500 



KNOWLEDGE & SCIENTIFIC NEWS. 



[August, 1906. 



The New Asteroid 

 1906 TG. 



By Uk. (iiORGio Abetti. 



Amongst the numerous asteroids which the photo- 

 graphic researches of Prof. Max Waif and his co- 

 wortvers at the Konigstuhl Observator\', Heidclbero;, 

 are continually adding to the long; list of those already 

 discovered, there is a faint one of the 13th magnitude 

 w hich, by reason of its very small diurnal orbital motion 

 of about ^ = 300", or neatly that of Jupiter'- himself, is of 

 particular interest to astronomers. 



The new asteroid, provisionally known as 190(1 TG, 

 has, as seen from the earth, a slow retrograde motion — 

 as is usually the case with asteroids when discovered 

 near their opposition to the earth — parallel to, and a 

 little south of, the ecliptic, which has given rise to the 

 conjecture that of all the bodies of this class hitherto 

 known this may be found to be the most distant. It 

 was photographed anew at Konigstuhl on March 3, 

 and two days later it was observed visually at Vienna 

 by Prof. Palisa, who followed it until April 22, when it 

 had fallen to the 14.5 mag-nitude and chang-ed from 

 retrograde to direct motion. 



Basing- his data on the two first observations, viz., 

 February 22 and March 5, Prof. Berberich was enabled 

 to calculate an approximate circular orbit which at once 

 revealed the small value of n, or, in other words, the 

 great distance of the asteroid from the sun. Accord- 

 ing to this first calculation the period of revolution 

 came out as 11.37 years, which, in comparison with 

 the 11.86 year period of Jupiter, was thus seen to be 

 only half a year shorter; but as further observations 

 became available, Prof. Berberich succeeded in de- 

 ducing the following elliptic orbit : — 



Epoch 1906, February 225 Berlin M.T. 



M = 48° 57' 23-"6 



w = 120 25 50 oj 



'^ = 315 34 6 8l igo6 o 



I = 10 20 53'oJ 



•^ = 9 38 426 



iL = 295-"i33 



log. a = 0-719993 



This orljit must obviously not be taken as final, for 

 of the entire path of 3600, but one sixtieth, correspond- 

 ing to the observed motion through 6° in two months, 

 has so far been observed. 



In this second calculation the period of revolution, as 

 given by /!= 295". 133, comes out as 12.03 years, or 

 almost two months g-reater than that of Jupiter, and it 

 is evident that, when still further and more accurate 

 orbital elements deduced from later observations have 

 become available, the period of revolution may be found 

 to be equal or even slightly less than that of Jupiter. 



In any case the fact is now placed beyond dispute 

 that there is a great resemblance in the revolutionary 

 periods of the two bodies, or, if it is preferred, in their 

 mean distances from the sun; for that of Jupiter is 

 5.20 r, or 5.20 times the radius of the earth's orbit, 

 while that of TG (corresponding to log:. = 0.72) is 

 5-25 !■• 



* The diurnal orbital motions of the major planets are - 



Planet. 



Mercury 



Venus 



Earth 



Mars 



Jupiter 



Saturn 



Now the distance of Jupiter, which has only a slightly 

 eccentric orbit, is subject to but a small variation; the 

 distance of T(J, however, oscillates between 4.37 and 

 6.13, and as r, the radius of the earth's orbit, is equal 

 to ] 50 million kilometres, it follows that the distance 

 of the new asteroid from the sun can vary between 655 

 and 920 million.s of kilometres. Its orbital eccentricity, 

 moreover, is four times that of Jupiter, so that, bearing 

 in mind the fact that the sun occupies one and the same 

 focus in all the planetary orbits (all more or less ellipti- 

 cal), T(i in each revolution about the sun pursues a 

 path which is for about 5 years wiiliin and for about 

 7 years without the orbit of Jupiter. 



If, as in the figure, we describe circles about a centre 

 S, representing the sun, a better idea will be obtained 

 of the orbit of the new asteroid with respect to the 

 orbits of Jupiter, Mars, and the Earth, all projected on 



Ore it of jgo6 Td 



mtUions of Jfin. 



S.ule 



the plane of the latter, i.e., the plane of the ecliptic. 

 The portions of TG's orbit lying outside and inside the 

 path of Jupiter are indicated by dotted and continuous 

 lines, while the points N and n represent the ascending 

 and descending nodes respectively of the orbits of 

 Jupiter and TG on the ecliptic. From February 22 to 

 April 22, J 906, the three bodies, Jupiter, TG, and the 

 Earth, had described the paths indicated by the short, 

 hea\y lines. At the present time, TG is moving faster 

 than Jupiter, and, while continuing to recede from him, 

 will shortly pass a point P, which, in the figure, repre- 

 sents the inter-.section of the orbits as seen projected 

 upon the ecliptic. 



Faking the small difi'erence in the sidereal revolutions 

 of the two planets for granted, it is easy to see that an 

 actual approach of the two bodies could only take place 

 in the course of centuries; indeed, from a recent ob- 

 servation made by Prof. Palisa on May 22, it would 

 appear that the mean diurnal motion given above is 

 somewhat too small. A larger value would have made 

 the resemblance between the sidereal revolutions still 



