Masquerading as a double star

The object in this image is Jonckheere 900 or J 900, a planetary nebula — glowing shells of ionised gas pushed out by a dying star. Discovered in the early 1900s by astronomer Robert Jonckheere, the dusty nebula is small but fairly bright, with a relatively evenly spread central region surrounded by soft wispy edges.

Despite the clarity of this Hubble image, the two objects in the picture above can be confusing for observers. J 900’s nearby companion, a faint star in the constellation of Gemini, often causes problems for observers because it is so close to the nebula — when seeing conditions are bad, this star seems to merge into J 900, giving it an elongated appearance. Hubble’s position above the Earth’s atmosphere means that this is not an issue for the space telescope.

Astronomers have also mistakenly reported observations of a double star in place of these two objects, as the planetary nebula is quite small and compact.

J 900’s central star is only just visible in this image, and is very faint — fainter than the nebula’s neighbour. The nebula appears to display a bipolar structure, where there are two distinct lobes of material emanating from its centre, enclosed by a bright oval disc.

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Josh Barrington.

Credit:

ESA/Hubble & NASA
Acknowledgement: Josh Barrington

About the Image

Id:potw1312a
Type:Observation
Release date:25 March 2013, 10:00
Size:568 x 586 px

About the Object

Name:Jonckheere 900, PN G194.2+02.5
Type:Milky Way : Nebula : Type : Planetary
Constellation:Gemini
Category:Nebulae

Coordinates

Position (RA):6 25 57.13
Position (Dec):17° 47' 27.94"
Field of view:0.47 x 0.49 arcminutes
Orientation:North is 46.1° right of vertical

Colours & filters

BandWavelengthTelescope
Optical
O III
502 nm Hubble Space Telescope
WFPC2
Optical
V
555 nm Hubble Space Telescope
WFC2
Optical
H-alpha
658 nm Hubble Space Telescope
WFPC2

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