Friday, February 4, 2022

3446 - STRANGE RADIO WAVES - what else to discover?

  -  3446  -   STRANGE  RADIO  WAVES  -    what else to discover?    Astronomers have discovered unusual signals coming from the direction of the Milky Way's center. The radio waves fit no currently understood pattern of a variable radio source and could suggest a new class of stellar object.




-------------  3446  -   STRANGE  RADIO  WAVES  -    what else to discover?

-  The strangest property of this new signal is that it is has a very high polarization.  Its light oscillates in only one direction, but that direction rotates with time.  The brightness of the object also varies dramatically, by a factor of 100, and the signal switches on and off apparently at random.

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-  Many types of star emit variable light across the electromagnetic spectrum. With tremendous advances in radio astronomy, the study of variable or transient objects in radio waves is a huge field of study helping us to reveal the secrets of the Universe. Pulsars, supernovae, flaring stars and fast radio bursts are all types of astronomical objects whose brightness varies.

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-   It could be a pulsar, a very dense type of spinning dead star, or else,  a type of star that emits huge solar flares.

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-   Surveying the sky with ASKAP to find unusual new objects with a project known as variables and slow transients (VASTs), throughout 2020 and 2021.  Looking towards the center of the galaxy, we found ASKAP J173608.2-321635. This object was unique in that it started out invisible, became bright, faded away and then reappeared.

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-  After detecting six radio signals from the source over nine months in 2020, the astronomers tried to find the object in visual light. They found nothing.  Astronomers  tried the more sensitive “MeerKAT radio telescope” in South Africa. Because the signal was intermittent, we observed it for 15 minutes every few weeks, hoping that we would see it again.

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-  Luckily, the signal returned, but we found that the behavior of the source was dramatically different.  The source disappeared in a single day, even though it had lasted for weeks in our previous ASKAP observations.

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-  The  “Square Kilometer Array”, SKA , will be able to make sensitive maps of the sky every day.  The power of this telescope will help us solve mysteries such as this latest discovery, but it will also open vast new swathes of the cosmos to exploration in the radio spectrum.

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-  By mapping radio waves in the universe astronomers have discovered something unusual that releases a giant burst of energy three times an hour, and it's unlike anything astronomers have seen before.

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-  The team that discovered it think it could be a neutron star or a white dwarf, collapsed cores of stars, with an ultra-powerful magnetic field. Spinning in space, the strange object sends out a beam of radiation that crosses Earth's line of sight, and for one minute in every 20, is one of the brightest radio sources in the sky.

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-  This object was appearing and disappearing over a few hours during our observations. It's really quite close to us, about 4,000 light-years away. It's in our galactic backyard.

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-   Objects that turn on and off in the universe aren't new to astronomers.  They call them “transients“.  Slow transients like supernovae might appear over the course of a few days and disappear after a few months. 

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-  Fast transients, like a type of neutron star called a pulsar, flash on and off within milliseconds or seconds.   This mysterious object was incredibly bright and smaller than the sun, emitting highly-polarized radio waves, suggesting the object had an extremely strong magnetic field.

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-   An ultra-long period “magnetar” is a type of slowly spinning neutron star that has been predicted to exist theoretically.  But,  nobody expected to directly detect one because we didn't expect them to be so bright. Somehow it's converting magnetic energy to radio waves much more effectively than anything we've seen before.

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-  By monitoring the object with the MWA to see if it switches back on. There are telescopes across the Southern Hemisphere and even in orbit that can point straight to it.  MWA  telescope is a precursor instrument for the ‘Square Kilometre Array“, a global initiative to build the world's largest radio telescopes in Western Australia and South Africa.

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-  The Murchison Widefield Array is located on the Murchison Radio-astronomy Observatory in Western Australia. The observatory is managed by CSIRO, Australia's national science agency, and was established with the support of the Australian and Western Australian Governments.

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-  The light we “see” with is so limiting.  Astronomers get whole new eyes with the entire electromagnetic spectrum as well as cosmic rays, and gravity waves , and , what else can we discover to see with?

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February 3, 2022      STRANGE  RADIO  WAVES  -    what else to discover?      3444                                                                                                                                               

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