1620 Geographos

Template:Short description Template:Use dmy dates {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = 1620 Geographos | image = {{#invoke:InfoboxImage|InfoboxImage|image=1620Geographos (Lightcurve Inversion).png|upright={{#if:||1.1}}|alt=}} | caption = Lightcurve-based 3D-model of Geographos | headerstyle = {{#if:#FFC2E0|background-color:#FFC2E0|background-color:#E0CCFF}} | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y

| header1 = Discovery<ref name="jpldata" />

| header10 = {{#if:|Designations|Designations}}

| header20 = Orbital characteristics{{#ifeq:|yes| (barycentric)}}<ref name="jpldata" />

| data21 = | data22 = {{#if:4 September 2017 (JD 2458000.5) |Epoch 4 September 2017 (JD 2458000.5)}} | data23 = {{#if:0 | Uncertainty parameter 0}} | label24 = Observation arc | data24 = 65.37 yr (23,875 days) | label25 = Earliest precovery date | data25 = 31 August 1951 | label26 = {{#switch:{{{apsis}}} |apsis|gee|barion|center|centre|(apsis)=Apo{{{apsis}}} |Ap{{#if:|{{{apsis}}}|helion}}}} | data26 = 1.6629 AU | label27 = Peri{{#if:|{{{apsis}}}|helion}} | data27 = 0.8276 AU | label28 = Peri{{#if:|{{{apsis}}}|apsis}} | data28 = | label29 = {{#switch:{{{apsis}}} |helion|astron=Ap{{{apsis}}} |Apo{{#if:|{{{apsis}}}|apsis}}}} | data29 = | label30 = Periastron | data30 = | label31 = Apoastron | data31 = | label32 = Template:Longitem | data32 = 1.2453 AU | label33 = Template:Longitem | data33 = | label34 = Eccentricity | data34 = 0.3354 | label35 = Template:Longitem | data35 = 1.39 yr (508 days) | label36 = Template:Longitem | data36 = | label37 = Template:Longitem | data37 = | label38 = Template:Longitem | data38 = 246.00° | label39 = Template:Longitem | data39 = Template:Deg2DMS / day | label40 = Inclination | data40 = 13.337° | label41 = Template:Longitem | data41 = | label42 = Template:Longitem | data42 = 337.20° | label43 = Template:Longitem | data43 = | label44 = Template:Longitem | data44 = | label45 = Template:Longitem | data45 = 276.90° | label46 = Template:Nowrap | data46 = | label47 = Satellite of | data47 = | label48 = Group | data48 = | label49 = {{#switch: |yes|true=Satellites |Known satellites}} | data49 = | label50 = Star | data50 = | label51 = Earth MOID | data51 = 0.0301 AUTemplate:·11.7 LD | label52 = Mercury MOID | data52 = | label53 = Venus MOID | data53 = | label54 = Mars MOID | data54 = | label55 = Jupiter MOID | data55 = | label56 = Saturn MOID | data56 = | label57 = Uranus MOID | data57 = | label58 = Neptune MOID | data58 = | label59 = T_Jupiter | data59 =

| header60 = Proper orbital elements

| label61 = Template:Longitem | data61 = {{#if: |{{{p_semimajor}}} AU}} | label62 = Template:Longitem | data62 = | label63 = Template:Longitem | data63 = | label64 = Template:Longitem | data64 = {{#if: |{{{p_mean_motion}}} deg Template:\yr}} | label65 = Template:Longitem | data65 = {{#if:|{{#expr:360/1 round 5}} yr
({{#expr:365.25*360/1 round 3}} d) }} | label66 = Template:Longitem | data66 = {{#if:|{{{perihelion_rate}}} arcsec Template:\yr }} | label67 = Template:Longitem | data67 = {{#if:|{{{node_rate}}} arcsec Template:\yr}}

| header70 = Template:Anchor{{#if:yes| Physical characteristics|Physical characteristics}}

