Skywatch Line for Monday and Tuesday, March 28th and 29th

This is the Skywatch Line for Monday and Tuesday, March 28th and 29th.

The Sun sets at 7:17 PM; night falls at 8:54. Dawn begins at 5:05 AM and ends with the Sun rising at 6:42.

Jupiter is the only bright Solar System member visible until after Midnight. Its minus 2.4 magnitude outshines all the bright stars nearby, including the sky’s brightest star – Sirius. Jupiter is parked near Leo’s hind leg, and is best observed about 11:30 PM. Jupiter sets at 6:05 AM.

As has been mentioned during the last few weeks, this is the “season” for double shadow transits. Tuesday, after Midnight, one takes place; it will be a telescopic observer’s dream. Jupiter’s moon Io begins to cross the planet’s face; at 2 AM, the Jovian moon Europa begins its trek. At 2:10, Io’s shadow follows its moon. Europa’s shadow follows its moon at 3AM. By 4:47 AM, both moons and their shadows exit Jupiter. During this event, Io and Europa bracket the Great Red Spot, a giant storm on Jupiter. The Great Red Spot, without accompanying moons, can also be seen at 10:11 PM, Tuesday. Several more double shadow transits occur during the first week of April.

The southern sky becomes crowded after Midnight. The twenty-day-old Moon rises in Ophiuchus and remains up the rest of the night. Tuesday it appears about 72 percent; Wednesday sees it shrink to 62 percent.

The Moon has company. Mars, in Scorpius, rises shortly before the Moon and accompanies it. Tuesday night it is about seven degrees West of the Moon; Wednesday finds it nineteen degrees away. Mars continues to brighten and grow larger in our telescopes. It is now at minus 0.5 magnitude bright, 11.5 arc seconds in diameter, and about 92 percent illuminated.

In Ophiuchus, Saturn rises about 12:48 AM about nine degrees East of Mars. Its ring system is always worth viewing. The bright star Antares, in Scorpius, lies about six degrees below Mars. Tuesday’s Moon-Saturn-Mars-Antares grouping is also a sight one should not miss.

Skywatch Line for Friday, March 25, through Sunday, March 27, 2016

This is Dudley Observatory’s Skywatch Line for Friday, March 25, through Sunday, March 27, 2016, written by Alan French.

Reaching full this past Wednesday, the Moon is moving toward last quarter, so a waning gibbous Moon rises in the late evening. Moonrise is at 9:25 PM Friday, 10:22 PM Saturday, and 11:18 PM Sunday.

The Sun now sets around 7:15 PM and the last vestiges of twilight are gone just before 9:00 PM, so there will be a short window of dark moonless skies Friday, with increasingly long windows on the following nights.

With the improving weather it’s a good time to learn the constellations or expand your knowledge. It’s fun to know your way around the night sky and comes in handy when a new comet makes an appearance. Some comets are bright and obvious, so they’re easy to find. But many are only faintly visible to the unaided eye or only visible with binoculars. Without a frame of reference these can be hard to spot. Everyone wanted to see Halley’s Comet back in 1986. It was visible by eye for a while, but you needed to know where to look, and there was a longer period when binoculars were required to spot it. For people unfamiliar with the sky, it was almost impossible to find.

The simplest gadget for learning the constellations is a planisphere. A disk with the stars and constellations visible from our latitude rotates within a window and can be set for any time on any night of the year. Planispheres do not know Daylight Saving Time, so set if for an hour earlier than the current time. Use a dim red light to view the planisphere – this preserves your eye’s night vision.(You can simply put red plastic or construction paper over a regular flashlight.)

Today, most people use a planetarium app on their phone, tablet, or other electronic device. These are very handy and easy to use, but they have one drawback – they are often too bright to preserve your night vision, even when set on “night mode.” Many do have a strong advantage – you can point your device at the sky and it will show and identify what you’re looking at. Handy, but it’s still useful, fun, and rewarding to know your way around the sky without such help.

Spending time enjoying the night sky has other benefits. I often hear the unmistakable “Who cooks for you? Who cooks for you-all?” call of the Barred Owl. On some nights a Great Horned Owl, with his deep, muffled rhythmic “ho hoo hoohoododo hooooo hoo.” On rare occasions the chilling descending whinny of an Eastern Screech Owl breaks the quiet of the night.

