ESO has just released a stunning new image
of a field of stars towards the constellation
of Carina.
This striking view is ablaze with a flurry
of stars of all colours and brightness,
some of which glow against a backdrop of gas
and dust clouds.
A complex nebula created by previous, violent
ejections surrounds an unusual star in the
middle of this field.
Astronomers have discovered that this star
has a companion.
Interactions in this double star system,
surrounded by a dusty disc, may be the engine
fuelling the star’s remarkable nebula.
Today we will explore a new, beautiful ESO
image that shows a rich field of stars centred
on a star called HD 87643.
A study using a new set of observations has
provided astronomers with the best ever views
of this exotic type of star.
The image, taken in the direction of the constellation
of Carina, shows a dense starscape towards
the Carina arm of the Milky Way Galaxy.
As we come closer, we see the star HD 87643,
a so-called B[e] star at a distance of 4,900
lightyears.
The image beautifully shows the extended nebula
of gas and dust that reflects the light from
the star.
The central star’s wind appears to have
shaped the nebula, leaving bright, ragged
tendrils of gas and dust.
A careful investigation of these features
seems to indicate that there are regular ejections
of matter from the star every 15 to 50 years.
The sheer range of this set of observations,
from the panoramic Wide Field Imager shot
to the fine details of the VLTI observations,
corresponds to a zoom-in factor of 60 000
between the two extremes.
With this data, the astronomers found out
that HD 87643 has a companion star
located at about 50 times the Earth–Sun
distance, and is embedded in a compact dust
shell.
The two stars probably orbit each other in
a period between 20 and 50 years.
The presence of this companion could provide
an explanation for the regular ejection of
matter
from HD 87643 that forms its amazing nebula.
As the companion star moves in a highly elliptical,
or oval-shaped, orbit,
it regularly comes very close to HD 87643,
and triggers an ejection of stellar material.
This celestial tango may be what generates
the gorgeous nebula
The NASA/ESA Hubble Space Telescope has recently
revealed magnificent sections of the Veil
Nebula
– the shattered remains of a supernova that
exploded some 5-10,000 years ago.
The new Hubble images provide beautiful views
of the delicate, wispy structure resulting
from this cosmic cataclysm.
Welcome to the Hubblecast!
Today we will take a closer look at one of
the most violent events in the Universe – a
supernova explosion.
It is the debris from one of these cosmic
explosions that we can see with unprecedented
detail
in these brand new images from the Hubble
Space Telescope.
Although we don’t usually think about it,
the stars twinkling in the night sky do not
shine forever.
How long a star lives depends on how big and
heavy it is.
The bigger a star, the shorter its life.
Now a star shines because of the nuclear fire
burning at its center.
And when a star significantly larger than
our Sun runs out of fuel for this fire,
it first collapses and then blows itself apart
in a gigantic explosion that we call a supernova.
A supernova releases so much light that it
can outshine all of the stars of an entire
galaxy put together.
The explosion sweeps out a huge bubble in
its surroundings, and at the fringe of this
bubble
we find the actual debris from the star as
well as the material that has been swept up
by the blast wave.
It is this glowing, brightly-coloured shell
of gas that we see as a nebula,
and that astronomers refer to as a ‘supernova
remnant’.
Now the remnant can remain visible for a very
long time after the actual explosion itself
has faded away.
Astronomers have pointed Hubble towards the
constellation of Cygnus to observe the Veil
Nebula in the wing of the Swan.
Located at a distance of 1,500 light-years
from Earth, the Veil Nebula, which is also
known as Cygnus Loop,
is one of the most spectacular supernova remnants
in the sky.
The entire shell spans some 3 degrees, corresponding
to about 6 full moons.
[music]…
One of the most remarkable parts of the remnant
is the so-called Witch’s Broom Nebula.
The bright blue star – dubbed 52 Cygnus
is unrelated to the supernova explosion.
It can be observed with the naked eye on a
clear summer’s night.
The small regions captured in the new Hubble
images provide stunning close-ups of the Veil.
