An odd couple of glowing gas clouds in the constellation of Dorado
Wide-field view of NGC 2014 and NGC 2020 in the Large Magellanic Cloud
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Two very different gas clouds in the galaxy next door
ESO’s Very Large Telescope has captured
an intriguing star-forming region in the Large Magellanic Cloud — one of
the Milky Way’s satellite galaxies. This sharp image reveals two
distinctive glowing clouds of gas: red-hued NGC 2014, and its blue
neighbour NGC 2020. While they are very different, they were both
sculpted by powerful stellar winds from extremely hot newborn stars that
also radiate into the gas, causing it to glow brightly.
This image was taken by the Very Large Telescope (VLT)
at ESO's Paranal Observatory in Chile — the best place in the southern
hemisphere for astronomical observing. But even without the help of
telescopes like the VLT, a glance towards the southern constellation of
Dorado (The Swordfish or Dolphinfish [1])
on a clear, dark night reveals a blurry patch which, at first sight,
appears to be just like a cloud in the Earth's atmosphere.
At least, this may have been explorer Ferdinand Magellan's first
impression during his famous voyage to the southern hemisphere in 1519.
Although Magellan himself was killed in the Philippines before his
return, his surviving crew announced the presence of this cloud and its
smaller sibling when they returned to Europe, and these two small
galaxies were later named in Magellan's honour. However, they were
undoubtedly seen by both earlier European explorers and observers in the
southern hemisphere, although they were never reported.
The Large Magellanic Cloud (LMC) is actively producing new stars.
Some of its star-forming regions can even be seen with the naked eye,
for example, the famous Tarantula Nebula.
However, there are other smaller — but no less intriguing — regions
that telescopes can reveal in intricate detail. This new VLT image
explores an oddly mismatched pair: NGC 2014 and NGC 2020.
The pink-tinged cloud on the right, NGC 2014, is a glowing cloud of
mostly hydrogen gas. It contains a cluster of hot young stars. The
energetic radiation from these new stars strips electrons from the atoms
within the surrounding hydrogen gas, ionising it and producing a
characteristic red glow.
In addition to this strong radiation, massive young stars also
produce powerful stellar winds that eventually cause the gas around them
to disperse and stream away. To the left of the main cluster, a single
brilliant and very hot star [2]
seems to have started this process, creating a cavity that appears
encircled by a bubble-like structure called NGC 2020. The distinctive
blueish colour of this rather mysterious object is again created by
radiation from the hot star — this time by ionising oxygen instead of
hydrogen.
The strikingly different colours of NGC 2014 and NGC 2020 are the
result of both the different chemical makeup of the surrounding gas and
the temperatures of the stars that are causing the clouds to glow. The
distances between the stars and the respective gas clouds also play a
role.
The LMC is only about 163 000 light-years
from our galaxy, the Milky Way, and so is very close on a cosmic scale.
This proximity makes it a very important target for astronomers, as it
can be studied in far more detail than more distant systems. It was one
of the motivations for building telescopes in the southern hemisphere,
which led to the establishment of ESO over 50 years ago. Although
enormous on a human scale, the LMC contains less than one tenth of the
mass of the Milky Way, and spans just 14 000 light-years — by contrast,
the Milky Way covers some 100 000 light-years. Astronomers refer to the
LMC as an irregular dwarf galaxy; its irregularity, combined with its
prominent central bar of stars, suggests that interactions with the
Milky Way and another nearby galaxy, the Small Magellanic Cloud, could
have caused its chaotic shape.
This image was acquired using the visual and near-ultraviolet FOcal Reducer and low dispersion Spectrograph (FORS2) instrument attached to ESO's VLT, as part of the ESO Cosmic Gems programme [3].
Notes
[1] Although this constellation is
often identified with the swordfish there are reasons to think that the
less commonly known dolphinfish may be a better match. More details are
given here.
[2] This star is an example of a rare class called
Wolf-Rayet stars. These short-lived objects are very hot — their
surfaces can be more than ten times as hot as the surface of the Sun —
and very bright and dominate the regions around them.
[3] This picture comes from the ESO Cosmic Gems programme,
an outreach initiative to produce images of interesting, intriguing or
visually attractive objects using ESO telescopes, for the purposes of
education and public outreach. The programme makes use of telescope time
that cannot be used for science observations. All data collected may
also be suitable for scientific purposes, and are made available to
astronomers through ESO’s science archive.
More information
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Links
Contacts
Richard Hook
ESO, Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
ESO, Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
