photometric observation of 107p/4015 wilson-harrington

Photometric Photometric Observation of Observation of

107P/4015 Wilson-107P/4015 Wilson-HarringtonHarrington

Seitaro UrakawaSeitaro Urakawa11, Shin-ichiro Okumura, Shin-ichiro Okumura11, Kota Nishiyama, Kota Nishiyama11, Tsuyoshi , Tsuyoshi SakamotoSakamoto11, Masateru Ishiguro, Masateru Ishiguro22, Kouhei Kitazato, Kouhei Kitazato33, Daisuke Kuroda, Daisuke Kuroda44, , Sunao HasegawaSunao Hasegawa55, Makoto Yoshikawa, Makoto Yoshikawa1,51,5

((11Japan Spaceguard Association, Japan Spaceguard Association, 22Seoul University, Seoul University, 33Aizu University, Aizu University, 44National Astronomical Observatory of Japan, National Astronomical Observatory of Japan, 55ISAS(Institute of Space ISAS(Institute of Space and Astronautical Science)/JAXA(Japan Aerospace Exploration Agency)and Astronautical Science)/JAXA(Japan Aerospace Exploration Agency)

우라카와 세이다로Сейтаро Уракаба

Outline Outline

Introduction Introduction Asteroid Explorer HayabusaAsteroid Explorer Hayabusa Primitive Body Missions of JapanPrimitive Body Missions of Japan 107P/4015 Wilson-Harrington107P/4015 Wilson-Harrington 　　 Observations Observations Data Reduction Data Reduction Results (Rotational Period; Rotational Direction; Results (Rotational Period; Rotational Direction;

Pole Direction; Shape Model ) Pole Direction; Shape Model ) SummarySummary

Welcome Home Welcome Home Asteroid ExplorerAsteroid Explorer Hayabusa Hayabusa

June 13, 2010 Asteroid explore Hayabusa return to the earth.


May 9, 2003: Lift off

Sep 12, 2005: Arrive asteroid Itokawa

Nov, 2005: Two times touch down and Nov, 2005: Two times touch down and collect the sample.collect the sample.


June 13 , 2010, at 10:54 (UT) Capsule release

June 13 , 2010, at 14:08 (UT) Touch down in Australia

Scientific Purpose of Hayabusa MissionScientific Purpose of Hayabusa Mission

Asteroids and comets preserve the condition at the Asteroids and comets preserve the condition at the birth of solar system.birth of solar system.

We can obtain a clue on the birth of solar system We can obtain a clue on the birth of solar system by analyzing the sampleby analyzing the sample in detail.in detail.

Primitive bodies (asteroids and comets) have not Primitive bodies (asteroids and comets) have not accepted much thermal influences since the early stage accepted much thermal influences since the early stage of solar system. In addition to it, the objects have not of solar system. In addition to it, the objects have not been weathered.been weathered.

Taxonomy of AsteroidsTaxonomy of AsteroidsInner asteroid belt:Inner asteroid belt:S-type asteroids are dominated.S-type asteroids are dominated.

S-type asteroid:S-type asteroid:Silicate componentSilicate component

Center asteroid belt:Center asteroid belt:C-type asteroids are dominated.C-type asteroids are dominated.

C-type asteroid:C-type asteroid:Carbonaceous componentCarbonaceous component

Outer asteroid belt (Trojan):Outer asteroid belt (Trojan):D-type asteroids increases.D-type asteroids increases.

D-type asteroid:D-type asteroid:More primitive component, More primitive component, Organic matter, Comet survivors!?Organic matter, Comet survivors!?

Primitive Body Missions of JapanPrimitive Body Missions of Japan

C-typeC-type S-typeS-type

D-type orD-type orDormant CometsDormant Comets

More Primitive Body

More Difficult Mission

HayabusaHayabusa ItokawaItokawa Hayabusa 2Hayabusa 2

1999 JU31999 JU3 Hayabusa Mk2Hayabusa Mk2Wilson-HarringtonWilson-Harrington(Candidate)(Candidate)

Hayabusa Mk2 missionHayabusa Mk2 mission

New Explorer (Development of new ion engine)New Explorer (Development of new ion engine)

Candidate of target: D-type or Dormant comet Candidate of target: D-type or Dormant comet (for example 107P/4015 Wilson-Harrignton)(for example 107P/4015 Wilson-Harrignton)

In order to design the mission, the physical properties of WH In order to design the mission, the physical properties of WH (rotational period, rotational direction, pole direction, shape) (rotational period, rotational direction, pole direction, shape)

are needed.are needed.

Such physical properties are obtainedSuch physical properties are obtained by the photometric observation (the light-curve of WH).by the photometric observation (the light-curve of WH).

The mission can provide insights on the unknown link The mission can provide insights on the unknown link between asteroids and comets.between asteroids and comets.

107P/4015 Wilson-Harrington 107P/4015 Wilson-Harrington

Semi-major axis Semi-major axis 　　 22.638AU.638AUEccentricityEccentricity 　　　　　　　　 0.6240.624InclinationInclination 　　 22.78°.78°Argument of perihelionArgument of perihelion 　　 9191.25°.25°Longitude of ascending nodeLongitude of ascending node 　　 270270.57°.57°Period Period 　　　　　　　　　　　　 44.28 year.28 year

Fernandez et al. 1997

A comet was discovered in 1949 A comet was discovered in 1949 at the Palomar observatory. The at the Palomar observatory. The faint tail can see. The comet faint tail can see. The comet named as 107P/Wilson-named as 107P/Wilson-Harrington. However, the comet Harrington. However, the comet was lost by the insufficient was lost by the insufficient observation.observation.

