NASA’s Jupiter Mission

NASA’s Jupiter Mission[1]

Multiple images combined show Jupiter’s south pole, as seen by NASA’s Juno spacecraft from an altitude of 32,000 miles. The oval features are cyclones. (Credit NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles)

The top and bottom of Jupiter are pockmarked with a chaotic mélange of swirls that are immense storms hundreds of miles across. The planet’s interior core appears bigger than expected, and swirling electric currents are generating surprisingly strong magnetic fields. Auroral lights shining in Jupiter’s polar regions seem to operate in a reverse way to those on Earth. And a belt of ammonia may be rising around the planet’s equator.

Those are some early findings of scientists working on NASA’s Juno mission, an orbiter that arrived at Jupiter last July.

Juno takes 53 days to loop around Jupiter in a highly elliptical orbit, but most of the data gathering occurs in two-hour bursts when it accelerates to 129,000 miles an hour and dives to within about 2,600 miles of the cloud tops. The spacecraft’s instruments peer far beneath, giving glimpses of the inside of the planet, the solar system’s largest.

“We’re seeing a lot of our ideas were incorrect and maybe naïve,” Scott J. Bolton, the principal investigator of the Juno mission, said during a NASA news conference on Thursday, May 25, 2017).

Two papers, one describing the polar storms, the other examining the magnetic fields and auroras, appear in this week’s issue of the journal Science. A cornucopia of 44 additional papers are being published in the journal Geophysical Research Letters. The papers describe findings based largely on the first two close passes of Jupiter in which Juno was able to make measurements. Juno has now made five, with the next on July 11, 2017, when it is to pass directly over the Great Red Spot.

Scientists are puzzled to see that the familiar striped cloud patterns of Jupiter may be only skin deep. An instrument collecting microwave emissions probes the top layers of the atmosphere, but that data does not reflect what is seen in the clouds. “These zones and belts either don’t exist or this instrument isn’t sensitive to it for some reason,” Dr. Bolton said.

The microwave instrument did detect a band of ammonia rising in the equatorial region from at least a couple of hundred miles down—“the most startling feature that was brand-new and unexpected,” Dr. Bolton said.

In measuring the gravitational field, scientists hoped to learn what lies at the center of Jupiter. Some predicted a rocky core, perhaps the size of Earth or several Earths. Others expected no rocky core, but hydrogen, the planet’s main constituent, all the way down. “Most scientists were in one camp or the other,” Dr. Bolton said, “and what we found is neither is true.” Instead, the data suggests a “fuzzy core,” one that is larger than expected, but without a sharp boundary, perhaps partly dissolved.

The magnetic field is also not simple. “What scientists expected was that Jupiter was relatively boring and uniform inside,” Dr. Bolton said. “What we’re finding is anything but that is the truth.”

John E.P. Connerney, a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and the deputy principal investigator on the mission, reported spatial variations in the magnetic field that were much stronger than expected in some areas and much weaker in others.

The magnetic field is generated by the churning of electrically charged fluids at the core. On Earth, that comes from the convection of molten iron in the outer core. On Jupiter, the currents come from hydrogen, which turns into a metallic fluid under crushing pressures.

The spatial variations suggest that the dynamo of churning currents is larger than had been thought and may extend beyond the metallic hydrogen region, Dr. Connerney said.

For the magnetic field and gravity measurements, a glitch that has greatly slowed the pace of data gathering could turn out to be beneficial. A final engine burn last October was to put Juno in a 14-day orbit, but a pair of sluggish valves in the fuel system led mission managers to forgo that, and Juno remains in the 53-day orbit instead. The spacecraft is to make the same number of orbits and collect the same amount of data, and the longer mission means that Juno may be able to detect slow changes in the magnetic field.

More surprises were found at the top and bottom of Jupiter.

With Juno’s orbits passing almost directly over the north and south poles, scientists can better study the powerful auroras, which are generated by charged particles traveling along Jupiter’s magnetic field and colliding with molecules in the atmosphere. In Earth’s case, charged particles from the Sun speeding outward through the Solar System are diverted by the planet’s magnetic field toward the poles, generating light when they collide with air molecules. The expectation was that the same would occur at Jupiter, and it does to some extent.

But Juno also detected charged particles—mostly electrons—traveling in the opposite direction at Jupiter: out of the planet into space. “It’s a 180-degree turnabout from the way we were thinking about those emissions,” Dr. Connerney said.

