Earth Grazers

Mark Pottenger

Most of the time we all pay little attention to actual asteroid orbits when working with asteroids in astrology. We are usually satisfied as long as we have their positions in charts. Occasionally, however, we do need to pay attention to orbital details. I recently had an inquiry from someone who thought there must have been something wrong with the underlying calculations because they saw a 10-day ephemeris of Ra-Shalom jump from Taurus to Scorpio between two entries.

Most of the asteroids are in a belt between the orbits of Mars and Jupiter. A few are farther out: the Trojans pacing Jupiter, (comet) Chiron farther out, and a number of recent discoveries as far out as Pluto. There are also a few hundred that come inside the orbit of Mars. Those that come close to Earth are colloquially called “Earth Grazers” even though most of them don’t actually come close enough to really worry about. The following are definitions from Asteroids:

Amor asteroids: asteroids having perihelion distance 1.017 AU < q < 1.3 AU.

Apollo asteroids: asteroids having semimajor axis a > 1.0 AU, and perihelion distance q < 1.017 AU.

Aten asteroids: asteroids having semimajor axis a < 1.0 AU, and aphelion distance Q > 0.983 AU.

In ordinary language: Amor asteroids closest approach to the Sun is a little bit outside Earth’s orbit. Apollo asteroids average distance from the Sun is outside Earth’s orbit and their closest approach to the Sun is no farther than 1.017 times Earth’s average distance from the Sun (and may come inside Earth’s orbit). Aten asteroids average distance from the Sun is inside Earth’s orbit and their greatest distance from the Sun is greater than 0.983 times Earth’s average distance. All three categories either cross inside Mars’ orbit or are completely inside it.

I did a quick scan of a file of asteroid elements to produce the following 3 lists:

Amor asteroids: 4401 Aditi, 887 Alinda, 1221 Amor, 1943 Anteros, 2061 Anza, 2059 Baboquivari, 2368 Beltrovata, 1580 Betulia, 1916 Boreas, 4957 Brucemurray, 1917 Cuyo, 3552 Don Quixote, 4954 Eric, 433 Eros, 3122 Florence, 1036 Ganymed, 1627 Ivar, 5324 Lyapunov, 4055 Magellan, 3352 McAuliffe, 3553 Mera, 3199 Nefertiti, 4947 Ninkasi, 2202 Pele, 4487 Pocahontas, 1915 Quetzálcoatl, 4587 Rees, 3288 Seleucus, 2608 Seneca, 5370 Taranis, 1980 Tezcatlipoca, 3551 Verenia.

Apollo asteroids: 2101 Adonis, 1863 Antinous, 1862 Apollo, 2135 Aristaeus, 4581 Asclepius, 2063 Bacchus, 3752 Camillo, 4769 Castalia, 1865 Cerberus, 4183 Cuno, 1864 Daedalus, 3671 Dionysus, 3103 Eger, 3838 Epona, 1620 Geographos, 2212 Hephaistos, 5143 Heracles, 1566 Icarus, 1981 Midas, 4486 Mithra, 4660 Nereus, 2201 Oljato, 3361 Orpheus, 2329 Orthos, 4450 Pan, 3200 Phaethon, 4341 Poseidon, 5011 Ptah, 1866 Sisyphus, 2102 Tantalus, 1685 Toro, 4179 Toutatis, 4257 Ubasti, 4015 Wilson-Harrington, 4544 Xanthus.

Aten asteroids: 3554 Amun, 2062 Aten, 2340 Hathor, 3362 Khufu, 2100 Ra-Shalom.

There are more asteroids in all categories being discovered and named all the time, so these lists will quickly become dated, but they do give a snapshot.

Several years ago, when I was printing asteroid ephemerides more often instead of concentrating on producing disk ephemerides as I now do, I used a simple rule of thumb to pick the print interval. Main belt asteroids can safely be printed with a 10-day interval without creating an unreasonable interpolation interval. Those even farther out can be printed with even larger intervals. If an asteroid comes inside the orbit of Mars, a 5-day interval is safer. If an asteroid approaches or crosses the orbit of Earth, I would normally print daily positions for it.

