http://www.skyandtelescope.com.au 9KUIPER BELT: NASA / JHU APL / SWRI / ALEX PARKER
Beyond Pluto – is New Horizons’
next target a binary body?
THE QUEST IS ON to learn everything possible about the
Kuiper Belt object (KBO) designated 2014 MU 69 before
New Horizons flies by at close range on January 1, 2019.
And that effort got a huge boost when the notoriously dim
(27th-magnitude) object passed in front of a dim star in
Sagittarius on July 17.
The occultation campaign’s first two events, on June 3 and
July 10, didn’t see any blink-outs). But on July 17, five of the 23
observing teams recorded brief occultations of up to 1 second.
These teams, which included some experienced amateur
observers, were arrayed about 4½ km apart along a
‘picket fence’ in remote parts of south-central Argentina,
perpendicular to the occultation’s predicted path. Given the
separations of the five successful teams, 2014 MU 69 has to be
20 to 30 km long. That’s smaller than originally thought, so
the surface material must be somewhat more reflective than
the surfaces of the Kuiper Belt’s usual denizens.
However, the occultation timings don’t match the
silhouette expected for a spherical object. Instead, campaign
leader Marc Buie (Southwest Research Institute) reports, it
could be highly elongated (like a skinny eggplant) or it might
be a pair of objects, either touching or twirling around each
other at very close range.
Corroborating observations come from Hubble Space
Telescope observations carried out by Susan Benecchi
(Planetary Science Institute) between June 25 and July 4. She
reports that 2014 MU 69 showed little variation in brightness
during the first observing run but that the changes became
more pronounced later on. Benecchi says this is consistent
with a double object; Buie prefers that option, too.
Meanwhile, negative results from the first two occultations
(especially observations from NASA’s SOFIA flying
observatory on July 10) build confidence that New Horizons’
forthcoming target isn’t ringed by impact debris, which would
have posed a threat to the spacecraft as it whizzes by the rock
at 13.7 km per second. ■ J. KELL Y BEATTYWWhat’s the real
shape of 2014
MU 69 , a Kuiper Belt
object that’s 43.
astronomical units
(6.5 billion km) from
the Sun? New studies
suggest it’s either
highly elongated and
up to 30 km long
(top) or a binary body
whose halves are
each about 15 to 20
km across (bottom).Saturn’s mysterious magnetic field
Saturn’s magnetic axis aligns surprisingly well with its rotational
axis. As NASA’s Cassini conducted its dramatic Grand Finale
dives between Saturn and its rings, the magnetometer aboard
measured the planet’s magnetic field. Its tilt is much smaller
than 0.06°, which was the lower limit obtained prior to the
Grand Finale. Magnetic and rotational axes are misaligned in
other magnetically active planets; astronomers think such tilts
help sustain those planets’ internal dynamos. Saturn’s good
alignment suggests we don’t understand its internal structure
as well as we thought we did. The wobble of a misaligned
magnetic field would also have revealed the rotation of the
planet’s core, and without that misalignment, scientists are still
unsure of the true length of Saturn’s day. y David DickinsonBSprites in space
Six of tiny spacecraft, dubbed Sprites, have been sent into orbit.
Each slightly larger than a postage stamp, they weigh 4 grams
and have solar panels, sensors and communication equipment.
Two of the Sprites were mounted on larger satellites named
Venta and Max Valier; Max Valier carried another four Sprites
in its cargo container for deployment as independent satellites.
While communication with Max Valier failed, halting the release
of its Sprites, ground stations made contact with the Sprite
mounted on Venta. The achievement is a small milestone for
Breakthrough Starshot, which helped create the satellites as a
test for building future interstellar craft. y David DickinsonBVisit our website https://britastro.org/digital and join today!Be a part of something
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