Research at the Centennial Observatory
Although the primary mission of the Centennial Observatory is to provide visitors with opportunities to experience the universe visually through telescopes, the facility is also used for astronomical research. The main research focus is the
determination of asteroids' sizes and the refinement of their orbits via stellar occultation .
The method is straightforward: A precise measurement of how long a distant star's light is occulted (blocked) by a passing asteroid, together with the asteroid's previously-determined distance and speed, allows the asteroid's diameter to
be calculated (by distance = rate x time). This measurement is accomplished via video photometry: video from a high-sensitivity camera attached to the telescope passes through a GPS-based device which "stamps" each video frame with the time (down
to millisecond precision). The video is analyzed with software that precisely measures the intensity of the target star in each video frame and assigns it a numerical relative brightness value. The light curve (a graph of brightness vs.
time—see fig. 3, below) reveals the duration of the occultation.
Fig. 1: Predicted shadow path of asteroid (105) Artemis , as cast on Earth by HIP 62736, a mag. 8.7 star in Virgo, on 11 April 2017. The northward-moving shadow was expected to pass
east of the Centennial Observatory, but uncertainty in the asteroid's precise orbital path allowed for a 26.3% chance that the shadow would pass over Twin Falls (which it did).
With several astronomers observing the same event from different location, the size and shape of the asteroid's shadow (identical to that of the asteroid itself, since stars are so distant that their light reaches Earth on essentially-parallel paths)
may be mapped out.
Fig. 2: Profile of asteroid (105) Artemis as determined by its occultation of HIP 62736 on 11 April 2017. Diagonal lines represent the star's apparent path, relative to the asteroid, as seen by observers at different locations. The
widths of the gaps ("chords") are determined by the duration of HIP 62736's disappearance as recorded by each observer. The Centennial Observatory's chord is cyan, at far right. The asteroid passed a bit to the southwest of
its predicted path (dotted line). (Note the 100 km scale bar at bottom.)
Since asteroids' exact orbits (like all measured quantities) are imperfectly known, their shadows (cast by starlight) take paths across the Earth whose precise location is uncertain. While many asteroid occultation observers utilize small,
portable instruments which allow them to travel to locations where a given asteroid's shadow is most likely to pass, this option is not available for the Centennial Observatory's permanently-mounted 24" (0.6m) telescope. Therefore we observe
many occultations, with probabilities ranging from near-certainty (weather notwithstanding) to less than 1-in-2000, to increase the frequency of success. To date, roughly one out of every nine occultation observations conducted at the Centennial
Observatory (not including those which were clouded out) has resulted in seeing the target star temporarily vanish as the asteroid obscures it. It should be noted that close misses can also be scientifically useful, as they may also help constrain the
asteroid's shape and path (e.g. the red chord at far left in fig. 2).
Fig. 3: Light curve of the 11 April 2017 (105) Artemis occultation, as derived by photometric video analysis. The jagged shape of the curve is due to a combination of signal noise and atmospheric distortion. For just over four seconds,
the light of HIP 62736 was blocked by (105) Artemis, causing the signal to drop by around 85% (from the combined light of the star and asteroid, to the light of the much fainter asteroid alone plus background sky glow).
The Centennial Observatory's first asteroid occultation observation was conducted on 24 August 2012, when asteroid (1585) Union cast its shadow from the star TYC 5777-010444-1 onto the Earth. No occultation was seen (i.e. the shadow missed
Twin Falls). All subsequent "positives" (timings performed when the Centennial Observatory was in an asteroid's stellar shadow) are listed below, in reverse chronological order.
Click on the date for a map of the asteroid's predicted shadow path. Click on the asteroid name for a profile of the asteroid showing all observers' chords (star tracks relative to the asteroid as seen from different locations). Click on
the star name for a graph of the Centennial Observatory's photometric data. Click on the observers' names for a map of their locations.
Positive Asteroid Occultations Recorded at theCentennial Observatory
Date (GMT) Asteroid Star Prob. Observers* Notes
29 Feb 2024
(135) Hertha
TYC 1226-01828-1
100.0%
C. Anderson
03 Feb 2024
(4460) Bihoro
UCAC4 702-036781
100.0%
C. Anderson
31 Jan 2024
(37853) Danielbarbier
UCAC4 591-027793
100.0%
C. Anderson
First measurement by occultation since discovery (1998).
29 Jan 2024
(26369) 1999 CG62
UCAC4 455-035613
100.0%
C. Anderson, K. Thomason, R. Showers
First measurement by occultation since discovery (1999).