The ephemeris fragment below, for 2100 Ra-Shalom in three days in October 1994 at 0.1-day intervals, shows that on rare occasions even daily positions are not enough. This is a case where the nickname “Earth Grazer” is more accurate than usual, because Ra-Shalom comes within 0.16 AU of Earth. That is still over 14 million miles away, but it is quite close in astronomical terms. It is definitely close enough to produce a phenomenal geocentric motion even though the heliocentric motion is not at all unusual. In one day (October 19th), Ra-Shalom moves from 7 Gemini 28 to 17 Libra 7, more than 4 complete signs! If you look at the latitudes, you will realize that Ra-Shalom passed almost exactly under the south pole of Earth during that day and that the polar placement is a significant factor in producing the apparent rapid movement on the ecliptic. Polar positions like this also raise all the questions about the validity of aspects that people raise for stars or other bodies a long way from the ecliptic. The velocities, as in almost all CCRS Horoscope Program printouts, are instantaneous velocities (in degrees) rather than daily motions. You can see how high the geocentric velocity got.

October 1994 (Delta T= 58.6 seconds)

Ra-Shalom

Dy

Hr:Mn

LONGIT

LATIT

DIST

VELOC

H.LONG

HLAT

HDIS

HVEL

18

0: 0

1Ge42

85s21

0.16

5.90

24Ar50

8s57

1.02

0.77

18

2:24

1 59

85s36

0.16

7.08

24Ar55

8s58

1.02

0.77

18

4:48

2 18

85s52

0.16

8.67

24Ar59

8s59

1.02

0.77

18

7:12

2 39

86s 7

0.16

10.92

25Ar 4

9s 0

1.02

0.78

18

9:36

3 4

86s23

0.16

14.23

25Ar 8

9s 1

1.02

0.78

18

12: 0

3 32

86s38

0.16

19.50

25Ar13

9s 2

1.02

0.78

18

14:24

4 4

86s54

0.16

28.59

25Ar18

9s 4

1.02

0.78

18

16:48

4 42

87s 9

0.16

45.77

25Ar22

9s 5

1.02

0.78

18

19:12

5 26

87s24

0.16

76.43

25Ar27

9s 6

1.01

0.78

18

21:36

6 20

87s39

0.16

109.86

25Ar32

9s 7

1.01

0.78

19

0: 0

7 28

87s54

0.16

129.86

25Ar36

9s 8

1.01

0.78

19

2:24

8 54

88s 9

0.16

139.69

25Ar41

9s 9

1.01

0.78

19

4:48

10 48

88s24

0.16

144.31

25Ar46

9s10

1.01

0.78

19

7:12

13 24

88s39

0.16

145.87

25Ar50

9s11

1.01

0.79

19

9:36

17 7

88s53

0.16

144.99

25Ar55

9s12

1.01

0.79

19

12: 0

22 50

89s 7

0.16

141.35

26Ar 0

9s13

1.01

0.79

19

14:24

2Cn25

89s20

0.16

133.33

26Ar 4

9s14

1.01

0.79

19

16:48

20 6

89s31

0.16

116.89

26Ar 9

9s15

1.01

0.79

19

19:12

21Le20

89s37

0.16

86.65

26Ar14

9s16

1.01

0.79

19

21:36

25Vi49

89s34

0.16

53.02

26Ar19

9s17

1.01

0.79

20

0: 0

17Li 7

89s24

0.16

32.40

26Ar23

9s18

1.01

0.79

20

2:24

28 30

89s12

0.16

21.59

26Ar28

9s19

1.01

0.79

20

4:48

5Sc 5

88s58

0.16

15.50

26Ar33

9s20

1.01

0.79

20

7:12

9 17

88s44

0.16

11.74

26Ar37

9s21

1.01

0.80

20

9:36

12 10

88s30

0.16

9.24

26Ar42

9s23

1.00

0.80

20

12: 0

14 14

88s16

0.16

7.49

26Ar47

9s24

1.00

0.80

20

14:24

15 49

88s 1

0.16

6.20

26Ar52

9s25

1.00

0.80

20

16:48

17 3

87s47

0.16

5.24

26Ar57

9s26

1.00

0.80

20

19:12

18 2

87s33

0.16

4.48

27Ar 1

9s27

1.00

0.80

20

21:36

18 50

87s18

0.16

3.89

27Ar 6

9s28

1.00

0.80

Here is a 10-day interval ephemeris for the period June 1994–January 1995 for the same asteroid, to give an idea of its normal motion when it is not quite so close to Earth:

