THE SOUTHWORTH PLANETARIUM
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Altitude: 10 feet below sea level
Founded January 1970
Julian Date: 2459243.18
2020-2021: LXXIX
THE DAILY ASTRONOMER
Thursday, January 28, 2021
Exploratorium XIV: Runaway World
*Location*
300,000 light years outside the Andromeda Galaxy
*Time*
Christmas 2021
Feel that? Rock solid surface. Actually, I would say lead solid.
Unfortunately, we can barely see anything. At this location, even
starlight is largely absent. A handful of faint stars are scattered across
this pitch black sky. The illumination they impart onto us is negligible.
The temperature? Well below -200 from pole to pole. The atmosphere that
once enveloped this world has long since solidified and settled onto the
surface. Oceans? Well, we're strolling across one of them. Below our
feet is a column of super cold ice 3.7 miles thick. Although the deep
interior retains residual heat from radioactive activity, it is too deeply
embedded to affect the oceans. Water hasn't flowed here for millions of
years. Everything is frozen solid and will remain that way for hundreds
of millions of more years, if not much longer. You see, we're standing
on a runaway world, a planet careening through the unfathomably vast gulfs
of intergalactic space.
We came here on what is now Christmas morning 2021. That seemed
appropriate because on Earth many people are celebrating both Christmas and
winter's beginning. Here, on this barren frigid, dark, lifeless
planet, the concept of seasons is meaningless. Also nonsensical are
concepts of day and night. Yes, ths planet still rotates and has done so
since its formation, but it doesn't turn toward any star's warming fires.
We would only know of this rotation were we to remain here for 31
hours, During that time, we'd notice a fuzzy light patch slowly rise and a
few hours later attain its maximum altitude and then a while later set.
That patch is the Andromeda Galaxy, the grand spiral galaxy from which
this planet was expelled so long ago when Andromeda devoured a minor
satellite galaxy. The resultant dynamics and close stellar encounters
dislodged many stars and their attendant worlds and cast them into the wild
black yonder.
This sad, nameless world that hasn't welcomed any tourists before us since
time immemorial would have fared much better had it remained
gravitationally bound with its parent star. Had it done so, that star
would have bestowed copious amounts of heat energy onto it and kept the
land warm, the waters in liquid form and the life forms would have
thrived. Though winters might have proven to be harsh, they would have
also been finite in duration. Instead, we're walking across the
planet's deepest sea in an eternal winter. In fact, the planet might
have been better off had it remained within the Andromeda Galaxy where it
might have been captured by a star. Now, well, the chances are extremely
remote. The probability of a planet encountering a star out here is
about equal to the chance of two darts being randomly tossed in North
America and colliding tip to tip.
Why visit such an inhospitable world so far from home? Well, it gives us
an opportunity to discuss the concept of renegade or runaway worlds.
Astronomers believe that these planets might well number in the millions or
billions through the Universe. Not only do large galaxies devour smaller
ones, but planets and other bodies are often expelled from solar systems as
they form. Consequently, both interstellar and intergalactic space
could well be littered with these unattached worlds.
Apart from these imaginary wanderings, how could humans actually find any
of these Runaway or Rogue Planets? Some astronomers such as Dr. Takahiro
Sumi at the University of Osaka have used microlensing observations to
detect a few rogue planets without any associated stars. Even relatively
small bodies such as planets can distort more distant starlight by sending
that light gravitationally. In 2020, microlensing enabled astronomers
to detect their first Earth-sized Rogue planet, one named
OGLE-2016-BLG-1928.
In 2025, the Nancy Grace Roman Telescope -seen below- is scheduled to
launch. Part of this infrared telescope's aim is to image exo-planets and
search for runaway planets within the galaxy. Those outside of
galaxies are much more difficult to find.
[image: Wfirst_beauty1_prores_1920x1080.mov_.00_00_17_16.still003_crop.jpg]
So, Merry Christmas 2021 to those on Earth. We few standing here on his
world between galaxies are loitering on a place bereft of life, sound,
light or seasons. If nothing else, spending time here will renew our
appreciation for the Sun, even though, in winter, it serves as little more
than ornamentation.
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