Some photos taken by the Hubble Space Telescope receive large amounts of media attention, such as the recent “rose of galaxies” photo. But the telescope takes a lot of photos – 750,000 in its first 15 years!  So it’s inevitable that the archives will contain many beautiful images which few people stumble upon.
I recently came across the photo above, taken in 1994 and released in 1999, showing Supernova 1994D (the bright star near the bottom-left corner) in the galaxy NGC 4526, about 50 million light-years away.
This photo gallery contains some incredible pictures of the Super-Kamiokande neutrino observatory, under Mount Kamioka in Japan.
The observatory consists of a vast underground chamber in the shape of a cylinder, filled with 11 million gallons (50,000 tons) of extremely pure water. The inside of the chamber is covered with 11,146 photomultiplier tubes (extremely sensitive light-detectors). When a neutrino passes through the chamber and hits a water molecule, a flash of light is produced, which is recorded by the photomultiplier tubes.
Photo No.15 is particularly eye-catching, showing two technicians in an inflatable boat, checking the photomultiplier tubes while the chamber is being filled with water.
Recently, NASA released two spectacular photos taken by the Hubble Space Telescope, showing very dense star fields in our own Milky Way galaxy and in the Andromeda Galaxy.
The photo above shows the Sagittarius-I Window “in the crowded central bulge of our galaxy, 26,000 light-years away”. 
The size of the field of view on the sky is roughly that of the thickness of a human fingernail held at arm’s length, and within this region, Hubble sees about a quarter million stars towards the bulge. 
I highly recommend you check out the larger versions of this photo, to fully appreciate the extraordinary quantity of stars.