| label71 = Dimensions | data71 = (5.0×2.0×2.1) ± 0.15 km<ref name="Hudson-1999" /> | label72 = Template:Longitem | data72 = Template:Val km<ref name="SIMPS" />
Template:Val km<ref name="Nugent-2015" />
Template:Val km<ref name="Nugent-2016" />
Template:Val km<ref name="lcdb" /><ref name="Harris-1998a" />
Template:Val km<ref name="Hudson-1999" /> | label73 = Template:Longitem | data73 = | label74 = Template:Longitem | data74 = | label75 = Template:Longitem | data75 = | label76 = Flattening | data76 = | label77 = Circumference | data77 = | label78 = Template:Longitem | data78 = | label79 = Volume | data79 = | label80 = Mass | data80 = | label81 = Template:Longitem | data81 = | label82 = Template:Longitem | data82 = | label83 = Template:Longitem | data83 = | label84 = Template:Longitem | data84 = | label85 = Template:Longitem | data85 = Template:Val h<ref name="Higgins-2008b" />
Template:Val hTemplate:Efn
Template:Val h<ref name="geneva-obs" />
Template:Val h<ref name="Skiff-2012a" />
Template:Val h<ref name="Warner-2016e" />
Template:Val h<ref name="Dunlap-1974" />
Template:Val h<ref name="Magnusson-1996" /><ref name="Kaasalainen-2001" />
Template:Val h<ref name="Hudson-1999" />
Template:Val h<ref name="Kwiatkowski-1995" /><ref name="Michalowski-1994" />
Template:Val h<ref name="Polishook-2009c" /> | label86 = Template:Longitem | data86 = | label87 = Template:Longitem | data87 = | label88 = Template:Longitem | data88 = | label89 = Template:Longitem | data89 = | label90 = Template:Longitem | data90 = | label91 = Template:Longitem | data91 = | label92 = Template:Longitem | data92 = | label93 = {{#if:yes |Template:Longitem |Albedo}} | data93 = Template:Val<ref name="lcdb" /><ref name="Harris-1998a" />
Template:Val<ref name="Nugent-2015" />
Template:Val<ref name="Nugent-2015" />
Template:Val<ref name="Nugent-2016" />
Template:Val<ref name="SIMPS" /> | label94 = Temperature | data94 =

| data100 = {{#if:|

Surface temp.	min	mean	max
{{{temp_name1}}}
{{{temp_name2}}}
{{{temp_name3}}}
{{{temp_name4}}}

}}

| label101 = Surface absorbed dose rate | data101 = | label102 = Surface equivalent dose rate | data102 = | label103 = Template:Longitem | data103 = Tholen = S<ref name="jpldata" />
SMASS = S<ref name="jpldata" /><ref name="lcdb" />Template:·S<ref name="Dandy-2003" />
B–V = 0.862<ref name="jpldata" />
B–V = Template:Val<ref name="Dandy-2003" />
U–B = 0.471<ref name="jpldata" />
V–R = Template:Val<ref name="Dandy-2003" />
V–I = Template:Val<ref name="Dandy-2003" /> | label104 = Template:Longitem | data104 = | label105 = Template:Longitem | data105 = | label106 = Template:Longitem | data106 = 15.09<ref name="lcdb" /><ref name="Harris-1998a" />Template:·15.41<ref name="Nugent-2016" />Template:·Template:Val<ref name="Veres-2015" />Template:·15.6<ref name="jpldata" /><ref name="SIMPS" /><ref name="Nugent-2015" /> | label107 = Template:Longitem | data107 =

| header110 = Atmosphere

| below = {{#if:||Template:Reflist }}

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1620 Geographos (Template:IPAc-en; provisional designation Template:Mp) is a highly elongated, stony asteroid, near-Earth object and potentially hazardous asteroid of the Apollo group, with a mean diameter of approximately Template:Convert. It was discovered on 14 September 1951, by astronomers Albert George Wilson and Rudolph Minkowski at the Palomar Observatory in California, United States.<ref name="MPC-object" /> The asteroid was named in honor of the National Geographic Society.<ref name="springer" />

Orbit and classificationEdit

File:Animation of 1620 Geographos orbit.gif

Animation of 1620 GeographosTemplate:'s orbit 2010-2020
Template:Legend2 Template:·Template:Legend2 Template:·Template:Legend2 Template:·Template:Legend2 Template:·Template:Legend2

Geographos orbits the Sun at a distance of 0.8–1.7 AU once every 1 years and 5 months (508 days). Its orbit has an eccentricity of 0.34 and an inclination of 13° with respect to the ecliptic.<ref name="jpldata" /> Its orbit is well-determined for the next several hundred years. Due to its high eccentricity, Geographos is also a Mars-crosser asteroid. The body's observation arc begins at Palomar, two weeks prior to its official discovery observation.<ref name="MPC-object" />

Close approachesEdit

As a potentially hazardous asteroid, Geographos has a minimum orbital intersection distance (MOID) with Earth of less than 0.05 AU and a diameter of greater than 150 meters. The Earth-MOID is currently Template:Convert, which translates into 11.7 lunar distances.<ref name=jpldata /> In 1994, Geographos made its closest approach to Earth in two centuries at 5.0 Gm – which will not be bettered until 2586.<ref name="Ostro-1996" />

Failed Clementine missionEdit

Geographos was to be explored by the U.S.'s Clementine mission which was launched in January 1994. However, a malfunction in the spacecraft ended the mission before it could approach the asteroid.<ref>NASA - Clementine</ref>

Physical characteristicsEdit

Spectral typeEdit

In the Tholen and SMASS classification, Geographos is an S-type asteroid.<ref name="jpldata" /> This means that it is highly reflective and composed of nickel-iron mixed with iron- and magnesium-silicates.

