Why Do More Gamma Ray Bursts Come From A Small Portion Of Our Sky?

And why, correlatively, do fewer come from the opposite orientation -- the other end of an imaginary arrow, which traverses the known Universe?

That is what the Fermi space scope -- for 13 years now (and generations of astronomers, prior to these, in truth) have been trying to discern. Here's a bit:

. . .Astronomers analyzing 13 years of data from NASA’s Fermi Gamma-ray Space Telescope have found an unexpected and as yet unexplained feature outside of our galaxy.

Intriguingly, the gamma-ray signal is found in a similar direction and with a nearly identical magnitude as another unexplained feature, one produced by some of the most energetic cosmic particles ever detected.

The team was searching for a gamma-ray feature related to the CMB (cosmic microwave background), the oldest light in the universe. A burst of visible light thought to have originated when the first atoms formed, the first time light could permeate the cosmos. Stretched by the subsequent expansion of space over the past 13 billion years, this light was first detected in the form of faint microwaves all over the sky in 1965.

In the 1970s, astronomers realized that the CMB had a so-called dipole structure, which was later measured at high precision by NASA's COBE (Cosmic Background Explorer) mission. The CMB is about 0.12% hotter, with more microwaves than average, toward the constellation Leo, and colder by the same amount, with fewer microwaves than average, in the opposite direction. Astronomers generally regard the pattern as a result of the motion of our own solar system relative to the CMB at about 230 miles (370 kilometers) per second.

This motion will give rise to a dipole signal in the light coming from any astrophysical source, but so far the CMB is the only one that has been precisely measured. A team led by Alexander Kashlinsky at the University of Maryland and NASA's Goddard Space Flight Center searched for the gamma-ray equivalent of this signal by adding together 13 years of data from Fermi’s Large Area Telescope.

Analysis of the resulting data revealed a part of the sky where more high-energy gamma rays are arriving than average, but at a level 10 times higher than expected – and in a different part of the sky than the CMB dipole.

The scientists note that the gamma-ray signal they uncovered is in roughly the same part of the sky – and at very similar levels to – an as yet unexplained dipole in the arrival direction of the highest-energy cosmic rays. They suggest the two may be related, with sources yet to be identified producing both signals. . . .

So at present, it does not seem to be solely an artifact of the notion that our Milky Way (with us inside it) is wheeling through the night sky, in a whirlpool fashion, at 230 miles per second (thus changing our orientation, relative to the rest of the Universe / night sky in an appreciable way -- every few days). That's our tiny local solar system animated, at immediate right, as we pull out of it, by the way.

[Could it be that all of space-time slowly revolves around a long, vertical and vast "polar region" -- from which this "arrow" emanates -- and returns? And that pole is generating gamma rays, at one end, and absorbing them at the other side of the Universe? Something like the way our solar system revolves around an imaginary pole, which is perpendicular to our local solar system's orbital plane? And on a grander scale, the way the arms of the Milky Way spiral around a similar imaginary vertical pole?!]

Who knows? But. . . there is thus a worthy puzzle -- for future generations of astronomers. . . to work on. Onward, smiling.

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