View source for IC 418

{{Short description|Planetary nebula in the constellation Lepus}}
{{Infobox planetary nebula
| image = [[Image:Spirograph Nebula - Hubble 1999.jpg|250px]]
| name = [[Index Catalogue|IC]] 418
| type = Planetary
| epoch = [[J2000]]
| ra = {{RA|05|27|28.2037}}<ref name="simbad">{{cite simbad
  | title=IC 418
  | access-date=2006-12-22}}</ref>
| dec = {{DEC|-12|41|50.265}}<ref name="simbad" />
| dist_ly = 3.6 ± 1.0 [[light year|kly]] (1100 ± 300 [[parsec|pc]])<ref name="ads">{{cite journal
  | title=Expansion Parallax of the Planetary Nebula IC 418
  | volume=138
 | pages=46–49
 | journal=The Astronomical Journal
  | bibcode=2009AJ....138...46G
  | arxiv=0905.0021
  | doi=10.1088/0004-6256/138/1/46
  | year=2009
 | last1=Guzmán
 | first1=Lizette
 | last2=Loinard
 | first2=Laurent
 | last3=Gómez
 | first3=Yolanda
 | last4=Morisset
 | first4=Christophe
 | issue=1
 | s2cid=17714722
 }}</ref>
| appmag_v = 9.6<ref name="simbad" />
| size_v = 3.5″x5.5"/11"x14"/150"/220"x250"<ref>{{cite journal
 | first=G. | last=Ramos-Larios
 |display-authors=etal
 | title=Discovery of multiple shells around the planetary nebula IC 418
 | journal=[[Monthly Notices of the Royal Astronomical Society]]
 | date=2012 | volume=423
 | issue=4 | pages=3753–3760
 | bibcode=2012MNRAS.423.3753R
 | doi=10.1111/j.1365-2966.2012.21165.x | doi-access=free
 |arxiv = 1204.5816| s2cid=118442646
 }}</ref>
| constellation = [[Lepus (constellation)|Lepus]]
| radius_ly = 0.15
| absmag_v = -
| notes = -
| names = Spirograph Nebula
|caption=A false color image of IC 418 (the spirograph nebula).}}
'''IC 418''', also known as the '''Spirograph Nebula''', is a bright [[planetary nebula]] located in the [[constellation]] of [[Lepus (constellation)|Lepus]] about 3,600 [[Light-year|ly]] away from [[Earth]]. It spans 0.3 [[light-years]] across. The central [[star]] of the planetary nebula, '''HD 35914''', is an [[O-type star]] with a [[Stellar classification|spectral type]] of O7fp.<ref>{{cite journal |last1=González-Santamaría |first1=I. |last2=Manteiga |first2=M. |last3=Manchado |first3=A. |last4=Ulla |first4=A. |last5=Dafonte |first5=C. |last6=López Varela |first6=P. |year=2021 |title=Planetary nebulae in Gaia EDR3: Central star identification, properties, and binarity |journal=Astronomy & Astrophysics |volume=656 |pages=A51 |arxiv=2109.12114 |bibcode=2021A&A...656A..51G |doi=10.1051/0004-6361/202141916 |s2cid=237940344}}</ref> The [[nebula]] formed a few thousand years ago during the star's last stages of its [[red giant]] phase. Material from the star's outer layers was ejected from the star into the surrounding space. The nebula's glow is caused by the central star's [[Ultraviolet|ultraviolet radiation]] interacting with the gas.<ref>{{Cite web |title=Spirograph Nebula (IC 418) |url=https://www.esa.int/Science_Exploration/Space_Science/Extreme_space/Spirograph_Nebula_IC_418 |access-date=2023-11-26 |website=www.esa.int |language=en}}</ref>

== Composition ==
The nebula gets its colors from the different [[Chemical element|chemical elements]] inside the nebula. The red color is [[nitrogen]] (the coldest gas in the nebula), the green is [[hydrogen]] and the traces of blue are the ionized [[oxygen]] gas (the hottest gas in the [[nebula]] due to its proximity to the central star).<ref>{{Cite web |title=Hubble's Spirograph - NASA Science |url=https://science.nasa.gov/missions/hubble/hubbles-spirograph/ |access-date=2023-11-26 |website=science.nasa.gov |date=16 June 2017 |language=en}}</ref> 