He said a voltage differential in the atmosphere was drawing the electrons upward.

Earlier photographs of the polar regions were taken from a sharp angle, with details hard to make out. Juno revealed that the clouds there are very different from the usual Jupiter stripes. “What you see is incredibly complex features, the cyclones and anticyclones all over the poles,” Dr. Bolton said.

Planetary scientists had wondered whether Jupiter would have a giant hexagonal pattern like that spotted on Saturn by NASA’s Cassini spacecraft.

On Wednesday [May 24,2017], NASA released new images of Saturn’s north polar region, which has changed color in the last four years, possibly because summer has reached the northern hemisphere.

In the final stages of Cassini’s mission, which ends in September, it has shifted to a looping elliptical orbit, which will enable similar probing of Saturn’s interior.

“Eventually we will compare,” Dr. Bolton said. “We will really be able to advance our understanding of how these giant planets work.”

[1] Kenneth Chang, “NASA’s Jupiter Mission Reveals the ‘Brand-New and Unexpected’”, New York Times (May 25, 2017). A version of this article appears in print on May 26, 2017, on Page A20 of the New York edition with the headline: “Seeing the ‘Brand-New and Unexpected’ of Jupiter.”

Where Is Everybody?

Where Is Everybody?[1]

Perhaps my favorite essay in Aliens: The World’s Leading Scientists on the Search for Extraterrestrial Life is by the astrobiologist Lewis Dartnell, who patiently explains why aliens would not come here to have sex with us or eat us for supper.

I can only assume that he gets these questions a lot.

Here are the answers, should you find these possibilities concerning: The likelihood that we’d be genetically compatible with aliens is terribly remote, which means that they’d almost certainly be immune to our sexual charms. For similar reasons, having to do with biochemistry, we’d be lousy refreshments for them—they would almost certainly lack the proper enzymes to digest us.

As a bonus, Dartnell goes on to reassure us why aliens wouldn’t be especially interested in raiding our planet for raw materials, either (asteroids are a far easier source to mine); and if it were water they were after, they’d be far better off going to Europa, one of Jupiter’s largest moons, which contains more water beneath its icy shell than all the oceans on Earth combined.

If you’re interested in non-Earthly life, don’t look to the movies, is his point.

You could argue that that’s the general point of this modest, eccentric collection. Jim Al-Khalili, a quantum physicist and the editor of Aliens, opens with a question asked by Enrico Fermi in 1950: If the universe is so vast, and its age so old, and its stars so plentiful, where is everybody?

I’m no marketing expert, but “Where Is Everybody?” strikes me as a far catchier title for this book than the one it has, and it’s definitely more accurate. There really is nobody—so far—to write about. (Fighting words, I know. My hands hovered, spaceshiplike, for several minutes over the keyboard before committing that sentence to print.) This doesn’t mean that life elsewhere doesn’t exist. But it probably corresponds very little to what most of us have in mind, and not at all to the ooze-covered beasts of Ridley Scott’s electric dreams[2].

One of the most consistent takeaways from this anthology is just how banal extraterrestrial life might be. Often, when entertaining the possibility of aliens, what we’re really entertaining is the possibility of hardy microbes that can withstand extreme conditions, whether they’re thermophiles (heat lovers), psychrophiles (cold lovers) or halophiles (salt lovers). Read enough of Aliens, and you realize that the search for life is just as much about the most mundane aspects of biology as about the trippier questions of cosmology.

But it is also about philosophy. In this search, it helps to know what life is. Yet there’s no consensus about how to answer this question, strangely. (At the risk of being too Clintonian, it depends on what your definition of “is” is.)

Nor do we know how life began. At some point, the Earth made the transition from chemistry to biology, yes, but we cannot “agree on a definition that separates the nonliving chemistry from life,” as the geneticist Johnjoe McFadden puts it. (He then paraphrases the astronomer Fred Hoyle, who famously said that the odds of assembling something like a bacterium out of the primordial ooze were akin to the odds of a tornado’s assembling a jumbo jet out of a junkyard heap as it sweeps through.)

There are scientists who will go so far as to say that life is a spectacular fluke. Not everyone, mind you: Researchers now estimate that there are one billion Earthlike exoplanets in the Milky Way. “To my mathematical brain, the numbers alone make thinking about aliens perfectly rational,” Stephen Hawking has said.

