Transport And Infrastructure

10 Lessons from the “Comet of the Century”

Remember Comet ISON? Last year began with a blizzard of hype, with stories repeating the mantra that this mysterious celestial visitor could become the “comet of the century.” This year begins with Comet ISON obliterated, an invisible cloud of debris expanding and traveling outward from the sun.

Death of Comet ISON: It entered the frame from lower right and fled the sun toward the upper right, falling apart as it went, in this time-lapse SOHO image from November 28, 2013.
(Credit: ESA/NASA/SOHO/SDO/GSFC)

For the millions of enthusiasts hoping to see a glowing dagger of light hanging in the night sky, the premature demise of Comet ISON was a crushing disappointment. But for the astronomers who had pinned great hopes on the comet as an object of study, Comet ISON fully lived up to its billing (see my preview article, The Life and Death of Comet ISON).

It is already the most closely observed comet in history. It inspired the Comet ISON Observing Campaign, which coordinated studies not only from around the world but from across the solar system. Some of the first scientific papers will be coming out this week at a meeting of the American Astronomical Society; expect the flow to keep going for a long time. Amateurs will get to participate as well, since much of the data on the comet will be released openly to the public.

But why wait? We’ve already learned some illuminating lessons from the late, great Comet ISON. [For more news, follow me on Twitter: @coreyspowell]

1. You can find amazing things while looking for junk. The two observers who found Comet ISON–Vitali Nevski and Artyom Novichonok–made their discovery largely by accident. They were working for the International Scientific Optical Network (hence ISON), a network of observatories that collaborate to study debris in orbit around the Earth and to monitor asteroids. Nevski has written a short explanation of how he and his partner happened on a comet instead. ISON continues on its primary mission of tracking space junk; Nevski modestly describes himself as an “engineer observer, not a professional in cometary astronomy.”

2. Comet ISON really was a comet of the century, and then some. Wait–what? Oh sure, it was a total dud for backyard observers, since it never even reached easy naked-eye visibility. As an astronomical object, however, Comet ISON really was something extraordinary: a fresh Oort Cloud comet that was also a sungrazer. Let me decode the terms.

The Oort Cloud is a huge swarm of inert comets orbiting in the icy depths, hundreds or thousands of times farther from the sun than Pluto. Most bright comets are “periodic,” meaning that they have flown past the sun repeatedly, getting cooked and altered in the process. Comet ISON was different. Its orbit shows that it came straight from the Oort Cloud. It had been in deep freeze since the formation of the solar system, so what astronomers were observing was an intact time capsule from 4.5 billion years ago.

Comet ISON in happier times. All that glowing gas and dust, stretching more than 8 million kilometers long, came from a solid body scarcely larger than a skyscraper. (Credit: Damian Peach)

Sungrazing comets are ones that pass extremely close to the sun, where the intense heat boils off their innards the fierce solar radiation makes the chemicals in the comet intensely visible. That makes sungrazing comets great scientific subjects…but most of them are too small and dim to study readily, and very few of them are fresh arrivals from the Oort Cloud. Comet ISON checked all the boxes: fresh, hot, and (relatively) bright. I asked Matthew Knight of Lowell Observatory: When is the last time astronomers saw a comet like that? His answer: “never,” at least not in the 200 years that astronomers have been able to track cometary orbits. By that measure, Comet ISON was at least the comet of the bicentennial.

3. The early solar system was a wildly unstable place. How did Comet ISON get out to the Oort Cloud in the first place? According to the latest theories, it was exiled during an era of extreme chaos in the solar system, starting 4.5 billion years ago. Early on, before Earth had even formed, Jupiter plunged in to less than 1/3 its present distance from then sun and then zoomed back out, flinging Comet ISON and trillions of others like it out beyond Neptune.

A second convulsion, about 600 million years later, exiled Comet ISON completely to the Oort Cloud, perhaps 1,000 times farther from the sun. At the same time, many other comets and asteroids came raining down on the young planets, battering the surface of Earth just as life was beginning to gain a foothold. I describe these ideas in much greater detail in my new article The Madness of the Planets. Astronomers are now scrutinizing Comet ISON’s composition to uncover evidence of its amazing journey.

4. Comet ISON’s cousins may have seeded life on Earth. This old idea gets a new spin from the latest theories. It may not be coincidence that the solar system’s second period of chaos, known as the Late Heavy Bombardment, roughly coincided with the first appearance of living things on Earth. Comets like ISON contain a lot of organic material–carbon-rich molecules that might have primed the early Earth with key ingredients for life. So while comets were blasting our planet’s surface, they might also have been setting the stage for today’s vibrant world. Unfortunately it is very hard to know what was happening on Earth at that early stage. Almost all traces of Earth’s surface from that time have been thoroughly eroded and erased, though Bruce Simonson at Oberlin College is making a dogged effort to sift through the traces of evidence from the attack of Comet ISON’s cousins.

5. It took a star (or a whole galaxy) to bring Comet ISON home. Once the comet found its way to the Oort Cloud, it remained largely inert for the next 3.9 billion years. It was in deep freeze, at temperatures just a few degrees above absolute zero (-273 degrees C, or -459 degrees F). It moved in a lazy orbit, taking 100,000 years or more to circle the sun just once; from out there, the sun looked just like another star, albeit an unusually bright one. Nothing changed for Comet ISON until something big happened.

The shove that dislodged ISON might have been the movement of a nearby star, whose gravitational pull dislodged the comet from its slumber. Or it might have taken the combined pull of the entire Milky Way galaxy to send Comet ISON back home. “The gravitational potential of the whole galaxy can destabilize comets,” explains Alessandro Morbidelli of the University of Nice. The Oort Cloud is so weakly attached to the sun that the gravitational pull of the galaxy essentially creates tides in the Oort Cloud, squeezing it and causing some vulnerable comets to fall inward. Comet ISON may have been one of those unlucky victims.

