Tag Archives: cobe

Cosmic Color Schemes

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I was really asleep at the wheel for this one. A Spitzer Space Telescope press release from 18 December describes the detection of light from “the Universe’s First Objects”—a version of the above image appears as today’s Astronomy Picture of the Day (APOD), which is what tipped me off (sorry to say).

Anyway, the image in question shows light “from a period of time when the universe was less than one billion years old, and most likely originated from the universe’s very first groups of objects—either huge stars or voracious black holes.” In the research paper, this light is referred to as “cosmic infrared background (CIB)” radiation, as opposed to the more familiar cosmic microwave background (CMB)” radiation.

Verbiage aside, what I find odd about this image is the choice to color-code intensity as color. A perusal of the aforementioned research article indicates that color information (i.e., the color of the background signal in infrared light) is minimal, but the blobby fluctuations that range from black to purple to pinkish-red to yellowy-white. To my eye, the color range (I hesitate to use the word “spectrum”) seems forced and unnatural—at least as a way of representing intensity—but I dunno. Honestly, however, I admire the choice to show blocked-out regions, which correspond to areas obscured by nearby stars and galaxies—as grey zones. Truth in advertising, as it were.

An associated image related to the press release confuses me even more. For some reason, data from the Cosmic Background Explorer (COBE) is used instead of data from the much more recent Wilkinson Microwave Anisotropy Probe (WMAP). Why? Perhaps becuse WMAP has better resolution…? I can’t say for sure because there are no units presented with the press images, making comparison difficult—i.e., I’d need to go back to the research article and the WMAP and COBE data to compare the two, which is something I haven’t time to do for a blog that is, in fact, not my day job.

So… I have mixed feelings. It’s a complicated concept to introduce to a lay public, but the variety of false color schemes—from COBE to WMAP to the above—muddy the waters. And it’s garish muddying at that.

Flahback to the Cosmic Microwave Background

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On the heels of the Nobel Prize committee announcing that John Mather and George Smoot had been awarded the 2006 Physics Prize “for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation,” I thought it might be nice to flash back briefly.

I was in grad school when the Cosmic Background Explorer (COBE) results were first analyzed and announced, and the graph above was the first result I saw. For astrophysicists and cosmologists, the result confirmed expectations stunningly well. The solid, curved line in the graph depicts the blackbody spectrum predicted by theory; the dots and squares lying along the curve indicate actual data collected by the satellite (some of which have lines attached to them indicating uncertainty in the measurements). The match between data and theory rarely matches so precisely, and (as I remember) the astronomical community was quite impressed with itself.

However, cosmologists expected some variation around this simple curved line—little squiggles, if you will, that would tell us about the structure of the early Universe. But as the COBE scientists dug deeper and deeper into their data, they didn’t find anything. Hubris turned to worry until fluctuations were discovered at the level of one part in 100,000! Tiny variations in this otherwise smooth curve. Depicting these variations as color differences in pink and purple led to the classic, garish COBE image depicting the entire sky as an oval.

In the past few years, the Wilkinson Microwave Anisotropy Probe (WMAP) has refined these measurements and told us even more about the structure and origins of the Universe, bt as I recall, it all started with the graph you see above…