View source for Zodiacal light

{{Short description|Faint solar glow caused by interplanetary dust at sunset and sunrise}}
{{Update|part=the hypothesized origin of the zodiacal cloud - Mars dust, rather than comets or asteroids|date=March 2021}}<!-- Steigerwald, William (9 March 2021) "Serendipitous Juno Spacecraft Detections Shatter Ideas About Origin of Zodiacal Light" https://www.nasa.gov/missions/serendipitous-juno-spacecraft-detections-shatter-ideas-about-origin-of-zodiacal-light/ -->

[[File:Night Sky from Hawai‘i and Chile (iotw2225c).jpg|right|thumb|upright=2|Two false dawns,<ref>{{cite web|title=False Dawn|url=http://www.eso.org/public/images/potw1707a/|website=www.eso.org|access-date=14 February 2017}}</ref> [[gegenschein]] (middle) and the rest of the zodiacal band of light and zodiac marked (visually crossed by the [[Milky Way]]), in this composite image of the night sky above the northern and southern hemisphere]]

The '''zodiacal light''' (also called '''false dawn'''<ref>{{Cite web | url=https://apod.nasa.gov/apod/ap120116.html |title = APOD: 2012 January 16 - Zodiacal Light and the False Dawn}}</ref><ref>{{Cite web | url=https://www.timeanddate.com/astronomy/zodiacal-lights.html |title = What are Zodiacal Lights?| date=13 January 2025 }}</ref><ref>{{Cite web|url=http://earthsky.org/astronomy-essentials/everything-you-need-to-know-zodiacal-light-or-false-dawn|title = EarthSky &#124; Zodiacal light: All you need to know|date = 6 September 2021}}</ref><ref>{{Cite web|last=Coffey|first=Rebecca|title=In Early March, Look To The West For The Zodiacal Light!|url=https://www.forbes.com/sites/rebeccacoffey/2021/03/01/in-early-march-look-to-the-west-for-the-zodiacal-light/|access-date=2021-06-05|website=Forbes|language=en}}</ref> when seen [[dawn|before sunrise]]) is a faint glow of [[photon diffusion|diffuse]] [[sunlight]] [[light scattering by particles|scattered]] by [[interplanetary dust]]. Brighter around the [[Sun]], it appears in a particularly dark [[night sky]] to extend from the Sun's direction in a roughly triangular shape along the [[zodiac]], and appears with less intensity and visibility along the whole [[ecliptic]] as the '''zodiacal band'''.<ref>{{cite encyclopedia |url=http://www.daviddarling.info/encyclopedia/Z/zodiacal_cloud.html |title=Zodiacal cloud |encyclopedia=Internet Encyclopedia of Science |first=David |last=Darling |author-link=David J. Darling}}</ref> Zodiacal light spans the entire sky and contributes<ref>{{cite journal |last=Reach |first=W. T. |year=1997 |title=The structured zodiacal light: IRAS, COBE, and ISO observations |journal=Diffuse Infrared Radiation and the Irts |volume=124 |page=1|bibcode=1997ASPC..124...33R }}</ref>  to the natural light of a clear and moonless night sky. A related phenomenon is ''[[gegenschein]]'' (or ''counterglow''), sunlight [[backscatter]]ed from the interplanetary dust, which appears [[antisolar point|directly opposite]] to the Sun as a faint but slightly brighter oval glow.

Zodiacal light contributes<ref>{{cite journal |last=Reach |first=W. T. |year=1997 |title=The structured zodiacal light: IRAS, COBE, and ISO observations |journal=Diffuse Infrared Radiation and the Irts |volume=124 |page=1|bibcode=1997ASPC..124...33R }}</ref> to the natural light of the sky, though since zodiacal light is very faint, it is often outshone and rendered invisible by [[moonlight]] or [[light pollution]].