The neutral regions of IC 418 contains lots of large grains of [[amorphous carbon]] while the ionized regions of the nebula contain smaller [[graphite]] grains. There is also likely the presence of [[silicon carbide]], [[magnesium]] and [[Iron sulfide|iron sulfides]]. The presence of theses chemicals would explain the emission features seen in IC 418.<ref>{{Cite journal |last1=Gómez-Llanos |first1=V. |last2=Morisset |first2=C. |last3=Szczerba |first3=R. |last4=García-Hernández |first4=D. A. |last5=García-Lario |first5=P. |date=2018-09-01 |title=Modeling dust emission in PN IC 418 |url=https://www.aanda.org/articles/aa/abs/2018/09/aa31707-17/aa31707-17.html |journal=Astronomy & Astrophysics |language=en |volume=617 |pages=A85 |doi=10.1051/0004-6361/201731707 |issn=0004-6361|arxiv=1806.10248 |bibcode=2018A&A...617A..85G }}</ref>

== Structure ==
IC 418 shows a multi-shelled structure with the main nebula slightly off centered to the outer elliptical halo. The nebula also contains numerous radial filaments, rays, a system of three concentric rings with time lapse between the rings being ∼630 years. There are also two detached haloes with time lapse between the two haloes is around 10,000–50,000 years.  There is also the presence of little blisters or ‘bubble-like’ features on to the exterior walls of the nebular shell.<ref>{{Cite journal |last1=Ramos-Larios |first1=G. |last2=Vázquez |first2=R. |last3=Guerrero |first3=M. A. |last4=Olguín |first4=L. |last5=Marquez-Lugo |first5=R. A. |last6=Bravo-Alfaro |first6=H. |date=2012-07-11 |title=Discovery of multiple shells around the planetary nebula IC 418 |journal=Monthly Notices of the Royal Astronomical Society |volume=423 |issue=4 |pages=3753–3760 |doi=10.1111/j.1365-2966.2012.21165.x |bibcode=2012MNRAS.423.3753R |doi-access=free |issn=0035-8711|arxiv=1204.5816 }}</ref>

[[Extinction (astronomy)|Extinction]] maps show that extinction tends to be higher at or close to the rim of the nebula.<ref>{{cite journal |last1=Monreal-Ibero |first1=Ana |last2=Walsh |first2=Jeremy R. |title=Studying Nearby Galactic Planetary Nebulae with MUSE: On the Physical Properties of IC 418 |journal=Galaxies |date=2022 |volume=10 |issue=1 |page=18 |doi=10.3390/galaxies10010018 |doi-access=free |bibcode=2022Galax..10...18M |hdl=1887/3515676 |hdl-access=free }}</ref>

=== Inner shell ===
The inner shell of IC 418 is particularly bright that higher relative excitation which is common for the inner shell of planetary nebulas. The  inner shell overplotted with the two slits going across the central star. The velocity of the gas at the poles has been determined to be traveling at 15.7 km/s while the equatorial gas travels at 12.6 km/s. These speeds only apply to the outer skirts of the inner shell.

=== Radial filaments and rays ===
The nebula contains numerous low surface brightness radial filaments and rays that emanate from the bright shell of IC 418. The filaments are mostly radial pointing towards the location of the central star. They are relatively featureless and broad. The separation of the rings are not uniform.

=== Halos ===
IC 418 contains halos, the inner halo and the outer halo. The time lapse between the two haloes is around 10,000–50,000 years. The faint inner halo is ionized but much is unclear about this halo. The outer halo is elliptical and five times fainter than the inner halo. It has a notable limb-brightened morphology, and its western tip is brighter than the eastern tip. Information on the kinematics of the halos is not available because the low surface brightness.

==Naming==
The name derives from the intricate pattern of the [[nebula]], which resembles a pattern which can be created using the [[Spirograph]], a toy that produces [[geometric pattern]]s (specifically, [[hypotrochoid]]s and [[epitrochoid]]s) on paper. The origin of the Spirograph pattern is unknown.<ref>{{Cite web |last=information@eso.org |title=The Spirograph Nebula |url=https://www.spacetelescope.org/images/opo0028a/ |access-date=2023-11-26 |website=www.spacetelescope.org |language=en}}</ref>

==References==
{{Reflist}}

==External links==
*{{commonscat-inline}}
*[http://hubblesite.org/newscenter/newsdesk/archive/releases/2000/28/image/a The Spirograph Nebula (IC 418) - STScI Press Release]
*[[Astronomy Picture of the Day]] - [http://apod.nasa.gov/apod/ap100411.html IC 418: The Spirograph Nebula] - 2010 April 11
{{Lepus (constellation)}}
{{DEFAULTSORT:Ic 418}}
[[Category:Planetary nebulae|IC 0418]]
[[Category:Lepus (constellation)|IC 0418]]
[[Category:IC objects|0418]]
[[Category:O-type stars]]