The globular cluster
Terzan 2 in the constellation Scorpio features in this observation from
the NASA/ESA Hubble Space Telescope. Globular clusters are stable,
tightly gravitationally bound clusters of tens of thousands to millions
of stars found in a wide variety of galaxies. The intense gravitational
attraction between the closely packed stars gives globular clusters a
regular, spherical shape. As a result, images of the hearts of globular
clusters, such as this observation of Terzan 2, are crowded with a
multitude of glittering stars.
Hubble used both its Advanced Camera for Surveys and its Wide Field Camera 3
in this observation, taking advantage of the complementary capabilities
of these instruments. Despite having only one primary mirror, Hubble’s
design allows multiple instruments to be used to inspect astronomical
objects. Light from distant astronomical objects enters Hubble and is
collected by the telescope's 2.4-metre primary mirror; it is then
reflected off the secondary mirror into the depths of the telescope,
where smaller mirrors can direct light into individual instruments.
Each of the four operational instruments on Hubble is a
masterpiece of astronomical engineering in its own right, and contains
an intricate array of mirrors and other optical elements to remove any
aberrations or optical imperfections from observations, as well as
filters which allow astronomers to observe specific wavelength ranges.
The mirrors inside each instrument also correct for the slight
imperfection of Hubble's primary mirror. The end result is a
crystal-clear observation, such as this glittering portrait of Terzan 2.
Source: ESA/Hubble/potw
