View source for 253 Mathilde

{{Infobox Planet <!-- Additional parameters for this template  are available at [[Template:Infobox Planet]]. -->

| bgcolour=#FFFFC0
| name=253 Mathilde
| image= (253) mathilde.jpg
| caption=NASA image of 253 Mathilde
| discoverer=[[Johann Palisa]]
| discovered=November 12, 1885
| alt_names=A915 TN; {{mp|1949 OL|1}}
| mp_category=[[Asteroid belt|Main belt]]
| epoch=January 30, 2005 ([[Julian day|JD]]&nbsp;2453400.5)
| orbit_ref=<ref name="jpl">Unless otherwise noted, parameters are per: {{cite web
 | last=Yeomans | first=Donald K. | date=August 29, 2003
 | url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=253
 | title=253 Mathilde
 | work=JPL Small-Body Database Browser
 | publisher=NASA | accessdate=2007-08-29 }}</ref>
<!--
  NOTE: Only 6 digits of the orbital elements are retained here.
        More detailed values are available from the ref.
-->
| aphelion=501.334&nbsp;[[Giga|G]][[metre|m]]<br />3.35121&nbsp;[[Astronomical unit|AU]]
| perihelion=290.564&nbsp;Gm<br />1.94230&nbsp;AU
| semimajor=395.949&nbsp;Gm<br />2.64676&nbsp;AU
| eccentricity=0.266157
| period=1572.787&nbsp;[[day|d]]
<br />(4.31&nbsp;[[Julian year (astronomy)|yr]])
| mean_anomaly=111.960[[degree (angle)|°]]
| inclination=6.738°
| asc_node=179.633°
| arg_peri=157.475°
| avg_speed=17.98 km/[[second|s]]<ref>For semi-major axis ''a'', orbital period ''T'' and eccentricity ''e'', the average orbital speed is given by:
:<math>\begin{align}
v_o & = \frac{2\pi a}{T}\left[1-\frac{e^2}{4}-\frac{3e^4}{64} - \dots \right] \\
    & = 18.31\ \mbox{km/s} \left[ 1 - 0.0177 - 0.00008 - \cdots \right] \\
    & \approx 17.98\ \mbox {km/s} \\
\end{align}\!\,</math>
For the circumference of an ellipse, see:
{{cite book
 | author=H. St̀eocker, J. Harris | year=1998
 | title=Handbook of Mathematics and Computational Science
 | url=https://archive.org/details/handbookofmathem00harr | page= 386 | publisher=Springer
 | isbn=0-387-94746-9 }}</ref>
| dimensions=52.8<ref name="jpl"/>&nbsp;[[kilometre|km]]<br />(66×48×46&nbsp;km<ref name="icarus140"/>)
| mass=1.033(±0.044)×10<sup>17</sup><ref name="Yeomans 1997"/>&nbsp;[[kilogram|kg]]
| density=1.3<ref name="Yeomans 1997"/>&nbsp;g/[[cubic centimetre|cm³]]
| surface_grav=0.0025<ref>With asteroid mass ''m'', radius ''r'' and ''G'' equal to the [[gravitational constant]], [[Newton's law of universal gravitation]] gives an average surface gravity ''g'' of:
:<math>\begin{align}
g & = G \frac{m}{r^2} \\
  & = 6.67 \times 10^{-11} \mbox{m}^3/\mbox{kg s}^2 \cdot \frac{1.03 \times 10^{17}\ \mbox{kg}}{(5.28 \times 10^4\ \mbox{m})^2} \\
  & = 0.0025\ \mbox{m/s}^2 \\
\end{align}</math></ref>&nbsp;m/s²
| escape_velocity=16.2<ref>For surface gravity ''g'' and radius ''r'', the escape velocity is:
:<math>\begin{align}
v_e & = \sqrt{2gr} \\
    & = \sqrt{2 \cdot 0.0025\ \mbox{m/s}^2 \cdot 52800\ \mbox{m}} \\
    & = 16.2\ \mbox{m/s} \\
\end{align}</math></ref>&nbsp;m/s
| rotation=17.406±0.010<ref>{{cite journal
 | author=Stefano Mottola | display-authors = etal
 | title=The slow rotation of 253 Mathilde
 | journal=Planetary and Space Science
 | year=1995 | volume=43 | issue=12 | pages=1609–1613
 | doi = 10.1016/0032-0633(95)00127-1
 | bibcode = 1995P&SS...43.1609M
 | url=http://adsabs.harvard.edu/abs/1995P&SS...43.1609M
 | accessdate=2007-02-04 }}</ref>&nbsp;[[day|d]]<br />(17&nbsp;[[day|d]] 9&nbsp;[[hour|h]] 45&nbsp;[[minute|min]])
| spectral_type=[[C-type asteroid|Cb]]<ref name="jpl"/>
| abs_magnitude=10.20<ref name="jpl"/>
| albedo=0.0436<ref name="jpl"/>
| single_temperature=~174<ref>For asteroid albedo ''α'', semimajor axis ''a'', [[solar luminosity]] ''<math>L_0</math>'', [[Stefan-Boltzmann constant]] ''σ'' and the asteroid's [[infrared]] emissivity ''ε'' (~0.9), the approximate mean temperature ''T'' is given by:
:<math>\begin{align}
T & = \left ( \frac{(1 - \alpha) L_0}{\epsilon \sigma 16 \pi a^2} \right )^{\frac{1}{4}} \\
  & = \left ( \frac{(1 - 0.0436) (3.827 \times 10^{26}\ \mbox{W})} {0.9 (5.670 \times 10^{-8}\ \mbox{W/m}^2\mbox{K}^4) 16 \cdot 3.142 (3.959 \times 10^{11}\ \mbox{m})^2} \right )^{\frac{1}{4}} \\
  & = 173.7\ \mbox{K}
\end{align}</math>

