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6 ASTRONOMY • FEBRUARY 2018

BY DAVID J. EICHER

FROM THE EDITOR

Editor David J. Eicher

Art Director LuAnn Williams Belter

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T

his coming New Year’s

Eve is set to be one of

the most exciting in

many years, at least

for astronomers. And

I’m not speaking of any cel-

ebrations that will be taking

place in Times Square. At

this time and on January 1,

2019, the spacecraft that

famously unveiled Pluto

up close more than two years

ago will f ly even closer past a

mysterious Kuiper Belt

object. This will give plan-

etary scientists an important

new look at the outer

solar system.

Throughout

the journey of

New Horizons, which

launched in 2006,

Astronomy has been

privileged to have the

program’s leader,

Alan Stern, contribute

our stories about the

mission. And in this issue,

the tradition continues with

a story that previews the

next chapter.

As Alan details in his

story, the extended mission

to the Kuiper Belt began in

late 2015 when the craft used

its thrusters to maneuver

toward this primitive rocky

body, (486958) 2014 MU 69 ,

also known simply as MU69.

This classical Kuiper Belt

object is a primitive

target, thought to be

essentially unchanged

since the solar system’s

earliest days.

Astronomers using

the Hubble Space

Telescope discovered

MU69 in 2014 during a

survey specifically aimed at

choosing a New Horizons

target. Subsequent observa-

tions suggest this rock is a

binary, or contact binary,

probably consisting of two

lobes. The lobes most likely

measure about 12 and 11

miles across (20 and 18 kilo-

meters), and this object has

an orbital period around the

Sun of 296 years. It’s a dark

reddish object, as astrono-

mers would expect, and it is

probably covered with some

complex molecules that have

decomposed from long-term

exposure to solar radiation.

In 2017, members of the

New Horizons team

observed several occulta-

tions, events wherein MU

passed in front of stars, from

sites in South America,

Africa, and the Pacific

Ocean. The occultation

results confirmed that

MU69 has an unusual

shape — an extreme

prolate spheroid, or

likely a close or contact

binary, with two dis-

tinct lobes.

This will be a very

exciting moment for

solar system astron-

omy. New Horizons is

expected to pass a mere

2,175 miles (3,500 km) from

MU69, about four times

closer than the spacecraft

got to Pluto and Charon.

Get ready for another

major solar system adven-

ture. Life is good!

Yo u r s t r u l y,

David J. Eicher

Editor

New Horizons

into the

Kuiper Belt

Follow the Dave’s Universe blog:

http://www.Astronomy.com/davesuniverse

Follow Dave Eicher on Twitter: @deicherstar

Throughout the journey of

New Horizons, which launched

in 2006, Astronomy has been

privileged to have the program’s

leader, Alan Stern, contribute

our stories about the mission.

JHUAPL/SWRI