Sky & Telescope - January 2019 - 40

The Nearest Stars
350

t BUILDING THE CENSUS In 1995, the Yale Parallax Catalog contained
fewer than 200 stars within 10 pc of Earth. That number jumped slightly
in 1997 with the Hipparcos mission data, and since 2002 the count has
risen by at least one star each year. Red points mark years in which
RECONS added the number of systems indicated with red digits.

Systems Within 10 Parsecs

Number of star systems

14
1

300

250

19

2

1

6
1
200

150

1995

2000

2005

Year

2010

2015

2020

team subtracts the 378 stars already known, Gaia might add
just a few objects at the boundary, he estimates.
After the Gaia data have been double-checked, Henry will
turn his attention back to the wide 25 and 100 pc surveys.
"We have probably identified about 90% of the nearest 500
stars, but only about 60% of the nearest 5,000 stars," he says.
Mapping the stars is only the beginning. Astronomers still
do not know much about the magnetic cycles of some of these

stars, which can affect their activity and any planets' habitability. The upcoming Large Synoptic Survey Telescope, which
will scrutinize the southern sky from Chile, will be able to
help here by watching the same stars for many years. A separate RECONS project will explore the orange K stars, which
are in the class of stars between our Sun and the red dwarfs.
Ultimately, learning about our nearest stars also helps
to put our solar system in context. We often refer to our
Sun as average, because it's partway between smaller stars
and larger stars. Yet compared to all the stars in its neighborhood, it's remarkable: Its temperature, luminosity, and
mass put it in the 90th percentile - far hotter, brighter, and
heftier than the more common little stars. In the end, it's all
just a matter of perspective.

¢ KEITH COOPER is the editor of both Astronomy Now magazine and Astrobiology Magazine (astrobio.net). His book The
Contact Paradox: Challenging Assumptions in the Search for
Extraterrestrial Intelligence will be published in October.

GR APH: LE AH TISCIONE / S&T, SOURCE T. J. HENRY E T A L. / ASTR ONOMICAL JOUR NAL 2018; ROSS 128: ESO / M. KOR NMESSER

ROSS 128b This artist's
concept shows a potentially habitable exoplanet
that lies 11 light-years
away - one of the closest such worlds known.

40

JA N UA RY 2 019 * SK Y & TELESCOPE



http://www.astrobio.net

Sky & Telescope - January 2019

Table of Contents for the Digital Edition of Sky & Telescope - January 2019

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