Skywatch Line for Wednesday, April 18th, and Thursday, April 19th, 2018

This is the Dudley Observatory Skywatch Line for Wednesday, April 18th, and Thursday, April 19th, written by Louis Suarato.

The 12% illuminated, waxing crescent Moon sets at 10:38 Wednesday night. After sunset, the Moon forms a triangle with the Pleiades star cluster and Venus. Look about 12 degrees north of the Moon for the Pleiades, and 8 degrees below the Pleiades for Venus. All planets, with exception of Venus, rotate clockwise. Venus rotates counter-clockwise, and unlike other planets, the Sun rises in the west and sets in the east. Venus rotates at a relatively slow speed of 4 miles per hour, or once every 243 Earth days. Venus orbits the Sun once every 224.7 Earth days, making a Venusian day longer than its year. If you were on the surface of Venus, you would experience a sunrise and sunset only once every 1.08 years. Uranus is different than other planets in that it rotates on its side. That means that for 42 years Uranus’ south pole face the Sun, and for 42 years, Uranus north pole faces the Sun. This unique rotation provides each pole with 42 years of continuous sunlight or darkness. Thursday night, the Moon will be 2 degrees below Taurus’ brightest star, Aldebaran.

Jupiter rises at 9:26 p.m. in Libra. Almost simultaneously, Jupiter’s largest moon, Ganymede, is occulted by the planet. Ganymede’s occultation ends at 10:39 p.m. as the moon reappears from behind the pole of the gas giant. Saturn rises at 1:15 a.m. in Sagittarius, followed by Mars 42 minutes later. Before dawn, the two planets are high in the south-southeast. Mars, slightly brighter than Saturn, is on the left. The red and ringed planets are separated by about 10 degrees. Saturn becomes stationary on Wednesday, and begins its retrograde, or westward motion. Saturn is also at aphelion, its furthest distance from the Sun since 1959.

The Albany Area Amateur Astronomers invite you to join them Thursday evening at miSci, beginning at 7:30 p.m., for their monthly meeting. The guest speaker is Dr. E. Bruce Watson, professor of Earth and Environmental Sciences at RPI. Dr. Watson specializes in the geochemistry of deep Earth in the lower crust and upper mantle. His topic will be “Ancient Crystals in the Early Earth”. Dr. Watson is a graduate of the University of New Hampshire and earned his Ph.D. from MIT. Dr. Watson has over 300 publications to his name.


Skywatch Line for Monday and Tuesday, April 16th and 17th, 2018

This is the Skywatch Line for Monday and Tuesday, April 16th and 17th.

The Sun sets at 7:39 PM; night falls at 9:22. Dawn begins at 4:27 AM and ends with the Sun rising at 6:10.

Venus, in Aries, is the brightest object in the darkening western sky. It blazes with minus 4th magnitude, appears about 91% lit and lies about 16º above the horizon. It sets at 9:41 PM.

The one-day-old Monday’s Moon lies 13º below Venus and about 2º above the horizon. It shines with 2nd magnitude and appears as a thin 1º crescent. It sets at 8:23 PM. Binocular and telescopic observers can see this very young Moon if they have an unobstructed horizon. This writer once caught a similarly young moon using both binoculars and telescope. Tuesday’s Moon is brighter, about 5% lit, about 13º high and sets at 9:34 PM.

Jupiter, in Libra, rises about 9:32 PM and blazes at minus 2nd magnitude. It is a best observed at 2:29 AM. Telescopic viewers can see the Great Red Spot (a giant Jovian storm) at 11:19 PM Monday and at 5:06 AM on Wednesday. They can also witness the moon Europa’s shadow begin to cross the planet’s face at 11:36 PM on Tuesday, followed by Europa itself at 12:37 AM Wednesday; Europa’s shadow exits at 1:51 AM Wednesday, followed by Europa at 2:45 AM.

