This website has been created by and is supported by a group of Boston-area amateur astronomers. It is intended to be a convenient site to access news and information about astronomy and space-related activities of interest to the community and the public.
Introduction to Astronomy
Winter of 2012.
One of our meetings will be at a local observatory; there we will be able to use a large telescope to learn about the sky first-hand.
We look forward to seeing you!
The Sky in January 2012
Phases of the Moon:
|
First Quarter Moon |
January 1 |
1:15 AM EST |
|
Full Moon |
January 9 |
2:30 AM EST |
|
Last Quarter Moon |
January 16 |
4:08 AM EST |
|
New Moon |
January 23 |
2:39 AM EST |
| First Quarter Moon | January 30 | 11:10 PM EST |
The Moon
and Planets:
The waxing gibbous Moon lies about
5° to the N of Jupiter on January 2nd. A waning
gibbous Moon passes about 10° to the S of Mars on the 14th.
On the 16th, a waning gibbous Moon lies to the S
of Spica and Saturn. A waxing crescent Moon passes about 7°
N of Venus on the 24th, and passes to the right
of Jupiter in the evening sky on the 29th and 30th.
Evening Planets
(after sunset):
-
Venus, in SW
-
Neptune, in SW
-
-
-
Visible At Midnight:
Jupiter, in W
Mars, in E
Morning Planets (before sunrise):
Mars, in SW
Saturn, in S
Comet C/2009 P1
(Garradd), in Hercules, may brighten from magnitude 7.1 to 6.8.
It is best seen in the early morning. As January begins, the
comet rises about 4.5 hours before the sun; at month’s end, it
comes up before midnight local time, and by sunrise is halfway
up to the zenith.
Meteors:
The Quadrantid meteors peak around January 4th.
The gibbous Moon will set around 3 AM, so will not interfere
with viewing the meteors in the early pre-dawn hours. The
shower averages a respectable 120 meteors per hour, so
getting up early and braving the cold can be well worth the
effort.
The Solar System in January
Current Night Sky: the Solar System:
The Planets
Venus shines like a beacon high in the SW after sunset; it is now bright enough and high enough to draw attention from even the most casual viewer of the skies. As January begins, it sets two and three-quarters hours after the Sun; by month’s end, it stays up for three and a third hours after sunset. On the first, it is 22° above the horizon at sunset (for observers at 42° N); by month’s end, it is 10° higher – a third of the way to the zenith! It brightens slightly during the month – from magnitude -4.0 to -4.1, making it brighter than any point of light in the sky. This is just the beginning; Venus will be getting further from the Sun and brighter well into spring. Through a telescope, Venus appears as a gibbous globe – 83% illuminated and 12.9 arc-seconds across on the 1st and 75% illuminated and 15.0” across on the 31st.
Venus passes close to 8th-magnitude Neptune on January 12th- 13th; brilliant Venus can be your guide to finding Neptune, which lies about 1.2° to its N. Of course, you will need binoculars or a telescope to spot the ice giant. A moderate scope will show it as a disk just 2.2” across. By the end of January, Neptune will have disappeared into the evening twilight.
Uranus lies a constellation to the E of Neptune, in Pisces. If you can find the faint “Circlet” stars of Pisces, look about 6° to its E. Uranus shines at magnitude +5.9; a telescope shows its faint blue-grey disk about 3.4” across.
Mighty Jupiter lies high in the S as darkness falls. It crosses the boundary from Pisces into Aries on January 8th; there are no bright stars in the area, so Jupiter dominates this region of the sky. It dims slightly during the month – from magnitude -2.6 to -2.4 – but remains the most brilliant point of light in the entire sky aside from Venus. The view through a telescope is impressive; the planet shrinks somewhat during the month - from 43.4” to 39.3” across at the equator - but the disk is large enough to show plenty of detail even in small scopes. The dark North Equatorial and South Equatorial Belts flank the broad, light-colored Equatorial Zone on either side. Depending on seeing conditions, a profusion of smaller belts and zones may be visible all the way up to the high-latitude Polar Regions. At higher magnifications, these features and the boundaries between them reveal a complex and ever-changing structure. The nature of these atmospheric features has been undergoing study, debate, and speculation for centuries. (See our “What’s New” section for more information.) In addition to the planet itself, Jupiter’s four large moons – Io, Europa, Ganymede, and Callisto – repay close attention in their ever-changing configurations as they orbit the planet.