The interplanetary dust in the [[Solar System]] forms a thick, pancake-shaped cloud called the zodiacal cloud which straddles the ecliptic plane. The [[particle size]]s range from 10 to 300 [[micrometre]]s, implying masses from one [[nanogram]] to tens of [[microgram]]s.<ref>{{cite book |last1=Peucker-Ehrenbrink |first1=Bernhard |last2=Schmitz |first2=Birger |title=Accretion of extraterrestrial matter throughout earth's history |pages=66–67 |publisher=Springer |date=2001 |isbn=978-0-306-46689-2 }}</ref><ref name=McCracken1967>{{cite journal | title=Conditions of encounter between dust and the planets | last=McCracken | first=C. W. | journal=Smithsonian Contributions to Astrophysics | volume=11 | page=213 | year=1967 | bibcode=1967SCoA...11..213M }}</ref>

The ''[[Pioneer 10]]'' and [[Helios Dust Instrumentation|''Helios'']] spacecraft observations in the 1970s revealed zodiacal light to be scattered by the [[interplanetary dust cloud]] in the Solar System.<ref name="HannerEA1976">{{cite book |chapter-url=https://ntrs.nasa.gov/search.jsp?R=19760060739 |last1=Hanner |first1=M. S. |title=Interplanetary Dust and Zodiacal Light |chapter=Pioneer 10 observations of zodiacal light brightness near the ecliptic: Changes with heliocentric distance |volume=48 |pages=29–35 |year=1976|bibcode=1976LNP....48...29H |doi=10.1007/3-540-07615-8_448 |series=Lecture Notes in Physics |isbn=978-3-540-07615-5 }}</ref><ref>{{cite journal |last1=Leinert |first1=Ch. |last2=Röser |first2=S. |last3=Buitrago |first3=L. |title=How to maintain the spatial distribution of interplanetary dust |journal=Astronomy and Astrophysics |date=February 1983 |volume=118 |issue=2 |pages=345–357 |url=https://articles.adsabs.harvard.edu/pdf/1983A%26A...118..345L |access-date=28 July 2022 |bibcode=1983A&A...118..345L}}</ref>
Analysis of images of impact debris from the ''[[Juno (spacecraft)|Juno]]'' spacecraft shows that the distribution of the dust extends from Earth's orbit to the 4:1 [[orbital resonance]] with Jupiter at {{val|2.06|u=AU}}, and suggests that the dust is from Mars.<ref>{{Cite web|last=Shekhtman|first=Lonnie|date=9 March 2021|title=Serendipitous Juno Detections Shatter Ideas About Origin of Zodiacal Light|url=https://www.jpl.nasa.gov/news/serendipitous-juno-detections-shatter-ideas-about-origin-of-zodiacal-light|url-status=live|access-date=19 March 2021|website=[[Jet Propulsion Laboratory]]|publisher=[[NASA]]|archive-date=18 March 2021|archive-url=https://web.archive.org/web/20210318004153/https://www.jpl.nasa.gov/news/serendipitous-juno-detections-shatter-ideas-about-origin-of-zodiacal-light}}</ref> However, no other dedicated dust instrumentation on ''[[Pioneer 10]]'', ''[[Pioneer 11]]'', ''[[Galileo (spacecraft)|Galileo]]'', ''[[Ulysses (spacecraft)|Ulysses]]'', nor ''[[Cassini (spacecraft)|Cassini]]'' found an indication that Mars is a significant source of dust besides comets and asteroids.<ref name="HannerEA1976" /><ref>{{cite journal |last1=Humes |first1=D. |title=Results of Pioneer 10 and 11 Meteoroid Experiments: Interplanetary and Near-Saturn |journal=Journal of Geophysical Research |date=November 1980 |volume=85 |issue=A11 |pages=5841–5852 |doi=10.1029/JA085iA11p05841 |url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA085iA11p05841 |access-date=28 July 2022 |bibcode=1980JGR....85.5841H|url-access=subscription }}</ref><ref>{{cite journal |last1=Grün |first1=E. |display-authors=etal |title=South-North and Radial Traverses through the Interplanetary Dust Cloud |journal=Icarus |date=October 1997 |volume=129 |issue=2 |pages=270–288 |doi=10.1006/icar.1997.5789 |bibcode=1997Icar..129..270G|doi-access=free }}</ref><ref name="SojaEA2019">{{cite journal |last1=Soja |first1=R.H. |last2=Grün |first2=E. |last3=Strub |first3=P. |last4=Sommer |first4=M. |last5=Millinger |first5=M. |last6=Vaubaillon |first6=J. |last7=Alius |first7=W. |last8=Camodeca |first8=G. |last9=Hein |first9=F. |last10=Laskar |first10=J. |last11=Gastieau |first11=M. |last12=Fienga |first12=A. |last13=Schwarzkopf |first13=G.H. |last14=Herzog |first14=J. |last15=Gutschke |first15=K. |last16=Skuppin |first16=N. |last17=Srama |first17=R. |title=IMEM2: a meteoroid environment model for the inner solar system |journal=Astronomy & Astrophysics |date=August 2019 |volume=628 |issue=A109 |page=13 |doi=10.1051/0004-6361/201834892 |url=https://www.aanda.org/articles/aa/full_html/2019/08/aa34892-18/aa34892-18.html |access-date=24 January 2022 |bibcode=2019A&A...628A.109S|s2cid=199117335 |doi-access=free }}</ref>

