Ghost of Jupiter

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Ghost of Jupiter
Observational Data
Designation NGC 3242
Cadwell 59
Right ascension 10h 24m 46.8s[1]
Declination -18° 38′ 38.8″[1]
Constellation Hydra
Type of object Planetary nebula
Dimensions 5.3 arcminutes[1]
Magnitude Apparent Mag: +7.3[2]
Absolute Mag: -0.9[3]
Astrometry
Distance from Earth 1,400 ly[1]
Radial velocity 4.7±0.9[4]
Proper motion RA: -17.1 mas/yr[4]
Dec.: 4.0 mas/yr[4]
Parallax 33.5±28.5 mas[4]

The Ghost of Jupiter (NGC 3242) is a planetary nebula in the constellation of Hydra.[1] Named for its resemblance to the planet Jupiter in its apparent size, the nebula was first observed in 1785 by William Herschel.[2] Herschel was the first to note a comparison the the planet Jupiter as did William Smyth, but it was likely Robert Burnham who first referred to it as the "Ghost of Jupiter." It requires high magnification and clear skies without light pollution to be seen well, but some details can be observed with smaller telescopes.

Properties and Structure

Lying some 1,400 light years away, the nebula is 5.3 arcminutes or 2 light years.[1] The nebula is of reasonable brightness for planetary nebulae, with an apparent magnitude of 7.3.[2] The nebula possess many concentric rings of gas that surround a white dwarf star at its centre.[5] Ultraviolet light from the star causes oxygen atoms to glow giving it a green colour in visible light. The nebula is expanding at around 30 km/s.[6]

The central white dwarf is much fainter than the rest of the nebula with and apparent magnitude of 12.5 though its great distance means it is 1,000 times more luminous than the Sun.[6] The star is catalogued as HD 90255 and has a temperature of 90,000 K.[6] An unusual feature of the nebula are the two red "FLIERS" at the poles of the nebula.[7] These are thought to be composed of gas, specifically nitrogen, that is moving much faster than the rest of the gas in the nebula.[6]

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Ghost of Jupiter nebula from spitzer.caltech.edu
  2. 2.0 2.1 2.2 The "Ghost of Jupiter" from oneminuteastronomer.com
  3. From definition of absolute magnitude, using apparent magnitude (+7.3) and distance (1,400 ly) given here.
  4. 4.0 4.1 4.2 4.3 NGC 3242 from simbad.u-strasbg.fr
  5. NGC 3242: The 'Ghost of Jupiter' Planetary Nebula from apod.nasa.gov
  6. 6.0 6.1 6.2 6.3 NGC 3242, a planetary nebula in Hydra from annesastronomynews.com
  7. NGC 3242, Ghost of Jupiter from spacetelescope.org