ASTRONEWS
0
500
1,
1,
2,
2,
0
30
60
90
120
Kepler
Telescope
Lunar
Reconnaissance
OrbiterHeliosphericSolar and
Observatory
Chandra X-ray Observatory
OSIRIS-REx
Spitzer SpaceTelescope
Mars
Reconnaissance
Orbiter
Dawn Juno
New Horizons
Voyager 2Voyager 1
2.
Seconds
Minutes
12
54
120
17 26 41 44
107
660
1,
2,
16
HOW LONG DOES IT TAKE TO TALK
TO A SPACECRAFT?
HOT STUFF. The Mars Reconnaissance Orbiter spotted evidence of hydrothermal vents on a martian lake bed
that once held 10 times the amount of water in the Great Lakes.
The Saturn Nebula, located 5,
light-years away in the constella-
tion Aquarius the Water-bearer, is
a complex planetary nebula that
contains many intriguing mor-
phological features. This is why an
international team of astronomers
used the Multi Unit Spectroscopic
Explorer (MUSE) to peer inside the
nebula’s dazzling clouds, produc-
ing the first detailed optical map
of a planetary nebula.
MUSE not only creates a two-
dimensional image of its target,
but also gathers spectral data for
each point in the image. With this
spectral information, the research-
ers can then filter the image by
color, revealing clues about the
object’s morphology and chemical
composition. In the Saturn Nebula,
the team found a plethora of
intricate structures, including a
thin elliptical inner shell, a foot-
ball-shaped outer shell, a spherical
halo, and two prominent exten-
sions called ansae (from the Latin
word for “handles”).
Most intriguingly, the research-
ers also found evidence of a mys-
terious wave-like structure within
the dust of the nebula. They dis-
covered that just outside the rim
of the inner shell, there is a nota-
ble drop in the amount of material,
indicating it may be destroyed as
the giant, expanding shock wave
of the inner shell travels outward.
By mapping the complicated
structures within planetary nebu-
lae, scientists hope to reveal the
role gas and dust plays in the lives
(and deaths) of the low-mass stars
that create them. — J.P.
Saturn Nebula’s strange structures
Messier catalog reboot
Voyager 1 left the solar system August 25, 2012, at a
distance of 11.25 billion miles (18 billion km) from Earth.
ROUND TRIP. Light — including the radio
waves used to communicate with spacecraft
— has a finite speed, meaning it takes time
to travel through space. When operators talk
to spacecraft, there is a time delay both for
outgoing and incoming signals. “Round-trip
light time” is the total time it takes for a signal
from Earth to reach a spacecraft and return
to its starting point. This time is affected by
several factors, including the positions of the
planets in their orbits around the Sun and the
trajectory of the spacecraft. — A.K.
FAST
FAC T AS OF OCTOBER 2017
ASTRONOMY
: ROEN KELLY
BEYOND THE VEIL. Planetary nebulae form when an aging star sheds its outer
layers, creating expanding shells of material. Inside, the star’s remnant core can still
be seen. The Saturn Nebula itself is about 6,000 years old. ESO/J. WALSH
STELLAR SPIRE. Stretching nearly 10 light-years,
this tall, dense pillar of cold gas and dust within the
Eagle Nebula (M16) is undergoing erosion by ultravio-
let radiation from hot, young stars seen in the top half
of the image. In October, NASA published this photo as
part of the Hubble Space Telescope’s “reboot” of the
Messier catalog, releasing images taken by HST of the
catalog’s 110 deep-sky objects. Compiled by French
astronomer Charles Messier almost 250 years ago, the
list was created to avoid these objects while comet
hunting. Today amateur astronomers rely on it for
visually stunning and easily locatable targets. — J.P.
NASA/ESA/STS
CI/AURA