Every month (or so), Gordon Johnston sends out an email with historical info on the naming of that month’s moon, tips for observational astronomers, and some info about the planets. Below is this month’s effort. As always, huge thanks to Gordon for writing this up and letting us re-post it here!
The next full Moon is on Monday, June 4, 2012. The Moon will be “opposite”
the Sun at 7:12 AM EDT Monday morning, and will appear full for about 3 days
centered around (i.e., from Saturday evening morning through Tuesday
This full Moon is known as the Strawberry Moon, a name universal to just
about every Algonquin tribe. The name comes from the relatively short
season in June for harvesting strawberries in northeastern North America.
Europeans call the June full Moon the Rose Moon. Some believe the name Rose
Moon comes from the color the Moon can get because, particularly for
locations at the higher northern latitudes, the full Moon rides lower in the
sky, shining through more atmosphere, than at other times of the year. The
orbit of the Moon around the Earth is almost in the same plane as the orbit
of the Earth around the Sun (only about 5 degrees off), so when the Sun
appears highest in the sky near the summer solstice, the full Moon opposite
the Sun will always ride lowest in the sky.
A new tribe has also given this full Moon a name. This new tribe is
geographically scattered but mostly living in the mid-Atlantic region of the
United States. This tribe’s language is primarily English, but with a
liberal smattering of acronyms and Hawaiian phrases (cheerfully contributed
by the Deputy Project Manager). Comprised of people from all backgrounds,
this tribe is devoted to the study of the Moon. This tribe calls June’s
full Moon the LRO Moon, in honor of the Lunar Reconnaissance Orbiter
spacecraft they placed in orbit around the Moon on June 23, 2009.
There is a partial eclipse with this full Moon. For those of us in the
Washington, DC area, we will not be able to see much. The Earth will begin
blocking some of the sunlight headed for the Moon at 4:48 AM EDT on Monday
morning, but since the partial Sun will still be illuminating all of the
Moon, the reduction in brightness will be gradual and difficult to see. For
the Washington, DC area, the Moon sets at 5:42 am EDT, 18 minutes before the
full shadow of the Earth begins to darken part of the Moon. People living
farther to the west will have a better view of this partial lunar eclipse.
There are currently five spacecraft operating in orbit around the Moon, LRO,
two GRAIL Spacecraft (Ebb and Flow), and two ARTEMIS spacecraft. These
spacecraft rely on sunlight to keep warm and provide power to operate.
Unlike last year’s two long eclipses, this will be a short eclipse. LRO,
for example, will preheat some of its systems but will have enough stored
battery power to leave its science instruments on during the eclipse.
As usual, suitably celebratory activities and attire (e.g., Aloha shirts,
bow ties, etc.) are encouraged in honor of the full Moon.
As to other celestial events between now and the next full Moon:
At the end of May/early June, in the northern hemisphere, the evenings start
with Saturn in the southern sky and Mars high in the southwest. In the
mornings, no naked eye planets are visible. Just before the full Moon after
next in early July, in the evenings, Saturn will appear to have shifted more
towards the west, closer to Mars, which will also have shifted closer to the
horizon. In the mornings, bright Venus will begin to emerge from the glow
of the Sun, having passed in front of the Sun on June 5th. Later in June,
if you observe Venus with a telescope or good binoculars, you will be able
to see that it appears as a crescent planet.
On Thursday evening, May 31, Saturn, Spica, and the Moon will appear lined
up. Once twilight has darkened to night, the waxing gibbous Moon will
appear about 3 degrees below the bright star Spica, with the bright planet
Saturn appearing about 5 degrees above Spica.
On Sunday, June 3, 2012, the nearly full Moon will appear near the bright
red star Antares (so named because it is similar in color and appearance to
the planet Mars, whose Greek name is Ares).
On Tuesday, June 5, 2012, the day after the full Moon and the partial
eclipse of the Moon, we will experience a rare and special event, a transit
of Venus, when the planet will appear to move in front of the Sun and block
a small amount of the Sun’s light.
