View source for Astronomy:(85713) 1998 SS49

{{short description|Asteroid}}
{{DISPLAYTITLE:{{mp|(85713) 1998 SS|49}}}}
{{Infobox planet
 | minorplanet     = yes
 | name            = {{mp|(85713) 1998 SS|49}}
 | background      = #FFC2E0
 | image           = 
 | image_size      = 
 | caption         = 
 | discovery_ref   = <ref name="jpldata" />
 | discoverer      = [[Astronomy:Lincoln Near-Earth Asteroid Research|LINEAR]]
 | discovery_site  = Lincoln Lab's ETS
 | discovered      = 29 September 1998
 | mpc_name        = {{mp|(85713) 1998 SS|49}}
 | alt_names       = {{mp|1998 SS|49}}
 | pronounced      = 
 | named_after     = <!--xafter<br />{{small|(description)}}<ref name="MPC-object" />-->
 | mp_category     = [[Astronomy:Apollo asteroid|Apollo]]{{·}}[[Astronomy:Near-Earth object|NEO]]{{·}}[[Astronomy:Potentially hazardous object|PHA]]<ref name="jpldata" /><ref name="MPC-object" />
 | orbit_ref       = <ref name="jpldata" />
 | epoch           = 4 September 2017 ([[Astronomy:Julian day|JD]] 2458000.5)
 | uncertainty     = 0
 | observation_arc = 18.05 yr (6,593 days)
 | aphelion        = 3.1535 [[Astronomy:Astronomical unit|AU]]
 | perihelion      = 0.6940 AU
 | semimajor       = 1.9237 AU
 | eccentricity    = 0.6393
 | period          = 2.67 [[Astronomy:Julian year|yr]] (975 days)
 | mean_anomaly    = 359.74[[Degree (angle)|°]]
 | mean_motion     = {{Deg2DMS|0.3694|sup=ms}} / day
 | inclination     = 10.764°
 | asc_node        = 41.493°
 | arg_peri        = 102.47°
 | moid            = 0.0023 AU{{·}}0.9 [[Astronomy:Lunar distance|LD]]
 | dimensions      = {{val|2.00|0.06}} km<ref name="AKARI" /><br />2.25 km {{small|(calculated)}}<ref name="lcdb" /><br />{{val|3.03|1.49}} km<ref name="Nugent-2016" /><br />{{val|3.484|0.789}} km<ref name="Mainzer-2011" /><ref name="WISE" />
 | rotation        = {{val|5.370|0.005}} [[Hour|h]]<ref name="Warner-2015c" />{{efn|name=lightcurve-plot-Warner-1}}<br />{{val|5.398|0.001}} h<ref name="Vaduvescu-2017" /><br />{{val|5.66|0.01}} h<ref name="Warner-2015h" />{{efn|name=lightcurve-plot-Warner-2}}
 | albedo          = {{val|0.076|0.039}}<ref name="Mainzer-2011" /><ref name="WISE" /><br />{{val|0.08|0.12}}<ref name="Nugent-2016" /><br />0.20 {{small|(assumed)}}<ref name="lcdb" /><br />{{val|0.237|0.018}}<ref name="AKARI" />
 | spectral_type   = [[Astronomy:S-type asteroid|S]] {{small|(assumed)}}<ref name="lcdb" />
 | abs_magnitude   = 15.6<ref name="jpldata" /><ref name="lcdb" />{{·}}15.70<ref name="AKARI" /><ref name="WISE" />{{·}}{{val|15.80|0.29}}<ref name="Veres-2015" />{{·}}16.01<ref name="Nugent-2016" />
}}

'''{{mp|(85713) 1998 SS|49}}''' (provisional designation '''{{mp|1998 SS|49}}''') is an [[Astronomy:Asteroid|asteroid]] on an eccentric orbit, classified as [[Astronomy:Near-Earth object|near-Earth object]] and [[Astronomy:Potentially hazardous asteroid|potentially hazardous asteroid]] of the [[Astronomy:Apollo asteroid|Apollo group]], approximately {{convert|3|km|mi|abbr=off|sigfig=2|sp=us}} in diameter. The asteroid was discovered on 29 September 1998, by astronomers of the [[Astronomy:Lincoln Near-Earth Asteroid Research|LINEAR]] program at Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico, in the United States.<ref name="MPC-object" /> It is one of the largest potentially hazardous asteroids and has a notably low Earth-[[Astronomy:Minimum orbit intersection distance|MOID]] of less than the distance to the Moon.<ref name="MPC-PHA-list" />

== Orbit and classification ==

{{mp|1998 SS|49}} is a member of the dynamical [[Astronomy:Apollo asteroid|Apollo group]],<ref name="jpldata" /><ref name="MPC-object" /> which are Earth-crossing asteroids. Apollo asteroids are the largest subgroup of [[Astronomy:Near-Earth object|near-Earth object]]s.