6. Comet ISON was a bomb, literally. Nevski and Novichonok were able to discover the comet while it was far from the sun, out past Jupiter, because it was already kicking up a big cloud of gas and dust. That ruckus is part of what made astronomers so optimistic that Comet ISON would be spectacularly bright; most comets don’t really get going until they are closer to the sun’s heat. Now we have some good ideas why the comet was such a precocious performer.

Karen Meech at the University of Hawaii ran computer models showing that Coet ISON was probably coated with a layer of frozen carbon dioxide (CO2) and carbon monoxide (CO), gases that vaporize at very low temperatures. Any comet that has experienced even a trickle of the sun’s warmth will have lost those gases. Comet ISON, which has been in deep freeze since birth, still had them. As a result, it erupted vigorously as soon as it hit the critical temperature for CO and CO2 to vaporize. Mike A’Hearn of the University of Maryland notes that the comet must also have been bombarded by cosmic radiation for billions of years while it idled in the Oort Cloud. The radiation shattered molecules in the comet; when heated, those molecules would then recombine explosively, like TNT. When it was first spotted, Comet ISON might have been in mid-detonation.

At any rate, Comet ISON’s hyperactive phase didn’t last. This is another lesson: First-time visitors from the Oort Cloud tend to peak early and then fizzle. That pattern may explain one of the most notorious cometary disappointments, Comet Kohoutek.

7. Little things have big consequences. Comet ISON’s tail stretched nearly 10 millions of kilometers across. Other comets have reached lengths up to 500 million kilometers–wider than Earth’s orbit around the sun! And yet the solid body of a comet is minuscule, typically no more than a 10 kilometers wide. The lesson here is that you don’t need much material to capture and reflect sunlight; think of wisps of cigarette smoke. The tail of a bright comet is so empty that it would be considered an extremely hard vacuum here on Earth. By the latest estimates, Comet ISON was a piker, no more than 500 meters across–and now, of course, it is nothing at all. Yet the similarly puny Comet Lovejoy made a beautiful show in 2011, and collectively comets have had a profound effect moving water and organic compounds around through the solar system. Comets may be small, but there are trillions of them…and they sure know how to put on a show.

This is the look of an old, eroded comet–Comet Hartley 2, seen by NASA’s EPOXI mission on November 4, 2010. The nucleus is about 2 kilometers long. (Credit: NASA/JPL-Caltech/UMD)

8. There is nothing to fear from Comet ISON. Every comet brings with it some nuttiness from the UFO/conspiracy theory crowd, and Comet ISON is no exception. Now that the comet has disintegrated, the fears linger on. The main concern is a based on the true detail that Earth may pass through the outer edges of Comet ISON’s debris trail later this month. But as the CIOC team explains, this will be no more intense than a typical meteor shower. In fact, it will be quite a bit less. Paul Wiegert of the University of Western Ontario estimates that the particles of Comet ISON reaching Earth will be “as fine as wood smoke,” 1,000 times smaller than the typical shooting star. The total mass of the comet debris raining down on us? About one pound (half a kilo). Like I said, no fear.

9. We’ve entered the age of interplanetary astronomy. On November 28, anyone with an internet connection could watch Comet ISON’s self-destructive swoop past the sun, nearly in real time. Even in an age of ubiquitous connectivity, the Comet ISON observing campaign marked a true milestone. The venerable Deep Impact comet probe watched from solar orbit. The Mars Reconnaissance Orbiter (MRO) watched the comet from Mars and MESSENGER watched from Mercury. The Hubble and Spitzer observatories scanned the comet from near-Earth space. The SOHO, SDO, and STEREO sun-monitoring probes captured the comet as it swung past the sun.

What we are witnessing is the brain transcending the body: Humans now have eyes all across the solar system.

10. Comet ISON is never coming back, but sequels are on the way. Even if Comet ISON hadn’t disintegrated, we never would have seen it again. It came in on a hyperbolic course, meaning it passes one time by the sun and then heads back to the Oort Cloud forever, perhaps breaking free from the sun entirely. But sequels are already on the way. On May 24 of this year, Earth will pass through the trail of Comet 209P/LINEAR, possibly producing a spectacular meteor shower. In August, the Rosetta spacecraft will rendezvous with Comet Churyumov-Gerasimenko, and then (all going well) drop a lander onto its surface in November. Just before that, on October 19, Comet Siding Springs will squeak 110,000 kilometers from Mars. The comet will pass so close that its coma (glowing envelope) will enshroud the planet and perhaps noticeably alter its atmosphere. Every spacecraft on and around Mars, including NASA’s upcoming MAVEN probe, will be watching.

“It happens to be a particularly good time for interesting comets; not just ISON, all these others as well,” says Mike A’Hearn. But it’s not just the comets getting better. We are getting better too, and Comet ISON–rest in peace–has already helped.

View the original article here

The Terror of Error. Murray Gell-Mann, Part 2

Three quarks. Centre National de la Recherche Scientifique

Blogs by their nature do not go through the editing a writer comes to value before new assemblages of words are let out in the world. No matter how many times I reread and revise a post, I am chagrined how often I find, after pressing “publish,” that there is a typo or two. These are not actually random mistypings — spellcheck usually spots those — but neurological malfunctions. Bugs in the wetware. I will think one word and type another, and with each rereading my mind automatically sees what I intended and not what I typed. The wound heals over and the scab goes unnoticed. Until I press “publish” and the blunders jump out at me.

A good editor can also protect you from worse sins — errors of fact or logic — and they can protect you from yourself. From those times you’re blinkered by your own slender wormhole or when you wander too far out on a rhetorical twig. After I began writing this, I came across this observation about blogs by Susan Orlean:

. . . you have no editor and no opportunity to have your work filtered through a critical eye. . . . somebody who says, ‘This doesn’t make sense to me,’ or, ‘Why are you writing this piece?’ or, ‘This lede just doesn’t engage me.’ A blog just doesn’t offer you that.

