The strange case of the missing dwarf

February 18, 2015, ESO
The SPHERE instrument is shown shortly after it was installed on ESO's VLT Unit Telescope 3. The instrument itself is the black box, located on the platform to one side of the telescope. Credit: ESO/J. Girard

The new SPHERE instrument on ESO's Very Large Telescope has been used to search for a brown dwarf expected to be orbiting the unusual double star V471 Tauri. SPHERE has given astronomers the best look so far at the surroundings of this intriguing object and they found—nothing. The surprising absence of this confidently predicted brown dwarf means that the conventional explanation for the odd behavior of V471 Tauri is wrong.

Some pairs of stars consist of two normal stars with slightly different masses. When the star of slightly higher mass ages and expands to become a red giant, material is transferred to other star and ends up surrounding both stars in a huge gaseous envelope. When this cloud disperses the two move closer together and form a very tight pair with one white dwarf , and one more normal star.

One such stellar pair is called V471 Tauri. It is a member of the Hyades star cluster in the constellation of Taurus and is estimated to be around 600 million years old and about 163 light-years from Earth. The two stars are very close and orbit each other every 12 hours. Twice per orbit one star passes in front of the other—which leads to regular changes in the brightness of the pair observed from Earth as they eclipse each other.

A team of astronomers led by Adam Hardy (Universidad Valparaíso, Valparaíso, Chile) first used the ULTRACAM system on ESO's New Technology Telescope to measure these brightness changes very precisely. The times of the eclipses were measured with an accuracy of better than two seconds—a big improvement on earlier measurements.

The eclipse timings were not regular, but could be explained well by assuming that there was a brown dwarf orbiting both stars whose gravitational pull was disturbing the orbits of the stars. They also found hints that there might be a second small companion object.

Up to now however, it has been impossible to actually image a faint brown dwarf so close to much brighter stars. But the power of the newly installed SPHERE instrument on ESO's Very Large Telescope allowed the team to look for the first time exactly where the brown dwarf companion was expected to be. But they saw nothing, even though the very high quality images from SPHERE should have easily revealed it.

"There are many papers suggesting the existence of such circumbinary objects, but the results here provide damaging evidence against this hypothesis," remarks Adam Hardy.

If there is no orbiting object then what is causing the odd changes to the orbit of the binary? Several theories have been proposed, and, while some of these have already been ruled out, it is possible that the effects are caused by magnetic field variations in the larger of the two , somewhat similar to the smaller changes seen in the Sun.

"A study such as this has been necessary for many years, but has only become possible with the advent of powerful new instruments such as SPHERE. This is how science works: observations with new technology can either confirm, or as in this case disprove, earlier ideas. This is an excellent way to start the observational life of this amazing instrument," concludes Adam Hardy.

This research was presented in a paper entitled "The First Science Results from SPHERE: Disproving the Predicted Brown Dwarf around V471 Tau" by A. Hardy et al., to appear in the Astrophysical Journal Letters on 18 February 2015.

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HannesAlfven
1 / 5 (4) Feb 18, 2015
The decision to observe exclusively through the lens of the textbook worldview creates the very problem that must now be solved. A more inclusive forced induction would also consider stellar expulsions, stellar fissioning, and even charge exchange between these bodies -- all of which might not be a part of the SSM, yet are far more classical than other accepted theories in mainstream astrophysics & cosmology today.

It seems to me that the astrophysical discipline has forgotten the danger of the theory-of-laddeness problem. Maybe it's because they have completely abandoned philosophy of science.
Captain Stumpy
4.2 / 5 (5) Feb 18, 2015
...completely abandoned philosophy of science.
@alfvie
regardless of the historical posts of yours, you've never been able to demonstrate how modern astrophysicists ignore any science, whereas just by reading ANYTHING on the electric universe pseudoscience site which you support so wholeheartedly, we can plainly see that the eu crown regularly refuses to acknowledge actual physics as well as modern experimental evidence and modern astrophysics, to tell the truth

this can be best demonstrated by the exchange between eu pseudoscience being shared by cantdtrive and actual physics being espoused by Thompson here: http://phys.org/n...ggs.html

again, science follows the evidence
whereas pseudoscience (and the eu crowd) establish the facts to be followed with strict rigidity, then claim science to be wrong

you going to make the same "don't know plasma physics" BS that cd does?
or quote everyone else wrong thought processes?
(again)
gulfcoastfella
not rated yet Feb 20, 2015
"This research was presented in a paper entitled 'The First Science Results from SPHERE: Disproving the Predicted Brown Dwarf around V471 Tau' by A. Hardy et al., to appear in the Astrophysical Journal Letters on 18 February 2015."

Extra points for giving the paper a name that everyone can understand.

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