Ra-Shalom

Mo/Dy/Yr

LONGIT

LATIT

DIST

VELOC

H.LONG

H.LAT

HDIS

HVEL

6/ 1/94

11Ar20

15n31

0.78

0.41

25Cp50

13n 1

0.92

0.96

6/11/94

15 36

14n32

0.78

0.44

4Aq47

11n30

0.99

0.82

6/21/94

19 59

13n28

0.77

0.44

12Aq34

9n55

1.05

0.73

7/ 1/94

24 24

12n16

0.75

0.44

19Aq32

8n21

1.09

0.66

7/11/94

28 44

10n55

0.71

0.43

25Aq55

6n47

1.13

0.61

7/21/94

2Ta56

9n19

0.66

0.42

1Pi54

5n15

1.16

0.58

7/31/94

6 59

7n23

0.60

0.40

7Pi36

3n43

1.18

0.56

8/10/94

10 49

4n57

0.53

0.38

13Pi 7

2n11

1.19

0.55

8/20/94

14 25

1n42

0.45

0.35

18Pi35

0n39

1.19

0.55

8/30/94

17 43

2s48

0.38

0.32

24Pi 4

0s54

1.19

0.55

9/ 9/94

20 41

9s25

0.31

0.28

29Pi39

2s28

1.17

0.57

9/19/94

23 14

19s41

0.24

0.24

5Ar28

4s 4

1.15

0.60

9/29/94

25 21

36s 7

0.19

0.20

11Ar37

5s42

1.11

0.64

10/ 9/94

27 5

60s34

0.16

0.20

18Ar16

7s24

1.07

0.70

10/19/94

7Ge28

87s54

0.16

129.86

25Ar36

9s 8

1.01

0.78

10/29/94

25Sc53

70s 5

0.19

0.07

3Ta56

10s54

0.95

0.90

11/ 8/94

25 51R

54s21

0.24

-0.05

13Ta40

12s40

0.88

1.07

11/18/94

25 15

42s 1

0.29

-0.05

25Ta28

14s18

0.80

1.33

11/28/94

25 6D

31s 4

0.37

0.04

10Ge18

15s30

0.71

1.70

12/ 8/94

26 26

20s51

0.46

0.24

29Ge37

15s35

0.62

2.24

12/18/94

0Sg19

11s37

0.60

0.54

25Cn 5

13s 8

0.53

2.92

12/28/94

7 40

3s58

0.78

0.89

27Le 5

6s29

0.48

3.46

1/ 7/95

18 20

1n32

0.98

1.16

2Li14

3n11

0.47

3.45

1/17/95

0Cp43

4n53

1.18

1.24

4Sc39

11n 3

0.52

2.92

1/27/95

13 4

6n36

1.34

1.19

0Sg48

14n50

0.60

2.25

With the sort of motion Ra-Shalom showed in October, no printed ephemeris would ever be completely satisfactory. I would want chart positions straight from the computer, and even those I would treat cautiously.

How close an asteroid comes to the Sun also affects disk ephemerides. With the ephemeris format I now use for asteroids, a two-century ephemeris of Chiron is only a little over 2K, most main belt asteroid ephemerides are between 8K and 16K, and the ephemerides of Icarus and Phaethon are over 400K each.

What sort of special meaning, if any, unusual motions should have in astrological interpretations is an open question. Any ideas out there?

Copyright © 1994 Los Angeles Community Church of Religious Science, Inc.

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