Making an error, large or small, and committing it to print — that is one of the demons that tormented Murray Gell-Mann, and made it so difficult for him to write the papers that marked him as the greatest physicist of his generation. He described his fear at the beginning of his book, The Quark and the Jaguar, which I mentioned in my previous post.

Anyone who knows me [Gell-Mann wrote] is aware of my intolerance of mistakes, as manifested for example in my ceaseless editing of French, Italian, and Spanish words on American restaurant menus. When I come across an inaccuracy in a book written by somebody else, I become discouraged, wondering whether I can really learn something from an author who has already been proved wrong on at least one point. When the errors concern me or my work, I become furious. The reader of this volume can therefore readily imagine the agonies of embarrassment I am already enduring just through imagining dozens of serious mistakes being found by my friends and colleagues after publication and pointed out, whether gleefully or sorrowfully, to the perfectionist author.

He recalled a story he once heard about a legendary lighthouse keeper, occupying his long, lonely nights by scouring books, one after the other, and noting each mistake.

That erudite lighthouse keeper must have been beaming his beacon into Murray’s eyes when he was struggling to write his landmark paper about The Eightfold Way — the periodic table that brought order to the seemingly haphazard realm of elementary particles like protons, neutrons, and mesons. He would submit the paper to Physical Review and then, after lying awake agonizing over the details, withdraw it from consideration. For a year he went back and forth, back and forth before finally letting go of the draft. It was rushed into print, and just in time, appearing in February 1962. The Israeli physicist Yuval Ne’eman had independently come up with the same idea. If Ne’eman’s paper hadn’t been bounced because of a formatting problem (his secretary didn’t double-space the manuscript) he would have beat Murray to the punch. Ne’eman got plenty of respect but Gell-Mann got the ownership every physicist craves.

Two years later, in 1964, came his paper, “A Schematic Model of Baryons and Mesons,” the one that was honored this week at Caltech. What had long been considered the most fundamental particles turned out to be glommed together from tinier things called quarks.

But were they really things with a palpable existence or just numbers, a fancy kind of accounting device — “a useful mathematical figment,” as Gell-Mann later put it? It was a question that bedeviled him and will be the subject here of a forthcoming post.

Quarks were another idea independently and almost simultaneously discovered, this time by George Zweig. Gell-Mann’s earlier claim to fame, the discovery of what he called “strangeness,” was also arrived at by another theorist, Kazuhiko Nishijima. But no one shared Murray’s zest for evocative names — quark, strangeness, Eightfold Way. And no one had lit upon three such powerful ideas. It was fitting that he alone was awarded, in 1969, the Nobel prize in physics.

While I was writing Strange Beauty, I was lucky to be invited to a Nobel Prize ceremony and witness firsthand the lavish affair. This time Steven Chu, who later became Obama’s Secretary of Energy, was one of the winners. But I wish I could have watched Murray at Stockholm. I was able to piece together the details of his experience through interviews and archival sources. Here is how I described it in Strange Beauty:

When the ceremony was over, the laureates and their families were packed into limousines and chauffeured across the river for the banquet at Sweden’s architectural gem, the Town Hall. To the accompaniment of a chamber ensemble, the laureates filed into the elegant Golden Hall, with its 24-karat mosaics. In further keeping with the pre-eminence Nobel had given physics, Margaret, as wife of the sole winner of that year’s prize, entered the hall on the arm of the king and sat by his side during the long dinner. Murray was wedged between the princess and the queen. After the toasts, course after course of lavish dishes were announced with musical fanfares, the army of waiters striding in formation to serve the food. Champagne (Krug brut reserve) was followed by an appetizer of avocado stuffed with salmon and then, for the main course, a roast filet of beef with truffles (Périgourdine style), served with a 1959 Bordeaux from Chateau Potensac. (But alas, no pheasant cooked between slices of veal.) Then with the orange sorbet and coffee and liquers, the after-dinner speeches began.

Murray charmed his hosts by launching into Swedish during his dinner talk, later beating himself up because he had mispronounced a word. Afterwards the fear of error probably contributed to his troubles in writing up his Nobel lecture for publication in the annual volume, Le Prix Nobel. This again is from Strange Beauty:

Seized with a pernicious case of writer’s block, something that has plagued him all his life, he fended off one urgent telegram after another with abject apologies, finally conceding — months after the deadline was extended again and again for his benefit — that he wouldn’t be submitting a lecture after all. Among the rows of volumes commemorating each year’s prizes, one will find an empty page for Murray Gell-Mann.

Gell-Mann’s Nobel citation didn’t specifically mention quarks. It wasn’t entirely clear yet that they existed. You may have been puzzled by an obscure aside in my description of the Nobel banquet — “pheasant cooked between slices of veal” — and that is part of the story, the one I’ll tell next.

(to be continued)

Lighthouse keepers: Please report typos and other neurological glitches by email or through Twitter.

@byGeorgeJohnson

Related: Strange Beauty web page

For a glimpse of my new book, The Cancer Chronicles, please see this website.

View the original article here

An Idea as Grand as the Ritz

The core of a Magic Eightball. (from ginifab.com)

I hadn’t thought, until a few days ago, when I was thumbing through Strange Beauty, about the origin of the word ritzy. It has become so ingrained in the language that it somehow sounds like what it means. I vaguely knew about the Hotel Ritz in Paris and the Ritz Carlton chain. These places were called that, I supposed, because they were ritzy.

Actually it worked the other way around. There was a Swiss hotelier named César Ritz, whose original establishment was so chic and luxurious that a new superlative was coined. Much of the renown lay with the cuisine, prepared under the direction of Georges Auguste Escoffier, who became the preeminent French chef of his day. Escoffier, oddly enough, figures into the history of modern physics, though in a very roundabout way.

