One of the challenges is radio astronomy is keeping your data free from extraneous signals. Humans use radio waves and microwaves for everything from transmitting music and mobile phone data to cooking a quick dinner. For this reason radio telescopes are often in fairly isolated places, such as the radio quiet zone in West Virginia or the ones in Australia. These limit the amount of contamination from stray signals. But astronomers who work at these remote telescope sites also have to live there, and they utilize things like microwaves in their daily lives. Sometimes that leads to some interesting science.

You might remember a while back I wrote about some strange signals being detected by the Parkes radio telescope in Australia. They were short, seemingly intense bursts of radio energy that would appear in the data from time to time. They seemed to fall into two groups. The first, known as perytons, had all the markings of being terrestrial. They were detected by a range of detectors rather than specific ones, and they didn’t show evidence of frequency dispersion, which is seen in deep space radio signals. The second type is known as fast radio bursts, or FRBs. These are also short lived, but have frequency dispersion and seem to come from specific directions in the sky.

The general consensus has been that FRBs are astrophysical in nature, while perytons are terrestrial. But it wasn’t entirely clear what perytons were. Now a paper published on the arxiv seems to have found the cause, and it’s hungry astronomers. The team began to wonder how a burst of radio energy might be produced locally. Since Parkes is in a radio quiet zone, that would seem to make the most sense. One obvious possibility is a microwave oven, but these operate at about 2.5 GHz, while the peryton signals were around 1.4 GHz.

The Cosmic Microwave Oven Background

But when the team looked through the peryton data, they found that each peryton was accompanied by a 2.5 GHz signal. They also found other 2.5 GHz signals that weren’t accompanied by perytons. The team speculated that perytons could be due to a microwave oven when the door is opened while still running. When you open the door of an active microwave oven, there is a short burst of radio waves as the oven is still powering down. This burst of energy isn’t harmful, but it could easily be picked up by a radio telescope. To test this idea, the team looked at where the telescope was aimed when each peryton was detected. Sure enough, a microwave was in the line of sight each time.

Just showing a correlation between perytons and an astronomer’s desire for hot pockets isn’t proof, but it seems reasonable given the evidence. The authors point out that if a peryton is detected without a corresponding 2.5 GHz signal, then that would disprove this hypothesis.

It’s important to point out that this does not demonstrate that FRBs are caused by microwave ovens. Perytons and FRBs are distinctly different in many ways. In fact, demonstrating a terrestrial origin to perytons helps us narrow down the astrophysical causes of FRBs, since it provides a simple way to distinguish them.

Paper: E. Petroff, et al. Identifying the source of perytons at the Parkes radio telescope. arXiv:1504.02165 [astro-ph.IM] (2015)

The post What’s Cooking appeared first on One Universe at a Time.

A few days ago I wrote about an interesting type radio signal known as a fast radio burst. These are short, intense pulses of radio energy that have all the hallmarks of being astronomical in origin.  One possible source of FRBs could be a neutron star collapsing to a black hole. But there is still some discussion that such bursts could be terrestrial in origin because of another type of radio burst known as a peryton.

The first FRB is known as the Lorimer burst, named after Duncan Lorimer, whose pulsar research group discovered the burst. The Lorimer burst had a couple of distinguishing features that point to it being astronomical.  The first is that its spectrum is dispersed. That is, instead of being a simple burst with all different frequencies happening at once, the frequencies were spread out, with higher frequencies first and lower ones later.  This whistler effect is characteristic of a pulse that has traveled through the interstellar medium.  It occurs because when an electromagnetic pulse interacts with charged ions, different frequencies are slowed by different amounts, with the lower frequencies slowed down more.  So you get a dispersion effect. Stray bursts or chirps from terrestrial sources generally don’t have the same dispersion because they don’t travel through plasma and they don’t travel far.

Another feature of the Lorimer burst is that it was localized within the detectors.  The Lorimer burst was observed at the Parkes radio telescope (seen in the figure), which has a 13 beam receiver. Each beam is the radio equivalent of a pixel in a digital camera.  The burst maxed out (saturated) one of the beams, but the others were largely unaffected.  This indicates that it was from a single astronomical direction, and not a local electromagnetic burst.

Since the Lorimer burst, there have been detections of at least four similar bursts, which is why there is an effort to determine what their astronomical origin might be.  But this is where it gets interesting, because in addition to the Lorimer-type bursts (FRBs) there is another type known as perytons.  Perytons have a similar intensity, and are also dispersed, but they max out all 13 beam receivers.  This means they are not from a directed astronomical source, and are therefore terrestrial.  These perytons only appear at Parkes, which is also the only place to have observed the FRBs.

Since both FRBs and perytons have only been detected at one radio telescope, you might thing that points pretty strongly to both of them being some kind of local interference or glitch unique to Parkes, but that isn’t the case.  For one, the Parkes radio telescope is particularly suited to detecting this type of signal, so it isn’t too surprising that only Parkes has detected FRBs. For another, perytons are distinctly different from FRBs. While both are dispersed, they are dispersed in different ways, and the peryton dispersion doesn’t match that of an astronomical source.

For now, it seems like Lorimer-type FRBs are astronomical in origin and perytons are terrestrial in origin. Beyond that they are a mystery.

The post Peryton Place appeared first on One Universe at a Time.