Insight |

Black Holes

Black holes were theoretically established in 1915, shortly after Albert Einstein published his theory of General Relativity. Since then, observations have confirmed black holes as actual astrophysical objects. In this Insight we publish ten long- and short-format pieces (in the “Reviews & Perspectives” and “Views & Comments” tabs, respectively) discussing key aspects of black holes, from their masses, to their spins, to the ways in which they impact their surroundings and are studied. This collection also showcases some of the black hole-related content that Nature Astronomy has published since our launch (in the “Primary research” and “Further reading” tabs). Also, please view our previous collection of landmark black hole discoveries published in Nature and other Springer Nature journals.

Reviews & Perspectives

Current black hole spin measurements, in X-rays, radio and gravitational waves, are already constraining models for the growth of black holes, the dynamics of stellar core-collapse and the physics of relativistic jet production.

Review Article | | Nature Astronomy

Examining and comparing many of the definitions of a black hole, it is concluded that the profusion of different definitions is a virtue that makes the investigation of black holes possible and fruitful in many different kinds of problems.

Perspective | | Nature Astronomy

Views & Comment

Black holes have the distinct honour of being the most popular and potentially the least well-understood objects in the Universe. This issue’s Insight explores how far black hole research has come since its inception, though it still has a long way to go.

Editorial | | Nature Astronomy

Mitchell C. Begelman, Professor in the Department of Astrophysical and Planetary Sciences at the University of Colorado Boulder and a black hole expert, discusses the start of the field with Nature Astronomy.

Q&A | | Nature Astronomy

The masses of supermassive black holes, key to many cosmological studies, are highly uncertain beyond our local Universe. The main challenge is to establish the spatial and kinematic structure of the broad-line emitting gas in active galactic nuclei.

Comment | | Nature Astronomy

Primary Research

A magnetohydrodynamic model for outflows around supermassive black holes can also reproduce the X-ray properties of an outflow around a stellar black hole. This indicates that magnetic forces have a universal role to play in driving these winds.

Letter | | Nature Astronomy

Further Reading

Arguably, no mission changed X-ray astronomy in as short a time as did Hitomi. The planned X-ray Astronomy Recovery Mission, XARM, will carry its legacy forward.

Comment | | Nature Astronomy

The material surrounding accreting supermassive black holes connects them with their hosts. From studies in the infrared and X-rays, the structure of this material is found to be complex, clumpy and dynamic.

Review Article | | Nature Astronomy

Radiative efficiency in radio-loud active galactic nuclei is governed by the accretion rate onto the central black hole rather than directly by the type of accreted matter; while it correlates with real differences in host galaxies and environments, it does not provide unambiguous information about particular objects.

Comment | | Nature Astronomy

Galaxy-scale outflows powered by actively accreting supermassive black holes are routinely detected, and they have been associated with both the suppression and triggering of star formation. Recent observational evidence and simulations are favouring a delayed mechanism that connects outflows and star formation.

Comment | | Nature Astronomy

Active galactic nuclei (AGNs) are empirically divided into ‘radio-loud’ and ‘radio-quiet’. These 50-year-old labels are obsolete, misleading and wrong. I argue that AGNs should be classified as ‘jetted’ and ‘non-jetted’ based on a physical difference — the presence (or lack) of strong relativistic jets.

Comment | | Nature Astronomy

Millimetre-wavelength interferometry and gravitational-wave detectors currently provide the most stringent tests for the existence of cosmic black holes. Complementary measurements of magnetic fields near their event horizon would be decisive.

Comment | | Nature Astronomy

Black holes present a profound challenge to our current foundations of physics, and an exciting era of astronomy is just opening in which gravitational-wave observation and very-long-baseline interferometry may provide important hints about the new principles of physics needed.

Comment | | Nature Astronomy

Feedback from active galactic nuclei (AGNs) remains controversial despite its wide acceptance as necessary to regulate massive galaxy growth. Consequently, we held a workshop in October 2017, at Leiden’s Lorentz Center, to distinguish between the reality and myths of feedback.

Meeting Report | | Nature Astronomy

The Event Horizon Telescope, an Earth-sized interferometer, aims to capture an image of a black hole’s event horizon to test the theory of general relativity and probe accretion processes, explains project director Shep Doeleman.

Mission Control | | Nature Astronomy

Recent polarization measurements of the stellar-mass black hole in Cygnus X-1 reveal an extended corona in the inner parts of the accretion flow and open the path for a new era in high-energy astrophysics.

News & Views | | Nature Astronomy

Supermassive binary black holes are thought to lie at the centres of merging galaxies. The blazar OJ 287 is the poster child of such systems, showing strong and periodic variability across the electromagnetic spectrum. A new study questions the physical origin of this variability.

News & Views | | Nature Astronomy

A study suggests that the gas clouds in the vicinity of rapidly accreting supermassive black holes are distributed in a planar distribution, impacting the estimation of the mass of the black hole based on the motion of these clouds.

News & Views | | Nature Astronomy

Orbiting supermassive black holes in the centres of nearby galaxies contribute to a gravitational-wave background over the whole sky. Networks of millisecond pulsars are sensitive to this signal. Creating maps of this background using information from known galaxies can help us to project when (and how) we may observe it.

News & Views | | Nature Astronomy

The first detection of electromagnetic emission from a gravitational wave source bridges the gap between one of the most energetic phenomena in the Universe and their dark, difficult to detect progenitors.

News & Views | | Nature Astronomy

The biggest black holes in the Universe were in place soon after the Big Bang. Explaining how they formed so rapidly is a daunting challenge, but the latest simulations give clues to how this may have occurred.

News & Views | | Nature Astronomy

Black holes grow by accreting mass, but the process is messy and redistributes gas and energy into their environments. New evidence shows that magnetic processes mediate both the accretion and ejection of matter.

News & Views | | Nature Astronomy