In my previous post I introduced Murray Gell-Mann’s Eightfold Way, an elegant mathematical theory in which the bewildering mess of subatomic particles can be described as if each is one face of an abstract polygon — an imaginary object that can be rotated in multidimensional space. Here is how I described the discovery in Strange Beauty:

As Murray worked out the equations, he marveled at the beauty of the architecture, this pattern unfolding in his mind. Using the eight operations allowed by [the theory], each particle could be converted into any of the others. Or, to use a different metaphor, there were eight “currents” through which the members of the group could flow from one into the other, assuming new identities. . . . Like the old child’s toy called the Magic Eightball, each face displays a different message.

Hour after hour he played with these mental objects.

The ease with which the pieces were fitting together was exhilarating. Within days the whole scheme was in place. Murray called it the Eightfold Way. Not just because there were eight possible rotations and eight particles in each representation but because of a saying of the Buddha about the eight ways to achieve Nirvana: “Now this, O monks, is noble truth that leads to the cessation of pain; this is the noble Eightfold Way: namely, right views, right intention, right speech, right action, right living, right effort, right mindfulness, right concentration.”

Murray himself was in Nirvana. For years all these different particles had come raining down on earth or ricochetting from the blasts of accelerators. Where there had been confusion now there was hope of order.

He didn’t believe this had anything to do with the Buddha — the name was a kind of joke. He quickly came to fear that his science itself was “crackpot.” It didn’t help that his eightballs described some particles not known to exist. But before long experimenters discovered them in their particle accelerators, and the Eightfold Way became a triumph.

What Mendeleev had done for the elements (which turned out not to be so elemental) Gell-Mann had done for the subatomic particles. But that was just the beginning. The mathematics he was using (called group theory) suggested that the polygons could be neatly decomposed into smaller pieces. Tap an eightball gently on the edge and it would shatter into smaller shards — perfect mathematical gems called triplets.

All of this was very abstract, and in the book I described the months that passed as theorists puzzled over the meaning. Just as Mendeleev’s elements turned out to be made from smaller particles like protons and neutrons, could these pieces be further broken down? Could each particle consist of a triplet of three even more fundamental entities — the true atoms of the universe? But how could a particle like a proton, with a charge of +1, be made from three smaller units? Particles with fractional charges seemed like an absurdity. Nothing like that had been observed.

Maybe these “kworks,” as Murray called them, (he had the sound in his head before he found the spelling in Joyce) were just interesting mathematical figments. “It is fun to speculate,” he wrote, “about the way quarks would behave if they were physical particles of finite mass (instead of purely mathematical entities). . . . A search for stable quarks . . . would help to reassure us of the nonexistence of real quarks.” Those are my italics. He assumed these weird things would not be found.

Gell-Mann struggled for the words that would imperfectly describe his quarks, calling them not only “mathematical” but even “fictitious.” One colleague interpreted Murray’s maddening ambiguity like this: “If quarks are not found, remember I never said they would be; if they are found, remember I thought of them first.”

He continued to hedge his bets. In 1967, when he and Richard Feynman — “the hottest properties in theoretical physics today” — were featured in The New York Times Sunday Magazine, Gell-Mann said quarks would likely prove to be “a useful mathematical figment.” At a lecture at a physics summer school in Erice, Sicily, he said that quarks might well turn out to be “purely illusory, a passing phase in our description, which will go away after a while, when we will learn how to . . . solve our equations without using quarks.”

Meanwhile they served him as a “pedagogical” device, a calculating tool for extracting new insights about the implications of the Eightfold Way. In one talk he used fictitious triplets to construct a model of the strong nuclear force “which may or may not have anything to do with reality.” After using this toy theory to abstract some general principles, he threw the field model away.

When his friend Valentine Telegdi learned about the technique, he told Murray it was like one used by the French chef Escoffier: Cook a pheasant between two slices of veal. Then discard the veal and serve the pheasant.

That to me is a testimony to Murray’s brilliance, the ability to hold contradictory ideas in one’s mind. Though be believed, deep down, that quarks lacked the solidity of electrons or even of neutrinos, the idea was too beautiful to let go of. He stuck with it, and before long evidence was found that pointlike particles indeed existed inside protons and neutrons

A theory called quantum chromodynamics (Murray named it and was one of the inventors) went on to explain why the quarks never appear independently in the world — why we don’t observe fractional charges. The nature of the strong nuclear force ensures that the quarks are permanently trapped, or “confined.”

With the existence of quarks established, Murray was soon insisting that he had believed in them all along. That was one of the reasons he was livid when my biography was published, providing ample evidence to the contrary. This is mostly a matter of interest to historians and philosphers of science, and I still wonder why he was so adamant and so angry. That initial ontological confusion was shared by most of his colleagues. It doesn’t detract in the slightest from his accomplishment. He had made one of the most important scientific discoveries of the century. He was the Escoffier of particle physics.

Please report typos and other neurological glitches by email or through Twitter.

@byGeorgeJohnson

Related: Strange Beauty web page

For a glimpse of my new book, The Cancer Chronicles, please see this website.

View the original article here

Clues from the Comet of the Century

Immediately after co-discovering Comet ISON the night of Sept. 21, 2012, Russian astronomer Vitali Nevski trumpeted it as a “comet of the century.” Although it initially fell short as visual spectacle, Comet ISON has fully lived up to its billing as a scientific sensation.

“It’s letting us look at material that formed 4.56 billion years ago and learn about the initial conditions that helped lead to the planets,” says Comet ISON Observing Campaign (CIOC) leader Carey Lisse.

Subscribe and get 10 issues packed with:The latest news, theories and developments in the world of scienceCompelling stories and breakthroughs in health, medicine and the mindEnvironmental issues and their relevance to daily lifeCutting-edge technology and its impact on our futureRegistration is FREE and takes only a few seconds to complete. If you are already registered on DiscoverMagazine.com, please log in.

