Australian Sky & Telescope - 02.2019 - 03.2019

24 AUSTRALIAN SKY & TELESCOPE February | March 2019

WBUILDING THE CENSUSIn 1995, the Yale Parallax Catalog contained

fewerthan200starswithin10pcofEarth.Thatnumberjumpedslightlyin

1997withtheHipparcosmissiondata,andsince2002thecounthasrisen

by at least one star each year. Red points mark years in which RECONS

added the number of systems indicated with red digits.

ROSS 128bThis artist’s

concept shows a potentially

habitable exoplanet that lies

11 light-years away — one

of the closest such worlds

known.

beagalaxy.Oncetheteamsubtractsthe378starsalready

known, Gaia might add just a few objects at the boundary, he

estimates.

After the Gaia data have been double-checked, Henry will

turnhisattentionbacktothewide25and100pcsurveys.

“We have probably identified about 90% of the nearest 500

stars,butonlyabout60%ofthenearest5,000stars,”hesays.

Mappingthestarsisonlythebeginning.Astronomers

still do not know much about the magnetic cycles of some of

thesestars,whichcanaffecttheiractivityandanyplanets’

habitability. The upcoming Large Synoptic Survey Telescope,

whichwillscrutinisethesouthernskyfromChile,willbe

abletohelpherebywatchingthesamestarsformanyyears.A

separate RECONS project will explore the orangeKstars, which

areintheclassofstarsbetweenourSunandthereddwarfs.

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

starsandlargerstars.Yetcomparedtoallthestarsinits

neighbourhood, it’s remarkable: Its temperature, luminosity,

and mass put it in the 90th percentile — far hotter, brighter,

andheftierthanthemorecommonlittlestars.Intheend,

it’salljustamatterofperspective.

„KEITH COOPERis the editor of bothAstronomy Now

magazine andAstrobiology Magazine(astrobio.net). His book

The Contact Paradox: Challenging Assumptions in the Search

for Extraterrestrial Intelligencewill be published in October.

150

1995 2000 2005 2010 2015 2020

350

300

250

200

1

6

2 1

1

14

Systems Within 10 Parsecs

Number of star systems

19

GRAPH: LEAH TISCIONE

/ S&T

, SOURCE T. J. HENRY ET AL. /

ASTRONOMICAL JOURNAL

2018; ROSS 128: ESO / M. KORNMESSER

THE NEAREST STARS