The Universe Becomes More Certain

NGC 4151 (Credit: NASA)

Using a new scaling technique, a collaborative team from Denmark, UK and Japan have calculated the mass of, and distance to, a supermassive black hole with groundbreaking accuracy.

The black hole inhabits an active galactic nuclei (AGN) located within galaxy, NGC 4151. Previous estimates placed the galaxy approximately 13.2 Mpc (1 megaparsec ≈ 3.26 million light-years) from Earth. However, distances ranging from 4–29 Mpc have also been recorded. These uncertainties are detrimental to black hole calculations, with current mass estimates standing at MBH = (3.76 ± 1.15) x 107 solar masses. New research, published in Nature, re-adjusts both of these figures to an increased distance of (19 ± 2.5) Mpc and mass, MBH = (5.4 ± 1.8) x 107 solar masses. These are large readjustments that will have important consequences for current theoretical models.

The new technique, first proposed in 2011, relies on measuring the radius of AGN galaxies through a process called, reverberation mapping. Converging UV (from black hole region) and infrared lightwaves (from outer disc/torus) are then used to calculate an angle, using Earth based interferometers. By obtaining these values, trigonometric relationships can then be used to calculate the absolute distance to an object.

The success of this method means astronomers now have a direct way of measuring deep field objects without the need to combine multiple, already established, techniques. This has been a long standing historical problem, as each individual technique creates its own uncertainty making error propagation a serious problem.

Distance measuring is the bedrock of many astronomical/cosmological models; by reducing uncertainties in calculations scientists will develop a deeper understanding of the universe’s scale and structure. Masses of black holes, spatial dimensions and the rate of cosmological expansion will all benefit from this advancement, creating a more certain world around us.

‘The distance to faraway objects is currently determined using a complicated “cosmic distance ladder” that employs several different techniques that apply only over specific distance ranges. The new AGN technique, in contrast, could be used over a wide range of cosmic distances’, said Hamish Johnston (IOP), ‘giving astronomers “an entirely separate and totally independent set of cosmic-distance measurement tools’.

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Paul Hattle

As a strong advocate for science and learning, I am a passionate supporter of the 'Campaign for Science and Engineering' (CaSE) Fellow of the 'Royal Astronomical Society' (RAS) Associate Member of the 'Institute of Physics' (IOP) & 'The Institute of Scientific and Technical Communicators' (ISTC)

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