What exactly do they mean by “colder than Mars”? Mars is a planet—one that, like Earth, has an atmosphere, albeit thin, and weather and seasons. Mars can get as cold as –143°C (–226°F) and as warm as 35°C (95°F) in spots. Mars’s mean temperature is –63°C (–82°F), which is colder than just about any population centre can get (and no, wind chill doesn’t count for this). So that can’t be it. (Besides, comparing a mean temperature to a local temperature would be an apples-to-oranges comparison. Earth’s mean temperature, for the record, is 15°C.)1
It turns out that what reporters really mean is the current temperature at Gale Crater, as measured by the Rover Environmental Monitoring Station on the Curiosity rover. It also turns out that there’s a handy widget that gives the current conditions as measured by REMS. As I write this, the air temperature on Mars is –19°C and the ground temperature is –6°C (the difference is because the air is so thin).
Since it’s –19°C right now where I live, yes, Mars—or at least Gale Crater, which is not the same thing (again: apples to oranges)—is just as cold. But temperatures as high as 20°C (68°F) and as low as –127°C (–197°F) have been recorded at Gale Crater. It’s no trick for a Martian summer to be warmer than a Canadian winter, but even the daytime highs of a Martian winter can be warmer than a Canadian winter. Because the air is so thin, the Martian surface heats quickly when it’s sunny, and the temperature can swing as much as 100 degrees.2
I know that hyperbole is an essential part of talking about how goddamn cold it is out there (see also: using wind chill instead of temperature), but honestly, Mars isn’t a useful point of reference.
So I mentioned that I might try to get a photo of the solar eclipse, weather permitting? In the end, weather permitted — in fact, everything that could have prevented us from observing or photographing the eclipse failed to do so: clouds were intermittent until after the maximum, the tall trees around our house didn’t block our view, and we were even able to find all the gear we needed in time (some hadn’t been unpacked yet).
I used my usual method for photographing the sun: a digital SLR connected to my 5-inch Schmidt-Cassegrain telescope at prime focus, using a visual solar filter. It turned out well: despite the heat (atmospheric shimmer, you see), the filter (Mylar) and the need to focus manually, I managed more than a few clear shots. Above is a shot from the eclipse’s maximum extent (it was a partial eclipse here). I’ve uploaded a few other photos here.
You know, I think this is the first time I’ve done any solar observing or photography in more than five years. I’m glad I found an excuse to do it again.
I’m outside the path of totality for next week’s solar eclipse, but don’t feel bad for me: I’ve already had my total eclipse experience. I had just turned eight years old when the total solar eclipse of February 26, 1979 came to my home town of Winnipeg, Manitoba. In 2009, I remembered the event in a blog post:
Some people spend thousands of dollars to see a solar eclipse; I was lucky: the eclipse came to me. But to see it, I had to stay home from school that morning. My father’s recollection is that for some nonsensical reason or other, the schools were going to keep the kids inside during totality. Screw that, said my parents, who had three science degrees between them. So I saw the last few seconds of totality from my front porch.
Since then, video of CBC Manitoba’s coverage of the eclipse has been uploaded to YouTube (see above). I remember watching this. (Even weirder, the meteorologist showing the satellite image at the start of the coverage is a friend of the family.)
If you’re in the path of totality, enjoy the eclipse on Monday (weather permitting). As for me, I’m going to be all nostalgic about the one I already saw.
(I think I might try to get a photo of the partial eclipse—again, weather permitting. I do have the gear for solar photography.)
The Harvard Computers, ca. 1890. Wikimedia Commons.
On December 25 the American astronomer Vera Rubin, whose discovery that galaxies were rotating too fast given the mass of their constituent stars provided evidence for the theory of dark matter, died at the age of 88. Her obituaries note the challenges Rubin faced as a pioneering woman in an overwhelmingly male field: prevented from doing graduate work at Princeton, she got her Ph.D. at Georgetown in 1954; in 1965 she became the first woman allowed access to the Palomar Observatory. In the June 2016 issue of Astronomy, Sarah Scoles decried the fact that Rubin’s discovery was somehow insufficient for a Nobel Prize, which she will now never win.
Inasmuch as Rubin was a pioneer, she was not the first woman in astronomy, nor the first to obtain a Ph.D., nor the first to be responsible for a discovery that fundamentally reshapes our understanding of the cosmos — nor the first for whom recognition was unfairly delayed. Some of the women who came before her are the subject of Dava Sobel’s new book, The Glass Universe, coincidentally out this month from Viking.
