Notes from the Astronomy Underground: Unappreciated Topics in Astronomy Part IV

Black Holes. Gamma-ray bursts. The hunt for extrasolar planets. Cosmology and the grandest scales of the cosmos. These are the fields of astronomy with the glitter and sweeping majesty of The Big Picture; sexy fields so infested with the most impressive contemporary buzzwords that NSF funding will chase you down like a pack of rabid ferrets should you show the slightest desire to work in them. But what about the other fields and attendant scientists, the ones that prefer to linger in relative obscurity, the ones to whom you could imagine all the other astronomers awkwardly crooning Bette Midlers Wind Beneath My Wings?

Well, dont actually imagine that. Trust me, it gives you really weird nightmares.

Anyway, its in honor of these thankless men and women of science I present:

Unappreciated Topics in Astronomy Part IV: Star Formation

The Job Description

Stars are kind of an important part of astronomy. A shocking revelation, Im sure, but its true. Decades of relentless stellar observations and increasingly intricate computational models have provided astrophysicists a reasonably complete understanding of how these things work. And by reasonably complete, I mean shamelessly superficial. Dont get me wrong- the voluminous body of mathematically abstruse literature weve compiled over the years is astonishingly complicated and would make any respectable brain wet itself in terror. But in reality, what we know of the underlying physical processes in stars is only a first-order approximation. Much like how my eyesight without my glasses is a shaky window to whats really happening in the world. And like astrophysics research, I have no idea where Im going, I run into walls, and I curse a lot.

But heres the problem. As much as we astronomers pat ourselves on the back for unraveling these cosmic mysteries as best we can, we really arent sure how these objects actually got here. And its not like we can sit back and watch a comically archaic video on Our Changing Bodies for stars, either. As fun as that would be.

Now Timmy, when two giant molecular clouds love each other very much

Of course, Creation Scientists might have an easy solution to this problem, one that I imagine involves a static, 5000 year-old universe, Abraham and Noah riding on dinosaurs like in they were Clydesdales, and nearly every prominent biblical figure looking suspiciously like Charlton Heston.

To be fair, early secular hypotheses concerning star formation, while they did not avoid the issue, were equally sketchy. Though Rene Descartes Theory of Vortices in 1644, and later Emanuel Swedenborgs 1734 Nebula Hypothesis had some good basic ideas about stars forming from swirling, collapsing nebulae, they lacked the mathematical rigor and observational backbone that are the hallmarks of modern science.

Or domesticated dinosaurs a la Flintstones and a brazen indifference to physical reality, if you subscribe to the other school of thought.

Later on, Immanuel Kant and Pierre Simon de Laplaces independent Nebular Hypotheses refined that idea by invoking the conservation of angular momentum to picture such a nebula rotating and contracting into protostellar disks. But our fundamental, modern conception of stellar genesis was established in the early 20th century by James Jeans. According to him, in the constant war between thermal pressure (how warm something is) and gravity, an interstellar cloud wont collapse into a star unless its contents are sufficiently chilled. Like Coors Silver Bullet commercials chilled.

Of course, not all stars are the same, and there are some important differences between so-called early and late type stars.

To review, early type O, B, and A stars are like the bloated, drunken frat boys of the universe. Theyre big, loud, obnoxious, and their lifetimes are proportional to these guys longevity in college. They also end their careers in an explosive, destructive milieu, much like what happens when setting off fireworks in the University presidents house inexplicably seems like a good idea to DKE house.

I dont think these types of stars call each other nonsensical, asinine names like Broseph, or Brahzasaurus, though.

Meanwhile, there are also the late types, the smaller, cooler F, G, K, and M stars that conserve their energy and make it all the way to graduation. Quiet, unassuming grad students fall into the far end of this spectrum, depressingly sticking around academia for years and years

And years.

These stars also take a good hundred million years or so to get started, unlike the short hundred thousand years or so their more energetic relatives require. You might expect the more luminous, boisterous early types to show up to the star formation party first, shotgun some ISM, and trash the place before the other stars show up. This will have some significant consequences later.

Meanwhile on the observational front, the wildly popular multiwavelength approach has enjoyed a broad application to understanding how star formation works. For stars around the size of our sun, an upcoming article in The Solar System summarizes some recent highlights:

Radio observations of the M20 nebula provide images of many stages of stellar evolution, from the parent cloud, fragmentation, collapse, to emission nebulae lit by the first generation of high mass stars. The 1970s and 1980s saw the discovery of lower and lower mass protostars closer and closer to the Solar System. For example, IRAS measurements identified Barnard 5, a currently forming solar-type star. Radio and infrared observations of hydrogen and carbon monoxide have found 100 km/s winds, as well as expanding knots of water and bipolar radio jets characteristic of protostars. At higher energies, Chandra, XMM-Newton, and Einstein Observatory X-ray satellites have also observed nascent solar-type stars and star-forming regions for clues to our suns past.

Check it out. Im using bona fide quotations here. Its like Im trying to make this column passably respectable and not an angry tirade of barely substantiated hyperboles or something.

