New images of the Butterfly Nebula and the Jewel Bug Nebula taken by the NASA/ESA Hubble Space Telescope are revealing information about how planetary nebulae develop their dramatic features.
The Butterfly Nebula: on top is an image captured by Hubble in 2019; further analysis by Kastner et al. produced the RGB image on the bottom, which shows extinction due to dust, as inferred from the relative strength of two hydrogen emission lines, as red; emission from nitrogen, relative to hydrogen, as green; and emission from iron as blue. Image credit: NASA / ESA / Hubble / STScI / J. Schmidt / Kastner et al.
The Butterfly Nebula is one of the brightest and more extreme examples of a pinched-waist, bipolar planetary nebula.
Also known as NGC 6302, it is located 2,417 light-years away in the constellation of Scorpius. Its butterfly shape stretches for more than two light-years, which is about half the distance from the Sun to Proxima Centauri.
The Jewel Bug Nebula, or NGC 7027, is a young and rapidly evolving planetary nebula approximately 3,000 light-years away in the constellation of Cygnus. The nebula is unusually small, measuring only 0.2 by 0.1 light-years.
Rochester Institute of Technology’s Professor Joel Kastner and colleagues observed the two nebulae in 2019 and early 2020 using panchromatic capabilities of Hubble’s Wide Field Camera 3.
They captured and analyzed near-ultraviolet (UV) to near-infrared light images to learn more about the properties of the nebulae.
“We’re dissecting them. We’re able to see the effect of the central star in how it’s shedding and shredding its ejected material,” Professor Kastner said.
“We’re able to see that material that the central star has tossed away is being dominated by ionized gas, where it’s dominated by cooler dust, and even how the hot gas is being ionized, whether by the star’s UV or by collisions caused by its present, fast winds.”
“The analysis of the new Hubble images of the Butterfly Nebula is confirming that the nebula was ejected only about 2,000 years ago and that the S-shaped iron emission that helps give it the ‘wings’ of gas may be even younger,” he added.
Surprisingly, Professor Kastner and co-author found that while other astronomers previously believed they had located the nebula’s central star, it was actually a star not associated with the nebula that is much closer to Earth than the nebula.
“We hope that future studies with the James Webb Space Telescope could help locate the actual central star,” he said.
The Jewel Bug Nebula: on the left is an image captured by Hubble in 2019; further analysis by Moraga Baez et al. produced the RGB image on the right, which shows extinction due to dust, as inferred from the relative strength of two hydrogen emission lines, as red; emission from sulfur, relative to hydrogen, as green; and emission from iron as blue. Image credit: NASA / ESA / Hubble / STScI / Alyssa Pagan / Moraga Baez et al.
The team’s ongoing analysis of the Jewel Bug Nebula is built on a 25-year baseline of measurements dating back to early Hubble imaging.
“NGC 7027 is remarkable for its unusual juxtaposition of circularly symmetric, axisymmetric, and point-symmetric (bipolar) structures,” said Paula Moraga Baez, a Ph.D. student at Rochester Institute of Technology.
“The nebula also retains large masses of molecular gas and dust despite harboring a hot central star and displaying high excitation states.”
Using radio images from the Northern Extended Millimeter Array (NOEMA) telescope, the authors identified molecular tracers of UV and X-ray light that continue to shape the Jewel Bug Nebula.
“We’re very excited about the findings,” said Dr. Jesse Bublitz, an astronomer at Green Bank Observatory.
“We had hoped to find structure that clearly showed CO+ and HCO+ spatially coincident or entirely in distinctive regions, which we did.”
“This is the first map of NGC 7027, or any planetary nebula, in the molecule CO+, and only the second CO+ map of any astronomical source.”
The scientists presented their findings on January 15, 2021 at the 237th Meeting of the American Astronomical Society (AAS).
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J. Kastner et al. Witnessingthe Shaping of the Archetypical ‘Butterfly’ Planetary Nebula NGC 6302 with HST’s Wide Field Camera 3. AAS 237, abstract # 507.01
P. Moraga Baez et al. Investigating Expansion and Extinction in the Planetary Nebula NGC 7027 with HST. AAS 237, abstract # 507.02
J. Bublitz et al. CO+, HCO+ Imaging and Outflows: Mapping NGC 7027 in New Light. AAS 237, abstract # 507.03