The verbal descriptions of owl vocalizations are often adequate, especially for the Barred Owl, one of our most common owls, but today you can find audio recordings on the web, nicely allowing you to learn “Who’s” around at night. You can start with the Great Horned Owl here, and then “Search” the site for the other owls.

Skywatch Line for Monday and Tuesday, March 21st and 22nd, 2016

This is the Skywatch Line for Monday and Tuesday, March 21st and 22nd.

The Sun sets at 7:09 PM; night falls at 8:45. Dawn breaks at 5:19 AM and ends with the Sun rising at 6:43.

The twilight sky contains Jupiter and a nearly “Full” Moon.

The Moon rises just before sunset and remains up the rest of the night. Monday night finds the Moon only two degrees from Jupiter. Both sit by the hind leg of Leo, the Lion. Tuesday sees the Moon migrated to Virgo. Although the Moon turns officially “Full” on Wednesday morning, the Moon is for all practical purposes “Full” all Tuesday night. The Moon sets at sunrise Tuesday morning, and at 7 AM on Wednesday.

Jupiter, as mentioned, lies by Leo’s hind leg. Jupiter, the Moon and the star Sigma Leonis form a neat triangle, visible in binoculars. As mentioned last week, this is the “season” for “double shadow transits.” Monday night, at 11:43 PM, the Jovian moon Europa begins to cross Jupiter’s face with its shadow trailing. Another Jovian satellite, Io, begins its transit at 11:56 PM, followed by its shadow at 12:15 AM on Tuesday. The two moons and their shadows cross Jupiter until they exit by 3:11 AM, Tuesday. Several more double shadow transits occur this month.

Mars rises in Scorpius at 12:24 AM. The Red Planet daily becomes brighter and larger in our telescopes. Its distinctive color makes finding it in the Scorpion’s head easy. Last week, the Mars Reconnaissance Orbiter (MRO) celebrated its 10th year photographing the Martian terrain. Over the decade, the MRO changed both scientific and popular views of Mars. Once thought dead and lifeless, the MRO demonstrated that Mars has varied surface features and good evidence for at least some subsurface water. It also serves as a relay for signals to Earth from the Opportunity and Curiosity rovers.

Saturn rises about an hour after Mars and is located in the dim constellation Ophiuchus.  Saturn is slightly dimmer than Mars, which is eleven degrees away. Can you tell the difference? Saturn is best observed about 5 AM, when it is highest before Dawn begins. Its famous rings are still tilted to maximum for our enjoyment.

Since Jupiter and Saturn are visible simultaneously, comparisons are in order. Both are gas giants – planets composed mostly of gas. Jupiter is larger; Saturn is about a third of Jupiter’s mass. In telescopes, Jupiter’s colored bands signify very active weather systems; one storm, the Great Red Spot, has been continuously observed for centuries. Saturn’s weather appears more subdued, with occasional faint features. Saturn’s   ring system is easily visible from Earth; Jupiter’s rings are observable only from space-borne telescopes. Both planets’ 120 moons account for most of the Solar System total. Four of Jupiter’s moons appear in binoculars, while Saturn’s satellites can only be spotted through a telescope. Jupiter’s moon Io is the most volcanically active moon in the Solar System; while Europa, Ganymede and Callisto may conceal oceans beneath their icy surfaces. Saturn’s moons Enceladus and Titan are geologically active, spurting ice fountains. Titan is the only moon to have an atmosphere; its atmosphere contains cold methane, rather than oxygen. Titan also has vast lakes of liquid methane on its surface.

Skywatch Line for Friday, March 18, through Sunday, March 20, 2016

This is Dudley Observatory’s Skywatch Line for Friday, March 18, through Sunday, March 20, 2016, written by Alan French.

The Moon was at first quarter last Tuesday and is moving toward full, so a waxing gibbous Moon dominates the night sky this weekend. The Moon will be full next Wednesday.

We’ve been writing about Jupiter’s Galilean moons and how they are easily visible in any telescope. This weekend features some close pairings of moons.

