The Sky This Week, 2010 December 14 – 21 — Naval Oceanography Portal

The 21st also marks the beginning of the astronomical season of winter, with the Winter Solstice occurring at 6:38 pm on the 21st. This is the moment when the Sun reaches its southernmost declination in the sky and we experience the year’s shortest day in the Northern Hemisphere. At this time the Sun stands directly over the Tropic of Capricorn over the remote islands of Kiribati in the South Pacific Ocean. Gradually over the next few days, then more rapidly as the new year begins, Old Sol will climb back toward more northern climes. Spring is surely on the way!

The Sky This Week, 2010 December 14 – 21 — Naval Oceanography Portal

Watch out for the Super Harvest Moon – NASA Science

Sept. 22, 2010:  For the first time in almost 20 years, northern autumn is beginning on the night of a full Moon. The coincidence sets the stage for a "Super Harvest Moon" and a must-see sky show to mark the change of seasons.

The action begins at sunset on Sept 22nd, the last day of northern summer. As the sun sinks in the west, bringing the season to a close, the full Harvest Moon will rise in the east, heralding the start of fall. The two sources of light will mix together to create a kind of 360-degree, summer-autumn twilight glow that is only seen on rare occasions. …

Northern summer changes to fall on Sept. 22nd at 11:09 pm EDT. At that precise moment, called the autumnal equinox, the Harvest Moon can be found soaring high overhead with the planet Jupiter right beside it. The two brightest objects in the night sky will be in spectacular conjunction to mark the change in seasons. …

Usually, the Harvest Moon arrives a few days to weeks before or after the beginning of fall. It’s close, but not a perfect match. The Harvest Moon of 2010, however, reaches maximum illumination a mere six hours after the equinox. This has led some astronomers to call it the "Harvestest Moon" or a "Super Harvest Moon." There hasn’t been a comparable coincidence since Sept 23, 1991, when the difference was about 10 hours, and it won’t happen again until the year 2029.

A Super Harvest Moon, a rare twilight glow, a midnight conjunction—rarely does autumn begin with such celestial fanfare.

Enjoy the show!

Watch out for the Super Harvest Moon – NASA Science

The Sky This Week, 2010 September 21 – 28 — Naval Oceanography Portal

This year’s Harvest Moon takes place within hours of the autumnal equinox, which falls on the 22nd at 11:09 pm EDT. At that instant the center of the Sun’s disc will be located directly over the Equator just west of Papua New Guinea, passing from the northern hemisphere of the sky into the southern hemisphere. Since the Sun subtends a tangible disc, though, the actual time when we see exactly 12 hours between sunrise and sunset won’t occur until a few days after the equinox. Here in Washington that phenomenon occurs on the 26th. This is also the time of year when the change in length of daylight occurs at its most rapid rate. There is no mistaking that the days are getting shorter!

The Sky This Week, 2010 September 21 – 28 — Naval Oceanography Portal

Closest Encounter with Jupiter until 2022 – NASA Science

Been outside at midnight lately? There’s something you really need to see. Jupiter is approaching Earth for the closest encounter between the two planets in more than a decade–and it is dazzling.

The night of closest approach is Sept. 20-21st. This is also called "the night of opposition" because Jupiter will be opposite the sun, rising at sunset and soaring overhead at midnight. Among all denizens of the midnight sky, only the Moon itself will be brighter.

Earth-Jupiter encounters happen every 13 months when the Earth laps Jupiter in their race around the sun. But because Earth and Jupiter do not orbit the sun in perfect circles, they are not always the same distance apart when Earth passes by. On Sept. 20th, Jupiter will be as much as 75 million km closer than previous encounters and will not be this close again until 2022.

Closest Encounter with Jupiter until 2022 – NASA Science

The Sky This Week, 2010 September 14 -21 — Naval Oceanography Portal

In celebration of our closest neighbor in space, the evening of the 18th has been designated as the first annual International Observe the Moon Night (InOMN). … Information on InOMN, including charts depicting Luna’s appearance on the 18th, may be found on the official website.

