Two white dwarf stars orbiting each other every five minutes, confirmed
Yousuf Khan
each other some day. This would be an ideal test to see if two white
dwarfs falling into each other produce a Type Ia supernova, leaving
nothing behind. Or if they simply turn into a neutron star.
Yousuf Khan
***
SPACE.com -- Fastest Orbiting Stars Circle Each Other in Mere Minutes
"After a decade of mystery, astronomers have now shown that a pair of
white dwarf stars spin around each other in just 5.4 minutes, making
them the fastest-orbiting and tightest binary star system ever found,
the researchers claim.
The record-setting stellar duo, known as HM Cancri or RX J0806.3+1527,
offer challenges in explaining how such a system might form. The
super-quick stars may also present a great future test-bed for detecting
gravitational waves, which are elusive ripples in space-time."
http://www.space.com/scienceastronomy/fastest-orbiting-stars-100309.html
Andrew Usher
> These two white dwarfs are so close together, that they might fall into
> each other some day. This would be an ideal test to see if two white
> dwarfs falling into each other produce a Type Ia supernova, leaving
> nothing behind. Or if they simply turn into a neutron star.
How long should it be before we see the merger?
Andrew Usher
Brad Guth
At 1600 light years, it probably already happened as of more than a
thousand years ago.
~ BG
Andrew Usher
Can anyone confirm this? Guth is hardly reliable, and I have no idea
how to calculate it myself.
Andrew Usher
Brad Guth
JPL has way more than enough supercomputer and those 3D interactive
simulators for orbital motions that'll make such matters child's play.
There's actually any dozen or more public funded supercomputers that
are over-qualified as is, so don't blame little old me.
It has been a good 8+ years, so the rate of those X-ray cycles of
321.5 seconds has changed by what amount?
~ BG
Andrew Usher
> On Mar 10, 6:40 pm, Andrew Usher <k_over_hb...@yahoo.com> wrote:
>
>
>
> > Brad Guth wrote:
> > > On Mar 9, 4:29 pm, Andrew Usher <k_over_hb...@yahoo.com> wrote:
> > > > Yousuf Khan wrote:
> > > > > These two white dwarfs are so close together, that they might fall into
> > > > > each other some day. This would be an ideal test to see if two white
> > > > > dwarfs falling into each other produce a Type Ia supernova, leaving
> > > > > nothing behind. Or if they simply turn into a neutron star.
>
> > > > How long should it be before we see the merger?
>
> > > > Andrew Usher
>
> > > At 1600 light years, it probably already happened as of more than a
> > > thousand years ago.
>
> > Can anyone confirm this? Guth is hardly reliable, and I have no idea
> > how to calculate it myself.
<snip>
Yousuf Khan
I think the major problem here is calculating frame dragging friction,
which requires Einstein's equations. I don't know how to do it, myself.
The 1600 light-year distance between us and this system is a negligible
calculation by comparison.
Yousuf Khan
Brad Guth
Binary dwarfs as tidal locked, separated by just 80,000 km and .37
solar mass each.
“ABSTRACT. RX J0806.3+1527 is an ultracompact, double-degenerate
binary with the shortest known orbital period (321.5 s). Hakala et al.
have recently reported new optical measurements of the orbital
frequency of the source indicating that the frequency has increased
over the 9 yr since the earliest ROSAT observations.”
http://www.iop.org/EJ/article/0004-637X/627/2/920/62306.text.html
RX J0806.3+1527 is a candidate double-degenerate binary with possibly
the shortest known orbital period. The source shows an 100% X-ray
intensity modulation at the putative orbital frequency of 3.11 mHz
(321.5 s). If the system is a detached, ultracompact binary,
gravitational radiation should drive spin-up with a magnitude of
10-16 Hz s-1. Efforts to constrain the X-ray frequency evolution to
date have met with mixed success, principally due to the sparseness of
earlier observations. Here we describe the results of the first phase-
coherent X-ray monitoring campaign on RX J0806.3+1527 with Chandra. We
obtained a total of 70 ks of exposure in six epochs logarithmically
spaced over 320 days. With these data we conclusively show that the X-
ray frequency is increasing at a rate of (3.77 ± 0.8) × 10-16 Hz s-1.
