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 Astronomers see 'warm' glow of Uranus's rings
21.06.2019 | University of California - Berkeley

nachricht A new force for optical tweezers awakens
19.06.2019 | University of Gothenburg

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: Fraunhofer IDMT demonstrates its method for acoustic quality inspection at »Sensor+Test 2019« in Nürnberg

From June 25th to 27th 2019, the Fraunhofer Institute for Digital Media Technology IDMT in Ilmenau (Germany) will be presenting a new solution for acoustic quality inspection allowing contact-free, non-destructive testing of manufactured parts and components. The method which has reached Technology Readiness Level 6 already, is currently being successfully tested in practical use together with a number of industrial partners.

Reducing machine downtime, manufacturing defects, and excessive scrap

Im Focus: Successfully Tested in Praxis: Bidirectional Sensor Technology Optimizes Laser Material Deposition

The quality of additively manufactured components depends not only on the manufacturing process, but also on the inline process control. The process control ensures a reliable coating process because it detects deviations from the target geometry immediately. At LASER World of PHOTONICS 2019, the Fraunhofer Institute for Laser Technology ILT will be demonstrating how well bi-directional sensor technology can already be used for Laser Material Deposition (LMD) in combination with commercial optics at booth A2.431.

Fraunhofer ILT has been developing optical sensor technology specifically for production measurement technology for around 10 years. In particular, its »bd-1«...

Im Focus: The hidden structure of the periodic system

The well-known representation of chemical elements is just one example of how objects can be arranged and classified

The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

Cooling with the sun

25.06.2019 | Power and Electrical Engineering

Robocabs: The mobility of the future?

25.06.2019 | Studies and Analyses

Skipping Meat on Occasion May Protect Against Type 2 Diabetes

25.06.2019 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>