See: {{cite book
 | author=Torrence V. Johnson, Paul R. Weissman, Lucy-Ann A. McFadden
 | year=2007 | title=Encyclopedia of the Solar System
 | url=https://archive.org/details/bwb_W8-BGD-739
 | page= [https://archive.org/details/bwb_W8-BGD-739/page/294 294] | publisher=Elsevier
 | isbn=978-0-12-088589-3 }}</ref> [[kelvin|K]]
}}

'''253 Mathilde''' is a [[Asteroid belt|main belt]] [[asteroid]] found by [[Johann Palisa]] in 1885. It has a fairly [[ellipse|elliptical]] [[orbit]] that takes more than four years to circle the [[Sun]]. This asteroid has an unusually slow rate of rotation, taking 17.4&nbsp;days to complete a 360° [[wikt:revolution|revolution]] about its axis. It is a primitive [[C-type asteroid]], which means the surface has lots of [[carbon]]; giving it a dark surface that reflects only 4% of the light that falls on it.<ref name="flyby"/>

This asteroid was visited by the [[NEAR Shoemaker]] spacecraft during June 1997, on its way to asteroid [[433 Eros]].  The spacecraft took pictures of one side of the asteroid, finding many big craters that have gouged out depressions in the surface.  It is currently the biggest asteroid to be visited by a spacecraft, and the first C-type asteroid to be so explored.

== Description ==
[[File:253 Mathilde side.png|right|thumb|300px|One of the big craters on 253 Mathilde. ''[[NASA]] image''.]]

253 Mathilde is very dark.<ref>{{cite web | last=Pon | first=Brian | date=June 30, 1999 | url=http://eetd.lbl.gov/HeatIsland/Pavements/Albedo/ | title=Pavement Albedo | publisher=Heat Island Group | accessdate=2007-08-27 | archive-date=2007-08-29 | archive-url=https://web.archive.org/web/20070829153207/http://eetd.lbl.gov/HeatIsland/Pavements/Albedo/ | url-status=dead }}</ref> The asteroid has a number of very big [[crater]]s, with the individual craters being named for [[coal]] fields and basins around the world.<ref>{{cite web
 | last=Blue | first=Jennifer | date=August 29, 2007
 | url=http://planetarynames.wr.usgs.gov/append6.html#Asteroids
 | title=Categories for Naming Features on Planets and Satellites
 | publisher=USGS | accessdate=2007-08-29 }}</ref> The two biggest craters, Ishikari (29.3&nbsp;km) and Karoo (33.4&nbsp;km), are as wide as the asteroid's average radius.<ref name="icarus140">{{cite journal
 | author=J. Veverka | display-authors = etal
 | title=NEAR Encounter with Asteroid 253 Mathilde: Overview
 | journal=Icarus | year=1999 | volume=140 | issue = 1
 | pages=3–16
 | doi = 10.1006/icar.1999.6120
 | bibcode = 1999Icar..140....3V
 | url=http://adsabs.harvard.edu/abs/1999Icar..140....3V
 | accessdate=2007-08-29 }}</ref> The impacts appear to have blown big volumes off the asteroid, as suggested by the angular edges of the craters.<ref name="flyby">{{cite web
 | last=Williams | first=David R.
 | date=December 18, 2001
 | url=http://nssdc.gsfc.nasa.gov/planetary/mission/near/near_mathilde.html
 | title=NEAR Flyby of Asteroid 253 Mathilde
 | publisher=NASA | accessdate=2006-08-10 }}</ref>

