Shadows of Lorentzian traversable wormholes

Abstract

The prospect of identifying wormholes by investigating the shadows of wormholes constitute a foremost source of insight into the evolution of compact objects and it is one of the essential problems in contemporary astrophysics. The nature of the compact objects (wormholes) plays a crucial role on shadow effect, which actually arises during the strong gravitational lensing. Current Event Horizon Telescope observations have inspired scientists to study and to construct the shadow images of the wormholes. In this work, we explore the shadow cast by a certain class of rotating wormhole. To search this, we first compose the null geodesics and study the effects of the parameters on the photon orbit. We have exposed the form and size of the wormhole shadow and have found that it is slanted as well as can be altered depending on the different parameters present in the wormhole spacetime. We also constrain the size and the spin of the wormhole using the results from M87* observation, by investigating the average diameter of the wormhole shadow as well as its deviation from circularity with respect to the wormhole throat size. In a future observation, this type of study may help to indicate the presence of a wormhole in a galactic region.

Shadow images of compact objects in beyond Horndeski theory

“…On the other hand, theoretical investigations of shadow images of compact objects are quite fascinating. This applies not only to black holes in General Relativity [36][37][38][39][40][41][42][43][44][45] and in alternative gravities [46][47][48][49][50][51][52][53][54][55][56], but also to exotic compact objects like wormholes [57][58][59][60][61][62][63][64][65][66][67], naked singlarities [68][69][70][71][72][73][74][75][76][77][78] or boson stars [79,80]. Previous studies have shown that some of these exotic compact objects can mimic black holes with respect to their shadow images if their light ring properties are similar.…”

Generalised Ellis-Bronnikov Wormholes in $f(R)$ Gravity

“…Karakasis et al discussed the wormhole geometries by introducing a phantom scalar field in the gravitational action of f (R) gravity; as a result, it becomes ghost-free and avoids the tachyonic instability [66]. Farook et al studied shadows of a particular class of rotating wormhole, and they compose the null geodesics and study the effects of the parameters on the photon orbit [67]. Kuhfitting addressed two fundamental issues concerning Morris-Throne wormholes in the five-dimensional spacetime, such as the origin of exotic matter and frequently inexplicable enormous radial tension at the throat [68].…”

Testing black hole mimickers with the Event Horizon Telescope image of Sagittarius A$^*$

“…This could help us constraining the parameter of these spacetimes (see e.g. [2,14,[23][24][25][26][27][28][29][30][31][32][33]). In this regard, while the notion of black hole event horizons continues to attract much of the attention, horizonless compact objects which mimic black holes are also fast gaining popularity in the literature (see [34] and references therein).…”