Stealthy Black Holes..

Interesting.. Maybe there are many more of these than we can ever realise and could that account for any percieved discrepancy in the mass of the Universe ?




www.dailygalaxy.com...< br />

By combining data from Chandra and several other telescopes, astronomers have identified the true nature of an unusual source in the Milky Way galaxy. This discovery implies that there could be a much larger number of black holes in the Galaxy that have previously been unaccounted for. For about two decades, astronomers have known about an object called VLA J213002.08+120904 (VLA J2130+12 for short). Although it is close to the line of sight to the globular cluster M15, most astronomers had thought that this source of bright radio waves was probably a distant galaxy. Thanks to recent distance measurements with an international network of radio telescopes, including the EVN (European Very Long Baseline Interferometry Network) telescopes, the NSF's Green Bank Telescope and Arecibo Observatory, astronomers realized that VLA J2130+12 is at a distance of 7,200 light years, showing that it is well within our own Milky Way galaxy and about five times closer than M15. A deep image from Chandra reveals it can only be giving off a very small amount of X-rays, while recent VLA data indicates the source remains bright in radio waves.

Also on the physics org site.

phys.org...

Usually, we find black holes when they are pulling in lots of material. Before falling into the black hole this material gets very hot and emits brightly in X-rays," said Bailey Tetarenko of the University of Alberta, Canada, who led the study. "This one is so quiet that it's practically a stealth black hole." Read more at: phys.org...

"Unless we were incredibly lucky to find one source like this in a small patch of the sky, there must be many more of these black hole binaries in our Galaxy than we used to think," said co-author Arash Bahramian, also of the University of Alberta. There are other implications of finding that VLA J2130+12 is relatively near to us. "Some of these undiscovered black holes could be closer to the Earth than we previously thought," said Robin Arnason, a co-author from Western University, Canada "However there's no need to worry as even these black holes would still be many light years away from Earth." Read more at: phys.org...

Abstract A wealth of astronomical data indicate the presence of mass discrepancies in the Universe. The motions observed in a variety of classes of extragalactic systems exceed what can be explained by the mass visible in stars and gas. Either (i) there is a vast amount of unseen mass in some novel form – dark matter – or (ii) the data indicate a breakdown of our understanding of dynamics on the relevant scales, or (iii) both. Here, we first review a few outstanding challenges for the dark matter interpretation of mass discrepancies in galaxies, purely based on observations and independently of any alternative theoretical framework. We then show that many of these puzzling observations are predicted by one single relation – Milgrom’s law – involving an acceleration constant a0 (or a characteristic surface density Σ† = a0/G) of the order of the square-root of the cosmological constant in natural units. This relation can at present most easily be interpreted as the effect of a single universal force law resulting from a modification of Newtonian dynamics (MOND) on galactic scales. We exhaustively review the current observational successes and problems of this alternative paradigm at all astrophysical scales, and summarize the various theoretical attempts (TeVeS, GEA, BIMOND, and others) made to effectively embed this modification of Newtonian dynamics within a relativistic theory of gravity

arxiv.org... ( 64 Pages PDF )

a reply to: skywatcher44

Soon they will discover a black body star. Stealth black holes and brown dwarves are leading us in this direction.

I tried to watch that video on my lunch break, but I fell asleep on the couch and now I'm late going back to work.

Stuff like this really interests me though. The universe always blows my mind, even if it puts me to sleep sometimes. I better run...

Karl G. Jansky VLA (phys.org says the New Mexico antennae were used as a source)? I had posted a little blurb on the updates they had done over here saying there would be more announcements made because of the details they gained in the upgrades. (At the end of the thread is a u-tube video on the VLA).

Glad to see it has happened! And we will continue to see it happen. It should fill the gap until the James Webb telescope starts sending back data. That and they can link up ground based radio telescopes with space based ones and see even more details. This is going to be a new age of discovery and a realization on how little we know!

S+F

originally posted by: skywatcher44
Interesting.. Maybe there are many more of these than we can ever realise and could that account for any percieved discrepancy in the mass of the Universe ?

If black holes account for any significant amount of dark matter they would need to have a small mass according to the following source, and one problem with that is that such small black holes have a tendency to "evaporate" according to theory:

Is Dark Matter Made of Tiny Black Holes?

Until now, researchers had eliminated the chances that black holes that are approximately the mass of the moon could make up dark matter. Kepler's data show no evidence of black holes between 5 and 80 percent of the moon's mass, suggesting these black holes could not constitute most dark matter.

However, even smaller primordial black holes, ones less than 0.0001 percent the mass of Earth's moon, could still make up the entirety of dark matter, Griest said. Future missions — such as the European Space Agency's Euclid spacecraft or NASA's proposed WFIRST satellite — could look for smaller black holes than those identified by the Kepler data.

"We've ruled out a range of primordial black holes as dark matter, but have not ruled them out completely," Griest told SPACE.com. "They're still a viable candidate for dark matter."

In order for such low mass black holes to exist, there would need to be something wrong with our theory that low mass black holes "evaporate", which is possible because that hasn't been confirmed with observation to my knowledge.

By the way I don't really trust the dailygalaxy as they've hosted some nonsense articles in the past though this probably isn't such an article, but still anything you find there I'd recommend trying to confirm with a better source. If it's a new paper you could look for the paper preprint on arxiv.org, then use that as a verifiable source.

a reply to: Arbitrageur

By the way I don't really trust the dailygalaxy as they've hosted some nonsense articles in the past though this probably isn't such an article, but still anything you find there I'd recommend trying to confirm with a better source. If it's a new paper you could look for the paper preprint on arxiv.org, then use that as a verifiable source.

Hi, I usually look for a verification story on Phys.org. The daily Galaxy I do trust as I have been reading from there for a few years, they do rehash earlier stories occasionally. Phys.org usually has the arxiv link..

arxiv.org... ( 13 Pages )

ABSTRACT
The observed relation between the X-ray and radio properties of low-luminosity accreting black holes has enabled the identification of multiple candidate black hole X-ray binaries (BHXBs) in globular clusters. Here we report an identification of the radio source VLA J213002.08+120904 (aka M15 S2), recently reported in Kirsten et al. 2014, as a BHXB candidate. They showed that the parallax of this flat-spectrum variable radio source indicates a 2.2+0.5 −0.3 kpc distance, which identifies it as lying in the foreground of the globular cluster M15. We determine the radio characteristics of this source, and place a deep limit on the X-ray luminosity of ∼ 4 × 1029 erg s−1 . Furthermore, we astrometrically identify a faint red stellar counterpart in archival Hubble images, with colors consistent with a foreground star; at 2.2 kpc its inferred mass is 0.1-0.2 M⊙. We rule out that this object is a pulsar, neutron star X-ray binary, cataclysmic variable, or planetary nebula, concluding that VLA J213002.08+120904 is the first accreting black hole X-ray binary candidate discovered in quiescence outside a globular cluster. Given the relatively small area over which parallax studies of radio sources have been performed, this discovery suggests a much larger population of quiescent BHXBs in our Galaxy, 2.6 × 104 − 1.7×108 BHXBs at 3σ confidence, than has been previously estimated (∼ 102 − 104 ) through population

Peace..