By Ann Finkbeiner | October 29, 2013 | 4 Comments
Astronomers irritate the hell out of me, NASA’s in particular, not the people but their press releases: never met a superlative they didn’t like, Biggest Black Hole, Farthest Quasar, Youngest Galaxy, and on and on, far into the night. The black hole’s size isn’t interesting unless it says something about how galaxies form. The quasar’s distance and the galaxy’s youth aren’t interesting unless they’re evidence for when and how galaxies formed. The rule is, discoveries are interesting only in their contexts. And in general press releases are less interested in context than in shock and awe, e.g., “NASA’s Great Observatories Begin Deepest Ever Probe of the Universe.” Let’s agree to ignore “deepest ever probe” and concentrate instead on those Great Observatories because NASA has a plan for using them and really, they’re good.
The Great Observatories are telescopes in space, launched with great hoopla and at enormous cost in money and astronomers’ careers a long time ago. The Hubble sees in the optical wavelengths in which humans see; Chandra, in x-rays; and Spitzer, in infra-red. They’re all up there above the atmosphere that, depending on the wavelength, distorts or blocks or swamps or otherwise screws with what we can see from the ground. So they see with precision and clarity to unbelievable distances and times. The reason they’re all up there is that the optical wavelengths in which we see are a piddly, pathetic little fraction of what the universe shines in.
The plan is called Frontier Fields (“fields” as in fields of view; “frontier” because NASA likes that word): over the next three years, all three observatories are going to look at the same few clusters of galaxies, partly because clusters themselves are interesting, partly because clusters are so massive they make big dents in space, that is, they curve the daylights out of space. And since light follows space’s curves, those big dents, those clusters, are also curving light and acting like lenses. In fact, a lens, called a gravitational lens, is real and effectively magnifies whatever is on its other side. On the other side of the clusters are galaxies going back as far as galaxies go. The lensing will show galaxies ten to a hundred times fainter and farther away, back when the universe was mostly hydrogen gas and the baby galaxies were first lighting up and blowing electrons off the hydrogen atoms and ionizing the whole universe.
The press release says that Hubble will show how fast those back-forty galaxies are forming stars. Spitzer will show how old the galaxies are. Chandra will show which of the galaxies have supermassive black holes – probably a violent youth that all galaxies go through.
The observatories will look at six clusters in all. During the first year, they’re looking at Abell 2744 and MACSJ0416.1-2403 (see photo at top of post) (the naming of astronomical things is its own rabbit hole but specifically, Abell is a catalog of bright clusters compiled by George Abell and this one is the 2,744th in that catalog; and MACS is the Massive Cluster Survey, and the numbers are the coordinates in the sky). The lensing also enables a more accurate measure of the clusters’ masses. And the amount of mass implied by the cluster galaxies’ light, compared with the amount implied by the lensing gives the amount of the clusters’ dark matter. And the amount of dark matter in the universe gives the nature of its death. (Ask Richard.)
Galaxy formation and the density of dark matter have both been studied for decades. If the Frontier Fields turn up no surprises and cosmologists continue to be right about the history of the universe, then the Great Observatories will add the refinements to cosmological history necessary for credible science. Otherwise, surprises, of course, will always be welcome. Meanwhile, what makes Frontier Fields so interesting is its multiwavelength context. The length of those waves ranges from 106 to 10-16 meters, from a million meters to a ten-quadrillionth of a meter, from radio to gamma; and the things of the universe are radiating in all of them.
The optical is the smallest band, with wavelengths right around a millionth of a meter, just a sliver of what’s out there. Looking in the optical at the universe is like hearing only the flutes in a Beethoven symphony. Granted, Spitzer and Chandra expand the range only into the infrared and xray bands, but still: looking at those fields comes a lot closer to hearing the whole orchestra.
3 images of 1 galaxy, M101: Spitzer Image: NASA, Jet Propulsion Lab/Caltech, and K. Gordon (STScI); Hubble Image: NASA, ESA, K. Kuntz (JHU), F. Bresolin (University of Hawaii), J. Trauger (Jet Propulsion Lab), J. Mould (NOAO), Y.-H. Chu (University of Illinois, Urbana), and STScI; Chandra Image: NASA, CXC, and K. Kuntz (JHU)