But a powerful essay by the evolutionary biologist Matthew Cobb will make you wonder whether any form of multicellular life is far less likely than one in a billion. He points out that “there are more single-celled organisms alive on Earth than there are Earthlike planets in the observable universe”; that the number of single-celled organisms that have lived on this planet over the course of 3.8 billion years is beyond calculation; that these organisms have interacted “gazillions” of times (I love it when words of the appropriate magnitude desert even the experts). Yet we’ve never had a second instance of eukaryogenesis—that remarkable moment when one unicellular life form lodged inside another, forming something much more complex—in all this time.

Of course, there are researchers who dispute this theory and Cobb’s reasoning. But you get the idea.

The experience of reading almost any anthology is a bit like traveling across the country in a rental car with only an FM radio for company. Sometimes you get Sinatra; other times you get Nickelback.

This collection has its share of Nickelback. One of its most disappointing essays is about aliens in science fiction, which manages, against stupefying odds, to contain just one interesting insight: that authors tend to be more concerned with physics than with biology. (How did those gigantic sandworms evolve on the desert planet in Dune?)

But the best of these essays are far out in more ways than one. The very first, by the cosmologist Martin Rees, notes that our best hope for interstellar travel isn’t as humans, who don’t live very long and require far too much fuel to get very far, but as post-humans, who will have made the Kurzweilian transition from organic to inorganic, from decaying mortals to silicon-based, eminently portable machines. He adds that alien intelligence, if we ever detect it, will also be in this form.

The final essay, by Seth Shostak, a senior astronomer at the SETI institute (short for Search for Extraterrestrial Intelligence), goes even further, saying that if we really want to be attuned to alien life in the cosmos, it’s so likely to be in the form of machine intelligence that we ought to “be alert to apparent violations of physics.”

These forms of life may well be speaking to us even now. It’s just that our radio telescopes, which listen to the skies for signals from alien beings, can’t understand what they’re hearing. “Even if the search succeeded,” Rees writes, “it would still in my view be unlikely that the ‘signal’ would be a decodable message.”

It’s a whole new twist on George Berkeley’s question. The tree would fall in the forest. We’d hear it. But it would sound nothing like a tree.

[1] See Jennifer Senior, “‘Aliens’ Asks: If the Universe Is So Vast, Where Is Everybody?”, New York Times (May 24, 2017). This article is  review of the book: Al-Khalili, Jim(2007). ALIENS :The World’s Leading Scientists on the Search for Extraterrestrial Life. New York: Picador. Follow Jennifer Senior on Twitter: @jenseniorny. A version of this review appears in print on May 25, 2017, on Page C2 of the New York edition with the headline: “I Think It’s Gonna Be a Long, Long Time.” Downloaded May 26, 2017

[2] Scott is a South African born movie director of sci-fi films, including Alien, and The Martian.

Neutron Star Interior

Neutron Star Interior[1]

It is a rare opportunity when we can use astronomical observations to push the frontiers of physics in a way that is not possible in any laboratory on Earth. Yet neutron stars, the dead, dense remnants of massive stars, provide us with just that opportunity.

Crushed under the inward pull of gravity once a massive star’s fuel is exhausted, the stellar core that becomes a neutron star reaches matter densities that are not naturally encountered anywhere else in the universe. (Black holes don’t count: Although they may infinite energy densities, they hide behind horizons and are inaccessible). In fact, the matter that makes up neutron stars has fundamentally changed character, taking us into regimes that are still poorly understood in physics. As a result, a lot of recent efforts have focused on probing these stars’ interiors with astronomical instruments. To be sure, there are some aspects of that unusual matter that we can confidently predict, based on theoretical calculations and laboratory experiments. For example, during the implosion of the star, the electrons that normally surround he nucleus of an atom in the core get pushed into the atomic nuclei. There, they combine with the protons through weak interactions, one of the four types of interactions that take place between particles in the universe. (The other three are strong, gravitational, and electromagnetic.) That combination produces a neutron—thus giving this new star its name—as well as nearly massless, ghostly particles called neutrinos that rapidly escape from the star, carrying with them a large amount of energy the first observational confirmation of this process happened with Supernova 1987 observed in 1987 in the Large Magellanic Cloud (see S&T Feb 2017, p. 36), when two neutrino observatories detected a burst of particles around the same time as the supernova’s visible light appeared in the sky.