Using the ephemeris derived from the new data, we are able to phase up
all the earlier Chandra and ROSAT data and show that they are
consistent with a constant = (3.63 ± 0.06) × 10-16 Hz s-1 over the
past decade. This value appears consistent with that recently derived
by Israel et al., largely from monitoring of the optical modulation,
and is in rough agreement with the solutions reported initially by
Hakala et al., based on ground-based optical observations. The large
and stable over a decade is consistent with gravitational radiation
losses driving the evolution. An intermediate polar (IP) scenario in
which the observed X-ray period is the spin period of an accreting
white dwarf appears less tenable because the observed requires an 2
× 10-8 M yr-1, which is much larger than that inferred from the
observed X-ray luminosity (although this depends on the uncertain
distance and bolometric corrections), and it is difficult to drive
such a high in a binary system with parameters consistent with all
the multiwavelength data. If the ultracompact scenario is correct,
then the X-ray flux cannot be powered by stable accretion, which would
drive the components apart, suggesting that a new type of energy
source (perhaps electromagnetic) may power the X-ray flux.
-
Clearly they are not getting further apart.
~ BG
Andrew Usher
> I think the major problem here is calculating frame dragging friction,
> which requires Einstein's equations. I don't know how to do it, myself.
> The 1600 light-year distance between us and this system is a negligible
> calculation by comparison.
I thought it should have been calculated when this system was
discovered. Surely the merger of two white dwarfs is an interesting
occurrence! I'm wondering, if the two WDs are both ONe (making a
supernova impossible), would they become a neutron star or a black
hole?
Andrew Usher
Yousuf Khan
Neutron star, if they don't blow up instead.
Yousuf Khan
Brad Guth
Binary dwarfs as supposedly tidal face-locked and separated by just
80,000 km and .37 solar mass each.
At some point in the near future, their ever increasing orbital
frequency and the combined magnetic force has to take over and draw
these two similar white dwarfs together, unless it’s running like a
magnetic bearing that’s perpetually isolating one another regardless
of those substantial gravitational forces (5.7e33 N). Electrons also
repulse one another, which should also help prolong their binary
status. At only 80,000 km separation, whereas being near equal mass
is pretty much required, and otherwise I agree with Yousuf Khan.
~ BG
Steve Willner
Yousuf Khan <bbb...@spammenot.yahoo.com> writes:
>http://www.space.com/scienceastronomy/fastest-orbiting-stars-100309.html
I can't offer an exact calculation of the time until merger, but the
paper (Roelofs et al. 2010 ApJL 711, L138) gives an orbital frequency
of about 3 mHz and derivative (df/dt) of about 3.6E-16 Hz/s.
Dividing these gives 8E12 s or about 3E5 years. This is just a very
rough estimate, of course.
--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123 swil...@cfa.harvard.edu
Cambridge, MA 02138 USA
Brad Guth
> In article <4b96da8...@news.bnb-lp.com>,
> Yousuf Khan <bbb...@spammenot.yahoo.com> writes:
>
> >http://www.space.com/scienceastronomy/fastest-orbiting-stars-100309.html
>
> I can't offer an exact calculation of the time until merger, but the
> paper (Roelofs et al. 2010 ApJL 711, L138) gives an orbital frequency
> of about 3 mHz and derivative (df/dt) of about 3.6E-16 Hz/s.
> Dividing these gives 8E12 s or about 3E5 years. This is just a very
> rough estimate, of course.
>
> --
> Help keep our newsgroup healthy; please don't feed the trolls.
> Cambridge, MA 02138 USA
It could be a whole lot sooner than 300,000 years. The current -2
feet/day could turn into losing three, four, eight, sixteen/day and so
forth within hardly a thousand years.
"Chandra data (above, graph) from observations of RX J0806.3+1527 (or
J0806), show that its X-ray intensity varies with a period of 321.5
seconds. This implies that J0806 is a binary star system where two
white dwarf stars are orbiting each other (above, illustration)
approximately every 5 minutes.
The short orbital period implies that the stars are only about 50,000
miles apart, a fifth of the distance from the Earth to the Moon, and
are moving in excess of a million miles per hour. According to
Einstein's General Theory of Relativity, such a system should produce
gravitational waves -ripples in space-time - that carry energy away
from the system at the speed of light.
Energy loss by gravitational waves will cause the stars to move
closer
together. X-ray and optical observations indicate that the orbital
period of this system is decreasing by 1.2 milliseconds every year,
which means that the stars are moving closer together at a rate of
about 2 feet per day."
http://chandra.harvard.edu/photo/2005/j0806/
http://i.ytimg.com/vi/ryqN6dyUmJg/0.jpg
"With its extremely short orbital period, RX J0806.3+1527 is also a
prime candidate for the detection of the elusive gravitational waves,
predicted by Einstein's General Theory of Relativity. They have never
been measured directly, but their existence has been revealed
indirectly in binary neutron star systems.
