Skywatch Line for Wednesday, May 24th, and Thursday, May 25th, 2017

This is the Dudley Observatory Skywatch Line for Wednesday, May 24th, and Thursday, May 25th, written by Louis Suarato.

Comet C/2015 V2 (Johnson) is well placed for viewing as it travels east to south through the constellation Boötes. Discovered by Astronomer Jess Johnson using the Catalina Sky Survey on November 3rd, 2015, Comet Johnson is now at 6.9 magnitude. The comet will peak in brightness in late June. Look about 30 degrees to the east of Arcturus for this binocular-visible comet. Look further south, and lower, for Jupiter. At magnitude -2.29, Jupiter will be the brightest object in the night sky, before Venus rises at 3:30 a.m. Thursday. Jupiter’s moon, Europa, begins its transit across the planet at 10:50 Thursday night. Two hours later, Io will join Europa. Four minutes later, Europa’s shadow will join the double Jovian moon transit. Saturn rises at 11 p.m. in Sagittarius. You’ll require a clear eastern horizon to see Mercury and the 3% illuminated, waning crescent Moon separated by 4 degrees before Wednesday’s sunrise. The New Moon occurs at 3:45 p.m. Thursday. Lunar perigee occurs 5 hours later, and will cause Perigean Spring Tides, when the gravitation pull of the close Moon induces the oceans to bulge, and creates higher, and lower, than normal tides. At the distance of 221, 958 miles from Earth, this will be the closest lunar perigee of the year.

There will be two extremely bright International Space Station passes over our region Wednesday and Thursday nights. Wednesday, beginning at 10:04 p.m., the -3.8 magnitude ISS will emerge from the west-southwest, pass through the constellation Hydra, continue through Leo and the Big Dipper, before crossing Cygnus and disappearing into the northeastern horizon. Thursday, the -3.7 magnitude International Space Station will rise from the southwestern horizon at 9:12 p.m., and pass close to Jupiter, sail by Arcturus, and pass the binary star Albireo in Cygnus before continuing northeastward.

Skywatch Line for Monday and Tuesday, May 22nd and 23rd, 2017

This is the Skywatch Line for Monday and Tuesday, May 22nd and 23rd.

The Sun sets at 8:18 PM; night falls at 10:23. Dawn begins at 3:20 AM and ends with the Sun rising at 5:25.

The evening sky continues to show Mars and Jupiter. Mars, still in Taurus, shines at first magnitude, appears as a tiny red dot about 10 degrees high and sets at 9:56 PM.

Jupiter, still in Virgo, is moderately high in the southern sky. It shines at minus 2 magnitude, is 41 minutes in size, is best observed at 9:44 PM and sets at 3:31 AM. Telescope users can see the Great Red Spot (a giant storm) at 1 AM on Tuesday. Wednesday, at 12:35 AM, they will also see the Jovian moon Ganymede be eclipsed by the planet; if they have an unobstructed western horizon, they can see Ganymede reappear at 3 AM.

Nightfall sees Saturn, now in Ophiuchus, as a zero-magnitude cream-colored ball three degrees high in the eastern sky. It is best observed at 2:34 AM and sets during daytime.

Besides two planets, there are also two comets in tonight’s sky. The first is Comet Tuttle-Giacobini-Kresak (41P). It is now a ninth magnitude smudge three degrees from 95 Herculis and is best viewed at 3 AM. A new Comet Johnson (C/2015 V2) is binocular visible at 7th magnitude. The comet, in Bootes, is located between the bright star Izar and Delta Bootis. Comet Johnson treks through Bootes towards Arcturus this month and continues into Virgo in June. It is best observed at 11:54 PM and remains up the rest of the night. Astronomy magazines and websites provide finder charts for both comets.

Eighth magnitude Neptune rises at 2:17 AM in Aquarius. By Dawn it is 10 degrees high and a tiny 2.3 arc-seconds in size.

Venus rises in Pisces at 3:32 AM, blazing at minus 4th magnitude and 14 degrees high at Dawn. It appears about 43 percent illuminated and 11 degrees above the Moon.

