The blue dot in this image marks the spot of an energetic pulsar -- the magnetic, spinning core of star that blew up in a supernova explosion. NASA's NuSTAR discovered the pulsar by identifying its telltale pulse.
Millions of galaxies populate the patch of sky known as the COSMOS field, short for Cosmic Evolution Survey, a portion of which is shown here. Even the smallest dots in this image are galaxies, some up to 12 billion light-years away.
Comet C/2013 UQ4 (Catalina) first looked like an asteroid when NASA's NEOWISE team first observed it on December 31, 2013. These exposures were taken that day, when the comet was at a distance of about 2.9 AU from the sun.
A composite image of the spiral galaxy NGC 4258 showing X-ray emission observed with NASA's Chandra X-ray Observatory (blue) and infrared emission observed with NASA's Spitzer Space Telescope (red and green).
This infrared image from NASA's Spitzer Space Telescope shows N103B -- all that remains from a supernova that exploded a millennium ago in the Large Magellanic Cloud, a satellite galaxy 160,000 light-years away from our own Milky Way.
Studied by astronomers, Serpens Cloud Core is one of the youngest collections of stars ever seen in our galaxy. This infrared image combines data from NASA's Spitzer with shorter-wavelength observations from the Two Micron All Sky Survey.
Astronomers have found cosmic clumps so dark, dense and dusty that they throw the deepest shadows ever recorded. A large cloud looms in the center of this image of the galactic plane from NASA's Spitzer Space Telescope.
This composite image shows one of the clusters, NGC 2024, which is found in the center of the so-called Flame Nebula about 1,400 light years from Earth. Astronomers have studied two star clusters using NASA's Chandra and infrared telescopes.
The magnetic field of our Milky Way galaxy as seen by ESA's Planck satellite. This image was compiled from the first all-sky observations of polarized light emitted by interstellar dust in the Milky Way.
This frame from an animation shows the coldest brown dwarf yet seen, and the fourth closest system to our sun. Called WISE J085510.83-071442.5, this dim object was discovered through its rapid motion across the sky.