View the original article here

Worlds Without End: Q&A with Exoplanet Hunter Sara Seager

In the mid-1990s, the discovery of worlds beyond our solar system changed astronomy forever. At the time, Sara Seager was slogging through graduate school, unhappy and unsure she even wanted a career in science. She decided to go for broke and devote her career to the new exoplanets, even though some doubted they were even real.

Soon, she published pioneering papers exploring the likely atmospheres of these exotic worlds and how we might identify an Earth-like “twin.” Exoplanet research now turns up new wonders nearly every week, and in 2013 Seager won a MacArthur Foundation “Genius” Fellowship for her discoveries.

Discover talked with Seager, now at the Massachusetts Institute of Technology, about what’s next in planet hunting.

Discover: What recent exoplanetary finds have amazed you? Sarah Seager: The best thing that’s happened in the past year or so is the [large] number of potentially habitable planets that have been found. I grew up with this field, so for me it’s so thrilling. The entire field is just snowballing.

The discoveries often are made possible by new instruments. What new equipment are you especially eager to use?

SS: Any time you put a new and more capable instrument on a telescope, you always find new things. The latest is the Gemini Planet Imager [in Chile]. It blocks out starlight, so you can see the planet directly and study its atmosphere. It will do direct imaging of giant Jupiter-like planets.

Your “starshade” idea, which could be launched into orbit by about 2022, would improve planetary picture-snapping. What’s the idea here?

SS: The challenge in finding an Earth twin is, how do you block out the light of a sunlike star to find a planet that’s 10 billion times fainter than it? The starshade does the hard work by blocking out all the starlight, spatially separating the planet and the star. You can use this shade with the equipment we already have, such as small commercial space telescopes that we already use for remote sensing of Earth’s atmosphere.

The Transiting Exoplanet Survey Satellite (TESS) is set to launch in 2017, and the James Webb Space Telescope will launch in 2018. What will they do?

SS: TESS will do an all-sky survey to find rocky worlds around the bright, closest M-stars [red dwarfs that are common and smaller than the sun — and therefore more likely to reveal the shadows cast by planets], about 500,000 stars. We’ll follow up with the James Webb to look at the atmospheres of this small pool of planets.

When a planet travels in front of its star, some of the starlight passes through the atmosphere, and some of the atmospheric gases leave telltale signatures on that starlight. By separating out the starlight from the planet light, we can identify molecules in the planet’s atmosphere and look for gases produced by life, like oxygen, ozone and ammonia.

With these newfound abilities to detect extraterrestrial life, you’ve recently revised the famous 1961 Drake equation, which calculates the odds for finding intelligent alien life and has influenced the search for it ever since. Why? What’s changed about our chances of success?

SS: I decided to revise the equation to tell the world that the real search for alien life is ongoing. The equation now tells us what the chances are that we’ll be able to find signs of life on a rocky exoplanet in the next decade with TESS and the James Webb.

The new equation has six terms. The first three are quantifiable: How many stars can we look at? How many are “quiet,” or not producing lots of radiation that could destroy biosignature gases or interfere with planet detection? And, how many stars have rocky planets in the habitable zone?

The next three terms of the equation involve the fraction of planets that can be observed, that have life and produce a detectable biosignature gas. Plugging in the numbers, the punch line is: If there is a rocky planet transiting a nearby bright M-star with signs of life in its atmosphere, we will be able to find it.

Some of the strangest details of the 3,500 likely alien worlds detected so far were discovered last year.

Kepler-62f
This rocky planet identified in April is closer to Earth’s size than any other world found in the habitable zone, the region around a star where surface water neither completely freezes nor boils away. This “super-Earth” is only 40 percent bigger than our planet.

HD 189733b
This “hot Jupiter” was found long ago, but last year, the Hubble Space Telescope revealed that it is blue, the result of light-scattering glassy particles in its scorching, whirling atmosphere.

Kepler-37b
The smallest exoplanet yet found around a sunlike star, this nubbin discovered in February is just slightly larger than our moon.

Kepler-7b
In September, visible and infrared light reflections from this hot, gassy planet provided the first alien weather report: clouds in the west, but clear skies out east.

GJ 504b
The lightest exoplanet directly imaged so far. Infrared data from Hawaii’s Subaru Telescope in August suggest it is magenta-colored.

Kepler-76b
Dubbed “Einstein’s planet,” researchers found this hot Jupiter in May using a technique based on the special theory of relativity: The gravitational tug of the exoplanet upon its star produces minor stellar brightening and shape-distorting effects.

What a run it was: For about four years, the Kepler space telescope watched more than 100,000 stars, looking for very slight dimming — a sign that a planet had crossed in front. By May, two of the four reaction wheels that precisely point the telescope had failed, leaving it too unstable to detect exoplanets around bright stars.

But half of Kepler’s data hasn’t yet been analyzed; this latter portion is where Earth-size worlds in habitable orbits are most likely to turn up, because the longer the mission and the more data the telescope collects, the stronger the signals are from these planets.

Says principal investigator Bill Borucki of NASA’s Ames Research Center: “The mission is entering its most exciting phase.”

[This article originally appeared in print as "Worlds Without End."]

View the original article here

New Signs of Long-Gone Life on Mars

In 1976, the Viking spacecraft gave us the first clear picture of the Martian surface — and sparked hopes that the barren, toxic planet once hosted life. In 2013, the rover Curiosity found the most convincing evidence yet that the planet was once habitable, as well as clues about why life there might have died out.

The $2.5 billion rover, roughly the size of a Mini Cooper automobile, discovered an ancient streambed soon after landing — evidence that water once flowed there. Next, Curiosity used its considerable payload of geologic tools to dig up further proof...

View the original article here

The Moon's Water Came From Earth

The moon, long thought to be bone dry, actually contains a surprising amount of water. In the latest twist, these stores turn out to be just like those on Earth, and probably filled by the same source: ancient asteroids.

These icy missiles likely bombarded the inner solar system billions of years ago, delivering water to the inner planets. Around this time, scientists believe, a stupendous collision between a Mars-size rock and the young Earth produced debris that eventually coalesced to form our moon.