Sagittarius houses three Solar System members. Saturn rises at 1:19 AM, shining with zero magnitude and about 10 arc-seconds in size. Saturn is at aphelion (most distant from the Sun) and also it is stationary in our sky. Note its position. Saturn soon begins retrograde motion, which means that it travels westward. Saturn is also high enough for telescopes to capture its rings and moons.

Mars rises about a half-hour after Saturn. It shines with minus zero magnitude, appears about 10 arc-seconds in size and 88% illuminated. It is best studied before Dawn and large enough to begin to show surface features. Dwarf Planet Pluto, which is too small and faint for most amateur telescopes, lies about 5º east of Mars.

Asteroid 4Vesta is the final inhabitant of Sagittarius. Rising at 12:33 AM, it shines with 7th magnitude about 28º above the eastern horizon. It is best observed at 5:28 AM. However, its small apparent size requires the use of detailed finder charts from astronomical media.

If the astronomer sees meteors streaking from the constellation Lyra, he is witnessing the beginning of the annual Lyrid meteor shower. Although it peaks on April 22nd, meteors may occasionally appear before that date.

Saturn is high in the Dawn sky. Besides the rings, Saturn has sixty-one moons. One of these, Iapetus, has puzzled observers for centuries. Iapetus is bright when it is on one side of Saturn, but markedly darker when on the other.

Recently, two groups of astronomers think they have figured it out. Iapetus is tidally locked to Saturn, just like the Earth’s Moon – showing the same side to the planet. The leading side of Iapetus sweeps up debris from a newly discovered (and invisible to amateurs) ring. Thus, one side looks like it was covered in chocolate dust, while the trailing side is as white as snow (really ice). In addition, the dust, warmed by sunlight, melts the ice beneath, which flows to the trailing side and re-freezes. Iapetus has a 79.3-day orbit and is visible in amateur telescopes. Astronomy programs and websites assist the observer.

Skywatch Line for Friday, April 13 through Sunday, April 15, 2018

This is Dudley Observatory’s Skywatch Line for Friday, April 13 through Sunday, April 15, written by Sam Salem.

On Friday, the Sun rises at 6:17am and sets at 7:36pm; the waning crescent Moon rises at 5:24am and sets at 5:03pm. New Moon occurs on Sunday at 9:57pm.

The winter constellations are crowded into the west during early evening. Venus gleams at magnitude –3.9 and sits roughly 10 degrees above the horizon one hour after sunset. Jupiter, at magnitude –2.4, clears the east-southeast horizon after 10:00pm. Wait a few hours for the planet to gain some elevation before you turn your scope on it. Jupiter reaches the meridian around 3:15am. Saturn is up shortly after 2:00am and Mars joins it some 20 minutes later. The space between the two planets is starting to grow after they have been keeping each other company for the past several weeks. Both planets are located in constellation Sagittarius and are closely matched in brightness. Saturn gleams at magnitude 0.4, while Mars is a little brighter at magnitude 0.1.

This weekend head over to constellation Cancer, the Crab, the faintest constellation of the Zodiac. Cancer, the Crab, lies between the two brightest starts of Gemini, Castor and Pollux, and Leo’s brightest star Regulus. Try to locate the open cluster M44, also known as the Beehive Cluster in Cancer. M44 is a fine binocular object that’s easy to locate. The one-degree-wide clump of stars is parked midway and a little west of a line joining Delta and Gamma Cancri. At magnitude 3.9, Delta is Cancer’s brightest star. Another delightful open cluster is M67. Nicknamed the King Cobra Cluster, M67 is an open cluster located in the constellation Cancer. It can be found roughly halfway and slightly above the imaginary line connecting the bright stars Regulus in constellation Leo and Procyon in constellation Canis Minor. Under a dark sky the little stellar gathering is visible in steadily held binoculars as a fuzzy patch. M67 is one of the oldest known open clusters and the single oldest open cluster listed by Messier in his catalogue. The estimated age of M67 is in the range from 3.2 to 5 billion years. Open clusters are typically younger and the stars tend to disperse over time, usually before they reach this age. For example, the Beehive Cluster M44 is only 600 million years old.
Constellation Cancer is also home to a number of fine double stars, including Iota Cancri. Iota is a striking sight in small telescopes. It features a 4.1-magnitude yellow star contrasting with a 6.0-magnitude blue companion, separated by a generous 31 arc seconds. The two are easily split in any scope used at low power. The double star is located 7 degrees north of the M44, Beehive Cluster.

