Des bouts d’astéroïde vont peut-être s’écraser sur Mars et c’est la faute de la Nasa
news.movim.eu / Numerama · Saturday, 13 April - 08:00
La Nasa avait réussi à dévier la trajectoire d'un astéroïde lors de la mission DART. Mais l'impact du vaisseau a peut-être créé un dommage collatéral. Des roches éjectées de l'astéroïde se dirigeraient vers Mars.
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Le JWST et Hubble sont d’accord sur l’expansion de l’Univers… mais le mystère s’épaissit
news.movim.eu / JournalDuGeek · Tuesday, 12 March - 17:02
Cette photo montre un phénomène unique sur les anneaux de Saturne
news.movim.eu / Numerama · Friday, 22 December - 16:09
La Nasa a pris une photo de Saturne et de ses anneaux. Jusque-là, rien de si exceptionnel. Cependant, la photo montre un phénomène très rare, à l'origine encore mystérieuse : des rayons d'anneaux.
Le télescope Hubble se remet d’une nouvelle défaillance
news.movim.eu / Numerama · Friday, 8 December - 12:45
La Nasa prévoit de remettre le télescope spatial Hubble en service ce 8 décembre. L'observatoire a connu quelques problèmes ces derniers jours au niveau d'un de ses gyroscopes.
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An exoplanet is getting vaporized but is trying to hide it
news.movim.eu / ArsTechnica · Tuesday, 15 August, 2023 - 17:06
Enlarge / Artist's conception of the atmosphere being blasted off an exoplanet. (credit: NASA, ESA, and Joseph Olmsted (STScI) )
Some planets cannot hold on to their atmospheres. It's thought that most of whatever atmosphere Mars may have had was annihilated by the solar wind billions of years ago, even as Earth and Venus held on to theirs. But there are planets that orbit so close to their star that atmospheric loss is inevitable. With at least one of them, we’ve learned that it is also unpredictable.
Exoplanet Au Mic b is that planet. It orbits the young, hot, and temperamental red dwarf star Au Microscopii (Au Mic), which is only 23 million years old—nothing compared to our 4-billion-year-old sun. NASA’s Hubble Space Telescope caught this scorched world losing a portion of its atmosphere.
When a team of scientists from the NASA Goddard Space Flight Center, Dartmouth College, the University of California at Santa Cruz, and other institutions analyzed the Hubble observations, they were confused by the planet’s erratic behavior. There would be evidence of atmospheric loss in some of the data, then suddenly none at all. It was unpredictable.
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Hubble continue de se faire photobomber, et c’est de pire en pire
news.movim.eu / JournalDuGeek · Wednesday, 8 March, 2023 - 07:30
Les chercheurs tirent la sonnette d'alarme, la pollution visuelle générée par certains satellites modernes créent des perturbations.
Hubble continue de se faire photobomber, et c’est de pire en pire
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Even Hubble’s seeing a growing number of satellite tracks
news.movim.eu / ArsTechnica · Tuesday, 7 March, 2023 - 20:13 · 1 minute
A combination of space junk and a growing constellation of functional satellites like SpaceX's Starlink have astronomers worried about the potential for orbital materials to interfere with observations. And justifiably so, given that researchers are currently arguing over whether one observation represents one of the farthest supernovae ever observed or a spent Russian booster .
This clutter is obviously a big problem for ground-based observatories, which sit below everything in orbit. But several observatories, including the Hubble Space Telescope, sit in low-Earth orbit, which places them below many satellites. And a new survey of Hubble images shows that it's capturing an increasing number of satellite tracks in its images. So far, this hasn't seriously compromised its science, but it clearly shows that orbiting observatories aren't immune to these problems.
The work came from a citizen science project, the Hubble Asteroid Hunter , which organized volunteers to search for the tracks asteroids left in long-exposure Hubble observations. If an asteroid happens to pass through Hubble's field of view during this exposure, it can leave a short streak in the resulting image. But the participants started noting that some of the streaks they were seeing crossed Hubble's entire field of view during a single image (the project maintains a forum where the volunteers can discuss their work).
Un trou noir affamé a transformé une étoile en donut
news.movim.eu / Numerama · Monday, 16 January, 2023 - 10:47
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Scientists may have found the first water worlds
news.movim.eu / ArsTechnica · Thursday, 15 December, 2022 - 20:37 · 1 minute
Enlarge (credit: NASA, ESA, Leah Hustak)
Two planets that were originally discovered by the Kepler mission may not be what we thought they were. Based on an initial characterization, it was thought these planets were rocky bodies a bit larger than Earth. But continued observation has produced data that indicates the planets are much less dense than we originally thought. And the only realistic way to get the sort of densities they now seem to have is for a substantial amount of their volume to be occupied by water or a similar fluid.
We do have bodies like this in our Solar System—most notably the moon Europa, which has a rocky core surrounded by a watery shell capped by ice. But these new planets are much closer to their host star, which means their surfaces are probably a blurry boundary between a vast ocean and a steam-filled atmosphere.
There are two main methods for finding an exoplanet. One is to watch for dips in the light from their star, caused by planets with an orbit that takes them between the star and Earth. The second is to track whether the star's light periodically shifts to redder or bluer wavelengths, caused by the star moving due to the gravitational pull of orbiting planets.
