BBC Focus - 04.2020_

STELLAR SHOCKWAVE

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BUBBLENEBULA

AlsoknownasNGC7635,theBubbleNebula

wascreatedbya petulantstar,around 45 times

themassofourSun,throwingoutitsgas,or

stellarwind.Thegasis travellingataround

6.5millionkilometresperhour,andasthe

resultingcloudexpandsout,it slamsintothe

surroundinginterstellarmedium– thisis the

gaswhichfillsthespacebetweenthestars–

creatinga shockwave.Theadvancingwave

causestheregionsit passesthroughtoheatup

andglow,producingthebrightbubblethatgives

thisnebulaitsname.

Thebubbleis lopsided,however,withthestar

locatedinthetopleft.Theinterstellarmedium

inthisregionis muchcooler,andtherefore

denser,makingit harder for the gas to expand in

that direction. 2

HUBBLE’S HIDDEN GEMS FEATURE

DUST BUSTER

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PISMIS 24

Pismis 24 is justoneclusterof starsina largenebula,
NGC6357.Theentireregionis hometo manyyoung
andgrowingstars,akaprotostars.Thesegrowupin
thickdustclouds,whichhidethemfromtelescopes
thatcanonlyviewtheUniverseat visiblewavelengths.
“HubblecanbeusedforUV,visibleandsome
infraredobservations.Thesepanchromatic
capabilitiesareincrediblyusefulforstudying
everythingfromSolarSystemactivityto distant
galaxies,”explainsJenniferWiseman,seniorproject
scientistfortheHubbleSpaceTelescope.
Here,Hubblehasbeenabletopiercethroughthe
dust,creatinga windowintowhereinfantstarsare
born.It wasthoughtthemassof thecluster’sbrightest
star,Pismis24-1,wasaround 300 timesthatof the
Sun,makingit theheaviestintheGalaxy.However,
Hubble puts it at a far more modest 100 solar masses.