ASTRONOMICAL PROGRESS IN 1900-1901. 



Venus as seen from the Earth. During the tran- 

 sit Satellite I will cross the disk of Jupiter in 

 a way that will occult its own shadow, which, 

 owing to the penumbral fringe being larger than 

 the satellite, will cause it to be seen as a ring 

 around the satellite. As such a phenomenon is 

 rare, it will be extensively observed, for it has 

 never yet been seen by mortal eyes, nor can it be 



being greatest in middle latitudes and less at the 

 equator and the poles. This conclusion is de- 

 rived from the observation of the relatively small 

 cloudlike masses lying in the upper regions of the 

 planet's atmosphere. It is very doubtful whether 

 the red spot is to be considered as a cloudlike 

 mass. It seems to lie in the deeper levels of the 

 Jovian atmosphere, as is indicated by appear- 



VEKKKS OBSERVATORY. 



except when the Earth is transiting his disk, 

 which will not occur again in several hundred 

 years. 



Prof. Edward E. Barnard, the discoverer of 

 Jupiter's fifth satellite, has in the past two years 

 made it a study, and finds its orbit elliptical, like 

 all the 21 moons in our system. This, the small- 

 est member of our system except the asteroids, 

 revolves around the planet in ll h 57 m 22.04 s . Not 

 only do the planets revolve, but their orbits also 

 do the same. The Earth's orbit makes a revolu- 

 tion once in 109,830 years, while that of the little 

 moon under consideration completes its revolu- 

 tion in 4.9 months, or over 900 degrees a year, or 

 2.465 degrees a day. Seen from the little nioon, 

 Jupiter's disk would extend half-way from the 

 horizon to the zenith. The solar system affords 

 no other example of so rapid a motion or any- 

 thing comparable to it. 



When the great red spot or continent, which 

 resembles a floating island, is observed for the 

 purpose of determining the period of the planet's 

 rotation on his axis, it is found that the period is 

 subject to a regular change, causing a lengthening 

 of its period. Of course the rotation period of the 

 planet itself can not change, but must forever be 

 a constant quantity. This oval red spot was dis- 

 covered, or, rather, first noticed, in 1809, and 

 since it has floated three-fourths around the 

 planet from east to west, or the reverse of the 

 planet's rotation. The spot has slowly increased 

 in length since its discovery. The rotation period 

 of Jupiter is not the same in different latitudes, 



ances when it is near the borders of the planet. 

 Small bright objects are often seen above it, 

 and its surface is frequently veiled by a thin 

 cloudlike screen. Prof. Bredichin, who has made 

 this strange phenomenon a study for years, con- 

 siders the brick-colored spot a solid mass, slid- 

 ing over the liquid surface of the planet, among 

 the lower layers of the vaporous atmosphere. It 

 is very improbable that the spot is a sea of glow- 

 ing lava, as many suppose, because of its color, 

 but more likely a semisolid crust. The width of 

 the spot is 8,000 and the length 30,000 miles. 



A Nest of Nebulae. One of the most remark- 

 able discoveries made in recent years in astronomy 

 was the depiction on a photograph plate covering 

 a portion of the sky two minutes less than the 

 disk of the Moon of 108 nebulae. The photo- 

 graph was taken by Prof. Max Wolf, at the Hei- 

 delberg Observatory, with the Bruce photographic 

 telescope. This astonishing cluster is in the con- 

 stellation Coma Berenices, in a nebulous region 

 due east of the star ft, and preceding it by about 

 thirteen minutes of time. Four or five ,of them 

 occupy a larger space than the others, and show 

 central condensations, and some are elongated; 

 but the greater number are round and very small. 

 We should call a single nebula small whose appar- 

 ent size was equal to the Moon. The photograph 

 was taken on March 4, 1901. This is another 

 striking example of what celestial photography is 

 accomplishing in regions from which the actinic 

 rays have been speeding toward us with the ve- 

 locity of light for thousands of years. 



