View source for 135 Hertha

{{Short description|Main-belt asteroid}}
{{Use dmy dates|date=September 2018}}
{{Infobox planet
| minorplanet = yes
| name = 135 Hertha
| background = #D6D6D6
| image = 135 Hertha.png
| image_scale = 
| caption = [[Lightcurve]]-base 3D-model of ''Hertha'' on the top with an image of the asteroid on the bottom.
| discovery_ref = <ref name="MPC-object" />
| discoverer = [[Christian Peters|C. H. F. Peters]]
| discovery_site = [[Litchfield Observatory|Litchfield Obs.]]
| discovered = 18 February 1874
| mpc_name = (135) Hertha
| alt_names = A874 DA<ref name="jpldata"/>{{efn|The MPC notates Hertha's retroactive new-style designation as 1874&nbsp;DA.<ref name="MPC-object"/>}}
| pronounced = {{IPAc-en|'|h|ɜr|θ|ə}}
| named_after = [[Nerthus]]<ref name="springer" /><br />{{small|(Norse mythology)}}
| mp_category = [[main-belt]]<ref name="MPC-object" /><ref name="jpldata" />{{·}}{{small|([[Kirkwood gap|inner]])}}<br />[[Nysa family|Nysa]] (Hertha)<ref name="Ferret" /><ref name="AstDys-object" />
| orbit_ref = <ref name="jpldata" />
| epoch = 23 March 2018 ([[Julian day|JD]] 2458200.5)
| uncertainty = 0
| observation_arc = 133.34 [[Julian year (astronomy)|yr]] (48,701 d)
| aphelion = 2.9320 [[Astronomical unit|AU]]
| perihelion = 1.9239 AU
| semimajor = 2.4279 AU
| eccentricity = 0.2076
| period = 3.78 yr (1,382 d)
| mean_anomaly = 233.89[[Degree (angle)|°]]
| mean_motion = {{Deg2DMS|0.2605|sup=ms}} / day
| inclination = 2.3052°
| asc_node = 343.65°
| arg_peri = 340.16°
| mean_diameter = 76.12 ± 3.29 km<ref name="Carry2012"/><br />{{val|79.24|2.0|ul=km}}<ref name="jpldata" />
| mass = {{nowrap|(1.21 ± 0.16) × 10<sup>18</sup> kg<ref name="Carry2012"/>}}
| density = 5.23 ± 0.96 g/cm<sup>3</sup><ref name="Carry2012"/>
| escape_velocity = 
| rotation = {{val|8.40061|ul=h}}<ref name=shape-rotation>{{Cite journal | title = Shapes and rotational properties of thirty asteroids from photometric data | last = Torppa | first = J. |date=August 2003 | journal = [[Icarus (journal)|Icarus]] | volume = 164 | issue = 2 | pages = 346–383 | doi = 10.1016/S0019-1035(03)00146-5 | bibcode=2003Icar..164..346T|display-authors=etal}}</ref>
| albedo = 0.1436<ref name="jpldata" />
| spectral_type = [[M-type asteroid|M]]<ref name=rotational-properties>{{Cite journal | title = M-type Asteroids: Rotational properties of 16 Objects | last = Dotto | first = E. |date=October 1992 | journal = Astronomy and Astrophysics Supplement Series | volume = 95 | issue = 2 | pages = 195–211 | bibcode = 1992A&AS...95..195D|display-authors=etal}}</ref>
| abs_magnitude = 8.23<ref name="MPC-object" /><ref name="jpldata" />
}}

'''135 Hertha''' is an [[asteroid]] from the inner region of the [[asteroid belt]], approximately {{convert|77|km|mi|abbr=off|sp=us}} in diameter. Discovered on 18 February 1874 by German–American astronomer [[Christian Heinrich Friedrich Peters|Christian Peters]] at the [[Litchfield Observatory]] near Clinton, New York,<ref name="MPC-object" /> it was named after the Teutonic and Scandinavian goddess of fertility, Hertha, also known as [[Nerthus]].<ref name="springer" /> It orbits among the [[Nysa family|Nysa]] asteroid family, but its classification as a metallic [[M-type asteroid]] does not match the more common [[F-type asteroid]] for this family, suggesting that it may be an [[Interloper (asteroid)|interloper]].<ref>{{Cite journal | title = Asteroid 'clans': Super-families or multiple events? | last = Cellino | first = A. |author2= Vincenzo, Z. |date=October 1993 | journal = Celestial Mechanics and Dynamical Astronomy | volume = 57 | issue = 1–2 | pages = 34–37 | bibcode = 1993CeMDA..57...37C | doi = 10.1007/BF00692459}}</ref> Spectroscopic analysis indicates the possible presence of hydrated [[silicate]]s indicating that ''Hertha'' should possibly be reclassified from its present M-type to the proposed W-type.<ref name=puzzling-case>{{Cite journal | title = The Puzzling Case of the Nysa–Polana Family | last = Cellino | first = A. |date=August 2001 | journal = [[Icarus (journal)|Icarus]] | volume = 152 | issue = 2 | pages = 225–237 | doi = 10.1006/icar.2001.6634 | bibcode=2001Icar..152..225C|display-authors=etal}}</ref>