05 Jan 2024
(299256) 2005 NS11
UCAC4 463-003420
6.7%
C. Anderson, K. Dan
First measurement by occultation since discovery (2005).
05 Dec 2023
(29853) 1999 FZ26
UCAC4 526-018884
84.3%
C. Anderson
First measurement by occultation since discovery (1999).
06 Oct 2023
(607) Jenny
UCAC4 556-044188
100.0%
C. Anderson
First measurement by occultation since discovery (1906).
29 Sep 2023
(1700) Zvezdara
UCAC4 313-117121
100.0%
C. Anderson
27 Aug 2023
(2249) Yamamoto
UCAC4 391-132618
100.0%
C. Anderson
First measurement by occultation since discovery (1942).
15 Aug 2023
(32153) Laurenmcgraw
UCAC4 410-141831
10.9%
C. Anderson
First measurement by occultation since discovery (2000).
16 Jul 2023
(76) Freia
UCAC4 348-090255
99.9%
C. Anderson
13 Jul 2023
(242) Kriemhild
UCAC4 413-080607
36.3%
C. Anderson
16 Jun 2023
(533) Sara
UCAC4 384-100263
97.3%
C. Anderson, R. Mayer
15 Jun 2023
(104) Klymene
UCAC4 327-084941
100.0%
C. Anderson
30 May 2023
(1057) Wanda
UCAC4 338-150100
10.3%
C. Anderson
12 May 2023
(203) Pompeja
UCAC4 316-221281
99.1%
C. Anderson
12 May 2023
(165137) 2000 KM79
HIP 96351
5.3%
C. Anderson
First measurement by occultation since discovery (2000).
11 May 2023
(2) Pallas
HIP 39848
11.0%
C. Anderson, R. Mayer
03 May 2023
(137) Meliboea
UCAC4 405-061012
90.3%
C. Anderson
30 Apr 2023
(4424) Arkhipova
G184411.6-071742
38.5%
C. Anderson
First measurement by occultation since discovery (1967).
07 Mar 2023
(5524) Lecacheux
UCAC4 410-061525
59.7%
C. Anderson
First measurement by occultation since discovery (1991).
04 Mar 2023
(505) Cava
TYC 2451-01245-1
85.9%
C. Anderson, R. Mayer
03 Feb 2023
(957) Camelia
UCAC4 423-049421
100.0%
C. Anderson
First measurement by occultation since discovery (1921).
22 Nov 2022
(195415) 2002 GJ40
UCAC4 540-009261
6.7%
C. Anderson
Jovian Trojan asteroid. First measurement by occultation since discovery (2002).
20 Nov 2022
(13556) 1992 OY7
UCAC4 594-009821
10.1%
C. Anderson
31 Oct 2022
(645) Agrippina
UCAC4 614-027481
18.1%
C. Anderson
21 Oct 2022
(3046) Molière
TYC 178-00936-1
6.0%
C. Anderson
First measurement by occultation since discovery (1960).
17 Oct 2022
(3415) Danby
UCAC4 370-183373
15.9%
C. Anderson
25 Sep 2022
(783) Nora
UCAC4 345-164371
99.8%
C. Anderson, R. Mayer, K. Thomason, R. Showers
20 Sep 2022
(29877) 1999 GL17
UCAC4 398-002437
20.4%
C. Anderson
First measurement by occultation since discovery (1999).
06 Sep 2022
(211) Isolda
UCAC4 535-003303
85.5%
C. Anderson, K. Thomason, R. Showers, R. Vega
08 Aug 2022
(1027) Aesculapia
UCAC4 326-161559
98.2%
C. Anderson
First measurement by occultation since discovery (1923).
12 Jul 2022
(238) Hypatia
UCAC4 423-071263
100.0%
C. Anderson
09 Jul 2022
Titan (Saturn VI)
HIP 107569
42.3%
C. Anderson
Brightness surges during ingress/egress due to thermal inversion layer in Titan's atmosphere.
23 Apr 2022
(88) Thisbe
TYC 6151-01340-1
100.0%
C. Anderson
22 Feb 2022
(2520) Novorossijsk
UCAC4 604-023871
39.8%
C. Anderson
First measurement by occultation since discovery (1976).
