WTF?! In what absolutely sounds like the beginning of an alien invasion movie, scientists are trying to explain a signal that has reached Earth from space. Not only does it repeat every hour, but it also goes through three different states.
The ASKAP radio telescope in Australia detected the signal ASKAP J1935+2148, which has a pulsation period of 53.8 minutes.
The signal is cycling through three states: bright flashes that last between 10 and 50 seconds and have a linear polarization (all waves point in the same direction), weaker flashes with a circular polarization that last 370 milliseconds, and sometimes the object is inactive in 53.8 minutes.
“What is intriguing is how this object exhibits three distinct emission states, each with completely different properties from the others,” said Dr. Manisha Caleb, lead author of the study, in a statement. “The MeerKAT radio telescope in South Africa played a crucial role in distinguishing between these states. If the signals weren’t coming from the same point in the sky, we wouldn’t have believed it was the same object producing these different signals.”
These states of active emissions have evolved over a period of eight months, suggesting that there may be physical changes in the area producing the emission.
Before you start preparing that bunker, the signal is unlikely to be of Independence Day-style alien origin. The signal is believed to be from a pulsar – a type of neutron star – one that rotates more slowly than any of the 3000+ ever measured.
“It’s very unusual to detect a neutron star candidate emitting radio pulses like this. The fact that the signal is repeating at such a quiet rate is remarkable,” added Caleb.
Neutron stars are formed after a supernova – the explosion that occurs when massive stars about 10 times the mass of the Sun use up all their fuel and explode. The stellar debris that remains is so dense that it packs 1.4 times the mass of our Sun into a ball just 20 kilometers (12.4 miles) wide, making them the second densest objects in the universe after black holes.
The powerful magnetic fields of neutron stars send streams of particles into space. The rotations of the pulsars cause the streams to rotate, creating what appears to be a repeating signal.
The rate at which this neutron star emits radio light is too slow for current descriptions of radio neutron star behavior. Neutron stars take only seconds or even fractions of a second to spin completely on their axis, so it should be impossible for one to spin as slowly as ASKAP J1935+2148 and still send out pulses. Researchers say this provides new insights into the complex life cycles of stellar objects.
An alternative explanation is that the object is a highly magnetized white dwarf that emits coherent radio emission like a neutron star pulsar, although radio emissions from isolated magnetic white dwarfs have never been detected before.
More research is needed to confirm whether the object is a neutron star or a white dwarf (or aliens?). “It may prompt us to reexamine our decades-old understanding of neutron stars or white dwarfs; how they emit radio waves and what their populations are like in our Milky Way galaxy,” said Dr Caleb.
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