[[Lightcurve]] data from ''Hertha'' indicates a flattened body,<ref name=shape-rotation/> and [[radar]] observations indicate that ''Hertha'' is non-metallic.<ref name=radar>{{Cite journal | title = More Results from a Long-Term Radar Survey of M-Class Asteroids | last = Shepard | first = M.K. |date=September 2006 | journal = Bulletin of the American Astronomical Society | volume = 38 | page = 626 | bibcode = 2006DPS....38.7101S|display-authors=etal}}</ref> Five [[occultation]]s of [[star]]s by the asteroid have been observed between 2000 and 2015.

== Discovery ==
''Hertha'' was discovered by [[Christian Heinrich Friedrich Peters|C. H. F. Peters]] on 18 February 1874, in [[Clinton, Oneida County, New York|Clinton, New York]].<ref name=discovery/>  Further observations were carried out in 1883 by [[William T. Sampson|W. T. Sampson]] and communicated to [[Astronomische Nachrichten]] on his behalf by Rear Admiral [http://www.arlingtoncemetery.net/rwshufeldt-usn.htm R. W. Shufeldt].<ref>{{Cite journal | title = Observations of (135) Hertha made at the Naval Observatory Washington with 9.6 inch equatorial | last = Sampson | first = W.T. |author2= Shufeldt, R. W. | year = 1884 | journal = [[Astronomische Nachrichten]] | volume = 107 | issue = 20 | page = 323 | bibcode = 1883AN....107..323S | doi = 10.1002/asna.18841072006| url = https://zenodo.org/record/1424719 }}</ref>

== Physical properties ==
After its discovery in 1874, subsequent observations in 1884 established ''Hertha''{{'s}} orbit. Astronomers then began investigation of its physical properties.  As early as 1904, [[George William Hill|G. W. Hill]] reported observations of ''Hertha''{{'s}} brightness indicating a variation of half a magnitude and a short period.<ref name=variability>{{Cite journal | title = Variability of (135) Hertha | last = Hill | first = G.W. |date=March 1904 | journal = [[Astronomical Journal]] | volume = 24 | issue = 557 | page = 42 | bibcode = 1904AJ.....24...42H | doi = 10.1086/103543}}</ref>

In October 1992 Dotto ''et al.'' performed 20 hours of observations spread over 6 nights to investigate ''Hertha''{{'s}} rotational period, approximate shape, and the coordinates of its rotational axis.  They were able to confirm a rotational period of 8.398 ± .001 hours as previously measured by Harris ''et al.'' published earlier in 1992.<ref name=rotational-properties/><ref name=asteroid-lightcurves>{{Cite journal | title = Asteroid lightcurve observations from 1981 | last = Harris | first = A.W. |date=January 1992 | journal = [[Icarus (journal)|Icarus]] | volume = 95 | issue = 1 | pages = 115–147 | doi = 10.1016/0019-1035(92)90195-D | bibcode=1992Icar...95..115H|display-authors=etal}}</ref>  In the same study, Dotto ''et al.'' measured the asteroid's shape and rotational axis.  The axes' ratios were found to be: a/b = 1.34 ± .03 and b/c = 1.22 ± .05.  Two possible values were determined for the rotational axis, however further measurements at different [[ecliptic longitude]]s are required to determine which is correct.<ref name=rotational-properties/>

In August 2003 Torppa ''et al.'' published their results on the shape and rotational properties of a number of asteroids, including ''Hertha''.  Utilizing data from 42 lightcurves of ''Hertha'' spanning from 1978 to 2002, a more refined set of axes' ratios was obtained and a detailed shape model was obtained through inversion.  New values for the axes' ratios are: a/b = 1.1 and b/c = 1.5.  Measurements of the pole direction were also obtained, however like Dotto ''et al.'' they were unable to differentiate between their two possible solutions of (β=+58°, λ=96°) and (β=+53°, λ=274°).<ref name=shape-rotation/>

