Visible Shapes of Black Holes M87* and SgrA*

We review the physical origins for possible visible images of the supermassive black hole M87* in the galaxy M87 and SgrA* in the Milky Way Galaxy. The classical dark black hole shadow of the maximal size is visible in the case of luminous background behind the black hole at the distance exceeding the so-called photon spheres. The notably smaller dark shadow (dark silhouette) of the black hole event horizon is visible if the black hole is highlighted by the inner parts of the luminous accreting matter inside the photon spheres. The first image of the supermassive black hole M87*, obtained by the Event Horizon Telescope collaboration, shows the lensed dark image of the southern hemisphere of the black hole event horizon globe, highlighted by accreting matter, while the classical black hole shadow is invisible at all. A size of the dark spot on the Event Horizon Telescope (EHT) image agrees with a corresponding size of the dark event horizon silhouette in a thin accretion disk model in the case of either the high or moderate value of the black hole spin, a≳0.75.

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

Universe ◽

10.3390/universe5080183 ◽

2019 ◽

Vol 5 (8) ◽

pp. 183 ◽

Cited By ~ 8

Author(s):

Vyacheslav I. Dokuchaev ◽

Natalia O. Nazarova

Keyword(s):

Black Hole ◽

Event Horizon ◽

Accretion Disk ◽

Disk Model ◽

Dark Region ◽

High Resolution Image ◽

Supermassive Black Hole ◽

Black Hole Spin ◽

The Galaxy ◽

Expected Position

We propose the simple new method for extracting the value of the black hole spin from the direct high-resolution image of black hole by using a thin accretion disk model. In this model, the observed dark region on the first image of the supermassive black hole in the galaxy M87, obtained by the Event Horizon Telescope, is a silhouette of the black hole event horizon. The outline of this silhouette is the equator of the event horizon sphere. The dark silhouette of the black hole event horizon is placed within the expected position of the black hole shadow, which is not revealed on the first image. We calculated numerically the relation between the observed position of the black hole silhouette and the brightest point in the thin accretion disk, depending on the black hole spin. From this relation, we derive the spin of the supermassive black hole M87*, a = 0.75 ± 0.15 .

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Universal interferometric signatures of a black hole’s photon ring

Science Advances ◽

10.1126/sciadv.aaz1310 ◽

2020 ◽

Vol 6 (12) ◽

pp. eaaz1310 ◽

Cited By ~ 16

Author(s):

Michael D. Johnson ◽

Alexandru Lupsasca ◽

Andrew Strominger ◽

George N. Wong ◽

Shahar Hadar ◽

...

Keyword(s):

General Relativity ◽

Black Hole ◽

Event Horizon ◽

Infinite Sequence ◽

High Order ◽

Black Hole Mass ◽

Tests Of General Relativity ◽

Supermassive Black Hole ◽

The Galaxy ◽

Self Similar

The Event Horizon Telescope image of the supermassive black hole in the galaxy M87 is dominated by a bright, unresolved ring. General relativity predicts that embedded within this image lies a thin “photon ring,” which is composed of an infinite sequence of self-similar subrings that are indexed by the number of photon orbits around the black hole. The subrings approach the edge of the black hole “shadow,” becoming exponentially narrower but weaker with increasing orbit number, with seemingly negligible contributions from high-order subrings. Here, we show that these subrings produce strong and universal signatures on long interferometric baselines. These signatures offer the possibility of precise measurements of black hole mass and spin, as well as tests of general relativity, using only a sparse interferometric array.

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10.2. High proper motions in the vicinity of Sgr A∗: unambiguous evidence for a massive central black hole

Symposium - International Astronomical Union ◽

10.1017/s0074180900085478 ◽

1998 ◽

Vol 184 ◽

pp. 433-434

Author(s):

A. M. Ghez ◽

B. L. Klein ◽

C. McCabe ◽

M. Morris ◽

E. E. Becklin

Keyword(s):

Black Hole ◽

Milky Way ◽

Galactic Center ◽

Robust Method ◽

Proper Motions ◽

Central Black Hole ◽

Milky Way Galaxy ◽

The Galaxy ◽

Sgr A

Although the notion that the Milky Way galaxy contains a supermassive central black hole has been around for more than two decades, it has been difficult to prove that one exists. The challenge is to assess the distribution of matter in the few central parsecs of the Galaxy. Assuming that gravity is the dominant force, the motion of the stars and gas in the vicinity of the putative black hole offers a robust method for accomplishing this task, by revealing the mass interior to the radius of the objects studied. Thus objects located closest to the Galactic Center provide the strongest constraints on the black hole hypothesis.

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M87 Supermassive Black Hole Review

10.20944/preprints202105.0487.v1 ◽

2021 ◽

Author(s):

Mekhala Ganguly

Keyword(s):

Black Hole ◽

Event Horizon ◽

Gravitational Lensing ◽

Elliptical Galaxy ◽

Virgo Cluster ◽

Supermassive Black Hole ◽

Cluster Of Galaxies ◽

Hot Plasma ◽

The Galaxy ◽

Relativistic Particles

M87 is a giant elliptical galaxy in the Virgo cluster of galaxies. The radio source has a core which coincides with the nucleus of the galaxy and a jet of emission which is detected from radio to X-ray bands. A supermassive black hole is assumed to be at the centre of M87 which sends out relativistic particles in the form jets along its axis of rotation. Relativistic particles accelerated in a magnetic field, give out synchrotron radiation. The centre is surrounded by an accretion disc, which is the closest that we can probe into a black hole. High resolution observations are needed to examine the nature of the radio emission closest to the centre of M87. An array of millimetre-band telescopes across the globe were used as an interferometer, called the Event Horizon Telescope, (EHT) to probe the nuclear region. The angular resolution of this interferometer array is 25 microarc sec, at a wavelength of 1.3mm and the data was carefully calibrated and imaged. The resulting image shows an asymmetric ring which is consistent with the predictions of strong gravitational lensing of synchrotron emission from hot plasma near the event horizon. In this paper, we review the results of the observations of the radio galaxy, M87, using the Event Horizon Telescope

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Effects of non-vanishing dark matter pressure in the Milky Way Galaxy

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab2571 ◽

2021 ◽

Vol 508 (1) ◽

pp. 1543-1554

Author(s):

K Boshkayev ◽

T Konysbayev ◽

E Kurmanov ◽

O Luongo ◽

D Malafarina ◽

...

