (Credit: CFHT/P. Delorme)

Infrared image of rogue planet CFBDSIR2149. (Credit: CFHT/P. Delorme)

Rogue Planet as Cosmic Bard

Astronomy-savvy readers may recall a splash last year when researchers reported calculating that there may be billions of these dark, lonely worlds wandering the galaxy.  However, as the “giggle-check” champion astronomer Phil Plait of “Bad Astronomy” fame was quick to point out, compared to the amount of free space in the galaxy, the odds of a collision with these seemingly innumerable rogue planets – any collision – are mind-bendingly slim.

Hence, while the Forecasting’s exercise deals with a disaster that is legitimately statistically possible, it is a threat far less likely than, say, being hit by a meteorite.  Or winning the lottery three times in a row.

Instead, the rogue planet has a different, more sublime function.  It can help us tell a story, and in the telling, learn a little bit more about the Earth.

By exploring the “What if?” scenario provided by the idea of a rogue planet breezing through our solar system, we have the opportunity to illuminate a seemingly-unrelated and often misunderstood phenomena at work much closer to home (and – for the “aha” moment – much more relevant to traditional weather):  Seasons.

Wherefore Art Thou Seasons?

The cosmic roots of our annual swing between months spent shoveling snow and sunning on sandy beaches may not be at all intuitive.  However, this reality becomes much easier to grasp in terms of a cosmic disaster.

Allow me to explain.

Many (intuitively) misunderstand why it is that the seasons exist at all, believing logically that summer is when the Earth is closest to the Sun, and winter is when we’re farthest away.  This is actually not the case.

Why not?  Simply, because the Earth’s orbit is almost perfectly circular, there really isn’t that much difference between the heat received by the Earth at closest and farthest approach to and from the Sun.

Instead, the seasons are caused by the fact that the Earth is tilted as it goes around the Sun.  This means that the Earth doesn’t stand “upright” as it goes round, but rather, it leans:

Illustration that weather seasons are related to the Earth's axis tilt; Summer on the hemisphere pointed toward the sun (northern or southern), and winter for the hemisphere pointed away. (Credit: Ben McGee)

Illustration that weather seasons are related to the Earth’s axis tilt; Summer on the hemisphere (northern or southern) pointed toward the sun, and winter for the hemisphere pointed away. (Credit: Ben McGee)

Consequently, summer is when your side of the Earth (northern or southern hemisphere) is pointed toward the Sun, and winter is when your side of the planet is pointed away.

This is also why, at the equator, the temperature is so consistent throughout the year – at the geographic middle of the planet, straddling the line between hemispheres, you’re neither pointed toward or away during any time of year and experience sunny temperatures year-round.  In contrast, if the “near-and-far” season misconception were true, one would expect snowy winters in Barbados, which simply never occurs…

Playing with Weather via Orbital Dynamics

All of this having been said, the reality explained above – the current cause of our seasons – goes completely out the window in the scenario explored in Forecasting’s rogue planet episode.  There, the orbits of Jupiter and the inner planets are enlongated by a rogue planet flyby (ignoring for the sake of brevity orbital resonances that might make such a shift even more catastrophic than advertised), which has a surprising result:

Such an event turns the previously-mentioned misconception (that seasons are caused by distance with respect to the Sun) into fact for life on Earth!

In such a scenario, the shape of Earth’s orbit becomes more oval (ellipse) than circle, and it travels much closer to and farther away from the Sun during its yearly course (aphelion and perihelion) than it does now.  As a result, seasonal changes due to the Earth’s axial tilt are totally overwhelmed by the global swing in temperatures based just on proximity to the Sun.

NOTE: These effects were actually scientifically modeled on Earth by Penn State astronomer Darren Williams and paleoclimatologist David Pollard in an effort to explore the habitability of worlds with more elliptical orbits around other stars and were published in the International Journal of Astrobiology in 2002.  This paper, which formed the conceptual basis for the effects depicted in this episode, can be found here.

So now, on a post-rogue-planet-soon-to-be-apocalyptic Earth, everyone on the planet experiences summer and winter globally, which leads to a rapid sort of climate change completely disruptive to our way of life:

With an elliptical orbit, (where during half the year the Earth is much closer to the Sun than the other), Earth's seasons are global and driven by proximity to the Sun. (Credit: Ben McGee)

With an elliptical orbit, (where during half the year the Earth is much closer to the Sun than the other), Earth’s seasons are global and driven by proximity to the Sun. (Credit: Ben McGee)

Earthly Take-Home in an Exoplanetary Context

Aside from the tantalizing (for space scientists) or terrifying (for everyone else) infinitesimally-remote specter of some sort of  interaction with a rogue planet, this episode provides a a roundabout and extreme way to drive home a simple truth:  Astronomy relates directly to weather.

