Evening star. [volume] (Washington, D.C.) 1854-1972, 1898-04-30

. siticns Of the Principal Stars which above
81. at 9-S-1 PM
| fall perpendicularly. He is sheltered. say
| by a broad-brimmed hat. which prot Gets
| him so long as he stands still but let him
| start to run in any direction and the rain
| will beat against him i'm front. He runs
| against the falling drops. and the result j.
the same as though. while he stood still.
| wind drove the drops against him a.
/, though they fell. not perpendicuIarly but
| slantingly.
Alteration of Light
Here is the principle of the alteration
| or light Light moves like a falling rain
| though inconceiyably faster The earth
ana the observer upon ii move like the man
| VINO runs, and from the combination of the
Two movements il results that the direction
| from which the light of a celestial body
seems TO come, or. in other words the di-
fecuon In which the body appears to be
is not It's true direction. A star is alWay=
seen a little out of its true place in IN
heavens, except when the earth is moving
directly toward IL or directly from IL. n
appears TO be little ahead with reference
10 the direction of the earth's movement
| or The point in the heavens where II really
lsIJust as TO the man who runs in th..
ram .he drops seem to come from a part of
'tie SKY IN advance of that from which they
actually do come: and since as the earth
Swings around I'm its orbit The aIracti,.,
| IN winch II moves continually changes tbs
t. always out OF Its true place, has a
corresponding movement. The star an
pears 10 move in a little orbit which has
the same form as the earth's orbit uouia
nave viewed from the direction of the star
me erect OF alteration is quite too small
- ~ t"n, Naple TO the naked eye; but il is
a matter OF which the astronomer must
.dhe account and for which he must ALLOW,
IN determining the position of a star fror,
user atlon- A great deal OF time has been
amount. and this is one of the prohI, -ss 81
tNact astronomy, at which they are s,ill
Morkihg: The value adopted for the con
ca1Iad o n, ap tt, as this quantity is
| neld in Paris in 1896. is ao47 seconds Of
angular measurement. This will b.. better
understood when it is explained that the
quantity named is the greatest displac--
ment of star due to this cause or one
naif OF the longer diameter of the little ell
Ipse Whch the star seems to describe IN
the course OF the year. a chain of forty
hNe such ellipses would be Just about lnng,
! moon. '
While we are upon the subject Of stellar
movement a word may be said about th.,
| proper motion of stars. Unlike the move
| ment just spoken of. this is a real not
merely an apparent movement
Changing Positions.
1t has been found that many of the stars
| are slowly changing their positions with
respect 10 thelr nelghbors, Sirius Arctu-
rus and Aldebaran have moved from the
places assigned them two thousand years
| ago, distance greater than the apparent
diameter of the moon. II is probable that
| none of the stars is really fixed - but all
| are rapidly moving in space in various di-
| rections. though SO enormous are their dis
tanceS from us that even in the cases Df
| the most rapidly moving il requires CEN
turtles TO effect a change that can be de
| tected with the naked eye.
This Is the movement called proper mo-
ton- With the telescope only motion
across the line of sight be detected
since the movement of n star directly to-
ward us or directly from obviously
would not affect its apparent plane on the
celestial sphere. But with the spectroscope
IT is possible to detect a stars movement
I'm the line of sight'-movoment of APP
proach or of iecession-and even to determ-
inc the rate of its movement. To instance
a few cases. Arcturus. Vega. Dubhe, Delta
! Andromedae and Alpha Arietis are ap-
preaching us at the respective rates Of
forty-two, thirty-six. forty-six, fifty and
ten miles a second; Aldebaran. Betelgeuse
and Rigel receding at the rates re-
Spectiyely, of forty-fiVe, sixteen and twelve
miles second.
To illustrate the effect of proper motion
in the long run on the appearance of the
consultations arrows have been attached
On the planisphere to the seven stars Of
the Great Dipper. indicating the directions
| in which the several stars moving aud
the distances to which they move in about
thirty thousand years. 1t will be seen that
the movements such as eventually 10
change very materially the figure of this
group of stars. and that at remote epoch
in the past also IL must have had a form
| quite unlike its present form. Yet -
slowly does the change take place that at
time as far back as history takes US tie
Dipper must have looked almost precisely
| as ii does tonight.
The Planets.
Mercury will be morning star through
out the month. reaching It's greatest elong-
alton west of the sun-24 degrees As min
utes-on the 2Sth. II should be visible
during the last week of the month south Of
east.
Venus has been evening star since
February Il. and viii continue to be such
until December 1. She is already con-
spicuous object for an hour or more after
sunset low in the west.
Mars is a morning star, rising at about
$3.50 a. m. at the beginning of the month,
exactly in the east. He crosses the equ-
noctial today, passing from the southern
to the northern hemisphere, and moving
rapidly eastward.
Jupiter still shifes magnificenty as All
evening star, crossing the meridian soon
after p. m. lie is still retrograding. On
the 9th he will be stationary and there
after his movement will be direct east
ward.
Saturn and Uranus. in the Scorpion. are
row evening stars and both are above the
horizon at y u. m. low in the southeast.
Saturn will be in opposition to the sun on
the Both of the month.
Neptune, in Taurus sets before 8 ID. m
Doesn't Jimper bore you to death?"
He never comes near me since i lent
him 81"
Cheap enough."-Chicago Record.