Properties of the Wow Signal

Signal Profile

The Wow! Signal was a strong 1420.455 MHz narrowband emission with a peak intensity approximately 30 times above the background noise level (Figure 1 and 2). The actual emission was likely constant for several minutes or even hours; however, the observed bell-shaped profile results from the motion of the radio telescope as it scanned across the source. The increase and decrease in signal intensity reflect the telescope’s beam pattern moving over the source, not intrinsic variations in the source’s emission.

Figure 1. Profile of the Wow! Signal fitted with a simple Gaussian beam model. The fit provides preliminary estimates of the signal strength (expressed as signal-to-noise ratio, SNR), its sky position, full width at half maximum (FWHM), and duration. These values are still under refinement and will be revised. For the current accepted parameters, see Table 1 instead. Credit: PHL @ UPR Arecibo.

Figure 2. This figure shows a ridgeline plot of the Wow! Signal compared to all other signals recorded by the telescope’s 50-channel radio receiver. The Wow! Signal stands out as significantly stronger than the noise levels observed in the other channels. Credit: PHL @ UPR Arecibo.

Signal Location

There is significant uncertainty regarding the exact sky location of the Wow! Signal. Two possible regions, known as the positive (“East”) horn and the negative (“West”) horn (Figure 2), correspond to the two beam positions of the Big Ear radio telescope at the time of detection. Complicating the localization further, the telescope’s diffraction pattern produced not only the main lobe but also multiple sidelobes within each beam, resulting in a complex response pattern. While the signal most likely originated from a position near the center of one of these two regions, its exact origin cannot be determined.

Figure 2. This image displays radio sources and the distribution of neutral hydrogen in the region of the sky surrounding the Wow! Signal location. The beam shapes, including the main lobes and sidelobes, are shown for the two possible positions of the signal, corresponding to the positive and negative feed horns. Radio source data is taken from the NRAO VLA Sky Survey (NVSS), while the neutral hydrogen column density (NHI) is based on the full-sky HI survey combining EBHIS and GASS (HI4PI). Credit: PHL @ UPR Arecibo.

Table 1. Key properties of the Wow! Signal detection.

References

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