THE SOUTHWORTH PLANETARIUM
207-780-4249       www.usm.maine.edu/planet
70 Falmouth Street  Portland, Maine 04103
43.6667° N,                    70.2667° W
Founded January 1970
                "340 days until Christmas"





THE DAILY ASTRONOMER
Tuesday, January 19, 2016
Five Planets

For the first time since 2005, all five naked eye planets,* will be
visible simultaneously in the pre-dawn skies starting tomorrow!
Those hearty sky watchers who are either impervious to or highly
tolerant of the bitter cold can venture outside at 6:00 a.m. to see
Jupiter, Mars, Saturn, Venus and Mercury.

The first planet to rise, Jupiter, appears around 10:00 p.m.      This
behemoth world heralds the eventual appearance of the lesser planets.

Mars follows around midnight.   Though not as bright as Jupiter, the
fourth planet's reddish color makes it distinct against the backdrop
of white stars.

Next comes Saturn: the most distant of the naked eye planets.
Yellowish in appearance, Saturn is also dimmer than Jupiter and, in
terms of color contrast, not as distinctive as Mars.  However, like
the other planets, it doesn't appear to twinkle, as the stars do. This
twinkle, or scintillation, affects stars more than planets because the
former is a pin point light source.  The latter, being disc like,
exudes a more concentrated light.

Venus arrives next in the very early morning, when the sky is
tinctured by the first hints of twilight.  Venus is the brightest of
the five and, therefore, the easiest to observe.

Finally, Mercury emerges as the twilight brightens.     Of the five
naked eye planets, Mercury will be the most difficult to find.
As it is the closest planet to the Sun, Mercury never appears to stray
far from it.


We'll have the opportunity to see all these planets for the next few
weeks, at which point Mercury will dive below the eastern horizon.
  The best time to venture out is late January, when Mercury will be
in a more favorable position.       One will notice that the planets
seem to describe an arc through the sky, as opposed to being scattered
in all directions.  This alignment is no coincidence.     When
forming, the solar system spread out like a disc.  The planets formed
from the peripheral gas surrounding the Sun and therefore are
positioned along this disc.      Earth travels along the same disc.
In fact, Earth's orbital plane defines the "ecliptic," which we
perceive as the Sun's apparent annual path through the heavens.
The planets travel along a narrow band centered on this ecliptic
because they are moving within the same disc in which the Sun
revolves.

Planet watchers rejoice!  All five visible planets are up for viewing.


*Mercury, Venus, Mars, Jupiter and Saturn are deemed the "naked eye
planets" as they are observable with just the unaided eye.    Of
course, some astronomers claim that Uranus is also a naked eye planet
when at its maximum brightness.     While this statement is true, even
at its brightest, Uranus only looks like a faint star.