The very thin Moon also rises in Pisces at 4:15 AM on Tuesday, glaring at minus 5th magnitude, appearing six degrees high and 9 percent illuminated. This is the last easy waning Moon. Wednesday, the Moon migrates to Cetus at minus 2nd magnitude, and only 3 percent illuminated. Although it rises at 4:53 AM, it is very close to the horizon and will be difficult to see amid the brightening sky.
Since Venus and the Moon are so close, let us contrast and compare them. Venus’ acid based clouds reflect 65 percent of sunlight; the Moon reflects only twelve percent. Venus and Earth are almost the same size, while the Moon is about a quarter that of Earth. The Moon is airless, while Venus has a thick, poisonous atmosphere. They display phases for the same reason: they reflect the Sun’s light. Venus orbits the Sun; the phases result from Venus’ approach to and retreat from Earth. The Moon’s phases are due to its monthly orbit around Earth. While the Moon remains almost the same apparent size throughout the cycle, Venus grows larger as it nears Earth and smaller as it recedes.

Skywatch Line for Friday, May 19, through Sunday, May 21, 2017

This is Dudley Observatory’s Skywatch Line for Friday, May 19, through Sunday, May 21, written by Sam Salem.

On Friday, Sun rises at 5:29am and sets at 8:16pm; the Waning Crescent Moon rises at 2:04am and sets at 1:05pm.

Sunday before sunrise, and for the next few mornings, get up early and look east to see the waning crescent Moon and Venus. Mercury is also up before dawn now, less easy to see, closer to the sunrise, but still possible for those with clear skies all the way to the eastern horizon at dawn. The Moon will sweep two degrees south of Venus on Monday morning. Mercury isn’t as bright as Venus and the Moon. Use binoculars to find Mercury near the sunrise horizon. Both Venus and Mercury will remain in the early morning sky through early June. Venus will remain visible at dawn throughout June and for some months to come.

The return of bright globular clusters to the evening sky is a signal that summer is around the corner. This weekend provides a good opportunity to search out for M3. As darkness falls, M3 is in prime position nearly overhead. The easiest way to pin down M3 is to draw an imaginary line connecting the stars Arcturus, the brightest star in constellation Bootes, the Herdsman, and Cor Corali, the brightest star in constellation Canes Venatici, the Hunting Dogs. M3 is situated a little less than half way from Arcturus. Shining at magnitude 6.2, the cluster is an easy catch in binoculars, and will seen as a slightly bloated, fuzzy “star.” Small telescopes will start to resolve individual cluster members.

Corona Borealis, the Northern Crown, is an almost-perfect semi-circle of stars. You’ll find this beautiful pattern in the evening sky from now until October. The constellation Corona Borealis is located almost along a line between two bright stars, Arcturus in the constellation Bootes, the Herdsman, and Vega in the constellation Lyra, the Harp. At nightfall and early evening, you’ll see Arcturus high in the east to northeast, noticeable for its brightness and yellow-orange color. Vega will be rather low in northeast, bright and blue-white in color. The brightest star in Corona Borealis is Alphecca, also known as Gemma, sometimes called the Pearl of the Crown. The name Alphecca originated with a description of Corona Borealis as the “broken one,” in reference to the fact that these stars appear in a semi-circle, rather than a full circle. Alphecca is located about 75 light-years from Earth. It is a blue-white star, with an intrinsic luminosity of almost 60 times that of our Sun.

Friday marks the 107th anniversary of the most intimate contact between the Earth and any comet in recorded history. On May 19, 1910, the Earth passed through the tail of Halley’s Comet. The event was anticipated with dire predictions. A few years earlier, astronomers had found the poisonous gas cyanogen in a comet. As a result, it was surmised that if Earth passed through the comet’s tail everyone would die. Astronomers explained that the gas molecules within the tail were so tenuous that absolutely no ill effects would be noticed. Nevertheless, the panicked portion of the public rushed to buy “comet pills” to counter the effects of the cyanogen gas. Earth had passed through the tail with no harm to Earth inhabitants.

Skywatch Line for Wednesday, May 17th, and Thursday, May 18th, 2017

This is the Dudley Observatory Skywatch Line for Wednesday, May 17th, and Thursday, May 18th, written by Louis Suarato.

You can begin Wednesday’s moonless night by observing Jupiter high above the south-southwestern horizon at twilight. The solar system’s largest planet will be about 40 degrees high around 9 p.m. in the constellation Virgo. Thursday night, at 11:53, Io’s shadow joins Europa’s shadow for a double transit across the face of the planet. Virgo’s brightest star, Spica, shines brightly to Jupiter’s lower left. Look about 15 degrees to the south, or right, of Spica with a telescope for M104, also known as the Sombrero Galaxy. M104 is an edge-on spiral galaxy located about 31 million light-years away. This 8th magnitude deep sky object has a diameter of approximately 50,000 light-years, which is about one-third the diameter of the Milky Way. It is the dark dust lane at its edge and the diffuse glow of billions of old stars at its center that give this galaxy the appearance of a sombrero. The Sombrero Galaxy was discovered on May 11, 1781 by PiérreMechain.

