HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

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HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by bystander » Wed Jul 27, 2016 9:17 pm

White Dwarf Lashes Red Dwarf with Mystery Ray
ESA Hubble | ESO VLT | Science Release | 2016 July 27
[img3="Credit: M. Garlick/University of Warwick/ESO, ESA/Hubble"]https://cdn.spacetelescope.org/archives ... c1616a.jpg[/img3][hr][/hr]
Astronomers using ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, along with other telescopes on the ground and in space, have discovered a new type of exotic binary star: in the system AR Scorpii a rapidly spinning white dwarf star is powering electrons up to almost the speed of light. These high energy particles release blasts of radiation that lash the companion red dwarf star, and cause the entire system to pulse dramatically every 1.97 minutes with radiation ranging from the ultraviolet to radio.

In May 2015, a group of amateur astronomers from Germany, Belgium and the UK came across a star system that was exhibiting behaviour unlike anything they had ever encountered. Follow-up observations led by the University of Warwick and using a multitude of telescopes on the ground and in space [1], have now revealed the true nature of this previously misidentified system.

The star system AR Scorpii, or AR Sco for short, lies in the constellation of Scorpius, 380 light-years from Earth. It comprises a rapidly spinning white dwarf [2], the size of Earth but containing 200 000 times more mass, and a cool red dwarf companion one third the mass of the Sun [3], orbiting one another every 3.6 hours in a cosmic dance as regular as clockwork.

In a unique twist, this binary star system is exhibiting some brutal behaviour. Highly magnetic and spinning rapidly, AR Sco’s white dwarf accelerates electrons up to almost the speed of light. As these high energy particles whip through space, they release radiation in a lighthouse-like beam which lashes across the face of the cool red dwarf star, causing the entire system to brighten and fade dramatically every 1.97 minutes. These powerful pulses include radiation at radio frequencies, which has never been detected before from a white dwarf system. ...

A Radio Pulsing White Dwarf Binary Star - T. R. Marsh et al
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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by Ann » Thu Jul 28, 2016 9:09 pm

That's amazing! :shock:
Vela pulsar and jet (and smile).
Photo: NASA/CXC/University of Toronto/M. Durant et al.
I thought only pulsars could do that sort of thing. And black holes.

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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by Ann » Thu Jul 28, 2016 9:55 pm

3C321 system: Bully galaxy zaps neigbour.
Xray: NASA/CXC/CfA/D Evans et al; Optical/UV: NASA/STScI;
Radio: NSF/VLA/CfA/D Evans et al, STFC/JBO/MERLIN
Even galaxies can zap one another:
Larry O'Hanlon, Discovery News, wrote:

Astronomers have spotted a distant galaxy zapping its smaller neighbour with a deadly particle beam.

The beam is a jet of particles moving at near light-speed out of a super-massive black hole at the centre of the larger galaxy.

The beam has smashed into the nearby second galaxy, where it is probably destroying an untold number of planets.

"There will be bad effects on earth-like planets," says astronomer Dr Daniel Evans of Harvard-Smithsonian Center for Astrophysics...
Imagine the Andromeda galaxy zapping the Milky Way with a deadly particle beam. Imagine the Andromeda galaxy zapping the Earth with a deadly particle beam!!! :ohno:

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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by neufer » Fri Jul 29, 2016 3:33 pm

Ann wrote:
I thought only pulsars could do that sort of thing. And black holes.
Stellar magnetic field strengths seem to be (roughly) inversely proportional to the star's surface area with magnestar neutron stars in the gigatesla range but with white dwarfs only reaching into the kilotesla range. While white dwarfs cannot thus (in and of themselves) generate gamma & X-ray synchrotron radiation they are perfectly capable of accelerating local particle beams that can then interact with nearby objects.
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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by Ann » Fri Jul 29, 2016 4:36 pm

neufer wrote:
Ann wrote:
I thought only pulsars could do that sort of thing. And black holes.
Stellar magnetic field strengths seem to be (roughly) inversely proportional to the star's surface area with magnestar neutron stars in the gigatesla range but with white dwarfs only reaching into the kilotesla range. While white dwarfs cannot thus (in and of themselves) generate gamma & X-ray synchrotron radiation they are perfectly capable of accelerating local particle beams that can then interact with nearby objects.
Thanks for the info, Art! :D

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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by Ann » Fri Jul 29, 2016 4:39 pm

neufer wrote:
Ann wrote:
I thought only pulsars could do that sort of thing. And black holes.
Stellar magnetic field strengths seem to be (roughly) inversely proportional to the star's surface area with magnestar neutron stars in the gigatesla range but with white dwarfs only reaching into the kilotesla range. While white dwarfs cannot thus (in and of themselves) generate gamma & X-ray synchrotron radiation they are perfectly capable of accelerating local particle beams that can then interact with nearby objects.
Thanks for the info, Art! :D

And hey... this was my post #7227. I think that must mean something!

Maybe it means this? Or this? Or this? Or this? Or this? Or this? Or this? Or this? Or... oh well, I give up already.

