2023-10-11 19:04:26
For more than 30 years, the Hubble telescope has revealed images of galaxies taken from the near infrared to the ultraviolet to the visible. In the James-Webb era, NASA reminded us – for six days – of what we owe to Hubble on this subject. Here is the continuation of the article that we devoted to the festival of galaxy images.
Here is the second part of the article dedicated to the week of NASA which each day gave a quick portrait of one of the galaxies observed with the Hubble telescope, while it is still active to reveal secrets of the kingdom of nebulae opened just under a century ago by Edwin Hubble.
The Hubble telescope once once more shows us the image of a galaxy discovered by the British astronomer William Herschel. He observed NGC 1087 in 1785 in the constellation Whale. But as always, it was not until the work of astronomers in the 1930s and beyond that we discovered that this spiral galaxy is located approximately 80 million light years from the Milky Way with a diameter of approximately 87,000 light years away.
NGC 1087 is one of the barred spirals and the image above, in false colors, shows it as seen by Hubble’s instruments in ultraviolet, visible and near-infrared light. According to the accompanying NASA press release: the dark red streaks are cold molecular gas, the raw material from which stars form. The bright pink spots mark areas where new stars are forming, characterized by the presence of ionized hydrogen, oxygen and sulfur. The bluer regions are home to hot young stars formed earlier in this galaxy’s life ».
The NGC 6951 galaxy, pictured below, is a type II Seyfert galaxy (named following the American astronomer Carl Keenan Seyfert who began to study them seriously in 1943) with a black hole at its center supermassive surrounded by a ring of stars, gas and dust approximately 3,700 light years across and thought to have formed between 1 and 1.5 billion years ago. But its discoverers, the French astronomer Jérôme Coggia in 1877 and the American astronomer Lewis Swift in 1878, might not have known this, any more than this spiral that we can observe in the constellation Cepheus was located regarding 78 million light years from the Milky Way.
The entire galaxy measures approximately 75,000 light years in diameter and is visible from the northern hemisphere, as explained in the NASA press release which also specifies that on the Hubble image in visible and infrared light we can see turbulent gas regions, shown in dark red, surrounding bright blue pinpricks that are star clusters.
NGC 6951 has remarkably been the site of at least six supernovae that have been detected over the past 25 years.
As a cosmic photographer, NASA’s Hubble Space Telescope has taken more than a million photos documenting the Universe. These images illustrate, explain and inspire us with their grandeur. But how are these images taken and processed?
This incredible video explains how Hubble images are taken and processed. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Automatically translate”. Choose “French”. © NASA’s Goddard Space Flight Center
NGC 4654 is one of the galaxies that can be observed in the Virgo cluster. It is located approximately 55 million light years from Earth. As it lies just north of the celestial equator, it is visible on Earth from the Northern Hemisphere and most of the Southern Hemisphere. Images from the Hubble Space Telescope, taken in visible, ultraviolet and infrared light, were necessary to obtain this false-color photo.
NGC 4654 appears to have had a gravitational interaction with companion galaxy NGC 4639 regarding 500 million years ago. We suspect that its movement through the plasma at millions of kelvins of the galactic cluster exerts a pressure on it which tends to strip it of its gas content, resulting in a long, thin trail of hydrogen gas on the south side. is of the galaxy, as explained in the NASA press release. Oddly, the rate of star formation remains comparable to that of other galaxies despite this process of gas depletion which tends to remove the possibility of gravitational collapse of matter to produce open clusters of young stars.
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