Back in 1984, when he was a new hire at the Space Telescope Science Institute in Baltimore, David Soderblom got to thinking. STScI was—and still is—the science and operations center for the Hubble Space Telescope, which was then scheduled to launch in 1986. Soderblom suggested that a memento of some sort be aboard the space shuttle delivering HST into orbit—something, he recently told me, “to tie Hubble the man to Hubble the telescope.”
His first thought was a pipe. In photographs, Hubble always seemed to have a pipe pinched between his teeth, even when observing at the eyepiece of the 200-inch Hale telescope on Palomar Mountain—or at least when posing at the eyepiece. Soderblom contacted Allan Sandage, the onetime assistant of Hubble who, upon Hubble’s debilitating heart attack in 1949 and death in 1953, became his de facto heir at the Mount Wilson and Palomar Observatories (now the Carnegie Observatories) in Pasadena. Sandage told Soderblom he had a better idea. What about the photographic plate with which Hubble had made the discovery that essentially began modern cosmology: that our vast menagerie of stars is not alone but is, as we now know, merely one among billions of galaxies clouding the universe as far as even HST would be able to see?
This anecdote was part of an STScI press release distributed at this past May’s meeting of the American Astronomical Society, in Boston, to accompany a presentation of a series of observations by Hubble-the-telescope commemorating this discovery by Hubble-the-astronomer. But, as Soderblom and I found during a conversation a couple of weeks ago, there’s more to the story.
To begin at the beginning:
On October 4, 1923, while observing with the 100-inch Hooker telescope on Mount Wilson, Hubble took a photograph of the Great Andromeda Nebula, or M31 in the classification system of 103 nebulae that Charles Messier published in 1781. (Messier was trying to help astronomers distinguish between smudges and comets.) Hubble thought he noted a “nova,” or new star, so he returned to M31 the following night and took a 45-minute exposure of the same spiral arm. When he got back to his office, he began comparing the new plates with other photographs of the nebula on a number of different dates and found that the nova was actually a variable, a kind of star that, as its name suggests, varies: It pulsates, brightening and dimming. More important, it was a Cepheid variable, the kind of variable that brightens and dims with clockwork regularity.
A Cepheid variable was what Hubble was hoping to find. In 1908, the Harvard astronomer Henrietta Swan Leavitt had discovered a proportional relationship between the pulsation period of a Cepheid variable and its intrinsic brightness: the longer the period, the brighter the variable. If you know how often a variable pulsates, then you know how bright it is relative to other variables; if you know how bright it is relative to other variables, then you know how distant it is relative to other variables. When Hubble compared the pulsation period of the Cepheid variable he’d found in M31 with the pulsation periods of other Cepheid variables, he concluded it was at sufficient distance that it (and therefore its host nebula, M31) lay beyond what astronomers of the day called “the island universe”—or, as they would now have to reconceive it, our island universe, the Milky Way galaxy.
Hubble went back to H335H, the photographic plate he made on the night of October 5 to 6, crossed out the “N” he’d used to designate the “nova,” and added a celebratory “VAR!” In doing so, he created one of the iconographic astronomical images of the twentieth century.
It was this relic that Sandage, at Soderblom’s behest, delivered to NASA in the mid-1980s.
But the idea of launching a historic photographic plate into space didn’t sit well with Soderblom (and he suspected that sending unnecessary glass into space wouldn’t sit well with NASA). So he suggested photographing the plate, producing fifteen negatives, and sending ten aboard for later distribution as tokens of thanks to sponsoring organizations. The negatives would travel in official flight kits—the facilities where NASA stores keepsakes. In 1990, the space shuttle Discovery loosed HST into orbit and returned to Earth with its “VAR!” cargo intact.
Then, disaster. The imperfections in HST’s primary mirror made the observatory a global laughingstock, and its cache of accompanying commemorative mementoes—the miniature flags and patches and pins, as well as Soderblom’s negatives—an afterthought.
About four years ago, Soderblom got to thinking about the upcoming fifth and final servicing mission to HST. And he got to thinking about those ten negatives. Maybe he could locate them and store them aboard the space shuttle that would be visiting HST one last time. He liked the “symmetry” of the negatives flying aboard the first and final HST shuttle missions.
By this time, of course, HST’s early ignominy was nearly forgotten. So too, alas, were the negatives. Soderblom contacted the person at the Johnson Space Center in Houston who was in charge of official flight kits. She said she would have to check the vault.
“Okay, that’s cool,” Soderblom thought. “I’ve got a desk drawer. She’s got a vault.”
The search, however, came up empty. Still, Soderblom figured, he at least had the remaining five negatives. He arranged to store two aboard Atlantis during the final mission to HST, in May 2009.
But then Soderblom got to thinking yet again. What if Hubble-the-telescope observed what Hubble-the-man had photographed on a fateful October night in 1923—the celestial object that astronomers call Hubble variable number 1, or V1? Locating V1 would be difficult and time-consuming, so the Hubble Heritage Project appealed to the American Association of Variable Star Observers (AAVSO). Between July and December 2010, eleven amateur astronomers made 214 observations of V1, allowing the Hubble Heritage team to target the variable at its brightest and dimmest phases: December 17, 21, and 30, and January 26—the achievement that Soderblom, the Harvard historian Owen J. Gingerich, and representatives from the Hubble Heritage Project and the AAVSO celebrated at the May meeting of the American Astronomical Society.
End of story? Not quite. When Soderblom and I spoke by phone earlier this month, he said he had a question. We were talking because we had heard through a mutual friend that we both had an interest in the “VAR!” plate. Soderblom wanted to know if I had actually held the plate in my hands.
Yes, I said. In May 1999, I was interviewing Sandage in his office at Carnegie Observatories when he reached into a file cabinet and produced the plate.
Soderblom said he had another question. Was the scrawled “VAR!,” as he’d often heard, actually in red ink?
“That’s really interesting,” he said, italics hardly doing the drawn-out word justice.
First, he said, this information confirmed for him that he’d never held the plate himself. Over the decades his memory had lost track of how the plate had arrived—whether Sandage had delivered it to STScI in person or through a courier (the U.S. Postal Service?!, he sometimes scared himself, retroactively). But now, he said, the red—the red he would have remembered.
This fact, however, also helped him understand an issue of greater historical import. Hubble had written “6 – Oct 1923” below “VAR!,” yet the custom at the time was to write such information on the opposite side of the plate, along the border. And indeed that’s where Hubble had written the date—though the date he wrote there and in his notebook was Oct. 5, reflecting Pasadena time. The “6 – Oct” inscription followed the astronomical convention of using Universal Time, or Greenwich Mean Time, but to an astronomer’s eyes it would have been, Soderblom said, “redundant information.” Hubble, he had always suspected, must have written it there “for display purposes”—a hunch, he added, that Hubble’s use of posterity-radiant red for “VAR!” certainly supported.
“In red, he wrote it,” Sandage had said. ”He knew reporters were going to come and look at this.”
Soderblom and I laughed. I’d never noticed the incongruity of the placement of the date. He’d never been sure about the red. Not that either piece of information changes the historical record regarding the science.
But together they do leave little doubt: Hubble the man was, in the end, only human.
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Credits (top to bottom): ESA/Hubble & Digitized Sky Survey 2 (acknowledgment: Davide De Martin, ESA/Hubble); Mt. Wilson Archive, Carnegie Institution of Washington; Carnegie Observatories; Carnegie Observatories; NASA, ESA, and the Hubble Heritage Team (STScI/AURA).