A strange radio signal that seemed to emanate from a small nearby star instead probably came from Earth-orbiting satellites, astronomers now say.
Last week, one of the closest stars to Earth, Ross 128, was thought to have emitted radio signals that have left researchers at Puerto Rico's Arecibo Observatory puzzled and fascinated. That made many space buffs jump to the first conclusion they always jump to.
"Bottom line: Astronomers at Arecibo Observatory observed a peculiar radio signal from the nearby star Ross 128," said Deborah Byrd, EarthSky radio series editor-in-chief. "They aren't saying 'aliens,' but the natural explanations have weaknesses."
According to Space.com, although the signal was theoretically consistent with a transmission from an alien civilization, astronomers said that hypothesis was "at the bottom of many other explanations." The leading candidates were flares from Ross 128, emissions from some other object in the same field of view as the star, or a burst from one or more high-orbiting satellites.
The original observations of the signals were made May 12, said the Planetary Habitability Laboratory website. Since then, follow-up observations at Arecibo, the Green Bank Telescope in West Virginia and the Allen Telescope Array in northern California suggest a satellite burst as the most likely scenario.
"The best explanation is that the signals are transmissions from one or more geostationary satellites," said Abel Mendez, director of the Planetary Habitability Laboratory at the University of Puerto Rico.
Geostationary satellites circle Earth at an altitude of about 22,300 miles, noted Space.com.
"This explains why the signals were within the satellite’s frequencies and only appeared and persisted in Ross 128; the star is close to the celestial equator, where many geostationary satellites are placed," said Mendez. "This fact, though, does not yet explain the strong dispersion-like features of the signals (diagonal lines in the figure); however, it is possible that multiple reflections caused these distortions, but we will need more time to explore this and other possibilities."
The observatory's researchers hadn't noticed the activity until two weeks after they were recorded, reported Popular Mechanics. At the time, they said they determined the signal couldn't have come from any man-made satellites because the radio signal was dispersed in all directions.
The signals behavior was similar to Type II solar flares, which are energetic events that vary rapidly in time and energy levels, but those are at a much lower frequency than what the observatory noticed.
"Since the frequencies are so high I'm counting on it being a new class of stellar flare for that hypothesis to work," Mendez said at the time, according to Popular Mechanics. "To our knowledge, that will be the first such signals are observed in any star."
Although the Ross 128 signal has a prosaic explanation, scientists should still follow up on similar detections in the future, said Seth Shostak, a senior astronomer at the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, California.
"The historic lesson is clear — these things pop up, and you have to follow them up, because you never know what's going to be the real one, or even if there will ever be a real one," Shostak, who was involved in the recent ATA observations of Ross 128, told Space.com earlier this week. "Following up is mandatory."
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