Measurement of the spin of the M87 black hole from its observed twisted light

Abstract

We present the first observational evidence that light propagating near a rotating black hole is twisted in phase and carries orbital angular momentum (OAM). This physical observable allows a direct measurement of the rotation of the black hole. We extracted the OAM spectra from the radio intensity data collected by the Event Horizon Telescope from around the black hole M87* by using wavefront reconstruction and phase recovery techniques and from the visibility amplitude and phase maps. This method is robust and complementary to black-hole shadow circularity analyses. It shows that the M87* rotates clockwise with an estimated rotation parameter a = 0.90 ± 0.05 with ∼ 95% confidence level (c.l.) and inclination i = 17 • ± 2 • , equivalent to a magnetic arrested disk with inclination i = 163 • ± 2 • . From our analysis we conclude, within a 6 σ c.l., that the M87* is rotating.

The Brightest Point in Accretion Disk and Black Hole Spin: Implication to the Image of Black Hole M87*

“…The 1σ error in this fit corresponds to the observed width of the asymmetric bright ring on the M87* image[1][2][3][4][5][6]. The derived value of the M87* spin is in a general agreement with the other similar estimations[44][45][46][47][48][49][50][51][52]. See inFigure 6the superposition of the M87* image and the modelled image of the thin accretion disk in the case of a = 0.75.FIG.…”

Testing the rotational nature of the supermassive object M87* from the circularity and size of its first image

“…When making the additional assumption that the jet is powered by the spin and it is aligned with the spin axis (for instance through the Blandford-Znajek mechanism [55]), the measurement of the direction of the jet leads to θ obs = 17 has been used in conjunction with simulations of the twist of the light emitted and propagated from the Einstein ring surrounding the shadow of M87* to estimate a * 0.9 ± 0.1 for a Kerr BH [58]. In our work, we have not included any other observation besides the deviation from circularity of the Kerr BH, so that the constraints in Fig.…”

The local intrinsic curvature of wavefronts allows to detect optical vortices

“…Because the distance D(s) is a linear application we obtain the projection as φ P (q) = φ (s)α 2 (7) and hence…”

“…It differs from "ordinary" light since the quantized orbital angular momentum L z = l per photon, where l is an integer. This introduces an additional degree of freedom that opens new perspectives in different fields of applied and fundamental science such as singular and quantum optics [2,3], astronomy and astrophysics [4][5][6][7], quantum information and computing [8,9] as well as telecommunications [10][11][12].…”