It orbits the Sun at a distance of 0.7–3.2&nbsp;[[Astronomy:Astronomical unit|AU]] once every 2 years and 8 months (975 days; semi-major axis of 1.92&nbsp;AU). Its orbit has a high [[Astronomy:Orbital eccentricity|eccentricity]] of 0.64 and an [[Astronomy:Orbital inclination|inclination]] of 11[[Degree (angle)|°]] with respect to the [[Astronomy:Ecliptic|ecliptic]].<ref name="jpldata" /> The body's [[Astronomy:Observation arc|observation arc]] begins with its official discovery observation at Socorro in September 1998.<ref name="MPC-object" />

=== Close approaches ===

At about [[Astronomy:Absolute magnitude|absolute magnitude]] 15.6, {{mp|1998 SS|49}} is one of the brightest and presumably largest known [[Astronomy:Potentially hazardous asteroid|potentially hazardous asteroid]] ''(see [[Astronomy:Potentially hazardous asteroid#Largest PHA|PHA-list]])''.<ref name="MPC-PHA-list" /> It has a very low ''Earth minimum orbital intersection distance'' of {{Convert|0.0023|AU|e3km LD|abbr=unit|lk=on}}.<ref name="jpldata" /> On 26 November 1902, this asteroid made its closest near-Earth encounter since 1900 at a nominal distance of {{Convert|0.0659|AU|e6km LD|abbr=unit|lk=on}}. The next notable close approach will be on 21 November 2022 passing at a nominal distance of {{convert|0.141|AU|km mi|abbr=on|lk=off}}.<ref name="jpldata" />

{{mp|1998 SS|49}} is also a Venus- and [[Astronomy:Mars-crosser|Mars-crosser]], as it crosses the orbit of [[Astronomy:Venus|Venus]] and the Red Planet at {{circa}} 0.72 and 1.66&nbsp;AU, respectively.

== Physical characteristics ==

{{mp|1998 SS|49}} is an assumed, stony [[Astronomy:S-type asteroid|S-type asteroid]].<ref name="lcdb" />

=== Rotation period ===

In 2014, two rotational [[Astronomy:Lightcurve|lightcurve]]s of {{mp|1998 SS|49}} were obtained from photometric observations by American astronomer Brian Warner at the CS3–Palmer Divide Station in California ({{small|U82}}). Lightcurve analysis gave a [[Rotation period|rotation period]] of 5.370 and 5.66 hours and a brightness variation of 0.18 and 0.06 [[Astronomy:Magnitude|magnitude]], respectively ({{small|U=2/2}}), one of which gave an alternative period solution of {{val|2.686|0.002}} hours.<ref name="Warner-2015c" /><ref name="Warner-2015h" />{{efn|name=lightcurve-plot-Warner-1}}{{efn|name=lightcurve-plot-Warner-2}} In April 2016, the [[Astronomy:EURONEAR|EURONEAR]] lightcurve survey measured a period of 5.398 hours with an amplitude of 0.12 magnitude ({{small|U=2}}).

=== Diameter and albedo ===

Surveys contrast: of the Japanese [[Astronomy:Akari (satellite)|Akari satellite]] and the [[Astronomy:NEOWISE|NEOWISE]] mission of NASA's [[Astronomy:Wide-field Infrared Survey Explorer|Wide-field Infrared Survey Explorer]].  These measure the object as between 2 and 3.484 kilometers lengthways (''in diameter'') and to have an [[Astronomy:Astronomical albedo|albedo]] (optical wavelength reflectivity) between 0.076 and 0.237.<ref name="AKARI" /><ref name="Nugent-2016" /><ref name="Mainzer-2011" /><ref name="WISE" /> The ''Collaborative Asteroid Lightcurve Link'' assumes a stony typical albedo of 0.20 to calculate the diameter as 2.25 kilometers and an absolute magnitude of 15.6.<ref name="lcdb" />

== Numbering and naming ==

This [[Astronomy:Minor planet|minor planet]] was [[Astronomy:Minor planet designation|numbered]] by the [[Organization:Minor Planet Center|Minor Planet Center]] on 30 August 2004.<ref name="MPC-Circulars-Archive" /> As of 2018, it has not been [[Astronomy:List of named minor planets (alphabetical)|named]].<ref name="MPC-object" />