Brown University’s Alberto Saal and colleagues measured the ratio of hydrogen to deuterium (hydrogen with an extra neutron) in lunar rock samples from the Apollo missions. This ratio reflects where in the solar system the material formed.

Moon samples had the same hydrogen-deuterium ratio as found in asteroids and Earth’s oceans. The simplest explanation, says Saal: The moon’s water was on Earth at the time of the giant impact.

[This article originally appeared in print as "Where Moon Water Comes From."]

View the original article here

Stars' Habitable Zones Are Larger Than Previously Thought

Good news for those searching for life elsewhere in the universe: a study released today suggests that planets orbiting surprisingly close to their stars can remain livable. This extension of the so-called habitable zone, based on computer modeling, is also important for what it implies about our own planet’s future habitability.

Studying habitable zones has always been tricky, because there’s only one habitable planet we know of—our own. Still, astronomers have established the general boundaries for what they call a star’s habitable zone, the donut-shaped region around that star where an Earth-like planet could host liquid water, necessary for life as we know it. At the zone’s outer edge water freezes from the cold, and at the inner edge it evaporates from the heat; conditions are “just right” inside the zone, hence the area’s other common nickname: the Goldilocks zone.

But it’s not as simple as all that, because stars’ output changes over time. The sun, for example, has been getting steadily brighter and hotter over the millennia. So scientists have used complicated models to determine the precise boundaries of any given star’s habitable zone over time.

But, as it turns out, they weren’t complicated enough. Today’s paper used 3-D climate models to determine just how hot a planet can get before it slips out of the habitable zone, and found that it can be hotter than the older, 1-D models suggested. (The new 3-D approach took into consideration things like clouds—a fairly important climate feature, if you think about it.)

So, whereas previously a sun-like star was believed to have a habitable zone starting at about 0.99 astronomical units away (where 1 AU is the average Sun-Earth distance of about 93 million miles), now it starts a bit closer, at 0.95 AU. The findings are reported today in Nature.

That might not seem like much, but it widens a sun-like star’s habitable zone by millions of miles. Thus it should, theoretically, be that much more likely for researchers to find an extrasolar planet out there with conditions suitable for life.

And the results also hit closer to home. With the sun’s ever-increasing output, we know there will come a time when its habitable zone leaves Earth behind, rendering our own planet uninhabitable. This study, which proved planets are more heat-resistant than thought, also suggests that “we” won’t have to worry about our world losing all its liquid water for at least another billion years. Phew!

Image credit Petigura/UC Berkeley, Howard/UH-Manoa, Marcy/UC Berkeley

View the original article here

My First Strange Encounter with Murray Gell-Mann

Credit line: Harvey of Pasadena, courtesy AIP Emilio Segre Visual Archives, Physics Today Collection

Long ago when I was working as a police reporter at the Albuquerque Journal, my best friend Richard Freedman called to deliver some exciting news: Murray Gell-Mann was giving a public lecture that evening up in Los Alamos, the city high in the Jemez Mountains where the atomic bomb was devised. Having made less than optimal use of our undergraduate education, Richard and I were studying new subjects like mad. Physics, philosophy, linear algebra — we were sure that somewhere therein lay the secret of the universe.

In school I hadn’t got past Physics 101 and an introduction to western philosophy. But throughout those years I had fallen in love with the literature of science – books like George Gamow’s Thirty Years That Shook Physics, Arthur Eddington’s The Nature of the Physical World, and The Universe and Dr. Einstein, Lincoln Barnett’s wonderful treatment of special and general relativity. I knew that the basic constituents of matter were quarks and that the man who had discovered them was Gell-Mann. It would have been wonderful to see this visionary in person — perhaps the greatest genius of the atomic age. (He would have looked much as he does in the picture at the top of this post.) But I was working the nightshift at the newspaper, and Los Alamos was a slow, 100-mile drive. For a combination of bad reasons, including inertia, I passed the opportunity by.

When I finally met Gell-Mann, approximately 15 years later, we got off to a bad start. By now I was working at the New York Times and I took a year’s leave of absence to move to Santa Fe and write Fire in the Mind. I was starting to spend time at the Santa Fe Institute, which was devoted to the emerging (and still emerging) sciences of complexity and where Gell-Mann was one of the most prominent thinkers. It was only a matter of time before our paths crossed.

The opportunity came one afternoon at Sol y Sombra, a magnificent estate on the outskirts of town that was occupied by Georgia O’Keefe in her dying days and, last I heard, is owned by Microsoft billionaire Paul Allen. The institute was holding a conference on the lush, rolling grounds. (Sol y Sombra means sun and shade.)

I walked into the meeting room and spotted Gell-Mann at the seminar table — “his full head of tightly packed white hair, his styleless glasses with black plastic frames.” That description is from the prologue of the biography I would later write: Strange Beauty: Murray Gell-Mann and the Revolution in 20th-Century Physics.

The scene continues:

He was wearing a turquoise bolo tie and a jacket with an emblem for the Nature Conservancy, one of the environmental organizations he champions. The field of complexity is intimately related to the phenomenon called chaos, and Murray was loudly complaining about a popular book on the subject written by my former New York Times colleague James Gleick. I had admired Chaos immensely and was a little shocked when Murray began to denounce “this Gleick person,” as he called him, for supposedly undermining the public’s understanding of science. And Gleick’s biography of Feynman made Murray livid. He conceded that Jim’s book was beautifully written, but that somehow just made it worse. (Later Murray met Jim’s brother, a scientist, who was visiting the Santa Fe Institute. They hit it off well, and from then on, Murray called him “the good Gleick.”)

