NGC 2867 ESO126-PN008, PK278-05.01 RA 09:21:24 Dec -58° 32.8' Planetary
nebula |
Discovered by Sir John Herschel at the Cape of
Good Hope with an 18-inch f/13 speculum telescope. As his observations set out
below will show, Herschel suspected this nebula of being a real planet, and so
he carefully measured the position of nearby stars to check on any possible
motion. His first observation recorded on April 1 1834 reads: "The finest
planetary nebula I ever remember to have seen for sharpness of termination; 3
arcsec diameter; exactly round; no more haziness about them than would be about
a star of the same magnitude to-night (which is a favourable one) Light, a pale
white = star of 9th mag. Position of companion star = ... 58.6 ; star = 15th
mag. A very remarkable object. Showed to Stone, who distinctly perceived the
total difference of appearance between it and a star 9th mag very near it. A
second companion star suspected (at about half the distance of the 1st by
diagram, and at an estimated position of 330 ) among multitude of large and
small stars." The next night Herschel checked up on his potential 'planet':
"Observed with Mr. Maclear, April 2, 1834, out of the meridian. Quite
round, well defined, and about 3 arcsec or perhaps 4 arcsec diam. Much better
seen (between clouds) than last night. The small star is still 1.5 diam. from
edge. It has therefore not moved perceptibly, and is therefore not a planet."
On 26 February 1835 he recorded it as "planetary nebula, perfectly sharp;
exactly round; not the least hazy or mottled. At 1.5 diam distant from the edge
(or taking 12 arcsec for the diameter of neb at 24" dist from the centre)
there is a star at pos = 51.1 ; well examined with Mr Maclear. It bears 320
[power] well, and is quite sharp and uniform with that power." He next
recorded it as "Planetary nebula. Pos of adjacent star = ... 58.0 ; Set
micrometer to 51.1, the measure of last night, and carefully examined ...
measured tonight with the utmost care; quite calm." His observation on 10
January 1836 recorded it as "planetary nebula, round, equal to 8th mag
star; quite uniform in light; quite sharply terminated. Its diameter transits
over a wire set to 60 in 4.03 seconds, by a mean of 5 transits. Has a star
adjacent pos = 60.7 , dist = 1.5 diam from the edge. About 40 stars in the
field, among which two are 9th mag." The observation on 10 March 1836 noted
it as "Beautifully round and sharp; just like a small planet 3 arcsec or 4
arcsec in diameter at the utmost. Position of the attendant star = ... 58.5 ;
distance 2.5 diameters from the centre. Shown to Captain Henning." His
final observation on 9 January 1837 recorded it as "Diameter 8 arcsec;
perfectly uniform in light; sharply terminated, just like a small planet;
position of attendants star = 60.7 ; dist. 1.5 diam; 14th mag."
Hartung writes: "This bright pale blue
planetary nebula lies in a field profusely spangled with stars; it is round,
about 8 arcsec across, of very even light with no visible central star. Even a
three-inch will pick it out easily from the field..."
ASV Journal Vol 24 No 3 June 1971: "at
limit in 2-inch 200x."
Modern catalogues give it a magnitude of 9.6
with an 11 arcsecond diameter. The central star glows faintly at magnitude 14.8.
The Vorontsov-Velyaminov description classifies it as exhibiting ring structure.
The RNGC (Sulentic and Tifft 1973) notes that this is a 9.5 mag planetary
nebula.
6-inch f/8.6 Newtonian: Even
with the sweeping eyepiece (50', 42x), this 'star', which lies in a rich field,
looks suspicious, appearing hazy. There are two companion stars on either side
(about 10 arcmin apart); both these focus to points. At higher power, the
planetary is clearly seen as a bloated star. (suburban skies) [AS]
10-inch f/5 Newtonian: This
planetary is bright and is easy to find, lying almost within the False Cross. It
is flanked on its northeast and southwest by two 9th mag stars. At about 120x it
appears as a slightly bloated star, no colour apparent. It is not particularly
large, but does not quite focus to a point as do other field stars. (suburban
skies) [AS] |