Une spectaculaire collision frontale entre deux galaxies crée un tsunami de naissance d’étoiles

Arp 143

Une spectaculaire collision frontale entre deux galaxies est à l’origine d’une frénésie de naissance d’étoiles de forme triangulaire, comme le montre une nouvelle image du télescope spatial Hubble de la NASA. Le duo de galaxies en interaction est collectivement appelé Arp 143. Le couple contient la galaxie spirale scintillante, déformée et productrice d’étoiles NGC 2445 à droite, ainsi que sa compagne moins voyante, NGC 2444 à gauche. Crédit : NASA, ESA, STScI, Julianne Dalcanton Center for Computational Astrophysics, Flatiron Inst. / UWashington, Joseph DePasquale (STScI)

Les interactions entre ces deux galaxies créent un tsunami de naissance d’étoiles

Si vous aimez regarder des galaxies aux formes étranges, il n’y a pas de meilleur endroit que le “Catalogue Arp des Galaxies Péculières”.

Compilé par l’astronome Halton Arp en 1966, le catalogue est un compendium de 338 galaxies bizarres en interaction. Mais Arp n’a pas compilé le catalogue juste pour montrer des galaxies qui semblent étranges. Il pensait que ces galaxies particulières étaient d’excellents laboratoires pour étudier les processus physiques qui déforment les galaxies elliptiques et spirales d’apparence normale. Il a été l’un des premiers à suggérer que les rencontres galactiques pouvaient former des étoiles en rafales.

Son point de vue contrastait avec celui de nombreux astronomes des années 1960, qui considéraient les galaxies difformes comme de simples curiosités. Ils croyaient en un univers “à l’emporte-pièce”, selon lequel la plupart des galaxies étaient ordonnées et symétriques. Mais Arp croyait en un autre type d’univers, un univers rempli de violence et de naissance.

Une de ces galaxies d’Arp qui explose avec de nouvelles étoiles se trouve dans cette image. Télescope spatial Hubble image du système Arp 143. Les deux galaxies de ce système sont entrées en collision frontale, alimentant l’explosion de formation d’étoiles de forme triangulaire. La paire contient la galaxie spirale déformée et productrice d’étoiles NGC 2445 à droite, ainsi que sa compagne moins voyante, NGC 2444 à gauche.


Une collision frontale spectaculaire entre deux galaxies a alimenté une frénésie inhabituelle de naissance d’étoiles de forme triangulaire, comme le montre une nouvelle image de ;” data-gt-translate-attributes=”[{” attribute=””>NASA’s Hubble Space Telescope. Credit: NASA’s Goddard Space Flight Center, Lead Producer: Paul Morris

A spectacular head-on collision between two galaxies fueled the unusual triangular-shaped star-birthing frenzy, as captured in a new image from NASA’s Hubble Space Telescope.

The interacting galaxy duo is collectively called Arp 143. The pair contains the glittery, distorted, star-forming spiral galaxy NGC 2445 at right, along with its less flashy companion, NGC 2444 at left.

Astronomers suggest that the galaxies passed through each other, igniting the uniquely shaped star-formation firestorm in NGC 2445, where thousands of stars are bursting to life on the right-hand side of the image. This galaxy is awash in starbirth because it is rich in gas, the fuel that makes stars. However, it hasn’t yet escaped the gravitational clutches of its partner NGC 2444, shown on the left side of the image. The pair is waging a cosmic tug-of-war, which NGC 2444 appears to be winning. The galaxy has pulled gas from NGC 2445, forming the oddball triangle of newly minted stars.

“Simulations show that head-on collisions between two galaxies is one way of making rings of new stars,” said astronomer Julianne Dalcanton of the Flatiron Institute’s Center for Computational Astrophysics in New York and the University of Washington in Seattle. “Therefore, rings of star formation are not uncommon. However, what’s weird about this system is that it’s a triangle of star formation. Part of the reason for that shape is that these galaxies are still so close to each other and NGC 2444 is still holding on to the other galaxy gravitationally. NGC 2444 may also have an invisible, hot halo of gas that could help to pull NGC 2445’s gas away from its nucleus. So, they’re not completely free of each other yet and their unusual interaction is distorting the ring into this triangle.”

NGC 2444 is also responsible for yanking taffy-like strands of gas from its partner, stoking the streamers of young, blue stars that appear to form a bridge between the two galaxies.

These streamers are among the first in what appears to be a wave of star formation that started on NGC 2445’s outskirts and continued inward. Researchers estimate the streamer stars were born between about 50 million and 100 million years ago. But these infant stars are being left behind as NGC 2445 continues to pull slowly away from NGC 2444.

Stars no older than 1 million to 2 million years are forming closer to the center of NGC 2445. Hubble’s keen sharpness reveals some individual stars. They are the brightest and most massive in the galaxy. Most of the brilliant blue clumps are groupings of stars. The pink blobs are giant, young star clusters still enshrouded in dust and gas.

Although most of the action is happening in NGC 2445, it doesn’t mean the other half of the interacting pair has escaped unscathed. The gravitational tussle has stretched NGC 2444 into an odd shape. The galaxy contains old stars and no new starbirth because it lost its gas long ago, well before this galactic encounter.

“This is a nearby example of the kinds of interactions that happened long ago. It’s a fantastic sandbox to understand star formation and interacting galaxies,” said Elena Sabbi of the Space Telescope Science Institute in Baltimore, Maryland.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Leave a Comment