ASTRONEWS
WWW.ASTRONOMY.COM 17The estimated maximum number of undiscovered
near-Earth asteroids more than 0.6 mile across.SELFIE STICK. NASA’s James Webb Space Telescope (JWST) passed a critical test last October. In what appears
to be the ultimate work selfie, Ball Aerospace optical engineer Larkin Carey is reflected in JWST’s convex second-
ary mirror as he tests its alignment. Such tests ensure that light from distant objects will travel the correct path as
it bounces off the telescope’s primary, secondary, and tertiary mirrors to focus on its instruments. Carey and his
equipment — including his camera — were tethered to a “diving board” suspended between the two mirrors to
prevent damaging the telescope’s primary mirror or Aft Optics Subsystem below him, should something slip off the
board. The procedure for taking the picture was practiced several times before Carey and the board were extended
for the final shot. — A.K.Webb Telescope sits for a unique portrait
Long ago, something large
smashed into Haumea.
Following the catastrophe,
the world could not fall back
into a circular shape because of
its small size. Instead, it is now
shaped like an egg or grain of
rice. The collision also left
behind a few small moons and
a trail of debris. And, as a paper
published October 11 in Nature
demonstrates, it left behind a
ring of material, too.
This isn’t the first small solar
system body discovered to
boast a ring: 10199 Chariklo, the
largest of a class of objects
called centaurs hiding out
between Saturn and Uranus,
has a ring, as does fellow cen-
taur 2060 Chiron. But both
those worlds are small, about
120 to 160 miles (200 to 250
kilometers) in diameter.
Haumea, on the other hand, is
roughly six times bigger than
Chariklo, making it still way
smaller than our Moon, but thefifth-largest object in the solar
system to have a ring, after
Jupiter, Saturn, Uranus, and
Neptune.
A team led by Instituto de
Astrofísica de Andalucía made
the discovery while watching as
Haumea passed in front of the
star URAT1 533-182543 in a
transit event called an occulta-
tion. The dwarf planet’s thinring is about 44 miles (70 km)
wide. Observing the occulta-
tion also helped the team
determine that Haumea does
not host an atmosphere.
The paper further speculates
that rings like this could be
more common in the outer
solar system, which contains
much of the debris from our
system’s formation. — J.W.Ring around the dwarf planet
The solar corona — the Sun’s outermost
layer of hazy plasma that is visible during
a total solar eclipse — has baffled astron-
omers for nearly 150 years. Whereas the
Sun’s surface (the photosphere) reaches
temperatures of only around 10,
degrees Fahrenheit (5,500 degrees
Celsius), the corona can reach tens of mil-
lions of degrees Fahrenheit.
In a study published October 9 in
Nature Astronomy, a team of astronomers
presented evidence that small explosions
called nanoflares could be the mecha-
nism responsible for the inexplicably
extreme temperatures.
To investigate the mystery, the team
launched a sounding rocket, called the
Focusing Optics X-ray Solar Imager
(FOXSI), into space for 15 minutes so that
the payload of seven X-ray telescopes
could observe the Sun. During the flight,
the telescopes observed X-ray light from
one region of the Sun’s corona corre-
sponding to temperatures of more than
18 million F (10 million C).
Because the team did not observe any
full-size solar flares in this region, the
researchers knew that regular flares were
not responsible for the heating. Instead,
they proposed a mechanism whereby
many small, intense nanoflares — which
are about a million times weaker than
traditional solar flares — crop up and dis-
sipate quickly, creating pockets of
extremely hot plasma.
Unfortunately, detecting these rela-
tively faint nanoflares is exceptionally
challenging and beyond our current
capabilities. But until the next FOXSI
flight, scheduled for August, the
researchers will incorporate nanoflares
into coronal models, hoping to bring the-
ory in line with observations. — J.P.Why is the Sun’s
corona so hot?
40
DOUBLE TROUBLE. Astronomers working with data from the Chandra X-ray Observatory found a
number of binary supermassive black holes, which could help explain how these black holes grow.FIRST PLACE. Weirdly shaped Haumea, named for the Hawaiian goddess,
is the first dwarf planet in our solar system to boast a ring. IAA-CSIC/UHUBABY BLAST. The Sun’s surface, shown here
in X-ray, bubbles with activity as solar flares
burst forth, spewing fountains of plasma.BALL AEROSPACENASA/JPL-CALTECH/GSFC