Skywatch Line for Friday, September 4, through Sunday, September 6

This is Dudley Observatory’s Skywatch Line for Friday, September 4, through Sunday, September 6, written by Alan French.

The Moon reaches last quarter Saturday morning, so moonrise over the weekend is late, leaving the evening skies nice and dark. Moonrise is at 11:41 Friday night, 12:30 am Sunday, and 1:22 am Monday.

If you look high overhead at 9:00 pm you’ll see the bright star, Vega, luminary of Lyra, the lyre. Like the majority of the brighter stars in the night sky, Vega is bright because it is one of our nearer stellar neighbors. It is 25 light away and ranks as the fifth brightest star. The only brighter star in the sky at 9:00 pm now is Arcturus, the reddish star in the western sky, which on outshines Vega slightly,.

Lyra is one of the smaller constellations in the sky and its pattern of stars is easy to recognize. If you are facing south and looking high in the sky at Vega, look for a parallelogram of stars to Vega’s lower left. A fifth star to the upper left of Vega completes the pattern of the Lyre. The star to the upper left is quite famous – it is known as the double-double, and is actually four stars. If you have sharp eyes you might be able to see that there are really two stars there, close together. If you can’t see the two by eye, binoculars will nicely reveal them. A telescope and higher power reveals that each of the two is itself a double star, and they are a pretty sight. (If the air is unsteady, they can be hard to discern. Try another night.)

You have probably heard that there is a total eclipse of the Moon on Sunday, September 27, and we’ll be writing about it on that weekend’s Skywatch Line. You may also have heard it called a “Supermoon Eclipse.”

The Moon’s orbit is not quite circular, so its distance from the Earth varies. When it is closest to Earth it appears slightly larger than when it is farthest away. Sometimes the extremes occur close to full Moon, and in recent years the media has taken to sensationalizing the extremes, calling the slightly larger full Moon a “supermoon” and the smaller a “micromoon.”

Exactly how much difference is there between a supermoon and a micromoon? Fortunately, this is easy to show using photography, and has been done numerous times. You can see one example here. In such photographs the difference is quite obvious, but the photos do not reflect two realities of looking at the Moon in the night sky, so they can be misleading.

First, the Moon’s apparent size in the night sky is much smaller than it looks in the photo. To get some idea of how small the Moon actually looks, hold an aspirin at arm’s length. It would completely cover the Moon. When objects are so small it is harder to discern small differences in size. More importantly, we can never do direct comparisons – supermoons and micromoons can only be seen well separated in time.

Here’s an easy experiment you can do if you’re really curious. Draw two circles on a white sheet of paper. Make the first one inch in diameter and the other one and one-eighth inches in diameter. These represent the micromoon and the supermoon. Now place them 115 inches away from your eyes, a distance where they accurately represent the apparent sizes of the micro and supermoons. You should be able to tell which is larger, but it is not as obvious as it was with the larger photos. Now imagine that you look at one circle and then the other, separated in time by many months. (The next micro-full Moon is on April 22, 2016.) The “extremes” of the Moon’s size at full are perhaps not as newsworthy as they seem.

Skywatch Line for Wednesday, September 2nd and Thursday, September 3rd

This is the Dudley Observatory Skywatch Line for Wednesday, September 2nd and Thursday, September 3rd written by Louis Suarato

Wednesday evening, after sunset, Saturn emerges approximately 20 degrees over the southwestern horizon. Saturn sets 14 minutes before 11 p.m. Wednesday night. The time between sunset and the time Saturn sets decreases from 3 1/2 hours to 2 1/2 hours during September. You will require binoculars or a telescope to view Neptune and Uranus. Neptune can be found at the center of the constellation Aquarius above the southeastern horizon at around 10:30 p.m., and Uranus will be in Pisces above the eastern horizon. Just one day past opposition, Neptune shines at 6th magnitude, while Uranus is at 8th magnitude. A finder chart for the precise location of these two outermost planets can be found at SkyandTelescope.com. You will have about two hours of dark skies after sunset before the 75% illuminated, waning gibbous Moon rises in the east.

The early morning sky offers views of our two neighboring planets, Mars and Venus. Look low over the eastern horizon around 5 a.m. for both. Venus, shining at magnitude -4.02, is the easiest to spot. Venus’ rise will increase from 2 hours before sunset to about 3 1/2 hours before sunset by month’s end. Look about 8 degrees to the left of Venus for the red planet, Mars. Look 3 degrees above Venus for the open star cluster M67 in the constellation Cancer. M67, also known as NGC 2682, was discovered by Johann Gottfried Koehler in 1779. The estimated ages of the stars within this cluster range from 3.2 to 5 billion years, making this one of the oldest known open clusters. There are approximately 500 stars within M67 with over 100 stars similar to our Sun. Look about 8 degrees above Mars and M67 for M44, the Beehive Cluster.