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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by Ann » Sat Jul 30, 2016 6:24 am

One more question, Art, or Chris. This is what Chris wrote in response to starsurfer regarding the planetary nebula M2-9:
Well, it's a big universe and there's a lot of stuff out there, but are there planetary nebulas where their central stars have accretion discs? I can't think of any, and it isn't clear to me how that could even happen. Planetary nebulas are just the glow of ejected gas from late-state, lower mass stars which are hot enough to ionize that gas. Isotropically hot, no stellar structure, no stellar jets, just 30,000 K blackbodies.
Is it true that the central stars of planetary nebulas don't have jets, but once they have shed their planetary nebula cocoons some of them might produce jets?

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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by neufer » Sat Jul 30, 2016 10:06 am

Ann wrote:
Well, it's a big universe and there's a lot of stuff out there, but are there planetary nebulas where their central stars have accretion discs? I can't think of any, and it isn't clear to me how that could even happen. Planetary nebulas are just the glow of ejected gas from late-state, lower mass stars which are hot enough to ionize that gas. Isotropically hot, no stellar structure, no stellar jets, just 30,000 K blackbodies.
Is it true that the central stars of planetary nebulas don't have jets, but once they have shed their planetary nebula cocoons some of them might produce jets?
  • Nobody understands planetary nebula very well.
https://en.wikipedia.org/wiki/Planetary_nebula wrote: <<A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from old red giant stars late in their lives. A mechanism for formation of most planetary nebulae is thought to be the following: at the end of the star's life, during the red giant phase, the outer layers of the star are expelled by strong stellar winds. After most of the red giant's atmosphere is dissipated, the ultraviolet radiation of the hot luminous core, called a Planetary Nebula Nucleus (PNN), ionizes the outer layers earlier ejected from the star. Absorbed ultraviolet light energises the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula.

A wide variety of shapes exist with some very complex forms seen. Planetary nebulae are classified by different authors into: stellar, disk, ring, irregular, helical, bipolar, quadrupolar, and other types, although the majority of them belong to just three types: spherical, elliptical and bipolar. Bipolar nebulae are concentrated in the galactic plane, likely produced by relatively young massive progenitor stars; and bipolars in the galactic bulge appear to prefer orienting their orbital axes parallel to the galactic plane. Only about 20% of planetary nebulae are spherically symmetric (e.g., Abell 39). Spherical nebulae are likely produced by the old stars similar to the Sun.

The huge variety of the shapes is partially the projection effect—the same nebula when viewed under different angles will appear different. Nevertheless, the reason for the huge variety of physical shapes is not fully understood. Gravitational interactions with companion stars if the central stars are double stars may be one cause. Another possibility is that planets disrupt the flow of material away from the star as the nebula forms. It has been determined that the more massive stars produce more irregularly shaped nebulae. In January 2005, astronomers announced the first detection of magnetic fields around the central stars of two planetary nebulae, and hypothesized that the fields might be partly or wholly responsible for their remarkable shapes.>>
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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by Chris Peterson » Sat Jul 30, 2016 2:10 pm

neufer wrote:Nobody understands planetary nebula very well.
What I would say is that planetary nebulas themselves are quite well understood, but the details of how the material is actually ejected remain poorly understood. You might say that's a minor semantic difference, but I think it's important to emphasize just which aspects of planetary nebulas remain unclear- basically, details of formation, not of behavior or evolution.
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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by Chris Peterson » Sat Jul 30, 2016 2:13 pm

Ann wrote:One more question, Art, or Chris. This is what Chris wrote in response to starsurfer regarding the planetary nebula M2-9:
Well, it's a big universe and there's a lot of stuff out there, but are there planetary nebulas where their central stars have accretion discs? I can't think of any, and it isn't clear to me how that could even happen. Planetary nebulas are just the glow of ejected gas from late-state, lower mass stars which are hot enough to ionize that gas. Isotropically hot, no stellar structure, no stellar jets, just 30,000 K blackbodies.
Is it true that the central stars of planetary nebulas don't have jets, but once they have shed their planetary nebula cocoons some of them might produce jets?
I can easily believe that in the case of the central "star" in a PN being a binary, we could see accretion and therefore phenomena like jets. Nevertheless, I'm not familiar with any PNs that display jets. Not saying they don't exist, but at the least, they must be quite rare given how many PN examples we have without them.
Chris

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Warwick: Mysterious White Dwarf Pulsar Discovered

Post by bystander » Tue Feb 07, 2017 6:35 pm

Mysterious White Dwarf Pulsar Discovered
University of Warwick, UK | 2016 Feb 07

An exotic binary star system 380 light-years away has been identified as an elusive white dwarf pulsar -- the first of its kind ever to be discovered in the universe -- thanks to research by the University of Warwick.

Professors Tom Marsh and Boris Gänsicke of the University of Warwick’s Astrophysics Group, with Dr. David Buckley from the South African Astronomical Observatory, have identified the star AR Scorpii (AR Sco) as the first white dwarf version of a pulsar -- objects found in the 1960s and associated with very different objects called neutron stars.

