Sky and Telescope - June 2015 - 16

News Notes

BLACK HOLES I New Stars in the Shadow of Sagittarius A*
Array to image what appear to be 44 protoplanetary disks, reservoirs of dust and
gas that feed low-mass newborn stars.
Intense ultraviolet radiation and stellar
winds have shaped the cocoons around
these objects into comet-like fuzzies, with
bright heads and blown-back tails.
The disks sit in two clusters, lying
2 and 2.6 light-years away from Sgr A*,
respectively. These clusters are both
between 10,000 and 100,000 years old.
Even though nearby stars' winds and
intense radiation will steal mass from
these disks, Yusef-Zadeh estimates they
could have enough material left to form
planets around the protostars.
The formation of low-mass stars suggests that, rather than a one-time formation event, stars are probably churned out
continuously in our galaxy's center, says
Andreas Eckart (University of Cologne,
Germany). The galactic center has one
of the highest star-formation rates in the
Milky Way, so if this activity is longstanding, that makes theorists' conundrum more than a temporary curiosity.

OBIT I Donald C. Parker, 1939-2015
Planetary imaging pioneer Don Parker
passed away in Miami, Florida, on the
evening of February 22nd from lung cancer. He maintained his razor-sharp intel-

June 2015 sky & telescope

ligence, wit, and kindness to the end.
Parker caught the astronomy bug at a
young age. He built several telescopes
during the 1950s, including an 8-inch f/7.5
Newtonian reﬂector that was featured in
the November 1957 S&T. After serving as a
medical oﬃcer in the U.S. Navy, he began
a career in anesthesiology and resumed
observing the planets, particularly Mars.
He was a former director of the Association of Lunar and Planetary Observers
(ALPO), where he became acquainted with
Lowell Observatory astronomer Charles
F. Capen. With Capen's encouragement
and mentorship, Parker quickly rose to the
forefront of amateur planetary photography. In 1988 he coauthored the book Introduction to Observing and Photographing
the Solar System with Capen and fellow

Two scenarios exist for explaining star
formation near the black hole, both of
which use the black hole's pull to their
advantage. In 2005, Sergei Nayakshin
(University of Leicester, UK) and colleagues suggested that a cloud might
break apart in the strong gravitational
ﬁeld, reassembling into a disk encircling
the black hole. The disk could then form
massive stars the same way that disks
around stars form planets. That might
explain why many young, massive stars
encircle Sgr A* in two rings.
Last year, another method suggested
by Behrang Jalali (University of Cologne,
Germany) and colleagues suggested that
molecular clouds on highly elongated
orbits that pass very close to the black
hole would spaghettify, compressing even
as they stretch out along their orbit. That
compression would in turn trigger star
formation inside the clouds. A spaghettiﬁed, star-bearing cloud might explain the
mystery object G2, which hurtled past Sgr
A* last spring, the team proposed.
■ MONICA YOUNG

amateur Thomas A. Dobbins.
Parker continued to be a pioneer in
planetary observing and imaging techniques, and he played a role in developing
many of the methods used in digital planetary imaging today. He's also credited
with the discovery of several features on
Mars and Jupiter. Many of his 20,000plus images have supported professional
researchers at NASA, JPL, and other
institutions, and he coauthored scores of
papers in scientiﬁc journals, popular magazines, and news sites worldwide. In 1994,
the International Astronomical Union
named asteroid 5392 Parker in his honor
for his contributions to solar system science. A frequent speaker at amateur conventions, he delighted audiences with his
colorful and often self-deprecating humor.
It was an honor to be his friend. ✦
■ SEAN WALKER

SEAN WALKER

Observations suggest that several
dozen low-mass stars, and eventually
perhaps even planets, are forming just
2 light-years from our galaxy's supermassive black hole.
Theorists still don't understand how
stars manage to coalesce around the Milky
Way's central black hole, Sgr A*, which
has a mass of 4.3 million Suns. The ﬁerce
gravitational ﬁeld ought to rip clouds apart
long before stars have a chance to form.
And that's if the intense radiation from
nearby stars in the galaxy's busy downtown doesn't blow the clouds apart.
Yet young, massive stars circle the
behemoth. Previous observations show
that massive stars have formed within
a few light-years of the black hole as
recently as 10,000 years ago.
Now Farhad Yusef-Zadeh (Northwestern University) and colleagues have
added another layer to the mystery with
their discovery of low-mass stars forming around the black hole, reported in an
upcoming Astrophysical Journal Letters.
The astronomers used the Very Large

Sky and Telescope - June 2015

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