18 Feb 2022
(350) Ornamenta
TYC 6248-01259-1
100.0%
C. Anderson
18 Feb 2022
(657) Gunlod
UCAC4 523-047997
66.8%
C. Anderson
16 Feb 2022
(1330) Spiridonia
UCAC4 444-057461
51.8%
C. Anderson
01 Feb 2022
(4691) Toyen
UCAC4 607-037549
40.3%
C. Anderson
First measurement by occultation since discovery (1983).
28 Jan 2022
(284) Amalia
UCAC4 508-039509
100.0%
C. Anderson
18 Jan 2022
(17872) 1998 SP22
HIP 11728
16.0%
C. Anderson
First measurement by occultation since discovery (1998).
10 Jan 2022
(886) Washingtonia
UCAC4 443-059137
100.0%
C. Anderson
09 Jan 2022
(13851) 1999 XB94
UCAC4 563-020668
5.8%
C. Anderson
First measurement by occultation since discovery (1999).
07 Jan 2022
(1572) Posnania
UCAC4 657-026362
75.5%
C. Anderson
First measurement by occultation since discovery (1949).
04 Dec 2021
(923) Herluga
UCAC4 450-027370
38.0%
C. Anderson
29 Nov 2021
(212) Medea
UCAC4 593-015827
100.0%
C. Anderson
10 Nov 2021
(751) Faïna
UCAC4 582-041611
75.9%
C. Anderson
05 Oct 2021
(270) Anahita
UCAC4 570-023329
100.0%
C. Anderson
04 Sep 2021
(740) Cantabia
UCAC4 338-146452
77.2%
C. Anderson, D. West
31 Aug 2021
(2826) Ahti
UCAC4 610-022703
73.0%
C. Anderson
First measurement by occultation since discovery (1939).
12 Aug 2021
(850) Altona
UCAC4 337-196499
99.4%
C. Anderson, R. Jones
20 Apr 2021
(2326) Tololo
UCAC4 503-056678
94.0%
C. Anderson
05 Apr 2021
(156) Xanthippe
UCAC4 532-021546
100.0%
C. Anderson
30 Mar 2021
(481) Emita
UCAC4 401-059106
100.0%
C. Anderson
16 Mar 2021
(420) Bertholda
UCAC4 336-100031
69.2%
C. Anderson
25 Jan 2021
(943) Begonia
TYC 1340-01086-1
59.8%
C. Anderson
12 Jan 2021
(423) Diotima
UCAC4 584-013733
89.6%
C. Anderson
04 Jan 2021
(213) Lilaea
UCAC4 548-042429
45.5%
C. Anderson
29 Dec 2020
(130) Elektra #1
TYC 4801-01033-1
97.5%
C. Anderson
Previously-unknown double star.
27 Nov 2020
(283) Emma #1
UCAC4 611-017367
43.1%
C. Anderson
26 Nov 2020
(1729) Beryl
UCAC4 559-006697
9.3%
C. Anderson
24 Nov 2020
(423) Diotima
UCAC4 578-016284
100.0%
C. Anderson
27 Oct 2020
(342) Endymion
UCAC4 542-036427
44.9%
C. Anderson
15 Oct 2020
(1437) Diomedes
UCAC4 637-005682
80.3%
C. Anderson
Jovian Trojan asteroid.
01 Oct 2020
(554) Peraga
TYC 6308-01033-1
100.0%
C. Anderson
21 Sep 2020
Umbriel (Uranus II)
UCAC4 522-004081
32.5%
C. Anderson
Cited in Monthly Notices of the Royal Astronomical Society , Volume 526, Issue 4, December 2023, Pages 6193-6204 .
17 Sep 2020
(185) Eunike
UCAC4 412-078333
99.5%
C. Anderson, G. Beuning, L. Beuning, L. Beuning, S. Korecki
07 Aug 2020
(207) Hedda
UCAC4 352-187113
75.6%
C. Anderson
10 May 2020
(667) Denise
TYC 1464-00943-1
82.1%
C. Anderson, K. Thomason
29 Apr 2020
(58) Concordia
TYC 4981-00328-1
96.3%
C. Anderson
20 Apr 2020
(70) Panopaea
UCAC4 610-024936
96.5%
C. Anderson, C. Anderson
18 Feb 2020
(148) Gallia
UCAC4 497-046647
35.2%
C. Anderson, A. Holesinsky
08 Feb 2020
(32615) 2001 QU277
UCAC4 512-052944
6.8%
C. Anderson
Jovian Trojan asteroid; first measurement by occultation since discovery (2001).
27 Jan 2020
(2634) James Bradley
UCAC4 545-023716
21.8%
C. Anderson
First measurement by occultation since discovery (1982).