The knowledge that the study of the universe beyond can help us understand life at home is a powerful one, and the take-home truth (to me) of the rogue planet episode is that orbit shapes and axis tilts work to define the temperature (weather) for any world orbiting a star.

-And today, because our orbit is not elliptical, it is the tilt of our axis that dominates our climate and causes our seasons.

________________________________________
Stay tuned for more, and I’ll try and have one of these out for each episode!





Pluto’s Pain: The Unsung Story of Ceres

20 07 2012

Pluto is once again in the press, astronomers having recently discovered a fifth moon about the tiny, icy world.  -And, again, Pluto’s official designation as a “dwarf planet” is coming under fire.

However, Pluto’s pain really hearkens back to a much older story – one of an unsung planet that stood proudly in the rightful lineup alongside Earth, Venus, Mars, and the rest of the household-name kin of the Solar System for nearly a half-century, yet today nearly no one knows its name:

This is the oft-overlooked story of the scrappy planet Ceres [planet symbol:], which ultimately becomes the story of Pluto.

A Persistent Pattern

The story begins in the late 1700s, when the maturing discipline of astronomy discovered what was believed to be a pattern in the orbital semi-major axes (read: distances between) the planets.  The Cliff’s Notes version of the orbital mechanics here is that there appeared to be a gap between Mars and Jupiter where another planet should have been.

Thus at the turn of the 19th Century began a concerted effort to find this missing world, bringing to bear a contingent of respected astronomers and an arsenal of the most advanced telescopes the science of the time had to offer.

It wasn’t long before they hit paydirt.

(In an ironic turn, I should note that the subsequent discovery was made despite the fact that the ultimate logic of this proposition – the Titius-Bode Law – turned out to be wrong!)

 A Group Effort

In an unbelievable stroke of serendipity, one of the astronomers selected for the search won the race before he’d even entered.  Before Giuseppe Piazzi at the Academy of Palermo, Sicily had even been approached to join the strike team of planet-hunters, he pegged what would turn out to be Ceres while making separate astronomical observations on New Year’s Day, 1801.

A flurry of activity followed during the next year, with the observations changing hands multiple times before a young mathematician named Carl Friedrich Gauss (of differential geometry and magnetism fame), only 24 at the time, predicted the small world’s position to within a half-degree.

Gauss’s calculations led astronomers to the definitive discovery on December 31, 1801, nearly a year to the day of Piazzi’s initial discovery.

The Rise and Fall of Ceres

The discovery of a new world made waves through the astronomical community, with Piazzi naming the planet after the Roman goddess of agriculture, Ceres.  (The names Hera and Demeter have also been bounced about in different cultures, but the current generally-accepted name is Ceres.)

With a diameter of just over 600 miles, (almost exactly the same size of the peninsula of Korea), the world is something of a planetary runt.  However, this did not stop the planet from being included in astronomy textbooks as a brother amongst the rest of the known planets for more than a half-century.  Unlike the asteroids with which it was eventually found to share its orbit, Ceres is a true differentiated astronomical body that has reached so-called hydrostatic equilibrium, becoming a spherical world.

It was only as telescope technology improved and astronomy advanced that the understanding of what Ceres was began to change.  A sudden flood of asteroid discoveries at roughly the same orbital distance began to cast doubt upon Ceres’s uniqueness in the solar system.  Eventually, it was realized that all of these many new, small bodies would either have to also be called planets in order to remain consistent, or the definition of Ceres would have to be changed.

And so, unceremoniously, Ceres was demoted to the ringleader of the asteroids in the latter half of the 19th Century.  This means that by the time our grandparents came on-scene, one would have been hard-pressed to find a modern book that included more than a passing reference to this once-celebrated world.  It had become merely an asteroid.

The 2006 Upheaval

More than a century passed after the discovery of Ceres, and in the 20th Century a familiar story then began to unfold:  Pluto, which was determined to be a tiny world beyond the orbit of Uranus, was discovered in 1930.  It was added to textbooks as the ninth planet, as many of us grew up with.  However, during the 20th and early 21st Centuries, a flood of discoveries of other small, icy bodies in the outer solar system began to cast doubt upon Pluto’s uniqueness.  All of these objects together made up what became known as the Kuiper Belt, a zone of remnant material left over from our star system’s formation and the reservoir from which comets are occasionally pulled.

