BBC Focus 02.2020

NASA’sTransitingExoplanetSurvey

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potentiallyhabitableplanetina star’s

‘Goldilockszone’,whereconditionsare

justrighttoallowtheexistenceofliquid

waterandthereforelife.

NamedTOI700d,theplanetis

thelatestina handfulofpotentially

habitableEarth-sizedworldsfound

throughouttheGalaxy.It is around 20

percentbiggerthanEarth,completesits

orbitevery 37 daysandreceives 86 per

centoftheenergyfromitsstarthatthe

SunprovidestoEarth.

It is theoutermostplanetfoundin

orbitaroundthestarTOI700,which

is a small,cool,dwarfstarlocatedjust

over 100 light-yearsfromEarthinthe

southernconstellationDorado.TOI

700 is roughly 40 percentoftheSun’s

massandsize,andabouthalfitssurface

temperature.

“TESSwasdesignedandlaunched

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orbitingnearbystars,”saidDrPaul

Hertz,astrophysicsdivisiondirectorat

NASAinWashington.“Planetsaround

nearbystarsareeasiesttofollowup

withlargertelescopesinspaceandon

Earth.DiscoveringTOI700dis a key

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planet’ssizeandhabitablezonestatus

withSpitzeris anotherwinforSpitzer

asit approachestheendofscience

operationsthisJanuary.”

TESSviewslargeswathesofthesky,

calledsectors,for 27 daysat a time.This

longperiodofobservationallowsthe

satellitetomonitorchangesina star’s

brightnesscausedbyanorbitingplanet

crossinginfrontofitsstarfromour

perspective,aneventcalleda ‘transit’.

WhiletheexactconditionsonTOI

700darea mystery,a teamofresearchers

at NASA’sGoddardSpaceFlightCenter

usedknowninformation,suchasthe

planet’ssizeandthetypeofstarit

orbits,togeneratea seriesofcomputer

modelsandmakepredictions.One

simulationrevealedanocean-covered

worldsurroundedbya dense,carbon-

dioxide-dominatedatmosphere,similar

towhatscientistssuspectsurrounded

Marswhenit wasyoung.Anothermodel

depictsTOI700dasa cloudless,all-land

versionofmodernEarth.

“It’sexcitingbecausenomatterwhat

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tolookcompletelydifferentfromwhat

wehavehereonEarth,”saidGabrielle

Englemann-Suissa,wholedthe

computer modelling team.

TESS has

found its

first planet

within the

Goldilocks

zone

SPACE

GET T Y IMAGES, ALAMY, NASA/GSFC

TheTransitingExoplanet

SurveySatellitespoed

theplanetjustover 100

light-years away

Artist’simpressionofthe

Earth-likeexoplanetTOI

700d,locatedjustover

100 light-years away