Diameter, density, and atmospheric data calculated for Neptune from 7 Apr. 1968 occultatio

Levin, B. YU.

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a.	
I
DIAMETER AND DENSITY OF NEPTUNE (DIAMETR I PLOTNOST'
NEPTUNA).
B. Yu. Levin (Akademiia Nauk SS'a, Institut Viziki 62'dernli)
MOSCOW, USSR).
Priroda, no, 6, 1969, p. 77, 78. In Russian
Okeanologiya Astronomiya
Translated by Reilly Translations, Gardena, California.
November 25, 1969.
Prepared for and issued by the Jet Propulsion Laboratory,
California Institute of Technology, Pasadena, California.
Under NASA Contract NAS 7-100
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h(!:; i11] t' t o 1 l' 1 .1 ()I],	 l vi ho 1(! seri es 01 astr.onom i c;a l Ob., ;('rv0 t i (.)1t:; wi t 1 1 it
Il I (fj1	 (j( (;r( t'
	
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(	 ^`.!	 1	 I	 I	 I')I,l^ ! Ill_'	 (..' 1141:;	 111	 OCCUI- taticI)	 by	 T•1( pl-uill'	 Ot	 it	 still: - 	Ot	 7 , 8
1l	 i	 t_;:	 ,('	 c,	 I	 h( (	 t,1,:; t	 1 1a L ioll Libra.rit 	 'Phr	 duration	 of	 the	 c)c^cua t it lion
1;1 1 	 1 )(1	 t.(':, rt	 1. (l.i.f	 fr^I-Cmt: observation points.
	 Photo( Iect-r:i c^ obser-
t-ic)n:;	 c	 f	 Lite	 or;c:ul_toLi(^n were made
	 it	 Japan,	 Ne41	 ';er,l, ^nd, 	 ;lnd	 nustl-aliI
I rle(:	 1 , 2 p t uno	 11. ;	 4- 11 . 1 (-;1, t (3n:;i v  Ll t.lnosFAic rc,	 the	 di:;4-ipp gat i(nc:e	 i-ind	 1 (2a1 T-)L-, ar -
I1 1 	 c '	 (,1	 III('	 ;I	 iit t	 c,r,l: ;(	 vcrr.l) t('Il::	 Ot	 :	 ec'c)1-1(1 ,
	(I'illllr
	
(^	 l)	 .
I.I'1	 (''	 t.11('	 1):;^	 I vc.1L1.On:,	 I j,Ive	 Li re' . 	Vi) I lll':;	 i Or - 	i II('	 (11..11I(`t('I	 OI
t 4-(,r) Lull(' 	 t.h(-• Iliil.': I I Allil	 ( to Lorm i rled 1jy the- tlI'le J row t l lc bo t ' 1 r111 I n( I 	 Lt t t he
n(f (.1
	
kll(	 U,; t- ImI ic(-,thIo -It Letitia tion o1. the 1i lit of t1w , ;t 4-11 ; the
1!i lli—um	 de-I crrllineel by 1-he c_ Lirat_i011 of the Complete invis.ibi l ity OI the
;t:..;r;
	 t:11(' ir;t( irlc'cji 1t(. - <tete:rrnine^d by twice tho attunurt.LiOn t ime: r)1 t11e
1 1(,, ht: c.,:	 t.11( ' :;t;lr.	 n:; Llie ilniclysi. ; of the obser-vations 0'at wzls lllitcle 1)v
'1'4-:±ylc,r (i': r ►(;aan(a) :;howod, these diilllleters are .res pec L.i.vely 50 500 -1 100 km,
cJ 000 k ; , 1 nd 50 l t)0 1 200 kr;l .	 N opturte i :; so	 Lht-i t there
	
a
r,( c c:( I,f 4- 1,1 (
	 Jc 1 Io("L ioiI Of 1. ight r.iiys 1 i'c,1n I.h(
	 rc^cLi 1_inl ;lr i n	 i t:; 1 - :4- c,Id
c)I urilvi. Ly.	 X111-owinu for thi.; re(luire.,; an increase i1 ► L11L, Lltree values
of the d i ijlll('t(_'1_• Y)y L-Ir-proximately 100 knl .	 In addi ti.on, the rnirimurcl and
_intcrilledi :.ltc
 
dimensions mu:;t be increa.;ed because of refraction of 1_i(il lt
in the i.ltmospher:e of the planet. For a layer_ thi.lt attenuated the
li(_'ht of the star by <)tte-hr lf, this correction is also equal to 100 km.
` z kin(- ), both corre(-tiorts into consideration, the true diameter cor_ rc-lspond-
in- to hitlf--atttenuati.on of the :st-ar is E 1 300 km. As for the minimum
vi:lu(, o,C the (li.^lineter, the correction as ,-,ociated with the refract 4 .o11 is
but it i;; dil 1 I.cult to estimate 1.ts preci:;e valuo.
'1'L-I'llo r (:ons i cler.:; Hie cliilnleter of. thc:!	 c)1 N(1I .ime, i . c1.
the :surface of the c1Oud layer, to he- '4-0 000 kln based on occul.ta Lion
observiltions.
The nevl v- % lue of the diameter of- Neptune is almost 10 per cent  (treater.
than that obta i ne ,3 in 1953-•1955 by Cam.-.chel, Dollfuss, and Kuiper.
[film i sh(_ 1' , Dol ' f_ yus, an(1 Keyperl (thee measured it by means of a di scortleter 	 I
..And doubtc image micromet-er) , and Only a little less than that obtained
1 -)y NI.Y - 11(-Ir .l i.rt a U99- 1900 who performed • _he measurenlent^; w i tit a f i lailleltt
micrometer.
If one starts from the measurements of 1953-1955, then, as has been con-
sidered in the last few years,
	