In 2017, Hanuš ''et al.'' confirmed that the correct solution is β={{val|53|3}}°, λ={{val|277|3}}°. They also calculated the first non-convex shape model, based on lightcurve and [[stellar occultation]] data.<ref name="Hanus2017"/>

=== Spectral classification ===
Although ''Hertha'' has long been classified as an M-type asteroid based on its spectral properties, observations carried out by Rivkin ''et al.'' in 1996 using the [[NASA Infrared Telescope Facility|IRTF]] at [[Mauna Kea Observatory]] have raised the possibility of reclassification.  The presence of a dip in the observed spectrum at 3&nbsp;μm indicates that the surface is hydrated, suggesting that ''Hertha'' should be reclassified as a W-type (a "wet M-type") asteroid.<ref name=3-micrometer>{{Cite journal | title = The Nature of M-Class Asteroids from 3-μm Observations | last = Rivkin | first = A.S. |date=June 2000 | journal = [[Icarus (journal)|Icarus]] | volume = 145 | issue = 2 | pages = 351–368 | doi = 10.1006/icar.2000.6354 | bibcode=2000Icar..145..351R|display-authors=etal}}</ref>  Based on work carried out by Salisbury and Walter, the Rivkin study estimated the water content of the asteroid to be between 0.14 and 0.27 percent by mass. This estimate is based on laboratory measurements and may not be applicable to asteroids in space.<ref name=3-micrometer/>

A more recent study by Rivkin ''et al.'' published in 2002 examined the dependence of spectral absorption on the asteroid's rotational phase.  The study looked at the 0.7&nbsp;μm band, which is also associated with hydrated silicates, and found that the reflectance changes as the asteroid rotates, suggesting that the surface is heterogeneous with some hydrated areas intermixed with dry areas.<ref name=hydrated-minerals>{{Cite journal | title = Hydrated Minerals on Asteroids: The Astronomical Record | last = Rivkin | first = A.S. |date=March 2002 | journal = Technical Report, Massachusetts Institute of Technology | url = http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3031.pdf|display-authors=etal}}</ref>

== Asteroid family ==
''Hertha'' is one of the core members of the [[Nysa family]] ([[FIN tbl#405|405]]) also known as Herta family.<ref name="Ferret" /><ref name="AstDys-object" /> The [[Nysa–Polana complex]] is the main-belt's largest grouping of asteroids with nearly 20,000 members.<ref name="Nesvorny-2014" />{{rp|23}}

== Notes ==
{{noteslist}}

== References ==
{{Reflist|refs=

<ref name="jpldata">{{cite web
  |type       = 2018-05-22 last obs.
  |title      = JPL Small-Body Database Browser: 135 Hertha
  |url        = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2000135
  |publisher  = [[Jet Propulsion Laboratory]]
  |accessdate = 18 September 2018}}</ref>

<ref name="springer">{{cite book
  |pages       = 27 |last       = Schmadel | first = Lutz D.
  |title = Dictionary of Minor Planet Names |publisher  = Springer Berlin Heidelberg
  |date       = 2007
  |isbn       = 978-3-540-00238-3
  |doi       = 10.1007/978-3-540-29925-7_136 |chapter       = (135) Hertha }}</ref>

<ref name="MPC-object">{{cite web
  |title      = 135 Hertha
  |work       = Minor Planet Center
  |url        = https://www.minorplanetcenter.net/db_search/show_object?object_id=135
  |accessdate = 18 September 2018}}</ref>

<ref name=discovery>{{Cite journal | title = Observations of the Planet Hertha (135), made at the Litchfield Observatory of Hamilton College | last = Peters | first = C.A.F. | year = 1874 | journal = [[Astronomische Nachrichten]] | volume = 84 | issue = 2001 | page = 129 | bibcode = 1874AN.....84..129P | doi = 10.1002/asna.18740840902| url = https://zenodo.org/record/1424687 }}</ref>

<ref name="AstDys-object">{{cite web
  |title      = Asteroid (135) Hertha
  |publisher  = AstDyS-2, Asteroids – Dynamic Site
  |url        = https://newton.spacedys.com/astdys/index.php?n=135&pc=1.1.6
  |accessdate = 18 September 2018}}</ref>

<ref name="Ferret">{{cite web
  |title      = Asteroid 135 Hertha
  |work       = Small Bodies Data Ferret
  |url        = https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=135+Hertha
  |accessdate = 18 September 2018}}</ref>