Saturday marks the 389th. birthday of the Dutch physicist and astronomer Christiaan Huygens who founded the wave theory of light, discovered the true shape of the rings of Saturn, and contributed to the study of the action of forces on bodies., In 1655, Huygens discovered the first moon of Saturn, later named Titan, using a lens he ground for himself. In 1656, he patented the first pendulum clock, which he developed to enable exact time measurement while observing the heavens. Cristiaan Huygens developed theories on centrifugal force in circular motion, which influenced Sir Isaac Newton in formulating his Law of Gravity. Huygens also studied and drew the first maps of Mars. On January 14, 2005, a NASA space probe, named after Huygens, landed on Titan.

Skywatch Line for Wednesday, April 11th, and Thursday, April 12th, 2018

This is the Dudley Observatory Skywatch Line for Wednesday, April 11th, and Thursday, April 12th, written by Louis Suarato.

The 18% illuminated, waning crescent Moon sets at 2:57 p.m. Wednesday. The Moon rises again, 13% illuminated at 4:57 Thursday morning. Mercury follows the Moon, rising 43 minutes later, 20 degrees from the Sun. With a diameter of 3,032 miles, Mercury is smaller than the two largest moons in the solar system. Jupiter’s largest moon, Ganymede, has a diameter of 3,274 miles, and Titan, Saturn’s largest moon, is 3,201 miles wide. Jupiter’s moon, Callisto has a diameter that is only 37 miles smaller than Mercury, and Io is 68 miles smaller. Venus is low in the west after sunset, 22 degrees elongated from the Sun.

Jupiter rises at 9:58 p.m. in the constellation Libra. Two hours after Jupiter rises, the Great Red Spot begins its transit across the face of the planet. This cyclonic storm has been raging on Jupiter for at least 350 years. With winds estimated at 400 miles per hour, the Great Red Spot is two to three times the size of Earth. Only the winds of Uranus, at 560 miles per hour, and those of Neptune, at 1,500 miles per hour, are stronger. Saturn and Mars rise overnight in Sagittarius, now separated by 4 degrees. Earth continues to close on Mars this month, coming to within 79 million miles on April 30th, with the red planet increasing in magnitude to -0.4.

Thursday is the 50th anniversary of the fall of the Schenectady meteorite. On April 12, 1968, at around 8:30 p.m., a meteorite hit a house in Glenville, NY. The 383.3 gram (approximately 10 ounces) meteorite was discovered on April 14th when the owner, Joseph Kowalski noticed the damage to his roof. Kowalski donated the meteorite to the Schenectady Museum, now known as miSci. According to the U.S. Meteorological Society, two other meteorites have been found in, or near, the Capital Region. A .5 ounce meteorite was found in Bethlehem in 1859, and in 1863, a 3.3 pound meteorite was found in Rensselaer County’s Tomhannock Creek.

The Schenectady meteorite will be on display April 21st at miSci for National Astronomy Day.

Skywatch Line for Monday and Tuesday, April 9th and 10th, 2018

This is the Skywatch Line for Monday and Tuesday, April 9th and 10th.

The Sun sets at 7:30 PM; night falls at 9:11. Dawn begins at 4:42 AM and ends with the Sun rising at 6:22.

The twilight sky has only one bright planet – Venus. Located in Aries, the planet shines with minus 4th magnitude, appears a medium size of 11 arc-seconds and is about 93 percent illuminated. Moderately low in the western sky, it sets at 9:23 PM.

Jupiter rises in Libra and is the brightest object in the constellation. Jupiter rises at 10:03 PM, and by midnight, is 17 degrees high in the eastern sky. Telescopic observers can see the Great Red Spot (a giant storm) at 10:34 PM Monday, and at 4:21 AM on Wednesday. They can also, at 11:17 PM on Tuesday, witness the moon Europa’s shadow leave the Jovian surface, followed by the moon itself at 12:29 AM. Jupiter is best observed at 3:00 AM.