Scientists can’t create such neutron-rich matter. Simply smashing together and squeezing them to high densities in heavy ion colliders, such as the RHIC experiment in Brookhaven National Laboratory, doesn’t work. First, collisions in accelerators create very hot matter, which behaves differently than cold matter inside a neutron star. (It’s “cold” not because the temperature is low, but because the thermal energy is so small compared to the energies of other internal interactions that it’s unimportant.) Second, the weak interaction acts over a relatively long time-scale, much longer than the time that particles have to interact with one another when crushed against each other in a collider. Imagine that a plane were flying nearby, in the opposite direction to yours. You might have time to catch a glimpse of a passenger on that flight, but you certainly wouldn’t have time for a hearty handshake—even the if it were physically possible.

Still, if the creation of neutrons during the implosion were all that could happen to the core’s atomic nuclei, astronomers would by now consider the question of what lies inside a neutron star a solved problem. But transforming run-of-the-mill atoms into a super-dense soup of (almost) entirely neutrons turns out to be only the beginning of the particles’ journey.

The Fate of Collapsing Matter

As neutrons become squeezed further together in neutron star cores, they reach densities that are difficult to fathom While the star’s crust may look more or less like normal mater, the core can reach densities that are a hundred trillion (! that is 1014) times higher than the densest natural elements on Earth.

Under those conditions, neutrons not only start vehemently repelling one another but also interacting in new ways. This is because neutrons are examples of particles called fermions, which require increasingly higher energy to be confined closer and closer together. To counter this rising energy, neutrons may find it “energetically favorable”–basically less hassle—to dissolve into their even smaller constituents, called quarks, creating a quark soup. Alternatively, they may form different combinations of quarks than what normally make up a neutron or proton. Such hyper-nuclei, called hyperons, can be created in laboratories but survive only or a short time. In neutron stars, they might be stable.

Yet another possibility is that fermions pair up with one another to form a type of particle called a boson. These particles, which behave differently from fermions, can transition into an unusual superfluid state of matter (the same state that is observed in low-temperature helium fluids, superconductors, and some other metals, called a Bose-Einstein condensate). This sate will have strange properties, such as flowing without friction. If this transition indeed occurs inside the core—and we have good reason to think that it does—it will relieve some of the pressure built up by the high densities that mater experiences there.

But which of these possibilities actually take place in a neutron star’s interior? One of the things that complicate this puzzle is that, while we’ve observed hyperons and many types of bosons as standalone particles in laboratories, a quark has never been observed by itself, in what is called an “unconfined” state. Therefore, predicting and testing the behavior of quark matter becomes very difficult.

But if one could see into the cores of neutron stars and prove that they contain quark matter, it would constitute a major advance in our understanding of these smallest constituents of matter.

Probing the Invisible

How would astronomers go about probing the deep interiors of not only the densest but also the smallest stellar objects in the universe? At roughly 20 km across, neutron stars are smaller than some of the Solar System’s asteroids. Yet they pack into that tiny volume up to two times the mass of the Sun. And unlike asteroids, they are hundreds to many thousands of light-years away. It turns out that measuring the exact sizes of neutron stars, which can be done from a distance, provides the best possible tool for getting a complete picture of their interiors. Our calculations tell us that, if only neutrons remain in the interior, the pressure building up from the repulsive interactions will support a star of a particular size. If any constituents other than neutrons form, their interactions would cause a different amount of repulsion, creating a star of a different size. Thus, astronomers can discover the possibilities in the realm of physics simply by measuring exact diameters of these stars.

Astronomers are used to measuring the sizes of far-away objects by collecting and analyzing the light they emit. Indeed, nearly all our knowledge about the sizes of normal stars comes from measuring both the total light emitted by the star, referred to as its luminosity, as well as the breakdown of that emission into different wavelengths of light, known as its spectrum. The spectrum of the star allows us to determine its temperature; the hotter the stat, the higher the energy of the light that it emits. It’s this temperature that regulates exactly the amount of radiation that emerges from each patch of the surface, allowing us to determine the star’s intrinsic brightness. Comparing that to the total observed luminosity give us an exact measurement of the star’s surface area.