Rotation periodEdit

Since the 1970s, several rotational lightcurve of Geographos have been obtained from photometric observations. Lightcurve analysis gave a rotation period (retrograde sense of rotation) between 5.222 and 5.224 hours with a very high brightness variation between 1.02 and 2.03 magnitude (Template:Small).<ref name="Higgins-2008b" /><ref name="geneva-obs" /><ref name="Skiff-2012a" /><ref name="Warner-2016e" /><ref name="Dunlap-1974" /><ref name="Polishook-2009c" />Template:Efn

The Yarkovsky effect is causing a decrease in the orbital semimajor axis of Template:Val,<ref name="Rozitis-2014" /> while the YORP effect is increasing the asteroid's rotation at the rate of Template:Val.<ref>Template:Cite journal</ref>

Spin axisEdit

Several lightcurve were also modeled from the abundant photometric observations. In 1994 and 1995, Polish astronomers obtained a concurring period 5.223328 hours and found a spin axis of (54.0°, −52.0°) in ecliptic coordinates (λ, β) (Template:Small).<ref name="Michalowski-1994" /><ref name="Kwiatkowski-1995" /> Radiometric observations gave a period of 5.223327 hours and a pole of (55.0°, −46.0°).<ref name="Hudson-1999" /> Two other international studies obtained a period of 5.223326 hours and a pole at (56.0°, −47.0°) and (55.0°, −45.0°), respectively (Template:Small).<ref name="Magnusson-1996" /><ref name="Kaasalainen-2001" />

Shape and structureEdit

The light curve shows a high amplitude, indicative of its elongated shape, measuring 5.0×2.0×2.1 kilometers, which corresponds to a mean-diameter of 2.5 km.<ref name="Hudson-1999" />

The interior of the asteroid probably has a rubble-pile structure. The asteroid's high thermal inertia indicates the surface is most likely a mix of fine grains and large rocks and boulders.<ref name="Rozitis-2014" /> During the asteroid's close approach to Earth in 1994, a radar study of it was conducted by the Deep Space Network at the Goldstone Observatory, California. The resultant images show Geographos to be the most elongated object in the Solar System.<ref name="Ostro-1996" />

Diameter and albedoEdit

According to the observations with the Goldstone Observatory and the space-based surveys carried out by the Infrared Astronomical Satellite IRAS and the NEOWISE mission of the Wide-field Infrared Survey Explorer, Geographos measures between 1.77 and 2.56 kilometers in diameter and its surface has an albedo between 0.26 and 0.3258.<ref name="SIMPS" /><ref name="Nugent-2015" /><ref name="Nugent-2016" /><ref name="Harris-1998a" /><ref name="Hudson-1999" /> The Collaborative Asteroid Lightcurve Link adopts an albedo of 0.26 and a diameter of 2.5 kilometers based on an absolute magnitude of 15.09.<ref name="lcdb" />

NamingEdit

This minor planet was named after the National Geographic Society, in recognition of its contribution to astronomy by supporting the National Geographic Society – Palomar Observatory Sky Survey (NGS-POSS), which produced a photographic atlas of the entire northern sky in the 1950s. NGS-POSS was headed by the second discoverer, Rudolph Minkowski. The Greek word {{#invoke:Lang|lang}} means geographer (from geo– 'Earth' + {{#invoke:Lang|lang}} 'drawer/writer').<ref name="springer" /> The official Template:MoMP was published by the Minor Planet Center in August 1956 (Template:Small).<ref name="DoMP-Circular-dates" />

NotesEdit

Template:Notelist

ReferencesEdit

Template:Reflist

External linksEdit

NASA Asteroid Radar Research - Radar-Detected Asteroids: 1620 Geographos
Large amplitude fast rotator Template:Dead link Template:Cbignore (Yahoo Groups)
Asteroid Lightcurve Database (LCDB), query form (info Template:Webarchive)
Dictionary of Minor Planet Names, Google books
Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
Template:NeoDys
Template:ESA-SSA
Template:JPL small body

Template:Minor planets navigator

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