Viewing the shadow of the black hole at the Galactic center

Heino Falcke, Fulvio Melia, Eric Agol

Research output: Contribution to journalArticle

402 Citations (Scopus)

Abstract

In recent years, evidence for the existence of an ultracompact concentration of dark mass associated with the radio source Sagittarius A* in the Galactic center has become very strong. However, unambiguous proof that this object is indeed a black hole is still lacking. A defining characteristic of a black hole is the event horizon. To a distant observer, the event horizon casts a relatively large "shadow" with an apparent diameter of ∼10 gravitational radii that is due to the bending of light by the black hole, and this shadow is nearly independent of the black hole spin or orientation. The predicted size (∼30 μas) of this shadow for Sgr A* approaches the resolution of current radio interferometers. If the black hole is maximally spinning and viewed edge-on, then the shadow will be offset by ∼8 μas from the center of mass and will be slightly flattened on one side. Taking into account the scatter broadening of the image in the interstellar medium and the finite achievable telescope resolution, we show that the shadow of Sgr A* may be observable with very long baseline interferometry at submillimeter wavelengths, assuming that the accretion flow is optically thin in this region of the spectrum. Hence, there exists a realistic expectation of imaging the event horizon of a black hole within the next few years.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume528
Issue number1 PART 2
StatePublished - Jan 1 2000

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radio
event horizon
very long baseline interferometry
interferometer
accretion
wavelength
radio interferometers
metal spinning
center of mass
casts
interferometry
telescopes
radii
wavelengths

Keywords

  • Black hole physics
  • Galaxies: active
  • Galaxy: center
  • Relativity
  • Submillimeter
  • Techniques: interferometric

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Viewing the shadow of the black hole at the Galactic center. / Falcke, Heino; Melia, Fulvio; Agol, Eric.

In: Astrophysical Journal, Vol. 528, No. 1 PART 2, 01.01.2000.

Research output: Contribution to journalArticle

Falcke, Heino ; Melia, Fulvio ; Agol, Eric. / Viewing the shadow of the black hole at the Galactic center. In: Astrophysical Journal. 2000 ; Vol. 528, No. 1 PART 2.
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