== Viewing ==
[[File:Submillimeter Array Night.jpg|thumb|Zodiacal light seen behind the [[Submillimeter Array]] from the summit of [[Mauna Kea]]]]
In the mid-latitudes, the zodiacal light is best observed in the western sky in the spring after the evening twilight has completely disappeared, or in the eastern sky in the autumn just before the morning twilight appears.  The zodiacal light appears as a column, brighter at the horizon and tilted at the angle of the ecliptic.  The light scattered from extremely small dust particles is strongly [[forward scattering]], although the zodiacal light actually extends all the way around the sky, hence it is brightest when observing at a small angle with the Sun.  This is why it is most clearly visible near sunrise or sunset when the Sun is blocked, but the dust particles nearest the line of sight to the Sun are not. The dust band that causes the zodiacal light is uniform across the whole ecliptic.

The dust further from the ecliptic is almost undetectable except when viewed at a small angle with the Sun.  Thus it is possible to see more of the width at small angles toward the Sun, and it appears wider near the horizon, closer to the Sun under the horizon.

== Origin ==

[[File:Moonlight and Zodiacal Light Over La Silla Observatory.jpg|thumb|Moonlight and zodiacal light over [[La Silla Observatory]]<ref>{{cite news|title=Moonlight and Zodiacal Light Over La Silla|url=http://www.eso.org/public/images/potw1325a/|access-date=21 July 2013|newspaper=ESO Picture of the Week}}</ref> ]]

The source of the dust has been long debated. Until recently, it was thought that the dust originated from the tails of active [[comet]]s and from collisions between [[asteroid]]s in the [[asteroid belt]].<ref>{{Cite journal|bibcode=2006DPS....38.4101E 
|title= Towards a Global Model of the Zodiacal Cloud 
|journal =Bulletin of the American Astronomical Society |volume=38 |page=557 
|author=Espy, Ashley J. |author2=Dermott, S. |author3=Kehoe, T. J. 
|date=September 2006}}</ref> Many of our meteor showers have no known active comet parent bodies.  Over 85 percent of the dust is attributed to occasional fragmentations of Jupiter-family comets that are nearly [[Extinct comet|dormant]].<ref>{{cite journal|title= Cometary Origin of the Zodiacal Cloud and Carbonaceous Micrometeorites. Implications for hot debris disks |journal=Astrophysical Journal |date=April 20, 2010 |volume=713 |issue= 2 |doi=10.1088/0004-637x/713/2/816 |bibcode=2010ApJ...713..816N |pages=816–836
|arxiv = 0909.4322 |last1= Nesvorný |first1= David |last2= Jenniskens |first2= Peter |last3= Levison |first3= Harold F. |last4= Bottke |first4= William F. |last5= Vokrouhlický |first5= David |last6= Gounelle |first6= Matthieu |s2cid=18865066 }}</ref> Jupiter-family comets have orbital periods of less than 20 years<ref>{{cite book|last=Jenniskens|first=Petrus Matheus Marie|title=Meteor showers and their parent comets|date=2006|publisher=[[Cambridge University Press]]|isbn=978-0-521-85349-1|pages=108}}</ref> and are considered dormant when not actively outgassing, but may do so in the future.<ref>{{cite web|title=Comet or Asteroid? Big Space Rock Has Identity Crisis|url=http://www.space.com/9700-comet-asteroid-big-space-rock-identity-crisis.html|publisher=SPACE.com|access-date=23 May 2011|author=SPACE.com Staff|date=6 January 2011|quote=Dormant comets retain some subsurface volatiles and may start outgassing once again as they near the sun.}}</ref> The first fully dynamical model of the zodiacal cloud demonstrated that only if the dust was released in orbits that approach Jupiter, is it stirred up enough to explain the thickness of the zodiacal dust cloud. The dust in meteoroid streams is much larger, 300 to 10,000 [[micrometre]]s in diameter, and falls apart into smaller zodiacal dust grains over time.
[[File:Romantic Sunset over the VLT.jpg|thumb|upright|Colorful center of the [[Milky Way]] and the zodiacal light above the [[Very Large Telescope]]<ref>{{cite web|title=Romantic Sunset over the VLT|url=http://www.eso.org/public/images/potw1516a/|website=www.eso.org|publisher=[[European Southern Observatory]]|access-date=21 April 2015}}</ref>]]
The [[Poynting–Robertson effect]] forces the dust into more circular (but still elongated) orbits, while spiralling slowly into the Sun. Hence a continuous source of new particles is needed to maintain the zodiacal cloud. [[Comet]]ary dust and dust generated by collisions among the [[asteroid]]s are believed to be mostly responsible for the maintenance of the dust cloud producing the zodiacal light and the [[gegenschein]].

