These images of distant galaxies shown above are a perfect examples
of gravitational lensing. In the middle of the image are a large number
of galaxies stretched out into almost straight streaks of light that
look like shooting stars. Meanwhile, just above and to the right of the
large, bright elliptical galaxy in the upper left of the image is a
spiral galaxy whose apparent shape has been stretched and mirror-morphed
into the shape of an alien from the classic 1970s computer game Space
Invaders! A second, less distorted image of the same galaxy appears to
the left of the elliptical galaxy.
Hubble’s ability to see distant objects will be enhanced with the start
of Frontier Fields in the near future, an observing campaign that aims
to combine the power of Hubble with the natural gravitational telescopes
of high-magnification clusters of galaxies — as seen here with Abell
68. This will enable Hubble to see objects that would ordinarily be too
distant or faint for it to see.
Frontier Fields will study six different galaxy clusters to give us a
sneak preview of the very earliest stars and galaxies, before the
launch of the James Webb Space Telescope in 2018. Although the resulting
images projected to us of these distant galaxies are typically heavily
deformed, this process, called gravitational lensing, is a hugely
valuable tool in cosmology, the branch of astronomy which deals with the
origins and evolution of the Universe.
The effect of this huge concentration of matter is to deform the
fabric of spacetime, which in turn distorts the path that light takes
when it travels through the cluster. For galaxies that are even further
away than the cluster — which is already at the impressive distance of
two billion light-years — and which are aligned just right, the effect
is to turn galaxies that might otherwise be invisible into ones that can
be observed with relative ease.
Another striking feature of the image, one unrelated to gravitational
lensing, is the galaxy in the top right corner of the image. What
appears to be purple liquid dripping from the galaxy is a phenomenon
called ram pressure stripping. The gas clouds within the galaxy are
being stripped out and heated up as the galaxy passes through a region
of denser intergalactic gas.
This image comes from the infrared channel of Hubble’s Wide Field
Camera 3, combined with near-infrared observations from the Advanced
Camera for Surveys. This offers a modest taster of the kind of images
that will come from the forthcoming NASA/ESA/CSA James Webb Space
Telescope, which is scheduled for launch in 2018.
Infrared images are particularly useful for studying very distant
objects whose light is redshifted into the infrared by the expansion of
the Universe, as well as for peering through dust clouds which are
opaque to visible light. The Webb telescope will produce images which
are sharper than Hubble’s infrared images, but more importantly, it will
be much more sensitive, thanks to its advanced sensors and larger
primary mirror.
The image is based in part on data spotted by Nick Rose in the Hubble’s Hidden Treasures image processing competition.
Source: The Daily Galaxy via http://www.spacetelescope.org
No hay comentarios:
Publicar un comentario