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Rene Magritte,
The Son of Man, 1964

The startling juxtaposition of galaxies in NGC 3314 reminds me of a well-known painting, Rene Magritte's The Son of Man. In a radio interview, the Belgian surrealist was asked about his work's iconic imagery. "Well, so you have the apparent face, the apple, hiding the visible but hidden, the face of the person," Magritte replied. He elaborated:

"We always want to see what is hidden by what we see. There is an interest in that which is hidden and which the visible does not show us. This interest can take the form of a quite intense feeling, a sort of conflict, one might say, between the visible that is hidden and the visible that is present."

It may seem strange that Magritte would draw such a distinction between the visible-present and visible-hidden. Shouldn't saying something is "visible" imply that it isn't hidden? But I suspect many astronomers I know might find Magritte a kindred spirit; might notice that he expresses a familiar notion. If you follow Magritte's words, he might as well be describing the psychological and philosophical pressures driving the project of science — and especially astronomy.

Astronomers, scientists, and generally curious people always want to see what is hidden by what we see. Always. Of course astronomers want to see through obstacles. When Hubble observes a dark pillar of interstellar gas and dust these days, astronomers aren't satisfied. Instead, they're itching for the James Webb Space Telescope to hurry up into space so it can stare straight through that pillar like the infrared-sensitive alien from Predator. In a further sense, an ideal scientist strives to hold up her own biases to the spotlight. She wants to acknowledge the unstated assumptions, the trappings of her paradigm, and to make sure they don't obscure or distort what she studies.
NGC 3314 by Hubble Heritageb(WFPC2)

Magritte isn't spewing art-speak gibberish, and isn't spinning an emperor-has-no-clothes story that you have to pretend to find deep or risk looking stupid. Instead, Magritte is describing the liminal space at the margins of our comprehension. He hints at an eye behind the green apple, which hints in turn at something more, producing an undeniable interest... a quite intense feeling, a sort of conflict. Astronomers, forever poring over scraps of light from the distant cosmos, know this feeling well. To study the faintest and most faraway galaxies in the Hubble Deep Field, they strove to dredge the depths of the observable universe. In pushing to detect the tiny wobbles an extrasolar planet might impart on its star, they've practically turned their solid-state detectors upside-down and shook them, waiting for every last significant photon to fall out. At its best, science operates at this tantalizing frontier, but I think Magritte's art does a good job of distilling what drives us to go there — and beyond.

Astronomy is rife with examples of the same thing seen in NGC 3314 and depicted in The Son of Man: some object positioned in front of something else. Sometimes this obscuration is ordinary. For example, astronomers are forever worried about "extinction," the dimming of starlight as it passes through interstellar dust clouds before reaching our telescopes. But the more fascinating cases are when the obscuration is anomalous, freakish, accidental. NGC 3314's superposition of two galaxies is striking on its own, but it stands out because of how unique it is. We observe untold millions of spirals in the sky, but they aren't usually stacked up perfectly like this. I see this kind of rare spatial alignment as deeply similar to rare temporal alignments: events that unfold on human time scales.
Venus March

These fated but infrequent alignments are often opportunities for exciting research. In 1919, Arthur Eddington used a solar eclipse to measure how stars very near the disk of the sun appear to slightly shift in space. His observations supported the general theory of relativity, making Albert Einstein a household name. Today, planets around other stars are studied through their "transits." When a planet crosses in front of its host star from the Earth's perspective, we observe the star dim as the planet blocks some of its light. Even now, the Kepler mission is using this method to discover planets analogous to Earth. Another example is the recent transit of Venus.

Venus crosses the sun once in a while, a fact that humans — with our sensible reservations about staring at the sun — have only figured out in the last few centuries. But since we calculated that the time separating every other transit is over 100 years, we've been determined not to miss them when we have a chance. Remarkably, each epoch of transits has been exploited to answer current, pressing questions about our universe. In 1761 and 1769, observations of the transits from different positions on Earth were used to measure the crucial distance between the Earth and the Sun. In the 1800s, higher-quality observations made this calculation more precise. John Philip Sousa was so excited about the contributions American scientists made to this endeavor that he did what I assume Sousa always did when he got excited: he wrote a march. By 2012, in a funny twist, astronomers were observing the transit of Venus not as a universal benchmark but as a proof-of-concept check on the observations of transits around other stars. So the Venus transit, too, has lent itself to cutting-edge science.

