Courtesy: MailOnline
·
The
cometary globule, also known as CG4, is powered by the leftover, dense core of
a star
·
The
head of CG4, which is the part visible in this ESO image, has a diameter of 1.5
light-years
·
Why
CG4 and other cometary globules have their distinct form is still unknown by
astronomers
·
One
theory is cometary globules are shaped by stellar winds and radiation from hot,
massive stars
The cometary globule, also known as CG4,
shines brightly in this spectacular image, and looks as though it is about to
grab at stars.
Although it appears vivid in this
picture, this is in fact a faint nebula, which makes it very hard for amateur
sky watchers to spot.
Astronomers believe it is powered by the
leftover, dense core of a star that blew up in a supernova explosion. But its
exact nature remains a mystery.
In 1976 several elongated comet-like
objects were discovered on pictures taken with the UK Schmidt Telescope in
Australia.
Because of their appearance, they became
known as cometary globules even though they have nothing in common with comets.
They had dense, dark, dusty heads and
long, faint tails, which were generally pointing away from the Vela supernova
remnant located at the centre of the Gum Nebula.
Although these objects are relatively
close by, it took astronomers a long time to find them as they glow very dimly
and are therefore hard to detect.
The object shown in this latest picture,
CG4, which is also sometimes referred to as the Mouth of the Beast, is one of
these cometary globules.
The fist of 'God's Hand', which is the
part visible on this image and resembles the head of the gigantic beast, has a
diameter of 1.5 light-years.
The tail of the globule — which extends
downwards and is not visible in the image — is about eight light-years long. By
astronomical standards this makes it a comparatively small cloud.
The relatively small size is a general
feature of cometary globules.
All of the cometary globules found so
far are isolated, relatively small clouds of neutral gas and dust within the
Milky Way, which are surrounded by hot ionised material.
The head part of CG4 is a thick cloud of
gas and dust, which is only visible because it is illuminated by the light from
nearby stars.
The radiation emitted by these stars is
gradually destroying the head of the globule and eroding away the tiny
particles that scatter the starlight.
However, the dusty cloud of CG4,
captured by the European Southern Observatory's Very Large Telescope, still
contains enough gas to make several sun-sized stars.
Why CG4 and other cometary globules have
their distinct form is still a matter of debate among astronomers and two
theories have developed.
Cometary globules could originally have
been spherical nebulae, which were disrupted and acquired their new, unusual
form because of the effects of a nearby supernova explosion.
Other astronomers suggest, that cometary
globules are shaped by stellar winds and ionising radiation from hot, massive
stars.
These effects could first lead to the
bizarrely named formations known as elephant trunks and then eventually
cometary globules.
To find out more, astronomers need to
find out the mass, density, temperature, and velocities of the material in the
globules.
These can be determined by the
measurements of molecular spectral lines which are most easily accessible at
millimetre wavelengths — wavelengths at which telescopes like the Atacama Large
Millimeter/submillimeter Array (Alma) operate.
When News Breaks Out, We Break In. (The 2014 Bloggies Finalist)
1 comment:
God is indeed great.these are divine miracles.
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