Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Can we tell black holes apart?

17.04.2018

Astrophysicists at Frankfurt, the Max Planck Institute for Radio Astronomy in Bonn, and Nijmegen, collaborating in the project BlackHoleCam, answer this question by computing the first images of feeding non-Einsteinian black holes: it is presently hard to tell them apart from standard black holes.

One of the most fundamental predictions of Einstein's theory of relativity is the existence of black holes. In spite of the recent detection of gravitational waves from binary black holes by LIGO, direct evidence using electromagnetic waves remains elusive and astronomers are looking for it with radio telescopes.


Synthetic shadow images of Sgr A* for a Kerr black hole (top row) and a non-rotating dilaton black hole (bottom row).

Fromm/Younsi/Mizuno/Rezzolla (Frankfurt)

For the first time, collaborators in the ERC funded project BlackHoleCam, including astrophysicists at Goethe University Frankfurt, Max Planck Institute for Radio Astronomy (MPIfR) Bonn, and Radboud University Nijmegen, have compared self-consistent and realistic images of the shadow of an accreting supermassive black hole – such as the black-hole candidate Sagittarius A* (Sgr A*) in the heart of our Galaxy – both in general relativity and in a different theory of gravity. The goal was to test if Einsteinian black holes can be distinguished from those in alternative theories of gravity.

Not all of the light rays (or photons) produced by matter falling onto a black hole are trapped by the event horizon, a region of spacetime from which nothing can escape. Some of these photons will reach distant observers, so that when a black hole is observed directly, a “shadow” is expected against the background sky. The size and shape of this shadow will depend on the black hole’s properties and on the theory of gravity.

Because the largest deviations from Einstein’s theory of relativity are expected very close to the event horizon, and since alternative theories of gravity make different predictions on the properties of shadow, direct observations of Sgr A* represent a very promising approach for testing gravity in the strongest regime. Making such images of the black-hole shadow is the prime goal of the international Event Horizon Telescope Collaboration (EHTC), which combines radio data from telescopes around the world.

Scientists from the BlackHoleCam Team in Europe, who are part of the EHTC, have now have gone a step further and investigated whether it is possible to distinguish between a "Kerr" black hole from Einstein’s gravity and a "dilaton" black hole, which is a possible solution of an alternative theory of gravity.

The researchers studied the evolution of matter falling into the two very different types of black holes and calculated the radiation emitted to construct the images. Furthermore, real-life physical conditions in the telescopes and interstellar medium were used to create physically realistic images. “To capture the effects of different black holes we used realistic simulations of accretion disks with near-identical initial setups. These expensive numerical simulations used state-of-the-art codes and several months on the Institute’s supercomputer LOEWE”, says Dr. Mizuno, lead author of the study.

Moreover, expected radio images obviously have a limited resolution and image fidelity. When using realistic image resolutions, the scientists found, to their surprise, that even highly non-Einsteinian black holes could disguise themselves as normal black holes.

“Our results show that there are theories of gravity in which black holes can masquerade as Einsteinian, so new techniques of analyzing EHT data may be needed to tell them apart”, remarks Luciano Rezzolla, professor at Goethe University and leader of the Frankfurt team. “While we believe general relativity is correct, as scientists we need to be open-minded. Luckily, future observations and more advanced techniques will eventually settle these doubts”, concludes Rezzolla.

“Indeed, independent information from an orbiting pulsar, which we are actively searching for, will help eliminate these ambiguities”, says Michael Kramer, director at the MPI for Radio Astronomy in Bonn. Heino Falcke (professor at Radboud University), who 20 years ago proposed using radio telescopes to image the shadow of black holes, is optimistic. “There is little doubt that the EHT will eventually obtain strong evidence of a black hole shadow. These results encourage us to refine our techniques beyond the current state of the art and thus make even sharper images in the future."

BlackHoleCam is an ERC-funded Synergy project to finally image, measure and understand astrophysical black holes. Its PIs, Falcke, Kramer and Rezzolla, test fundamental predictions of Einstein’s theory of General Relativity. The BlackHoleCam team members are active partners of the global Event Horizon Telescope Consortium (ETHC). Goethe University is a stakeholder institute and represented on the Executive board of the EHTC.

List of Authors and affiliations:

Yosuke Mizuno1, Ziri Younsi1, Christian M. Fromm1, , Oliver Porth1, Mariafelicia De Laurentis1, Hector Olivares1, Heino Falcke2, Michael Kramer3 and Luciano Rezzolla1,4

(1) Institute for Theoretical Physics, Goethe University, Frankfurt, Germany; (2) Radboud University, Nijmegen, The Netherlands; (3) Max Planck Institute for Radioastronomy, Bonn, Germany; (4) Institute for Advanced Studies, Frankfurt, Germany

Scientists Contact phone numbers:

Yosuke Mizuno: Mobile: +49 159 02104299, Office: +49 69 79847885
Heino Falcke: Mobile: +49 151 23040365, Office: +31 24 3652020
Michael Kramer: Mobile: +49 160 90747348, Office: +49 228 525278
Luciano Rezzolla: Mobile: +49 170 3022982, Office: +49 69 79847871


Local Contact:

Prof. Dr. Michael Kramer,
Director and Head of Research Department „Fundamental Physics in Radio Astronomy“
Max-Planck-Institut für Radioastronomie, Bonn.
Fon: +49 228 525-278
E-mail: mkramer@mpifr-bonn.mpg.de

Prof. Dr. Eduardo Ros,
Max-Planck-Institut für Radioastronomie, Bonn.
Fon: +49 228 525-125
E-mail: ros@mpifr-bonn.mpg.de

Dr. Norbert Junkes,
Press and Public Outreach
Max-Planck-Institut für Radioastronomie, Bonn.
Fon: +49 228 525-399
E-mail: njunkes@mpifr-bonn.mpg.de

Weitere Informationen:

https://www.mpifr-bonn.mpg.de/pressreleases/2018/5

Norbert Junkes | Max-Planck-Institut für Radioastronomie

More articles from Physics and Astronomy:

nachricht Unraveling the nature of 'whistlers' from space in the lab
15.08.2018 | American Institute of Physics

nachricht Early opaque universe linked to galaxy scarcity
15.08.2018 | University of California - Riverside

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

Diving robots find Antarctic seas exhale surprising amounts of carbon dioxide in winter

16.08.2018 | Earth Sciences

Protein droplets keep neurons at the ready and immune system in balance

16.08.2018 | Life Sciences

3D inks that can be erased selectively

16.08.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>