fbpx

A slow transient Magnetar has been found with the MWA

Ok so my suggestion to name this object LGM (Little Green Men) 2 was declined by my team Haha but we still aren’t 100% sure that these objects are Magnetars, and to avoid any potential conspiracy addicts (if you’re reading this) going into overdrive right now, it’s not aliens, my LGM 2 reference is a joke and ode to the original (half-jokingly name) LGM 1 which was given to the first Pulsar signal discovered before they knew it was a pulsar.

My Research team at CIRA (Curtin Institute of Radio Astronomy) has found a mysterious signal in Space, it is what we call a slow transient, transient meaning it turns off and on and slow meaning well… it does this slowly.

This signal was actually recorded in 2018 by the MWA Telescope but not discovered until 2021 when an Honours student-led by Curtin Astrophysicist “Natashia Hurley-Walker” was combing through old Archive records and stumbled upon this mystery signal. It turns on for 1 minute and then off for just over 18 minutes which would indicate it rotates once every 18 minutes and that’s odd, Reasons for which I’ll explain further in the article. The team has spent over a year since following up with further observations with the MWA, Parks Telescope in NSW, and NASA’s Chandra X-ray Observatory but here’s the kicker, the signal was only active for 3 months between February – March 2018 and has since turned off and hasn’t been detected since.

The team has also tirelessly looked through the last 10 years of observations from the MWA looking for this signal but to no avail, so it randomly turned on for what seems to be the first time in February 2018 and turned off a few months after and hasn’t been seen since. Weird!

 

This is an image of our Galaxy in radio light with the position of the discovered object highlighted. Credit: ICRAR.

 

So, then what’s a Magnetar? A Magnetar is a Neutron star! These objects are the leftover collapsed dense cores of giant stars after the star explodes in a supernova! The core itself is mainly all Neutrons packed tightly into a ball with some Protons and Electrons in there that survived the collapse. Stars are already spinning, but when the star explodes and its core collapses, this causes it to spin faster and faster as it gets smaller, this is due to the conservation of angular momentum (think of a figure skater spinning on ice, they speed up as they draw in their arms).
This also makes the magnetic field skyrocket up in strength to a billion times stronger than our own Sun’s magnetic field! That’s strong enough to erase your credit card from a 100,000Km away! Magnetars are the most magnetic objects in our universe.
These Neutron stars are Dense, which means they have terrifyingly strong gravity! A single cubic Cementer of Neutronium (which is what Neutron stars are made up of) would outweigh Mount Everest!

Now only around 10% of all neutron stars turn into Magnetars, there is also another type of Neutron star that spins fast and as they spin, they produce beams of energy (Light) out of their North and South Magnetic poles, these objects are called Pulsars! These dead stars spin and as they spin, these beams of light turn with it (think of a lighthouse) when the beam of light turns and flashes at the earth, we see this pulse of light and can detect them via Radio Telescopes, but although rarer, Magnetars can also produce these Beams!
So, recap, all Pulsars and Magnetars are simply Neutron stars but with added more unusual properties!

What’s most important now is that we are not 100% sure what causes these Neutron stars to produce these emission beams. We do know that it’s to do with their strong magnetic field coupled with their fast spin that accelerates electrons on their surface & above its surface up the open magnetic field lines and well that’s what makes this discovery weird! At a spin of 18 Minutes per hour, that’s insanely slow for these objects and as far as our understanding goes, this just isn’t fast enough to produce the beams that we are detecting!

The first thing we were able to determine was it seems to be within our own Galaxy. Its Dispersion Measure (DM) is around 56 and so we can then calculate its rough distance using a model called the electron distribution model to find a distance of 1.3Kpc (kiloparsec) which is well within our own galaxy.

Why do we think it’s a Magnetar? well, that’s tricky to explain but we take all the data and measurements from the radio light it has emitted and deduced many aspects of its characteristics which all seem to match that of Magnetars and Pulsars, such as its Polarization angle and how it flattens across each Pulse, it’s Spectral index, most pulsars/Magnetars show a systematic increase in pulse width and separation of profile components when observed at lower frequencies (meaning emissions at higher frequencies are being produced closer to the surface of the neutron star than at lower frequencies), also it’s around 90% Linearly polarized which all Pulsars and Magnetars generally are and along with other things which unless you want a 10-page article ill avoid going into for now.

I should now add that we have found a second slow transient which we believe to be another Magnetar, however, this one has a rotational period of 22 minutes (even slower) and has been active for the last 5 or 6 years after following up previous data from the MeerKAT Telescope in South Africa, how did that one go undiscovered for so long? it’s got very similar properties to the first discovered object, i.e., angle of polarization and pulse flattening however its Spectral index appears to be different along with other characteristics that could suggest it’s a completely different object.

this all leads to bigger questions, have we just discovered two of the same Objects, and in which case how they have not got picked up previously?
Or have we discovered two completely different objects? which seems even more absurd!

We are working behind the scenes to unravel this mystery, do more follow-ups, and look for other objects emitting slow pulses that fit the same profile… STAY TUNED!
Here is also a quick article you can read on two Neutron stars colliding creating what we call a Kilonova….COOOOOOL! Thanks to Mitch for finding and sending through! Mitch is one of our amazing Astronomers here at the GDC!
If you want to learn more about how these types of objects are created or to understand fully, then you really need to know the full cycle of how stars live their lives and die! what makes some stars fuse heavier elements? what determines if those big stars turn into Neutron stars or black holes? If this interests you, then I’d highly recommend coming to our advanced talk on the Life and Death of Stars! We won’t hold back on the physics so come along, sit down and you might want to strap yourself in! 

You can book here, and you won’t be disappointed! The night includes looking at some of these objects through our telescopes!

And as always if you have any questions then feel free to send me an email here and I’ll happily answer them and feature your question in our article next Month!

Until then keep looking up!