Evening star., 1939-05-04
Of Stars, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
And Study
BIZ Thomas z. Henri.

By Thomas r. Henry.
Collisions Of stars at 300 -mile-a-second
speeds may account for the celestial
explosions of almost Nmitless energy
known to astronomers as supernovae,
according to report just made to the
National Academy of Sciences here by
DR.. Fred L. Whipple of Harvard Uni
versity.
Such an explosion has an energy in
ergs, the basic energy unit, Of followed
by 48 or 40 ciphers. This is about the
energy, DR.. Whipple's calculations show,
which two bodies like the sun would
release in some form or other If they
actually sideswiped each other. Some
of it would be in the form of light and
heat which could be recorded on earth.
The rest would be expended in hurting
stellar matter trillions of miles into
space.
Up to the present astronomers have
been unable to formulate any adequate
explanation Of supernova explosion.
There is one approximately every year
somewhere in creation, although only one
possible example is recorded for the
entire Milky Way galaxy of which the
solar system forms part They are
now being studied in the hundreds of
thousands of outer galaxies millions of
light years distant.
Although the crashing stars would
have about the right amount of kinetic
energy to account for supernova, Prof.
Whipple reports it Is difficult to con-
ceive how such large proportion of it
would appear as radiant energy. The
energy released in such smash would
be greatly augmented, he points out, the
nearer it came to being head-on COL
nsion the probability for which is much
smaller than for grazing collision. The
possibility has become less fantastic, he
points out, with newer concepts of the
numbers and thickness of stars.
The probability that two stars will
crash is very slight. Assuming a uni
form density through galactic space
astronomers have calculated that such
collision probably would occur once in
every 100000 ,OOo, 100000 years. This is
about 5000 times as long as the Milky
Way system is believed to have existed
in anything like its present form.
great deal depends, however, on
how thickly the stars are packed into
galactic space. This can only be esti-
mated. Most stars are forever invisible,
the average being only about half the
size and tenth the weight of the sun.
Present calculations range from mini
mum total of about 5000 100000 to
maximum of close to 200 600, 900 900, con-
sidering the sun as an average star.
The most generally accepted estimate
is about so 900 100000. This would mean
a density of so suns per cubic parsec,
parsec being the distance which light
moving at about 10000 miles second
would cover in little more than three
years With such density, DR.. Whipple
calculates, there might be at least a
grazing collision once in every $4,000
years.
The star distribution, however is not
uniform. The stars get thicker, closer
to the invisible nucleus of the galaxy,
100000 900, 100000 miles away. The
thicker they get, assuming that their
speed is uniform throughout creation,
the more likelihood of smash. This
speed is calculated at an average of
about 300 miles second. The closer
packed, however, the greater the speed,
and the greater the speed the less nken-
hood of a smash.
There may be critical region in space,
DR.. Whipple calculates, where the speed
and density effects do not balance each
other-making a considerably greater
possibility of collisions. The majority
Of the supernovae actually observed in
the outer galaxies-star systems very
similar to the Milky Way system but
separated from it by immense voids
Of space-have been from 500 to 900
parsecs away from the galactic nuclei.
The earth is almost 10000 parsecs away
from the Milky Way nucleus and hence
well out of any probable danger zone
He is not proposing this thesis, says
Prof. Whipple in his report to the
National Academy as an entirely ade-
quate explanation. A supernova ex-
plosion remains about the most mystic
rious phenomenon in the universe. The
star collision hypothesis, he stresses,
approaches possibility and might be
shown to be entirely possible if all the
facts regarding space density, star speeds,
and the explosion energy were known.