When the meeting broke for lunch, I carried my plate to one of the long wooden tables and sat down. I felt a mild adrenaline jolt when I saw Gell-Mann walk in my direction and, quite by accident, sit down across from me. He put out his hand and said in his deep, nasal voice, “Hi. I’m Murray Gell-Mann.” I apprehensively introduced myself as an editor for The New York Times. “Oh, The Times,” he said, smiling with amusement. “That’s the place that employs that — what is his name? — that Wilford person.”

It seems that John Noble Wilford, the dean of American science journalism, had once written a story that Gell-Mann didn’t like. In the mid 1980s, some scientists at Purdue University were arguing that Galileo had got it wrong: A feather and a brick dropped inside a vacuum would not land simultaneously after all. A fifth force of nature — beyond gravity, electromagnetism, and the strong and weak nuclear forces — would cause some objects to accelerate faster than others. Wilford had called Gell-Mann to ask his opinion of what might conceivably have been a monumental discovery. After subjecting Wilford to a five- or ten-minute oration on everything that was wrong with science-writing today, Gell-Mann tried to dissuade him from writing the piece. No one had heard of these scientists, Murray told him. Their analysis was shaky and would doubtlessly turn out wrong.

As I listened to Gell-Mann tell the story, I could empathize with the frustration Wilford must have felt. Right or wrong, the fact that some card-carrying physicists were publishing this theory — now long forgotten — in Physical Review Letters was certainly newsworthy. Getting a quote from Gell-Mann would help put the story in perspective. I could imagine the clock ticking above Wilford’s head, the deadline approaching, and Gell-Mann stubbornly refusing to cooperate. Looking for a good quote, Wilford apparently did what any of us might have done: he asked a leading question, something like, “Well, if the theory does turn out to be right, would it be important?” “Well, yeah, of course,” Murray had replied. He was appalled to read the next morning on the front page of The Times that “Dr. Murray Gell-Mann, a theoretical physicist at the California Institute of Technology, said that if the conclusions of the study were correct, it was fair to speculate on the existence of a fifth force. . . .” Never mind that Wilford had taken all the care in the world to point out in his story how very tentative the research was. This had happened six years before, and Gell-Mann was not about to forgive him.

The story, given just the right spin by Gell-Mann, set off a round of laughter at the lunch table, which had filled with other physicists. I could see that it was going to be open season on science writers. And Gell-Mann was on a roll. “Things used to be worse,” he said. He told about another science writer, a two-time winner of the Pulitzer Prize, who infuriated him by refusing to believe in the existence of the famously elusive particle called the neutrino. He was, Gell-Mann declared, “a man of impenetrable stupidity unmatched even by science writers today.” This was getting to be a bit much. I had heard that Gell-Mann, the perfectionist and procrastinator, was having a huge amount of difficulty trying to write his own book, The Quark and the Jaguar, explaining complexity to a general audience. The manuscript was late and the publisher was ready to demand that he return his rather considerable advance. I couldn’t resist. “How is your book coming along?” I asked. “Umm. Not very well,” he admitted. He turned away and began talking to some physicists about string theory.

Last night I read in Sean Carroll’s blog, Preposterous Universe, that Gell-Mann was honored this week at Caltech on the 50th anniversary (which is early next month) of the paper that introduced the quark.

As with almost anything involving Murray (as almost everyone comes to call him), there is a story behind that paper, which I will tell, among others, in a forthcoming post.

My initial encounter with the man — one of the first Nobelists I had met — turned out to have a happier ending. A few weeks later I was invited to a Halloween party at the small house Seth Lloyd, one of Murray’s former students, was renting while visiting SFI. We were sitting in the floor carving jack-o’-lanterns when Gell-Mann sat down next to me.

“You know, I’m finding that this book-writing business isn’t as easy as it looks,” he said a little sheepishly. I took it as a touching concession, and before I knew it he was giving me chapters of his manuscript to read.

About a year after that I decided, to his great consternation, to write his biography.

(to be continued)

Murray Gell-Mann at the World Economic Forum Annual Meeting, 2012. Wikipedia

Related: Strange Beauty web page
The Books in the Basement

For a glimpse of my new book, The Cancer Chronicles, please see this website.

@byGeorgeJohnson

View the original article here

The Secret Origins of Cosmic Rays

Where do cosmic rays come from, and what makes them the highest-energy particles in the universe? Until recently, no one knew for sure. But in February, scientists discovered that stellar explosions known as supernovae act like particle accelerators, boosting protons’ speeds enough to turn them into cosmic rays.Subscribe and get 10 issues packed with:The latest news, theories and developments in the world of scienceCompelling stories and breakthroughs in health, medicine and the mindEnvironmental issues and their relevance to daily lifeCutting-edge technology and its impact on our futureRegistration is FREE and takes only a few seconds to complete. If you are already registered on DiscoverMagazine.com, please log in.

View the original article here

Kaleidoscopic View of the Sun Reveals its Hidden Features

A screenshot of a movie of the sun from NASA’s Solar Dynamics Observatory. The pie-shaped slices show the sun in different wavelengths of light that are ordinarily invisible to our eyes. Each highlights different kinds of features on the sun’s surface and in its corona. (Source: NASA Goddard Space Flight Center)

The human visual system is an incredible example of natural engineering that far surpasses the very best cameras and lenses. To offer one example, on a bright day with extremely contrasty light, it can discern fine details in both the dark shadows and bright highlights — details that are all but lost in to a camera.

Even so, what we can see is extremely limited compared to what’s actually out there — a fact that is dramatically illustrated by the kaleidoscopic view of the sun above. It’s a frame from a movie put together by NASA to illustrate the abilities of the Solar Dynamics Observatory, an orbiting satellite that continuously monitors the sun.

SDO’s instruments are sensitive to wavelengths of light that are invisible to us. In the image, above (and the full video below), each pie-shaped slice represents a view of the sun in a particular wavelength. Viewing the sun in different wavelengths allows scientists to discern different kinds of features on its surface and in its atmosphere, called the corona.

Here’s the full video:

Remember that in the video, and the image up top, the coloring is artificial.

