The coming weeks are likely to be important for the future of ground-based astronomy in the face of the threat of satellite constellations. How is it a threat, what are astronomers doing, why are these weeks important? Thread 👇
Since 2019, satellite constellations, mainly Elon Musk's Starlink are being laucnhed to provide internet access all over the globe, with low latency. The first launches have surprised astronomers.
Some observations have become unusable: For example:
In the visible range, the larger the field of view of the telescopes, the more they are affected, like the Vera Rubin Observatory: arxiv.org/abs/2006.12417
For radio observatories, such as the future SKA in South Africa and Australia, the largest astronomical project of the coming decades, data transmissions from satellite constellations to the ground could be problematic.
These radio observatories are built far from any civilization, in order to probe the confines of the Universe without the pollution of waves due to human activity ... but there these waves could come from the sky!
What are astronomers doing? They met to discuss the impact of these satellites, and of light pollution in general, on astronomy and biodiversity. The conference was attended by ~900 participants, with a summary (of 279 pages) here: iau.org/static/publica...
Why is this important today? The results of this work will be presented to the COPUOS (Committee on the Peaceful Uses of Outer Space) of the UN from April 19.
What do the astronomers want? That these constellations limit as little as possible our observations of the Universe and our quest for answers to fundamental questions for humanity: how was the Universe formed, does life exist elsewhere? etc...
There are currently international rules for the use of wave frequencies, with some frequencies reserved for science. However, there are no rules for light pollution. We would like to avoid that it becomes the far west!
During this COPUOS Technical Committee meeting, sky pollution will be discussed for the first time, including a presentation of the International Astronomical Union's report "Dark and Quiet Skies for Science and Society".
This may be our only chance to preserve our sky, for astronomers but also for humanity, in a more or less near future.
What are we doing before this meeting? In France we are actively discussing, via @SF2A_astro, with the CNRS (via @INSU_CNRS), the national center for space studies, the ministries of education, research and industry and foreign affairs.
Internationaly, @IAU_org will be finalising its preparation tomorrow for the presentation at COPUOS next week.
Everyone agrees that it is important to consider the impact of current and future satellite constellations on astronomy. It is important that the industrialists who build or will build these constellations also think about this.
International working groups have been formed to quantitatively measure the impact of these satellites on astronomy and to be able to discuss constructively with industry to mitigate the impact on astronomy.
The CNRS institution, via @INSU_CNRS, will encourage French astronomers to get involved in these studies, in order to preserve our sky, while discussing constructively with all actors in the space field.
The @IAU_org reports show that light pollution (not only from satellites) has an impact on astronomy, but also on biodiversity and human health.
Thank you for sharing to raise awareness on the importance of preserving our sky, which is arguably humanity's most beautiful common heritage! We hope that the next meetings at COPUOS of the United Nations will help to protect the starry sky!
Pour mieux comprendre notre monde, il faut comprendre les sciences. Mais connaître les faits n'est peut-être pas le plus important: il faut comprendre comment se construit un savoir. Ça vous dit de comprendre la démarche scientifique avec l'exemple de la gravitation?
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Cela fait plusieurs millénaires que les humains observent le ciel. A l'œil nu il est possible de voir 7 astres errants, qui bougent par rapport aux étoiles, fixes: la lune, Mars , Mercure, Jupiter, Vénus, Saturne et le Soleil!
Ces 7 astres errants ont donné les 7 jours de la semaine. Lundi la Lune, Mardi Mars, Mercredi Mercure, Jeudi Jupiter, Vendredi Vénus, Samedi Saturne et Dimanche le soleil (Sunday). Planète veut d'ailleurs dire "astre errant" en grec!
J'ai la sensation de vivre une nuit historique en France, des centaines de personnes m'envoient des photos d'aurores boréales visibles partout dans le pays. Il se passe quoi?
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Quand vous regardez le soleil (jamais le regarder directement), dites vous que c'est une étoile qui s'est formée il y a 5 milliards d'années... avec le gaz d'étoiles mortes des milliards d'années avant! J'explique la formation des étoiles ici:
Donc, en gros, le Soleil s'est formé dans un grand nuage de gaz qui s'est effondré sous sa propre masse. La gravitation pousse ce gaz vers le centre, du coup c'est hyper dense au centre... des petits atomes d’hydrogène fusionnent pour donner des atomes d'hélium
Pour commencer, il faut remonter au Big Bang, concept introduit en 1927 par l’Abbé belge Georges Lemaître, qui propose que l'Univers est en expansion, et devait donc être plus petit dans le passé (pas con hein?)
En 1929, Edwin Hubble observe des galaxies au Mt Wilson en Californie. Il se rend compte que les galaxies, ces "univers-iles" contenant des milliards d'étoiles, s'éloignent de nous. Et plus elles sont éloignées, plus elles s'éloignent vite. L'Univers est bien en expansion!
On avait perdu le contact avec la sonde Voyager 1, partie de la Terre il y a 46 ans et qui vogue maintenant à plus de 24 milliards de kilomètre de nous, après avoir quitté le système solaire.
On vient de re-rentrer en contact avec la sonde. Thread en images👇
Toutes les informations sur ces sondes, qui sont toujours en contact avec la Terre sont ici: Elles se déplacent à ~60000 km/h!! voyager.jpl.nasa.gov/mission/status/
On a souvent du mal à se l'imaginer, car on vit autour d'une étoile solitaire, mais la plupart des étoiles sont au moins doubles.
La vie d'une étoile dépende de sa masse. Plus une étoile est massive, plus elle évolue vite. Les étoiles comme le Soleil vont devenir des géantes rouges, immenses et froides.