Look for Jupiter toward the east southeast at 9:00 pm. On Friday night all four moons will be on one side of the planet. Io and Europa will be nearest Jupiter and very close together – in some telescopes it may be hard to split the pair and they may look like a single, perhaps, elongated star, especially if the air is unsteady and the planet itself appear to shimmer. Callisto is next farthest away with Ganymede most distant.

On Saturday at 9:00 pm three moons will be on one side of the planet and the fourth, Io, will be on the opposite side. Ganymede will be closest to the planet with Europa a little farther away, with Callisto well away from the planet.

By Sunday Ganymede and Europa, close together, will be on one side and Io, closer to the planet, will be on the other side. Considerably farther away on that side you’ll find Callisto.

Even when we don’t write about the moons they are fun to follow from night to night and hour to hour. Apps are available that show the positions of the moons and various Galilean satellite events.

From our perspective, the Galilean moons shuttle back and forth. When they are moving from east to west they cross in front of Jupiter. As they move from west to east the go behind the planet and vanish from sight. Both Jupiter and its moons cast shadows, so the moon’s shadows can appear on the cloud tops of the planet, and the moons can be seen moving into or out of Jupiter’s shadow as they pass behind the planet.

A moon moving in front of the planet is called a transit. When a shadow moves across the planet it’s a shadow transit. Apps give times for moon and shadow transit beginnings, known as ingress, and moon and shadow transit ends, known as egress.

A moon can disappear behind the western limb of Jupiter, being hidden or occulted by Jupiter. It can also emerge from behind the planet, an occultation end. Right now Jupiter’s shadow lies to its east, so a moon emerging from behind the planet’s eastern limb is in the shadow – eclipsed – and invisible at first. Then it moves out of Jupiter’s shadow into sunlight and becomes visible.

Skywatch Line for Wednesday, March 16th and Thursday March 17th

This is the Dudley Observatory Skywatch Line for Wednesday, March 16th and Thursday March 17th written by Louis Suarato

During these last weeks of winter, the constellation Orion is high above the southwestern sky after sunset. Follow Orion’s belt south to Sirius, the brightest star in our sky, and west to Aldebaran, the brightest star in the constellation Taurus. Follow Orion’s belt beyond Aldebaran to find the Pleiades star cluster. At the distance of 8.6 light-years, Sirius is one of the closest stars to our Sun. A blue white star, Sirius sometimes appears to emit a rainbow of colors, as its light passes through Earth’s atmosphere. Sirius is a binary star, consisting of a smallcompanion, Sirius B, also known as the Pup. Sirius B can only be seen with the power of a telescope. Look about 4 degrees below Sirius for the open cluster M41. Also known as NGC 2287, this open cluster was discover by Giovanni Batista Hodierna before 1654. M41 contains about 100 stars and forms a triangle with the star Nu Canis Majoris and Sirius, and all three can be seen in the same field of view with binoculars. This cluster of stars covers a field as large as the Full Moon. 

Jupiter rises after 6 p.m. Wednesday and will be about 20 degrees over the eastern horizon after sunset. Around 8:30 p.m., you’ll notice a bright star rising in the east-northeast. That star is Arcturus, the brightest in the constellation Bootes. Arcturus is the second brightest star in our night sky, and is known as a harbinger of Spring, as it begins its rise at the time of the vernal equinox. Mars rises about 30 minutes after midnight at the head of Scopius, followed by Saturn an hour later. The two planets form a triangle with Antares, Scorpius’ brightest star. Look before dusk when the three are high in the south. The 71% illuminated, waxing gibbous Moon rises at 1:41 p.m. Thursday afternoon. As darkness falls, you’ll discover the Moon is between the bright stars Pollux in Gemini, above, and Procyon, below. Procyon is the brightest star in Canis Minor. 

The Albany Area Amateur Astronomers invite you to join them at miSci in Schenectady for their monthly meeting Thursday, March 17th at 7:30 pm. This month, our speaker is club member Sam Salem, on the recent reports of a possible large planet beyond the orbit of Pluto. This talk gives an overview of how human perception of celestial geometry evolved, from Ptolemy, to Kepler, to Einstein, to accommodate new facts.

Skywatch Line for Monday and Tuesday, March 14th and 15th, 2016

This is the Skywatch Line for Monday and Tuesday, March 14th and 15th.

