Quarter Moon Archive
    April 22, 2016
  • As the moon moves around Earth in its monthly orbit, there are four points at which it is in exact geometry with the sun and Earth: new moon, first quarter, full moon, and last quarter.

    These are the four points at which the Earth, moon and sun are in a straight line, or the sun and moon form a 90-degree angle as seen from Earth.

    At new moon, the moon is between Earth and sun, so we are trying to see the moon's dark side in front of the brilliant sun. We can never see the moon at new moon because of the bright sunlight, except on the rare instances when the moon is directly in front of the sun and we get a solar eclipse. Because of the tilt of the moon's orbit, most of the time it passes either above or below the sun, but still close enough that it is lost in the sun's glare. [Moon Photography Tips from Astrophotographers: A Visual Guide]

    At full moon, Earth is between sun and moon, so the moon is exactly opposite the sun in Earth's sky. The moon rises just as the sun sets, and sets just as the sun rises. The side of the moon we see is fully illuminated, except on the rare occasions when the shadow of Earth falls on the moon: a lunar eclipse. Once again, the tilt ofthe moon's orbit makes it usually pass above or below the Earth's shadow.

    The quarter moon phases, first and last, fall exactly in between new and full moon, when the moon is a quarter or three quarters of the way around Earth. These are the best times to observe the surface of the moon, because the sun is just rising or setting along the terminator, the dividing line between bright and dark sides of the moon. The moon's surface features are shown in stark relief by the rising or setting sun.

    The average skywatcher is much more familiar with the appearance of the first quarter moon than the last quarter moon. That's because first quarter always occurs when the moon is in the evening sky, when most of us do our observing. The last quarter moon is much more rarely seen because it is mainly visible in the wee hours of the morning.

    Because the moon takes 29 and a half days to go through its cycle of phases, sometimes we can get the same phase twice in a calendar month, usually 30 or 31 days. This is most noticeable with the full moon, and some people have named the second full moon in a month a "blue moon."

    Last month, in February with only 29 days, many parts of the world missed out on having any last quarter moon. This month we make up for it by having two last quarter moons. The first was on Tuesday, March 1, at 6:11 p.m. EST. The second occurred on Thursday, March 31, at 11:17 a.m. EDT.

    If a second full moon in a month is called a "blue moon," perhaps a second last quarter moon in a month could be called a "blue last quarter." [Amazing Blue Moon Photos by Lunar Fans]

    Like any "blue moon" this "blue last quarter" won't look any different from a regular last quarter, and certainly won't be blue in color. It is simply an accident of our calendar.

    The best time to observe a last quarter moon is around sunrise, before the sky becomes fully light. Look for the moon close low in the southern sky at sunrise (in the northern hemisphere).

    If you look at the last quarter moon with a telescope, you will be surprised at how different some of the familiar features look with the sunlight coming from the opposite direction. Most striking is the famous scarp known as the Straight Wall, a bit south of the center of the moon's disk. At first quarter it appears as a dark line, with the sun rising to its east. At last quarter, its westward facing face is fully lit by the setting sun, and appears as a bright white line.

    Try capturing this rare event in a photograph, something seen only "once in a blue last quarter moon." Even a cell-phone camera is capable of making good pictures of the moon through a telescope.

    April 22, 2016
  • (Reuters) - American Airlines Group Inc (AAL.O) on Friday dashed Wall Street's hope that it could turn around a key revenue measure this year, plunging shares of the world's largest airline by 5 percent.

    American said it sees more turbulence ahead from a surge in rivals' flights across the Atlantic and from lower prices on trips booked at the last minute.

    A closely watched measure - passenger revenue divided by American's plane seats and mileage - is expected to fall between 6 percent and 8 percent in the second quarter, the airline said.

    Moves to stop the measure's months-long decline would not have a major impact until 2017, American President Scott Kirby said on an analyst call.

    The company has lowered its international growth plans to boost unit revenue and later this year will start selling cheap fares with more restrictions to battle U.S. budget carriers.

    "Unilaterally reducing capacity wouldn't get us (passenger unit revenue) positive on its own," Kirby said, noting that American is implementing a new demand forecasting system and tweaking its pricing strategy, among other actions.

    Not every initiative has improved results.

    For about three months this year, American and other carriers stopped selling special connecting fares that undercut prices on rivals' nonstop flights, according to Kirby. That began to hurt revenue so airlines have added the fares back into the market.

    JPMorgan analyst Jamie Baker called the revenue forecast disappointing in a research note. American forecast a pre-tax profit margin between 14 percent and 16 percent for the second quarter, whereas investors were looking for guidance closer to 16 percent, Baker said.

    Rivals' shares fell after the news, as investors cast doubts about a stronger forecast last week from Delta Air Lines Inc (DAL.N), which said unit revenue would stop falling this year. Delta fell 1 percent in morning trade, while United Continental Holdings Inc (UAL.N) fell 3 percent.

    The forecast also overshadowed American's announcement to buy back another $2 billion of its shares by the end of 2017. American said its share count dropped nearly a quarter since the end of 2013, raising the value of investors' stakes.

    The airline said income fell about 25 percent to $700 million in the first quarter from a year ago, in part because it recorded additional non-cash taxes. Excluding special items, it earned $1.25 per share, above analysts' average estimate of $1.19 per share, according to Thomson Reuters I/B/E/S.

