Download Friends newsletter december 2011

FRIENDS OF THE PLANETARIUM NEWSLETTER – DECEMBER 2011
Season’s greetings everyone. The southern summer solstice, with the Sun highest and the hours of
daylight longest, is on December 22. Morning twilight will start well before 5am NZDT, with the Sun
rising before 6am NZDT all month. In the evening, twilight will persist until well after 10pm, especially
in the south of NZ. Obviously it is not the astronomer’s preferred time of year for nocturnal viewing.
Still, the planet viewing is quite good these days. Venus will be easily visible in the early evening sky
throughout January, setting close to 2 hours after the Sun all month. Half an hour after the Sun goes
down, Venus will be an obvious object about 15 degrees up, a little to the south of west. Jupiter will be
readily visible in the evening sky, best seen as soon as the sky darkens to the northwest. It will get lower
later in the evening. The planet sets about 2am on January 1, by midnight on January 31. The planet
starts January in Pisces but on the 8th crosses back into Aries, which it left in early December. Mars
starts to move into the evening sky in January after having been in the morning sky for the last 10
months. It rises at 12.30 am on the 1st, 10.40 pm on the 31st. By then it will have brightened to
magnitude -0.5, starting to lead up to its opposition at the beginning of March. But during January Mars
will still be best seen in the morning sky. At midnight on the 31st it will be only 14 degrees up, half way
between east and northeast. Mars will be the brightest object in that part of the sky. Saturn will be easily
visible in the morning sky before dawn to the northeast during January. It rises about 2 am at the
beginning of January and close to midnight by the end of the month. The planet at magnitude 0.6 will be
about 6.5 degrees below Spica, which at magnitude 1.1 is the brightest star in Virgo. We may even be
lucky enough to see a comet in January. Comet Levy will move higher into southern skies during
January. It is expected to brighten to magnitude 8.1 by mid January, so should be visible in binoculars as
a faint fuzzy patch. On January 14 it will be 6.5 degrees to the left of Jupiter and only a little further from
the planet for a couple of evenings either side of that date. As we gaze up at Jupiter, scientists on Earth
are still analyzing data sent back by the Galileo probe in the 1990s. In a potentially significant finding in
the search for life beyond Earth, scientists studying
data from NASA's Galileo probe have discovered
what appears to be a body of liquid water the
volume of the North American Great Lakes locked
inside the icy shell of Jupiter’s moon Europa. The
data suggest there is significant exchange between
Europa's icy shell and the ocean beneath. This ocean
is deep enough to cover the whole surface of Europa
and contains more liquid water than all of Earth's
oceans combined. However, being far from the Sun,
the ocean surface is completely frozen. Most
scientists think this ice crust is tens of kilometers
thick. This information could bolster arguments that
Europa's global subsurface ocean represents a
potential habitat for life elsewhere in our solar
system. The water could represent a potential
habitat for life, and many more such lakes might
exist throughout the shallow regions of Europa’s
shell.
On Mars, the search for evidence of a watery past continues. While looking for a safe place to weather
the cold Martian winter, the rover Opportunity spied a subtle yet intriguing feature on the edge of the
giant Endeavour crater: a bright vein of light-toned rock piercing the ruddy, rocky surface of a large rise
called Cape York. The vein (dubbed "Homestake") may prove to be hard evidence of phyllosilicates,
minerals formed in the presence of a watery environment. If this is the case then this chance discovery
would mean that
Opportunity, after
nearly eight years on
Mars, has literally
stumbled upon the
"Holy Grail" of its entire
mission. These minerals
are sure signs of past
water, most likely salty
water that could have
been highly conducive
to the development of
life. Opportunity is now
facing its fifth Martian
winter and the MER team must soon plan driving maneuvers to place it at a prime location to weather
the long months of frigid temperatures and reduced sunlight. Most importantly it will need to find a
north-facing slope that will position it at a ten- to fifteen-degree angle, to take best advantage of the
available sunlight on its already dusty solar panels. While this potential discovery is undoubtedly
exciting, Opportunity's ultimate survival must take precedence. Once the six-month-long Martian winter
is over, Opportunity can resume exploration of the area around Cape York, an area that has already
proven itself to hold promises of many never-before-seen features.
Closer to the Sun, the MESSENGER spacecraft has been sending back very detailed images of the surface
of Mercury. Here is a mosaic of images showing the limb or edge of Mercury in incredible detail.
To finish off this newsletter, here’s an interesting tidbit about the nature of time. While our units for
measuring time seem to be here to stay, the way we measure time has changed significantly over the
centuries. The Ancient Egyptians used sundials and waterclocks, as did several civilisations after them.
Hourglasses were also an important time-keeping device before the invention of mechanical and
pendulum clocks. The development of modern quartz watches and atomic clocks has enabled us to
measure time with increasing accuracy. Today, the standard definition for time is no longer based on
the rotation of the Earth around the Sun, but on atomic time. A second is defined as: "9,192,631,770
periods of the radiation corresponding to the transition between the two hyperfine levels of the ground
state of the caesium-133 atom." Whaaat?????? Best wishes for 2012.