== Notes ==
{{notelist|refs=

{{efn|name=lightcurve-plot-Warner-1|1=[http://www.planetarysciences.org/plots/BDW/85713_1998SS49_2014-09-26.PNG Lightcurve plot of {{mp|(85713) 1998 SS|49}}] – ambiguous rotation period {{val|5.370|0.005}} and {{val|2.686|0.002}} hours, by B. D. Warner at the CS3–Palmer Divide Station (2014). Quality code of 2. Summary figures at the [http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=85713%7C LCDB] and [http://www.planetarysciences.org CS3 website].}}

{{efn|name=lightcurve-plot-Warner-2|1=[http://www.planetarysciences.org/plots/BDW/85713_1998SS49_2014-11-20.PNG Lightcurve plot of {{mp|(85713) 1998 SS|49}}] – rotation period {{val|5.66|0.01}} hours, by B. D. Warner at the CS3–Palmer Divide Station (2014). Quality code of 2. Summary figures at the [http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=85713%7C LCDB] and [http://www.planetarysciences.org CS3 website].}}

}} <!-- end of notelist -->

== References ==
{{reflist|30em|refs=

<ref name="jpldata">{{cite web
  |type       = 2016-10-17 last obs.
  |title      = JPL Small-Body Database Browser: 85713 (1998 SS49)
  |url        = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2085713&cad=1
  |publisher  = [[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]]
  |accessdate = 18 January 2018}}</ref>

<ref name="MPC-object">{{cite web
  |title      = 85713 (1998 SS49)
  |work       = Minor Planet Center
  |url        = https://www.minorplanetcenter.net/db_search/show_object?object_id=85713
  |accessdate = 18 January 2018}}</ref>

<ref name="MPC-Circulars-Archive">{{cite web
  |title      = MPC/MPO/MPS Archive
  |work       = Minor Planet Center
  |url        = https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html
  |accessdate = 24 February 2018}}</ref>

<ref name="MPC-PHA-list">{{cite web
  |title      = List of the Potentially Hazardous Asteroids (PHAs)
  |work       = Minor Planet Center
  |url        = https://www.minorplanetcenter.net/iau/lists/t_phas.html
  |accessdate = 18 January 2018}}</ref>

<ref name="Mainzer-2011">{{cite journal
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  |arxiv      = 1109.6400
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<ref name="lcdb">{{cite web
  |title      = LCDB Data for (85713) 
  |publisher  = Asteroid Lightcurve Database (LCDB)
  |url        = http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=85713%7C
  |accessdate = 18 January 2018}}</ref>

<ref name="AKARI">{{cite journal
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  |first1     = Fumihiko |last1 = Usui
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  |date       = October 2011
  |title      = Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey
  |journal    = Publications of the Astronomical Society of Japan
  |volume     = 63
  |issue      = 5
  |pages      = 1117–1138
  |bibcode    = 2011PASJ...63.1117U
  |doi        = 10.1093/pasj/63.5.1117
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<ref name="WISE">{{cite journal
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  |date       = November 2011
  |title      = NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results
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  |issue      = 2
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  |bibcode    = 2011ApJ...741...90M
  |doi        = 10.1088/0004-637X/741/2/90
  |arxiv      = 1109.6407
  |s2cid = 35447010 }}</ref>

<ref name="Nugent-2016">{{cite journal
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  |first1     = C. R. |last1 = Nugent
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<ref name="Warner-2015h">{{Cite journal
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<ref name="Warner-2015c">{{Cite journal
  |author     = Warner, Brian D.
  |date       = January 2015
  |title      = Near-Earth Asteroid Lightcurve Analysis at CS3-Palmer Divide Station: 2014 June-October
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<ref name="Vaduvescu-2017">{{Cite journal
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  |doi        = 10.1007/s11038-017-9506-9
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<ref name="Veres-2015">{{cite journal
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}} <!-- end of reflist -->

== External links ==
* [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
* {{NeoDys|85713}}
* {{ESA-SSA|85713|1998SS49}}
* {{JPL small body|id=2085713}}

{{Minor planets navigator | |number=85713 |PageName={{mp|(85713) 1998 SS|49}} | }}
{{Small Solar System bodies}}

{{DEFAULTSORT:1998 SS49}}
[[Category:Apollo asteroids|085713]]
[[Category:Potentially hazardous asteroids|085713]]

{{Sourceattribution|(85713) 1998 SS49}}