View source for Astronomy:44 Nysa

{{Short description|Main-belt asteroid}}
{{Infobox planet
 | minorplanet       = yes
 | background        = #D6D6D6
 | name              = 44 Nysa
 | image             = 44Nysa (Lightcurve Inversion).png
 | image_scale        =
 | caption           = [[Astronomy:Lightcurve|Lightcurve]]-based 3D-model of ''Nysa''
 | discoverer        = H. Goldschmidt
 | discovered        = 27 May 1857
 | mpc_name          = (44) Nysa
 | pronounced        = {{IPAc-en|ˈ|n|aɪ|s|ə}}<ref>Noah Webster (1884) ''A Practical Dictionary of the English Language''</ref>
 | adjective         = Nysian {{IPAc-en|ˈ|n|ɪ|s|i|ə|n}}<ref>Katz (2004) ''The complete elegies of Sextus Propertius''</ref><ref>Stein (2004) ''Persephone Unveiled''</ref>
 | alt_names         = 1977 CE
 | named_after = Nysa
 | mp_category       = [[Astronomy:Main belt|Main belt]] ([[Astronomy:Nysa family|Nysa]])
 | orbit_ref         = <ref name=JPL-small-body>{{Cite SBDB|title=44 Nysa|id=44}}</ref>
 | epoch             = 2008-05-14 ([[Astronomy:Julian day|JD]]&nbsp;2454600.5)
 | semimajor         = {{convert|2.42380478|AU|Gm|sigfig=4|abbr=on|lk=off}}
 | perihelion        = {{convert|2.06469721|AU|Gm|sigfig=4|abbr=on|lk=off}}
 | aphelion          = {{nowrap|{{convert|2.78291235|AU|Gm|sigfig=4|abbr=on|lk=on}}}}
 | eccentricity      = 0.148158617 ± 5.7499e-08
 | period            = 3.77&nbsp;[[Astronomy:Julian year|yr]]
 | inclination       = 3.7028885 ± 6.2628e-06°
 | asc_node          = 131.59519 ± 1.0657e-04°
 | arg_peri          = 342.52066 ± 1.0904e-04°
 | mean_anomaly      = 118.743236 ± 2.4281e-05°
 | dimensions        = 113±10&thinsp;×&thinsp;67±10&thinsp;×&thinsp;65±12&nbsp;km<ref name=radar />
 | mass              = 3.7×10<sup>17</sup> kg
 | density           = 2.0 g/cm<sup>3</sup>
 | rotation          = 6.421417 ± 0.000001&nbsp;h<ref name=binary-structures />
 | pole_ecliptic_lat = +58 ± 3°&thinsp;<ref name=binary-structures />
 | pole_ecliptic_lon = 98 ± 2°&thinsp;<ref name=binary-structures />
 | spectral_type     = [[Astronomy:E-type asteroid|E]]<ref name=binary-structures />
 | magnitude         = 8.83<!-- Ephemeris 2026-Jan-24 --> to 12.46
 | abs_magnitude     = 7.03&thinsp;<ref name=JPL-small-body />
 | albedo            = 0.44 ± 0.10 (vis.)<ref name=radar /><br />0.19 ± 0.06 (rad.)<ref name=radar />
 | angular_size      = 0.09"<!-- Horizons 2026-Jan-24 --> to 0.026"
}}

'''Nysa''' ([[Astronomy:Minor planet designation|minor planet designation]]: '''44 Nysa''') is a large and very bright main-belt [[Astronomy:Asteroid|asteroid]], and the brightest member of the [[Astronomy:Nysa family|Nysian asteroid family]]. It is classified as a rare [[Astronomy:E-type asteroid|class E]] asteroid and is probably the largest of this type (though [[Astronomy:55 Pandora|55 Pandora]] is only slightly smaller).

== Discovery ==
It was discovered by Hermann Goldschmidt on May 27, 1857, and named after the mythical land of Nysa in [[Religion:Greek mythology|Greek mythology]].

== Physical properties ==
In 2002 [[Biography:Mikko Kaasalainen|Kaasalainen]] ''et al.'' used 63 [[Astronomy:Lightcurve|lightcurve]]s from the Uppsala Asteroid Photometric Catalog (UAPC) to construct a shape model of 44 Nysa. The shape model is conical, which they interpreted as indicating the asteroid may actually be a contact [[Astronomy:Binary asteroid|binary]].<ref name=binary-structures />

In 2003, Tanga ''et al.'' published results obtained from the Fine Guidance Sensor on the [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] in which high-precision interferometry was performed on Nysa with the goal of a more accurate shape determination. Due to Hubble's orbit around the Earth, hours-long photometry sessions, as are normally used to resolve the asteroid's shape, were not possible. Instead, the team used interferometry on the asteroid at the time in its rotation when it would have its longest axis perpendicular to the Earth. Ellipsoidal shape models were then fit to the resulting data to determine an estimate of the asteroid's shape. Both single and double ellipsoid models were fit to the data with both providing approximately the same goodness of fit; leaving the team unable to differentiate between a single elongated object and the contact binary model put forth by Kaasalainen ''et al.''<ref name=hubble>{{Cite journal | title = Asteroid observations with the Hubble Space Telescope. II. Duplicity search and size measurements for 6 asteroids | last = Tanga | first = P. |date=April 2003 | journal = Astronomy and Astrophysics | volume = 401 | issue = 2 | pages = 733–741 | bibcode = 2003A&A...401..733T | doi = 10.1051/0004-6361:20030032|display-authors=0| doi-access = free }}</ref>
An observation of an occultation by 44 Nysa of TYC 6273-01033-1 from the Dutch amateur astronomer Harrie Rutten showed a two-phase reappearance on March 20, 2012. This confirms the conical shape or the binary nature of Nysa.