Septembers local astronomy events include Night Sky Adventures @MiSci on September 15th at 7 pm. The program “Total Lunar Eclipse” will provide insight on what will occur during September 28th’s eclipse. On Friday, September 18th at 7 pm, the Dudley Observatory will hold an Octagonal Barn Lecture and Star Party in Delanson, NY. The topic of the lecture will be “A Scientific Sweatshop: The Industrialization of American Science and the Woman of Dudley Observatory. On September 17th at 7 pm, MiSci will be host to International Observe the Moon Night, an international event to encourage observation, appreciation and understanding of the Moon and planetary science.

Also in September, the Albany Area Amateur Astronomers will be hosting star parties at the Landis Arboretum in Esperance, NY on Friday, September 11th and 12th and on Friday, September 18th at Grafton Lake State Park.

Skywatch Line for Monday and Tuesday, August 31st and September 1st

This is the Dudley Observatory Skywatch Line for Monday and Tuesday, August 31st and September first written by Joe Slomka.

The Sun sets at 7:32 PM; night falls at 9:13. Dawn breaks at 4:39 AM and ends with sunrise at 6:19.

Two bright planets blaze in the darkening sky. Mercury lies low above the western horizon. At civil dusk, it is only three degrees high. An observer with an unobstructed view could see a bright ball; but he has to act quickly, Mercury sets at 8:21 PM.

Saturn, on the other hand, is easy to spot; it appears midway between Libra and the head of Scorpius – about twenty-three degrees high. Saturn dips lower daily; and, Earth’s atmosphere increasingly makes detecting details difficult. Its rings are still a wonder to behold, since they are still tilted to maximum. Saturn sets before 11 PM.

Neptune rises with sunset; it is at opposition tonight in Aquarius. We will discuss Neptune in another minute.

The seventeen-day-old Moon rises in Pisces at 8:43 PM on Monday evening and appears about seven degrees to the right of Uranus. A slimmer Moon rises about 10 PM on Tuesday night and appears seven degrees to Uranus’ left. Uranus rises about 9 PM both nights also in Pisces. The bright Moon’s proximity may hinder attempts to locate this giant planet. Finder aids to Neptune and Uranus can be found in astronomy magazines, websites and apps.

Dawn sees Mars and Venus rise in Cancer. Mars rises first at 4:15 AM. To early risers, it looks like a tiny red ball in their telescopes. Recently, planetary scientists announced that Mars once had salty water, just like Earth; but they could not say how acid was Martian water.

Venus follows Mars at 4:38 AM. At minus fourth magnitude, Venus is an easy guide to Mars, about eight degrees above. Venus sports a very thin crescent, about nine percent. Both planets should be observed as soon as possible to avoid the rising Sun’s glare.

As mentioned, Neptune is in “opposition,” which means it rises at sunset and sets at sunrise, and is ideally positioned for observation. Neptune can be seen in binoculars, but it takes a moderately large telescope and a detailed chart to identify it as a planet. Neptune is a gas giant planet. It is also a modern planet. Planet Uranus was discovered in 1781 (it is currently located in Pisces). Irregularities in Uranus’ orbit inspired a search for another planet. Newton’s laws of planetary motion suggested a place to search. Johann Galle and Heinrich D’Arrest discovered Neptune in the place suggested, Aquarius, in 1846. The discovery of Neptune was a triumph of Newton’s theory. Neptune takes over 163 years to orbit the Sun. Neptune is appropriately named. He is the Roman god of the Sea, and now reigns over the vest heavenly ocean. Neptune shines at magnitude 7.8 and appears a tiny 2.3 arc seconds in size. Neptune has two moons, Triton and Nereid. Triton is visible in medium size telescopes; it is the only large solar system moon that orbits its planet backwards, providing an interesting observation target.

Skywatch Line for Friday, August 28, through Sunday, August 30

This is Dudley Observatory’s Skywatch Line for Friday, August 28, through Sunday, August 30, written by Alan French.

The Moon reaches full late in the morning on Saturday, so the weekend’s sky will be dominated by a bright Moon. Amateur astronomers are not fond of the Moon around full. Its brightness washes out the faint deep sky objects (nebulae, galaxies, and star clusters) many enjoy. Even the brighter celestial showpieces are more muted. Lunar aficionados themselves are often not fans. Near full, shadows over most of the Moon are short or nonexistent, so detail does not stand out. Only near the limb are shadows long, and our view of features on the limb, far around the curve of the Moon, is not the best..

