PLANET. 
595 
obfervations. He had given elements in a circular orbit 5 
and Hr. Burckhardt at Paris, and Mr. Gaufs at Bremen, 
elliptical elements. Baron Zach publilhed calculations 
of its place from Dr. Burckhardt’s elements, in his month¬ 
ly journal; and the aftronomers of Europe had laboured 
to find it by thefe calculations and their own, but in vain. 
Mr. Gaufs of Brunfvvick, probably excited by this difap- 
pointment to try to produce more exaCt elements, fuc- 
ceeded in the attempt, and calculations made upon them 
were aifo published in the fame monthly journal, and 
fortunately were the means of finding the planet again, 
which was obferved by baron Zach, at the Gotha Obfer- 
vatory, on the 7th of December, 1801, and by Dr. Olbers, 
at Bremen, on the ift of January, 1802, as it had been 
difcovered by M. Piazzi on the ift of January of the pre¬ 
ceding year. Dr. Olbers obferved the planet, without 
knowing it, making a right angle with two ftars in the 
right wing of the conitellation of the Virgin ; and, looking 
again the next night, was llruck with the appearance of 
the figure of the triangle being changed, which flowed a 
motion that pointed out the planet to him. He thought 
he was the firlt who had obferved it fince it had been loft, 
but baron Zach afterwards publiflied an account of his 
having feen it before, on the 7th of December ; who, 
however, not being certain of its being the planet, waited 
before he publilhed any thing till he could verify his ob- 
fervation by the return of fine weather, which was not 
till the latter end of the month. Thus thefe two learned 
gentlemen may both be cor.fidered as difcoverers, fince 
each found it without the aftiftance of the other; and, if 
either of the obfervations had been wanting, w r e Ihould 
have been in poflefiion of the planet by the obfervation of 
the other. Wemuft, however, always gratefully acknow¬ 
ledge our principal obligations are to M. Piazzi, the ori¬ 
ginal difcoverer, though he let it afterwards dip through 
liis fingers ; and, by withholding an early, free, and 
ample, communication of his difcovery from the learned 
world, hazarded the total lofs of it to the prefent genera¬ 
tion, to be difcovered again, perhaps by accident, in fome 
future age. We are, however, now in full pofleflion of it, 
without fear of lofing it again, except only in the fun’s 
rays, in like manner as the other planets, to emerge from 
them again on the contrary fide of the fun, and from an 
evening liar turned into a morning one. 
This fmall planet is apparently furrounded by a denfe 
atmofphere, and plainly exhibiting a difc, when examined 
with a magnifying power of about 200. Its revolution 
round the fun is performed in four years, feven months, 
and ten days ; at a mean diftance of nearly 260 millions 
of Englilh miles. The excentricity of its orbit is fome- 
what greater than that of Mercury, and its inclination to 
the ecliptic exceeds that of all theold planets. According 
to Dr. Herfchel, its diameter does not exceed 160 miles ; 
whereas Mr. Schroeter makes it 1624. miles. The following 
table comprehends ail the particulars that are known con¬ 
cerning it: 
Tropical revolution, La Lande 
Do. from Malkelyne’s Table 
Annual motion - 
Mean longitude, January f, 1804. 
Place of alcending node in 1804 
Place of aphelion, Jan. 1, 1804 
Excentricity, the mean diftance being 
Inclination of orbit - - - 
Greateft equation of centre 
Mean diftance from the Sun, that of the } 
Sun from the Earth being 1 j 
Mean diftance in Englilh miles 
Diameter in Englilh miles, Herfchel 
•-, Schroeter 
1 o 
,h 
4 y 7 " 
1681 d 12“ 9' 
2 s 18° 14' o" 
10 11 59 o 
2 21 6 o 
4 4 26 44 
- 1.08141 
10° 37' o" 
9 20 8 
- 2.77 
260,000,000 
163 
1624 
Apparent mean diameter, as feen from the Earth 1" 
Pallas, difcovered by Dr. Olbers in 1802. In our 
account of this planet, vol. xviii. p. 285.it will be feen 
how imperfectly thefe bodies are as yet known 5 fince 
Herfchel fuppofes the diameter of Pallas to be only 80 
miles, while Schroeter fets it down at 2099. 
