NASA captures an image showing a galaxy bursting with life
A new Hubble view of NGC 7456 shows a spiral galaxy that is packed with action in both its bright center and its arms. NGC 7456 sits about 51 million light years away in the southern constellation Grus.
The image highlights clumpy arms streaked with dust and dotted with rosy star-forming pockets. It also hints at something wilder – high energy X-rays and a brilliant core powered by compact objects that feed on nearby matter.
Galaxy NGC 7456 seen by Hubble
Hubble’s sharp vision separates young blue clusters, lanes of dark dust, and compact knots where gas collapses into newborn stars.
Those rosy patches mark regions where hydrogen glows as new stars flood their neighborhoods with energetic light.
Samaresh Mondal of the Nicolaus Copernicus Astronomical Center in Warsaw (NCAC), studies extreme X-ray sources in this galaxy and others.
His team’s findings help explain why NGC 7456 looks so lively in multiple kinds of light.
Where the pink glow comes from
The reddish pink light traces hydrogen gas emitting at the H-alpha line near 656 nanometers. That glow is a basic signature of HII regions – zones of ionized hydrogen around hot, short-lived stars.
These bubbles do not last long on cosmic timescales. Young massive stars pour out ultraviolet radiation that energizes nearby gas, it lights up while stars are forming, then fades as winds and radiation disperse the clouds.
The galaxy also hosts ultraluminous X-ray sources known as ULXs. These are compact objects, black holes or neutron stars, that shine above about 1039 erg per second in X-rays.
ULXs are interesting because they tell us how matter behaves when it falls inward faster than simple models allow. Some ULXs are neutron stars that are bright enough to challenge old assumptions about what these objects can do.
Clues from time delays and iron
XMM Newton has observed NGC 7456 more than once, revealing several compact X-ray beacons within the galaxy. A deep 2018 observation of roughly 90,000 seconds identified multiple ULXs, including two with luminosities around 6 to 10 × 1039 erg per second.
“We report the first detection of an Fe K alpha line and soft X-ray lag in the ultraluminous X-ray source NGC 7456 ULX-1,” stated Mondal.
This source in particular, NGC 7456 ULX 1, shows spectral features and timing behavior that act like fingerprints of the regions close to the compact object.
That study measured a soft X-ray delay of about 1,300 seconds relative to harder photons. The iron signature of near 6.4 keV indicates reflection from material in the inner system, where gravity and radiation compete.
NGC 7456 has an energetic core
At NGC 7456’s center sits a supermassive black hole that lights up its surroundings. An active, bright nucleus like this is a hallmark of an active galaxy, often called a Seyfert galaxy when the host is a spiral.
Activity at the core comes from accretion – gas spiraling inward and heating up as it loses energy. That process creates glowing disks, jets in some cases, and high energy radiation that outshines the stars near the center.
The picture that emerges is of a galaxy that is busy on multiple fronts. In the arms, young stars carve out cavities in gas clouds while their radiation makes hydrogen glow.
Across the disk, ULXs pulse with power as matter rains onto compact objects. Near the core, the central engine adds its own energetic signature, a bright nucleus that stamps NGC 7456 as active in X-rays and optical emission lines.
What astronomers are still asking
What exactly powers each ULX in this galaxy, a small black hole or a neutron star pushing matter past typical limits.
Reviews note that ULXs can include neutron star accretors, which helps explain their extreme brightness and timing behavior.
How does star formation feed the central engine, and how does the central engine push back? Gas cycles between stars, compact remnants, and the nucleus, and tracking that flow across wavelengths is the next step.
Why NGC 7456 is useful
NGC 7456 offers a clean laboratory for connecting star formation, compact objects, and nuclear activity.
It sits near enough that modern telescopes can resolve individual regions and monitor changes over hours to years, all within one target.
Hubble shows the structures where stars form. XMM Newton and other X-ray observatories map compact sources and the core, letting teams match high energy behavior to features seen in visible and ultraviolet light.
Longer X-ray observations can check if ULX 3 and ULX 4 really switch on and off, which would mark them as temporary systems.
Extra follow-up studies of the light can also sharpen the view of the iron signal in ULX 1 and show how near the surrounding gas is to the compact object.
High resolution optical spectra will track emission lines in the nucleus and out in the disk. Radio and infrared data can weigh obscured star formation and any feedback from the center that may shape future stellar births.
Information taken from a NASA online press release.
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