Mars rises about 10:00 PM local time at the beginning of January, and over an hour and a half earlier by month’s end. On the 14th, it crosses from Leo into Virgo. It almost doubles in brightness this month, going from magnitude +0.2 to -0.5. A telescope will show its diameter as increasing from 9.0” to 11.7”. Most likely, the first feature to come into view will be the north polar ice cap; it is spring in the Northern Hemisphere of Mars, but the polar cap will still be the most prominent feature on the planet. The larger “dark areas” will be increasingly visible as Mars nears opposition (and thus closest approach) in early March.
Saturn, in Virgo, rises after 1 AM local time on January 1st, but is up at 11:30 PM by month’s end. The best time to view it is in the early hours before sunrise, when the planet has had a chance to rise high in the SE sky. Saturn remains within about 7° of Spica all month; its magnitude dims from +0.7 to +0.6 – slightly brighter than the star’s +1.04. (Numerically lower magnitudes are brighter in the standard astronomical magnitude scale.) It takes a telescope – almost any telescope will do – to reveal Saturn’s true glory. The diameter of the planet’s globe increases from 16.7” to 17.6” across this month, with the diameter of the visible ring system increasing from 37.9” to 39.9”. Most gratifyingly, the rings are now inclined about 15° to our line of sight, giving us good views of details such as the Cassini Division – the narrow gap between the inner B Ring and the outer A Ring. Eighth- magnitude Titan is usually visible, along with a number of the smaller moons. Check the web link at the end of this Sky Report for identifying the individual satellites.
Mercury is visible in the pre-dawn sky the first half of January. On the 1st, it shines in the SE at magnitude -0.4. A telescope shows it as a gibbous disk 80% illuminated and 5.7” across.
Dwarf Planets/Asteroids:
Pluto is too close to the Sun to be observable this month.
Eight-magnitude Ceres passes from Aquarius into Cetus on January 2nd, from Cetus into Pisces on the 27th, and finally back into Cetus on the 30th. On January 10th, it lies about 9° due S of Uranus. On the 20th, it lies about 1.75° to the NE of Iota Ceti.
Vesta is in
Aquarius. It can be found about 5° SE of brilliant Venus on the
23rd, and about 4.5° due S of Venus on the 29th.
Not for nothing is
the planet Jupiter known as a “Gas Giant”. Without restating
the obvious, when we observe Jupiter and its wonderful
panoply of patterns and colors, we are not seeing the solid
surface of the planet; we are seeing only the visible top of
its atmosphere, which may extend downwards for thousands of
miles toward its center. Indeed, there has sometimes been
debate as to whether Jupiter even has a solid surface! What
we do know comes from visual observation, remote sensing at
a variety of wavelengths, computer modeling, and data from
one probe (Galileo) which entered Jupiter’s atmosphere in
1995.
It is though that
the visible cloud layers are composed of ammonia and ammonia
hydrosulfide ice crystals. Beneath those there should be a
layer of water ice, followed deeper down by the materials
composing the planet’s deep interior.
Vertical structure of
Jupiter’s atmosphere.
The
altitude on the left axis refers to altitude with respect to
an arbitrarily-defined pressure level, rather than a solid
surface.
However, this is far
too static a picture. Jupiter’s light-colored zones are
actually locations where atmospheric material is coming up
from below. The dark-colored belts, such as the Equatorial
Belts, are locations where the material – presumably altered
somehow by exposure to sunlight – descends back to the
“surface”.
The Material flow in Jupiter's atmosphere.
Also involved in this process must be small or trace quantities of compounds that produce the stunning panorama of form and color we see from telescopes on Earth. Hopefully, understanding some of the processes occurring on Jupiter will deepen our appreciation of planetary phenomena in this Solar System and others.
The Sky in January
9:00 PM EST on January 15th
Looking at Zenith, South at Bottom.
(click to enlarge)*
In all of the sky charts you see
here on the Sky Report, you may note a healthy collection of
“M”, or Messier objects. Examples this month range from the
famous M42 (the “Great Nebula in Orion”) and M45 (the
Pleiades) to the relatively obscure M93 in Puppis and M50 in
Monoceros. What are these objects and where did their names
come from?
The Messier list was begun in 1771 by the French comet-hunter Charles Messier and his assistant Pierre Méchain. They set out to compile a list of objects easily confused with comets, and therefore to be avoided. Their list ultimately contained 103 open clusters, nebulae, globular clusters, and other objects they catalogued. Since then others have added a handful of items to the catalog, which now runs from M1 to M110 – with a few dubious or suspect objects included. The irony is that now, amateur astronomers seek out these Messier objects as worthy of study and admiration in and of themselves!