Dawn sees Sagittarius as the site of the main attractions. Saturn rises 1:46 AM, shining at 0.5 magnitude, 17 arc-seconds in size and 21 degrees high in the western sky. The Ringed Planet lies about 47 degrees east of Jupiter. Binocular observers can see the rings tilted nearly to maximum – 25.5 degrees. They can also see Saturn 1 degree above globular star cluster M-22, 4 degrees from globular star cluster M-28 and 3 degrees below open star cluster M-25. Telescopic observers can, at 4:00 AM Tuesday, see 5 Saturnian moons clustered about the planet.

Mars also inhabits Sagittarius, rising at 2:09 AM, shining at zero magnitude and 9 arc-seconds in size. It appears about 88 percent illuminated. Mars is gradually growing brighter, larger, and beginning to be worthy of studying surface features. Sagittarius has one more visitor, 4Vesta. This asteroid is 512 km (312 mi) in diameter and is appropriately small in our telescopes. It rises at 12:55 AM and shines with 7th magnitude, within most amateur telescopes. Observers should consult websites and magazines for detailed finder charts.

Finally, the Moon rises in Capricornus at 3:47 AM Tuesday, and 4:22 AM on Wednesday. It shines at minus 8th magnitude and is 31 percent phase on Tuesday, and 22 percent on Wednesday.

Earlier, we mentioned that Saturn and Mars lie quite close to several star clusters. Throughout the night, star clusters abound. In early evening, we find the Pleiades above the shoulders of Taurus. The Bull’s face is made of another star cluster, the Hyades. The nearby constellation Auriga harbors three clusters. Finally, Cancer contains the Beehive and M 67.

All these are called “Open Clusters.” They appear to contain, at most, a few hundred stars, which are widely spaced and irregularly shaped. Open clusters are relatively young, less than a billion years old. They reside in the disk of a galaxy and are relatively small, about 50 light-years across.

There is another class of star clusters, called “Globular Clusters.” Globular clusters are usually found around galaxy halos and central bulges.
Globulars may contain up to a million stars and are quite large, in a sphere about 100 light-years across. These stars are quite old.

If tonight’s weather is clear, binoculars can show many Open Clusters. Just dress warmly and observe the Hyades, Pleiades and the nearby pentagon shaped constellation Auriga.

Skywatch Line for Friday, April 6 through Sunday, April 8, 2018

This is Dudley Observatory’s Skywatch Line for Friday, April 6 through Sunday, April 8, written by Sam Salem.

On Friday, the Sun rises at 6:29am and sets at 7:28pm; Moon rises at 12:47am and sets at 10:30am. Last quarter Moon occurs on Sunday at 3:17am. The last quarter Moon aligns with the closest apogee of the year, at 404,144 km distance. Apogee is the Moon’s most distant point from Earth in its monthly orbit. This Sunday, the half-lit last quarter Moon almost exactly aligns with lunar apogee. This is the year’s closest coincidence of quarter Moon and lunar apogee, with the two events taking place less than two hours apart.

Venus gleams at magnitude –3.9 in the early evening even as it sits low in the west at dusk. Jupiter, at magnitude –2.4, rises a little before 11pm. Mars and Saturn rise more or less together around 2:45am. The two planets are less than three degrees apart in northern Sagittarius and closely matched in brightness. Mars glows at magnitude 0.2, while Saturn is only a bit fainter at magnitude 0.5. On Saturday morning, Saturn will be the closer of these two planets to the Moon, as the Moon will pass just north of Saturn.

