Current
Astronomy "Headlines"
Last Quarter
July 04
|
New Moon
July 11
|
First Quarter
July 18
|
Full Moon
July 25
|
Listed
below are notable astronomical events coming up for the month of
July 2010:
Naked-Eye
Planets
Mercury
Mercury begins July setting only about 4.5 degrees from the Sun,
since it has just come out of superior conjunction with the Sun,
in the constellation of Gemini. The young, waxing crescent Moon
meets up with Mercury in Cancer on the evening of the 12th, and
then crosses into Leo, coming into a conjunction of less than half
a degree with the star Regulus of Leo on the evening of the 27th.
Mercury ends the month setting at about 9:30 p.m. in Leo. This month
will probably be one of the best out of the year in which to view
Mercury in the evening, setting a little after 9:30 p.m. for several
days to either side of the 23rd of the month. Mercury shines at
magnitude 0.2 and displays a disk size of 6.91arc-seconds by the
end of the month. This is both brighter and bigger than the planet
Mars appears at this same time of month!
Venus
Venus starts the month of July setting at 11 p.m. at about 9.5 degrees
west of the star Regulus in Leo. On the 9th of the month, Venus
passes just outside of 1 degree away from the aforementioned Regulus,
then is itself passed by the waxing crescent Moon on the evening
of the 14th. Venus continues through Leo, reaching the western border
of that constellation by the end of the month, when the bright planet
will set a little before 10:30 p.m. At this time, Venus shines at
magnitude -4.2, its disk diameter is 19.97 arc-seconds – small
compared to what it will become later in the year as Venus close
the distance gap between itself and our Earth! – and it sports
a phase of 0.58 - a nearly “Last Quarter” Venus!
Mars
The Red Planet is almost exactly in between the star Regulus of
Leo and the planet Saturn in western Virgo along the line of the
ecliptic at the beginning of July. ON the evening of eth 10th Mars
passes 1 degree south of the dim star Sigma Leonis, and is itself
bypassed by the waxing crescent Moon (and making a right triangle
with Mars and Saturn) on the evening of the 15th. On the 19th of
the month, Mars crosses into the constellation Virgo and on the
24th of the month, passes in close conjunction (< 0.5 degree!)
of the star Zavijava / Beta Virginis. On the 30th, Mars passes into
a close conjunction (< 2 degrees) with the planet Saturn, and
by month’s end, Mars has passed Saturn and is setting at about
10:45 p.m. Mars is shining at magnitude 1.5 (slightly dimmer than
the brightness of Regulus). Mars sports a small, ever-shrinking,
4.69 arc-second diameter disk (this is only about 1 arc-second wider
than the planetary diameter of the disk of the planet Uranus as
seen from Earth at this time.)
Saturn
Saturn is decently high in the WSW sky in western Virgo at the beginning
of July, just over 2 degrees straight up from the much dimmer star
Zavijava / Beta Virginis while facing that direction. The waxing
crescent Moon makes its closest pass to Saturn on the 15th of the
month at about 10.5 degrees SW of the Ringed Planet, forming a right
triangle with the steadily-approaching planet Mars. The planet Mars
(and Venus, from farther away) steadily catch up with much-slower
Saturn’s position in the sky, until Mars comes into closest
conjunction with Saturn at less than 2 degrees away on the 30th.
By month’s end, Saturn forms a very long, thin triangle with
Mars and Venus (at nearly 7.5 degrees away and closing). Saturn
will lose quite a bit of evening height by month’s end: it
sits at only about 16 degrees above the WSW horizon at 9:30 p.m.
local time, then sets at a bit after 10:45 p.m. Our Saturn-viewing
nights are quickly running out for this year – next month
will be the last in which it will be high enough to see in the evening
until about late March of next year! View it now while you can!
If you have even a modest telescope, you should be able to observe
Saturn and its ring system in the eyepiece beginning with modest
power (at least 30x-35x). In addition, Saturn’s largest moon,
Titan, can nearly always be seen relatively close to the planet.
With good seeing conditions, up to nearly a half-dozen other Saturnian
satellites are within reach of most moderately-sized backyard telescopes!
At the end of the month the rings’ major axis is 37.1”
and minor axis is 1.5”. At this time, Saturn will shine at
magnitude 2.1 and show an equatorial diameter of 16.34 arc-seconds
and a polar diameter of 14.58 arc-seconds.