Saturn rises in the southeast at 10:23 p.m. above the Teapot asterism in Sagittarius. Saturn’s rings are currently titled at 26.5 degrees toward Earth. Saturn’s rings span 21 Earth diameters, or 166,300 miles. As NASA’s Cassini spacecraft travels through the rings at 67,000 mph as part of its Grand Finale, we will receive the closest images ever of Saturn’s rings. The 58% illuminated, waning gibbous Moon rises at 1:28 a.m. Thursday in Capricornus. The Moon reaches its Last Quarter phase at 8:34 Thursday night. Venus rises at 3:44 a.m. in Pisces. Mercury reaches its greatest western elongation at 26 degrees, but the low angle of the ecliptic keeps it too close to the horizon to view.

The Albany Area Amateur Astronomers invite you to join them for their monthly meeting to be held at miSci in Schenectady on Thursday night, May 18th, beginning at 7:30. May’s speaker is Ron Voller, author of The Muleskinner and the Stars: The Life and Times of Milton La Salle Humason, Astronomer (Springer, 2016). The book tells the story of Milton La Salle Humason, part of the team that discovered cosmic expansion in the days of Edwin Hubble. “The story chronicles Humason’s life on Mount Wilson, from his first trip to the mountain to his days as a muleskinner, leading teams of mules hauling supplies to the summit during the construction of the observatory, and follows him through his extraordinary career in spectroscopy, working beside Edwin Hubble as the two helped to reconstruct our concept of the universe.”

Skywatch Line for Monday and Tuesday, May 15th and 16th, 2017

This is the Skywatch Line for Monday and Tuesday, May 15th and 16th.

The Sun sets at 8:11 PM; night falls at 10:11. Dawn breaks at 3:31 AM and ends with the Sun rising at 5:31.

The evening sky contains two planets. First magnitude Mars in Taurus, is moderately low in the western sky, appearing as a tiny red dot, and setting at 10 PM.

Much brighter Jupiter makes its presence known at minus 2 magnitude in Virgo in between the stars Spica and Porrima. In our telescopes and binoculars, it appears as a 42 arc-second ball moderately high in the southern sky. It is best observed at 10:13 PM. Tuesday, telescopic observers can witness the Jovian moon Ganymede disappear behind the planet at 9:05 PM and reappear at 11:27. Wednesday, Jupiter’s moon Europa also vanishes at 2:04 AM and reappears at 2:53. Jupiter sets at 4 AM.

Zero magnitude Saturn rises in Sagittarius at 11:24 PM on Tuesday, is best observed at 3 AM and remains up the rest of the night.

By Midnight, the ninth magnitude comet 41P rises after 9 PM about 7 degrees from the star Nu Herculis. Astronomical magazines and websites provide finder charts.

Tuesday’s waning Moon rises, in Sagittarius, after Midnight. It is 20 days old and appears about 75 percent illuminated and 30 arc-minutes in size. Its minus 10th magnitude will blot out dim distant stars and galaxies. Wednesday’s Moon rises in Capricornus at 12:50 AM and appears a bit less lit and dimmer.

Venus rises in Pisces, at 3:44 AM, glows at minus 4th magnitude and appears about 39 percent lit. Neptune and Mercury accompany the bright planet, but are hidden by lunar glare.

With Venus so prominent in the Dawn sky, let us examine her in detail. Venus is the second planet from the Sun. It is almost an Earth twin – about the same size and slightly less massive. Early telescopic observers noted its complete cloud cover. They speculated that Venus was a lush, tropical planet. As astronomers obtained better instruments, rude shocks came. Venus did not rotate in 24 hours like Earth; its day lasts 243 earth-days. Russian and US probes landed on Venus; pictures showed a rock filled wasteland. Those same probes recorded a toxic atmosphere with true acid rain, causing the probes to die within hours. Since Venus is closer to the Sun, it gets twice the solar radiation. Temperatures approach the melting point of lead and atmospheric pressure is 90 times that of Earth. Its slow rotation and lack of axis tilt means no seasons or weather. Most planetary scientists now think that Venus is a case of uncontrolled global warming. Any oceans boiled off, leaving an atmosphere of 96 percent carbon dioxide. Without oceans, there was no water to capture the carbon dioxide into limestone rocks, as on Earth.

