RESEARCHERSof the IndianInsti-
tute of TechnologyHyderabad(IITH),
havefoundthat peoplelivingin a city
withactivecoal-fired powerplants
andconsuminglocalaquaticpro-
ducemay havehigherbodylevelsof
mercury.The conclusionsare based
on a studyof amountsof mercuryin
the hair of over600 peoplein three
citiesin India.Thisstudyhas been
reportedin “Journal of Exposure
Science and Environmental
Epidemiology”.
Mercuryis a neurotoxinthatisestimatedto be the largestemitters
of mercuryto the atmosphere.”The
totalmercuryemissionsin Indiaare
estimatedto becomearound 540
tonnesin 2020.“Hairis an excellent
indicatorof mercuryin the body.
Hairconcentratesmercuryand its
samplingis non-invasive,makingit
easyto bothmeasure and correlate
to the amountof mercuryin the
body,”Qureshiadded.Thesurvey
showedthatnearly5.5 per centof
the people tested had mercury
levelsabovethe currentreference
set by the EnvironmentalProtection
Agency(EPA),UnitedStates.used in industry and consumer
productsand existsas a naturalim-
purityin ores.It is non-degradable
and circulates widelywithin and
betweenecosystems.Mercuryhas
adverseeffectson lungsandkid-
neys,and heartdiseases.
“In moderntimes,”pointedout
Asif Qureshiof IITH who headedthe
researchwork, “thenon-occupa-
tionalexposure of humansto mer-
curycomesfromfood,especially
fish, and rice grownin contaminated
fields.Coal-fired powerplantsareHighlevelsofmercuryin urbanIndians
ASTRONOMERSnow havea
fairly good idea of the
chaoticand crowdedneigh-
bourhoodsurroundingthe
supermassive blackholeat
the centreof the MilkyWay,
thatis about 26,000light
yearsfromthe earth(one
lightyearis about9.5 billion
km).SagittariusA, the su-
permassiveblackhole,is 4
milliontimesthe massof
the sun.The regionaround
the blackholeis brimming
withrovingstars,interstel-
lar dustclouds,and a large
reservoirof bothphenom-
enallyhot andcomparat-
ivelycoldergases.These
gasesaccumulate in a huge
“accretiondisk”,whichor-
bits the black hole, the
centreof very largegravita-
tionalattraction.As the gas
spiralsin, it becomeshot
and emitsenergyat a vari-
ety of wavelengths,includ-
ing X-rayand radiowaves.
Theseemissionsextenda
few tenthsof a lightyear
fromthe blackhole’sevent
horizon,the boundarysur-
faceof a blackholebeyond
whichnothingcanescape
fromwithinthe blackhole.
fromthe blackhole.How-
ever,imagescaptured so
far of this accretinggas,
which forms a roughly
sphericalflow, showedno
obviousrotation.
In additionto thishot
glowinggas,previousob-
servations havedetecteda
vaststoreof comparatively
coolerhydrogengas (about
10,000°C)withina few light
yearsof the blackhole.
Withits highsensitivity
and powerfulabilityto seefine details, theAtacama
LargeMillimetre/submilli-
metreArray(ALMA),Chile,
was ableto detectthis faint
radio signaland produce
thefirst-everimageof the
coolergas disk at only about
a hundredthof a lightyear
away(or about1,000times
the distancefromthe earth
to the sun)fromthe super-
massiveblackhole.It has
been estimated that the
amountof hydrogenin this
cool disk is aboutone-tenth
the massof Jupiter,or one
ten-thousandth of the mass
of the sun.
“We werethefirst to im-
agethiselusivediskand
study its rotation,” said
ElenaMurchikovaof the In-
stitutefor AdvancedStudy,
Princeton,and leadauthor
of the paper,publishedin
the latestissueof “Nature”.
“We are also probingaccre-
tion ontothe blackhole.
Thisis importantbecause
thisis our closestsuper-
massiveblackhole.Even
so, we still haveno goodun-
derstandingof howits ac-
cretion works. We hope
thesenewALMAobserva-
tionswill helpthe blackhole
give up someof its secrets.”Untilnow,however,as-
tronomershavebeenable
to imageonlythe tenuous,
hot portionof thisflow of
accretinggas,whosetem-
peratureis estimatedto be
10 million°C (about two-
thirds the temperature
foundat the coreof the sun).
At this temperature, the gas
glowsfiercelyin X-raylight,
allowingit to be studiedby
space-based X-ray tele-
scopes, downto scale of
abouta tenthof a lightyearTHE IMAGEof the disk of cool hydrogengasflowing
aroundthe supermassiveblack hole at the centre of the
Milky Way,as produced by the ALMA.ALMA(ESO/NAOJ/NRAO), E.M.MURCHIKOVAETALSupermassiveblackholeandbeyond