Esplora Sky Tg24, Sky Sport, Sky Video
News:
Sport:
Video:
Format:
Cronaca
Politica
Mondo
spettacolo
Altre sezioni
altro
Seguici:

Il telescopio James Webb vede due galassie all'alba del cosmo. FOTO

Scienze

Sono  tra le primissime formatesi nell'universo primordiale, tra 350 e 450 milioni di anni dopo il Big Bang. Lo conferma lo studio di un team internazionale guidato dall'Italia, con l'Istituto Nazionale di Astrofisica (Inaf)

ascolta articolo

Si alza finalmente il sipario sull'alba del cosmo grazie al nuovo telescopio spaziale James Webb (Jwst), lanciato lo scorso Natale dalle agenzie spaziali di Stati Uniti (Nasa), Europa (Esa) e Canada (Csa). Nelle sue prime osservazioni scientifiche, il telescopio spaziale più grande e potente mai costruito è riuscito a immortalare due tra le primissime galassie dell'universo primordiale, tra 350 e 450 milioni di anni dopo il Big Bang. Un risultato rivoluzionario che apre una nuova era per l'astronomia, come indica lo studio pubblicato su The Astrophysical Journal Letters da un team internazionale guidato dall'Italia con l'Istituto Nazionale di Astrofisica (Inaf). Alla collaborazione hanno partecipato anche ricercatori dello Space Science Data Center dell'Agenzia Spaziale Italiana (Asi), dell'Università di Ferrara e della Statale di Milano. 

Though an estimated 100 million black holes roam among the stars in our Milky Way galaxy, astronomers have never identified an isolated black hole – until now. Following six years of meticulous observations, NASA’s Hubble Space Telescope has provided, for the first time ever, strong evidence for a lone black hole plying interstellar space. The black hole that was detected lies about 5,000 light-years away, in the Carina-Sagittarius spiral arm of our galaxy. However, its discovery allows astronomers to estimate, statistically, that the nearest isolated black hole to Earth might be as close as 80 light-years. Black holes are born from rare, monstrous stars (less than one-thousandth of the galaxy’s stellar population) that are at least 20 times more massive than our Sun. These stars explode as supernovae, and the remnant core is crushed by gravity into a black hole. Because the self-detonation is not perfectly symmetrical, the black hole may get a kick, and go careening through our galaxy like a blasted cannonball. Hubble can’t photograph the wayward black hole because it doesn’t emit any light, but instead swallows all radiation due to its intense gravitational pull. Instead, Hubble measurements capture the ghostly gravitational footprint of how the stealthy black hole warps space, which then deflects starlight from anything that momentarily lines up exactly behind it. Ground-based telescopes, which monitor the brightness of millions of stars in the rich star fields in the direction of the central bulge of our Milky Way, look for the tell-tale sudden brightening of one of them when a massive object passes between us and the star. Then Hubble follows up on the most interesting such events. Kailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland, along with his team, made the discovery in a survey designed to find just such isolated black holes. The warping of space due to the gravity of a foreground object passing in front of a star located far behind it will momentarily bend and amplify the light of the background star as it passes in front of it. The phenomenon, called gravitational microlensing, is used to study stars and exoplanets in the approximately 20,000 events seen so far inside our galaxy. The signature of a foreground black hole stands out as unique among other microlensing events. The very intense gravity of the black hole will stretch out the duration of the lensing event for over 200 days. Also, If the intervening object was instead a foreground star, it would cause a transient color change in the starlight as measured because the light from the foreground and background stars would momentarily be blended together. But no color change was seen in the black hole event. Next, Hubble was used to measure the amount of deflection of the background star’s image by the black hole. Hubble is capable of the extraordinary precision needed for such measurements. The star’s image was offset from where it normally would be by two milliarcseconds. That’s equivalent to measuring the diameter of a 25-cent coin in Los Angeles as seen from New York City. This astrometric microlensing technique provided information on the mass, distance, and velocity of the black hole. The amount of deflection by the black hole’s intense warping of space allowed Sahu’s team to estimate it weighs seven solar masses. The isolated black hole is traveling across the galaxy at 90,000 miles per hour (fast enough to travel from Earth to the moon in less than three hours). That’s faster than most of the other neighboring stars in that region of our galaxy. “Astrometric microlensing in conceptually simple but observationally very tough,” said Sahu. “It is the only technique for identifying isolated black holes.” When the black hole passed in front of a background star located 28,000 light-years away in the galactic bulge, the starlight coming toward Earth was amplified for a duration of 265 days as the black hole passed by. However, it took several years of Hubble observations to follow how the background star’s position appeared to be deflected by the bending of light by the foreground black hole. The existence of stellar-mass black holes has been known since the early 1970’s, but all of them—until now—are found in binary star systems. Gas from the companion star falls into the black hole, and is heated to such high temperatures that it emits X rays. About two dozen black holes have had their masses measured in X-ray binaries through their gravitational effect on their companions. Black hole masses in X-ray binaries inside our galaxy range from 5 to 20 solar masses. Black holes detected in other galaxies by gravitational waves from mergers between black holes and companion objects have been as high as 90 solar masses. “Detections of isolated black holes will provide new insights into the population of these objects in our Milky Way,” said Sahu. He expects that his program will uncover more free-roaming black holes inside our galaxy. But it is a needle-in-a-haystack search. The prediction is that only one in 1500 microlensing events are caused by isolated black holes. NASA’s upcoming Nancy Grace Roman Space Telescope will discover several thousand microlensing events out of which many are expected to be black holes, and the deflections will be measured with very high accuracy. In a 1916 paper on general relativity, Albert Einstein predicted that his theory could be tested by observing the sun’s gravity offsetting the apparent position of a background star. This was tested by astronomer Arthur Eddington during a solar eclipse on May 29, 1919. Eddington measured a background star being offset by 2 arc seconds, validating Einstein’s theories. Both scientists could hardly have imagined that over a century later this same technique would be used – with unimaginable precision of a thousandfold better — to look for black holes across the galaxy.
Isolated Black Hole

