Archive for June, 2015

The Sky This Week, June 23 – 30, 2015 !

The Sky This Week, 2015 June 23 – 30

Follow the waxing Moon.
Lunar crater Copernicus, imaged 2015 SEP 15

The Moon waxes in the evening sky this week, diving toward the southern reaches of the ecliptic as she brightens the midsummer night sky. Full Moon occurs on July 1st at 10:20 pm Eastern Daylight Time. This is the first of two Full Moons for the month; the next falls on the 31st. This Full Moon is popularly known as the Hay Moon, Buck Moon, or Thunder Moon. The latter seems particularly appropriate this year! Luna may be found just northwest of the first-magnitude star Spica on the evening of the 25th. On the 27th she is just two degrees northeast of the tongue-twisting second-magnitude star Zubenelgenubi. On the 28th look for Luna just a degree north of yellow-hued Saturn.

This is another week when the Moon dominates the night sky view. The summer Milky Way is washed out by Luna’s glow which is further scattered by the persistent haze of Washington’s famed heat and humidity. However, it is often this bank of stagnant air that provides us with some of our crispest views of our nearest neighbor in space. Air often forms an “inversion” over urban areas during hot muggy days, and the lack of currents in this layer often allows telescopes to perform at their peak resolving power. As the Moon waxes through her gibbous phases, a wide variety of landscapes present themselves for your enjoyment. During much of the week the terminator line creeps slowly across one of the largest impact features on Luna’s face, the Mare Imbrium, or Sea of Rains. This huge feature, some 1100 kilometers (700 miles) across, is one of the largest impact craters in the solar system. It was formed by the impact is a large asteroid about 3.9 billion years ago, and its floor was subsequently flooded by lava erupted from the Moon’s interior. It can be seen with the naked eye as the left-hand “eye” of the “Man in the Moon”. It has many interesting features, the most notable being the so called “wrinkle ridges”, where molten lava solidified into a sort of frozen wave. Its floor is littered with smaller impact craters. Just to the south of Imbrium is a prominent impact crater that’s best seen on the evenings of the 25th and 26th. This is the crater Copernicus, a 93 kilometer (56 mile) diameter feature that’s much younger than the Imbrium basin, excavated by a smaller asteroid about a billion years ago. As such it is one of the youngest geological formations on the Moon. Had it been funded, the proposed Apollo 20 mission would have landed on its floor!

The early evening hours hold the most interesting phenomenon for the week as the dazzling planet Venus catches up to and passes Jupiter. On the evening of the 30th the duo will be less than 1/3 of a degree apart for one of the closest planetary appulses of the year. Venus will sail a few degrees ahead of Jupiter over the next several weeks, but they will stay well within five degrees of each other through mid-July.

Jupiter now sets just after the end of evening twilight, but you still have a chance to get a glimpse of him as the sky darkens after sunset. You should still be able to view his four bright moons as twilight deepens, but you’ll need exceptionally steady air to see much detail on his distant cloud tops.

Saturn is hitting his stride as evening twilight ends, crossing the meridian after 10:30 pm. At his best he’s only 33 degrees above the southern horizon, so a sultry still night may give you your best view. From my yard he has to dodge trees for me to get a good view of him, but whenever I do catch a glimpse of him I still marvel at the sight he presents in the eyepiece.


The Sky This Week – June 16 – 23, 2015 !

The Sky This Week, 2015 June 16 – 23

Come see the stars on the National Mall!
Jupiter, Europa, and Io, 2015 June 12, 01:12.5 UT

The Moon returns to the evening sky this week, passing the converging planets Venus and Jupiter in the early evening hours of the 19th and 20th. First Quarter occurs on the 24th 7:03 am Eastern Daylight Time. As Luna passes Venus and Jupiter, try your hand at a little basic astrophotography. Any good digital camera or smart phone should be able to record the Moon in the company of the two planets. If you’re lucky you may be able to frame them in the glowing red of a summer sunset.

The summer solstice occurs on the 21st at 12:38 pm EDT. At that time the center of the Sun’s disc will stand directly over the Tropic of Cancer at a spot about 400 kilometers north of the Dominican Republic. It also marks the longest day of the year for northern hemisphere residents. Here in Washington we’ll experience 14 hours and 54 minutes between sunrise and sunset. If we include the times of twilight, the sky is only fully dark for just over 5 hours.

Despite the dearth of darkness, the evening of June 19 will find telescopes set up for public viewing in the field to the northeast of the Washington Monument for the 6th annual Astronomy Night on the National Mall. Weather permitting we’ll have dozens of telescopes set up between 6:00 and 11:00 pm EDT observing the Sun, Moon, Venus, Jupiter, and Saturn. Last year’s event attracted some 7000 visitors, and everyone got a chance to see celestial showpieces, many for the first time. Despite the lights of downtown DC, we’ll have plenty of interesting things to look at. Representatives from NASA as well as a number of astronomy-oriented organizations will be on hand with the latest news on space probes and space research. In the event of rain the event will be held Saturday at Catholic University.