15 Dec 2019
(979) Ilsewa
UCAC4 516-030661
15.8%
C. Anderson
First measurement by occultation since discovery (1922).
17 Nov 2019
(163) Erigone
UCAC4 361-199049
62.8%
C. Anderson, A. Holesinsky, K. Snell
02 Nov 2019
(120) Lachesis
UCAC4 555-046398
1.7%
C. Anderson
30 Sep 2019
(547) Praxedis
UCAC4 441-118948
10.8%
C. Anderson
25 Sep 2019
(493) Griseldis
HIP 40716
53.9%
C. Anderson
Video
02 Sep 2019
(1259) Ógyalla
UCAC4 568-028403
22.4%
C. Anderson
25 Jul 2019
(713) Luscinia
UCAC4 400-078605
66.5%
C. Anderson
02 Jul 2019
(517) Edith
UCAC4 333-131777
90.9%
C. Anderson, D. West, A. Holesinsky
24 Jun 2019
(52) Europa
UCAC4 441-000722
100.0%
C. Anderson
24 Jun 2019
(2906) Caltech
UCAC4 320-120385
37.7%
C. Anderson
21 Jun 2019
(91) Aegina
UCAC4 319-115946
82.5%
C. Anderson
09 May 2019
(225) Henrietta
TYC 5019-00392-1
69.7%
C. Anderson
04 May 2019
(410) Chloris
UCAC4 378-099549
94.0%
C. Anderson
25 Apr 2019
(690) Wratislavia
TYC 6751-00068-1
80.9%
C. Anderson
01 Feb 2019
(538) Friederike
UCAC4 541-023639
40.1%
C. Anderson, S. Korecki
Video (on Facebook)
24 Jan 2019
(638) Moira
UCAC4 570-033268
36.0%
C. Anderson
23 Jan 2019
(84) Klio
UCAC4 619-016579
51.3%
C. Anderson
29 Sep 2018
(671) Carnegia
TYC 2437-00868-1
62.9%
C. Anderson
10 Sep 2018
(174567) Varda
UCAC4 440-067774
5.9%
C. Anderson, R. Showers, K. Thomason
Trans-Neptunian Object & dwarf planet candidate
15 Aug 2018
(134340) Pluto
UCAC4 341-187633
20.3%
C. Anderson, D. West
Occultation by atmosphere only
17 Apr 2018
(137) Meliboea
2UCAC 28992342
92.5%
C. Anderson
06 Oct 2017
(1936) Lugano
TYC 1358-00407-1
31.1%
C. Anderson
Video
28 Sep 2017
(69) Hesperia
UCAC4 380-139928
99.9%
C. Anderson, Ky. Hansen
26 Sep 2017
(372) Palma
UCAC4 697-043370
100.0%
C. Anderson
09 Aug 2017
(903) Nealley
TYC 5788-00046-1
66.8%
C. Anderson
16 Apr 2017
(838) Seraphina
4U 475-43580
31.8%
C. Anderson, Ka. Hansen, Ky. Hansen
11 Apr 2017
(105) Artemis
HIP 62736
26.3%
C. Anderson
18 Jan 2017
(52) Europa
2UCAC 28031948
99.9%
C. Anderson
Profile with shape model derived from rotation light curve.
22 Oct 2015
(247) Eukrate
TYC 3413-01493-1
57.3%
C. Anderson, S. Barksdale
23 Aug 2015
(107) Camilla
TYC 5595-00982-1
88.0%
C. Anderson, B. Hall, J. Royalty
Cited in Astronomy & Astrophysics , 7 Feb 2017 .
Profile with shape model derived from rotation light curve.
27 Jul 2015
(8823) 1987 WS3
HIP 90382
2.2%
C. Anderson, B. Hall
First measurement by occultation since discovery (1987).
12 Feb 2015
(931) Whittemora
TYC 652-01042-1u
14.2%
C. Anderson, D. West
09 Oct 2014
(54) Alexandra
TYC 6308-00865-1
Not rec.
C. Anderson
*At the Centennial Observatory. Observers in other locations not listed.
The table below includes all the negative observations (misses) recorded at the Centennial Observatory for which at least one other observer recorded a positive, and no other negatives
lay between the asteroid's shadow and us. Such misses may also help constrain the asteroid's size and shape (depending on distance from the shadow path, best seen in the profile).
