Farook Rahaman and colleagues investigated the shadow cast by a certain class of rotating traversable wormhole i.e. Lorentzian. They showed that the throat of a wormhole plays very crucial role in shadow formation. They found that the shadow of wormhole is slanted as well as can be altered depending on the different parameters present in the wormhole spacetime. Their study recently appeared in Classical and Quantum Gravity.
Wormholes are topologically non-trivial structures of the spacetime connecting our Universe with other universes. Their nature plays a crucial role on shadow effect, which actually arises during the strong gravitational lensing. Current observations have inspired scientists to construct the shadow of wormholes, as well as, analyse the shape of the shadows.
Now, Farook Rahaman and colleagues explored the shadow cast by a certain class of rotating wormhole. To search this, they first composed the null geodesics and studied the effects of the parameters on the photon orbit.
They have found that, for small spin and smaller wormhole throat size, the shadow of a wormhole mimics those of the black hole.
However, with increasing either the spin or the throat size, the shadow of a wormhole start deviating from that of a black hole. Detection of such deviation may possibly indicate the presence of a wormhole.
They also constrained the size and the spin of the wormhole using the results from M87* observation, by investigating the average diameter of the wormhole as well as deviation from circularity with respect to the wormhole throat size. Their results indicated that a wormhole having reasonable spin or throat size, can be distinguished from a black hole through observations of their shadow.
“In a future observation, this type of study may help to indicate the presence of a wormhole in a galactic region.”, they concluded.
Reference: Farook Rahaman, Ksh. Newton Singh, Rajibul Shaikh, Tuhina Manna and Somi Aktar, “Shadows of Lorentzian traversable wormholes”, Classical and Quantum Gravity, 2021. https://iopscience.iop.org/article/10.1088/1361-6382/ac213b
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