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Under the lens of gravity, it is sometimes seen double. This is the case with one of the last galaxies observed by Hubble, the space telescope that has made the history of astronomical observations in the last thirty years, and which now seems to not want to live in the shadow of the newcomer, the James Webb Space Telescope. The galaxy is called SGAS J143845 + 145407comes from the distant and ancient universe, and its peculiarity is that appears double due to gravitational lensing. It is part of a series of Hubble observations that exploit this effect of general relativity to see inside the galaxies in the early Universe.
This intriguing observation from the NASA / ESA Hubble Space Telescope shows a gravitationally lensed galaxy with the long-winded identification SGAS J143845 + 145407. Gravitational lensing has resulted in a mirror image of the galaxy at the center of this image, creating a captivating centerpiece. Gravitational lensing occurs when a massive celestial body – such as a galaxy cluster – causes a sufficient curvature of spacetime for the path of light around it to be visibly bent, as if by a lens. Appropriately, the body causing the light to curve is called a gravitational lens, and the distorted background object is referred to as being “lensed”. Gravitational lensing can result in multiple images of the original galaxy, as seen in this image, or in the background object appearing as a distorted arc or even a ring. Another important consequence of this lensing distortion is magnification, allowing astronomers to observe objects that would otherwise be too far away or too faint to be seen. Hubble has a special flair for detecting lensed galaxies. The telescope’s sensitivity and crystal-clear vision allow it to see faint and distant gravitational lenses that cannot be detected with ground-based telescopes because of the blurring effect of Earth’s atmosphere. Hubble was the first telescope to resolve details within lensed images of galaxies, and is capable of imaging both their shape and internal structure. This particular lensed galaxy is from a set of Hubble observations that take advantage of gravitational lensing to peer inside galaxies in the early Universe. The lensing reveals details of distant galaxies that would otherwise be unobtainable, and this allows astronomers to determine star formation in early galaxies. This in turn gives scientists a better insight into how the overall evolution of galaxies has unfolded.ESA / Hubble & NASA, J. Rigby
Light bends to gravity
The effect we are talking about is the same one who made a show the first deep field of James Webb, but its manifestations can be very different. The concept behind the phenomenon, theorized by Einstein in general relativity, is that any celestial body with a curved mass spacetime (as a ball, more or less heavy, would do if placed on a tight sheet) and consequently causes a deflection of light rays that pass in its vicinity. In the event that a massive celestial body, or a set of celestial bodies such as a cluster of galaxies, is between us and the source we are observing, it will act as a real lens: the light we will see will be distorted, amplified or duplicated according to the particular system configuration. The phenomenon is called, not surprisingly, gravitational lens (or gravitational lensing). The effects, we said, are different: from the increase in the flow of light arriving from distant sources, to the production of distorted images (in the form of arcs and rings, Einstein’s rings), to the generation of multiple images of the same object, as for SGAS J143845 + 145407.
Not just beautiful to look at
Hubble was the first telescope to resolve details within images of gravitationally lensed galaxies, and is able to photograph both their shape and their internal structure. Precisely because this phenomenon, in addition to distorting, amplifies and focuses the light, it can be used to see details that would otherwise be unreachable. A sort of telescope within a telescope which, in the case of this galaxy and other distant galaxies, offers the possibility of understanding how they were born and raised in the early universe. Studying the light and the structures, in fact, their star formation history can be determinedor at what pace they formed their stars, to understand how they evolve over time until reaching today’s galaxies, the ones we see in our cosmic neighborhood.
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