Can Wormholes and Black Holes be Distinguished by Magnification? (Cosmology)

The enigmatic universe has long captivated the imagination of scientists and stargazers alike. Among its many profound phenomena, wormholes and black holes stand as cosmic mysteries that continue to beckon exploration. Recent research conducted by Ke Gao and Lei-Hua Liu delves deep into the intricate world of these celestial wonders, focusing on the rotational Simpson-Visser metric (RSV) as the key to unraveling their magnification effects.

The allure of wormholes and black holes lies not only in their perplexing existence but also in their ability to magnify the cosmos. Understanding the finite distance analysis of this magnification phenomenon has been the pursuit of many astronomers and physicists, and Gao and Liu’s work takes a significant step towards clarity.

By meticulously calculating the deflection of light within the RSV metric, the researchers were able to unveil the mesmerizing magnification effect. This groundbreaking approach enabled them to apply the RSV metric to specific examples, including the Ellis-Bronnikov wormhole, Schwarzschild black hole, and Kerr black hole (or wormhole), shedding light on their unique magnification characteristics.

The results of their study are as intriguing as the objects of their investigation. Notably, the Ellis-Bronnikov wormhole exhibited singular magnification peaks, a distinctive trait that sets it apart from its black hole counterparts. In contrast, Schwarzschild’s black hole, as the ADM mass increases, unfolds the astonishing spectacle of up to three peaks of magnification.

The story doesn’t end there; black holes with negative spin, known as Kerr Black holes, introduce a fascinating twist. As spin increases, these enigmatic entities transition from three magnification peaks to a solitary peak, a phenomenon that is mirrored in the case of positive spin. These findings open new vistas in our comprehension of black hole behavior.

Perhaps the most tantalizing revelation is the application of this research to the Central Black Hole of the Milky Way Galaxy. Here, the lensing effect showcases multiple peaks of magnification, offering a tantalizing glimpse into the cosmic wonders that lie at the heart of our galaxy. Regrettably, these captivating effects remain beyond the purview of observation from Earth, a testament to the vastness of the cosmos.

In essence, Gao and Liu’s research provides not only a discernible phenomenological difference in magnification between black holes and wormholes but also lays down a firm theoretical foundation for future explorations into the intricacies of these celestial enigmas. As humanity continues to gaze towards the heavens, such revelations bring us ever closer to unlocking the profound secrets of the universe, one cosmic puzzle at a time.

Reference: Ke Gao, Lei-Hua Liu, “Can wormholes and black holes be distinguished by magnification?”, Arxiv, 2023. https://arxiv.org/abs/2307.16627

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How Microlensing by Black Holes Can Influence The Characteristics of the Shadow? (Cosmology)

Gravitational microlensing is a phenomenon that occurs when the light from a distant source is bent and magnified by the gravitational field of an intervening object. In the context of black hole shadows imaged by the Event Horizon Telescope (EHT), a recent analysis by Himanshu and Silk presents a detailed exploration of how microlensing by intervening compact objects can influence the center, size, and shape of the shadow. This article summarizes their findings, highlighting the dependence of the shadow on the Einstein angle and the implications for future observations.

Microlensing and Black Hole Shadows:

The concept of a black hole shadow refers to the dark region in the immediate vicinity of a black hole caused by its intense gravitational pull, as predicted by Einstein’s theory of general relativity. Himanshu and Silk demonstrate that microlensing effects can introduce significant modifications to the black hole shadow, resulting in observable changes in its characteristics.

Dependence on Einstein Angle:

The size of the shadow is found to be dependent on the Einstein angle, which is a measure of the angular scale associated with gravitational lensing. The authors show that the center, size, and shape of the shadow are influenced by the relative size of the Einstein angle to the true/unlensed shadow size. This dependency provides a valuable insight into the behavior of black hole shadows under the influence of microlensing.

Effects of Lens Location:

The location of the intervening lens plays a crucial role in the shift, size, and asymmetry of the black hole shadow due to microlensing. Himanshu and Silk’s analysis reveals that microlensing can create an asymmetry of up to approximately 8%, which is twice the asymmetry caused by the spin and tilt of the supermassive black hole (SMBH) relative to the observer. Additionally, the size of the shadow can be enhanced by approximately 50% compared to its true size.

Limitations and Future Prospects:

Presently, the terrestrial baselines of the EHT lack the resolution required to detect microlensing signatures in black hole shadows. However, the authors suggest that future expansions of the EHT, including space-based baselines at the Moon and L2, hold the potential to enable the detection of microlensing events. These advancements could open up new avenues for studying the dynamics of black holes and their surrounding environments.

Observing Microlensing Events:

While the event rate of microlensing phenomena near the supermassive black hole Sgr~A∗ is currently low (0.0014 per year), making them difficult to observe even with space-based baselines, continuous monitoring of the shadow of Sgr~A∗ could provide valuable insights into the compact object population surrounding the galactic center. By tracking potential microlensing events, researchers may gain a deeper understanding of the distribution and properties of these compact objects.

Conclusion:

In conclusion, the work by Himanshu and Silk offers a comprehensive analysis of gravitational microlensing effects on black hole shadows imaged by the EHT. The study highlights the dependence of the shadow’s center, size, and shape on the Einstein angle and demonstrates the significant impact of intervening compact objects on the asymmetry and size of the shadow. Although current observational capabilities limit the detection of microlensing signatures, future expansions of the EHT, including space-based baselines, could unlock the potential to observe these events and provide further insights into the nature of black holes and their surroundings.

Reference: Himanshu Verma, Joseph Silk, “Microlensing Black Hole Shadows”, Arxiv, 2023. https://arxiv.org/abs/2306.02440

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