The 5.1-magnitude open cluster, M35, in constellation Gemini is easy to find as it’s located just above the westernmost foot of the Twins, marked by 2.9-magnitude Mu (μ) and 3.3-magnitude Eta (n) Geminorum. 10×50 binoculars show a few individual cluster members in M35. A more powerful telescope has the ability to resolve many more stars. Try to spot M35’s celestial neighbor, the 8.6-magnitude cluster NGC2158. It’s a tough catch in binoculars, but a small scope has no trouble pulling in little NGC2158 in a reasonably dark sky. The two clusters are physically similar but look quite different to us because one is much nearer to Earth than the other. M35 is the closer cluster at roughly 2,800 light-years. It’s only one-fifth the distance of NGC2158.

On April 6, 1852, Edward Sabine announced that the 11 year sunspot cycle was “absolutely identical” with the geomagnetic cycle. Sabine was an Irish geophysicist, astronomer, and explorer, who made extensive pendulum measurements to determine the shape of the Earth, and established magnetic observatories to relate sunspot activity with disturbances in terrestrial magnetism.

Sunday marks another anniversary related to sunspot discovery. On April 8 1947, the largest sunspot group recorded was observed on the Sun’s southern hemisphere. Its size was estimated at 7 billion square miles, or an area of 6100 millionths of the Sun’s visible hemisphere. Sunspots are areas of somewhat cooler surface than the surrounding solar gases, and appear as dark spots on the solar surface. Astronomers measure the sizes of sunspots as millionth fractions of the Sun’s visible area. Typically, a big sunspot measures 300 to 500 millionths. The entire surface area of the Earth is only 169 millionths of the solar disk.

Skywatch Line for Wednesday, April 4th, and Thursday, April 5th, 2018

This is the Dudley Observatory Skywatch Line for Wednesday, April 4th, and Thursday, April 5th, written by Louis Suarato.

The 84% illuminated, waning gibbous Moon sets at 9:14 a.m., and rises again at 11:53 p.m., 80% illuminated, between the constellations Ophiuchus and Scorpius. Scorpius’ brightest star, Antares, can be found to the Moon’s lower right, while Jupiter shines to the Moon’s upper right. Look for Venus before it sets in the west at 9:07 p.m. below the Pleiades star cluster. Saturn and Mars rise in Sagittarius at 2:09 and 2:21 overnight, 2 degrees apart.

Two of the brightest stars in our sky are visible these nights. The brightest, Sirius, in the constellation Canes Major, shines at magnitude -1.45. Sirius is 8.6 light-years away, and this binary system contains two of the eight closest stars to our Sun. Its luminosity is 25 times that of our Sun, which combined with its close proximity, contributes to Sirius’ brightness. Look over the southwestern horizon around 9 p.m. for the brightest star in the sky. Orion’s belt points southward to Sirius. The second brightest star in the sky is Arcturus. Found in the constellation Bootes, Arcturus shines at magnitude 0.15, and along with Virgo’s brightest star, Spica, and Leo’s brightest, Regulus, these stars form the asterism known as the Spring Triangle. Arcturus is 36.7 light-years away and 25 times the diameter of the Sun, and 170 times as luminous. Look for Arcturus after 9p.m. over the eastern horizon. The stars forming the handle of the Big Dipper point down to Arcturus.

There’s a small, faint constellation above Arcturus called Coma Berenices. This constellation is comprised of three 4th magnitude stars forming a 45 degree angle covering 386.5 square degrees.When looking towards Coma Berenices, you are looking perpendicular to the disk of the Milky Way, and away from the stars and dust forming our galaxy, therefor providing the clearest view of galaxies outside of our own. This region contains the Coma Galaxy Cluster, and the Virgo Galaxy Cluster, each hosting more than 1,000 galaxies. It is also the home of 8 Messier objects. Also found within Coma Berenices, is a loose open star cluster known as Melotte 111, or the Coma Star Cluster. This star cluster is about 7.5 degrees wide, or three quarters the width of a fist held at arm’s length, and contains 40 brighter stars ranging from magnitudes 5 to 10. The brightest stars form a V-shape as Coma Berenices is rising. The Coma Star Cluster is 280 light-years away and is approximately 450 million years old. Look for Melotte 111 at the top of Coma Berenices, and to the east of Denebola in Regulus.

