Page 117 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

WHAT TO SEE

As it explodes, Supernova REMARKABLE
1987a, bottom right, rivals
the brightness of the
Tarantula Nebula, top left REMNANTS
When massive stars explode, they throw off their outer layers at
blistering speeds. The rapidly expanding shells of gas and dust
create spectacular objects known as supernova remnants. These
stellar carcasses are some of the most intricate deep-sky objects.
Their beauty has been captured with the help of space telescopes
observing at many wavelengths of light, as shown below.

CRAB NEBULA
First observed by the English
astronomer John Bevis in 1731,
this famous remnant is the fi rst
object in the Messier Catalogue.
The 1054 supernova that
the star’s matter is blasted Even though these caused it was so bright that it
out into space, with a vast supernovae are often bright was visible during the daytime.
increase in brightness that enough to outshine entire Constellation: Taurus
Distance: 6,250 lightyears
can last from weeks to months. galaxies, only a tiny fraction
The exact story of a of the energy released is
supernova involves several visible light. Most of the VEIL NEBULA
stages. A massive star will energy is released in the The explosion that created this
relatively large remnant occurred
live for millions of years, form of subatomic particles.
almost 10,000 years ago. It
happily converting its main When the drama is over, what
was discovered by German-
fuel of hydrogen into helium, remains is the old, dead core born English astronomer
until the hydrogen runs of the star radiating away William Herschel in 1784.
low. With enough mass, the its heat. It’s now a compact Constellation: Cygnus
temperature and pressure in neutron star or, if the star is Distance: 2,000 lightyears
its core are high enough for more massive, a black hole.
helium to be used as fuel, This is what happens with 3C 10
and the outer layer of the a typical supernova, which
In November 1572 the
star gets pushed away from astronomers call a Type II supernova that created 3C 10
the core. Eventually the supernova. There are also was observed by Danish
helium runs low and more Type Ia, Ib and Ic supernovae, astronomer Tycho Brahe. This
changes happen: other of which Type Ia are the most spectacular ball is also known
elements are created through interesting. This is where an as Tycho’s Supernova Remnant.
Constellation: Cassiopeia
nuclear reactions and then old star, much like the Sun,
Distance: 7,500 lightyears
used as fuel. All the time has already died and become a
the star is growing larger, white dwarf star, but is pulling ESA/HUBBLE, X-RAY (NASA/CXC/NCSU/S.REYNOLDS ET AL.); RADIO (NSF/NRAO/VLA/CAMBRIDGE/D.GREEN ET AL.), NASA/ESA/J. HESTER AND A. LOLL (ARIZONA STATE UNIVERSITY), NASA/ESA/ AND THE HUBBLE HERITAGE (STSCI/AURA)-ESA/HUBBLE COLLABORATION, MPIA/NASA, NASA/ESA/JHU/R.SANKRIT & W.BLAIR, ROYAL OBSERVATORY EDINBURGH/SCIENCE PHOTO LIBRARY
becoming a red supergiant. gas off a nearby star. When KEPLER’S
the white dwarf has built SUPERNOVA
TIME BOMB up enough mass, nuclear The last supernova observed in
If the star is massive enough, reactions can take place our Galaxy. Spotted in 1604
an iron core eventually and a supernova can erupt. by Johannes Kepler, it left an
amazing remnant of colourful
forms. The star will not Type Ia supernovae are
gas and dust.
create any elements heavier useful as they all explode Constellation: Ophiuchus
than this within its core. with pretty much the same Distance: 20,000 lightyears
This heavy, very dense brightness as each other, so
core then shuts down and they can be used to measure
SN 1987A
collapses under gravity. distances from the Earth.
This distant supernova was
With no internal pressure It’s also worth noting that
spotted in 1987 in the Large
holding it up, the rest of the during a Type II supernova,
Magellanic Cloud, a dwarf
star’s matter also falls inwards. material like carbon and galaxy near the Milky Way.
It hits the core and rebounds oxygen is thrown out. In This Hubble Space Telescope
back into space at a speed fact, all the elements we are image of the remnant shows
of 70 million km/h, in an made from and rely on come several looping rings of material.
Constellation: Dorado
explosion that generates a from these fi nal moments
Distance: 168,000 lightyears
vast amount of energy. of a dying star.
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