Fascinating smoke-like wisps of gas are all
that remain visible of what was once a Milky
Way star.
Scientists estimate that the supernova explosion
occurred some 5-10,000 years ago.
Now what that means is that it could have
been witnessed and recorded by ancient civilizations.
What they would have seen is a star increasing
its brightness roughly to the brightness of
the crescent Moon.
The intertwined rope-like filaments of gas
in the Veil Nebula result from the enormous
energy released
as the fast-moving debris from the supernova
explosion ploughs into the surroundings and
creates a shock front.
This shock, driven by debris moving at 600,000
kilometres per hour, heats the gas to millions
of degrees.
It is the subsequent cooling of this material
that produces the brilliantly coloured glows.
The Hubble images of the Veil Nebula are striking
examples of how processes that take place
hundreds of light-years away
can sometimes resemble effects we see around
us in our daily lives.
There are similarities with the patterns formed
by the interplay of light and shadow
on the bottom of a swimming pool, rising smoke
or wispy cirrus clouds
So why are astronomers interested in studying
supernovae and their remnants?
The reason is, that they are extremely important
for understanding the history of our own Milky
Way.
Although only a few stars per century in our
Galaxy end their lives in this spectacular
way,
these explosions are more or less directly
responsible for creating all the elements
in our universe that are heavier than iron.
For example, all the copper, mercury, gold,
iodine and lead that we see on Earth around
us here today
were forged in these violent explosions billions
of years ago.
The expanding shells of the supernova remnants
eventually mixed with other material in the
Milky Way
and this became the raw material for the next
generation of stars and planets including
our own solar system.
So the chemical elements that constitute the
planets, the Earth, the plants and animals
around us –
and indeed our very selves – were built
deep inside ancient stars and in supernova
explosions.
So the green in the grass and the red of our
blood are in fact the colours of stardust.
In an unprecedented 16-year-long study, using
several of ESO’s flagship telescopes,
astronomers have produced the most detailed
view ever of the surroundings of the monster
lurking
at our Galaxy’s heart — a supermassive
black hole.
The research has unravelled the hidden secrets
of this tumultuous region by mapping the orbits
of almost 30 stars.
A team of German astronomers, with characteristic
precision and patience, has spent 16 years
mapping out the motions of 28 stars orbiting
the very centre of our Milky Way galaxy.
Now, astronomers have believed for quite a
while that the centre of our galaxy is the
site of a supermassive black hole.
Black holes are a consequence of General Relativity.
They are objects that are so dense and whose
gravity is so strong, that not even light
can escape them.
These observations that we are going to show
you today are the best evidence yet that black
holes
are not just theoretical constructs, but actually
do exist in reality.
This is truly a milestone result..
Observers under dark skies, far from the bright
city lights, can marvel at the splendour of
the Milky Way,
arching in an imposing band across the sky.
Zooming in towards the centre of our galaxy,
about 25000 light years away, you can see
that it is composed of myriads of stars.
This is a pretty impressive sight, but much
is hidden from view by interstellar dust,
and astronomers need to look using a different
wavelength, the infrared that can penetrate
the dust clouds.
With large telescopes, astronomers can then
see in detail the swarm of stars circling
the super massive black hole, in the same
way that the Earth orbits the Sun.
The Galactic centre harbours the nearest supermassive
black hole known,
and also the one that is largest in term of
its angular diameter in the sky
Making it the best choice for a detailed study
of black holes.
So what this team did was at various parts
of the last 16 years, they kept taking images
of the very central region of the Milky Way.
Now, from these images, they were able to
map out the motions of a total of 28 stars.
Now, what these motions showed was that these
stars aren’t just moving about randomly,
but that they are clearly orbiting a very
massive, central object.
And the point is that this central object
is completely unseen.
Now, from the motions it’s also possible
to deduce the mass of the central object.
It came out to be a little over four million
times the mass of the Sun.
Now, what’s more, that enormous mass has
to fit into a tiny little volume,
and so one cannot escape the conclusion that
the central object really is a black hole.