The evening thunderstorms of late have served to temporarily clear the nighttime sky during the late evening hours, and I have had a number of nice views of the rising stars of the Summer Triangle. Each of the three stars in this asterism leads a separate constellation which can be traced out from the suburban sky, while dark-sky viewers can see the fluffy star-clouds of the Milky Way running through the Triangle’s center. The highest and brightest of the Triangle stars is Vega, lead star in the diminutive constellation of Lyra the Harp. The body of the harp is a small parallelogram of third- and fourth-magnitude stars that should be easily sighted in binoculars. Just to the east of Vega your binoculars will reveal a pair of stars in close proximity to each other. This attractive pair offers a further surprise when you examine them with a small telescope: each of the component stars is itself a close double star, making the entire system a “quadruple” star system. Cataloged as Epsilon Lyrae, it is popularly known to amateur astronomers as the “Double-double”. If you now direct your telescope to the space between the bottom two stars in the parallelogram, you should see a ring of ghostly light resembling a tiny smoke ring. This is Messier 57, also known as the Ring Nebula, one of the best examples of a star’s slow death available for amateur astronomers to observe.

Venus and Jupiter continue to draw closer to each other, with the brighter Venus halving the apparent gap between the two worlds. By week’s end Venus and Jupiter are just four degrees apart, and that gap will continue to close until a spectacular conjunction occurs between them by the end of the month.

We should still get a decent view of Jupiter at the star party on the Mall, and the giant planet will oblige by presenting a transit of its moon Io and Io’s shadow across the planet’s face during the course of the evening. Nearby Venus will exhibit a waning crescent phase just a telescopic nudge away.

Saturn will feature prominently at the star party, and I anticipate many “oohs” and “aahs” from people who will get their first glimpse from the Mall. Saturn is simply un-Earthly; nothing else in the solar system of the deep-sky quite compares to it. While we now understand the rings’ composition and dynamics, they are still a sight that defies logical explanation. Come on down on Friday night ad get a look for yourself.

The Sky This Week, June 9 – 16, 2015 !

The Sky This Week, 2015 June 9 – 16

Our shortest nights are upon us.
The summer Milky Way from Cassiopeia to Sagittarius
imaged from Morattico, Virginia

The Moon wanes through her crescent phases in the pre-dawn hours this week, passing through autumn’s sparse star-fields as she skirts the southeastern horizon. New Moon occurs on the 16th at 10:05 am Eastern Daylight Time. Luna has very few bright companions to call on this week, the exception being a one-degree encounter with a fourth-magnitude star with the tongue-twisting name of Torcularis Septentrionalis, the name bestowed on the star Omicron Piscium in a 1515 edition of Ptolemy’s “Almagest”.

By the end of the week we begin to enter the two-week series of events tied to the Summer Solstice. Due to the small but measurable eccentricity of the earth’s orbit the dates of earliest sunrise and latest sunset occur about a week before and a week after the solstice respectively. Here in the Washington, DC area Old Sol will rise at his earliest time for the year, 5:42 am EDT, on the morning of the 14th. By the time we see our latest sunset on the 28th sunrise will be about three minutes earlier.

The nights around the summer solstice are the shortest we’ll experience for the year, just over five hours long between the end of evening twilight and the beginning of morning twilight. This leaves us with little time to enjoy the sights of a moonless dark sky, but if you’re up late in the evening you can help chart the brightness of your local sky by participating in the citizen-science “Globe at Night” program. This month’s campaign uses the stars of the constellation Boötes, the Herdsman. While the ancients would like you to imagine the figure of a man leaning on a staff holding two dogs on leashes herding Ursa Major (the Great Bear) around the pole, I find it far easier to imagine an ice-cream cone with the bright star Arcturus marking the cone’s pointed tip. Most of the constellation’s other stars are much fainter second- and third-magnitude stars. From my suburban lawn I can spot only three other stars besides Arcturus, but in darker skies you should be able to pick out up to a dozen more.

By midnight the sky begins to undergo a significant change. Rising in the east are the bright stars associated with the midsummer sky, dominated by the trio of first-magnitude stars known as the Summer Triangle, Vega, Deneb, and Altair. Running from north to south through the triangle are the bright star clouds of the Milky Way, which reach down to the southern horizon to the east of the bright reddish star Antares, brightest star in the constellation of Scorpius, the Scorpion. These star clouds will be wonderful targets for binoculars and small telescopes as the summer progresses. Chock full of star clusters and glowing nebulae, these areas of the sky offer a welcome sight after evenings spent hunting down faint galaxies in the dark spaces between the spring’s few bright stars.