But such a Moon does offer some treats. The darker, lunar Maria really stand out from the bright lunar highlands. You can see many by eye alone, and binoculars provide a fine view. (It’s nice to learn your way around the Maria – they provide a good framework identifying other lunar features.) Also look for subtle variations of shading.

This is also a good time to see the “rays,” streaks of newer material that was ejected when a meteor hit the Moon and formed a crater. The rays go radially outward from some of the newer craters. The most prominent rays are seen around Tyco. Tyco is in the southern (bottom) part of the Moon, in the brighter highlands. Binoculars will nicely reveal its rays. The rays are visible because Tyco is a rather young crater, estimated to be just over 100 million years old, so the ejected material is fairly fresh and bright. It will fade and grow less prominent with age, but it is a slow process.

It’s always fun to catch the nearly full Moon rise, and it can be a nice subject for a photograph if you find a good foregound. It often is a lovely orange, adding to its visual and photographic impact. On Friday the Moon rises at 6:49 pm in the east southeast. Moonrise Saturday is at 7:29 pm a little south of due east, and by Sunday the Moon rises at 8:07 pm in the east.

To the eye the “Moon illusion” makes it look larger when close to the horizon.

The Moon illusion is not completely understood. One frequent claim is that the Moon looks larger near the horizon because there are objects there to compare it to, but the illusion also works along a featureless ocean or desert horizon.

The illusion is a largely due to a perceptional difference in looking upward versus looking straight ahead. Indeed the dome of the sky looks closer low down than overhead. Even constellations seem larger when near the horizon. When I spend a long night observing, and the time of year is right and the Big Dipper has a chance to move from high overhead to skimming the horizon, the difference in perceived size is striking.

Skywatch Line for Wednesday, August 26th and Thursday, August 27th

This is the Dudley Observatory Skywatch Line for Wednesday, August 26th and Thursday, August 27th written by Louis Suarato

On Wednesday, the 88% illuminated, waxing gibbous Moon rises at 5:06 p.m. between the constellations Capricornus and Sagittarius. Above and slightly east of the Moon, you’ll find the constellation Aquila with its brightest star Altair. Altair, shining at a magnitude of 0.75, is the twelfth brightest star in our sky. At a distance of 16.7 light-years, Altair is one of the closest stars visible to the naked eye and one of our nearest stellar neighbors. This star’s rapid rotation, 10 hours to complete one cycle on its axis, causes Altair to flatten at its poles. Altair, along with Deneb in Cygnus, and Vega in Lyra, form the asterism known as the Summer Triangle.

The only easily visible planet during these nights is Saturn. You’ll find Saturn about twenty degrees above the southwestern horizon around 9 pm. NASA’s Cassini spacecraft recently completed its second flyby of Saturn’s moon, Dione. Cassini came within 295 miles of the surface, revealing many details of the solar system’s 15th largest moon. Discovered by Giovanni Domenico Cassini in 1684, Dione is the fourth largest of Saturn’s 62 moons. The Cassini spacecraft will go on to explore water-rich Enceladus later this year, passing as close as 30 miles from its surface and passing through the icy geyser spraying out from the moon. A medium sized telescope will enable you to see five of Saturn’s moons. Wednesday night, look furthest on the opposite side of Saturns’s largest moon, Titan, for Dione.

Mars rises around 4 a.m. in the constellation Cancer, followed by Venus an hour later. The two planets will be separated by 10 degrees. Look for the Beehive Cluster, M44, approximately 4 degrees above Mars. This month marks the third anniversary of the rover Curiosity’s landing on Mars. Curiosity has traveled 7 miles in that time, and along the way, discovered an ancient riverbed that may have supported life. Curiosity is currently making its way up Mount Sharp, a Mount Ranier-size mountain at the base of the red planet’s Gale Crater.

Skywatch Line for Monday and Tuesday, August 17th and 18th

This is the Dudley Observatory Skywatch Line for Monday and Tuesday, August 17th and 18th written by Joe Slomka.

The Sun sets at 7:54 PM; night falls at 9:41. Dawn breaks at 4:06 AM and ends with sunrise at 6:05.

The three-day-old Moon lights the darkening sky. Appearing ten percent illuminated, it blazes at minus fifth magnitude, low in the southwest. Tuesday sees a fatter and brighter Moon close to the bright star Spica. The Moon sets after 9 PM on both nights.

