Our galaxy might actually be square, study finds
Just like being stuck inside and not being able to see what the outside of your house looks like, we鈥檙e trapped inside and aren鈥檛 able to see its complete structure. Most of us have this vision of a circular, with gracefully curving spiral arms. Nope, says a group of from Brazil. The might be square. Not like a box, but, in places, the spiral arms are straight rather than curved, giving the Milky Way a distinctly square look. And sits right on one the straightest parts of an outer arm.
It really IS hip to be square.
The map of the Milky Way has been redrawn several times since the first attempts in the 1950鈥檚 using radio to trace out the spiral arms of our home galaxy. However, the concept of having square-ish arms is not so farfetched: we know of the , above, that has areas of straight and squared off arms, and a found that instead of arms neatly circling the , the mapped traced a more . But most of the maps of the Milky Way have assumed that the material in our galaxy the center in a circular fashion, so having arms stars that don鈥檛 follow this path come as somewhat of a surprise.
Jaques Lepine and his team from the University of Sao Paulo in Brazil wanted to obtain the equivalent of a 鈥漟ace-on鈥� map of the spiral arms of our Galaxy, so they studied the spectra produced by clouds of carbon monosulphide, a common gas in our galaxy, rather than the usual suspect of ionized hydrogen.
They were able to determine velocity information for 870 regions of the Milky Way which is a larger number than that of previous studies based on classical HII regions, so they鈥檝e created a new map of the galaxy with detail never seen before. 鈥淥ne way to improve the description of the spiral arms is to increase the number of objects used to trace them,鈥� the team writes in
Not only did they find evidence for straight places in the arms, but they also found an additional third arm. A had demoted the number of arms from four to two, but other studies, including an earlier one by Levine have said three. So, yes, there is some uncertainty on the number of arms. The new arm is about 30,000 from the at a longitude of between 80 and 140 degrees. This one is rounded however, 鈥渨ith strong inward curvature.鈥�
鈥淏asically, our results confirm the main aspects of the spiral structure revealed by the studies of HII regions,鈥� said Levine and his team. 鈥淔or instance if we move horizontally across the figure, to the right or to the left of the Galactic center, we find roughly 3 spiral arms on each side, like the previous works. There are departures from the pure logarithmic spirals, with segments of arms that are almost straight lines.鈥�
Drawing a map of the Milky Way is a challenging task, since we only have an edge-on view of the galaxy in which we reside. To top it off, it鈥檚 full of dust and gas that muck up the view in the . So, we have to rely on other spectra.
We may not ever know exactly what our galaxy would look like when viewed from other worlds, but we鈥檒l keep trying.
Read the team鈥檚 paper:
Additional source:
Nancy Atkinson blogs at .
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