THE SOUTHWORTH PLANETARIUM
207-780-4249 www.usm.maine.edu/planet
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70 Falmouth Street Portland, Maine 04103
43.6667° N 70.2667° W
Altitude: 10 feet below sea level
Founded January 1970
Julian date: 2458750.5
2019-2020: XVII
"When you're different, sometimes you don't see the
millions of people who accept you for what you are. All you notice is the
person who doesn't." -- Jodi Picoult
THE DAILY ASTRONOMER
Wednesday, September 25, 2019
Interstellar Visitor
We don't know where it's been, but we do know where it's going. We know
its character, but not its origin. We know where it is currently located,
but we don't know precisely how it arrived there. The "it," to which
we're referring, Mr King, is Comet C/2019 Q4 Borisov. The graphic below
shows its path, both past and future, as it hurtles through our solar
system. This comet is scheduled to reach perihelion, the closest point to
the Sun, on December 8, 2019. Even at this "close approach," the comet
will only come to within 196 million miles of Sol. (It isn't expected to
veer anywhere near Earth, either).
[image: 20190913_interstellar-comet-illustration-tps_f840.jpg]
*Feeling hyperbolic? * Comet C/2019 Q4 Borisov is quite likely the second
known interstellar object to have been identified. This interstellar
comet is traveling along a hyperbolic orbit that brought it into our
planetary neighborhood and will swiftly convey it away, never to return.
Comet C/2019 Q4 Borisov* is attracting a great deal of attention because
many astronomers believe it to be an interstellar object. It originated
from another solar system and just happened to encounter our solar system
during its interminable odyssey through the Milky Way Galaxy. More
orbital analysis will be necessary before astronomers can conclusively
identify it as being of interstellar origin.
If it is determined to be from elsewhere, Comet C/2019 Q4 Borisov will be
only the second interstellar object discovered. The first was an enigmatic
projectile called "Oumuamua"**. Some people still believe it to have been
an alien spacecraft or at least a fragment of a craft as it exhibited
strange motions when approaching the Sun, similar to the behavior of a
solar sail designed to exploit radiation pressure as a propulsion source.
Many researchers discount this notion out of hand as they ascribed the
motion to the interplay between solar radiation and what perhaps could have
been a highly reflexive region within the object. In any event, the
issue will likely remain unresolved as Oumuamua has swooped out of the
solar system for distant parts of the galaxy. As one astronomer quipped,
"If it was intended as an invading spacecraft, the onboard aliens are
either asleep or stupid."
Astronomers estimate that millions of such renegade objects have been
propelled out of their respective solar systems and are currently careening
through interstellar space. Being well concealed within the darkest
hollows well removed from stars, these objects are virtually impossible to
detect until they venture into the solar system and reflect sufficient
light so as to render themselves observable.
The notion that these objects are alien craft deployed to explore other
solar systems proves quite appealing to those who believe/want the galaxy
to teem with life. While the existence of extraterrestrial beings remains
unresolved, we can confidently assert that when it comes to comets, those
that are gravitationally bound to the Sun are certainly not alone.
*What's in a name? Well, for this object, the name says quite a lot. The
"C" designation is reserved for comets. "2019" denotes the discovery
year. Q4 is all bookkeeping. The first comet discovered in 2019 was
labeled A1, the second A2, and so forth. Every half month, the first
letter changes. Borisov is the last name of the comet's discoverer,
Crimean astronomer Gennady Borisov.
**Oumuamua: from a Hawaiian term roughly meaning "scout."
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