Skywatch Line for Monday and Tuesday, April 2nd and 3rd, 2018

This is the Skywatch Line for Monday and Tuesday, April 2nd and 3rd.

The Sun sets at 7:22 PM; night falls at 9:00. Dawn begins at 4:56 AM and ends with the Sun rising at 6:34.

Venus, in Aries, is the sole bright planet in the evening sky. It appears about 94 percent illuminated, glows with minus 4th magnitude, is about 13 degrees high in the southwest and sets at 9:05 PM. Uranus, in Pisces, is becoming difficult to see naked eye. Binoculars or telescopes may pick out the 6th magnitude planet amid the darkening sky, about 7 degrees below Venus. Uranus sets at 8:34 PM.

Libra houses both the Moon and Jupiter. The 17-day-old Moon rises at 9:48 PM on Monday, appearing about 92 percent lit and blazing at minus 11th magnitude; it is best observed at 3:15 AM. Tuesday’s Moon rises at 10:50 PM, appearing a bit dimmer and slimmer, and best observed at 4:03 AM.

Jupiter rises at 10:33 PM, glowing with minus 2nd magnitude. This month, Jupiter brightens a bit and also appears slightly larger. Jupiter is positioned in Libra so that Monday’s Moon lies about 7 degrees above the planet, and Tuesday’s Moon about 7 degrees below. The Great Red Spot can be telescopically observed at 3:36 AM Tuesday.

By Dawn, Mars and Saturn, in Sagittarius, join the Moon and Jupiter. Yesterday, Mars was about the same distance from Earth as Earth is far from the Sun. Mars also brightens from 0.3 magnitude to minus 0.4. Mars and Saturn are in conjunction on April 2nd; they are around 1 degree apart on both nights.

Saturn rises at 2:13 AM, shining at 0.5 magnitude and 20 degrees high in the South; is lies about 47 degrees from Jupiter. Saturn also brightens slightly this month.

Red Planet Mars rises at 2:21 AM, appearing 88 percent lit and 8 arc-seconds in size, which provides marginal telescopic views.

The asteroid 4Vesta is also visible in the Dawn sky. Rising at 1:16 AM, it glows at 7th magnitude and appears as a tiny 0.4 arc-seconds in size. It lies within 2 degrees of the binocular star cluster M-23. Vesta is the fourth dwarf planet to be discovered. It orbits the Sun every 3.6 years, and is nearing opposition, which occurs in June. Like the first three asteroids, Vesta was temporarily named a planet, until astronomers realized their small size. Vesta is the brightest asteroid. It can be seen in binoculars from a dark, rural site. Vesta currently inhabits Sagittarius. Those seeking Vesta should consult magazine articles and web sites to identify the asteroid amid similar looking stars.

Hydra, the Water Snake, wends its way southward beneath Cancer and Leo. Two constellations ride on its back, Corvus and Crater. Corvus is known as either a Raven or a Crow, due to conflicting legends. One story depicts a snow-white Raven as Apollo’s messenger. When the Raven gives Apollo the especially bad news that his wife was unfaithful, the angry god changed the Raven’s feathers black (the color of contemporary ravens) and banished him to the sky. The other myth sees the Crow again as Apollo’s messenger. When the god asks for a cup (Crater) of water, the Crow departs, but is distracted by a fig tree, full of ripening fruit. The Crow took too long, returning with a water snake (Hydra) in his claws. The fuming deity exiled the bird, the snake and the cup to the night sky.

Skywatch Line for Friday, March 30 through Sunday, April 1, 2018

This is Dudley Observatory’s Skywatch Line for Friday, March 30 through Sunday, April 1, written by Sam Salem.

On Friday, the Sun rises at 6:41am and sets at 7:20pm; Moon sets at 6:32am and rises at 6:30pm. Full Moon occurs on Saturday at 8:37am. This is the second full Moon in the month of March, which makes it a “blue” Moon. This is the second blue Moon of 2018. The previous one occurred at the end of January. On Friday and Saturday, watch for the Moon to shine in the vicinity of the 1st-magnitude star Spica from dusk till dawn. The Moon and Spica, the brightest star in the constellation Virgo, light up the eastern sky as darkness falls. They climb highest up for the night around midnight and sit low in the west at dawn.

