The Whirlpool Galaxy, also known as M51 or NGC 5194, is one of the
most spectacular examples of a spiral galaxy. With two spiral arms
curling into one another in a billowing swirl, this galaxy hosts over a
hundred billion stars and is currently merging with its companion, the
smaller galaxy NGC 5195.
Around 30 million light-years away, the
Whirlpool Galaxy is close enough to be easily spotted even with
binoculars. Using the best telescopes available both on the ground and
in space, astronomers can scrutinise its population of stars in
extraordinary detail.
In this image, observations performed at
three different wavelengths with ESA’s Herschel and XMM-Newton space
telescopes are combined to reveal how three generations of stars coexist
in the Whirlpool Galaxy.
The infrared light collected by Herschel
– shown in red and yellow – reveals the glow of cosmic dust, which is a
minor but crucial ingredient in the interstellar material in the
galaxy’s spiral arms. This mixture of gas and dust provides the raw
material from which the Whirlpool Galaxy’s future generations of stars
will take shape.
Observing in visible and ultraviolet light,
astronomers can see the current population of stars in the Whirlpool
Galaxy, since stars in their prime shine most brightly at shorter
wavelengths than infrared. Seen at ultraviolet wavelengths with
XMM-Newton and portrayed in green in this composite image are the
galaxy’s fiercest stellar inhabitants: young and massive stars pouring
powerful winds and radiation into their surroundings.
The image
also shows the remains of previous stellar generations, which shine
brightly in X-rays and were detected by XMM-Newton. Shown in blue, these
sources of X-rays are either the sites where massive stars exploded as
supernovae in the past several thousand years, or binary systems that
host neutron stars or black holes, the compact objects left behind by
supernovae.
Source: ESA - Space Images
