*THE SOUTHWORTH PLANETARIUM*




*207-780-4249 <207-780-4249>       www.usm.maine.edu/planet
<http://www.usm.maine.edu/planet> 70 Falmouth Street  Portland, Maine 04103
43.6667° N,                    70.2667° W Founded January 1970*


*           "Trip the life fantastic." *




*THE DAILY ASTRONOMER*

*Monday. April 25, 2016*

*Renegade Worlds*















* Even by astronomical standards, this is a wild concept.  Imagine a planet
that was once part of a binary star system close to the galactic nucleus.
 (Yes, we've determined that binary star systems can harbor planets.* )
Next imagine a strange scenario in which said binary star system ventures a
wee bit too close to a black hole, not an uncommon sight (ha ha ha ha ha
ha) around the galactic nucleus.   When in close proximity to such a
powerhouse stellar remnant, the binary star system might experience a
violent disruption.    Not only will the disruption sever the system, it
might well propel the circumbinary planet at extreme speed away from the
wreckage.     Or, so goes this freshly baked scenario from the theoretical
astrophysics oven. The actually term describing these runaway worlds is
"hypervelocity planets."  And, not only do such renegade worlds exist, they
might be currently roaring away from the galaxy is a veritable swarm at
speeds that only interstellar protons can surpass.      Or, so asserts a
paper slated to appear in the Journal of the Royal Astronomical Society:
the same publication that's given us breathless page-turners such as
"Modeling the flaring activity of the high-x, hard X-ray selected blazar
IGR J22517+2217," and "The non-thermal emission of extended radio galaxy
lobes with curved electron spectra." The notion of runaway planets arose
from the discovery of hypervelocity stars more than seven years ago.**
These stars, like the hypothesized planets mentioned in the introductory
paragraph, were binary components ejected following their close approach to
a black hole.      Astronomers suspect that one star might be captured by
the black hole while the other flees.       A planet might either be
captured by the black hole or expelled at high velocity. At the moment,
though, the hypervelocity planet is theoretical, as none have yet been
discovered.   That astronomers haven't observed one yet is hardly
surprising.     How can one find a planet rushing around in the dark?
 At least hypervelocity stars still emit light and are therefore visible.
   Hypervelocity planets are invisible.   However, perhaps astronomers
might catch a glimpse of one as it passes along a star's line of sight.
For instance, if a star's brightness diminishes slightly over a brief time
period and doesn't experience the diminishment again, an astronomer might
conclude that the occulting object was one of these breakneck worlds.
 They could determine the speed by measuring the brightness diminishment
duration.     Of course, this technique is the ultimate long shot. What
would life be like on such a world?   Well, the answer is a quick
"impossible."    Any planet hurtling through space without the warmth and
light of a parent star would be barren and lifeless.   If it had an
atmosphere when it was orbiting a star, that atmosphere would rapidly
freeze out soon after being ejected from its parent stars.   That air
freeze-out wouldn't bode well for the life forms dependent on that air, of
course.     However, since the DA is nothing more than a pretend Universe,
we'll assume we can flourish on a space-cold rock.       One advantage is
the sky:   without a Sun, it would be perpetually dark.     And, if our
world is moving at speeds in excess of 2 million miles per hour, we could
actually observe the galaxy growing smaller over time as our world barrels
madly away from it.  Of course, as our distance from the home galaxy
increases, we'd slowly lose our view of its stars.      Computer models
suggest that these runway worlds would continue out of the galaxy and
beyond.     Even if the planet encounters an intergalactic star (a star
between  galaxies), it would likely remain uncaptured.    Traveling at such
a speed would make the world extremely difficult to snatch.       Perhaps
it would continue its voyage through the Universe always dark , cold and
speeding along at a rapid clip as its exhilarated inhabitants shout
"Righteous! Righteous!"*
*Wild...*





**NASA's Kepler Probe discovered Kepler 16-b, the first known circumbinary
planet - the term applied to a planet in orbit around two stars- in
September 2011. ** SDSS J090745.0+024507 was the first hypervelocity star
discovered.  Found in 2005 by astronomers at the Harvard-Smithsonian Center
for Astrophysics, SDSS J090745.0+024507 is escaping the Milky Way Galaxy at
2,400,000 km an hour (1,500,000 miles per hour.) *