The density measured by NEAR Shoemaker, 1,300&nbsp;kg/m³, is less than half that of a normal carbonaceous chondrite; this may indicate that the asteroid is very loosely packed rubble pile (an asteroid that has been broken apart by a collision and pulled back together by [[gravity]]).<ref name="Yeomans 1997">{{cite journal
 | author=D. K. Yeomans | display-authors = etal
 | title=Estimating the mass of asteroid 253 Mathilde from tracking data during the NEAR flyby
 | journal=[[Science (journal)|Science]]
 | volume=278 | issue=5346 | year=1997 | pages=2106–9
 | doi = 10.1126/science.278.5346.2106
 | pmid = 0009405343
 | url=http://www.sciencemag.org/cgi/content/full/278/5346/2106
 | accessdate=2007-08-29 }}</ref> The same is true of several C-type asteroids studied by ground-based telescopes with [[adaptive optics]] systems ([[45 Eugenia]], [[90 Antiope]], [[87 Sylvia]] and [[121 Hermione]]). Up to 50% of the volume inside of 253 Mathilde has open space. However, the existence of a 20-km-long scarp may indicate that the asteroid does have some structural strength, so it could contain some big internal components. The low interior density is an inefficient transmitter of impact shock through the asteroid, which also helps to preserve the surface features to a high degree.<ref name="icarus140"/>

Mathilde's [[orbit]] is [[eccentricity (orbit)|eccentric]], taking it to the farther reaches of the Main belt. Nonetheless, the orbit lies between the orbits of [[Mars (planet)|Mars]] and [[Jupiter (planet)|Jupiter]]; it does not cross the planetary orbits. It also has one of the slowest rotation periods of the known asteroids — most asteroids have a rotation period in the range of 2 – 24 hours.<ref>{{cite web
 | last=Lang
 | first=Kenneth R.
 | year=2003
 | url=http://ase.tufts.edu/cosmos/view_chapter.asp?id=15&page=3
 | title=2. Asteroids and meteorites, Size, color and spin
 | work=NASA's Cosmos
 | publisher=NASA
 | accessdate=2007-08-29
 | archive-date=2012-08-06
 | archive-url=https://www.webcitation.org/69io1CLu5?url=http://ase.tufts.edu/cosmos/view_chapter.asp?id=15
 | url-status=dead
 }}</ref> Because of the slow rotation rate, NEAR Shoemaker was only able to take pictures of 60% of the asteroid's surface. The slow rate of rotation may been accounted for by a moon orbiting the asteroid, but a search of the NEAR images revealed none bigger than 10&nbsp;km in diameter out to 20 times the radius of 253 Mathilde.<ref>{{cite journal
 | author=W. J. Merline | display-authors = etal
 | title=Search for Satellites of 253 Mathilde from Near-Earth Asteroid Rendezvous Flyby Data
 | journal=Meteoritics & Planetary Science
 | year=1998 | volume=33 | pages=A105
 | bibcode = 1998M&PSA..33..105M
 | url=http://adsabs.harvard.edu/abs/1998M&PSA..33..105M
 | accessdate=2007-08-29 }}</ref>

== References ==
{{Reflist}}

== Other websites ==
{{Commons|(253) Mathilde|253 Mathilde}}
* {{cite web
 | author=Bowell, Ted; and Koehn, Bruce
 | date=September 2, 2007
 | url=ftp://ftp.lowell.edu/pub/elgb/astorb.html
 | title=The Asteroid Orbital Elements Database
 | publisher=Lowell Observatory
 | accessdate=2007-09-02
 }}{{Dead link|date=June 2021 |bot=InternetArchiveBot |fix-attempted=yes }}
* {{cite web
 | author=Staff | date=August 28, 2007
 | url=http://cfa-www.harvard.edu/iau/lists/NumberedMPs.html
 | title=Discovery Circumstances: Numbered Minor Planets
 | publisher=Minor Planet Center | accessdate=2007-09-02 }}
* {{cite news
 | last=Hall | first=Alan | date=June 30, 1997
 | title=NEAR-ing Mathilde | publisher=Scientific American
 | url=http://www.sciam.com/article.cfm?articleID=000944D0-BE16-1CF3-93F6809EC5880000
 | accessdate=2007-08-29 }}

{{MinorPlanets Navigator|252 Clementina|254 Augusta}}
{{Small Solar System bodies}}

{{DEFAULTSORT:Mathilde}}
[[Category:Asteroids]]