04.14.00
mhharismansur
Messier 78 (a reflection nebula in Orion)
ESO’s VLT reveals the Carina Nebula's hidden secrets
The Eagle Nebula
This image is a
composite of 3 filters in the visible range: B (blue), V (green) and R (red).
The Eagle's EGGs
Using the infrared
multi-mode ISAAC instrument on the 8.2-m VLT ANTU telescope, European
astronomers were able to image the Eagle Nebula at near-infrared wavelength.
The ISAAC near-infrared images cover a 9 x 9 arcminutes region, in three
broad-band colours and with sufficient sensitivity to detect young stars of all
masses and — most importantly — with an image sharpness as good as 0.35
arcseconds.
The wide-field view of
M16 shows that there is much happening in the region. The first impression one
gets is of an enormous number of stars. Those which are blue in the infrared
image are either members of the young NGC 6611 cluster — whose massive stars
are concentrated in the upper right (north west) part of the field — or
foreground stars which happen to lie along the line of sight towards M16.
Most of the stars are
fainter and more yellow. They are ordinary stars behind M16, along the line of
sight through the galactic bulge, and are seen through the molecular clouds out
of which NGC 6611 formed. Some very red stars are also seen: these are either
very young and embedded in gas and dust clouds, or just brighter stars in the
background shining through them.
This photo is the
result of a three-colour composite mosaic image of the Eagle Nebula (Messier
16), based on 144 individual images obtained with the infrared multi-mode
instrument ISAAC on the ESO Very Large Telescope (VLT) at the Paranal
Observatory. At the centre, the so-called "Pillars of Creation" can
be seen. This wide-field infrared image shows not only the central three pillars
but also several others in the same star-forming region, as well as a huge
number of stars in front of, in, or behind the Eagle Nebula. The cluster of
bright blue stars to the upper right is NGC 6611, home to the massive and hot
stars that illuminate the pillars.
Technical information:
This image was made using the near-infrared camera ISAAC on the ESO 8.2-m VLT
ANTU telescope on April 8 and May 8 - 10, 2001. The full field measures
approximately 9.1 x 9.1 arcmin, covering roughly 17 x 17 light-years (5.3 x 5.3
pc) at the distance to the region (about 6,500 light-years or 2 kpc). This
required a 16-position mosaic (4 x 4 grid) of ISAAC pointings : at each
pointing, a series of images were taken in each of the near-infrared J s -
(centred at 1.24 µm wavelength), H- (1.65µm), and K s - (2.16 µm) bands. North
is up and East left.
The total integration time for each pixel in the mosaic was 1200, 300, and 300 seconds in the central 4.5 x 4.5 arcmin region, and 200, 50, and 50 seconds in the outer part, in J s -, H-, and K s - bands, respectively. The seeing FWHM (full width at half maximum) was excellent, at 0.38, 0.36, and 0.33 arcsec in J s, H, and K s, respectively. Point sources are detected in the central region at the 3-sigma level (brightest pixel above background noise) at 22.6, 21.3, and 20.4 magnitudes in J s, H, and K s, respectively. These limits imply that a 1 million year old, 0.075 solar-mass object on the star/brown dwarf boundary could be detected in M16 through roughly 15, 20, and 30 magnitudes of visual extinction at J s, H, and K s, respectively.
After removal of instrumental signatures and the bright infrared sky background, all frames in a given band were carefully aligned and adjusted to form a seamless mosaic. The three monochromatic mosaics were then scaled to the cube root of their intensities to reduce the enormous dynamic range and enhance faint nebular features. The mosaics were then combined to create the colour-coded image, with the J s -band being rendered as blue, the H-band as green, and the K s -band as red. A total of 144 individual 1024 x 1024 pixel ISAAC images were merged to form this mosaic.
The total integration time for each pixel in the mosaic was 1200, 300, and 300 seconds in the central 4.5 x 4.5 arcmin region, and 200, 50, and 50 seconds in the outer part, in J s -, H-, and K s - bands, respectively. The seeing FWHM (full width at half maximum) was excellent, at 0.38, 0.36, and 0.33 arcsec in J s, H, and K s, respectively. Point sources are detected in the central region at the 3-sigma level (brightest pixel above background noise) at 22.6, 21.3, and 20.4 magnitudes in J s, H, and K s, respectively. These limits imply that a 1 million year old, 0.075 solar-mass object on the star/brown dwarf boundary could be detected in M16 through roughly 15, 20, and 30 magnitudes of visual extinction at J s, H, and K s, respectively.
After removal of instrumental signatures and the bright infrared sky background, all frames in a given band were carefully aligned and adjusted to form a seamless mosaic. The three monochromatic mosaics were then scaled to the cube root of their intensities to reduce the enormous dynamic range and enhance faint nebular features. The mosaics were then combined to create the colour-coded image, with the J s -band being rendered as blue, the H-band as green, and the K s -band as red. A total of 144 individual 1024 x 1024 pixel ISAAC images were merged to form this mosaic.
The Crab Nebula in Taurus
In this picture, the
green light is predominantly produced by hydrogen emission from material
ejected by the star that exploded. The blue light is predominantly emitted by
very high-energy ("relativistic") electrons that spiral in a
large-scale magnetic field (so-called synchrotron emission). It is believed
that these electrons are continuously accelerated and ejected by the rapidly
spinning neutron star at the centre of the nebula and which is the remnant core
of the exploded star. This pulsar has been identified with the lower/right of
the two close stars near the geometric center of the nebula, immediately left
of the small arc-like feature, best seen in ESO Press Photo eso9948. Technical
information: ESO Press Photo eso9948 is based on a composite of three images
taken through three different optical filters: B (429 nm; FWHM 88 nm; 5 min;
here rendered as blue), R (657 nm; FWHM 150 nm; 1 min; green) and S II (673 nm;
FWHM 6 nm; 5 min; red) during periods of 0.65 arcsec (R, S II) and 0.80 (B)
seeing, respectively. The field shown measures 6.8 x 6.8 arcminutes and the
images were recorded in frames of 2048 x 2048 pixels, each measuring 0.2
arcseconds. North is up; East is left.
Sumber : ESO