the mean density of the planet is equal to
I.((	 r,f	 /r.tlt(,tt'((,:(1 P. 0. IIUX 2214 .	 GAIt01iNA, CALIFORNIA 90:47 (213) 53;-7.181	 (1-1 31
 63 i-57b5
I' I )! ll rc	 'I'll C'	 coll(I I t i ( II
OI	 Nc 1 11111 c'	 Oc.c:ll I t ;1 t i ,P
(^f	 I li c 	 ;1 1 , 	 I O1'
;^ t
	 i 11	 I; ► }), ► rl	 (I)	 :111(1
i ii	 At l	 t r,+ I i; I	 (_')	 I l l c.
 :I	 I ()l)	 I)O i 11 t
t U	 t II l'	 I1O I t it
	
li(1 I ^'	 ^) I	 1 ,1('
tllll(-
I	 lIi-^	 I	 1' wI(w1( (*t
	 i(	 rc'c_ord OI' the totall
I	 Ili	 Oi' ; ('I)tullC	 111d	 thc, ^;t;lr tit.	 the tlstrolmvlic_t1 I
t i ()It	 U()d;l i I . ( • 	 (:J;il);)11 )	 clut' i III;	 Neptunc;' s nlo t iOn
ll	 1 O	 t llc'	 ;t 'I I
	
(li('" 1 1111 I 111),	 of	 occ'll l tat 1011) .
f .'>	 O. 1. (I/('	 ,	 I .L.	 iio tice-ifJf y i^bove Lllc, 1m-in cell:.; I L y O I a , iI)ut .	 't hc'
nc_w value of thc diameter of NepLune yields a densi Ly OI J.. i) (I/c m %
Practically coi.rlc:iclirn; with the dero iLy of Ur.ar111s.
	 'thus, bo)L11 platlet:s
shOu ld have i-In a1wos t identical composition.
'Phc- cuL.lr:;c' Of t-h(, <Ittonuation and the i.ntcncii ictlt.ic)n of the 1ight of th('
for dill i nq I l
	 11 1 .;,1! pear-lnce behind N Cptulle - nd r ('ill:	 y 1 E'1 CI:;
1l?II: ur tzint i.nf Orl ►ldti011 ConCernln(J the at111osphere of this p1anut. Even in
1.929 C. F(-J)ry (:' ll. Prll)ri.] developed a theory of attenuation of the light
_)f a ^:Lar ,Iurilly its occultation by a plrinet havi nO an atmosphere.
T:j>l).l;^i r ►y I',al)ry':: t 1wOry to Lilo sc^t of ob:;ervat 1.on
	 of Nept-mw's occultati 011
Jlva(ie at al-I. t1w joh c r'vationj pointf , it wa., Iound that. in the layer.
respon^-.U)Ie,
 1-or the half--attenuation of the light of the star, the so
called height of homo,leneous atmosphere, which cha:acterizes the sl.ope..
of - (^ecre a., ;e i-n its, dew..; i- ty with (-ll t:i. tude, is 45 kill.
	 Hence, it is possible
to detcrmine the minimum value of Lhe temperature in this 1 i_yer, assumin(,,
that it	 only of molecular_ hydrogen. This minimum temperature
turns c)ut to be :;urpr isi.n(lly hi(Ih, i.e.,  118°l, . 	 One Islay su rpect that
this value of the hei(Iht of the llnnlogeneous a•_lnospheru is e :aggerated.
The (lensi Ly c)1- this layer. turns out to he approxirltately 2-5-10 -6 cJ /cnl 3 ,
i . e . , the same a:; the density ofthe 1 ar. th's at111ospher-e at In altitude
1, 6 #(	 1•,1.11ltd ou 1
	 ► •.	 L3o X 7.:' 1 .1	 GARDE=NA, CALIFORNIA OU217 -- (213) 53?-7411 	 ( 13) &31,-5755
2
0a •	 0
'0-- 1 0 1'.111	 T114	 jLl:-; L 110t i.Ccah I o al-t-or lv, -tion	 1 7 the lit1h t. c)1
	 LAw ,;tclr
-0	 1, ,,,c I	 i1j),ire-iAly locat-.(.-t	 100-1.5 i kni ahovc thi , 1.ziyui." of -
J 1t' 1 i I . - It L Lena it i mi	 ();j itawli bulow LL	 irc the 1..1y(-.i!;	 ('jjLJ.1'j.[j the
t o u- i I d i s	 JC_1tA f L' I I I C e c 1 the I i qh L of the star nnuain.,; unc1c.-- a 7,	 i iw, - i t.
i ,, cl-i 1, f i cult Lo (.:alcailate Ilic refra -Lion croat.!d by t11c !11.
the atmo., ;phoro of Neptuic ohtaintd throu(Ili
I	 I	 . 1.-atA.()n, im,'	 Lit. dif-ol' the h(.oinnin- 111d O(d (If OCCL 'L
('11 1 1 1 t,	 rva L( , t: I( , :" f	ilf(., ( " ,:,i l 	 di ;ti 1i(jUi.,.;1lud	 1-170111 Mle (.111WAlf.r.	 I I i.
1-1t
.
- ,
 ),,:	 %v Ah eit-Aior the	 proper Lie.. )I the	 M-
t I r.	1 - I - cc t t; cif  I a ti tu (I o ( Wi (_. u r u 2 ) .
ODC 521.86
—.P. O. 13ox 2214 -- GARDENA, CALIF()F?NIA 90247 -- (213) 53 :-7401 -- (213) 635-5755
3


Diameter and density of Neptune

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