Jupiter
Jupiter rises at a little before 1:00 a.m. in western Pisces on
the 1st of July, only about 2.5 degrees east of the far-dimmer planet
Uranus. On the morning of the 3rd, the near-Last Quarter Moon makes
its closest pass at 8 degrees NW of the planet, then again on the
30th at about 6 degrees NNE of the planet. At the end of the month
Jupiter rises at just before 11:00 p.m. just over 3 degrees east
of the planet Uranus. Jupiter is showing signs of slowing down its
forward annual motion as it gets ready to retrograde next month.
If you stay up late enough, you can observe the giant Jupiter in
a telescope, revealing cloud bands and the 4 Galilean moons. Even
a pair of binoculars, though, will reveal at least some of these
4 moons, provided you can hold your binoculars steadily enough!
At this time, Jupiter shines at a brightening -2.7 magnitude, and
sports a large and still-growing disk with a 45.74 arc-second equatorial
diameter, and a 42.78 arc-second polar diameter!
Telescopic
Planets
Uranus
At the beginning of July, Uranus starts off the month setting a
little before 12:35 a.m. in western Pisces about 2.5 degrees west
of Jupiter. On the morning of the 3rd the near-Last Quarter Moon
passes within about 5.5 degrees of Uranus, and and the waning gibbous
Moon bypasses again on the evening of the 29th / morning of the
30th. By month’s end, Uranus rises at about 10:35 p.m. a little
over 3 degrees west of Jupiter, and now coming around into the evening
sky again! It is possible to observe Uranus through binoculars or
telescopes as a pale blue, steadily-shining “star” in
binoculars, and a small telescope at moderate-to-high power (about
75x or more) will reveal its disc (magnitude 5.8, and 3.60 arc-seconds
on 7/31).
Neptune
Neptune is in western Aquarius just under 2 degrees north of the
star Iota Aquarii, rising at a little before 11:15 p.m. at the beginning
of July. Neptune is in retrograde motion this month, and will appear
to move westward with respect to the constellations. The waning
gibbous Moon passes about 3.5 degrees away from Neptune on the evening
of the 27th. By month’s end, Neptune will rise at a little
before 9:15 p.m. Neptune appears as a slightly deeper blue-hued
“star” in binoculars than Uranus normally does, but
also much less bright. A telescope will barely reveal a very small
disc (magnitude 7.8, and 2.31 arc-seconds on 7/31) at high power
(150x or more).
Dwarf
Planets
Ceres
The dwarf planet / asteroid
Ceres is already risen after sunset in the constellation Ophiuchus,
just NE of the “spout” of the “Teapot” asterism
of the constellation Sagittarius, at just about 3.5 degrees ESE
of the star Theta Ophiuchii at the beginning of July. The nearly-Full
Moon passes closest on the evenings of the 21st and 22nd. Ceres
will exhibit retrograde motion against the background of stars this
month, just like last month, and by the end of the month Ceres will
be only a little over 2 degrees south of the aforementioned star
Theta Ophiuchii. An observer will be able to view Ceres with a telescope
(although a detailed star chart will be necessary to pinpoint its
position), although far from glaringly, and even then Ceres’
disc is too small to be seen through any but the largest professional
ground-based telescopes. Ceres should appear as a “dot”
of a star, much like Pluto, only it will be visible with MUCH more
modest viewing equipment! On the last day of the month, Ceres’
magnitude is 8.1.
Pluto
In the month of July,
tiny Pluto is already risen after sunset in northern Sagittarius,
a little under 3 degrees NNE of the star Mu Sagittarii. The near-Full
Moon passes at just under 9 degrees to the ESE on the 23rd of the
month. This month will be the easiest in the entire year in which
to spot Pluto through a telescope, for those so inclined! By the
end of the month, Pluto is over 30 degrees above the SSE horizon
at roughly 3 degrees dues north of the star Mu Sagittarii after
sunset. Although now classified as a dwarf planet, Pluto still makes
as possible a telescopic target as it ever did, under the right
conditions! With observing experience, a great deal of patience
and persistence, as well as an excellently-detailed star map, a
dedicated observer may be able to spot Pluto using the aforementioned
Mu Sagittarii (at magnitude 3.58) as a dim, but visible, guide star.
Be prepared for a challenge, though. The icy dwarf planet is only
visible as a very modest, slight “dot” of a star in
a telescope of at least 8”-10” aperture. A very detailed
star chart (as well as a great amount of patience and endurance!)
is vitally necessary in order to spot it! Pluto glows feebly at
magnitude 14.0.
*****
*****
Meteor
Showers - http://amsmeteors.org/showers.html
Viewable
Comets - http://cometography.com/current_comets.html
Special
events - http://www.skyandtelescope.com/observing/highlights
|