The white dwarf pulsar has eluded astronomers for over half a century.

AR Sco contains a rapidly spinning, burnt-out stellar remnant called a white dwarf, which lashes its neighbour -- a red dwarf -- with powerful beams of electrical particles and radiation, causing the entire system to brighten and fade dramatically twice every two minutes.

The latest research establishes that the lash of energy from AR Sco is a focused ‘beam,’ emitting concentrated radiation in a single direction -- much like a particle accelerator -- something which is totally unique in the known universe. ...

Polarimetric Evidence of a White Dwarf Pulsar in the Binary System AR Scorpii - D. A. H. Buckley et al
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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by Ann » Wed Feb 08, 2017 4:20 am

University of Warwick wrote:
An exotic binary star system 380 light-years away has been identified as an elusive white dwarf pulsar – the first of its kind ever to be discovered in the universe – thanks to research by the University of Warwick.
...
The latest research establishes that the lash of energy from AR Sco is a focused ‘beam’, emitting concentrated radiation in a single direction – much like a particle accelerator – something which is totally unique in the known universe.
No other objects like this one is known, then, at least not another object which emits concentrated radiation in a single direction.
The white dwarf in AR Sco is the size of Earth but 200,000 times more massive, and is in a 3.6 hour orbit with a cool star one third the mass of the Sun.
The mass of the Sun is about 300,000 times the mass of the Earth, which suggests that AR Sco is about two thirds the mass of the Sun. And the red dwarf companion is one third the mass of the Sun. That would make the white dwarf about twice as massive as its companion.
With an electromagnetic field 100 million times more powerful than Earth, and spinning on a period just shy of two minutes, AR Sco produces lighthouse-like beams of radiation and particles, which lash across the face of the cool star, a red dwarf.
...
The distance between the two stars is around 1.4 million kilometres – which is three times the distance between the Moon and the Earth.
AR Sco is spinning very fast. Isn't it true that in a tight binary - and the AR Sco binary is very tight - the more massive component can be "spun up" by its less massive companion? And isn't a high rotation speed, along with magnetism, associated with jets in pulsars?
"AR Sco is like a gigantic dynamo: a magnet, size of the Earth, with a field that is ~10.000 stronger than any field we can produce in a laboratory, and it is rotating every two minutes. This generates an enormous electric current in the companion star, which then produces the variations in the light we detect."
Alpha (left) and Beta (right) Centauri.
Photo (I think): Ken Croswell.
AR Sco lies in the constellation Scorpius, 380 light-years from Earth, a close neighbour in astronomical terms.

The fact that AR Sco is located 380 light-years away in Scorpius strongly suggests that it is a member of the Sco-Cen association of B-type stars, many of which are about 400 light-years away.

One famous star that is located almost exactly 380 light-years away is Beta Centauri, which is seemingly situated right next to the Earth's next-door neighbour, Alpha Centauri.

Beta Centauri is a binary star, consisting of (according to Jim Kaler) two main sequence stars of spectral class B1. It is interesting to think that Beta Centauri may be related, however distantly, to AR Sco.

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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by neufer » Wed Feb 08, 2017 4:38 am

Ann wrote:
University of Warwick wrote:
An exotic binary star system 380 light-years away has been identified as an elusive white dwarf pulsar – the first of its kind ever to be discovered in the universe – thanks to research by the University of Warwick.
...
The latest research establishes that the lash of energy from AR Sco is a focused ‘beam’, emitting concentrated radiation in a single direction – much like a particle accelerator – something which is totally unique in the known universe.
No other objects like this one is known, then, at least not another object which emits concentrated radiation in a single direction.
The key here is the pulse timing: just once every 1.97 minutes with radiation ranging from the ultraviolet to radio.

A neutron star pulsar has periods that range from milliseconds to seconds
(; radio pulsar, PSR J2144-3933, has the longest period of 8.51 seconds)
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Re: HEIC/ESO: White Dwarf Lashes Red Dwarf with Mystery Ray

Post by Ann » Wed Feb 08, 2017 8:59 am

neufer wrote:
Ann wrote:
University of Warwick wrote:
An exotic binary star system 380 light-years away has been identified as an elusive white dwarf pulsar – the first of its kind ever to be discovered in the universe – thanks to research by the University of Warwick.
...
The latest research establishes that the lash of energy from AR Sco is a focused ‘beam’, emitting concentrated radiation in a single direction – much like a particle accelerator – something which is totally unique in the known universe.
No other objects like this one is known, then, at least not another object which emits concentrated radiation in a single direction.
The key here is the pulse timing: just once every 1.97 minutes with radiation ranging from the ultraviolet to radio.

A neutron star pulsar has periods that range from milliseconds to seconds
(; radio pulsar, PSR J2144-3933, has the longest period of 8.51 seconds)
Good point, but a neutron star that is a pulsar is also very much smaller than a white dwarf. It is not comparable to the Earth in size.

Rotating a body the size of the Earth in two minutes requires perhaps almost the same velocity as rotating a body comparable to a spherical New York in 8 seconds?

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