Particles can be reduced in size by collisions or by space weathering. When ground down to sizes less than 10 micrometres, the grains are removed from the inner Solar System by solar radiation pressure. The dust is then replenished by the infall from comets. Zodiacal dust around nearby stars is called [[exozodiacal dust]]; it is a potentially important source of noise in attempts to directly image [[extrasolar planets]]. It has been pointed out that this exozodiacal dust, or hot debris disks, can be an indicator of planets, as planets tend to scatter the comets to the inner Solar System.

In 2015, new results from the secondary ion dust spectrometer COSIMA on board the [[Rosetta (spacecraft)|''ESA/Rosetta'']] orbiter confirmed that the parent bodies of interplanetary dust are most probably Jupiter-family comets such as comet [[67P/Churyumov–Gerasimenko]].<ref>{{cite journal|author=Rita Schulz |title=Comet 67P/Churyumov-Gerasimenko sheds dust coat accumulated over the past four years |journal= Nature|date=12 February 2015|issue=7538 |pages=216–218 |doi=10.1038/nature14159 |volume=518|bibcode = 2015Natur.518..216S |display-authors=etal |pmid=25624103|s2cid=205242328 }}</ref> Data from the [[Juno (spacecraft)|Juno]] mission indicate that the dust close to Earth has a local origin in the inner Solar System, best fitting the planet Mars as a source.<ref>[https://www.spacedaily.com/reports/Juno_data_shatter_ideas_about_origin_of_Zodiacal_Light_999.html Space Daily: Juno data shatter ideas about origin of Zodiacal Light]</ref>

== Appearance ==
[[File:Zodiacal Light Seen from Paranal.jpg|thumb|upright|Zodiacal light seen from [[Cerro Paranal]]]]
[[File:AS15-98-13325.jpg|thumb|[[Solar corona]] and the zodiacal light spiking along the ecliptic where [[Venus]] is visible, the brightest blurred star-like object in the photograph, viewed from the Moon under [[earthshine]], during [[Apollo 15]]]]

Zodiacal light is produced by sunlight reflecting off dust particles in the Solar System known as [[cosmic dust]]. Consequently, its [[spectroscopy|spectrum]] is the same as the [[sun|solar]] spectrum. The material producing the zodiacal light is located in a lens-shaped volume of space centered on the sun and extending well out beyond the [[orbit]] of Earth. This material is known as the [[interplanetary dust cloud]]. Since most of the material is located near the plane of the Solar System, the zodiacal light is seen along the [[ecliptic]]. The amount of material needed to produce the observed zodiacal light is quite small. If it were in the form of 1&nbsp;mm particles, each with the same [[albedo]] (reflecting power) as the [[Moon]], each particle would be 8&nbsp;km from its neighbors. The [[gegenschein]] may be caused by particles directly opposite the Sun as seen from Earth, which would be in full [[lunar phase|phase]].

