In 1966, Erast Gliner, a young physicist at the Ioffe Physico-Technical Institute in Leningrad, proposed a hypothesis that very large stars would collapse into what might now be called generic objects for Dark Energy (GEODEs) that appear be black holes when viewed from the outside, but unlike black holes, they contain dark energy instead of a singularity.
Fast forward to new research at the University of Hawaii at Manoa: physicists usually assume that a cosmologically large system, like the universe, is insensitive to details of the small systems contained therein. Astrophysicist Kevin Croker and mathematician Joel Weiner have identified and corrected a subtle error made by applying Einstein's equations to model the growth of the universe showing that this assumption can fail for the compact objects that remain after the collapse and explosion of very large stars.
"For 80 years, we have generally worked under the assumption that the universe, in broad terms, was not affected by the specific details of any small region," Croker said. "It is now clear that general relativity can be observed collapsing stars ̵
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Croker and Weiner showed that the growth rate of the universe can be sensitive to the average contribution of such compact objects. In the same way, the objects themselves can be linked to the growth of the universe, gain or lose energy depending on the compositions of the objects. This result is significant because it reveals unexpected connections between cosmological and compact object physics, which in turn leads to many new observation predictions.
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Objects like Powehi, the recently depicted super-massive compact object in the center of the galaxy M87 (pictured at the top of the page), may actually be GEODEs. Powehi GEODE, shown to scale, would be about 2/3 of the radius of the dark region depicted by the Event Horizon Telescope. This is almost the same size as expected for a black hole. The region containing Dark Energy (green) is slightly larger than a black hole with the same mass. The properties of any crust (purple) depend on the GEODE model. (EHT collaboration; NASA / CXC / Villanova University)
One consequence of this study is that the universe's growth rate provides information on what happens to stars at the end of their lives. Astronomers usually assume that large stars form black holes when they die, but this is not the only possible outcome.
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In 1998, two independent teams of astronomers discovered that the universe's expansion was faster, consistent with the existence of a uniform contribution from Dark Energy. However, it was not acknowledged that GEODEs could contribute in this way. With the corrected formalism, Croker and Weiner showed that if a fraction of the oldest stars collapsed in GEODE, instead of black holes, their average contribution today would naturally produce the necessary uniform Dark Energy.
The results of this study also apply to the colliding double star systems that can be observed by gravitational waves through the LIGO-Virgo collaboration. In 2016, LIGO announced the first observation of what appeared to be a colliding double-black hole system. Such systems were expected to exist, but the object was unexpectedly heavy – about 5 times larger than the black hole masses predicted in computer simulations.
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Using the corrected formalism, Croker and Weiner considered whether LIGO-Virgo observes dual GEODE collisions, instead of double black hole collisions. They found that GEODE grows together with the universe in the meantime until such collisions. When the collisions occur, the resulting GEODE masses become 4 to 8 times larger, roughly in line with the LIGO-Virgo observations.
Croker and Weiner were careful to separate their theoretical results from observational support for a GEODE scenario, emphasizing that "black holes are really not dead. What we have shown is that if GEODE exists, they can easily give rise to observed phenomena We currently anticipate many other observational consequences of a GEODE scenario, including many ways to exclude. We have barely begun to scratch the surface. "
Daily Galaxy via University of Hawaii at Manoa