The world’s best-selling astronomy magazine

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