Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-10-27
De Sitter of Holland Thinks
Gas Freed by SmaSh-up
Condensed Into Liquid.
PRESENT SOLAR SYSTEM
WITH EARTH FORMED
Cosmologist Tells Academicians
Second Similar Grouping May
Exist in Universe.
BY THOMAS R. HENRY.

| its revolving planets, was attributed to
/ an actual collision between the sun
and another star of approximately the
| same size by Prof. Willem De Sitter,
! famous Dutch astronomer. in lecture
here last night before the Washington
| Academy of Sciences and the Society
| of Sigma Xxi.
The great smaSh-up, Prof de Sitter
said, probably took place between 1,000,-
! 900, 900 and 100000 900 years ago,
afnd the two great celestial bodies may
! have been in contact for four or five
| hours. Previous theories of the birth
| of the system of which the earth is
part and which may be unique in
creation have been that the planetc
were thrown off from the sun by CEN
! trifugal force when that body was an
| enormous revolving mass of thin gas
now an abandoned concept-and that
| they were pulled away by the gravita-
/ tional attraction of another star passing
| through space somewhere in the neigh
| borhood of the sun.
| The second theory now is held gen.
! orally, but mathematical examination,
| DR.. De Sitter said, shows that it will not
! At the case. It does not explain why
| the sun and all its planets revolve on
| their axes. nor why the planets move
around the sun in nearly circular orbits
| instead of in long, drawn-out ellipSoids.
| 1t also leaves unexplained the birth OF
the satellites of the planets. which also
move around their parent bodies In
nearly circular orbits.
Holds Collision Freed Gas.
All these mysteries are cleared up,
said the astronomer, by assuming that
the careening star actually hit the sun
in a special way-not head-on smash.
nor a grazing blow, but close enough so
that about one-eighth of the radius of
the visitor would pass through about
| eighth of the radius of the sun.
Both were great masses of gas, so they
could pass through each other.
They were moving with terrific speed,
so that the mixing of parts of the two
masses set up whirlpoolS of gas in the
contact zone. AS the visitor moved on
! its gravitational force pulled away some
of these whirlpoolS. already revolving,
from the sun and started them moving
| in long drawn-out enipsoidS through
| space around the sun. They already
were revolving and, free in space, there
earth still turns on its axis every "a
hours, and will continue to do so until
tidal friction causes it to stop.
But mathematical analysis also shows,
Prof. De Sitter said. that if this was all
that happened the planets would move
in slender ellipses which might have
brought the earth, for example, back
into the sun again. To meet this OBJ
lection he assumed that not all the gas
molecules drawn out of the sun went to
form planets, but that some were start
| ed moving in the same sort of indie
pendent orbits around the parent mass.
| But the gravitational attraction be-
| tween these independent particles was
strong and tended to draw in their
I Orbit four n yir,oo 1f ofr-
Gle. Through this free gas the revolv
ing planets moved. It's friction tended
to slow them up and to change their
own orbits toward the circular form.
Believes Gas Formed Earth.
Now, he pointed out. the sun also re-
wolves on its axis. just like its planets
There is no reason to believe that 1t
was revolving at the time of the smash
up, nor Immediately afterward. But
| gradually this free, revolving gas was
| pulled back toward the sun. When it
came in contact with the parent body
again it tended to pull it into an axial
revolution. Prof. de Sitter said that
an amount of free gas about sufficient
to have formed the great planet Jup-
tier would have been just enough TO
| cause the sun to revolve.
The next puzzling point to be ex-
planned, he said, was that of the origin
of sattelites-not including the moon,
which differs so Strikingly in size from
the other minor bodies in the solar sys-
tenn that it must have originated In
different way The planets, when they
first were started moving in orbits
around the sun, were masses OF gas.
They were pulled of somewhat like a
draWn-out string of beads, with the
largest beads in the center and the
Snaller at the two ends.
Since they were only tenuouS gas, 1t
might have been expected that the sun
would pull them back in again when
their orbits came TO the nearest point
of contact, the perhelion. But the
| smaller the mass the more rapid the
condensation into some form of matter
approaching a liquid, which would be
heavier and require more gravitational
force to dislodge. This, he assumed.
happened to the smaller planets-Mer-
curry. Venus and Earth. When, at the
expiration of year OF free life, they
passed the point where they originally
were torn loose they had condensed SUI
ficiently to guarantee their future indie
pendence.
Accounts for Planets Moons
The great planets. Jupiter. Saturn,
Neptune and Uranus, remain gaseous.
So the pull OF the sun at perhelion
1 drew out SOlllC VI t4lCA SuDotaAkNC hdSs
because of their distance, was not able
to get it back again. Some OF 1t
formed into moons which began to
repeat with respect 10 their own par
ents what they themselves had done
with respect to the grandparent. the
sun They started moving in long ell
lipSeS around the planets. But here
there was much free gas through which
they must move and which tended 10
draw their paths from ellipses to
circles.
The falling back of the free rotating
gas he insisted, cannot explain the rc-
tation of the great planets, as it does
the rotation of the sun. 1t would have
required a mass of free gas 400 times
the total mass of all the satellites of
Jupiter 10 have caused this effect, so
the astronomer is forced back TO the
whirlpool theory.
The special sort of collision neces-
sary to have given birth 70 anything
like the solar system, Prof. De Sitter
said. reduces enormously the chances
that il can have happened very often
among the many billions of stars which
compose the great Milky Way, galaxy.
Although these stars seem very dense,
they are actually so far apart that.
although they are travelling constantly
at tremendous speeds, there is very lit
tie likelihood of two coming In suffi-
GENTLY close contact TO raise great tides
on each other.
). Considering The mathematical prob
-