153 Hilda

{{Infobox planet

| name= 153 Hilda

| image= Hilda-LB1-mag14.jpg

| image_scale =

| caption= Star field showing Hilda (apmag 14.2)

| background= #D6D6D6

| minorplanet= yes

| mpc_name= (153) Hilda

| alt_names= A875 VC; 1935 GD

| pronounced= {{IPAc-en|'|h|I|l|d|@}}{{dict.com|Hilda}}

| adjective= Hildian {{IPAc-en|'|h|I|l|d|i|@|n}}Bhattacharya & Lichtman (2016) Solar Planetary Systems, p. 6

| discovery_ref=

| discoverer = J. Palisa

| discovery_site = Austrian Naval Obs.

| discovered= 2 November 1875

| mp_category= Main belt (Hilda)

| orbit_ref=

| epoch= 31 July 2016 (JD 2457600.5)

| observation_arc= 121.05 yr (44215 d)

| uncertainty= 0

| semimajor= {{cvt|3.9783|AU|Gm}}

| eccentricity= 0.13971

| period={{cvt|2898.3|days|years|order=flip}} 7.94 yr (2898.3 d)

| inclination= 7.8249°

| perihelion= {{cvt|3.4225|AU|Gm}}

| aphelion= {{cvt|4.5341|AU|Gm|lk=on}}

| asc_node= 228.16°

| arg_peri= 38.617°

| mean_anomaly= 51.690°

| mean_motion= {{Deg2DMS|0.12421|sup=ms}} / day

| jupiter_moid= {{Convert|0.569657|AU|Gm|abbr=on}}

| tisserand= 3.023

| dimensions= {{val|170.63|3.3|ul=km}}

| mass= ~5.2{{e|18}} kg

| escape_velocity= ~ 6 m/s

| abs_magnitude= 7.48

| rotation= {{Convert|5.9587|h|d|abbr=on|lk=on}}

| albedo= {{val|0.0618|0.002}}

| spectral_type= P

}}

153 Hilda is a large asteroid in the outer main belt, with a diameter of 170 km. The spectrum matches that of a P-type asteroid. It was discovered by Johann Palisa on 2 November 1875, from the Austrian Naval Observatory at Pula, now Croatia. The name was chosen by the astronomer Theodor von Oppolzer, who named it after one of his daughters.{{cite book|last=Schmadel|first=Lutz D.|title=Dictionary of Minor Planet Names|url=https://books.google.com/books?id=KWrB1jPCa8AC&pg=PA29|year=2003|publisher=Springer Science & Business Media|isbn=978-3-540-00238-3|page=29}} It is the largest member of the hilda family, a collisional family of asteroids in the Hilda region.

Orbit and family

File:HildasOrbitWithLagrangePointsLousy.ogv (red). The open red circles are the Jovian Lagrange points that Hilda approaches.Based on orbital data from the year 2000. Hilda seldom approaches the Lagrangians exactly.]]

Hilda gives its name to an asteroid group called the Hilda group (or Hildas for short). It is not a true asteroid family, since the members are not physically related, but rather share similar orbital elements. The Hildas are locked in a 2:3 orbital resonance with Jupiter;{{cite journal

|last=Brož |first=M.

|author2=Vokrouhlický, D.

|title=Asteroid families in the first-order resonances with Jupiter

|journal=Monthly Notices of the Royal Astronomical Society

|volume=390 |issue=2 |pages=715–732 |year=2008

|doi=10.1111/j.1365-2966.2008.13764.x

|doi-access=free

|bibcode=2008MNRAS.390..715B|arxiv=1104.4004|s2cid=53965791

}} since Jupiter takes 11.9 years to orbit the Sun while Hilda takes 7.9 years, Jupiter orbits the Sun twice for every 3 orbits that Hilda completes. There are over 1,100 other objects known to be in a 2:3 resonance with Jupiter. The asteroid is, however, the largest member of the ancient physically related Hilda family within the dynamical group of the same name.

The orbital plane of 153 Hilda is inclined at an angle of 7.82° to the plane of the ecliptic. It has an orbital eccentricity (ovalness) of 0.13971. Multiple light curves of the asteroid provide a consistent rotation period of approximately {{val|5.9585|u=hours|fmt=commas}}