Skywatch Line for Friday, May 12, through Sunday, May 14, 2017

This is Dudley Observatory’s Skywatch Line for Friday, May 12, through Sunday, May 14, written by Sam Salem.

On Friday, Sun rises at 5:36am and sets at 8:09pm; the Waxing Gibbous Moon rises at 9:44pm, reaches transit altitude at 1:57am, and sets at 7:00am.

Venus, at magnitude –4.7, rises due east at 3:52am, on Saturday morning. The “morning star” is bright enough to be seen even after the Sun rises if you know where to look. Jupiter is up before sunset, shining at magnitude -2.4, and reaches the meridian around 10:27pm, on Friday. About 15 minutes later, Saturn, at 0.2 magnitude, climbs to southeast horizon. The ringed planet is at its highest altitude of 25 degrees south around 3:21am, as morning twilight begins to brighten the sky. The waning gibbous Moon makes a triangle with Saturn and the star Antares. Watch for this celestial triangle to illuminate southeast sky by mid-to-late evening. On Saturday evening, the Moon will be positioned roughly 3½ degrees to the left of Saturn as the pair rises together in the southeast. Saturn now shines in front of the constellation Sagittarius, but will cross over into the constellation Ophiuchus after a few more days. Saturn will be considerably closer to Antares on the sky’s dome at the end of its retrograde on August 25.

NASA scientists have called the space between Saturn’s rings “the big empty,” after interpreting readings from the Cassini spacecraft. During the first of its final dives, Cassini revealed the void between the rings is largely dust-free. If the environment were very dusty, scientists would hear dust hitting the spacecraft as a lot of crackling and popping in the readings. However, as Cassini entered the 1,200-mile-wide void, scientists heard very little. Cassini ventured into the space between Saturn’s rings on April 26.

Regulus, in Leo, the Lion, can be split in a small telescope even at low magnification. Its 8.2-magnitude companion lies 176 arc-seconds northwest of the 1.4-magnitude main star. Regulus sets at 2:32am on Saturday morning. Swing your telescope around and aim due north at Polaris, the Pole star. Alpha Ursae Minoris is also a striking double featuring components that span a range of brightness similar to the Regulus twosome. A 9.1 magnitude companion, 18.6 arc-seconds away, accompanies the 2.1 magnitude Pole star.

As evening falls in the month of May, the plane of the pancake-shaped galactic disk of our Milky Way coincides with the plane of the horizon. The Milky Way rims the horizon in every direction at nightfall and early evening, which makes it difficult to see this roadway of stars until later at night. By June, you’ll begin to see the stars of the Summer Triangle, Deneb, Vega, and Altair rising above eastern horizon earlier at night. In a dark country sky, the Milky Way’s band of stars becomes visible as well, for the Milky Way passes right through the Summer Triangle. The Milky Way’s softly glowing band of luminescence hides behind the horizon at nightfall and early evening in the month of May. You’ll begin to see the starlit band of the Milky Way rising in the eastern sky around midnight.

On May 14, 1973, the United States launched its first manned space station “Skylab One”. During the following nine months, three successive crews of astronauts manned the orbiting laboratory. This was the largest payload launched into space. It fell back into and burned up in the Earth’s atmosphere in July 1979.

Skywatch Line for Wednesday, May 10th, and Thursday, May 11th, 2017

This is the Dudley Observatory Skywatch Line for Wednesday, May 10th, and Thursday, May 11th, written by Louis Suarato.

May’s Full Flower Moon occurs at 5:42 p.m., Wednesday. Look for the Moon to rise at 7:52 p.m. in the constellation Libra. Above, and south, of the Moon is Jupiter in the constellation Virgo. Thursday, Jupiter’s moons Io and Europa will cast their shadows on the planet from 9:59 to 10:05 p.m. EDT. The bright star, about 40 degrees above the Moon, is Arcturus. Between the Moon and Arcturus is the globular cluster M5 in the constellation Serpens. Discovered by German astronomer Gottfried Kirch in 1702, M5 is 165 light-years in diameter, making it one of the largest known globular clusters. It is also one of the oldest globular clusters, estimated to have formed 13 billion years ago. M5 is 24,500 light-years away, and may have as many as 500,000 stars. As the Moon is rising, Mars will be setting in the west. Saturn rises at 10:52 p.m. between the constellations Ophiuchus, above, and Sagittarius, below. The open star clusters M23, M24, and M25 form a diagonal line to the left of Saturn. Venus joins Saturn in the early morning sky as it rises in Pisces at 3:55 a.m. Thursday. The Full Moon will be setting as Venus rises.