Bright Venus closes to within 10 degrees of slightly dimmer Jupiter during the course of the week. The two planets will converge over the course of the next few weeks, then spend a week less than a degree apart from each other after a spectacular close conjunction on June 30th.

Jupiter is becoming increasingly difficult to observe in a telescope as he steadily loses ground to the advancing Sun. Strong summer sun heats up rooftops and tree canopies which then radiate that heat back into the sky after sunset. By the time the air stabilizes Old Jove is not very far from the western horizon. You can still track the comings and goings of his four bright moons, but searching for fine detail in his cloud tops is now a very difficult task.

Saturn crosses the meridian at midnight, so the hours between twilights are the best times to view him. Despite his southerly declination the ringed planet shows off his signature rings to owners of small telescopes. They are tilted about 25 degrees to our line of sight, giving the planet a unique aspect among all of the sights in the night sky.

The Sky This Week, June 2 – 9, 2015 !

The Sky This Week, 2015 June 2 – 9

Markarian’s Chain, the heart of the Coma-Virgo Galaxy Cluster
Messier 86 and 84 are the two prominent galaxies at center-right
Imaged from Morattico, Virginia on 2013 April 14.

The Moon wanes from the full phase this week, skirting the southern horizon as she moves into the barren star-scapes of the autumnal sky. Last Quarter occurs on the 9th at 3:42 pm Eastern Daylight Time. Luna stands squarely over the top of the “Teapot” asterism of Sagittarius in the early morning hours of the 4th. After that she finds few bright companions to meet for the rest of the week.

As the Moon slips into the morning sky we begin to get a few precious hours of dark-sky time, but we have to wait up awhile to enjoy them. June is the moth of the solstice, and full astronomical darkness now doesn’t occur until around 10:30 pm! At this hour the bright rose-tinted star Arcturus may be found near the meridian high in the sky. About halfway between Arcturus and the southern horizon is another bright star, Spica, brightest star in the constellation Virgo. Just to the west of these stars is the region known to thousands of amateur astronomers as the “Realm of the Nebulae”, the heart of the Virgo Galaxy Cluster. From a good dark sky location you can spot several of the cluster’s brightest galaxies as small fuzzy blobs of light in a steadily-held pair of binoculars. A three-inch aperture telescope will reveal a few dozen of these distant star systems, while a six-inch can show hundreds more. One of the most amazing sights I’ve seen in the sky is the view of the central part of the cluster through my 14.5-inch reflecting telescope, with the ghostly glow of a dozen galaxies gently wafting through the field of a wide-angle eyepiece. Each of these galaxies is shining with the light of a hundred billion suns whose light has taken over 50 million years to traverse the gulf of space to arrive at my eye. Stepping back from the eyepiece and gazing eastward we now see the rising star-clouds of the summertime Milky Way, which is itself a far-flung outlier of those distant wisps of light that I’ve just been looking at. Yes, the universe is a very big place!

One of those stars in the Milky Way galaxy is our Sun, and whirling around it are a number of objects that attract our attention in the night sky. Two of the brightest of these are now best seen in the fading twilight of the mid-evening, dominating the western sky. The brightest of these is Venus, often referred to as Earth’s “sister planet”. Physically Venus is just a bit smaller than our fair world, but her surface is perpetually hidden under a global deck of bright clouds that cause her to shine with dazzling brilliance. Under those clouds lies a surface that is truly hellish to imagine, with a global surface temperature hot enough to melt lead and a crushing atmosphere which belies her pleasing appearance in our skies. Venus is now appearing to close in on the planet Jupiter, and by the end of the month she will be quite close to the giant planet in the sky. This closeness is really an optical illusion; Jupiter never gets closer than a few hundred million miles to the dazzling planet!

Jupiter is now best placed for viewing shortly after sunset and remains high enough in the sky for telescopic viewing as evening twilight fades. Despite a brighter sky background, the planet still offers a wonderful sight in the telescope. His four large Moons offer constantly shifting configurations from night to night, and the alternating dark belts and bright zones are a testament to the violent forces at work in the planet’s huge atmosphere. If you observe him at around 9:00 pm on the 6th you’ll see the famous Great Red Spot crossing the center of the planet’s disc as well as a nice view of all four of the planet’s moons.

Saturn is easily seen in the southeastern sky by the end of evening twilight. His yellow glow contrasts nicely with the surrounding blue-tinted stars in the head of Scorpius. Viewing Saturn in a telescope invariably elicits surprise from those who’ve never seen it before, and even seasoned observers take a few moments to ponder the planet’s rings. Saturn will be with us in the evening sky for most of the summer, so you’ll have plenty of chances to get a nice view.