Mercury appears lower in the western sky. It shines at zero magnitude and hovers about three-and-a-half degrees above the unobstructed western horizon. Powerful binoculars or any size telescope should reveal Mercury to be about three-quarters illuminated. Mercury sets around 8:46 PM.

Saturn is the easiest planet to see tonight, lying midway between Libra and Scorpius. It is moderately high in the Southwest and easy to spot, shining a bit brighter then Mercury. Normal binoculars hint at the rings; but a telescope brings out the full beauty of the ring system. Saturn sets about 10:51 PM.

Neptune rises during civil twilight in Aquarius. Neptune, although a giant planet, is so far from Earth that it is only a blue speck among the stars. Around 10 PM, Uranus, another giant planet, rises in Pisces and is brighter and a bit larger in our telescopes; it, too, is a mere dot in telescopes. Astronomy websites, magazines and apps provide charts for these distant members of our Solar System. Both remain up all night.

Mars rises in the eastern sky during civil dawn and inhabits Cancer. Mars appears as a moderately bright red ball amid the growing sky glow. Before the sky gets too bright, early risers could see Mars and the Beehive Star Cluster in the same binocular field. Telescopic views reveal Mars almost “full.”

This month, the American Southwest and Mid-West experiences a heat wave. Recently, a local television weatherman used the phrase “Dog Days.” That expression harks back to antiquity. Although most people observe the constellation Canis Major, the Big Dog, in winter, it, and its brightest star, Sirius, rises just before sunrise. Ancient Mesopotamians, Egyptians, Greeks and Romans knew this. All regarded the constellation as a dog. The word “Sirius” comes from the Greek for “scorching.” Indeed, the star rises during the hottest time of the year for the Northern Hemisphere. These cultures considered the constellation bad news. The heat was reputed to cause people and animals to become feverish, mad or warlike. Myths say men turned into werewolves, while animals contracted rabies. Today, we see the star a brilliant white; however, some ancient astronomers described it as “reddish.” When Sirius first rises, it is, of course, low on the horizon, and appears red, just like a newly risen Sun. The Egyptians did find one bright spot during the Dog Days. The rising of Sirius also signaled the beginning of the annual Nile floods. These floods not only irrigated farms but also deposited vital nutrients, fertilizing the soil.

Skywatch Line for Wednesday, August 19th and Thursday, August 20th

This is the Dudley Observatory Skywatch Line for Wednesday, August 19th and Thursday, August 20th written by Louis Suarato

The 24% illuminated, waxing crescent Moon will be approximately 20 degrees high over the western horizon after sunset Wednesday evening. The Moon will set a few minutes before 10 pm. As the sky darkens, you’ll be able to spot Virgo’s brightest star, and the 15th brightest star in the sky, Spica, a few degrees below the Moon. Spica, also known as Alpha Virginis, is a binary star whose components are separated by about 11 million miles and orbit each other every four days. Located about 250 light-years from Earth, Spica’s primary star is 10 times more massive than our Sun, and 7 times larger.

Thursday evening, the Moon will be almost halfway between Spica, to its lower right, and Saturn, to its upper left.Cassiopeia is above the northeast horizon during these nights. This circumpolar constellation is home to many open star clusters and can be used to find two prominent deep sky objects. Begin at the middle star at the center of Cassiopeia’s “W”, a star named Navi or Gamma Cassiopeiae, and follow the line through star at the bottom of the shallower “V”. That star is known as Ruchbah, or Delta Cassiopeiae. Eight degrees below Ruchbah is the deep sky object known as the Double Cluster or Caldwell 14. Caldwell 14 is comprised of two wonderful binocular targets, open clusters NGC 869 and NGC 884. Located at a distance of 7,500 light-years, these clusters are relatively young, aging 12.8 million years. You can also use Cassiopeia to find M31, or the Andromeda Galaxy. The star at the bottom of the deeper part of the “W” is known as Shedir or Alpha Cassiopeiae. Follow the arrow formed by the deeper “V” approximately 18 degrees to the Andromeda Galaxy. In was only 90 years ago when Edwin Hubble settled the debate of whether M31 was within the Milky Way and determine it was a separate galaxy.

The Albany Area Amateur Astronomers invite you to join them for their annual meeting and star party to be held at the Landis Aboretum in Esperance, NY, Thursday evening beginning at 7:30 pm. The August meeting at Landis is canceled if the skies are mostly cloudy. Cancellations will be posted on the Dudley Facebook page and Astro_Albany.