Mysterious Signal Coming From Our Galaxy Could Be One of The Rarest Known Objects

Only one other object has ever been identified as an object so rare that it could be a repeating radio signal.

The signal uploaded to arXiv could be a white dwarf radio.

Since the early days of pulsar astronomy there has been speculation that a rotating magnetic white dwarf might show activity similar to a pulsar.

The recently discovered periodic radio Transient is a candidate for the first true white dwarf pulsar. It has a period of 18.18 minutes and it has a low Frequency emission with a bright temperature. There is no companion with which to interact. Its period is hundreds of times longer than any of the others, but it still meets the criteria of a classical pulsar.

Once a star has ejected its outer material and core, no longer supported by the outward pressure of fusion, it collapses under its own gravity.

If the star is over 30 times the mass of the Sun, the core collapses into a black hole.

A progenitor star between eight and 30 times the mass of the Sun results in a neutron star, which is around 20 kilometers (12 miles) across and up to 1.4 times the mass of the Sun.

The core of a star less than eight times the mass of the Sun will collapse into a white dwarf, packing mass up to 1.5 times that of the Sun into a ball between the sizes of Earth and the Moon.

There are a subset of stars called pulkas. The beams of bright radio waves shooting from the magnetic poles sweep past Earth on the scale of seconds down to milliseconds, when the neutron stars are rotating incredibly fast.

Scientists have wondered if similar behavior could be observed in white dwarf stars, and in 2016 they seem to have come close. In a system with a red dwarf star, AR Scorpii flashes on a timescale of minutes.

The periodic signal lacks coherence and it is closer to a neutron star than it is to a black hole. The signal might be different from traditional radio pulsars.

This brings us back to the location, which is 4,000 light-years away from Earth. It was one of the most bright objects in the low-frequency radio sky from January to March of this year.

The research team thought it might be a hypothetical object called an ultra-long-period magnetar because it matched the profile of no known astronomy object. The explanation still didn't fit that the star was a neutron star with a powerful magnetic field.

The International Centre for Radio Astronomy Research (ICRAR) in Australia explained at the time that nobody expected to detect one like this.

The first problem is that the rotation period is too long, and the second is that the pulse was too bright for a pulsar. If the object is a white dwarf, the problems will be solved.

It would be the first white dwarf discovered that shares the same physics and radiation mechanism as traditional radio pulsars. Although white dwarfs are very dim, and we might not be able to pick up any visible light at its distance, it could be a promising target for optical observations. It is worth a shot given the possibility.

Astronomers could look at other white dwarfs to see if they have the same properties.

If it were bright enough, optical observations could determine its magnetic field.

The fast-rotating, strongly magnetized, white dwarf would be promising targets for low frequencies radio observations to determine if any of them are white dwarfs.

The paper has been uploaded.