So, everyone knows that the reclassification of what makes a “planet” resulted in Pluto’s demotion to a new class of worlds called “dwarf planets.”  What few realized, however, was that Pluto’s loss was another’s vindication!

Ceres – waiting patiently in the wings for nearly 150 years – was promoted as a result of the change.  Instead of being “just” an asteroid, it too became a dwarf planet alongside Pluto.  Each as a result of the change evolved into small but noteworthy masters of their respective belts of material – Ceres the dwarf planet of the asteroid belt, Pluto the dwarf planet of the Kuiper belt.

In a way, the controversy resulted in long-awaited justice for little Ceres.

Take-Away

Perhaps, when engaged in your own debate about whether or not Pluto should be called a planet, you might decide to frame the conversation in a larger context.

It really isn’t just about Pluto.  Remember Ceres.





Extrasolar maelstrom!

22 10 2011

This week might be considered a red-letter period for discoveries relating to extrasolar planets, from imaging alien comets and their implications for otherworldly oceans to witnessing the dusty disks and primordial protoplanets of young, forming star systems.

In case you missed it, this week provides your healthy dose of Exoplanetology:

Very “Wet” Extrasolar System Found

Artist's concept, illustrating an icy planet-forming disk around the young star called TW Hydrae. (Credit: NASA/JPL-Caltech )

The European Space Agency’s Herschel Telescope recently discovered direct evidence of cold water vapor surrounding the disk of dusty material surrounding a young star.

Whereas earlier studies had detected evidence of warmer water vapor within the material of young star systems, this is the first to extend this zone of water vapor into the cold regions extending far away from the parent star, TW Hydrae.

This finding is very significant to those searching for habitable planets or the life that might arise on them, as it bolsters the idea that comet-strewn planetary systems like our own (with water-rich inner planets) might be common in the galaxy.

Heavy Comet Bombardment Observed in Alien Solar System

Artist's concept, illustrating a storm of comets around nearby star Eta Corvi. (Credit: NASA/JPL-Caltech)

Evidence of the comet storms suggested in the previous discovery and which left their own scars on the rocky worlds of our own Solar System during the period called the Late Heavy Bombardment, (look up at the moon for evidence,) has been detected in the nearby star system Eta Corvi.

Tantalizingly, NASA’s Spitzer Space Telescope has detected evidence of a titanic comet collision(s) – dust fragments that match the signature of a comet having been wiped out during an impact with a planet.

Further, the location of the dust plume coincides with the potential location of inner, rocky planets like our own…

Forming Planets Likely Culprit Dust-Sculpters

View of two spiral arms in the gas-rich circumstellar disk around star SAO 206462. (Credit: NAOJ/Subaru)

In a wave of discoveries that don’t seem to be letting up, researchers using the Subaru Telescope atop Mauna Kea in Hawaii have released images of spiral arms in the dust disk surrounding nearby star SAO 206462.

These images, the first of their kind, agree with simulations of what the gravitational effects of newly formed or forming planets can do to the gas and dust surrounding a young star.  (Researchers are cautious to point out, however, that other processes might be responsible for the pattens.)

Beyond potentially further bolstering our understanding of how planets and star systems form, the spirals suggest locations of further research to find extrasolar planets… and provide yet another serious contender for desktop wallpapers everywhere.

Humankind First: Birth of an Alien World Witnessed

Artist’s conception of newly born alien planet LkCa 15 b and its parent star. (Credit: Karen L. Teramura, UH IfA)

Not to be outdone by the truly significant discoveries already mentioned, a team of researchers using the Keck Observatory in Hawaii have imaged the youngest alien world to date – so young, in fact, that it is still forming out of the disk of gas and dust around star LkCa 15.

Using sophisticated optical techniques, the team was not only able to resolve the protoplanetary disk around the star LkCa 15, but they were able to peer into the zone where the new planet was spawning – a wide gap between the young parent star and an outer disk of dust.

What they found there was truly a first:  A protoplanet surrounded by a sheath of cooler dust and gas still falling into/onto the still-forming planet.

