Evening star. [volume] (Washington, D.C.) 1854-1972, 1901-06-15
WONDERS OF SCIENCE
How Planets That Are Invisible Can
Be Studied
BY TEE ANALYSIS OF LIGHT
Heavenly Bodies That Blaze With
Sudden BriIIiancy
FROM UNKNOWN CAUSES
FROM UNKNOWN CAUSES

/
Written for The Evening Star by Prof. Simon
| Newcomb LID.
No achievement of the human intellect
| Is more wonderful than the discovery of
| planets revolving around many of the
| stars. II these bodies could be seen with
| telescope there would be nothing won
| derful in their being found. But they are
| generally. so far as we know, entirely
| dark; at least. they send forth no light
that the human eye could discern In the
| most powerful telescope. They are and
| must forever be invisible. How, then, is
their existence made known. By their at
| traction on the stars around which they
| revolve, and which they cause to swing
| first to one side and then to the other But
| this swing of star Is so small as to be
| entirely beyond the power Of detection by
| the most delicate eye and the most power
| full telescope To all appearances the stars
| remain absolutely at rest, except for the
! slow, straightforward motion which we
| find many of them to have when observa-
| tions on their positions are extended
| through years or generations If We can
| not see any motion. how do we know that
| the stars move?
This Is the real wonder. 1t is done by
analyzing the light which the star sends to
! US. 1t has long been known that light
| really consists in minute vibrations or
| wave-like motions in an ether which fills
| all space. There are from 10000 to 100000
of these waves in the length Of a single
| inch, and yet they travel forward so rap
| idly that they would encircle the earth
seven times between two beats Of the clock
| Small though they are, each little wave
| has its crest. as have the pillows of the
| ocean. On the latter the distances between
Two successive crests may be more than
the length of ship, or less than that of
| ships boat. So it is with light; although
| countless millions of millions of waves pass
| in single second some yibrate more rap
| idly than others.
| Analysing Light
| By the aid of the spectroscope the as
| tronomer analyses the light of a star, and
thus finds the length of certain of the
| waves which it sends toward us. II it is
moving in direction these waves will
! be a little shorter than when it is moving
| away from us. And thus it is said that
| by measuring the length of the light wave
| which a star emits, it can be determined
| whether the star is increasing diminish
| ing its distance from US. When these most
! difficult and delicate measures were made
upon number of the brighter stars it was
| found that some of them changed their
motion to or from For few hours
| or perhaps few days. a star would be
| moving toward us. then it would slacken
| its pace and move away from us, to re-
| turn toward US again. Thus 1t would VI
DIdle backward ana Forward, as 1t We're,
| like a swinging pendulum. As matter
| OF fact, We know that the motion was more
| likely to be around and around in circle.
But this circle. though millions of miles in
| extent. is so small as to be quite invisible
| at the enormous distances of the fixed
stars. The motion of the stars which
! have described being made known by the
| light can be as we'll determined upon a
| star at teh most immeasurable distance
as upon one In our immediate neighbor-
| hood. And thus it Is that these motions
are made out when the telescope fails to
! show any movement whatever. They can
| be caused only by the attraction Of intisI-
| BILE but massive bodies revolving around
| the stars as the planets revolve around
the sun.
| So exact have these measures been made
| in recent times that the form of the orbit
| OF dark body can. in some cases, be cal
| culated with more or less exactness And
| thus it happens that if there are any in
| habitants on these planets our astronomers
| here on earth could tell them more about
| the motion of the world on which they live
| than the most civilized people few centu-
| ries ago knew Of the motions OF the earth
| on which We dwell.
| Variations in Brightness.
The most recent researches show that
| there is an immense variety among the
| stars. especially to their actual bright
| ness. OF course a star of any given bright
ness will look fainter the farther it is from
| us. Thus it was, in former times. suppos-
| ed that the brightest stars were most near
US. But this is not always the case
| 1t is true that Sirius, the brightest star
| in the heavens. is among the nearer ones;
| about twice as far as the nearest star
| known. But the next brightest is Campus,
| which never rises in our northern ATTITUDES
| though 1t may sometimes be seen in the
| gulf states. 1t is there visible low down
near the southern horizon some time dur
| ing the winter evenings.
| Gill. at the Cape of Good Hope made a
| long series of the most exact measures on
| the position of this star amongst those
scattered around it. with view of de-
| termining its distance The result of his
| work showed that this distance must be
| UNNECESSARILY great. Had it been only
| ten million times the distance of the sun
| he would have found it out. The result
| of his work is that this star must be thou
| sands and perhaps tens Of thousands OF
| times as bright as our sun. If our earth
| revolved around it at the same distance
| that it does from the sun everything on its
surface would Immediately melt with fer
| vent heat.
New Stars.
There are number of cases recorded In
history of new and very bright stars blaz-
/ ing forth in the heavens. This. however.
| occurred very rarely. Sometimes two such
stars would be seen in the course Of a CEN
| fury. Frequently several centuries have
elapsed without anything Of the kind be-
| Ing recorded. But in recent times,
| when people watch the heavens more care
| fully, it is found that such an occurrence
| takes place every year or two. Generally,
! however. the star is so small that only a
| trained expert observer would have noticed
| it among the thousands Of its companions
| Very wonderful, therefore. was the blaz-
! ing out, so recently as last February, Of
the most brilliant star of this kind whose
| appearance has been recorded during the
| last two hundred years 1t is now well
| known under the name of Nova Persei, or
| the new star in the constellation Of Per-
seus. 1t has not yet been determined that
| any star visible in the most powerful tele-
scope existed in the place where this one
| appeared. Yet it blazed up until it was