[SHIMMERING MUSIC PLAYS]
>>ASHLEY PAGNOTTA: In astronomy, things either happen almost instantaneously,
or over tens of thousands, millions of years.
But one of the things that we’re starting to learn is that the things
that we previously thought were constant over a hundred years, we’re seeing changes over
decades—essentially the course of a human lifetime.
My name is Ashley Pagnotta. I am a Kathryn Davis postdoctoral fellow at the Museum of
Natural History. I research stars that explode and I teach future teachers.
[SHELF LIFE THEME MUSIC]
>>PAGNOTTA: One of the differences between natural history collections and astro collections is that
becuase ours live on hard drives, instead of in cabinets, they take up a whole lot less room.
Theoretical and computational astrophysicists run these enormous simulations. So, their collections
are the outputs of those simulations.
For me, because I’m an observational astronomer, my collections are images.
Now, when we take pictures of the sky, we use basically digital cameras. Before we had
that technology, we used glass plates that were coated with a photo emulsion. They would
be put onto the end of the telescope, exposed like film, and then developed. And the advantage
of this was that they, for the first time, had an objective record of what the sky looked like.
The Harvard Plate Collection is the largest in the world—about half a million glass plates.
They date all the way back to 1890. Harvard had telescopes all over the world,
and they would do what we call sky patrol—basically, take pictures every night in an organized
fashion so they could cover the whole sky. And then they would regularly repeat that,
so they could look for things that were changing.
>>MICHAEL SHARA: Once we had a permanent record on photographic plates, we knew that we could go back
a week later, a year later, a century later, and in some sense, recover what galaxies, stars,
and so on were like during those observations.
My name is Mike Shara. I’m a curator of astrophysics here at the American Museum of
Natural History. What I do is exploding stars.
I can’t send a time machine into the past. We simply have one record of the universe
streaming by us, and because the astronomers a century and more ago were snapping pictures,
we have a continuous record over an enormously long period of time.
It’s a completely unique history and digitizing their collections is very, very high on the
wish list of most of the world’s astronomers.
>>PAGNOTTA: Harvard has started a scanning program and here at the Museum, we’re also working to
help bring the plates into the modern era and to make them more available to us, for
the science that we want to do, but also to the broader astronomical community.
So, one type of star that I’m interested in is called a Cepheid variable, and these
were discovered by Henrietta Leavitt who worked at the Harvard Observatory in the early 1900s.
She realized that you can use these Cepheid variables to measure distances.
Which is really useful because we can’t just stretch a yardstick halfway across the galaxy.
Leavitt in the early 1900s compiled a catalog of all these variable stars in the Large and
the Small Magellanic Clouds—mini-galaxies that are actually gravitationally bound to
our galaxy, the Milky Way. Later in the 1950s and ‘60s, Cecilia Payne-Gaposchkin updated
Henrietta Leavitt’s catalog. So, we have these two fantastic catalogs that are crucial
to measure distances.
But we went to look for them in our modern digital catalogs of stars and they weren’t there.
So, what we decided to do with a couple of groups of high school students who work
here through what we call the SRMP program—the Science Research Mentorship Program—was
to update those catalogs.
>>JULIA KRUK: My name is Julia Kruk
>>ZACHARY MURRAY: I am Zachary Murray. We participated in the SRMP program.
Essentially, they were taking pictures of the sky and printing them on photographic
plates, and then Henrietta Leavitt used an X-Y coordinate system to chart the locations of the stars.
What we start with is a sheet with columns of numbers on it. But these positions were
only valid for the era in which she did her observations.
>>KRUK: We had to make sure that it was accurate so we could find these stars today.
>>MURRAY: So, in order to correct that, we converted those X-Y coordinate positions
to modern spherical coordinates.
>>PAGNOTTA: But they weren’t quite as modern as we use today. Because the Earth kind of wobbles on
its axis, that means where we see the stars changes very slightly over time.
So, the next step was they had to do what we call precess them all the way forward.
So, they actually wrote a computer program to get modern coordinates.
>>KRUK: We’re publishing this data and making it available to the astronomical community—
a century’s worth of data in one location.
>>SHARA: It’s one thing to collect and to generate data. It’s entirely another thing to make
sense of it. And that’s what makes it more and more scientifically valuable. By involving
a team of students who are willing to get their hands dirty and look at the data, we
begin to train the next generation of scientists and at the same time, selfishly, we get something out of it.
>>PAGNOTTA: Once this catalog is complete—and it’s almost finished—we will have a digital,
fully accessible catalog that anyone in the world can use. And then from there, you can
start to do science—see how do these stars change over time. We think that they probably
do change over 100 years, but we don’t really know what they do. Nobody’s ever looked before.