Significant Asteroid Occultation Misses Recorded at the Centennial Observatory
Date (GMT) Asteroid Distance from predicted path* Prob. Observers Notes
31 Dec 2023
(5651) Traversa
4 mi. (6 km) outside 1-σ
6.8%
C. Anderson
16 Dec 2023
(911) Agamemnon
35 mi. (56 km) outside 1-σ
<0.05%
C. Anderson
04 Nov 2023
(3132) Landgraf
In 1-σ, 3 mi. (4.8 km) outside shadow
15.3%
C. Anderson, R. Mayer
07 Sep 2023
(2592) Hunan
In 1-σ, <1 mi. (1.6 km) outside shadow
29.0%
C. Anderson
24 Nov 2022
(653) Berenike
In 1-σ, <1 mi. (1.6 km) outside shadow
50.5%
C. Anderson
19 Oct 2022
(568) Cheruskia
7 mi. (11 km) outside 1-σ
6.7%
C. Anderson
15 Aug 2022
(786) Bredichina
In 1-σ, 11 mi. (19 km) outside shadow
29.0%
C. Anderson
25 Apr 2022
(633) Zelima
In 1-σ, <1 mi. (1.6 km) outside shadow
47.9%
C. Anderson
13 Feb 2022
(779) Nina
In 1-σ, 6 mi. (10 km) outside shadow
19.4%
C. Anderson
15 Aug 2021
(790) Pretoria
10 mi. (16 km) outside 1-σ
6.4%
C. Anderson, R. Jones
10 Aug 2021
(2613) Plzen
28 mi. (45 km) outside 1-σ
2.7%
C. Anderson
30 Mar 2021
(237) Coelestina
5 mi. (8 km) outside 1-σ
0.3%
C. Anderson
12 Jan 2021
(356) Liguria
In 1-σ, 4 mi. (6 km) outside shadow
36.1%
C. Anderson
12 Nov 2020
(4749) Ledzeppelin
In 1-σ, 18 mi. (29 km) outside shadow
7.5%
C. Anderson
28 Oct 2020
(624) Hektor
117 mi. (188 km) outside 1-σ
<0.05%
C. Anderson
Jovian trojan asteroid.
30 Aug 2020
(360) Carlova
25 mi. (40 km) outside 1-σ
1.5%
C. Anderson
15 Aug 2020
(532) Herculina
13 mi. (21 km) outside 1-σ
1.6%
C. Anderson
16 May 2020
(560) Delila
31 mi. (50 km) outside 1-σ
1.3%
C. Anderson
24 Apr 2019
(386) Siegena
587 mi. (945 km) outside 1-σ
<0.05%
C. Anderson
19 Mar 2019
(1072) Malva
14 mi. (23 km) outside 1-σ
4.9%
C. Anderson, S. Korecki
14 Dec 2018
(164) Eva
52 mi. (84 km) outside 1-σ
<0.05%
C. Anderson
05 Nov 2018
(545) Messalina
In shadow, 34 mi. (55 km) from center
53.6%
C. Anderson, H. Lavin
21 Sep 2018
(89) Julia
147 mi. (237 km) outside 1-σ
<0.05%
C. Anderson
21 Feb 2018
(1328) Devota
475 mi. (764 km) outside 1-σ
<0.05%
C. Anderson
21 Feb 2018
(372) Palma
1784 mi. (2871 km) outside 1-σ
<0.05%
C. Anderson
19 Oct 2017
(1574) Meyer
17 mi. (27 km) outside 1-σ
5.9%
C. Anderson, S. Korecki
29 Dec 2016
(446) Aeternitas
In 1-σ, <1 mi. (0.6 km) outside shadow
49.1%
C. Anderson, D. West, Ka. Hansen, Ky. Hansen
29 Dec 2016
(102) Miriam
665 mi. (1070 km) outside 1-σ
<0.05%
C. Anderson, D. West
29 Jun 2016
(1796) Riga
194 mi. (312 km) outside 1-σ
<0.05%
C. Anderson, S. Barksdale, S. Mauldin
11 May 2016
(569) Misa
In 1-σ, 8 mi. (13 km) outside shadow
41.2%
C. Anderson
29 Oct 2014
(393) Lampetia
307 mi. (494 km) outside 1-σ zone
Not rec.
C. Anderson
*The 1-σ zone (delineated in red on the "Observers" maps) has a 68.27% chance of containing at least some of the asteroid's shadow ("one
standard deviation" from the predicted shadow path). The wider 2-σ zone (two standard deviations from the shadow) has a 95.45% chance of containing at least
some of the asteroid's shadow.