Keyword(s):

Black Hole ◽

Dark Matter ◽

Gravitational Lensing ◽

Matter Content ◽

Dark Matter Halo ◽

Matter Distribution ◽

Milky Way Galaxy ◽

The Galaxy ◽

Dark Matter Distribution ◽

Inner Parts

ABSTRACT We consider the possibility that the Milky Way’s dark matter halo possesses a non-vanishing equation of state. Consequently, we evaluate the contribution due to the speed of sound, assuming that the dark matter content of the galaxy behaves like a fluid with pressure. In particular, we model the dark matter distribution via an exponential sphere profile in the galactic core, and inner parts of the galaxy whereas we compare the exponential sphere with three widely used profiles for the halo, i.e. the Einasto, Burkert and Isothermal profile. For the galactic core, we also compare the effects due to a dark matter distribution without black hole with the case of a supermassive black hole in vacuum and show that present observations are unable to distinguish them. Finally we investigate the expected experimental signature provided by gravitational lensing due to the presence of dark matter in the core.

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A Star Is Born

From Dust to Life ◽

10.23943/princeton/9780691175706.003.0007 ◽

2017 ◽

Author(s):

John Chambers ◽

Jacqueline Mitton

Keyword(s):

Milky Way ◽

Rotating Disk ◽

Stellar Disk ◽

Mass Star ◽

Fine Dust ◽

Solar Mass ◽

Milky Way Galaxy ◽

Supermassive Black Hole ◽

The Galaxy ◽

Main Component

This chapter focuses on the nature and composition of the Milky Way galaxy. The main component of the Milky Way is a rotating disk of stars some 100,000 light-years across but only about 1,000 light-years thick. Between the stars lies an extremely tenuous mixture of gas and fine dust grains called the interstellar medium. The disk of stars is only about 1,000 light-years thick but becomes thicker near the Milky Way's center, where a bar-shaped bulge of densely packed stars surrounds a supermassive black hole at the heart of the galaxy. Enveloping the thin stellar disk is an extended disk of gas about 10 times thicker. Today, stars are forming in the Milky Way at a rate equivalent to one solar-mass star every year. Judging by the age of its oldest members, the Milky Way has been giving birth to new stars for over 13 billion years.

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The Long View of Planetary Systems

10.1093/oso/9780198799894.003.0011 ◽

2018 ◽

Author(s):

Karel Schrijver

Keyword(s):

Solar System ◽

Milky Way ◽

Planetary Systems ◽

Giant Planets ◽

Milky Way Galaxy ◽

Population Statistics ◽

The Past ◽

General Terms ◽

The Galaxy ◽

The Universe

How many planetary systems formed before our’s did, and how many will form after? How old is the average exoplanet in the Galaxy? When did the earliest planets start forming? How different are the ages of terrestrial and giant planets? And, ultimately, what will the fate be of our Solar System, of the Milky Way Galaxy, and of the Universe around us? We cannot know the fate of individual exoplanets with great certainty, but based on population statistics this chapter sketches the past, present, and future of exoworlds and of our Earth in general terms.

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A Statistical Estimation of the Occurrence of Extraterrestrial Intelligence in the Milky Way Galaxy

Galaxies ◽

10.3390/galaxies9010005 ◽

2021 ◽

Vol 9 (1) ◽

pp. 5

Author(s):

Xiang Cai ◽

Jonathan H. Jiang ◽

Kristen A. Fahy ◽

Yuk L. Yung

Keyword(s):

Statistical Estimation ◽

Milky Way ◽

Galactic Center ◽

Model Simulation ◽

Temporal Variations ◽

Extraterrestrial Intelligence ◽

Milky Way Galaxy ◽

The Galaxy ◽

Peak Location ◽

Intelligent Life

In the field of astrobiology, the precise location, prevalence, and age of potential extraterrestrial intelligence (ETI) have not been explicitly explored. Here, we address these inquiries using an empirical galactic simulation model to analyze the spatial–temporal variations and the prevalence of potential ETI within the Galaxy. This model estimates the occurrence of ETI, providing guidance on where to look for intelligent life in the Search for ETI (SETI) with a set of criteria, including well-established astrophysical properties of the Milky Way. Further, typically overlooked factors such as the process of abiogenesis, different evolutionary timescales, and potential self-annihilation are incorporated to explore the growth propensity of ETI. We examine three major parameters: (1) the likelihood rate of abiogenesis (λA); (2) evolutionary timescales (Tevo); and (3) probability of self-annihilation of complex life (Pann). We found Pann to be the most influential parameter determining the quantity and age of galactic intelligent life. Our model simulation also identified a peak location for ETI at an annular region approximately 4 kpc from the galactic center around 8 billion years (Gyrs), with complex life decreasing temporally and spatially from the peak point, asserting a high likelihood of intelligent life in the galactic inner disk. The simulated age distributions also suggest that most of the intelligent life in our galaxy are young, thus making observation or detection difficult.

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