5
other
strange
stars
timescouldjustaswellhavebeenproducedbya
randomnumbergenerator.”
Theextremeconsistencyofthedips– insize
andshapeifnotintiming– meansthata dustring
isunlikelytobetheculprit.Insteadtheyappearto
beproducedbysomethinglargeandsolid,butit’s
unclearexactlywhat.Theshortdurationofthedips
meantheobjectsaretravellingquickly,andhence
inrelativelytightorbits.Theobservationscouldbe
explainediftherearea lotofplanets,allroughlythe
samesize,travellingonsimilarbutslightlydifferent
orbits– butthathardlyseemslikely.Ontheother
hand,‘multiplesimilar-sizedobjects’doessounda
lotlikea Dysonsphereinthemaking.
It’saneasyconclusiontojumpto.AsVanderburg
pointsout:“Whenpeopleinourcommunityhear
aboutsomethinglikethis,therunningjokeis
it might be aliens.” Yet HD 139139 is as good a
contender as anything astronomers have seen to
date. As Hugh Osborn, a specialist in transits at the
Marseille Laboratory of Astrophysics, said: “The
coherent dips in this system look more like solid
structures than the incoherent wandering of f luxduringtheeclipsesofTabby’sStar.”Nevertheless,he
remainsscepticalofthealienexplanation:“Tome,
itmakesfarmoresensethatthissystemissome
previouslyunknownnaturalphenomenon.”
Justwhatthat‘naturalphenomenon’isremains
tobeseen.Onepossibility,favouredbyOsborn,is
thattheHD 139139 systemcontainsatleasttwo
otherstarsinadditiontothetwothatcanbeseen.
Theextremecomplexityofa quadruplesystem
mightaccountfortheseeminglyrandomdipsthat
areobserved.
VanderburgagreesthatHD 139139 isunlikelyto
beanalienmegastructure:“Inastronomywehave
a longhistoryofnotunderstandingsomething,
thinkingit’saliens,andlaterfindingoutit’s
somethingelse.Theoddsareprettygoodthatit’s
goingtobeanotheroneofthose.”
But astronomers have only turned their attention
to HD 139139 in the last few months. It’s going to
require a lot more work to establish just how weird
or inexplicable it is. As Boyajian said: “This is one of
those systems where it’s probably not going to be
figured out without more data.”Vega:a squashedstar
Vegaisoneofthebrighteststars
inthenightsky– just 25 lightyears
awayandtwicethemassofthe
Sun.Bizarrelyitspinssorapidlyit’s
squishedoutattheequator.Mira:a starwitha tail
Mira– Latinformiraculous– was
oneofthefirstknownvariable
stars.Butitdeservesthetagfor
anotherreason– UVobservations
showithasa long,comet-liketail.VFTS352:mergingstars
Twostarsthatarevirtuallyidentical
twins,orbitingsoclosetoeach
otherthattheiratmospheres
overlap.It’slikelytheywillendup
mergingintoa singlestar.ARScorpii:
thewhitedwarfpulsar
Mostpulsarsarerotatingneutron
stars,butthisoneisa super-dense
whitedwarforbitedbya larger,but
lessmassive,reddwarf.HD140283:theagedstar
This is the oldest known star, with
an estimated age of 13.7 to 15.2
billion years. It’s probably the lower
estimate, because the age of the
universe is only 13.8 billion years!TIME
BRIGHTNESS
LIGHTCURVE
STAR
PLANET
Below:
A megastructure
could also be a
‘ring world’
around a star,
rather than
a sphere©Alamy
©Alamy©ESA©NASA©ESOThe weirdest star