BBC Focus - 04.2020_

FE ATURE WHAT HUBBLE TAUGHT US

Hubblehasfundamentallyaltered

our view on the largest of scales

CONFIRMINGPRIMORDIALHELIUM

In 1995,Hubblefinallyconfirmedthe

presenceofprimordialhelium.Theory

hadpredictedthataftertheBigBang,

thecoolingUniverseformedboth

heliumandhydrogen,buttheformer

had never been seen before.

GAMMARAYBURSTS

GRBsarethemostpowerful

explosionsin theknownUniverse,but

theiroriginsarea mystery.In 2019,

Hubblefounda GRBthathadcome

fromthedenseenvironmentofa

brightgalaxyaroundfivebillion

light-yearsaway– a cluetothe

conditions that might cause a GRB.

UNIVERSE MOMENTS

HUBBLE’S TOP 3

5 l ig ht,”saysWiseman.“Byexaminingthegravitationallensing

ofthegalaxyclusterswecantell something about how mass is

distributedintheseclusters.”

Mostofthismassisdarkmatter.Bylookingathowmuch

galaxiesaredistorted,astronomersareabletomapouthowthe

mysterious substance is distributed throughout the Universe.

SPOTTINGBLACKHOLES

AnotherseeminglyinvisibleobjectthatHubblehashelped

illuminatearesupermassiveblackholes.Thesedensebodies

areseveralbilliontimesmoremassivethanourSunandare

thoughttolieat theheartofmostgalaxies.BeforeHubble,these

blackholeswereentirelytheoretical.Theonlyevidenceoftheir

existencewereradioobservationsofdistantgalaxiesknownas

quasars,whichcontainedobjectsaroundthesizeoftheSolar

Systembutwhichshonebrighterthananyotherknownthing

intheUniverse.Hubblewasabletodeterminethattheradio

emissionswerecomingfromthecentresofthegalaxiesthat

heldthem,mostlikelyfromextremelyhotgasthatwasbeing

intenselyheatedasit swirledarounda giantblackhole.

In1997,theSpaceTelescopeImagingSpectrographwasinstalled

onHubble.Thisinstrumentwasmuchbetteratlookingatthe

regionclosetoa galaxy’scentre,andit couldmakeouttherapid

movementofstarscaughtinorbitclosetoa blackhole.The

instrumentsoonfoundthem,definitively proving the existence

ofsupermassiveblackholes.

Forthelast 30 years,Hubblehashelpedastronomersto pullout

photonsfromthedeepestdepthsof space,andevenilluminated

placesinourcosmoswherenolight shines, helping to reveal

the Universe’s darkest secrets.

ABOVEThis

image,takenby

Hubble,is a good

exampleof

gravitational

lensing.The

massivegalaxy

clusterinthe

centreofthe

imageis about

4.6billion

light-yearsaway.

It is surrounded

byfourarcs

(threeinthetop

right,oneinthe

bottomleft).

Withinthese

narrowarcsare

atleast 12 copies

ofa galaxy

nicknamedthe

SunburstArc,

locatednearly 11

billionlight-years

away.Itslightis

beingdistorted

intomultiple

imagesby

gravitational

lensing

byDRELIZABETHPEARSON(@E z z y P)

Elizabethis a spacejournalistandnews editor

atBBC Sky At Night magazine. NASA/ESA/G.

ILLINGWORTH/D.

MAGEE,

AND

P.OESCH

(UNIVERSITY

OF

CALIFORNIA/SANTA

CRUZ)/R.

BOUWENS

(LEIDEN

UNIVERSITY)

AND

THE

HUDF09

TEAM,

MALEKAS85/ISTOCK/GET T Y IMAGES, NASA/ESA AND M. KORNMESSER, ESA/HUBBLE/NASA/RIVERA-THORSEN ET AL, NASA/MICHAEL SOLURI, NASA/W. HRYBYK

EXTREMEDEEPFIELD

In 2012,theHubbleteamreleased

theeXtremeDeepField.Theimage

coveredjust2x2.3arcminutes,around

1/32,000,000thsofthesky,yethad

anexposuretimeofaround 23 days.It

looksbackthrough13.2billionyears,

showingonegalaxywhen it was just

450 million years old.