Sky and Telescope - November 2017 - 27

Background
galaxy
VFTS 016

Hodge 301

R139

H II regions
(ionized hydrogen)
R136

VFTS 102

NGC 2060

VFTS 352

1 arcminute

p TREASURE MAP The marriage of two Hubble near-infrared images
with ground-based visible and hydrogen-alpha views yields this sweeping
view of 30 Doradus and its surroundings. Key features are labeled and
listed in the table. NGC 2070 comprises much of the left-hand complex.

N ASA / ESA / ESO / D. LENNON, E. SA BBI, E T A L.

Nature of the Beast
The star cluster NGC 2070, 130 light-years across, lies at the
Tarantula's heart. O-type stars, the hottest and most luminous of all, are the rarest in our galaxy, with a population
distribution of roughly 1 in 3 million. Yet NGC 2070 boasts
some 2,400 O and B stars spread among a nest of sub-clusters, including the powerhouse called R136. The potent ionizing radiation from these stars collectively is 500 times greater
than that from the Orion Nebula's hot, young suns. In fact, it
creates the most active region of star formation in the Local
Group of galaxies, which includes the Milky Way and more
than 50 of its neighbors.

Researchers long believed that 30 Doradus was an evolved
H II region with no major ongoing star formation. Then in
1992 observers spotted several protostars enshrouded in nebulosity. Further evidence came with the discovery of numerous infrared sources and intense radio emissions from OH
radicals, a telltale sign of rapid starbirth. Today, we know 30
Doradus to be a region where star formation has taken place
in multiple distinct epochs that continue to the present day.
The lack of red supergiants in R136, despite the large
number of suitably massive stars, constrains the cluster to be
less than 5 million years old. Further HTTP-based research
led by Michele Cignoni (University of Pisa, Italy) shows that
the star-formation rate peaked about 2 million years ago. This
makes R136 notable: Few generations of stars we can observe
are only a few million years old.
The oldest and second largest cluster is Hodge 301. Modelling led by Elena Sabbi (Space Telescope Science Institute),
s k y a n d t e l e s c o p e . c o m * N O V E M B E R 2 0 17

27



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Sky and Telescope - November 2017

Table of Contents for the Digital Edition of Sky and Telescope - November 2017

Contents
Sky and Telescope - November 2017 - Cover1
Sky and Telescope - November 2017 - Cover2
Sky and Telescope - November 2017 - 1
Sky and Telescope - November 2017 - Contents
Sky and Telescope - November 2017 - 3
Sky and Telescope - November 2017 - 4
Sky and Telescope - November 2017 - 5
Sky and Telescope - November 2017 - 6
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