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The NASA/ESA Hubble Space Telescope has been orbiting the Earth well above our planet's atmosphere for over 25 years. | NASA
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Top 10 Astronomical Discoveries Of All Time

From the discovery that Earth isn't at the center of the universe to detecting the 'echo' of the Big Bang, here are some of the most profound discoveries in astronomical history.

February 17, 2016
7:00 AM EST
In January and February 2015, all five naked-eye planets were visible in the night sky. | NASA/JPL-Caltech
This graphic shows the position of all the planets in our solar system, but is not to scale and includes some stylistic additions (such as the galaxy at lower right). | NASA/JPL
Artist's impression of the gravity field around Earth as well as Gravity Probe B, a spacecraft intended to measure space-time (height, width, length and time). | NASA
Auroras sparkle in these images of Uranus captured by the Hubble Space Telescope in 2011. | NASA, ESA, and L. Lamy (Observatory of Paris, CNRS, CNES)
The speed of light puts a serious damper in our plans to visit the Andromeda Galaxy, which is 2.5 million light-years away from Earth. Inset is a possible black hole. | X-ray: NASA/CXC/SAO/R. Barnard, Z. Lee et al.; Optical: NOAO/AURA/NSF/REU Program/B. Schoening, V. Harvey and Descubre Foundation/CAHA/OAUV/DSA/V. Peris
The cosmic microwave background is a remnant of the energy of the Big Bang. | NASA
Artist's impression of the Big Bang believed to have started the universe, and the universe's subsequent expansion. | NASA
This Hubble Space Telescope image shows evidence of a gravitational lens at its center (the faint circle surrounding the middle galaxies). In some cases, gravitational lenses could be evidence of dark matter. In this case, however, a galaxy cluster likely created the distortion. | NASA, ESA, K. Sharon (Tel Aviv University) and E. Ofek (Caltech)
Geysers erupt on Saturn's icy moon Enceladus, as viewed by the Cassini spacecraft in false color. | NASA/JPL/Space Science Institute
Artist's impression of the James Webb Space Telescope, which is expected to launch in 2018. | NASA