X7, a mysterious object about to be engulfed by our central black hole

This supermassive black hole is Sgr A*. The very first image of it was obtained last year thanks to a worldwide network of telescopes, the Event Horizon Telescope. It took five years to successfully make this shot, but in reality, we have been observing this black hole for much longer. For nearly 25 years, we have been following it continuously to better understand how the physics around a supermassive black hole works, how the black hole influences its environment…

The engulfment of a mysterious object by the black hole at the center of our galaxy

And because the black hole is by definition invisible, we observe the objects that orbit near it to understand its influence. Most of the studies carried out until now have focused on the celestial bodies, the nearby stars, in particular on their speed, to determine how their movements are modified by the presence of Sgr A*…. Thousands of data were therefore collected as part of this work.

In this study published in

The Astrophysical Journal, the researchers reused part of these 25 years of data, collected by the Keck Observatory in Hawaii, not to study the populations of stars, but an object which is in what is called the interstellar medium , between the stars therefore. And it is about X7… With all these data, the scientists were able to describe the morphology and the dynamics of this cloud of gas.

As a result, X7 has changed shape over the past 25 years, on the scale of human time. This is a unique opportunity to study the effect of gravitation around our central black hole.

Interview with Anna Ciurloa researcher at UCLA, the University of California at Los Angeles and first author of this study.


1 min

Image from the Keck Observatory in the summer of 2021 showing gas and dust structures in the galactic center.

Image from the Keck Observatory in the summer of 2021 showing gas and dust structures in the galactic center.

– A. Ciurlo et al./UCLA GCOI/W. M. Keck Observatory

Images of the evolution of the shape of X7 between 2002 and 2021

Images of the evolution of the shape of X7 between 2002 and 2021

– A. Ciurlo et al./UCLA GCOI/W. M. Keck Observatory

The Scientific Method

58 min

Raccoon dog singled out in search for origin of SARS Cov-2

New genetic analyzes on the Wuhan market would show the presence of animals positive for SARS-Cov-2, including these

cartoon dog, small raccoon-like mammals that are sold for their fur. These would not be the only animals detected, there would also be civets and other mammals. And I only use the conditional here, because nothing has yet been published. The samples were taken at the beginning of 2020, but only put online on a large database at the end of January 2023. It was a French researcher, Florence Débarre, who flushed out these sequences somewhat by chance. The WHO was therefore only informed of their existence on March 12.

Publications will appear soon, and this will allow us to see more clearly, especially since this discovery would contradict a prepublication of Chinese scientists at the origin of the sampling published on February 25 deposited on

Research Square. A study which concludes that no animal sample positive for sars-Cov-2 had been detected in the market.

This does not mean that these raccoon dogs are the source of the spread of the virus, or even that these animals were infected, only that they were present at the time of the emergence of the epidemic, and this therefore revives the hypothesis of the zoonotic origin of SARS-COV-2.

Science, CQFD

58 min

The first complete mapping of a fly’s brain

Because beyond its apparent simplicity, the fly is one of the complex organisms. Scientists who publish in

Science had to make a thousand brain slices from a larva of Drosophila, the fruit fly, and then made

electron microscopy images, to finally reconstitute all the neural circuits of this tiny brain, neuron after neuron and synapse after synapse.

As a result, we obtain in detail the connections of 3,000 neurons, i.e. a network of almost 550,000 synapses. This is what researchers call the connectome. Thanks to this connectome, they were able to demonstrate that three quarters of their neurons are associated with reward and learning circuits. Until now, only organism connectomes not exceeding a hundred neurons had been mapped. This is the first time an insect brain has been probed with this level of detail.

A new IPCC report will be released today

This is the last part of the sixth assessment cycle started in 2015. IPCC scientists met last week in Switzerland in Interlaken to write this

ultimate synthesis. It will contain all the information contained in the three working groups of the IPCC: the first evaluating the physical bases of the climate, the second the consequences of climate change and the third the strategies for mitigating these effects.

This is supplemented by a summary of three special reports, as well as a summary for policymakers. A document of around ten pages in which each sentence, even each word, must be validated by the representatives of the 195 States that make up the IPCC, which therefore takes some time and may somewhat delay its publication, planned for later -noon.

Thanks to Anna Ciurlo and Aurélien Hees for their valuable explanations

Science, CQFD

58 min

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