Now that Daylight Saving Time is in effect, the Sun sets at 7:01 PM; night falls at 8:35. Dawn breaks at 5:32 AM and ends with sunrise at 7:06.

The darkening sky reveals one planet and the Moon. The Moon, in Taurus, rose earlier, and, by Civil Dusk, is high in the sky. Monday shows it about 40 percent illuminated; Tuesday finds it in Orion at First Quarter, when it is at its highest at 7:15 PM. The Moon sets around 2 AM.

Jupiter rose at 6:15 PM, and is located near Leo’s hind foot. While binoculars provide views of Jupiter and its four Galilean moons, telescope users can see the Great Red Spot (a giant storm) at 12:49 AM and 8:40 PM on Tuesday. Sky watchers on Monday night can see the moon Europa begin to cross Jupiter’s face, followed by its shadow at 9:46. At 10:12 PM, Io, another moon, begins its trek across Jupiter, followed by its shadow at 10:20. This double shadow transit, as this event is called, is one of several that takes place this month. By 12:37 AM on Tuesday, both moons and their shadows leave Jupiter’s surface. Jupiter remains up all night.

Mars, in Scorpius, rises about 12:41 AM. The Red Planet now shines at minus 0.1 magnitude and appears about 91 percent illuminated. Mars is located near the Scorpion’s head, about eight degrees from the bright star Antares. Note their color. Both Mars and Antares appear red in our telescopes, but for different reasons. Mars appears red because that is the color of its soil. Antares is red due to its old age. More about Antares in a minute.

Saturn rises about an hour after Mars. It inhabits the dim constellation Ophiuchus, and lies about twelve degrees East of Mars. It is slightly dimmer than Mars. Can you tell the difference? Its cream color stands out amid the dim stars. The rings are at maximum tilt for our enjoyment. Telescopes are preferred instruments to see the rings and a few of Saturn’s 62 satellites.

Venus rises at 6:25 AM and is very low on the horizon. Even though it blazes at minus 3.9 magnitude, Venus requires an unobstructed eastern horizon to find it.

About Midnight, the constellation Scorpius lies due South. Its brightest star, the Lucida, is Antares. The Greek name means “Rival of Ares,” the Greek version of the Roman god Mars. Antares is one of the brightest stars in the northern sky. It is one of only two bright supergiant stars, the other being Betelgeuse. Antares is truly a giant star. Its diameter is 600 million miles. Antares lies about 600 light years away; only Betelgeuse is closer. This star is nearing the end of its life. It is slightly variable, and will, one day, blow itself up as a supernova. In 1970, Antares became the first star, proven to emit radio waves.

The Albany Area Amateur Astronomers hold their monthly meeting on Thursday, March 17th at 7:30 PM at miSci.

This month, club member Sam Salem talks about how human perception changed our view of planetary motions.

Skywatch Line for Friday, March 11, through Sunday, March 13, 2016

This is Dudley Observatory’s Skywatch Line for Friday, March 11, through Sunday, March 13, 2016, written by Alan French.

This weekend marks the beginning of Daylight Saving Time, so set your clocks ahead by one hour before retiring on Saturday night.

The Moon was new last Wednesday and is moving toward first quarter. A waxing crescent Moon will be visible in the early evening sky after sunset.

Look for the lunar crescent toward the west as darkness falls Friday night. The Moon will set at 9:21 pm. The Moon will be fatter and higher on Saturday night and will set at 10:33 pm. Because the clocks spring ahead Sunday morning, moonset is after midnight on Sunday, at 12:41 am Monday morning.

We recently wrote about the four brightest moons of Jupiter – Io, Europa, Ganymede, and Callisto, and how they are visible through even a very modest telescope. The four were discovered by Galileo in 1610 and were the first moons discovered orbiting another planet. They are known as the Galilean moons.

Io is the Galilean moon closest to Jupiter, taking less than two days (1.77 days) to orbit the planet. Hence its positions changes markedly from night to night. Io is very active and has hundreds of volcanoes, spewing material high above its surface. The material continues to resurface the moon’s landscape, which is covered with lava flows and liquid sulfur. The volcanoes are powered by the immense tidal forces stretching Io as it orbits close to Jupiter. These strong tidal forces can raise surface features by as much as 100 meters.

