Australian Sky & Telescope — July 2017

38 AUSTRALIAN SKY & TELESCOPE July 2017

Several of TRAPPIST-1’s

worlds might have the

potential for liquid surface

water — or have had their

atmospheres torn off.

T

he star TRAPPIST-1 is an unassuming,M8reddwarf

star.Itlies39light-yearsawayinthedirectionof

Aquarius,shiningatameaslyapparentmagnitudeof

19.CloserinsizetoJupiterthantotheSun,thedwarfputs

outlessthanathousandthasmuchlightasourstar.

Lastyear,MichaëlGillon(UniversityofLiège,Belgium)

andcolleaguesannouncedthatatrioofsmallexoplanets

orbitsthispipsqueakstar.Theteamdetectedtheexoplanets

usingthetransittechnique,whichcatchesthetinydipin

starlightwhenaplanetpassesinfrontofitshoststarfromour

perspective. Now, after an intensive follow-up campaign, the

observershavediscoveredthatthereareactuallysevenplanets,

notthree.Allarelikelyrocky.AtleastthreelieinTRAPPIST-1’s

putativehabitablezone—theregionwhere,givenanEarth-like

composition, liquid water could be stable on the surface.

TALIEN SKYArtist’s concept of what the sky might look like from above

one of the seven known terrestrial planets in the TRAPPIST-1 system.

ESO / M. KORNMESSER

The

EXOPLANET NEWS by Camille M. Carlisle

magnificent seven