Black hole at center of Milky Way unpredictable and chaotic

This X-ray image of the galactic centre merges all Swift observations from 2006 through 2013. Sagittarius A* is at the centre. Low-energy (300 to 1,500 electron volts) X-rays appear red. Green are medium-energy (1,500 to 3,000 eV). Blue are high-energy (3,000 to 10,000 eV).
Credit: NASA/Swift/N. Degenaar

An international team of researchers, led by postgraduate student Alexis Andrés, has found that the black hole at the centre of our galaxy, Sagittarius A*, not only flares irregularly from day to day but also in the long term. The team analysed 15 years’ worth of data to come to this conclusion. The research was initiated by Andres in 2019 when he was a summer student at the University of Amsterdam. In the years that followed, he continued his research, which is now to be published in Monthly Notices of the Royal Astronomical Society.

Sagittarius A* is a strong source of radio, X-rays and gamma rays (visible light is blocked by intervening gas and dust). Astronomers have known for decades that Sagittarius A* flashes every day, emitting bursts of radiation that are ten to a hundred times brighter than normal signals observed from the black hole.

To find out more about these mysterious flares, the team of astronomers, led by Andrés, searched for patterns in 15 years of data made available by NASA’s Neil Gehrels Swift Observatory, an Earth-orbiting satellite dedicated to the detection of gamma-ray bursts. The Swift Observatory has been observing gamma rays from black hole since 2006. Analysis of the data showed high levels of activity from 2006 to 2008, with a sharp decline in activity for the next four years. After 2012, the frequency of flares increased again – the researchers had a difficult time distinguishing a pattern.

In the next few years, the team of astronomers expect to gather enough data to be able to rule out whether the variations in the flares from Sagittarius A* are due to passing gaseous clouds or stars, or whether something else can explain the irregular activity observed from our galaxy’s central black hole.

“The long dataset of the Swift observatory did not just happen by accident,” says co-author and previous supervisor to Andrés, Dr Nathalie Degenaar, also at the University of Amsterdam. Her request for these specific measurements from the Swift satellite was granted while she was a PhD student. “Since then, I’ve been applying for more observing time regularly. It’s a very special observing programme that allows us to conduct a lot of research.”

Co-author Dr Jakob van den Eijnden, of the University of Oxford, comments on the team’s findings: “How the flares occur exactly remains unclear. It was previously thought that more flares follow after gaseous clouds or stars pass by the black hole, but there is no evidence for that yet. And we cannot yet confirm the hypothesis that the magnetic properties of the surrounding gas play a role either.”

Media Contact

Robert Massey
Royal Astronomical Society
rmassey@ras.ac.uk
Office: 44-207-7292-3979

Expert Contacts

Nathalie Degenaar
Anton Pannekoek Institute for Astronomy, University of Amsterdam, the Netherlands
N.D.Degenaar@uva.nl

Jakob van den Eijnden
Department of Physics, University of Oxford
jakob.vandeneijnden@st-hildas.ox.ac.uk

Alexis Andres
Institute of Astronomy, The National Autonomous University of Mexico
bandres@astro.unam.mx

www.ras.ac.uk

Media Contact

Robert Massey
Royal Astronomical Society

All latest news from the category: Physics and Astronomy

This area deals with the fundamental laws and building blocks of nature and how they interact, the properties and the behavior of matter, and research into space and time and their structures.

innovations-report provides in-depth reports and articles on subjects such as astrophysics, laser technologies, nuclear, quantum, particle and solid-state physics, nanotechnologies, planetary research and findings (Mars, Venus) and developments related to the Hubble Telescope.

Back to home

Comments (0)

Write a comment

Newest articles

Better magnets for green energy

Researchers use multicomponent alloys to make strong and ductile soft magnetic materials. Latest results now published in the journal Nature. Soft magnetic materials (SMMs) applied in electric engines transform energy…

Sound plus electrical body stimulation has potential to treat chronic pain

New technique could relieve pain for individuals with various chronic and neurological conditions. A University of Minnesota Twin Cities-led team has found that electrical stimulation of the body combined with…

Bioengineered cornea can restore sight to the blind and visually impaired

Bioengineered corneal tissue for minimally invasive vision restoration in advanced keratoconus in two clinical cohorts. Researchers and entrepreneurs have developed an implant made of collagen protein from pig’s skin, which…

Partners & Sponsors