Several years ago, the organization that allots time on the Hubble Space Telescope asked astronomers to propose some long-term, mind-expanding projects that the HST might complete during its lifetime. Astronomer Julianne Dalcanton talks about how her team’s winning proposal—a staggeringly detailed portrait of the Andromeda Galaxy—came to be.
I was already used to thinking big with the Hubble, but this was like asking, ‘what’s the coolest thing you can possibly think of?’ One of my closest collaborators and I were talking on the phone about some of our crazy ideas. Somewhere during the conversation I said, ‘What if we did M31 (The Andromeda Galaxy)?’ The more we thought about it, the more we became convinced that this would be something transformative.
We are used to looking at galaxies as whole. But each galaxy, as Carl Sagan told us, holds billions and billions of stars. And if you look at it closely enough—as we could with the HST—you should be able to see the stars within it. Those stars are a ‘fossil record’ of everything that happened to the galaxy in the past. Through that record, we can figure out long-past events that we couldn’t witness directly. It’s almost identical to archaeology.
As for the image itself, well, I think ‘jaw-dropping’ is as close as you can get. I mean, when you write a proposal, you do a good job of convincing yourself that this is something that’s going to work. For me and my collaborators, there was a gobsmacking moment of, ‘This is as incredible as we thought it would be!’—and a tremendous relief that it actually worked.
For me, the most compelling reactions are the people whose first gut reaction is, ‘There’s no way we’re alone.’ I find that incredibly profound. I mean, you can tell people there are billions of stars in other galaxies. But when people actually see those billions of stars scrolling by on their computer screen, the idea that not one of them ever developed life starts to seem a little farfetched.