A planned gravitational wave space experiment, the European Space
Agency's Laser Interferometer Space Antenna (LISA) that will be
launched in about 10 years' time, will be sufficiently sensitive to
be
able to reveal this radiation from RX J0806.3+1527 with a high degree
of confidence. Such an observational feat would open an entirely new
window on the universe."
http://www.eso.org/public/news/eso0211/
Binary dwarfs as supposedly tidal face-locked and separated by just
80,000 km and worth .37 solar mass each. At some point in the near
future (perhaps a few thousands years from now), their ever increasing
orbital frequency and the combined magnetic force has to take over and
draw these two similar white dwarfs together, unless it’s running like
a magnetic bearing that’s perpetually isolating one another regardless
of those substantial gravitational forces (5.7e33 N). Electrons
repulse one another, which should also help prolong their binary
status. At only 80,000 km separation, whereas being near equal mass
is pretty much required, and otherwise I agree with the final outcome
being a neutron star unless the merger goes into a hyper/superluminal
explosion where everything gets expelled.
It’s actually more likely that Sirius(B) gets to become a neutron star
about the same time as the human species goes extinct here on Earth.
~ BG
Dr J R Stockton
oglegroups.com>, Wed, 10 Mar 2010 18:40:50, Andrew Usher
<k_over...@yahoo.com> posted:
Other sources have 16,000 light years. But is Guth not *consistently*
wrong?
Wikipedia <http://en.wikipedia.org/wiki/HM_Cancri> says that Chandra
shows that they are currently closing by about two feet per day, which
is about a tenth of a mile per year. Wiki gives the separation as
50,000 miles. The closure rate will change with distance; but it would
be IMHO remarkable if closure was expected in Guth's estimate of under
600 years, and surprising if under 16,000 years ERT.
--
(c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk Turnpike v6.05 MIME.
Web <URL:http://www.merlyn.demon.co.uk/> - FAQqish topics, acronyms & links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.
Andrew Usher
> Wikipedia <http://en.wikipedia.org/wiki/HM_Cancri> says that Chandra
> shows that they are currently closing by about two feet per day, which
> is about a tenth of a mile per year. Wiki gives the separation as
> 50,000 miles. The closure rate will change with distance; but it would
> be IMHO remarkable if closure was expected in Guth's estimate of under
> 600 years, and surprising if under 16,000 years ERT.
Thanks, this is what I needed. It will be over 100,000 years then, and
we will not see it.
It makes you wonder how they could have closed to the distance they
are right now. I think gravitational radiation goes as (v'')^2 or 1/
r^7. Since potential energy goes as 1/r, dr/dt ~ 1/r^5. So in the
entire age of the galaxy, they could only have closed from about 8
times as far as they are now, which is absurd. Or is there another
factor?
Andrew Usher
Andrew Usher
> > I thought it should have been calculated when this system was
> > discovered. Surely the merger of two white dwarfs is an interesting
> > occurrence! I'm wondering, if the two WDs are both ONe (making a
> > supernova impossible), would they become a neutron star or a black
> > hole?
>
> Neutron star, if they don't blow up instead.
Oxygen-neon white dwarfs are at least 1.05 Msun and up to 1.37, so the
combined mass could be 2.1-2.75 Msun. The limit for a neutron star is
thought to be about 2.2, but could it lose enough mass while colliding
to avoid becoming a black hole?
Andrew Usher
Brad Guth
> Dr J R Stockton wrote:
>
> > Wikipedia <http://en.wikipedia.org/wiki/HM_Cancri> says that Chandra
> > shows that they are currently closing by about two feet per day, which
> > is about a tenth of a mile per year. Wiki gives the separation as
> > 50,000 miles. The closure rate will change with distance; but it would
> > be IMHO remarkable if closure was expected in Guth's estimate of under
> > 600 years, and surprising if under 16,000 years ERT.
>
> Thanks, this is what I needed. It will be over 100,000 years then, and
> we will not see it.
I wouldn't go with 100,000 years. My initial swag of 600 years is a
wee bit short, although a few thousand years might be more likely.
>
> It makes you wonder how they could have closed to the distance they
> are right now. I think gravitational radiation goes as (v'')^2 or 1/
> r^7. Since potential energy goes as 1/r, dr/dt ~ 1/r^5. So in the
> entire age of the galaxy, they could only have closed from about 8
> times as far as they are now, which is absurd. Or is there another
> factor?