In all, it appears that with an accelerating pace the universe is becoming less a tapestry to simply observe and more an atlas of locations and potential destinations.  Will the names TW Hydrae, Eta Corvi, SAO 260462, and LkCa 15 one day fill an atlas of solar systems the way we now appraise continents on a globe?

-And will the subtle letters behind each name, themselves indicating the presence of a planet, fill the same atlas as we currently manage nations and provinces?

We can only hope… but at this rate, odds are looking good!





Solar System’s “Planet X” lost in space?

21 10 2011

Some researchers have proposed a new planet beyond the Oort Cloud. (Credit: Ben McGee)

Well, the intriguing possibilities affecting the likelihood of a mysterious companion in our Solar System continue to blossom.

First, the actions of comets suggested that there may be a large “Planet X” named Tyche beyond the Oort Cloud.  Then, we discovered planets around distant stars with highly elliptical, highly inclined orbits, giving us more potential places (oblique orbits) to look for distant, cool companions in our own system.

Now, SwRI researcher David Nesvorny recently published research indicating that our Solar System likely did have another giant planet in its youth that was flung into space as the planets matured and settled into their current orbits.

Why?  Well, as it turns out, computer modeling of star systems with only four giant planets, (read: Jupiter, Saturn, Uranus, and Neptune,) doesn’t tend to settle into a Solar System that looks anything like our own.  However, adding a fifth, giant icy world into the primordial mix appears to generate systems like ours, though this Planet X is ejected into interstellar space in the process.

So, according to this new research, there may indeed have been a Planet X in our planetary past, though not one that could ever return to fulfill doomsday prophesies.

Might the cold, shadowy deep beyond the prying eyes of our best infrared telescopes conceal large worlds awaiting the heady thrill of human exploration?  Research continues to tease us with the possibility.

I for one believe our star system has big surprises yet in store.  Time will tell.





The National Space Exploration Administration

26 05 2011

Is a National Space Exploration Administration the future of NASA? (Hypothetical logo credit: Ben McGee)

I’m a convert.  Yesterday, Apollo astroanut, geologist-moonwalker, and U.S. Senator Dr. Harrison “Jack” Schmitt made what amounts to one of the most daring space exploration suggestions to date:  End NASA.  -And I think I’m all for it.

Allow me to explain.

Dr. Schmitt testing NASA Apollo program field logistics. (Uncredited)

In a sweeping and devastatingly logical essay published on the “americasuncommonsense” blog, Dr. Schmitt makes a compelling case that NASA as a force for exploration and national growth has lost its way.  Irrecoverably.

Being the only scientist-astronaut to ever walk on another world, Dr. Schmitt possesses a unique credibility and vantage from which to make this sort of assessment.  He proposes that NASA and its administrative shortcomings be scrapped in favor of a new agency, which he calls the National Space Exploration Administration, or NSEA.

There is a precedent for this sort of rebirth or evolution, which Schmitt is quick to point out.  NASA itself was created as a combination of the National Advisory Committee on Aeronautics and Werner Von Braun’s Army Ballistic Missile Agency, (which was reponsible for one of the most ambitious space exploration initiatives, Project Horizon.)  Likewise, the U.S. Air Force was formed out of the U.S. Army Air Corps.

According to Schmitt, NASA’s climate activities could be cleanly adoped by the National Oceanic and Atmospheric Administration, NASA’s space science activities could be neatly rolled into the National Science Foundation, and NASA’s aeronautics research and technology would go back to the coalition of national research centers from which they were originally derived, a recreated National Advisory Committee on Aeronautics.

This, he argues, frees the new NSEA to do what NASA should have been doing all along – driving the human exploration of deep space and reestablishing American space superiority.  The straightforward mission of this new agency, as Schmitt envisions it, is as follows:

“Provide the People of the United States of America, as national security and economic interests demand, with the necessary infrastructure, entrepreneurial partnerships, and human and robotic operational capability to settle the Moon, utilize lunar resources, scientifically explore and settle Mars and other deep space destinations, and, if necessary, divert significant Earth-impacting objects.”

Finally,  this represents a clear-cut national space agency mission that (I believe) everyone who supports space exploration can wholeheartedly endorse.  -And, perhaps more importantly, having such a clear agency objective would end the space exploration/terrestrial science/space science budgetary tug-of-war that has chronically crippled NASA.

Check out the essay and decide for yourself.  I think it’s time to send our governmental representatives a phone call or an email and make them aware of this concept as well, so they will begin to ask the question, “is a NSEA the future of NASA?”








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