The Locomotive - Lighthouse Survival Blog

1901.] THE LOCOMOTIVE. 103
Professor Watson, who discovered a number of these freak planets, endowed his little
contingent; that is, he left money the income of which is to be used in keeping track of
their wanderings, so that they may never be lost again.
The orbits of the " asteroids," as they are called, exhibit every variety of peculiarity
that is consistent with elliptic motion, and we find some with great eccentricities, and
others with enormous inclinations to the plane of the earth's orbit. The most remarka-
ble member of the family, without doubt, is the little planet that was discovered a few
years ago, and named "Eros." This particular asteroid has an orbit so eccentric that it
actually comes nearer to us at times than the planet Mars. This circumstance alone is
enough to make it an exceedingly important member of the solar system; because its
smallness and comparative nearness will enable astronomers to measure its distance quite
accurately; and when the distance of any one planet is known (in miles) the distances of
all the others can be obtained by a very simple calculation. It turns out, however, that
Eros has a great many other peculiarities of the most interesting kinds; and, while these
others will probably not have the same importance that attaches to the planet's small
mass and relatively close approach, they will nevertheless conspire to make the little
wanderer one of the most interesting objects in the sky. The Popular Science Monthly,
in a recent issue, tells of some of these things in the following words :
"The little planet Eros bids fair to hold the attention of astronomers for several
years to come. Before the observations necessary for the determination of the sun's dis-
tance had been completed came the announcement, by Dr. Oppolzer, of the planet's
variability. A variable planet, with a range of brightness such as Eros has shown, is,
in itself, something new and striking; but this is only the beginning of the problem.
Several hundred stars are known to vary their light periodically, and some advance has
been made in the theory of their variability. Variable stars, however, do not become
invariable; neither do invariable stars, after a time, become variable. But from a varia-
ble planet, having an extremely short period and large range of variation, Eros recently
became invariable. In Europe, soon after the discovery of its variability, its range was
said to be two magnitudes: that is, it shone with about six times as much light at maximum
as it gave at minimum. Precise photometric measurements of the light of Eros,
made by Professor Wendell, gave a range of variation of 1.1 magnitudes on March 1$
of the present year, and of 0.4 magnitude on April 12. On May 6 and 7 no variation
was perceptible, and if any variation existed, it was probably less than a tenth of a
magnitude. Owing to poor weather and the planet's approach to the sun, later observa-
tions have been difficult; but a slight variation was apparent in June. These unique
phenomena are probably the result of the changing direction of the axis of rotation of
the planet, as related to the line of sight; for, although the direction of this axis in
space is fixed, it will constantly change with reference to an observer on the earth.
When (if ever) the axis points directly towards the earth, there can be no variation of
light; and the maximum range will be found when the axis is perpendicular to the line
of sight. Apparently this axis has been recently pointing towards the earth ; and we
may confidently expect that within a short time Eros will again show well marked
changes, although the planet's position may not permit exact observations. On March
5th M. Andre communicated to the Astronomische Niachrichten a discussion in which he
assumed that the variation in brightness is due to the fact that Eros is a double asteroid.
M. Andre even gave approximate elements for a system which appeared to him to satisfy
the conditions. Professor Pickering has recently pointed out that the variations in light
can hardly be accounted for by two similar bodies alternately eclipsing each other, and
has suggested that the known facts can be explained by supposing that Eros is an elon-