<ref name="Nesvorny-2014">{{Cite book
  |first1     = D. |last1 = Nesvorný
  |first2     = M. |last2 = Broz
  |first3     = V. |last3 = Carruba
  |date       = December 2014
  |chapter      = Identification and Dynamical Properties of Asteroid Families
  |title    = Asteroids IV
  |pages      = 297–321
  |bibcode    = 2015aste.book..297N
  |doi        = 10.2458/azu_uapress_9780816532131-ch016
  |arxiv      = 1502.01628
  |isbn = 9780816532131
  }}</ref>

<ref name="Carry2012">{{cite journal | last=Carry | first=B. | title=Density of asteroids | journal=Planetary and Space Science | volume=73 | issue=1 | year=2012 | issn=0032-0633 | doi=10.1016/j.pss.2012.03.009 | pages=98–118 | bibcode   = 2012P&SS...73...98C|arxiv = 1203.4336 }} See Table 1.</ref>

<ref name="Hanus2017">{{cite journal | last1=Hanuš | first1=J. | last2=Viikinkoski | first2=M. | last3=Marchis | first3=F. | last4=Ďurech | first4=J. | last5=Kaasalainen | first5=M. | last6=Delbo' | first6=M. | last7=Herald | first7=D. | last8=Frappa | first8=E. | last9=Hayamizu | first9=T. | last10=Kerr | first10=S. | last11=Preston | first11=S. | last12=Timerson | first12=B. | last13=Dunham | first13=D. | last14=Talbot | first14=J. | title=Volumes and bulk densities of forty asteroids from ADAM shape modeling | journal=Astronomy & Astrophysics | volume=601 | year=2017 | issn=0004-6361 | doi=10.1051/0004-6361/201629956 | page=A114 |arxiv=1702.01996 |display-authors=1 | bibcode=2017A&A...601A.114H }}</ref>

}} <!-- end of reflist -->

== Further reading ==
* {{Cite journal | title = Near-IR spectral evidence for the presence of iron-poor orthopyroxenes on the surfaces of six M-type asteroids | last1 = Hardersen | first1 = Paul S. |last2=Gaffey |first2=Michael J. |last3=Abell |first3=Paul A. |date=May 2005 | journal = [[Icarus (journal)|Icarus]] | volume = 175 | issue = 1 | pages = 141–158 | doi = 10.1016/j.icarus.2004.10.017 | bibcode=2005Icar..175..141H}}
* {{Cite journal | title = Near-infrared Reflectance Spectra Of 135 Hertha, 224 Oceana, 516 Amherstia, And 872 Holda | last1 = Hardersen | first1 = Paul S. |last2=Gaffey |first2=Michael J. |last3= Abell |first3=Paul A. |date=September 2006 | journal = Bulletin of the American Astronomical Society | volume = 38 | page = 626 | bibcode = 2006DPS....38.7103H}}

== External links ==
* [http://www.minorplanetobserver.com/pdolc/A135_2008.HTM Lightcurve plot of 135 Hertha], Palmer Divide Observatory, ''[[Brian D. Warner|B. D. Warner]]'' (2008)
* [https://web.archive.org/web/20150910160437/http://www.asteroidoccultation.com/observations/Results/Data2008/HerthaProfileNEWcolor.jpg 2008-Dec-11 Occultation] / [https://web.archive.org/web/20120821015035/http://www.asteroidoccultation.com/observations/Results/index2008.html (2008 Asteroidal Occultation Results for North America)]
* [http://www.minorplanet.info/PHP/lcdbsummaryquery.php Asteroid Lightcurve Database (LCDB)], query form ([http://www.minorplanet.info/lightcurvedatabase.html info] {{Webarchive|url=https://web.archive.org/web/20171216050541/http://www.minorplanet.info/lightcurvedatabase.html |date=16 December 2017 }})
* [https://books.google.com/books?id=aeAg1X7afOoC&pg Dictionary of Minor Planet Names], Google books
* [http://obswww.unige.ch/~behrend/page_cou.html Asteroids and comets rotation curves, CdR] – Observatoire de Genève, Raoul Behrend
* [https://www.minorplanetcenter.net/iau/lists/NumberedMPs000001.html Discovery Circumstances: Numbered Minor Planets (1)-(5000)] – Minor Planet Center
* {{AstDys|135}}
* {{JPL small body}}

{{Minor planets navigator |134 Sophrosyne |number=135 |136 Austria}}
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{{DEFAULTSORT:Hertha}}
[[Category:Nysa asteroids|000135]]
[[Category:Discoveries by Christian Peters]]
[[Category:Named minor planets]]
[[Category:Objects observed by stellar occultation|000135]]
[[Category:M-type asteroids (Tholen)|000135]]
[[Category:Xk-type asteroids (SMASS)|000135]]
[[Category:Astronomical objects discovered in 1874|18740218]]