Anyway, X-ray observations are the newest addition to this science, one thats paradoxically an increasingly big deal here at Penn State, but not ubiquitously known to the Real World. According to Amanda Martin, a fellow grad working on such a project, a typical project in [this] field would be to collect X-ray photons from a space telescope such as Chandra or XMM on a massive star formation region. Moreover, these regions are typically less than 5 million years old so that we can study the evolution of even the most massive stars, which are measured to be 60 times the mass of our Sun.

Dozens of these regions are scattered throughout the galaxy, but theyre too distant to resolve anything but the largest stars. Before any conclusions can be made about X-ray luminosities of these objects, astronomers (or rather, their servile grad students) have to sift through all the photons and determine whether they came from the fetal star, a background galaxy, a foreground source, or some freak cosmic ray. There is some form of art to this pruning of photons, explains Amanda, because sometimes a source will just emit a few photons at one time and then be quiet. These are variable sources that are extremely interesting to us and thus shouldnt be thrown out.

From there, a bunch of scientific objectives are available. For instance, a current topic of interest is studying the effects that quickly forming massive stars have on the evolution of more leisurely-forming ones and their protoplanetary disks. These disks, the precursors to extrasolar planets, were previously identified in infrared studies.

These massive stars are emitting a lot of stellar radiation which cooks and evaporates the disks of nearby stars. With the x-ray source data we can do a statistical significance test to see if those less massive stars around larger stars are less likely to have disks, and later planets.

Why No One Likes It

It would be nice if this Jeans business was the only pertinent criteria for star formation. It would also be nice if George Lucas didnt go unambiguously insane and make another Indiana Jones movie. But we dont live in a perfect world.

Way to ruin yet another franchise, George.

Carl von Weizsacker and Dirk ter Harr in the mid-20th century crashed the party by introducing supersonic turbulence into the mix. Along the way, some other scary-sounding concepts emerged like Alven waves, magnetohydrodynamic turbulence, ambipolar diffusion, and a lot of other nasty-sounding magnetic effects wed prefer to ignore like the current administration ignores polar bears in its environmental policies.

Lacking the computational ability to address these issues, astronomers could pretty much ignore all these problems for 50 years, focusing hardware and software development on better iterations of Oregon Trail and Q*Bert. But now in the 21st century, we really have no excuse. We tried to ford the river, the oxen died, we shot up 8,000 pounds of pixilated Buffalo, Jebediah suffered a slow and agonizing demise from dysentery; its time to move on.

This is the main reason why not a whole lot of people like this field. Its new. Its poorly understood. Its hard. In that sense, this is the epitome of science just not being that transparent to the public. Its all abstract and terminally stricken with incomprehensible jargon. Frankly, thats all the more reason why people should respect it more.

X-ray studies fare even worse in that regard, since its rather counter-intuitive. These energetic photons are normally attributed to equally energetic processes like supernovae or active galaxies, not from the low energy environments needed for gravity to work its magic and turn interstellar refuse into a new star. On the surface, this seems to make as much sense as the soundtrack to Footloose.

I mean, its great youre holding out for a hero, Bonnie Tyler, but theyre racing tractors. In Iowa.

Needless to say, this is all still a work in progress.

Who Does This Stuff?

Anyone working in this field has to be comfortable with the sometimes aggravating minutia of data reduction and all its implicit uncertainties. As with any subfield of astronomy, you have to know your equipment just as well as you understand the physics of whatever youre trying to study.

Or if youre in grad school, confidently dance around actually understanding said physics and try to steal stuff from the supply closet.

How is this any different from the astronomers Ive described in previous updates to this tired series on the overlooked sciences? In a lot of respects its not; Im just running out of ways to rephrase the same sycophantic spiel. I guess the salient difference here is that when you get the data from Chandra or XMM, you really dont know what youre going to get out of them. Will you have the requisite sensitivity to see solar-type stars? Will your resolution be adequate to pick out binaries? Will you finally figure out why everyone in America loves The Princess Bride even though its probably the most unimpressively mediocre comedy ever made?

This kind of primetime game show uncertainty is part of the appeal to star formation research. In terms of the proverbial Big Picture, these studies also have an unspoken effect on the dramatically philosophical Life in the Universe debate. Our current understanding of the Drake Equation frames this issue in a pretty despondent light already, i.e. we shouldnt expect to make timely contact with the possibly mere handful of extremely remote civilizations in our own galaxy. But in consideration of the deleterious effects rapidly forming early type stars have on struggling protoplanetary disks of their diminutive neighbors, the odds are weighed even more against striking up cordial small talk with the extraterrestrial Joneses. How often can you say that your job lets you make grandiose conclusions about the privileged isolation of mankind and the underlying anthropic nature of the universe?

I dont know if I like the idea of our species being somehow uniquely special, though. It makes me wonder whether drinking Saranac and watching Threes Company on Hallmark at two in morning is an ideal use my time.

Eh, who am I kidding? Don Knotts is hilarious.