The transit will begin at about 6:10 pm EDT. The transit will continue
until 12:45 am EDT on Wednesday morning, but we in the Washington DC area
will no longer be able to see it directly after Venus and the Sun set at
about 8:30 pm EDT (although many sites are planning to stream live video
throughout the transit).
Four Transits of Venus occur every 243 years. Two transits occur separated
by 8 years, then there is a 121 1/2 year wait for two more transits also
separated by 8 years, followed by another 105 1/2 years. This is the last
transit of Venus in our lifetimes, as the next one will be in December 11,
Prior to the development of planetary radar (measuring the time it takes for
radio ways to bounce off a planet and return to the Earth), planetary lidar
(doing the same think with laser beams) and space probes (actually tracking
spacecraft as they fly by, orbit, or land on other planetary bodies),
precisely observing transits of Venus from different parts of the Earth was
the best and most accurate way to measure the Earth’s distance from the Sun
and provide an absolute scale for the size of the solar system. The transit
of 1639 was observed by Jeremiah Horrocks who used his measurements to
estimate the size of Venus and the distance from the Earth to the Sun. In
the late 1600′s Edmund Halley proposed a world-wide effort for the next two
opportunities, in 1761 and 1769 (well after Halley’s death). As part of
this international scientific effort, Captain James Cook recorded the 1769
transit of Venus from the island of Tahiti during his first voyage around
the world. Improved observing technology allowed even more accurate
measurements for the 1874 and 1882 transits, further improving our
understanding of the size of the solar system. Now that we have better ways
of measuring interplanetary distances, scientific interest in observing
transits has shifted to comparing what we know about the Sun and Venus to
what we might be able to learn about other stars and their planets when we
observe transits of planets in solar systems beyond our own.
Be careful not to look at the Sun without a proper solar filter that you are
sure works! If you have approved solar shades (for viewing solar eclipses,
etc., do not try anything fancy like combining them with binoculars
(anything that focuses the sunlight could overcome the protection solar
shades provide). Only use binoculars or a telescope if you have an approved
solar filter designed to work with your optical system.
Because the orbit of the Earth around the Sun is not quite round, the
earliest sunrises occur before the Solstice while the latest sunsets occur
after the Solstice. For NASA Headquarters and the Washington, DC area,
rounded off to the minute, the earliest time of sunrise is 5:42 am from
Monday, June 11, 2012 to Friday, June 15, 2012.
On Sunday, June 17, 2012, about an hour before dawn (about 4:45 am in the
Washington, DC area), the waning crescent Moon will appear near the planet
Jupiter, low on the north-northeastern horizon. Jupiter will be just
beginning to become visible again, after having been lost from sight in the
glow of the Sun as it passed on the far side of its orbit as seen from the
By Monday, June 18, 2012, the waning crescent Moon will have shifted even
closer to sunrise, making it hard to see, but if you can find it, you should
be able to see a line-up of Jupiter, Venus, and the Moon, with the Moon
closest to the horizon.
Wednesday, June 20, 2012, at 7:08 or 7:09 pm EDT (apparently depending upon
how you round of the calculations), is the Summer Solstice, making this the
longest period of daylight of the year.
For NASA Headquarters and the Washington, DC area, rounded off to the
minute, the latest time of sunset is 8:37 pm from Wednesday, June 20, 2012
to Wednesday, July 4, 2012.
In the evening on Monday, June 25, 2012, the waxing crescent Moon will
appear near Mars in the southwestern sky.
By Tuesday, June 26, 2012, the first quarter Moon will have shifter to be
about halfway between Mars and Saturn.
By Wednesday, June 27, 2012, the waxing gibbous Moon will have shifted to
form a triangle with Saturn and the bright star Spica.
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 near by.
The full Moon after next is on Tuesday, July 3, 2012.