Europa is the next farthest moon away from Jupiter, taking just over three-and-a-half days (3.55 days) to orbit the planet. It is the smallest of the Galilean moons and its surface is largely covered with water ice. Tidal forces are smaller on Europa because of its greater distance from Jupiter, but the heat they generate may produce a liquid ocean under its icy crust. Some astronomers believe strongly that we should explore Europa’s oceans and look for life there.

Third outward from Jupiter is Ganymede, the largest moon orbiting the planet and the largest moon in our solar system. It travels around the planet in just over 7 days (7.15 days). Its surface is dominated by ancient cratered regions, bright linear features, mountain ranges, and flows of water ice.

The Galilean moons are tidally locked – one side is always toward Jupiter. The inner three moons are in resonant orbits. Europa makes one orbit for every two orbits of Io, and Ganymede makes one trip around Jupiter for every four of Io.

Farthest from Jupiter, of the four Galilean satellites, is Callisto, which makes a leisurely seventeen day (16.69 days) journey around the planet. It is not in a resonant orbit nor is it affected by tidal forces.

Skywatch Line for Wednesday, March 9th and Thursday, March 10th, 2016

This is the Dudley Observatory Skywatch Line for Wednesday, March 9th and Thursday, March 10th written by Louis Suarato

The 1% illuminated, waning crescent Moon will be a challenge to see as it sets an hour after the Sun on Wednesday. The crescent Moon will be easier to see when it is 5% illuminated, and higher above the horizon after sunset Thursday evening. The moonless sky offers its evening highlights early as Jupiter climbs above the eastern horizon. Jupiter reached opposition Tuesday, and shines at magnitude -2.5. As you look at Jupiter’s Galilean moons throughout the night, you’ll notice Ganymede and Io to one side and Europa and Callisto on the other side, all moving away from the planet. Thursday night, Jupiter’s Great Red Spot, a 200 to 400 year old storm, twice as large as planet Earth, begins its transit at 8:30. This storm, with winds peaking at 400 miles per hour, orbits the planet counter-clockwise, with a period of about six days.

Mars rises between Libra and Scorpius around midnight. Earth and Mars are moving toward each other, by 25,954,000 miles, until Mars reaches opposition on May 22nd. Saturn rises in the constellation Ophiuchus after 1 a.m. Thursday. Rising alongside Saturn, to its right, is the globular star cluster NGC 6235, also known as Mel 154. Ten degrees to the right of NGC 6235 is the globular star cluster M4. The distance between Mars and Saturn is also closing, from 18 degrees to 9 degrees throughout March. Venus joins the morning planets, rising at 5:30 Thursday.

There will be a bright International Space Station pass over our region early Thursday morning. The ISS will appear in mid-sky, between the handle of the Big Dipper and Arcturus, at 4:39 a.m., and travel toward the northeast horizon.

The Moon reaches perigee, the closest to Earth during this lunar cycle, at 2:04 a.m. Thursday, at a distance of 223,389 miles.

Skywatch Line for Monday and Tuesday, March 7 and 8, 2016

This is the Skywatch Line for Monday and Tuesday, March seventh and eighth.

The Sun sets at 5:53 PM; night falls at 7:27. Dawn breaks at 4:44 AM and ends with sunrise at 6:18.

The Moon turns “New” Tuesday evening and is not seen either Monday or Tuesday evening.

The darkening sky contains only one bright planet – Jupiter. Jupiter rises at 5:45 PM and is found near Leo’s hind leg. Jupiter is at opposition Tuesday morning and sets shortly after sunrise. While binoculars readily show Jupiter and its four Galilean moons, telescopes present an exciting sight Monday evening – two shadows on its face. The satellite Europa and its shadow began their trek across the planet during Jupiter’s rise. At 7:28 PM, the shadow of the moon Io joins Europa’s, followed by Io itself. Both shadows can be seen through most amateur telescopes. Europa and its shadow exit Jupiter at 8:58 PM.  Io and its shadow exit at 9:43 PM. Telescopic observers can also see the Great Red Spot, a giant storm, on Jupiter at 12:13 AM and 8:04 PM Tuesday.