According to Nesvorný and Jenniskens, when the dust grains are as small as about 150 micrometres in size, they will hit the Earth at an average speed of 14.5&nbsp;km/s, many as slowly as 12&nbsp;km/s. If so, they pointed out, this [[comet dust]] can survive entry in partially molten form, accounting for the unusual attributes of the [[micrometeorites]] collected in Antarctica, which do not resemble the larger [[meteorites]] known to originate from [[asteroids]]. In recent years, observations by a variety of spacecraft have shown significant structure in the zodiacal light including dust bands associated with debris from particular [[minor planet|asteroid families]] and several cometary trails.

== Cultural significance ==
According to [[Alexander von Humboldt]]'s ''[[Kosmos (Humboldt)|Kosmos]]'', Mesoamericans were aware of the zodiacal light before 1500.<ref name="ley196104">{{Cite magazine
 |last=Ley
 |first=Willy
 |date=April 1961
 |title=The Puzzle Called Gegenschein
 |department=For Your Information
 |url=https://archive.org/stream/Galaxy_v19n04_1961-04#page/n37/mode/1up 
 |magazine=Galaxy Science Fiction
 |pages=74–84
}}</ref> It was perhaps first reported in print by [[Joshua Childrey]] in 1661. The phenomenon was investigated by the astronomer [[Giovanni Domenico Cassini]] in 1683. According to some sources, he explained it by dust particles around the Sun.<ref>{{cite book|author=Petrus Matheus Marie Jenniskens|title=Meteor Showers and Their Parent Comets|url=https://books.google.com/books?id=QpajMuyXG8AC&pg=PA531|date=14 September 2006|publisher=Cambridge University Press|isbn=978-0-521-85349-1|page=531}}</ref><ref>{{cite book |last1=Fechtig |first1=H. |last2=Leinert |first2=Ch. |last3=Berg |first3=O. |title=Interplanetary Dust |chapter=Historical Perspectives |chapter-url=https://link.springer.com/chapter/10.1007/978-3-642-56428-4_1 |series=Astronomy and Astrophysics Library |year=2001 |pages=1–55 |publisher=Springer Link |doi=10.1007/978-3-642-56428-4_1 |isbn=978-3-642-62647-0 |access-date=23 March 2022}}</ref> Other sources state that it was first explained this way by [[Nicolas Fatio de Duillier]], in 1684,<ref>{{cite book|author=Steven J. Dick|title=Discovery and Classification in Astronomy: Controversy and Consensus|url=https://books.google.com/books?id=IT8oAAAAQBAJ&pg=PA350|date=31 August 2013|publisher=Cambridge University Press|isbn=978-1-107-03361-0|page=350}}</ref> whom Cassini advised to study the zodiacal light.{{r|ley196104}}

=== Importance to Islam ===
The [[Islam]]ic prophet [[Muhammad]] described zodiacal light in reference to the timing of the [[salat|five daily prayers]], calling it the "false dawn" ({{lang|ar|الفجر الكاذب}} ''{{transliteration|ar|al-fajr al-kādhib}}''). Muslim oral tradition preserves numerous sayings, or [[hadith]], in which Muhammad describes the difference between the light of false dawn, appearing in the sky long after sunset, and the light of the first band of horizontal light at sunrise, the "true dawn" ({{lang|ar|الفجر الصادق}} ''{{transliteration|ar|al-fajr al-sādiq}}''). According to the vast majority of Muslim scholars, [[nautical twilight|navigation twilight]] is considered the true dawn. Practitioners of Islam use Muhammad's descriptions of zodiacal light to avoid errors in determining the timing of fasting and daily prayers.<ref>[https://sunnah.com/muslim/13/52 Sahih Muslim 1094c – The Book of Fasting – Sunnah.com – Sayings and Teachings of Prophet Muhammad (صلى الله عليه و سلم)<!-- Bot generated title -->]</ref><ref>{{Cite web | url=https://books.google.com/books?id=LcNtDwAAQBAJ&q=false+dawn+hadith+by+prophet+Muhammad&pg=PA258 |title = Sahih Moslim (The Authentic Hadiths of Muslim) 1-4 Vol 2: صحيح مسلم 1/4 &#91;عربي/إنكليزي&#93; ج2|date = January 2011}}</ref><ref>{{Cite web | url=https://sunnahonline.com/library/fiqh-and-sunnah/732-distinguishing-the-true-dawn-from-the-false-dawn | title = Distinguishing the True Dawn from the False Dawn (sunnahonline.com)}}</ref>

