December 1, 2022

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The five pictures that changed the history of science

The Earth-orbiting Hubble Space Telescope – NASA/Flickr/CCby2.0

The James Webb Telescope is about to depart for space, where it will observe the universe in infrared near the Big Bang. And if it succeeds, it will push the boundaries of our astronomical knowledge that was made by its predecessor: the Hubble Space Telescope. It was April 24, 1990, when five astronauts aboard the space shuttle Discovery deposited the space telescope into an orbit about 600 kilometers above the Earth’s surface. After solving a problem with mirrors – which did not allow us to accurately observe the objects of the universe – thanks to a mission carried out with another shuttle in 1993, the Hubble eye began to show things we had not seen before, taking us almost to the limits of time and space.

Starting with our own solar system, it has allowed us, year after year to photograph the planets, to observe the general evolution of their atmosphere or photograph truly unique phenomena. Like, for example, he watched the extreme flight of Comet Schoemaker-Levy 9 smashed by Jupiter’s gravity as it passed in the summer of 1992. Two years later Hubble followed the fragments as they fell into the core. The atmosphere of Jupiter. Then he transmitted moving pictures of the scars caused by the collision.

Over the years, he documented the turbulent birth of stars almost everywhere in our galaxy. Through his infrared observation instruments, he was able to penetrate the dust clouds enveloping the Star Cradle, revealing them like we’ve never seen them before. One of the most exciting images he has released for us is the one in which you can see disks of dust around some newborn stars hidden in the depths of the Orion Nebula. There, completely new solar systems are being born just as they did in ours four and a half billion years ago.

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Stars often end their lives catastrophically, disintegrating into giant starbursts, known as supernovae. For a few glorious months, it could become one of the brightest objects in the entire universe, surpassing all the other stars in their galaxy in splendor. Among these, Hubble witnessed the scene of supernova 1987A. The telescope observed a ring of gas formed around the point of the supernova explosion. Over the years, I’ve watched some bright spots appear along the ring, as if they were a gemstone on a necklace. Those cosmic pearls were ignited by supersonic shock waves released as the star exploded.

Then he studied and photographed galaxies, which are huge islands of stars like ours that have hundreds of billions inside. And although the universe is made up of more vacuum than matter, galaxies can collide. Don’t forget the Bullet Cluster photo where two giant groups of galaxies collide about 3 billion 720 million light-years away from us.

Then “investigate” what is happening near black holes. Each galaxy has a black hole in its core, and Hubble has studied the movement of nearby stars, collecting data that allowed us to obtain the masses of black holes. What is in the center of our galaxy, for example, has a mass 4 million times the mass of the Sun. Hubble also allowed us to observe ‘gravitational lenses’.

They are a kind of mirage of the universe. They form because gravity bends space and thus deflects light rays. Thus it happens that the light from distant galaxies is distorted and amplified by the gravitational field of objects (such as very massive galaxies) that it encounters on its way to Earth. It’s like looking through a huge magnifying glass and the result is the so-called “gravitational lens” effect.

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It is also thanks to Hubble that by measuring the “red shift” (a phenomenon similar to what happens to the sound of an ambulance siren when it moves away from the listener: the sound is “stretched” precisely because the ambulance itself is removed) from the farthest objects that were able to Determine their location at the start of light and thus the age of the universe, which turns out to be 13 billion and 800 million years.

Then there is an iconic image of not only what Hubble was able to observe, but of all of humanity: the “ultra-deep field”. It’s an image that shows nearly 10,000 galaxies of different ages, sizes, shapes, and colors. The smallest and reddish galaxies, around 100, may be among the most distant galaxies known, which existed when the universe was only 800 million years old. The earliest galaxies – the largest, brightest and most famous spiral and elliptical galaxies – formed about a billion years ago, when the universe was 13 billion years old. The image required 800 exposures, taken during Hubble’s 400 orbits around the Earth. The total exposure time was 11 and a half days. But Hubble’s life did not end. His observations will continue alongside those of the James Webb Telescope.