For neutron stars, the approach we take isn’t too different. So far, much of the information we’ve obtained about their sizes has come from nearly the same methods we apply to normal stars, but with a few complications. First off, it is difficult to see down to the surface of many neutron stars. This is because the majority of neutron stars that have ever been observed are enshrouded by strong magnetic fields (called magnetospheres), as well as energetic charged particles that swarm around in these fields like a cloud. These types of neutron stars are exciting in their own right, observable as the beautiful radio and gamma-ray pulsars that spin like lighthouses with exquisite regularity. However, it is difficult to see down to the star’s surface without being overwhelmed by the light emitted from the surface of the neutron star itself, we focus instead on those stars that have very weak magnetic fields, which allows the surface’s x-ray glow to shine through. Some of these stars are not pulsars at all, while others have very weak pulsar emission.

The second difficulty astronomers encounter in measuring sizes comes from the extremely strong gravitational fields neutron stars possess. Thanks to the vast amount of matter packed into such a small volume, a neutron star strongly bends space-time around itself and the path of the light that the star emits becomes significantly distorted. Indeed, the gravitational field is so strong that a neutron star hovers just this side of catastrophe—any denser, and it would collapse into a black hole.

What this means for measuring the size of a neutron star is that an extra step is required to map the observed light through its distorted path back to its origin. This procedure allows us to accurately account for every piece of the surface that contributes to the observed light and obtain a measurement of the entire surface area.

The results we have obtained to date with this method have been pretty striking: Neutron stars turn out than what we would predict if they were made up only of neutrons. More precisely, if none of the possible interactions that give rise to new particles or unconfined quarks take place in their cores, we would expect neutron stars to be 25-26 km across. The measurements point to 20-22 km instead. That may seem like a small difference, but it is in fact large: The central density of two such stars differs by a factor of two. This is enough to have a profound effect on the amount of repulsion the particles experience.

As with all scientific experiments, these results need to be confirmed with independent methods. So far, though, the measurements indicate that neutrons are taking at least one of the possibilities available to them to partially release the pressure valve. Which one, we’re still unsure. We need both additional, independent observations and theoretical investigations to find out.

Gravity to the Rescue

One of the powerful techniques that can reveal the sizes of a neutron star relies on the general relativistic effects that arise due to the star’s extreme gravity—the exact same effects that cause complications in surface area measurements. This time though, they come to our help We apply a technique known as pulse profile modeling to a special class of pulsars. In these sources, the magnetic fields that are anchored on the surface are weak enough that the swarm of particles around the star doesn’t overwhelm the light from its surface. Nevertheless, these magnetic fields are strong enough to guide charged particles toward the star’s magnetic poles, producing a hotspot where the poles meet the crust. As the star spins on its axis, the hotspots come in and out of sight, generating a characteristic pulse in the x rays.

Measuring the pulses’ shapes allows us to determine the size of the star that emitted them. This is because the amount that the light path bends as it leaves the surface of a neutron star depends on how large the star is. In other words, two neutron stars of the same mass but with different sizes, say 20 and 25 km, would create a different pattern of modulation in the light they emit. These patterns can be calculated very precisely and compared to the observed pulses, revealing the sizes of these pulsars.

We are poised to conduct this experiment with an instrument called the Neutron Star Interior Composition Explorer (NICER), which is scheduled for launch to the International Space Station (ISS) this year (2017). NICER is approximately a meter across and consists of carefully designated optical elements that focus the incoming x rays onto 56 silicon detectors. After its journey on a SpaceX resupply mission, it will be unpacked and mounted onto its home on the ISS platform. A star-tracker-based pointing system will then allow the high-precision x-ray timing instrument to point to and track pulsar targets over nearly half of the sky.

What makes NICER unique is its unprecedented capability to record the arrival times of incoming photons with 100-nanosecond precision. This capability will enable the highly faithful reconstruction of the pulse waveforms for a number of pulsars. The detectors will also capture the pulsars’ spectra. Coupled with the precisely determined pulse shape, these measurements will provide all the information necessary for a precise size measurement within a year after its launch.

