Going to the weekly meetings of the Boston University Astronomical Society (BUAS) has definitely become the highlight of my Wednesdays since my first observing session back in September. Even though Boston isn't the best place for stargazing, we can see the moon and planets pretty well, especially through the large telescopes. The university's Astronomy Department recently decided to take advantage of the crowds that come for Public Observing Night by holding lectures one Wednesday a month about the research they do.
The rain and fog this Wednesday made observing from the roof impossible. (Although, given the weather's habit of messing with astronomers, Thursday was absolutely perfect.) Luckily, however, post-doc Jonathan Foster from the university's Institute for Astrophysical Research was still slated to give a presentation at 7:00.
I arrived at 6:30 for the usual half-hour meeting. We chatted about astronomy news, especially the latest exoplanets discovered by the Kepler space observatory, how long it would take us to travel there to them if we could turn ourselves into light, and how it would seem like much longer to ordinary people watching on Earth.
We headed down the hallway to the auditorium where Dr. Foster was preparing for his talk. Since there weren't only a few other astronomy students and grad students there, we got good seats. The BU Astronomy Department has two parts, the Center for Space Physics and the Institute for Astrophysical Research. The Center for Space Physics focuses on topics that are cosmically relatively close-to-home, like the Earth's atmosphere, the planets and moons of our solar system, and our own sun -- objects we can study directly with space probes. The Institute for Astrophysical Research, on the other hand, studies objects that are a little more far-out, beyond our solar system and even our galaxy.
And, as Dr. Foster explained, a lot of the time, what they study is dust. That's because the universe is a rather dusty place. When stars die, they often leave behind (rather pretty) clouds of dust and gas, and it's from these clouds that new stars and their attendant planets form. Of course, not all of that dust ends up being so productively used. Some of it just ends up floating around aimlessly through space. So, we have loose dust floating around in our solar system, between our sun and other stars, in clumps throughout our Milky Way galaxy, between galaxies, and between stars within other galaxies just as in our own.
The first project Dr. Foster told us about was aimed at studying dust between stars in our own Milky Way galaxy to find out just how dusty interstellar space was. According to their current data, the dust in the Milky Way as a whole is mostly found within one narrow band inside the galaxy's plane -- the flat disk where most of its stars are also found. (As you're probably aware, the Milky Way is basically shaped like two fried eggs stuck together.)
To find out if this is typical, they're also taking similar measurements of other galaxies with an instrument launched on a sounding rocket called IMAGER (Interstellar Medium Absorption Gradient Experiment). Yes, Dr. Foster told us, astronomers are big fans of acronyms.
(On a slight tangent, I sometimes get asked how we can observe the Milky Way if we're inside the Milky Way. The answer is that we can look at the parts we aren't in. I can't see all of Boston at once from my room, as I'm within Boston, but I can see the lights of skyscrapers east down to the harbor out the window of my dorm room, and if I went to other windows in the building, I could see what was to the west, north, and south of me. When we see the band of the Milky Way as a patch of hazy light in the sky, we're looking at a part we aren't in, just like the skyscrapers along the Charles are a part of Boston I'm not in.)
The next topic Dr. Foster discussed is also one that's been in the news recently -- the edge of our solar system and the conditions there. The sun sends out heat, light, and energy constantly, and we call this stream of particles the solar wind. Where it blows by the Earth, it interacts with our planet's magnetic field, sometimes creating the auroras at the north and south poles.
The next time you turn on a faucet in a sink or bathtub, watch what happens when the water hits the surface of the basin. It runs out smoothly and very quickly in a circular shape for a little bit, and then, once it gets a certain distance away from the source, it splashes out more messily before flowing slowly. (Here's a picture.)
That's what the solar wind seems to do at the edge of our solar system. It slows down where it meets the gas and dust of interstellar space. However, since the universe is three-dimensional, unlike our flat sink surface, the shock wave around our solar system is more of a bubble than a disk. According to the latest findings, the Voyager probes launched in 1977 are now very close to the edge of this bubble, called the heliosphere, and will pop out into interstellar space soon.
Moving out into our galaxy, Dr. Foster told us about two projects with creative names -- SloWPoKES and MALT 90. SloWPoKES stands for "Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars," and studies M-dwarfs, the smallest type of true stars that exist. M-dwarfs are incredibly long-lived--barring collisions, every M-dwarf that has ever formed is still around and will not die for many more billions of years.
MALT 90, the Millimeter Astronomy Legacy Team at 90 Gigahertz survey, looks at the black clouds in interstellar space where high-mass stars form. In astrophotographs, you can sometimes see these dark clouds blocking out the light from stars behind them. (In the first episode of Carl Sagan's show Cosmos, these clouds are simulated with an effect that looks like ink in water and is rather creepy, like darkness visible.)
Looking at our galaxy as a whole, some astronomers at the Institute for Astrophysical Research are trying to map out its magnetic field by looking at how it affects, you guessed it, galactic dust. Like iron filings scattered on a piece of paper will align with the lines of magnetic force if the paper is held over a magnet, galactic dust aligns with our galaxy's magnetic field. (If you've never tried the filings-and-magnet experiment before, I encourage you to do so, we did it in my physics class last year and the results are rather beautiful.)
Even further out, some BU astronomers study the intergalactic medium -- the space not between stars but between whole galaxies. Out there, clusters of galaxies are sometimes massive enough to bend light and distort the images of other galaxies behind them. Like lenses in a pair of binoculars, this bending can magnify our view of those galaxies, letting us see them as if they were closer and larger. This "lensing" effect shows that distortion isn't always a bad thing!
After Dr. Foster finished his presentation, I asked him what research project he'd most want to work on if he couldn't do the one he was involved with. He had trouble coming up with an answer.
"You end up liking whatever you're involved in." He said.