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    This Is the Best Map Yet of the Early Universe

    Written by

    Derek Mead


    Image: ESA and the Planck Collaboration

    That we can look backwards in time by looking at really old light is one of the most fundamentally awesome aspects of astrophysics. It's useful, too: Researchers have compiled what the ESA calls the most detailed map of cosmic microwave background radiation (CMBR), ancient emissions that are left from the Big Bang. According to NASA, the map above shows fluctuating levels of those microwave emissions that date back to when the universe was just 370,000 years old.

    The data come from the first 15 and a half months of observations from ESA's Planck space telescope, which is tasked with looking at some of the universe's earliest emissions. The map above is essentially a heat map. CMBR, which is spread uniformly through the observable universe, has expanded over time to huge wavelengths, but still shows minor fluctuations that correspond to temperature differences caused by uneven concentration of matter in the early universe–areas with denser material in the hot atomic soup of the baby universe were hotter, and empty regions cooler.

    Those fluctuations have persisted, and appear on the map: red regions are regions of higher matter density, while blue regions have lower density. That means the Planck telescope was able to take a portrait of the early universe as the atomic soup following the Big Bang first began to coalesce into matter. In fact, that's where the CMBR comes from: when protons and electrons fused together to produce hydrogen, the first element in the universe, they released energy which to this day persists as CMBR.

    Image: ESA and the Planck Collaboration

    This new map from Planck is the most precise of its type yet produced, which is to be expected as the Planck satellite was designed to be more sensitive than any other previous telescope for this type of work. That precision has already yielded some curious results. First, it appears that the universe is expanding at a slower rate than previously expected.

    That rate of acceleration, known as the Hubble Constant, was previously estimated by NASA's WMAP telescope, the predecessor to Planck, at being about 69.32 kilometers per second per megaparsec. The Planck data suggest that speed is slower, at 67.15 km/s/Mpc. Why does that matter?

    Well, if the universe is expanding more slowly than thought, that means it would have taken a longer time to get to its current size. In other words, the Planck data suggest the the universe is older than thought–13.82 billion years is the estimate, which is about 100 million years old than previously calculated.

    Perhaps the strangest is the finding that average temperatures are not uniform in opposite hemispheres of the observable universe. As you can see in the image above, the southern ecliptic hemisphere (below the curved line) has slightly higher average temperatures than its northern counterpart.

    That finding runs counter to the standard model of the universe, which would predict that energy should be spread fairly uniformly throughout the universe following the Big Bang. Additionally, the circled region above shows a cold patch of sky that's larger than would be expected. That suggests that the universe essentially didn't mix itself up as uniformly as has been hypothesized, but it's not clear why. It could be that the Planck map doesn't take enough of a macro view, or that CMBR rays have been manipulated in a way that's not yet understood.

    “Our ultimate goal would be to construct a new model that predicts the anomalies and links them together. But these are early days; so far, we don’t know whether this is possible and what type of new physics might be needed. And that’s exciting,” George Efstathiou of the University of Cambridge said in a release.

    But overall the new Planck analysis suggests the universe fits pretty closely to previous models. The data suggest the universe is made of a little bit more dark matter than previously estimated (26.8%, up from 22.7%) and ordinary matter, like what planets are made of (4.9%, up from 4.4%), while the proportion of estimated dark energy in the makeup of the universe has correspondingly declined.

    There are two ways to look at the data released by the ESA–which, to be clear, aren't the final word. First is that the harder we look at the universe, the more we realize we don't understand it so well. (We still aren't sure what dark energy even is, remember.) On the other hand, it's impressive how closely our models hold up as our data gets more precise and more refined. I suppose both are true, as is this: The universe is really old, and it's amazing that we're even able to prove that.