Another exciting avenue into the neutron star interior will become possible through the detection of gravitational waves with LIGO. Even though the first two events detected by LIGO were coalescing black hole binaries, LIGO is also sensitive to signals from merging neutron stars (S&T Dec, 2015, p. 26). Shortly before the expected coalescence, the pair of inspiraling neutron stars start distorting and pulling each other apart through tidal interactions, obeying the same principles as the Moon’s effect on Earth’s oceans, but far more severe. How severe it is depends on how deformable the stars are, which in turn depends on their size, density, and interior composition. Remarkably, the distortions caused by these tidal interactions are then encoded into the gravitational wave signals that are emitted throughout the inspiral, offering one more penetrating glimpse into the neutron star interior.

If NICER and LIGO experiments confirm the existing measurements of small sizes, the results would point to new physics that emerges when matter becomes ultra-dense. Or the experiments may offer other surprises—that remains to be seen.

But no matter how small and impenetrable they may seem, neutron stars will not be able to hold onto their innermost secrets for much longer

[1] See Feryal Őzel, “The Inside Story of Neutron Stars,” Sky and Telescope (134, 1, 2017, pp. 16-21). Feryal Őzel is a professor of astronomy and physics at the University of Arizona and a current Guggenheim Fellow. She studies neutron stars and black holes and is a member of the NICER team.

Art and Science

Art and Science[1]

In 2001, a group of scholars packed into an auditorium at New York University to hear English artist David Hockney present his theory that since the Renaissance, many painters have used optics in their work. The photorealistic paintings of Dutch master Johannes Vermeer were among Hockney’s examples. To Hockney and his collaborator, optical scientist Charles Falco, Vermeer’s paintings bear the unmistakable signature of camera-like projection.

But many in the room had come not to praise Hockney for his insight, but to convict him of heresy. They were offended at the suggestion that the ineffable genius of revered artists might have benefited from anything so vulgar as lenses and mirrors. One museum curator insisted that Vermeer’s attitude had been, “To hell with physics!” Characteristically witty, writer and critic Susan Sontag likened the reliance of art on optics to the reliance of sex on Viagra.

The battle lines that day were drawn between what C. P. Snow called “The Two Cultures.” On one side are art and the humanities, expressions of the human spirit; on the other side is science, the haven of cold, dehumanizing rationality. “The Two Cultures” are stamped indelibly onto the zeitgeist of our times.

Personally, I don’t get it.

Listen to conversations among scientists, and you might be surprised to catch phrases like “playing with the data,” the “beauty of an experiment,” or the “elegance of a theory.” You might hear passion about intuition or the aesthetic that guides their work.

Trade lab coats for fedoras, equations for lead sheets, and scientific jargon for the esoteric language of jazz, and you might confuse the scene with a bunch of musicians taking five during a recording session! The distinction might blur further if the discussion turned to the technical side of making and recording musical sound.

In both cases, you would be witnessing the same thing: human creativity at work.

The notion of a gulf between science and art would have puzzled Leonardo da Vinci. He and others moved beyond received wisdom — and invented modern science — precisely by applying an artist’s creativity and careful eye to questions of how the world works.

All of which raises the question: If science and art are so similar — both human expressions of the creative drive to experience and comprehend the world — then why are they viewed so differently?

The answer lies in the jury process. Art finds its value in the subjective response of its audience. In contrast, many a beautiful scientific theory has been abandoned for the simple crime of making predictions that were incorrect.

Johannes Vermeer captured the light and details of The Music Lesson so perfectly that some wonder if he used optical aid. If he did, would that make him an art fraud or simply a different kind of genius?

Science can be uncomfortable because it says, “What you want doesn’t matter.” You might want astrology to work. You might want global warming to be a hoax. You can stomp your foot as much as you like and even get yourself elected to Congress. But that still doesn’t make it so. Some people have trouble accepting that.

Inventor and technologist Tim Jenison had a lot to do with bringing computer animation to the world—two Emmys’ worth. Turning revolutionary technology into revolutionary art is his life’s work. When Jenison heard about Hockney’s ideas, he was intrigued. But instead of opinion, Jenison saw Hockney’s work as a scientific theory to be tested. So he set out to do just that.

Jenison’s early experiments with a mirror on a stick grew into an obsession. After years mastering everything from polishing lenses to making his own paint, all using 17th-century techniques, it was time for his grand experiment. He would attempt to paint his own version of Vermeer’s masterpiece, The Music Lesson.

