Sky and Telescope - January 2018 - 29

0h
+60°

22h

20h
18h
DRACO
Original
Kepler ﬁeld

CEPHEUS

16h

14h

12h

10h

HERCULES

LYRA

CYGNUS

LYNX

PEGASUS

-30°

LIP

VIRGO

OPHIUCHUS

19
19
12

LIB RA
TIC

9 11

CAPRICORNUS

CORVUS

CENTAURUS

TAURUS

18h

16h

0°

CANIS
MAJOR

CETUS

HYDRA

-30°

ERIDANUS
PHOENIX

VELA

CRUX

LUPUS

20h

PISC ES

ORION

PUPPIS

PAVO

LEPUS

SCORPIUS

22h

SAGITTARIUS

-60°
0h

13
1

1
10

7
17
6

1
2 15

+30°

ARIES

0
18
18

AQUILA

ANDROMEDA

GEMINI

B OÖTES
LEO

AQUARIUS

0h
+60°

PERSEUS
URSA
MAJOR

AUR IGA

+30°

CARINA

14h

12h

10h

-60°
0h

G REGG DINDER M A N / S&T, SOURCE: K EPLER & K 2 / N ASA A MES RESE A RCH CEN TER
K 2 PA PERS: LE A H TISCIONE / S&T, SOURCE: K EPLER & K 2 / N ASA A MES RESE A RCH CEN TER

p CAMPAIGN FIELDS Kepler originally stared continuously at a region of sky in Cygnus and Lyra (yellow grid field). Now confined to the ecliptic after
technical mishaps, the repurposed space telescope points at a different field every 80 or so days. Shown are completed K2 campaigns (yellow outlines) and those upcoming when we went to press (orange). Campaign 16, which begins in December 2017, is dedicated to searching for supernovae.

spacecraft without the ability to point itself precisely toward a
single spot in the sky. But NASA wasn't willing to give up on
the scope, even if it was a little shaky.
Engineers developed an alternative plan, in which the telescope uses radiation pressure from the Sun to stay stable. But
it can no longer stare at a single patch of sky as it did before.
Instead, Kepler is limited to observing campaigns that each
last roughly 80 days before the telescope has to reposition
itself. It is also conﬁned to observing near the ecliptic plane.
Both raise a list of pros and cons for Kepler's stellar astrophysics, but Jenkins argues that the new situation is the "best
worst thing that ever happened to Kepler."
For the most part Kepler has shed light on the evolution of
Sun-like stars - particularly ones that are as mature as the
Sun or older. But now that Kepler has the freedom to point

K2 Papers, By Science Topic
Exoplanet
discovery
Catalogs &
data analysis

18%
23%

Exoplanet
characterization

Supernovae & 4%
extragalactic 5%
Solar system
science
Stellar flares &
activity
Young
stars

4%
3%

Eclipsing Open
binaries clusters

4% Microlensing
6%
3%

along the ecliptic, it will have the opportunity to observe the
opposite side of the spectrum: young stars. That's because
regions of star formation (like those toward Taurus, Sagittarius, and Scorpius) dot the disk of our galaxy, which twice
crosses the ecliptic.
"It's an amazing second act for Kepler," Kawaler says.
K2 may also help solve some of the mysteries Kepler created, like those surrounding supernovae. In December 2017,
the telescope will start to monitor roughly 15,000 galaxies
with the hope of catching somewhere between 10 and 15
supernovae. Garnavich wants to use these supernovae to
determine - once and for all - what triggers them.
Not only will K2 help shed light on stellar evolution, but it
will also reveal surprising details about galactic evolution. By
using asteroseismology to map the masses, sizes, and ages of
hundreds of thousands of stars across the Milky Way, astronomers will better understand when stars started to form and
where. And that result will help them chart the development
of our galaxy in unprecedented detail.
Even with K2 well under way, scientists are still mining
the data from the original mission. It's the only data set that
gives four continuous years of brightness measurements,
which makes it "the best resource for doing this sort of science that we have at the moment," Huber says. "I believe
there is still more to be found in the Kepler data."

Asteroseismology

Galactic
archaeology
Classical pulsators
White dwarfs

n While writing this story, freelance science journalist SHANNON HALL witnessed two awesome - and life-changing
- celestial events: the total eclipse of the Sun and, later, the
northern lights.
sk yandtelescope.com * JA N UA RY 2 018

http://www.skyandtelescope.com/

Sky and Telescope - January 2018

Table of Contents for the Digital Edition of Sky and Telescope - January 2018