M1-b

PR Photo 40f/99 shows a three colour composite of the well-known Crab
Nebula (also known as "Messier 1"), as observed with the FORS2
instrument in imaging mode in the morning of November 10, 1999. It is
the remnant of a supernova explosion at a distance of about 6,000
light-years, observed almost 1000 years ago, in the year 1054. It
contains a neutron star near its center that spins 30 times per second
around its axis (see below). PR Photo 40g/99 is an enlargement of a
smaller area. More information on the Crab Nebula and its pulsar is
available on the web, e.g. at a dedicated website for Messier objects.

In this picture, the red 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
syncrotron 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 PR Photo
40g/99.

Technical information: Photo 40f/99 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 arcmin and the images were recorded in frames of
2048 x 2048 pixels, each measuring 0.2 arcsec.  The Full Resolution
version shows the original pixels. North is up; East is left.


ESO Press Information is made available on the World-Wide Web (URL:
http://www.eso.org/outreach/press-rel/). ESO Press Photos may be
reproduced, if credit is given to the European Southern Observatory.