Day after day, month after month, Jenison devoted himself to the demanding and tedious work. One brush stroke at a time, he used his optical device to meticulously match pigments on canvas to light from the scene. When finished, Jenison’s painting was undeniably beautiful. It also perfectly captured the precise perspective and illumination that define Vermeer’s style.

Jenison’s remarkable story is chronicled in the delightful documentary film Tim’s Vermeer. Narrated by Penn Jillette and directed by his partner, Teller, Tim’s Vermeer has received widespread critical praise.

But many in the art history community are no happier with the idea now than they were in 2001. Jonathan Jones, writing for the Guardian, pulled no punches in his scathing critique. “At last,” wrote Jones, “an art film for philistines.”

Did Jenison prove that Vermeer invented and used a forerunner of modern copy cameras? No. But Jenison did successfully demonstrate an optical method that would have allowed Vermeer to produce the unique works of art that continue to marvel us to this day.

Immersed in the scientific and artistic excitement of the Dutch Golden Age, if Vermeer did invent such a powerful technique, why wouldn’t he have used it?

I enjoyed Tim’s Vermeer. At last, a film about science and art for those who insist they are two sides of the same coin.

[1] See Jeff Hester, “A False Dichotomoy,” Astronomy (43, 8, 2015, p. 14). Jeff Hester is a keynote speaker, coach, and astrophysicist. Follow his thoughts at jeff-hester.com.

The Mystery of Quasars

The Mystery of Quasars[1]

At left is a Hubble Space Telescope image of quasar 3C 273, showing the incredibly powerful, distant galaxy blazing as the central “star” in the frame. Material shot outward from the supermassive black hole in the quasar’s center is visible as a faint jet to the upper left of 3C 273

In the early 1960s, astronomer Maarten Schmidt had a problem. Along with other researchers, this fixture of the California Institute of Technology had been studying mysterious radio sources discovered in the 1950s.

These strange objects, the two most notable designated 3C 48 and 3C 273, appeared tiny on the sky but were extremely energetic sources of radio waves. They didn’t fit any logical explanation of what astronomers understood at the time. (The designation 3C came from the Third Cambridge Catalog of Radio Sources, produced at Cambridge University.)

A precise position of 3C 273, using the 200-inch Hale Telescope on Palomar Mountain in California, finally allowed Schmidt to record the object’s spectrum, the signature of its light, for the first time. This, in turn, produced a 1963 paper declaring that the strange radio object lay at the impressive distance of 2.4 billion light-years. Yet in Earth’s sky, the object appeared merely as a faint star, leading Schmidt to name this new thing a “quasi-stellar object,” or quasar.

How could something so far away be so incredibly energetic? At first, the notion completely baffled astronomers.

And then the mystery deepened. Over the years to come, astronomers found a series of strange, distant, highly energetic objects far beyond the Milky Way. Using a wide range of the electromagnetic spectrum, a rogues’ gallery of super-energetic, distant object emerged. They came to include quasars, Seyfert galaxies, BL Lacertae objects (or “blazars”), and radio galaxies. For nearly a whole generation, this array of weird objects seemed to represent a complex puzzle of the unrelated oddities in the astrophysical zoo.

Eventually, astronomers learned that these strange high-energy objects were similar beasts viewed from different angles. They were all some form of high-energy galaxy, called active galactic nuclei, with centers harboring supermassive black holes. Material cascaded around the black hole—but not swallowed—was slingshot outward for astronomers to see.

And the first step in resolving the mystery of quasars was complete.

[1] See David J. Eicher, “The Mystery of Quasars”, Astronomy (45, 5, May, 2017, p. 8).

A New Venusian Look-Alike

A New Venusian Look-Alike [1]

A new member of the exoplanet club is sparking excitement in the astronomical community. Angelo et al. published in The Astronomical Journal (DOI: 10.3847/1538-3881/aa615f) their discovery of an object 219 light years from Earth—Kepler-1649b — that is strikingly similar to our bright sister planet, Venus. With the help from the Kepler mission transit data and observations from the Mount Palomar Observatory in California, the team was able to analyze the flux of radiation onto the planet and the planet’s radius, concluding that the size and the amount of radiation it receives from its sun is consistent with the values for Venus. This Venus doppelgänger has a few notable differences, however. Kepler-1649b takes just nine days to orbit around a sun that’s one quarter the size of our own. The group noted that by default the planet must travel much closer to its pint-sized host star to receive the amount of radiation comparable to Venus. This might subject the planet to solar flares, coronal mass ejections, and large tidal effects, which can influence seasonality and geologic activity of the star. This Venusian look-alike is now on the research docket, to understand how it differs from Earth-like planets and what conditions might lead to habitability on a planet.

