Jupiter moons captured in rare triple transit
There was no dramatic entry. No high-risk maneuvers or
nail-biting rocket firing. If NASA’s Dawn spacecraft missed
on its slow crawl into orbit around the dwarf planet Ceres
early on March 6, engineers would have just tweaked the
weak thrust of the ion engines and tried again. Instead,
mission managers say the real drama will be the science
unveiled as NASA chronicles the history of the largest
unexplored body in the inner solar system.
“Since its discovery in 1801, Ceres was known as a
planet, then an asteroid, and later a dwarf planet,” said
Dawn Chief Engineer Marc Rayman on the 6th. “Now,
after a journey of 3.1 billion miles (4.9 billion kilometers)
and 7.5 years, Dawn calls Ceres home.”
Ceres — the largest member of the main asteroid belt
— is Dawn’s second target. The spacecraft spent 14
months exploring Vesta, the second-largest asteroid.
Together, the pair make up 40 percent of the belt’s mass.
The rest of the belt represents a multi-billion-year
record of collisions; however, astronomers believe these
two icy bodies are protoplanets — the fossilized seeds of
planets that might have been. Dawn’s images of Ceres
already imply material moved from the interior onto the
surface relatively recently. Vesta is covered in craters, but
Ceres has large regions where the surface is smooth.
Its density implies a mix of rock and ice, but the world’s
exact makeup is a mystery Dawn hopes to explain. The
European Space Agency’s Herschel spacecraft found
evidence of water near the dwarf planet last year, so NASA
is eagerly seeking plumes streaming off the surface. And
strange bright spots, seen only on Ceres, might have
already delivered. In talks given at March’s Lunar and
Planetary Science Conference in Houston, Dawn scientists
said the spots might be the very ice volcanoes they’d hoped
to find, giving Dawn success upon arrival. — Eric Betz
Lunar hydrogen deposits —
possibly a sign of water — are
more abundant on south polar-
facing crater slopes, NASA’s
Lunar Reconnaissance Orbiter
found. The deposits might one
day supply water, fuel, and air.
- MAGNETIC STORMS
NASA launched its four
spacecraft in March to study
magnetic fields connecting and
disconnecting around Earth.
Such explosive energy releases
are involved in technology-
disrupting space weather.
A study of planetary nebulae —
a Sun-like star’s final stage —
found “water fountains,”
explosions that occur as red
giants use up their nuclear fuel.
It shows some suns have sur-
prising last gasp eruptions.
DEEP-FRIED ICE CREAM
Lab tests on ice and organics
show comet surfaces get hard
and crystalize on approach to
the Sun as carbon-containing
molecules are ejected — sort of
like deep-fried ice cream.
The European Space Agency
launched a new spaceplane to
advance reusable transport
capabilities. The craft climbed
to 75 miles (120km) and reen-
tered the atmosphere, splash-
ing down in the Pacific Ocean.
Visual effects from the movie
Interstellar led to a February
paper in Classical and Quantum
Gravity. The code mapped light
beams moving through a black
hole’s space-time, showing
how they would be bent in
front of a filmmaker’s camera.
The Very Large Telescope’s new
instrument, SPHERE, failed to
find a suspected brown dwarf
around V471 Tauri, a strange
binary. SPHERE’s first science
has astronomers after a new
theory of the odd behavior.
Brazilian astronomers found
new star clusters at our galaxy’s
edge — far from the inner disk
where most form. The group
suspects a supernova booted
the star-forming dust and gas,
or it was stripped as our galaxy
skimmed a neighbor. — E. B.
TWINKLE, TWINKLE. British scientists announced plans for a small satellite named “Twinkle,” which will analyze the
atmospheres of thousands of known exoplanets, searching for spectral fingerprints of gases like water and methane.
NASA visits the
NASA/ESA/THE HUBBLE HERITAGE TEAM (STS
CERES SUCCESS. NASA’s Dawn spacecraft reached Ceres in
March, but it approached from the far side, leaving scientists in the
dark until mid-April. NASA/JPL-CALTECH/UCLA/MPS/DLR/IDA; ASTRONOMY: ROEN KELLY
SHADOW PLAY. On January 24, the Hubble Space Telescope captured an event only seen once or twice a decade: three of Jupiter’s
moons crossing the giant planet’s face and casting their shadows on its banded surface. In the image at left, showing the beginning of
the triple-moon transit, brownish Callisto and orange-yellow Io are visible, along with their shadows and that of Europa. Some 42 min-
utes later (right image), yellow-white Europa has entered the scene at lower left, while Io no longer casts its shadow on Jupiter. — K. F.
The breakneck speed of star US 708, fast
enough to launch it out of the Milky Way.
Are these spots icy