Jonckheere 900

Lore & Background

J900 was discovered in 1912 by French astronomer R. Jonckheere using the Lille University observatory. He initially thought it was a double star, but the Hubble Space Telescope later determined the object was not a double star. A faint field star located roughly 11 arcseconds from the central star gives the illusion of a double system. The nebula has a distance ranging from 3.89 to 6 kiloparsecs, with an average value of ~4.6 kpc. The ionization front is located at ~8.5 arcseconds from the central star. The nebula has a temperature floor of ~829 K, derived from an H2 temperature of 755±36 K. H2 lines are emitted from both a ~670 K warm region and a ~3200 K hot region. Emission lines with calculated electron temperatures and densities include: [O III] with Te = 11,600±1160 K and ne = 3600±1160 cm⁻³; S III with Te = 13,000 K; N II with Te = 11,500 K; O II with Te = 10,300 K and ne = 3980 cm⁻³; S II with Te = 7800 K and ne = 3600 cm⁻³; and [Ar IV] with ne = 8240 cm⁻³. The nebula was detected to have Kr III and Se IV lines. Forbidden Lines of [Kr], [Rb], and [Xe] were detected in the BOES spectrum while the F line was detected using the mid-IR Spitzer infrared spectrograph.

Reader's Guide

Jonckheere 900 is significant as a bipolar planetary nebula that was initially mistaken for a double star by its discoverer, a misidentification later corrected by the Hubble Space Telescope. Its distance is not precisely known, ranging from 3.89 to 6 kiloparsecs, with an average of ~4.6 kpc. The nebula is notable for the detection of forbidden lines of krypton, rubidium, and xenon in the BOES spectrum, as well as Kr III and Se IV lines, and an F line detected with the Spitzer infrared spectrograph. These detections indicate the presence of heavy elements produced by nucleosynthesis in the progenitor star. The central star has an effective temperature of ~134,800 K, calculated from the I(He II 4686 Å)/I(H β) ratio, and evolved from an initial mass of ~2.0 M⊙. The nebula's H2 emission arises from two distinct temperature regions, a warm ~670 K component and a hot ~3200 K component, and its ionization front lies ~8.5 arcseconds from the central star. The presence of a faint field star 11 arcseconds away perpetuates the visual illusion of a double system.

Did You Know?

• J900 was initially thought to be a double star by its discoverer R. Jonckheere.
• The Hubble Space Telescope later determined that J900 is not a double star.
• Forbidden lines of krypton, rubidium, and xenon were detected in the BOES spectrum of J900.
• The central star of J900 has an effective temperature of approximately 134,800 K.