Le galassie più antiche mai viste

Le due galassie, tra le più antiche mai viste finora, sono state individuate grazie alle osservazioni del lontano ammasso di galassie Abell 2744 e di due regioni del cielo ad esso adiacenti, realizzate dal telescopio spaziale tra il 28 e il 29 giugno nell'ambito del progetto Glass-Jwst Early Release Science Program. Il gruppo guidato da Marco Castellano, ricercatore Inaf a Roma, è stato tra i primi a usare i dati di Jwst, pubblicando un pre-print sulla piattaforma arXiv a luglio, solo cinque giorni dopo che i dati erano stati resi disponibili. "C'era molta curiosità nel vedere finalmente cosa Jwst poteva dirci sull'alba cosmica, oltre naturalmente al desiderio e all'ambizione di essere i primi a mostrare alla comunità scientifica i risultati ottenuti dalla nostra survey Glass", afferma Castellano. "Non è stato facile analizzare dei dati così nuovi in breve tempo: la collaborazione ha lavorato 7 giorni su 7 e in pratica 24 ore su 24 anche grazie al fatto di avere una partecipazione che copre tutti i fusi orari". 

The Pillars of Creation are set off in a kaleidoscope of color in NASA’s James Webb Space Telescope’s near-infrared-light view. The pillars look like arches and spires rising out of a desert landscape, but are filled with semi-transparent gas and dust, and ever changing. This is a region where young stars are forming – or have barely burst from their dusty cocoons as they continue to form. Newly formed stars are the scene-stealers in this Near-Infrared Camera (NIRCam) image. These are the bright red orbs that sometimes appear with eight diffraction spikes. When knots with sufficient mass form within the pillars, they begin to collapse under their own gravity, slowly heat up, and eventually begin shining brightly. Along the edges of the pillars are wavy lines that look like lava. These are ejections from stars that are still forming. Young stars periodically shoot out supersonic jets that can interact within clouds of material, like these thick pillars of gas and dust. This sometimes also results in bow shocks, which can form wavy patterns like a boat does as it moves through water. These young stars are estimated to be only a few hundred thousand years old, and will continue to form for millions of years. Although it may appear that near-infrared light has allowed Webb to “pierce through” the background to reveal great cosmic distances beyond the pillars, the interstellar medium stands in the way, like a drawn curtain. This is also the reason why there are no distant galaxies in this view. This translucent layer of gas blocks our view of the deeper universe. Plus, dust is lit up by the collective light from the packed “party” of stars that have burst free from the pillars. It’s like standing in a well-lit room looking out a window – the interior light reflects on the pane, obscuring the scene outside and, in turn, illuminating the activity at the party inside. Webb’s new view of the Pillars of Creation will help researchers revamp models of star formation. By identifying far more precise star populations, along with the quantities of gas and dust in the region, they will begin to build a clearer understanding of how stars form and burst out of these clouds over millions of years. The Pillars of Creation is a small region within the vast Eagle Nebula, which lies 6,500 light-years away. Webb’s NIRCam was built by a team at the University of Arizona and Lockheed Martin’s Advanced Technology Center.

