Sky & Telescope - May 2024 - 11

IN BRIEF
Dan Caselden Wins
Chambliss Award
GALAXIES
Milky Way-like Galaxies Started Out Pickle-Shaped
WHAT DID THE MILKY WAY look like
shortly after it was born? Decidedly
different than it does now, according
to a new study that will appear in the
Astrophysical Journal.
New observations from the James
Webb Space Telescope reveal that small,
star-forming galaxies in the early universe
- the forerunners of the Milky
Way - had elongated shapes. Some
appeared long and round like pickles,
others long and flat like surfboards.
Previous observations from the
Hubble Space Telescope hinted at this
morphological evolution, says Lennox
Cowie (University of Hawai'i, Manoa).
But Hubble was only able to probe the
appearance of galaxies residing in a
universe already 2 billion years old, and
some astronomers thought their elongated
shapes might be happenstance,
due to viewing early disk galaxies edgeon,
like frisbees seen from the side.
Now, Webb's images of galaxies from
the Cosmic Evolution Early Release Science
(CEERS) survey reveal some galaxies
have truly stretched-out shapes just
650 million years after the Big Bang.
To investigate the role of viewing
angle, Viraj Pandya (Columbia University)
and colleagues first categorized
the shape of each galaxy detected in
the CEERS survey as an ellipsoid. They
then modeled what 1 million different
ellipsoids would look like as seen
from 100,000 random viewing angles
each. Comparing these distributions
to the spread of shapes they actually
pAt first glance, the true shape of these early
galaxies that the James Webb Space Telescope
has imaged is unclear. However, the distribution
of galaxy shapes shows that small star-forming
galaxies in the early universe are truly elongated.
observed, they found that the farthest
and smallest star-forming galaxies tend
to be truly elongated - pickle- and
surfboard-shaped rather than edge-on
frisbees. (The method is statistical in
nature, Pandya cautions, so they can't
tell the shapes of individual galaxies but
rather the likelihood of different shapes
within a group of galaxies.)
" The JWST observations are beautiful, "
Cowie says. " The analysis is very
careful and detailed. " But understanding
why galaxy shapes changed over
cosmic time will be difficult, he adds.
Pandya's team suggests that early
galaxies are elongated because they
came together along the dark matter-
dominated filaments that crisscross the
universe. Like cars on a highway, galactic
collisions in filaments would have
occurred along a preferred direction,
leading to elongated shapes.
But Cowie thinks subtler actions
might be at play. " It probably has little
to do with the cosmology, " he says, " and
is mostly caused by the changes in the
gas inflow, the dynamics of the interstellar
medium, and the structure of the
star formation. "
The next aim of Pandya's team will
be to analyze larger samples by combining
CEERS with other Webb data sets.
¢MONICA YOUNG
At the 243rd meeting of the American Astronomical
Society, the society conferred
the Chambliss Amateur Achievement
Award on citizen scientist Dan Caselden
for his " outstanding participation in the
Backyard Worlds citizen science projects. "
Like previous recipients of the award,
Caselden is not a professional astronomer
- he's a computer security researcher.
But in 2017 he stumbled upon Backyard
Worlds: Planet 9, a NASA-led citizenscience
project dedicated to searching for
new brown dwarfs near the Sun as well
as the elusive Planet 9. Along with his colleague
Paul Westin, he ended up building
an interactive browser tool that could efficiently
visualize images from the Wide-field
Infrared Survey Explorer, precipitating a
rise in the rate of brown dwarf discoveries.
One of Caselden's own discoveries resulted
in the JWST observations described
on page 10.
¢DIANA HANNIKAINEN
Nominate an amateur astronomer at
https://is.gd/ChamblissAward.
Another Giant Star Dims
Betelgeuse isn't the only giant star to
undergo a " Great Dimming " (S&T: Mar.
2021, p. 14). In late 2022, the variable star
RW Cephei - a yellow hypergiant and
one of the largest stars in the Milky Way
Galaxy (see page 77) - experienced a
similar event. A huge surface mass ejection
might have precipitated its sudden fade,
according to Narsireddy Anugu (Georgia
State University). When several astronomers,
including members of the American
Association of Variable Star Observers,
noted that RW Cep had faded to about a
third of its normal brightness, Anugu led
a team that followed up with the Center
for High Angular Resolution Astronomy's
six-telescope array on Mount Wilson, California.
They imaged RW Cep in December
2022 and again in July 2023, when the star
had almost returned to its normal brightness.
The images, presented at the 243rd
meeting of the American Astronomical
Society and published in the Aug. 1, 2023
Astronomical Journal, resemble those
taken of Betelgeuse about four years ago.
In the case of RW Cephei, dust appears to
block the western part of the star's face.
¢GOVERT SCHILLING
See the change: https://is.gd/RWCep
sk yand tele scope .o r g * MAY 2024 11
V. PANDYA / COLUMBIA UNIVERSITY (8)
https://www.is.gd/ChamblissAward https://www.is.gd/RWCep http://skyandtelescope.org
Sky & Telescope - May 2024

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