Juno, difcovered by Mr. Harding, on the ift of Septem¬ 
ber, 1804. Its diameter is 1425 miles. For other parti¬ 
culars, fee vol. xi. p. 529. 
Vesta. — Dr. Olbers who had diftinguiflied himfelf by 
the difcovery of two of the new planets, conceived that 
thefe fmall celeftial bodies were merely the fragments of 
a larger planet which had been burft afunder by fome in¬ 
ternal convulfion, and that feveral more might be difco¬ 
vered between the orbits of Mars and Jupiter. He there¬ 
fore concluded, that, though the orbits of all thefe frag¬ 
ments might be differently inclined to the ecliptic, yet, 
as they mull have all diverged from the fame point, they 
ought to have two common points of reunion, or two 
nodes in oppofite regions of the heavens, through which 
all the planetary fragments mull fooner or later pafs. 
One of thefe nodes Dr. Olbers found to be in Virgo, and 
the other in the Whale’; and it was actually in the latter 
of thefe regions that Mr. Harding had difcovered the 
planet Juno. With the intention, therefore, of detecting 
other fragments of the fuppofed planet, Dr. Olbers exa¬ 
mined, thrice every year, all the little ftars in the oppofite 
conftellations of the Virgin and the Whale, till his la¬ 
bours were crowned with fuccefs on the 29th of March, 
1807, by the difcovery of a new planet in the conftella- 
tion Virgo, to which he gave the name of Vejla. 
This planet was obferved at Blackheath the 26th of 
April, 1807, by S. Groombridge, efq. an ingenious and 
aCtive aftronomer; and, purfuing his obfervations with 
perfevering attention and induftry, he at length, on the 
8th of September, 1808, obferved the ecliptic oppofition 
of this planet at y h 30' in longitude 11 s 15 0 54' 26", 
Vefta is of the fifth or fixth magnitude, and may be feen 
in a clear evening by the naked eye. Its light is more 
intenfe, pure, and white, than any of the other three. 
It is not furrounded with any nebulofity, and has no vi- 
fible difc. The orbit of Vefta cuts the orbit of Pallas, 
but not in the fame place where it is cut by that of Ceres. 
According to the obfervations of Schroeter, the apparent 
diameter of Vefta is only 0-488 of a fecond,one half of what 
he found to be the apparent diameter of the fourth fatel- 
1 ite of Saturn ; and yet it is very remarkable, that its 
light is fo intenfe, that Mr. Schroeter faw it feveral times 
with his naked eye. Phil. Tranf. 1807. part ii. p. 245. 
M. Burckhardt is of opinion, that Le Monnierhad ob¬ 
ferved this planet as a fixed ftar, fince a fmall ftar, fituated 
in the fame place, and obferved by that aftronomer, has 
fince difappeared. The following are the elements of the 
orbit of Vefta, computed by Groombridge, Burckhardt, 
and Dr. Pearfon : 
Tropical revolution 
Place of aphelion - 
Place of perihelion 
PDce of afcending node 
Inclination of orbit 
Mean diftance - 
Excentricity in parts of the Earth’s radius 
Diameter in Englilh miles 
1 335“ ° h 23' 
6 s 3 0 o' o" 
8 9 42 53 
3 14 38 o 
7 8 20 
2-163 
0-0953 
23S 
From a variety of confiderations it has been concluded, 
agreeably to the opinion fuggefted by Dr. Olbers, that 
thefe four planets are the fragments of a large celeftial 
body which once exifted between Mars and Jupiter. On 
the fuppofition that they are independent planets, their 
diminutive fize, the great excentricity and inclination of 
their orbits, and their numerous interleClions when pro¬ 
jected on the plane of the ecliptic, are phenomena abfo- 
lutely inexplicable on every principle of fcience, and com¬ 
pletely fubverlive of that harmony and order, which, be¬ 
fore the difcovery of thefe bodies, pervaded the planetary 
fyftem. But, if we admit the hypothefis, that thefe pla¬ 
nets are the remains of a larger body, which circulated 
round the fun nearly in the orbit of the greateft frag¬ 
ment, the fyftem relumes its order, and we difcover a re¬ 
gular 