leggi anche

Pilastri della creazione, telescopio Webb cattura nuova immagine. FOTO
JWST NIRCam image of the z ~ 6.2 Sunrise Arc, including the lensed star Earendel, marked with an arrow. This 15farcs2 × 12farcs4 color image combines all eight NIRCam images on a 0farcs02 pixel scale. ANSA/THE ASTROPHYSICAL JOURNAL LETTERS +++ ANSA PROVIDES ACCESS TO THIS HANDOUT PHOTO TO BE USED SOLELY TO ILLUSTRATE NEWS REPORTING OR COMMENTARY ON THE FACTS OR EVENTS DEPICTED IN THIS IMAGE; NO ARCHIVING; NO LICENSING +++

La ricercatrice: "Nuovo capitolo per l'astronomia"

Tanta fatica è stata ricompensata da risultati straordinari. "Queste osservazioni sono rivoluzionarie: si è aperto un nuovo capitolo dell'astronomia", commenta Paola Santini, ricercatrice dell'Inaf a Roma e coautrice dell'articolo. "Già dopo i primissimi giorni dall'inizio della raccolta dati, Jwst ha mostrato di essere in grado di svelare sorgenti astrofisiche in epoche ancora inesplorate". Queste antiche galassie "sono molto diverse dalla Via Lattea o da altre grandi galassie che vediamo oggi intorno a noi", spiega il responsabile del progetto Glass-Jwst Tommaso Treu, professore all'Università della California a Los Angeles e tra i protagonisti di una conferenza stampa organizzata dalla Nasa per presentare i nuovi risultati. 

FdLX8uiWQAAOWzT

leggi anche

Dal telescopio Webb un’immagine nitida degli anelli di Nettuno
Image cutouts of Earendel in each JWST filter are shown in the top row in native pixels (SW 0farcs031; LW 0farcs063). Individual exposure cutouts are fit with a PSF point-source model, and the sums of these four exposure-level models are shown in the middle row. The residuals are also calculated on the level of individual exposures, then summed to produce the bottom row of this figure. The residuals are consistent with noise in each filter, indicating that Earendel is a pointlike source and supporting the interpretation that it is a distant lensed star. ANSA/THE ASTROPHYSICAL JOURNAL LETTERS +++ ANSA PROVIDES ACCESS TO THIS HANDOUT PHOTO TO BE USED SOLELY TO ILLUSTRATE NEWS REPORTING OR COMMENTARY ON THE FACTS OR EVENTS DEPICTED IN THIS IMAGE; NO ARCHIVING; NO LICENSING +++

Il dato sulla distanza tra le due galassie deve essere confermato

Le osservazioni del Jwst sembrano indicare che le galassie nell'universo primordiale fossero molto più luminose, anche se più compatte del previsto. Se ciò fosse vero, potrebbe rendere più facile per il telescopio trovare un numero ancor maggiore di queste galassie precoci nelle sue prossime osservazioni. La distanza delle due antiche galassie dovrà essere confermata con maggior precisione, ma si tratta già dei candidati più robusti selezionati ad oggi con dati del Jwst. A confermare l'affidabilità dei risultati è l'accordo con quanto riscontrato in altri studi, come il lavoro guidato da Rohan Naidu dell'Harvard Center for Astrophysics (Usa), pubblicato sempre su The Astrophysical Journal Letters. 

sole nasa

leggi anche

Il Sole sembra sorridere: spettacolare foto dal telescopio della Nasa

Scienze: Ultime notizie

Bombo, scoperta specie che sopravvive sott'acqua fino a una settimana

Scienze

Si tratta delle regine del comune bombo orientale. La scoperta, avvenuta inizialmente per caso a...

Bombo, scoperta specie che sopravvive sott'acqua fino a una settimana

STEM Women Congress, prima edizione a Milano il 28 maggio 2024

Scienze

La giornata si articolerà con un’alternanza di speech delle imprese e panel di condivisione...

STEM Women Congress, prima edizione a Milano il 28 maggio 2024

Napoli, il documentario su tv svizzera: "Sarà sepolta dalla cenere"

Scienze

Potrebbe accadere nel caso di un'eruzione dei Campi Flegrei e avrebbe ripercussioni sul Sud...

Napoli, il documentario su tv svizzera: "Sarà sepolta dalla cenere"

Scoperto il buco nero stellare più massiccio della Via Lattea

Scienze

Chiamato Gaia BH3, batte il record di dimensioni finora detenuto dal buco nero Cygnus X-1. La...

Scoperto il buco nero stellare più massiccio della Via Lattea

Festival delle Scienze a Roma, programma ed eventi da non perdere

Scienze

Dal 16 al 21 aprile torna la tanto attesa kermesse romana dedicata al mondo scientifico....

Festival delle Scienze a Roma, programma ed eventi da non perdere

In evidenza

Scienze: I più letti