The Sky This Week, 2010 September 14 -21 — Naval Oceanography Portal

The Sky This Week, 2010 July 27 – August 3 — Naval Oceanography Portal

As you wait for the sky to darken in the hours after sunset, keep an eye on the southwestern sky, where three planets are participating in one of the best series of conjunctions for the year.  The objects in question are Venus, Mars, and Saturn, and they will spend the next couple of weeks playing a celestial version of “leapfrog” during the twilight hours.  As the week opens, both Venus and Mars lie to the west of Saturn.  By the end of July Mars overtakes and passes the more distant ringed planet, with closest approach between the duo falling on the evening of the 31st.  In the meantime, dazzling Venus is chasing down both objects, and by the end of the week you’ll see an attractive triangle in the southwest with Mars and Venus forming the base and Saturn the apex.  Looking ahead to August, Venus blows by Saturn on the 7th, then passes Mars on the 18th.   

All of this activity in the early evening sky sets the stage for the entrance of Jupiter, who rises just as Saturn and his companions set.  By the end of the week you should see Old Jove in the east at around 11:00 pm, and by midnight he should be high enough to train the telescope in his direction.  Jupiter will become an easier target as August passes, rising about four minutes earlier each night.  He’s still missing his prominent South Equatorial Belt of dark clouds, but this in turn helps to accentuate the famous Great Red Spot, which is the planet’s most famous feature.

The Sky This Week, 2010 July 27 – August 3 — Naval Oceanography Portal

The Sky This Week, 2010 July 20 – 27 — Naval Oceanography Portal

The late twilight of the evening sky finds the beginnings of a planetary “traffic jam” in the southwest.  Venus will be the most obvious planet as the light of early evening fades, and she is steadily closing in on ruddy Mars and gold-hued Saturn.  I happened to view Venus shortly before she set last weekend from down on the Northern Neck of Virginia.  Thanks to a flat horizon, thin clouds, and haze, the normally dazzling white planet was glowing like a single orange-red coal in a dying campfire.  She spends the week in restless pursuit of Mars and Saturn, which are gearing up for their own conjunction next week. 

The late night sky now welcomes the bright glow of Jupiter, who is doggedly rising about four minutes earlier each night.  Old Jove reaches the first stationary point in the current apparition on the night of the 23rd, pausing for a few days in his eastward motion before seeming to back up toward the west over the course of the next four months.  Late night skywatchers are now enjoying the view of the giant planet in their telescopes.  Soon he’ll be delighting even those of us with early bedtimes.

The Sky This Week, 2010 July 20 – 27 — Naval Oceanography Portal

The Sky This Week, 2010 June 15 – 22 — Naval Oceanography Portal 

The summer solstice occurs on June 21st at 7:28 am EDT.  At this moment the center of the Sun’s disc stands directly overhead at a point on the Tropic of Cancer in the southeastern corner of Algeria.  A few hours earlier Old Sol stood virtually overhead in the Egyptian city of Aswan, known to the Greek astronomer Eratosthenes in about 240 BCE as Syene.  Eratosthenes also knew that on the summer solstice in Alexandria, Egypt the Sun was just over seven degrees from the zenith.  Having traveled by camel from Syene to Alexandria, he estimated the distance between the two cities and used geometry to estimate the circumference of the Earth.  His result was remarkably close to our modern value if we make certain assumptions about the units that he used.  Still, his method proved that the Earth was indeed a sphere of finite dimension.  For most of us, the solstice passes more or less unnoticed except as the marker of the longest day of the year.  However, many ancient cultures revered the day, as evidenced by Neolithic and Paleoamerican sites throughout the world.

The Sky This Week, 2010 June 15 – 22 — Naval Oceanography Portal

Happy Solstice to all!