Today is the last full day of the American Astronomical Society's (AAS) 222nd conference. Before you cry about that, remember that the discoveries will continue to roll out, even if the astronomers aren't having mid-morning coffee breaks with 500 of their closest friends. Their probing questions and productive collaborations will continue after the hotels' mandatory 11 a.m. check-out times.
The first speaker of the day was Steve Howell, an astronomer with a ponytail, who is the Deputy Project Scientist for Kepler at the NASA Ames Research Center in California. When you think of Kepler, you probably think "Oh, yeah, that thing that keeps finding smaller and smaller planets" — and you're right! But it is more than that. It is also expert at probing stars' insides from afar. This kind of study is called "asteroseismology," and it deals with the oscillations, pulsations, and general internal turmoil of stars.
Kepler is particularly adept at studying exotic, extreme binary star systems, like those called "heartbeat stars," in which the two suns pass so close together that their mutual gravity causes their sides periodically to bulge. The side-stretching produces a pulsation, which shows up like a heartbeat on an electrocardiogram.
Scientists have published 341 papers about astrophysics discoveries related to such non-planet-discovery. Howell stated that it's easier to study the internal dynamics of stars other than the Sun because the Sun is so close that we almost know too much about it. "Once you can study something in more detail, you find it harder, and you can't understand it anymore," he said. When distance blurs some of the details, other intricacies come into focus.
An updated catalog of Kepler's candidate planets will be out this fall, but scientists have analyzed only half the collected data. In other words, the catalog soon will look like the Yellow Pages. Two hundred ninety-six papers have been published about the thousands of planets and candidate planets the telescope has found so far.
Unfortunately, a stabilizing wheel on Kepler recently failed, leaving the telescope unable to point at a specific spot in space. Still, scientists haven't left it feeling cold and abandoned. "We talk to Kepler many times a week," Howell said.
And soon, they may ask for ideas for how to jump-start Kepler out of its slump and back into the working world. A two-wheel hybrid mode (no details on what that means, exactly, yet) is a possibility, and Kepler could do some kind of non-exoplanet science.
But Kepler isn't the only one doing planet and star science. Todd Henry, a scientist with the Research Consortium on Nearby Stars (RECONS) project, reported more about the smallest star, which I talked a little bit about on Monday. RECONS data has doubled the number of known red dwarfs and revised the stellar census: Scientists now believe that 75 percent of all stars are such dwarfs. Of the smallest stars within 82 light-years of Earth, 3.3 percent have known planets, and that figure is likely to rise.
But how do stars form? Bruce Elmegreen of IBM gave a review of the current state of star-making research. If you're egocentric and consider the galaxy to be an extension of yourself, you'll be happy with the finding that "galaxies like the Milky Way dominated star formation in the universe, so we're in good company."
But the star formation doesn't always happen in the bright arms of spiral galaxies, contrary to what seems intuitive. In some galaxies, the rate at which new suns form is the same between the arms (a place we could call "armpits") as it is in the arms themselves.
To find out what the Milky Way and its star formation looked like in the past, scientists can look at similar galaxies that are different distances away from us — and thus are seen at different points in the universe's timeline. Check out the collection of images to the right, which shows how the Milky Way might have looked to us if we a) had been born a long time ago and b) weren't stuck inside of it.
If you're interested in how the star-forming gas in the Milky Way arranged itself, you might want to take a look at Renaud's team's high-resolution model, which you can zoom like a Google map!
Still on the star-formation theme, here are some shorter highlights of the last full conference day:
- Robert Benjamin, a scientist at the University of Wisconsin-Whitewater, took us to the edge of the Milky Way, which his team determined was 45,000 light-years out. The project mapped the locations of 20 million red clump giant stars, and the outer boundary of the Milky Way is where the density of those common stars drops away.
- The Milky Way Project, a citizen science program that has involved over 100,000 participants, has a goal of finding "bubbles" in the galaxy. Scientists suspect most of these bubbles are areas where massive star formation has blown away interstellar gas and dust, leaving relatively empty space. Charles Kenton of Iowa State University said the project has identified 5,000 bubbles and shown that more star formation occurs where massive star formation recently occurred.
- Wouldn't it be nice to know how, exactly, the solar system went from being a disk of swirling material to an organized system of planets, moons, and a star? Studies like the one led by Nancy Brickhouse of the Harvard-Smithsonian Center for Astrophysics observe Sun-like stars that are at different points in their evolution, which is the closest astronomers can get to hopping in a time machine. TW Hydrae, which is only 10 million years old, is surrounded by a disk that will (scientists think) go on to form planets. TW Hydrae's magnetic field channels material from this disk onto the star's poles. However, the star can't keep taking and taking, just like you cannot eat cake after cake after cake after cake. Some of the infalling stuff is shot back out, helping to ionize and heat the disk, which will aid in planetary formation.
- Sarah Willis, also of the Center for Astrophysics, wins the Title of the Day award for "Cat's Paw Nebula littered with baby stars." She said that this nebula, NGC 6334, contains stars up to 40 times massive as the Sun and matter totaling 150,000 times its mass. In the Cat's Paw, her team found 375,000 protostars that were less than half a million years old. This star factory turns the equivalent of 3,600 Suns of material into stars in just a million years.
Dawn Summer, a professor of geology at the University of California, Davis, and a co-investigator on the Mars Science Laboratory team, closed out the day with the latest results from Curiosity. Curiosity has been in Gale Crater since August of 2012. This depression has "a good history of environments through time within one particular area." While "engineers insist on landing somewhere safe and flat, geologists love cliffs like the Grand Canyon," where rock is exposed and features are rugged. Gale was a compromise between scientific promise and practicality. Although the rover now has only budged some 1,600 feet (50 meters) from its landing spot, it has, among other things, characterized the radiation environment at the surface, found a habitable spot, discovered the basic chemicals that can lead to life, confirmed the existence of water, and found pebbles rounded by once-flowing water. Curiosity technically is a two-year mission, but Summer said, "One presumes that as long as it's working, we'll keep at it."
According to the sessions I attended today, the universe is full of stars and planets. That sounds pretty accurate. Astronomers continue to discover more of both, and the universe continues to produce more of both. The exact mechanisms by which it does so will become even clearer as researchers continue studies like the ones I heard about today.