More than any other telescope in orbit, Hubble has expanded the frontiers of human knowledge. For 25 years, astronomers have used it to peer deep into distant galaxies with unrivalled clarity, revealing the breathtaking beauty of our universe. In the April issue of National Geographic, some of the most stunning images beamed back for the telescope have been revealed. The Horsehead Nebula is a cold, dark cloud of gas and dust, silhouetted against the bright nebula IC 434. The bright area at the top left edge is a young star still embedded in its nursery of gas and dust. The nebula is relatively close at 1,500 light years from Earth . Hubble has helped scientists understand how planets and galaxies form, detected black holes and changed our theories surrounding dark energy, a mysterious force that causes the universe to expand faster and faster as time goes on. The hundreds of thousands of images beamed back from Hubble have helped scientists unravel cosmic mysteries as well as estimate the age of the universe to about 14 billion years old. Among them is the Horsehead Nebula - a cold, dark cloud of gas and dust, silhouetted against the bright nebula IC 434 1,500 light years from Earth. Another remarkable image shows a display of starlight, glowing gas, and silhouetted dark clouds of interstellar dust that forms the spiral galaxy NGC 130. This is one of Hubble's largest images ever made of a complete galaxy. Some of the most striking scenes are created during the death throes of intermediate-mass stars, when great clouds of superheated gas are expelled into space. In 2002, a dull star in an obscure constellation suddenly became 600,000 times more luminous than our sun, temporarily making it the brightest star in the Milky Way. The mysterious star, called V838 Monocerotis, has since faded back to obscurity. But observations by the Hubble Space Telescope of a phenomenon called a 'light echo' around the star have uncovered remarkable new features . This huge, young stellar grouping, called R136, is only a few million years old and resides in the 30 Doradus Nebula, a turbulent star-birth region in the Large Magellanic Cloud, a satellite galaxy of the Milky Way . The telescope captured a display of starlight, glowing gas, and silhouetted dark clouds of interstellar dust in this 4-foot-by-8-foot image of the barred spiral galaxy NGC 130. This is one of Hubble's largest images ever made of a complete galaxy . 'Launched into orbit aboard the space shuttle Discovery on April 24, 1990, amid flurries of hope and hype, the Hubble Space Telescope promptly faltered,' explained Timothy Ferris writing in April's issue of National Geographic . An iconic image from Hubble captures the dying breaths from planetary nebula NGC 6302. Known perhaps more appropriately as the Bug or Butterfly Nebula, this complex nebula lies roughly 3800 light-years away from us within the Milky Way. But at first, astronomers didn't expect Hubble to amount to much. 'Launched into orbit aboard the space shuttle Discovery on April 24, 1990, amid flurries of hope and hype, the Hubble Space Telescope promptly faltered,' explained Timothy Ferris writing in April's issue of National Geographic. 'Rather than remaining locked on its celestial targets, it trembled and shook, quaking like a photophobic vampire whenever sunlight struck its solar panels. 'Opening its protective front door to let starlight in perturbed the telescope so badly that it fell into an electronic coma. 'Worst of all, Hubble turned out to be myopic. Its primary light-gathering mirror, eight feet in diameter and said to be the smoothest large object ever fashioned by humans, had been figured perfectly wrong.' The telescope's design had been a compromise. While astronomers had wanted a bigger telescope in a higher orbit, they could only get 350 miles (550km) high so that astronauts in space could reach it for repairs. Next month, the telescope - which is the length of a large school bus and weighs as much as two adult elephants - will celebrate its 25th anniversary. To celebrate Hubble astronomers recently revisited one of its most stunning photos to date, known as 'the pillars of creation.' Taken in 1995, the team revealed never-before-seen details of three giant columns of cold gas bathed in the scorching ultraviolet light from a cluster of young, massive stars in a small region of the Eagle Nebula, or M16. The new Hubble photo is sharper than the original, and also has a  wider field of view. It also reveals the base of the cold, gassy columns for the first time. And in January the sharpest and largest image ever taken of the Andromeda Galaxy - the nearest spiral galaxy to our Milky Way. The Hubble image shows more than 100 million stars and thousands of star clusters embedded in a section of the galaxy’s pancake-shaped disc stretching across over 40,000 light-years. The sweeping view, which reveals one third of our galactic neighbour, also suggests that the galaxy may have been battered by a collision with another galaxy two billion years ago. The panoramic image has 1.5 billion pixels — meaning you would need more than 600 HD television screens to display the whole image. It traces the galaxy from its central galactic bulge on the left, where stars are densely packed together, across lanes of stars and dust to the sparser outskirts of its outer disc on the right. 'That human beings find them to be as beautiful and evocative as photos of earthly sunsets and mountain peaks affirms anew that nature is all of a piece, and that we're part of it,' said Ferris. Some of the most striking scenes are created during the death throes of intermediate-mass stars, when great clouds of superheated gas are expelled into space. This image from Hubble captures the dying breaths from planetary nebula NGC 6302. Known perhaps more appropriately as the Bug or Butterfly Nebula, this complex nebula lies roughly 3800 light-years away from us within the Milky Way . Click on the image to zoom in . The new Hubble photo of the pillars of creation is sharper than the original, and also has a wider field of view. It also reveals the base of the cold, gassy columns for the first time .
Images include the Horsehead Nebula, which is a cold, dark cloud of gas and dust 1,500 light years away . Another remarkable image is of NGC 130, one of Hubble's largest images ever made of a complete galaxy . Some of the most striking images beamed back from Hubble were created during the death throes of stars .