The next supernova
2 Athomeinits
environment
Thedesignoftheobservatory
takesadvantageofthemountain’s
naturaltopography.Itsorientation
wasselectedafterextensive
weathertestingandsimulationsto
minimiseairdisturbance.3 Keepingthe
mirrorcool
Toprotecttheoptical
mirror,theheated
operationspacesare
locatedbelowthe
servicelevelwith
theheat-generating
equipmentbelow
that,farthestfrom
thetelescope.6 On-sitemaintenance
Toensuremaximumimaging
time,theobservatoryhasitsown
dedicatedcleaningandcoating
areawherethemirrorsarewashed
andrecoatedduringoperations.Gettingbrighter
Betweennowand100,000years’time
AstronomerswillknowBetelgeusehasexploded
beforeweseeit.Thelightoftheexplosionwillbe
sloweddownasitpassesthroughgassurrounding
thedyingstar.Ghostlyparticlescalledneutrinos
willpassstraightthroughandbeatthelighthere.Atitsbrightest
Firstweekofbrightening
Betelgeusewilltaketimetorampuptomaximum
brightness– thisusuallytakesabouta weekortwo.
Astronomerscanestimatethisbylookingathow
thelightfromothersimilarsupernovaevariesinthe
daysandweeksafterdenotation.Fadingaway
Afewmonthsafterpeakbrightness
ThelightcurvesfromotherTypeIIsupernovae
showthatthefadingprocesshappensintwo
stages.Firstitdropsinbrightnessbya factoroften
overa coupleofweeks,thenitsbrightnessplateaus
fora monthortwobeforetailingofffurther.student developing these models at Michigan State
University. This is because a lot of the important
physics that happens in the final stages of a star’s
life takes place deep within its core. And it takes
days, weeks or even years for any evidence to
affect the surface. “By contrast, the shock wave of
a supernova can blast its way out of the star very
rapidly, so will overtake most of the indications we’d
be looking for,” says Stanway.
Uncertainty hasn’t stopped speculation. Guinan
recently returned from the American Astronomical
Society meeting in Hawaii. Many delegates wanted
to speak to him about his notices on Betelgeuse and
what they thought you might see if it was about
to go supernova. “Some of them thought nothing.
It would just happen. And then there were a few
that thought there would be dimming, and then six
months later it would take off.”
In the meantime, teams continue searching
for ‘warning signs’, looking back through old
observation plates to find stellar sources of later-
observed supernovae. However, because these
events come out of the blue, there is never an
opportunity to organise detailed surveys in the
lead up. This leaves astronomers with at best a
single image, which alone cannot reveal unusual
variability or behaviour.
Others are looking outside optical light for clues.
Type II supernovae are accompanied by huge
amounts of ‘ghostly’ non-interacting neutrino
particles that can pass seamlessly outwards through
the star’s atmosphere. These are f lung into space
long before we expect anything to have changed
on the star’s surface, as the light struggles to make
its way out of these giant stars. When supernova
1987a exploded, Earth-based instruments detected
a small spike of a dozen or so neutrinos. Betelgeuse
is so near you could get 20,000 or 30,000 neutrino
detections, says Guinan.
“We might start detecting neutrinos weeks or
even months before the supernova explosion, andHow Betelgeuse’s supernova will look from Earth
Left: Neutrino
detectors like
the Super-
Kamiokande
in Japan
could spot
early signs
of a nearby
supernovaSource: Wikipedia © LSST Project/J. Andrew© Kamioka Observatory, ICRR, University of Tokyo