Astronews

Lo sguardo più profondo in Orione

Pubblicato 14/07/2016 | Da Barbara Bubbi

 

FB_IMG_1468497769226Questa spettacolare immagine ripresa dal telescopio VLT dell’ESO scruta in profondità nel cuore della Nebulosa di Orione, come mai prima d’ora, rivelando un numero di nane brune e oggetti isolati di massa planetaria circa dieci volte superiore a quelli già noti. La scoperta mette in discussione lo scenario ampiamente accettato della formazione stellare in Orione. Continua a leggere→

Un buco nero clandestino potrebbe rappresentare una nuova popolazione

Pubblicato 29/06/2016 | Da Barbara Bubbi

A binary system containing a quiescent black hole about 7,200 light years from Earth.Gli astronomi hanno combinato i dati dell’osservatorio a raggi X Chandra della NASA, del telescopio spaziale Hubble e del Very Large Array (VLA) per concludere che una particolare sorgente di onde radio che si riteneva fosse una galassia lontana è in realtà un vicino sistema stellare binario contenente una stella di massa bassa e un buco nero. Questa identificazione suggerisce che ci potrebbero essere un gran numero di buchi neri passati inosservati finora nella nostra galassia. Continua a leggere→

NGC 1569, una galassia starbust

Pubblicato 29/06/2016 | Da Barbara Bubbi

This NASA/ESA Hubble Space Telescope image reveals the iridescent interior of one of the most active galaxies in our local neighbourhood — NGC 1569, a small galaxy located about eleven million light-years away in the constellation of Camelopardalis (The Giraffe). This galaxy is currently a hotbed of vigorous star formation. NGC 1569 is a starburst galaxy, meaning that — as the name suggests — it is bursting at the seams with stars, and is currently producing them at a rate far higher than that observed in most other galaxies. For almost 100 million years, NGC 1569 has pumped out stars over 100 times faster than the Milky Way! As a result, this glittering galaxy is home to super star clusters, three of which are visible in this image — one of the two bright clusters is actually  the superposition of two massive clusters. Each containing more than a million stars, these brilliant blue clusters reside within a large cavity of gas carved out by multiple supernovae, the energetic remnants of massive stars. In 2008, Hubble observed the galaxy's cluttered core and sparsely populated outer fringes. By pinpointing individual red giant stars, Hubble’s Advanced Camera for Surveys enabled astronomers to calculate a new — and much more precise — estimate for NGC 1569’s distance. This revealed that the galaxy is actually one and a half times further away than previously thought, and a member of the IC 342 galaxy group. Astronomers suspect that the IC 342 cosmic congregation is responsible for the star-forming frenzy observed in NGC 1569. Gravitational interactions between this galactic group are believed to be compressing the gas within NGC 1569. As it is compressed, the gas collapses, heats up and forms new stars.Questa immagine del telescopio Hubble rivela l’interno di una delle galassie più attive nelle nostre vicinanze, NGC 1569, una piccola galassia situata a circa undici milioni di anni luce di distanza nella costellazione della Giraffa.

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Splendide regioni di formazione stellare

Pubblicato 20/06/2016 | Da Barbara Bubbi

This image from NASAs Wide-field Infrared Survey Explorer, or WISE, highlights several star-forming regions. There are five distinct centers of star birth in this one image alone. Star-forming nebulae (called HII regions by astronomers) are clouds of gas and dust that have been heated up by nearby stars recently formed from the same cloud, and have appeared in previously featured WISE images. The largest, brightest cloud, in the upper right is known as Gum 22. Its named after Colin Gum, an Australian astronomer who surveyed the southern hemisphere sky in the early 1950s looking for star-forming regions like these. He catalogued 85 new such regions, named Gum 1 to 85 (Gum Crater on the moon was also named in his honor). Going counter-clockwise from Gum 22, the other catalogued nebulae in the image are Gum 23 (part of same cloud as 22), IRAS 09002-4732 (orange cloud near center), Bran 226 (upper cloud of the two at lower left), and finally Gum 25 at far lower left. There are also several smaller and/or more distant regions scattered throughout the image that have yet to be catalogued. Most of the regions are thought to be part of our local Orion spiral arm spur in the Milky Way Galaxy. Their distances range from about 4,000 to 10,000 light-years away. Notice the very bright green star near the lower right portion of the image. You can tell its a star because it appears to have spikes sticking out of it (diffraction spikes like these are an optical effect caused by the structure of the telescope). Bright stars in WISE images are typically blue, so you know this one is special. Known as IRAS 08535-4724, its a unique type of stellar giant called a carbon star. Carbon stars are similar to red giants stars, which are much larger than the Sun, glow brightly in longer wavelengths, and are in the late stages of their lives. But they have unusually high amounts of carbon in their outer atmospheres. Astronomers think this carbon comes either from convection currents deep witQuesta immagine del telescopio Wide-field Infrared Survey Explorer (WISE) mette in evidenza diverse splendide regioni di formazione stellare: se ne possono individuare almeno cinque in questa immagine. Si tratta di regioni HII, nubi di gas e polveri riscaldate da vicine, calde stelle di recente formazione. Continua a leggere→