=== Brian May ===
In 2007, [[Brian May]], lead guitarist with the band [[Queen (band)|Queen]], completed his [[thesis]], ''A Survey of Radial Velocities in the Zodiacal Dust Cloud'', thirty-six years after abandoning it to pursue a career in music.<ref>{{cite book|last1=May|first1=Brian|title=A Survey of Radial Velocities in the Zodiacal Dust Cloud|url=https://www.springer.com/gb/book/9780387777054|year=2007|publisher=[[Springer Nature]]|doi=10.1007/978-0-387-77706-1|bibcode=2007asor.book.....M|hdl=10044/1/1333|isbn=978-0-387-77705-4|accessdate=27 May 2017}}</ref> He was able to submit it only because of the minimal amount of research on the topic undertaken during the intervening years. May described the subject as being one that became "trendy" again in the 2000s.<ref>[https://www.npr.org/templates/story/story.php?storyId=128935865 Terri Gross interviews Brian May], National Public Radio show [[Fresh Air]]</ref>

== Other planets ==
[[File:Venus dust ring.png|thumb|First ever panorama image of the dust ring of Venus's orbital space, imaged by [[Parker Solar Probe]]]]
Other planets, like Venus or Mercury,<ref name="Frazier 2021">{{cite web | last=Frazier | first=Sarah | title=NASA's Parker Solar Probe Sees Venus Orbital Dust Ring | website=NASA | date=2021-04-16 | url=http://www.nasa.gov/feature/goddard/2021/nasa-s-parker-solar-probe-sees-venus-orbital-dust-ring-in-first-complete-view | access-date=2023-01-21}}</ref>   have shown to have rings of interplanetary dust in their orbital spaces.

== See also ==
{{Portal|Astronomy}}
<!-- Please keep entries in alphabetical order & add a short description [[WP:SEEALSO]] -->
{{div col|colwidth=20em|small=yes}}
* [[Exozodiacal dust]]
* [[Interplanetary dust cloud]]
* [[Kordylewski cloud]]
* [[Optical phenomenon]]
* [[Sodium tail of the Moon]]
* [[Zodi]]
{{div col end}}
<!-- please keep entries in alphabetical order -->

==References==
{{Reflist|30em}}

==External links==
{{Commons category}}
* Reach, W. T. (1997). [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997ASPC..124...33R&amp;db_key=AST "The structured zodiacal light: IRAS, COBE, and ISO observations"]. Diffuse Infrared Radiation and the IRTS. ASP Conference Series. 124, 33–40
* [http://www.as.wvu.edu/~jel/skywatch/skw9810h.html "Zodiacal Light and the Gegenschein", an essay by J. E. Littleton] {{Webarchive|url=https://web.archive.org/web/20060226112406/http://www.as.wvu.edu/~jel/skywatch/skw9810h.html |date=2006-02-26 }}
* [http://antwrp.gsfc.nasa.gov/apod/ap070925.html Zodiacal Light and the False Dawn]  September 25, 2007
* [http://apod.nasa.gov/apod/ap091029.html Zodiacal Light Over Laguna Verde] October 29, 2009
* [https://web.archive.org/web/20110716210030/http://www.twanight.org/newTWAN/photos.asp?ID=3002008 Zodiacal light as seen from above the Himalayan Hills in Uttarakhand, India]

{{Solar System}}
{{Authority control}}

[[Category:Solar System]]
[[Category:Light sources]]
[[Category:Observational astronomy]]