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Another test for Einstein:


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https://phys.org/news/2018-02-astronomers-s0-star-ready-big.html

 

Astronomers discover S0-2 star is single and ready for big Einstein test

February 22, 2018, W. M. Keck Observatory

The orbit of S0-2 (light blue) located near the Milky Way's supermassive black hole will be used to test Einstein's Theory of General Relativity and generate potentially new gravitational models. Credit: W. M. Keck Observatory

Astronomers have the "all-clear" for an exciting test of Einstein's Theory of General Relativity, thanks to a new discovery about S0-2's star status.

Up until now, it was thought that S0-2 may be a binary, a system where two stars circle around each other. Having such a partner would have complicated the upcoming gravity test.

But in a study published recently in the Astrophysical Journal, a team of astronomers led by a UCLA scientist from Hawaii has found that S0-2 does not have a significant other after all, or at least one that is massive enough to get in the way of critical measurements that astronomers need to test Einstein's theory.

The researchers made their discovery by obtaining spectroscopic measurements of S0-2 using W. M. Keck Observatory's OH-Suppressing Infrared Imaging Spectrograph (OSIRIS) and Laser Guide Star Adaptive Optics.



Read more at: https://phys.org/news/2018-02-astronomers-s0-star-ready-big.html#jCp
 

 

the paper: 

http://iopscience.iop.org/article/10.3847/1538-4357/aaa3eb/meta

Investigating the Binarity of S0-2: Implications for Its Origins and Robustness as a Probe of the Laws of Gravity around a Supermassive Black Hole:

 

Abstract

The star S0-2, which orbits the supermassive black hole (SMBH) in our Galaxy with a period of 16 years, provides the strongest constraint on both the mass of the SMBH and the distance to the Galactic center. S0-2 will soon provide the first measurement of relativistic effects near a SMBH. We report the first limits on the binarity of S0-2 from radial velocity (RV) monitoring, which has implications for both understanding its origin and robustness as a probe of the central gravitational field. With 87 RV measurements, which include 12 new observations that we present, we have the requisite data set to look for RV variations from S0-2's orbital model. Using a Lomb–Scargle analysis and orbit-fitting for potential binaries, we detect no RV variation beyond S0-2's orbital motion and do not find any significant periodic signal. The lack of a binary companion does not currently distinguish different formation scenarios for S0-2. The upper limit on the mass of a companion star () still allowed by our results has a median upper limit of  sin i ≤ 1.6 M ⊙ for periods between 1 and 150 days, the longest period to avoid tidal break-up of the binary. We also investigate the impact of the remaining allowed binary system on the measurement of the relativistic redshift at S0-2's closest approach in 2018. While binary star systems are important to consider for this experiment, we find that plausible binaries for S0-2 will not alter a 5σ detection of the relativistic redshift.

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OK, my main question [ and possible answer] is also the one referred to in the article, and summed up in the following extract....

"The study also sheds more light on the strange birth of S0-2 and its stellar neighbors in the S-Star Cluster. The fact that these stars exist so close to the supermassive black hole is unusual because they are so young; how they could've formed in such a hostile environment is a mystery.

"Star formation at the Galactic Center is difficult because the brute strength of tidal forces from the black hole can tear gas clouds apart before they can collapse and form stars," said Do.

"S0-2 is a very special and puzzling star," said Chu. "We don't typically see young, hot stars like S0-2 form so close to a supermassive black hole. This means that S0-2 must have formed a different way."

OK, while this star is fairly large, wouldn't the answer to where it formed, be instead that it was actually ejected, possibly in its proto stage from another system within the galactic buldge? 

 

The other point I find so enthralling and revealing about this article and paper, is again, another example of the fact that science and scientists are forever trying and testing out incumbent theories, even those of Einstein. Whoever ends up finding any flaw in GR, will have his name up in lights. If ever GR is invalidated or falsified, or some limitation on its predictiveness is found, it will be from the inside mainstream.
 

 

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