The planet Uranus still inhabits Pisces. However it is quite low in the western sky and sets at 8:28 PM.

Midnight sees Jupiter at is highest and best observed around Midnight. Meanwhile, Mars rises before Midnight. Mars is now at zero magnitude and also growing bigger in our binoculars and telescopes.

Saturn joins the scene by rising at 1:10 AM in the dim constellation Ophiuchus. It is slightly dimmer than Mars, but its cream white orb stands out amid the stars. Saturn’s rings are not to be missed, especially by first time sky watchers.

Venus rises before Civil Dawn. It appears very low on the eastern horizon; an unobstructed view may be necessary to find it. Venus blazes at minus 3.9 magnitude and is 92 percent illuminated.

If you observe from a rural dark site, Jupiter is about 18 degrees to the left of a dim roughly triangular small constellation. This constellation is Sextans.

Most constellations are related to mythical people or objects. In the 16th and 17th centuries, new constellations were devised to celebrate newly discovered star patterns and high technology of the times.  One of these constellations is Sextans, the Sextant. Sextans is found between Leo’s front paws and the constellation Hydra.

Johannes Hevelius was a Polish astronomer in the port city of Gdansk (also known as Danzig).  Prominent in local politics, his true passion was astronomy. In 1641, he built a private observatory that included a 150-foot telescope. However, he did most of his work with a six-foot brass sextant. He was inducted into Britain’s Royal Society in 1664.  A sextant contains an arc, one-sixth of a circle. It has a moveable arm that permits measurement of angles. In 1679, fire destroyed his observatory.  He immortalized his loss with an invented constellation, Sextans, and rebuilt his observatory.  Sextants still exist. Sailors use a version that includes a small telescope on the swinging arm and mirrors. Along with an accurate clock and astronomical almanac, the navigator locates his position at sea. That skill is being lost to the increasing use of GPS to fix a position with unprecedented accuracy.

Skywatch Line for Friday, March 4, through Sunday, March 6, 2016

This is Dudley Observatory’s Skywatch Line for Friday, March 4, through Sunday, March 6, 2016, written by Alan French.

The Moon reached last quarter last Monday and is now moving toward new, which occurs this coming Tuesday. A slender old Moon will grace the morning sky before sunrise.

At 5:30 AM on Saturday morning a 17-percent illuminated crescent Moon will be low in the southeast, just under 14 degrees above the horizon. At the same time Sunday morning, an even thinner crescent – just 9-percent in sunlight, will be just over 7 degrees above the horizon in the east southeast.

The dark moonless skies this weekend are ideal for enjoying the beauty of the winter sky before it vanishes in the west. At 8:00 PM the familiar bright stars of winter are almost due south, with brilliant Sirius, the brightest star in the night sky, 30 degrees above the horizon.

Sirius is bright mostly because it is a nearby neighbor, lying at a distance of just 8.7 light years. With a luminosity of a bit over twenty times that of our Sun, it is pretty typical of the stars we see.

It can be hard to get a real concept of the vastness of space and the large distances between our solar system and even our nearest neighbors. A popular model of our solar system begins with a Sun the size of a bowling ball. On this scale our Earth is the size of a peppercorn and is 26 yards from the bowling ball Sun. The farthest planetary member of our solar system, Neptune, would lie 778 yards away and be the size of a peanut.

When we start adding the nearby stars to our model, the distances grow much larger. In our model, Sirius would lie 8,070 miles away. The nearest star in our nighttime sky, Proxima Centauri, would be 4,000 miles from our bowling ball Sun.

If you are away from the light polluted skies of our cities and larger towns, look for the band of light that marks the winter Milky Way, stretching upward a bit east of due south, passing east of Sirius, up above Orion, and passing west of bright Capella high overhead. The Milky Way narrows and dims past Capella, then brightens and broadens as it move down toward the north northwestern horizon.

In the winter we are looking outward in our galaxy, away from its center. The region of Taurus and Auriga, where you see a marked dimming, is directly away from the galactic center. Largely because there are fewer stars in the outer part of the galaxy, this part of the Milky Way is faint.

The region passing through the conspicuous “W” pattern of stars marking Cassiopeia is quite rich in stars. It’s a wonderful area to explore with binoculars, especially from the comfort of a lawn chair.