Tag: Exoplanet

Radio Search for Artificial Emissions from ‘Oumuamua

It’s the first time a visitor from another star system has been seen nearby. But what is it? An asteroid, a comet … or an alien artifact?

Scientists at the SETI Institute have attempted to address this question by using the Allen Telescope Array (ATA) to observe ‘Oumuamua when it was about 170 million miles away, or slightly less than the diameter of Earth’s orbit.

The intention was to measure artificial radio transmissions which, if found, would be strong evidence that this object is not simply a rock tossed into space by a random gravitational slingshot interaction that occurred in its home star system.

“We were looking for a signal that would prove that this object incorporates some technology – that it was of artificial origin,” says Gerry Harp, lead author of a paper to be published in the February 2019 issue of Acta Astronautica.

“We didn’t find any such emissions, despite a quite sensitive search. While our observations don’t conclusively rule out a non-natural origin for ‘Oumuamua, they constitute important data in accessing its likely makeup.”

Following its discovery in October 2017, ‘Oumuamua was the subject of popular speculation about a possible non-natural origin largely because it brought to mind the interstellar spaceship in Arthur C. Clarke’s novel Rendezvous with Rama. Its highly elongated shape and the fact that no coma was observed strengthened this hypothesis for some, as these are uncharacteristic of asteroids and comets.

A recent paper published in Astrophysical Journal Letters by researchers at Harvard has also suggested the possibility that ‘Oumuamua is a deliberate construction. The Harvard researchers argue that the slight, unexpected acceleration observed for this object could be caused by pressure from sunlight as ‘Oumuamua swung around the Sun.

Their hypothesis is that the object might be a light sail, either deliberately or accidentally sent our way. A deliberate origin is considered somewhat more likely because our solar system is a very small target for any object that is not being aimed.

Such arguments strengthen the importance of observations such as those conducted on the ATA that can constrain the true nature of ‘Oumuamua.

Observations were made between November 23 and December 5, 2017, using the wide-band correlator of the ATA at frequencies between 1 and 10 GHz and with a frequency resolution of 100 kHz. No signals were found at a level that would be produced by an omnidirectional transmitter on-board the object of power 30 to 300 milliwatts.

In portions of the radio spectrum that are routinely cluttered by artificial satellite telemetry, the threshold for detection was as high as 10 watts. In all cases, these limits to the powers that could be detected are quite modest – comparable to that of cell phones or citizen band radios.

While no signals were found coming from ‘Oumuamua, the types of observations reported by SETI Institute scientists may have utility in constraining the nature of any interstellar objects detected in the future, or even the small, well-known objects in our own solar system.

It has been long-hypothesized that some of the latter could be interstellar probes, and radio observations offer a way to address this imaginative, but by no means impossible, idea.

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Failed Star Presents Unique Opportunities

A rogue, planet-size object 20 light-years away from Earth has stunned astronomers with its incredibly powerful magnetic field.

The scientists found that the object’s magnetic field is more than 200 times stronger than Jupiter’s, which, in turn, is between 16 and 54 times stronger than Earth’s, according to NASA. How the object, which scientists call SIMP J01365663+0933473, can maintain a magnetic field so strong, as well as generate spectacular auroras, is still unclear.

“This particular object is exciting because studying its magnetic dynamo mechanisms can give us new insights on how the same type of mechanisms can operate in extrasolar planets — planets beyond our solar system,” lead study author Melodie Kao, an astrophysicist at Arizona State University, said in a statement from the National Radio Astronomy Observatory published Aug. 2.

It’s not just the magnetic mechanism that’s leaving scientists with questions right now — there are plenty of other mysteries about the object, which scientists first discovered in 2016.

The object is what scientists call a brown dwarf. Nicknamed “failed stars,” brown dwarfs are larger than planets, but not quite large enough to fuse hydrogen, the way stars do. The boundary line is still debated, but scientists tend to draw it at about 13 times the mass of Jupiter.

Originally, scientists thought SIMP J01365663+0933473 was a gigantic, old brown dwarf. But further study showed that it is instead relatively young, at 200 million years old, and is only 12.7 times the mass of Jupiter. That research also showed that the planet is on its own, not orbiting a star.

“This object is right at the boundary between a planet and a brown dwarf, or ‘failed star,’ and is giving us some surprises that can potentially help us understand magnetic processes on both stars and planets,” Kao said in the statement. “We think these mechanisms can work not only in brown dwarfs, but also in both gas giant and terrestrial planets.”
The team is particularly excited by the new research because it relies in part on radio observations of the object’s auroras — which means that radio telescopes may be able to identify new planets by their auroras.

The new research was described in an article published July 31 in the Astrophysical Journal.
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