Astrophysicist, CNRS


Astrocladistics is still alive!

I was delighted to see a new paper deposited this November 2020 into ArXiv: A phylogenetic analysis of galaxies in the Coma Cluster and the field: a new approach to galaxy evolution by Martinez-Marin et al. This paper uses the NJ algorithm to perform a chemical tagging analysis of a few hundreds of galaxies within […]

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Maximum Parsimony on a large data set of galaxies

Maximum Parsimony is known to be NP-complete and thus cannot really be used for a number of taxa larger than, say, 1000. Since the beginning of astrocladistics I was concerned by this problem, and it took us several years to find a solution. Indeed, we must cluster the data first, that is make a similarity […]

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Stellar Evolutionary Tracks

Unsupervised classification looks for patterns in the data set, patterns that can be associated with “classes”. There are basically two kinds of patterns: clumps and tracks. Clumps exist because of similarity between objects, and tracks are formed by relationships. Most of the diversity in the Universe is due to evolution. Astronomical objects, such as stars, […]

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Other phylogenetic studies in astrophysics

2016 seems is a new milestone for astrocladistics: fifteen years after the beginning of this adventure, and ten years after the first papers were published, other phylogenetic analyses,  in which I am not involved, have been published. They use either Maximum Parsimony (cladistics) or Neighbour Joining: Cladistical Analysis of the Jovian Satellites, Holt et al […]

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From the Realm of the Nebulae to the Society of Galaxies. Dialogues on a Century of Research

This is the title of a new fantastic book that is quite timely: From the Realm of the Nebulae to the Society of Galaxies Dialogues on a Century of Research D’Onofrio, M.; Rampazzo, R. & Zaggia, S. (Eds.) Astrophysics and Space Science Library, Vol 45 Springer International Publishing, 2016. In order to outline possible […]

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Multivariate Approaches to Classification in Extragalactic Astronomy

This the title of our paper that makes a review of the tentative to base a (unsupervised) classification of galaxies on learning machine techniques : Multivariate Approaches to Classification in Extragalactic Astronomy Didier Fraix-Burnet, Marc Thuillard, Asis Kumar Chattopadhyay Frontiers in Astronomy and Space Sciences, 2015, 2 (3) It is an Open Access publication (not […]

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Why multivariate analyses are not more widespread in astrophysics, especially in the extragalactic domain? I have not really the answer (I have some ideas though…), but let me show some plots that should help convince (astro)physicists. Firstly, do you remember this conference help in 1990? This shows that the debate about the morphological classification of […]

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Transforming the Hubble Tuning Fork into a Piano

A Tuning Fork is a device used to tune musical instruments. It vibrates at a single frequency, it is a pure sound of a single note. The Hubble Diagram not only looks like a Tuning Fork, but is also sounds like it: morphology is a single note, a single parameter, and it is based on […]


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Gamma Ray Bursts and Cladistics

Another kind of astronomical objects has been successfully analyzed with maximum parsimony: Gamma Ray Bursts! These are still mysterious objects, extremely violent, that emit a lot of gamma-rays during tenths of a second to several seconds. Gamma-rays are very energetic electromagnetic radiation, more so than X-rays, UV and of course visible light. Gamma-ray detectors on […]

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Astrocladistics and galaxies: a milestone

Astrocladistics has the power to renew our classification of galaxies. I have explained why this is necessary. But after more than 10 years of developments, where are we standing in this ambitious and long term goal? A first step has been made forward in our publication: A six-parameter space to describe galaxy diversification. Fraix-Burnet, D., […]

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