A near earth asteroid (4015) A near earth asteroid (4015) was discovered in 1979.was discovered in 1979.

The continuous observations The continuous observations identified that 107P/Wilson-identified that 107P/Wilson-Harrington and asteroid Harrington and asteroid (4015) were the same object.(4015) were the same object.

Past Study of Wilson-Harrington Past Study of Wilson-Harrington

P=6.1h Osip and Campine1995

P=3.556h Harris and Young 1983

Spectral type: C-typeSpectral type: C-type (NASA/JPL database)(NASA/JPL database)

Rotational period: two solutions Rotational period: two solutions for 0.148 day (3.556 hour) or for 0.148 day (3.556 hour) or 0.254 ±0.002day (6.1 ±0.05 hour)0.254 ±0.002day (6.1 ±0.05 hour)

Rotational direction: unknownRotational direction: unknown

Pole direction: unknownPole direction: unknown

Shape: unknownShape: unknown

ObservationsObservations

University of Hawaii 2.2m (PI: Dr.Ishiguro)Dec 18, 2009

Kiso Observatory 1.05m (PI: Dr.Kitazato)Aug 17, 19, 20, Dec 12, 2009 / 4 days

Lulin Observatory 1.0m (PI: Dr.Kitazato)Dec 7-10, 2009 / 4 days

Okayama Astrophysical Observatory 0.5m (PI: Dr.Kuroda)Nov 7, 2009 – Dec 21, 2009 / 19 days

Bise Spaceguard Center 1.0mSep 6, 2009 – Mar 11, 2010 / 43 days

Bias and flat field calibrationBias and flat field calibration Aperture photometry (IRAF)Aperture photometry (IRAF) Relative photometry by using reference starsRelative photometry by using reference stars

Data ReductionData Reduction

Rotational PeriodRotational PeriodMethod of period analysis: Lomb-Scargel Periodgram (Lomb 1976 & Scargel 1982).We use the photometric precise data (Data of December).

Candidate 1:0.2592 day



Rotational Period Rotational Period Results: 0.2979day (7.15 h)

*Unusual six-peak light-curve(The light-curve represented the cross section area of asteroid. When the shape of asteroid is an ellipsoidal body, the shape of typical light-curve is double-peak.)

*The past data consist with the period of candidate 2 (0.2979 day). When we made the folded light-curve with other candidates, the shape of light-curve was not good.

Rotational DirectionRotational DirectionAppearance Rotation(Red circled asteroid)

True Rotation(Green circled asteroid)

Observer

Prograde rotation

Retrograde rotation

Appearance Rotation :The rotation is determined by the light-curve.

True Rotation :The rotation is slightlyshorter or longer than theappearance rotation.

Retrograde rotation:The true period is longer than the appearance period.

Prograde rotation:The true period is shorter than the appearance period.

Asteroid

≠

Rotational DirectionRotational Direction

Prograde Retrograde

We calibrated the difference between the appearance rotation and the true rotation.

Assume prograde rotation Assume retrograde rotation

The light-curve shape is not good. The light-curve shape is good.

Determination of Pole Direction by Determination of Pole Direction by Epoch MethodEpoch Method

Epoch method (Magnusson 1986) : Phase shift in the light-curve→ Pole direction

We search θ value which minimizes the residuals between the left-hand and the right-hand.

Phase shift (Observational values)

Phase shift (Theoretical values)

(T : The time when a specific feature (for example, the flux minimum) appears, P: Rotational Period, n: Number of rotation during the observation term, θ: A vector that is related with the pole direction.

Determination of Pole Direction by Determination of Pole Direction by Epoch MethodEpoch Method

Candidate 1λ: 320°±15β: -20 °±15

Candidate 2λ= 　 140±15°β= -20±15

Shape ModelShape Model

Light-curve Light-curve →→ 　　 Shape Model Shape Model (The software is developed and distributed by Kassalainen et (The software is developed and distributed by Kassalainen et al. 1992.)al. 1992.)

edge on pole onLike hexagonal shape

Summary Summary

We introduced the primitive body mission of Japan. We introduced the primitive body mission of Japan. →→The target candidate of Hayabusa Mk2 is 107P/4015 Wilson-The target candidate of Hayabusa Mk2 is 107P/4015 Wilson-

Harrignton.Harrignton. We found the following properties from the light-curve of WH,We found the following properties from the light-curve of WH, Rotational period: 0.2979 day (7.15 hour)Rotational period: 0.2979 day (7.15 hour)→→Hayabusa Mk2 can Hayabusa Mk2 can

touch down. touch down. Rotational direction: Retrograde rotationRotational direction: Retrograde rotation Pole direction: (λ,βPole direction: (λ,β ）） =(320°,-20 °) or (140°,-20 °)=(320°,-20 °) or (140°,-20 °) Shape: Like hexagonal shapeShape: Like hexagonal shape In order to calculate the precise rotational period, it is important In order to calculate the precise rotational period, it is important

to observe the target from multi-longitude location. WH is not to observe the target from multi-longitude location. WH is not the only target. There is the possibility of the target change. We the only target. There is the possibility of the target change. We would like to collaborate with Maidanak observatory and other would like to collaborate with Maidanak observatory and other observatories for the next ground-base observation campaign. observatories for the next ground-base observation campaign.

photometric observation of 107p/4015 wilson-harrington

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