Here are a few examples of what the various colored views show:

Yellow: Shows light with a wavelength of 5,800 Angstroms emanating from material that’s at about 10,000 degrees F (5700 degrees C). This wavelength highlights features on the surface of the sun.Green: Shows extreme ultraviolet light with a wavelength of 94 Angstroms. This light comes from atoms that are more than a thousand times hotter — at about 11 million degrees F (6,300,000 degrees C). Solar flares, which are extremely hot, show up well in this wavelength.Red: Shows another wavelength of extreme ultraviolet light, at 304 Angstroms. Plasma made of helium II ions, the second most abundant element in the sun’s atmosphere, emit light in this wavelength, which is good for discerning gigantic loops of plasma that align with features of the sun’s magnetic field.

The video below shows a particularly spectacular example of what can be seen when viewing the sun in this latter wavelength. It was captured by SDO on July 19, 2012.

First, a moderately powerful solar flare explodes from the sun. This is followed by an ejection of solar material, a phenomenon that’s known as a coronal mass ejection, or CME. And then the really spectacular fireworks begin:

The massive loops of glowing material are what’s known as coronal rain. This happens as plasma cools and condenses along magnetic field lines.

With the flare and CME, the sun’s magnetic field has bulged outward here. Ordinarily, it can’t be seen. But the glowing plasma acts like a tracer, making it visible. The plasma rains down for almost a full day (which is compressed into about four minutes in the video), until the bulge in the magnetic field dissipates.

SDO images of the sun seen in different wavelengths. (Source: NASA/SDO/Goddard Space Flight Center)

Last but not least, a mosaic of solar images showcasing the 13 different wavelengths of light that SDO’s instruments can discern.

Of course you should never look directly at the sun with the naked eye. Doing so could cause irreparable damage to that wonder of natural engineering — your vision. But the next time that you’re out and about on a sunny day, perhaps you can now see — in your mind’s eye — all the amazing detail and activity that’s ordinarily hidden from us.

View the original article here

Mars’ Past Habitability Is Even More Likely

Big news today from the Martian front. New data from everyone’s favorite car-sized roving robot, Curiosity, has come out, with implications for potential life on the Red Planet.

At a press conference today at the American Geophysical Union’s fall meeting in San Francisco, and in a bundle of six Science papers, scientists announced the extreme likelihood of an ancient lake near Curiosity’s landing site that was habitable for certain microbes, as well as greater details about the geological history of the landing site and the amount of harmful radiation that the rover’s been exposed to.

You may be forgiven for thinking this sounds a bit familiar.

Let’s start with what seems like the biggest news, from the most epically titled paper of the bunch: “A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars.” (Fluvio-lacustrine, just on the off chance you’re unfamiliar with the term, is a geological term meaning “produced by lakes and rivers.”) Yellowknife Bay is the specific area under scrutiny within Gale Crater, the 154-kilometer-diamater area where Curiosity landed and wanders.

By analyzing the environment with its lasers and drills and other fancy instruments, the rover found data suggesting the site was once habitable, home to flowing water with neutral pH, low salinity and various important elements for life like carbon, hydrogen, oxygen, sulfur, nitrogen and phosphorous. This means microbes known as chemolithoautotrophs, known to thrive in Earth’s caves and hydrothermal vents on a diet of chemicals, could have almost certainly lived in that ancient Martian lake.

Great news, sure, but it was a bit more impressive the first time. We’ve known about that particular ancient lake and its likely habitability for almost a year now. These new findings solidify the scientists’ suspicions of habitability and do provide a timeframe for the lake, suggesting it existed in habitable form for tens or hundreds of thousands of years.

Science is often iterative, and builds slowly upon itself — these findings are definitely important to other scientists and anyone extremely interested in Mars’ past habitability. But it’s also important to keep perspective on findings like this, too.

A graph compares radiation dosage on Mars with various earthbound sources.

Of the other five papers in the bundle, three deal with the minutiae of Curiosity’s geologic findings, one deals with a new method of dating the rocks on and just beneath Mars’ surface, and the final one reports on the radiation the rover’s received on the surface. This last one might also seem like another rehash of old news, but it is worth exploring briefly.

It’s easy to forget, but among Earth’s finer qualities is its ability to shield us from the hazardous radiation rampant in space, mostly from galactic cosmic rays and solar energetic particles. The journey to Mars would prove somewhat dangerous for humans on board any but the most heavily shielded vessel, and landing on Mars would only offer a minor improvement.

Curiosity’s Radiation Assessment Detector, after 300-odd days on the Red Planet, measured the total average radiation rate to be about 0.21 microgray per day (mGy/day), only about half the 0.48 mGy/day it picked up during the journey in space. (Measuring radiation is weird, but see here and here for pointers.) In total, the scientists now estimate the surface rate at 76 mGy/yr. That’s pretty high, but not intolerable, for humans and other life. Knowing this will help us plan for possible future Mars exploration (and put further bounds on the unlikely scenario of Martian life currently existing).

View the original article here

Thirteen New Answers to an Age-Old Physics Puzzle

Since the days of Isaac Newton, physicists have sought to describe all the possible ways that three objects can orbit each other regularly in empty space. Solutions to the “three-body problem” could predict the dynamics of real-life planetary and stellar systems. It is also a fiendishly difficult mental puzzle: In more than 300 years, physicists had found only three solutions.

Then last year, using computer simulations of three objects in motion, physicists Milovan Šuvakov and Veljko Dmitrašinovic from the Institute of Physics Belgrade found 13 new solutions. The researchers began by plotting hypothetical masses with specific locations and velocities, then simulated their possible orbits, looking for periodic orbits (ones that repeat). The simple-sounding procedure eventually yielded the new solutions (examples above).

If computer modeling proves such orbits are stable, it may be only a matter of time before astronomers discover these patterns among the stars.

[This article originally appeared in print as "Thirteen New Answers to an Age-Old Physics Puzzle."]

View the original article here