Here’s our quad-weekly report on happenings in the skies from the always-awesome Gordon Johnston. Not as exciting as last month’s report (no Venus transits the next four weeks), but still some exciting stuff to gaze at. Anyways, check it out:
The next full Moon is on Tuesday, July 3, 2012. The Moon will be opposite
the Sun at at time when we cannot see it (2:52 pm EDT), but will appear full
for about 3 days centered on this time, from late Sunday night/early Monday
morning through early Thursday morning.
This full Moon has many names.
* For Hindus this is the Guru Full Moon (Guru Purnima) and is celebrated
as a time for clearing the mind and honoring the guru or spiritual master.
* Europeans called July’s full Moon the Hay Moon or the Mead Moon.
* The Algonquin tribes in what is now the Eastern US called July’s full
Moon the Buck Moon, as July is normally the month when the new antlers of
buck deer push out of their foreheads in coatings of velvety fur. They also
called this the Thunder Moon because of July’s frequent thunderstorms.
Since this is the Thunder Moon, a quick note on lightning safety. Most of
the lighting that strikes the ground arcs from the negatively charged bottom
of the storm to the ground underneath the storm. Much more rare is positive
lightning, which arcs from the top of a thunderstorm to strike the ground up
to eight miles away from the storm. Positive lightning can sometimes strike
areas where the sky is clear (hence the term “bolt out of the blue”).
Because it arcs across a greater distance it tends to be 5 to 10 times more
powerful that regular ground strikes. Though positive lightning is rare
(less than 5% of all lightning strikes), the lack of warning combined with
its greater power tends to make it more dangerous. A good rule to follow is
if you can hear the thunder, you can be struck by the lightning. As a
bicycle commuter I am well aware that the inch or so of rubber tire between
my metal bicycle and the ground will make little difference to a bolt that
can arc across miles of air from the top of a thunderstorm to the ground. Be
As usual, suitably celebratory celestial attire (e.g., Aloha shirts, bow
ties, etc.) is encouraged in honor of the full Moon. Also, watch out for
lightning and consider setting aside a little time to clear the mind.
As to other sky events between now and the full Moon in early August:
We are currently in the period with the latest sunset of the year. For NASA
Headquarters and the Washington, DC area, rounded off to the minute, sunset
is 8:37 pm for the two weeks from Wednesday, June 20, 2012 to Wednesday,
July 4, 2012. Our 24 hour day is based on the average length of the solar
day throughout the year. Right now the solar days are slightly longer than
24 hours. Even though the Summer Solstice on June 20th was the day with the
longest daylight of the year, the earliest sunrises occur before the
Solstice and the latest sunsets occur after the Solstice.
In late June, when the sky finally does get dark (nautical twilight ends
around 9:50 pm), three planets are visible in the western sky. Mercury is
very low on the horizon in the west northwest, Mars is high up to the west
southwest, and Saturn even higher from the horizon in the southwest. During
July Mercury will appear to plunge towards the Sun, disappearing in its
glow, and by July 28th Mercury will be passing between the Earth and the
Sun. In the mornings Venus and Jupiter are visible, appearing higher in the
sky as the month progresses.
On Friday, June 29, 2012, Pluto will be at at opposition. This is as close
as it gets for the year, about 4,673,400,000 km or 2,903,900,000 miles from
Earth. If you have a really good telescope (at least 8 inches in diameter)
and can see Pluto, the light you would see would have left the Sun about 8
hours and 48 minutes before, passing near the Earth after about 8-1/2
minutes, taking 4 hours 20 minutes to get to Pluto, then bouncing back
towards the Earth, taking another 4 hours 20 minutes to get to your eye. No
spacecraft has ever visited Pluto, but the New Horizons mission is on its
way. NASA launched the New Horizons spacecraft on January 19, 2006, it is
the fastest spacecraft humans have ever launched, and it will get to Pluto
in another 3 years (Summer of 2015).
Also on Friday, June 29, 2012, a Near-Earth Object (NEO) called 2012 MY2
will pass by the Earth at about 1.3 times the distance between the Earth and
the Moon. This object is between 15 and 30 meters in diameter.
On Saturday, June 30, 2012, Mercury will be at its greatest elongation, 25.7
degrees east of the Sun in the evening sky. Look low near the horizon to
the west northwest shortly after sunset. Because Mercury orbits close to
the Sun, this is about as high above the horizon as it ever gets (when the
sky is dark enough see it). I once saw a total eclipse of the Sun, which
included clearly seeing Mercury high in the sky, but this was only because
the Moon was blocking the Sun, making the sky dark enough to see stars and
planets. The first mission to orbit Mercury, NASA’s MESSENGER spacecraft,
continues to send back surprising new information about this planet closest
to the Sun.
In the morning on Sunday, July 1, 2012, at about an hour before sunrise
(about 4:45 am for the Washington, DC area), Venus and Jupiter will appear
near each other, with the bright star Aldebaran nearby. Later on July 1st
the Moon will be at its closest to the Earth for this orbit.
As mentioned above, the full Moon is on Tuesday, July 3, 2012.
On Wednesday, the 4th of July, 2012, just before midnight EDT, the Earth
will be at aphelion, the farthest away from the Sun it gets in the year.
Aphelion is at 1.017 astronomical units, 152,100,000 km, or 94,540,000 miles
from Sun. Since the Sun is about 1.7% farther from the Earth than the
average Earth-Sun distance and the intensity of light varies as the square
of the distance, sunlight a Aphelion is about 3.3% less intense than on
average. One of the reasons the seasons in the northern hemisphere are less
extreme than in the southern hemisphere is that sunlight is less intense
during northern summers and more intense during northern winters.
In the morning of Monday, July 9, 2012, Venus will appear close to the
eastern horizon, within a degree of the bright star Aldebaran, with Jupiter
Tuesday, July 10, 2012 is the last quarter Moon.
On Friday the 13th of July, 2012, the Moon will be at apogee, approximately
404,800 km or 251,500 miles from Earth.
On Sunday morning, July 15, 2012, the waning crescent Moon, Venus, Jupiter,
and the bright star Aldebaran will form a cluster near the eastern horizon.
The new Moon is on Thursday, July 19, 2012.
In the evening on Monday, July 23, 2012, the waxing crescent Moon will
appear to line up with Mars and Saturn near the west southwest horizon.
By Tuesday, July 24, 2012, the waxing crescent Moon will have shifted to
form a triangle with Mars and Saturn, with the bright star Spica nearby.
The first quarter Moon will be on Thursday, July 26, 2012.
The Delta Aquarid meteor shower appears to radiate from the southern part of
the sky (and are generally easier to see from the southern hemisphere).
This meteor shower does not have a strong peak, but reach a maximum rate of
about 15 to 20 meteors per hour on the weekend of July 28 and 29, 2012 (to
see meteors at this rate you will need to have clear skies, a clear view of
the sky, and be far away from city lights). The best time to watch is after
the Moon sets but before the sky starts to lighten for dawn (around 5 am EDT
for the Washington, DC area). For the Washington DC area, on Saturday
morning July 28, 2012 the Moon sets at 1:18 am EDT and on Sunday it sets at
2:13 am EDT.
In the morning on Monday, July 30, 2012, Jupiter will appear about 5 degrees
from the bright star Aldebaran.
The full Moon after next is on Wednesday, August 1, 2012.