Spiral Galaxy M100

In celebration of the 25th anniversary of NASA's first astronaut mission to service the Hubble Space Telescope in orbit, a comparison photo is being released today showing one of Hubble's first targets after its 1993 optical repair.

[RIGHT] - This photogenic celestial object, the magnificent spiral galaxy M100, is seen here as observed with Hubble's Wide Field Camera 3. Hubble's newest camera, it was installed during the last space shuttle servicing mission to Hubble in May 2009, and the M100 photo was taken a few months later. M100 is designated a grand-design spiral galaxy because of its two prominent lanes of young, blue stars. This is caused by ripples of matter in the stellar disk that propagate through the galaxy and create high-density regions of gas. These denser areas precipitate new star formation. In addition, clearly visible are two tightly wound, inner spiral arms wrapping around the core where there is a small bar pattern of stars. The yellowish color of the inner region is from older populations of stars.

[LEFT] - For comparison, this is a 1993 image of M100 taken with Hubble's Wide Field/Planetary Camera 1, which was part of an original suite of instruments launched aboard Hubble in 1990. Because of a manufacturing flaw in the primary mirror, which created an optical effect called spherical aberration, the galaxy appears blurred because it cannot be brought into a single focus. In particular, the orange foreground star below image center has tentacle-like image artifacts that are clear evidence of spherical aberration, where the starlight is not concentrated into a single point.

The same galaxy was re-photographed with the Wide Field/Planetary Camera 2, which was installed during the December 1993 space shuttle servicing mission (SM1, STS-61). The replacement camera contained corrective optics to compensate for the space telescope’s fuzzy view. Like putting contact lenses on a nearsighted patient, the M100 picture snapped into focus and was a stunning demonstration that Hubble had been returned to its expected sharpness. The M100 photo was just a preview of what was to come in subsequent servicing missions, which further improved Hubble’s capabilities. Hubble has enthralled the public with evocative and breathtaking pictures of the universe that have become even more stunning since that very first servicing mission.