[1] See “Research News: A New Venusian Look-Alike”, APS News (26, 5,May , 2017, p. 1, 7)

Cassini’s Deep Dive

Cassini’s Deep Dive[1]

The recording starts with the patter of a summer squall. Later, a drifting tone like that of a not-quite-tuned-in radio station rises and for a while drowns out the patter.

These are the sounds encountered by NASA’s Cassini spacecraft as it dove through the gap between Saturn and its innermost ring on April 26, the first of 22 such encounters before it will plunge into Saturn’s atmosphere in September [2017].

What Cassini did not detect were many of the collisions of dust particles hitting the spacecraft as it passed through the plane of the rings.

“You can hear a couple of clicks,” said William S. Kurth, a research scientist at the University of Iowa who is the principal investigator for Cassini’s radio and plasma science instrument.

The few dust hits that were recorded sounded like the small pops caused by dust on a LP record, he said. What he had expected was something more like the din of “driving through Iowa in a hailstorm,” Dr. Kurth said.

Since Cassini had not passed through this region before, scientists and engineers did not know for certain what it would encounter. Cassini would be traveling at more than 70,000 miles per hour as it passed within 2,000 miles of the cloud tops, and a chance hit with a sand grain could be trouble.

The analysis indicated that the chances of such a collision were slim, but still risky enough that mission managers did not send Cassini here until the mission’s final months. As a better-safe-than-sorry precaution, the spacecraft was pointed with its big radio dish facing forward, like a shield.

Not only was there nothing catastrophic, there was hardly anything at all. The few clicking sounds were generated by dust the size of cigarette smoke particles about a micron, or one-25,000th of an inch, in diameter.

To be clear: Cassini did not actually hear any sounds. It is, after all, flying through space where there is no air and thus no vibrating air molecules to convey sound waves. But space is full of radio waves, recorded by Dr. Kurth’s instrument, and those waves, just like the ones bouncing through the Earth’s atmosphere to broadcast the songs of Bruno Mars, Beyoncé and Taylor Swift, can be converted into audible sounds.

Dr. Kurth said the background patter was likely oscillations of charged particles in the upper part of Saturn’s ionosphere where atoms are broken apart by solar and cosmic radiation. The louder tones were almost certainly “whistler mode emissions” when the charged particles oscillate in unison.

The dust particles create their own distinctive noises.

Upon hitting Cassini, the dust and a bit of the spacecraft vaporize in small clouds of ultrahot gas where electrons are ripped away from atoms and generate radio waves.

The actual physics is still somewhat contentious. “People aren’t really sure what they’re seeing,” said Sigrid Close, an associate professor of aeronautics and astronautics at Stanford.

Her idea, supported by laboratory experiments and computer simulations, is that the lighter electrons initially speed away faster, setting up an electric field that pulls the electrons back toward the ions, and then they oscillate back and forth.

Above is a picture taken of Earth through Saturn’s rings. The arrow points to Earth.

Similar radio frequency pulses are generated by lightning, she said.

For spacecraft closer to home, like commercial and military satellites in orbit around the Earth, this could be an important process to understand, because pulses generated by large dust strikes could cripple their electronic systems.

When Cassini passed through a faint Saturn ring in December, the dust impacts numbered in the hundreds per second.

With the knowledge that the gap between Saturn and its innermost ring is safe, Cassini does not need to use its antenna as a shield, allowing it to make additional scientific measurements.

During its second dive through the gap on Tuesday [May 2, 2017], another instrument, the cosmic dust analyzer, made the first direct analysis of the ring particles. The dust analyzer is able to record particles smaller in size than could have been detected via radio waves during the first pass. In addition, Cassini performed magnetic measurements that will help determine the length of a Saturn day. That is still a mystery, because Saturn’s clouds obscure how quickly the underlying planet is rotating.

Cassini got back in touch with Earth on Wednesday morning [May 3, 2017] and is sending the results of the second dive.

[1] See “The ‘[Sounds’ of Space as NASA’s Cassini Dive by Saturn,” New York Times (May 3, 2017)