From the 1880s to the 1980s, the Harvard College Observatory amassed a collection of half a million glass photographic plates of the night sky, and catalogued hundreds of thousands of stars’ luminosity and spectra. The work, along with some significant scientific discoveries, was largely done by a group of women known as the Harvard Computers. If you watched Cosmos: A Spacetime Odyssey, you saw a bit of this in the eighth episode, “Sisters of the Sun,” which talked about the computers, especially Annie Jump Cannon, as well as Cecilia Payne, who used the computers’ data to redefine our understanding of the makeup of stars.
The Glass Universe charts the history of the group, from the bequest by Henry Draper’s widow, to Observatory director Edward Charles Pickering’s decision to hire women to do the work (less expensive), to the achievements and discoveries that followed. It’s not a scholarly work, though it’s assiduously researched, drawing on the correspondence of the principal figures. Nor is it an explicitly feminist analysis, or for that matter strictly focused on the women themselves, as the narrative takes the reader far and wide, to remote stations in Peru and South Africa. Sobel (whose previous work includes Longitude, the story of Harrison’s chronometers) provides context, and a whole history, to help us understand not only who these women were, but what they accomplished.
The sheer volume of data collected — Pickering agonized over losing the irreplaceable glass plates to fire — was the basis not only of the Bright Star Catalogue and the Henry Draper Catalogue (if you see a star identified by a number with an HD prefix, that’s where it came from), but of the discoveries that resulted from the mass of data collection, and the fact that the principals stayed at their work for decades, building up a wealth of experience and perspective at, frankly, graduate student pay rates.
It is a paradox of popular culture that while the women of the Observatory who made these discoveries received credit for their work — first in acknowledgements in Pickering’s own work, later as co-authors and authors in their own right, and in the honours they eventually received from their peers (though not, it must be said, from Harvard University itself) — their names have not penetrated the popular-science zeitgeist to the same extent as, say, Hubble’s, Lowell’s or Tombaugh’s. You might argue that stellar spectra are a more rarefied subject, but I’d counter that (a) we know who Hubble is, and his discoveries are a direct consequence of their work; and (b) I knew what their discoveries were, I just didn’t know who made them.
I knew, for example, about the system of stellar classification based on stellar spectra (“Oh Be A Fine Girl Kiss Me” and all that), but I didn’t know that it was developed by Annie Jump Cannon — as a compromise between earlier systems devised by Williamina Fleming and Antonia Maury. Classifying stars was long, tedious, repetitive work — women’s work — but it was vital, and enduring.
I knew what a Cepheid variable was, and how the relationship between its pulsation and its luminosity allowed it to be used to calculate interstellar (and later intergalactic) distances; I didn’t know that this relationship had been discovered by Henrietta Swan Leavitt. And it was Cecilia Payne (later Cecilia Payne-Gaposchkin) who determined that Cannon’s spectral classes were a function of temperature, and that stars were mainly made up of hydrogen and helium. These are fundamentals of stellar astronomy, and these women were the ones who discovered them.
I’m trying to reconcile the hostility Rubin faced with the relatively warm reception given the women of the Harvard College Observatory. It’s possible that Rubin’s obituaries and Sobel’s book are each reporting a different side of the same coin: the story in both cases is incomplete. But the women of the Observatory were likely seen as exceptional, which is to say exceptions, and as such less of a threat to the profession. In any case, the field needed their work, their data and their discoveries, and was happy to have it. And in the end, the Harvard Computers, once referred to as “Pickering’s Harem,” managed to transcend what in science is called the “harem effect” — the hiring of large numbers of female subordinates at lower pay — to reshape our understanding of the stars.
As hobbies go, astrophotography has murderously high barriers to entry in terms of equipment costs and skill, and the money and time required to acquire each. Fortunately there’s an exception. Taking pictures of the Moon requires neither specialized equipment or skill: my first photo of the Moon was taken with an entry-level digital SLR and a telephoto zoom lens, and people have used smartphones to take decent photos of the Moon through the eyepiece of a telescope.
From that first shot I graduated to prime focus lunar photography, using adapters to connect my SLR to a telescope, making that telescope essentially a gigantic telephoto lens. Here’s an album of those prime focus photos.
Let me say at the outset that beginners should stay as far away from this book as possible (they should start with the advice in The Backyard Astronomer’s Guide). This is a comprehensive reference that covers every available way for amateurs to capture lunar imagery with their own equipment, and it does so in a systematic fashion. In method it’s not at all dissimilar from Michael Covington’s Digital SLR Astrophotography (from the same publisher), but for some reason I found the Covington easier to follow than the Dupont-Bloch.