Venus Transit 2012
(Images courtesy of Z. Levay)

Images COuresy of Zolt Levay

Of course, the science is only part of the story. On June 5th, 2012, I attended a public viewing of the Venus transit. To be honest, as I gawked at that tiny black disk against the sun, I wasn't thinking about the science at all. My inner monologue, condensed: "this is just really, really cool, by itself, but especially because of how rare this is." I spoke to my dad on the phone about it later — I had directed him to watch the event through a streaming video from NASA, and he had complied. He's not a scientist, but we are both sports fans, and I needed to communicate that sense of rareness, almost sacred special-ness I had felt. "You know how Wilt Chamberlain scored 100 points against the Knicks?," I asked. My dad claims to have followed the historic, unmatchable feat on the radio in 1962; I strongly suspect that his recollection is faulty. He replied yes. "Well," I said, " this is a lot like that. They're both generational, even once-in-a-lifetime events."

A day later, at lunch with friends, I spun those feelings in a different direction. I pitched a business idea. In 50 years, assuming eccentric billionaire (and Virgin Galactic founder) Richard Branson has made space travel convenient, why not host a luxury "celestial alignment" cruise? You could zip high-rollers around the solar system, lining up obscurations like dominoes and then knocking them down. Imagine lounging in the shade cast by Saturn. Imagine seeing Titan eclipse Enceladus, the Galilean moons silhouetted against each other... or just the boring old transit of Venus again. But I wondered: if you could do all that, would it still be special?

NGC 1376, a rough approximation of what NGC 3314A might look like.y

My musing led me to an obvious but profound truth: it matters that our position is fixed. Historically, the simple issue of the sky's unfathomable depth has been one of the most vexing problems in astronomy. We can measure positions in the sky, but establishing knowledge about distances has been trickier. The Greeks knew that the Earth moved in space as it orbited the sun, so that if you measured the sky once and then half a year later, you should see a small angular shift in the positions of nearby stars. The size of this shift would let you calculate how far away the stars were. But this effect was so vanishingly small, so difficult to measure, that no one succeeded at seeing it until Friedrich Bessel finally did in 1838. Even the distances between galaxies — then "spiral nebula" — were so unknown that until the 1920s some astronomers believed the Milky Way might encompass the entire universe. So here we are, with the clockwork of the cosmos whirring all around us, and we can't even move around to take a look at everything!

NGC 3370, a galaxy with the same general shape and orientation as NGC 3314B.

We can't tilt our telescopes to the side so that the two galaxies in NGC 3314 edge away from each other in our line of sight. We can't reach out and snatch away Magritte's apple to see the face behind it, and perhaps this teases us enough to draw us in closer. We can't (yet) leave Earth and move freely through the universe, much less our own solar system. But Magritte rightly notes that the obscurations we face are provocations, opportunities. Being fixed doesn't stifle us. It inspires us, motivating us to take great advantage of those rare moments when things do come together, when the planets align, and when groundbreaking work is possible. And it forces us to appreciate these moments aesthetically all the more.

The overlap of NGC 3314 A and B doesn't promise a huge scientific payoff, but it is a breathtaking, arbitrary phenomenon with both Copernican and anti-Copernican resonances. The Copernican Principle holds that our perspective is average; that humans are one species on an unremarkable planet in an unremarkable place in the galaxy. Clearly, NGC 3314 is a quirky curiosity, but there's no higher meaning to it. But this cuts another way. In the vastness of our universe, even the unlikely becomes inevitable. Even in an unremarkable place, thanks to probability and large-number statistics, we are guaranteed to see remarkable things once in a while. And sometimes, these things are special because of our unique vantage point, not just in spite of it.

So in one corner of a sky full of intricate spiral galaxies, we happen to see this spectacular superposition. And in a season where he's averaging a Herculean 50.4 points per game, Wilt Chamberlain just might jump up through a few standard deviations and drop 100.

Venus Transit Sunset Image courtesy of S. Goebel.