>
> Andrew Usher
Cosmic mergers, like the one(s) which created our galaxy and gave
birth to the likes of Sirius ABC. Also, nothing out there runs
linear. Ever heard of the golden ratio or phi = 1.618034
~ BG
Yousuf Khan
My feeling is that the limit is thought to be 2.8 Msun between neutron
star and black hole, though I'm sure there's plenty of overlap here. The
smallest stellar mass black hole found to date is about 3.8 Msun, though
we might find smaller.
XTE J1650-500 - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/XTE_J1650-500
Whether a core becomes a neutron star or a black hole probably depends
on how much compression it underwent when being formed during original
blow-off phase. Usually that amount of compression is dependent on the
mass of the progenitor star, but it wouldn't surprise me that some
nuclear forces could aid gravity in the compression mechanism, thus
within certain range of masses we might see some become black holes and
some become neutron stars. Thus I don't see two white dwarfs ever
forming a black hole, because they simply don't create a compressive
force on each other's cores when they merge; in fact, I'd say it's
mostly tensile during this time.
Now as for the 2.2 Msun neutron star limit, that may just be the limit
for normal neutron stars. There are subspecies of neutron stars that
have been proposed with higher masses, such as: quark stars, strange
stars, and most recently electroweak stars.
Yousuf Khan
Yousuf Khan
> Thanks, this is what I needed. It will be over 100,000 years then, and
> we will not see it.
>
> It makes you wonder how they could have closed to the distance they
> are right now. I think gravitational radiation goes as (v'')^2 or 1/
> r^7. Since potential energy goes as 1/r, dr/dt ~ 1/r^5. So in the
> entire age of the galaxy, they could only have closed from about 8
> times as far as they are now, which is absurd. Or is there another
> factor?
>
> Andrew Usher
They're only this close because they have been orbiting within each
other's gas envelopes as each one took their turns becoming red giants.
Combination of aerodynamic friction and gas exchange changing up their
orbital relationships. Now that neither of them have any gas left, they
will only approach each other through the gravitational friction method.
Yousuf Khan
Brad Guth
Plus attracted to one another by their magnetic forces (especially if
poles flip) which can be rather considerable.
~ BG
Yousuf Khan
> Plus attracted to one another by their magnetic forces (especially if
> poles flip) which can be rather considerable.
Magnetic attraction is balanced out by magnetic repulsion. The only
thing magnetism will serve to do is tidally lock them into position quicker.
Gravity is the only force at work here.
Yousuf Khan
Brad Guth
Gravity is an extremely weak force.
Those white dwarfs have a lot going for them, except having too few of
those repulsive elections to keep themselves apart.
One pole flip and it's magnetic attraction of that pair of perhaps 1e6
gauss stars merging very quickly.
~ BG
Yousuf Khan
> Gravity is an extremely weak force.
>
> Those white dwarfs have a lot going for them, except having too few of
> those repulsive elections to keep themselves apart.
>
> One pole flip and it's magnetic attraction of that pair of perhaps 1e6
> gauss stars merging very quickly.
Let's not forget how magnetic attraction and repulsion actually work:
the poles actually have to point towards each other. The poles in stars
are usually aligned parallel to each other. There is no net attraction
or repulsion there. It wouldn't matter if one star's pole is north and
the other star's pole is south, when they are parallel. There are
localized attractions and repulsions which would serve to sync up the
two stars' rotations with each other, but once synchronized, nothing
further happens.
Yousuf Khan
Brad Guth
You need to play with magnets before you assume anything, especially
about white dwarf stars that could represent 1e6 gauss each.
Try to orbit powerful magnets in open space as a simulation, such as
within the zero delta V of our moon-Earth L1(Selene L1). Whatever you
do, don't place yourself in the center.
The natural order of magnetic items is to join up or merge together
and stay that way.
~ BG
Brad Guth
Apparently if these two eventually merge, their combined mass isn't
going to trigger a supernova, instead just a normal stellar explosion
of 0.01 c or less.
Any ideas as to their individual gauss?
~ BG
~ BG
Brad Guth
Apparently white dwarfs can go with 2+ solar masses, so perhaps most
everything we know about white dwarfs is at risk.
These two little dwarfs magnetically combining would hardly make a
bang, much less a supernova.
~ BG
Yousuf Khan
> Apparently white dwarfs can go with 2+ solar masses, so perhaps most
> everything we know about white dwarfs is at risk.
>
> These two little dwarfs magnetically combining would hardly make a
> bang, much less a supernova.
They're talking about the combined mass of the two white dwarfs together
as about 2+ Msun, not either WD individually. Of course the maximum any
single WD can go upto is just slightly less than 1.4 Msun (i.e.
Chandrasekhar Limit).
Yousuf Khan