    (Reporting by Jeffrey Dastin in New York; Editing by Bernadette Baum and Bill Trott)

    April 22, 2016
  • As you gaze at the first-quarter moon this week, you may wonder when the last-quarter moon will occur this month. But there won't be one, if you live in North or South America.

    Take the situation in eastern North America, which is in the Eastern Standard Time (EST) zone. The previous last-quarter moon was on Jan. 31 at 10:28 p.m. EST, and the next one will be on March 1 at 6:11 p.m.

    The mathematics behind this is that the average synodic lunar month — from new moon to new moon — is 29.53 days long, while February is either 28 or 29 days long. So it is possible, even in a leap year like 2016, to have one of the four main lunar phases fall outside the calendar month of February. [Earth's Moon Phases, Monthly Lunar Cycles (Infographic)]

    Other parts of the world, such as Europe, had a last-quarter moon this month early on the morning of Feb. 1.

    We make a big fuss about the "Blue Moon," when there are two full moons in a month, but we don’t seem to notice when one of the lunar phases goes missing.

    This raises the question of why our months vary so much in their number of days: 28 or 29 in February, 30 in April, June, September and November, and 31 in the other seven months. The problem is that the sun, moon and Earth don’t move to the tune of simple arithmetic.

    The lunar month consists of 29.530589 days, and the tropical year (equinox to equinox) is 365.242190 days long. When the ancient astronomers attempted to construct a calendar with these bizarre numbers, they found that, literally, it did not compute.

    Early astronomers divided the shape of a circle into 360 degrees. This seems like a strange number to us with our decimal system, but it made sense with a number system based on 12. It also came close to the number of days in a year, though not close enough. The year was divided into 12 months (a natural in a base-12 number system) of 30 days each — but that left the awkward 5-and-a-bit-days remaining.

    Mathematicians struggled with this problem for thousands of years, until finally a papal commission in 1582 came up with a complex but elegant solution, known as the Gregorian calendar, after Pope Gregory XIII, who commissioned it.

    In order to get the church’s feast days back in phase with the astronomical calendar, it was necessary to omit 11 days.

    May 04, 2016
  • A stellar eclipse will be visible from nearly everywhere in the United States and much of southern Canada this Sunday (April 10). Even skywatchers in Hawaii will be able to see the eclipse, although it will not be visible from Alaska.

    The waxing crescent moon, 15 percent illuminated by the sun, will pass in front of the star that marks the angry orange eye of the constellation Taurus,

    That star is Aldebaran, the 13th brightest star in the sky and certainly one of the more colorful ones. This eclipse is known to astronomers as  As the moon orbits the Earth, it appears, from our perspective, to move slowly toward the east relative to the stars, at roughly its own diameter per hour. A waxing moon always leads with its dark edge as it moves along its orbit against the starry background.

    May 04, 2016
  • The colossal impact that created the moon may have spawned the cosmic mashup between the rocks that ultimately became Earth and its lunar neighbor, researchers say.

    Previous research suggested that about 100 million years after the solar system formed 4.6 billion years ago, the newborn  named after the mother of the moon in Greek myth. Debris from the collision later coalesced into the moon.

    Much remains uncertain about the precise nature of this giant impact. For instance, scientists have long debated how much debris, including water, was exchanged between the nascent Earth and moon, and whether the collision was a glancing blow or a high-energy impact.

    May 04, 2016
  • The researchers analyzed seven  collected during the Apollo 12, 15 and 17 lunar missions. They also examined one lunar meteorite — a rock that a cosmic impact knocked off the moon, which later crashed on Earth.

    The researchers focused on ratios between different isotopes of oxygen in the rocks. Isotopes of an element have differing numbers of neutrons from one another — for instance, oxygen-16 has eight neutrons in its nucleus, while oxygen-17 has nine. [Violent Birth of the Moon Explained (Infographic)]

    The ratio of oxygen-17 to other oxygen isotopes typically gets smaller the bigger planets and moons get. This means that different planets and moons usually have distinct isotope signatures.

    However, the researchers found that Earth and the moon have indistinguishable oxygen isotope ratios, within 5 parts per million when it comes to oxygen-17.

    "As we continue to improve our ability to make measurements, the moon and Earth continue to be more and more alike isotopically," Young told Space.com.

    October 24, 2016
  • A first quarter moon shows half of its lighted hemisphere – half of its day side – to Earth.

    The moon reaches first quarter on October 9, 2016 at 0433 UTC; translate to your timezone. The full moon will come on the nights of October 15-16. It will be the Hunter’s Moon and also a supermoon.

    We call this moon a quarter and not a half because it is one quarter of the way around in its orbit of Earth, as measured from one new moon to the next.

    Also, although the moon appears half-lit to us, it’s good to recall that the illuminated portion of a first quarter moon truly is just a quarter. On the night of first quarter moon, we see half the moon’s day side, or a true quarter of the moon. Another lighted quarter of the moon shines just as brightly in the direction opposite Earth!

    And what about the term half moon? That’s a beloved term, but not an official one.

    A first quarter moon rises at noon and is highest in the sky at sunset. It sets around midnight. First quarter moon comes a week after new moon. Now, as seen from above, the moon in its orbit around Earth is at right angles to a line between the Earth and sun.