In December 2006, Shepard ''et al.'' performed three days of [[Astronomy:Radar astronomy|radar]] observations on Nysa with the [[Astronomy:Arecibo Observatory|Arecibo radio telescope]]. The asteroid was found to have a high radar [[Physics:Polarization (waves)|polarization]] value (''μ<sub>c</sub>'') of 0.50 ± 0.2, a radar albedo (<math>\hat{\sigma}_{OC}</math>) of 0.19 ± 0.06, and a visual albedo (''p<sub>v</sub>'') of 0.44 ± 0.10.<ref name=radar /> The albedo measurements were based on a shape model worked out at Arecibo. The best fit shape model as measured by the Arecibo team has parameters a/b = 1.7 ± 0.1, a/c = 1.6–1.9, with an a-axis of 113 ± 10&nbsp;km; this gives an effective diameter of 79 ± 10&nbsp;km, which is in agreement with the HST study by Tanga ''et al.'' in 2003.<ref name=radar/> The data gathered also showed signs of significant concavity in Nysa's structure, but the dip in the radar curves is not pronounced enough to indicate bifurcation, calling into question whether or not Nysa really is a contact binary.<ref name=radar/>

Nysa has so far been reported [[Astronomy:Occultation|occulting]] a [[Astronomy:Star|star]] three times.

==Studies==
44 Nysa was in a study of asteroids using the Hubble [[Astronomy:Fine Guidance Sensor (HST)|FGS]].<ref name="Tanga 733–741">{{Cite journal|last=Tanga|first=P.|last2=Hestroffer|first2=D.|last3=Cellino|first3=A.|last4=Lattanzi|first4=M.|last5=Martino|first5=M. Di|last6=Zappalà|first6=V.|date=2003-04-01|title=Asteroid observations with the Hubble Space Telescope FGS|url=https://www.aanda.org/articles/aa/abs/2003/14/aa3023/aa3023.html|journal=Astronomy & Astrophysics|language=en|volume=401|issue=2|pages=733–741|doi=10.1051/0004-6361:20030032|issn=0004-6361|bibcode=2003A&A...401..733T|doi-access=free}}</ref> Asteroids studied include [[Astronomy:63 Ausonia|(63) Ausonia]],  [[Astronomy:15 Eunomia|(15) Eunomia]], [[Astronomy:43 Ariadne|(43) Ariadne]], (44) Nysa, and [[Astronomy:624 Hektor|(624) Hektor]].<ref name="Tanga 733–741"/>

== See also ==
* Aubrite
* [[Astronomy:E-type asteroid|E-type asteroid]]
* Hungaria family
* [[Astronomy:64 Angelina|64 Angelina]]
* [[Astronomy:3103 Eger|3103 Eger]]
* [[Astronomy:55 Pandora|55 Pandora]]
* [[Astronomy:2867 Šteins|2867 Šteins]]
* {{mpl|2015 TC|25}} (Thought to have broken off of 44 Nysa)

== References ==
{{reflist
|refs=

<ref name=radar>{{cite journal
 |title=Radar observations of E-class Asteroids 44 Nysa and 434 Hungaria
 |last=Shepard |first=M.
 |date=May 2008
 |journal=Icarus
 |volume=195
 |issue=1
 |pages=220–225
 |doi=10.1016/j.icarus.2007.12.018
 |bibcode=2008Icar..195..220S
 |display-authors=0}}</ref>

<ref name=binary-structures>{{cite journal
 |title=Binary structures among large asteroids
 |last=Kaasalainen |first=M.
 |author2=Torppa, J.
 |author3=Piironen, J.
 |date=March 2002
 |journal=Astronomy and Astrophysics
 |volume=383
 |issue=3
 |pages=L19–L22
 |bibcode=2002A&A...383L..19K
 |doi=10.1051/0004-6361:20020015|doi-access=free
 }}</ref>

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

== Further reading ==
* {{Cite journal | title = Phase relations of high albedo asteroids: The unusual opposition brightening of 44 Nysa and 64 Angelina | last = Harris | first = A.W. |date=October 1989 | journal = Icarus | volume = 81 | issue = 2 | pages = 365–374 | bibcode = 1989Icar...81..365H | doi = 10.1016/0019-1035(89)90057-2|display-authors=0}}

== External links ==
* {{AstDys|44}}
* {{JPL small body}}

{{Small Solar System bodies}}

{{DEFAULTSORT:000044}}
[[Category:Nysa asteroids]]
[[Category:Named minor planets|Nysa]]
[[Category:E-type asteroids (Tholen)]]

vec:Lista de asteroidi#44 Nisa

{{Sourceattribution|44 Nysa}}