Mercury has departed the celestial stage after its brief dusk apparition. Venus, the “evening star” is gradually climbing higher. Gleaming at magnitude –3.9, Venus is easy to spot, hovering above the west horizon shortly after sunset and remaining visible until the end of astronomical twilight. Jupiter Rises at around 11:30pm. Shining at magnitude –2.4, Jupiter is at its best at around 4:20am, when it’s highest and due south. As morning twilight begins Mars and Saturn are well up in the south-southwest. The two planets are close both in in northern Sagittarius. Mars, at magnitude 0.3, outshines 0.5-magnitude Saturn by a slight margin. Check out Saturn in the dawn sky. The ideal time to observe Saturn is between 5:30 and 6:00am when the planet is approaching its greatest altitude and before twilight becomes overwhelmingly bright. Try to spot the famous Cassini Division, a 4,700-kilometer-wide gap that separates Saturn’s two brightest rings. With the Saturn rings currently tilted open almost the maximum amount these days, under good seeing conditions, this feature is visible even in a small telescope.

Before sunrise on Monday, see Mars pair up with Saturn in the predawn/dawn sky. At that time, the Moon and Jupiter will have moved over into the western half of sky. Mars and Saturn rise around one and one-half hours after midnight.

On Sunday and through the week, try to spot Sirius with your naked eyes before sunset and follow Vega in the early sunrise into daylight.

Easter and Passover are celebrated this “full Moon” weekend. Easter and Passover are tied to the lunar cycle. Easter is observed on the first Sunday after the first full Moon of spring. The Passover starts in the middle of the Hebrew month of Nissan, when the Moon is full. Nissan usually falls in March or April of the Gregorian calendar.

Skywatch Line for Wednesday, March 28th, and Thursday, March 29th, 2018

This is the Dudley Observatory Skywatch Line for Wednesday, March 28th, and Thursday, March 29th, written by Louis Suarato.

The 91% illuminated, waxing gibbous Moon rises at 4:22 p.m. Wednesday. As the sky darkens, look for Leo’s brightest star, Regulus about 5 degrees to the upper right of the Moon. Venus sets at 8:50 p.m., 77% illuminated. Thursday, Venus and Uranus will be less than a degree apart. Use binoculars in your search for Uranus to the lower right of Venus. Jupiter rises at 10:58 p.m. in Libra. Mars and Saturn rise in Sagittarius at 2:33 and 2:36 a.m., 2 degrees apart. There are two globular clusters 1 to 2 degrees to the lower right of each planet. To the lower right of Mars is the globular cluster M28. Discovered by Charles Messier on July 17, 1764, M28 is 17,900 light-years from Earth, and its stars are estimated to be about 12 billion years old. M28 has a diameter of 60 light-years, and contains at least 50,000 stars. The Great Sagittarius Cluster, also known as M22, is to the lower right of Saturn. When Abraham Ihle found this globular cluster on August 26, 1665 while observing Saturn, it was one of the first to be discovered. At magnitude 5.10, it is one of the brightest globular clusters, and at the distance of 10,600 light-years, M22 is one of the nearest. The estimated 83,000 stars within the Great Sagittarius Cluster are also estimated to be about 12 billion years old.

March 29th is the anniversary of Heinrich Wilhelm Olbers’ discovery of asteroid 4 Vesta. When Olbers observed 4 Vesta for the first time in 1807, it was the only asteroid visible to the naked eye. With a diameter of 326 miles, 4 Vesta is one of the largest objects in the asteroid belt. 4 Vesta is second only to dwarf-planet Ceres in mass, accounting for 9% of the total mass of all asteroids. 4 Vesta formed about 1 to 2 million years after the solar system, around 4.5 billion years ago. Look for 4 Vesta about 10 degrees to the upper right of Mars, and 2 degrees above star cluster M23.