May 10th is the birth date of astronomer Cecilia Payne. Born in 1900, Payne was the first to apply atomic physics to the study of temperature and density of celestial bodies. Payne was also the first to conclude the universe was mostly composed of the elements hydrogen and helium. At a time when the prevailing theory was the Sun was comprised mostly of iron, Payne’s thesis at Harvard in 1925 stated the Sun was 99% hydrogen and helium, and just 1% iron. Her thesis was mostly ignored until 20 years later when it was confirmed by Fred Hoyle.

Skywatch Line for Monday and Tuesday, May 8th and 9th, 2017

This is the Skywatch Line for Monday and Tuesday, May 8th and 9th.

The Sun sets at 8:04 PM; night falls at 10. Dawn begins at 3:43 AM and ends with sunrise at 5:39.

The Moon and two planets are in this evening’s sky. The nearly full Moon is high in the southeast after sunset. The Moon blazes at minus 12th magnitude on both nights. The Moon is best observed at 11:42 PM on Monday and at 12:26 AM on Wednesday. It remains up past sunrise on both days.

Jupiter, in Virgo, is high in the South and continues a slow westward motion. Jupiter is highest at 10:43 PM on Monday. About that time, the Great Red Spot (a giant storm) is visible to telescopic observers who can also witness the Jovian moon Io begin to cross the planet’s face at 2:47 AM on Wednesday, followed by its shadow at 3:30 AM. Jupiter sets at 4:29 AM.

Mars, in Taurus, is low on the western horizon at civil dusk. The first magnitude planet is a tiny 3.8 arc-seconds in size and sets at 10:05 PM.

Saturn, at zero magnitude, in Sagittarius, rises before 11 PM and is best observed at 3:33 AM. It is one of the few objects to defy the Moon’s glare and remains up the rest of the night.

Civil Dawn sees the rise of two bright planets. Venus, in Pisces, rises first at 3:56 AM. By Civil Dawn, it is about 13 degrees high in the southeast. It is easy to spot, glaring at minus 4.5 magnitude. In telescopes and binoculars, it appears about 33 arc-seconds in size and about one-third illuminated.

First magnitude Mercury, also in Pisces, rises at 4:54 AM and is very low on the eastern horizon. With an unobstructed horizon, the observer will see a 10 arc-second planet, lit about 25 percent.

Since the almost full Moon dominates tonight’s sky, let’s consider our nearest neighbor. Astronomers have long wondered about the Moon’s origin. Before lunar landings, three theories predominated. The first was that the Moon was literally spun off of a rapidly rotating Earth. The second was that the Moon was formed by leftovers from Earth’s formation. The third theorized that a wandering Moon was already formed elsewhere in the Solar System and captured by Earth’s gravity. Due to the Apollo lunar landings, which brought back Moon rocks, a new hypothesis resulted. This theory, supported by Moon rock analysis, states that the Earth was hit by a Mars-sized body, which broke off pieces of Earth. Those pieces formed a temporary ring and later coalesced into the Moon. The Moon’s gravity causes tides on Earth. In fact, in the far distant future, lunar gravity will slow the Earth’s rotation to the point that it will present the same face to the Moon, just as the Moon now shows the same face to Earth.

Skywatch Line for Friday, May 5, through Sunday, May 7, 2017

This is Dudley Observatory’s Skywatch Line for Friday, May 5, through Sunday, May 7, written by Sam Salem.

On Friday, Sun rises at 5:44am and sets at 8:01pm; the Waxing Gibbous Moon reaches transit altitude at 9:30pm and sets at 3:26am the following day.

On Friday night, watch for Eta Aquariid meteors to streak the nighttime from about 3 am until dawn. From our latitude, this is a modest display owing to the meteors radiant low altitude. In addition, this year the bright waxing gibbous Moon will limit the number of meteors you’ll see. Ten in an hour would be a good tally. The best time to look is during the predawn hours of Friday and Saturday when the radiant point, near the star eta Aquarii, is situated due east. The distinctive Y-shaped “Water Jar” pattern of stars in the constellation Aquarius aligns closely with the radiant point of the Eta Aquariid shower. There is a possible connection between Jupiter’s 12-year orbit and the intensity of the Eta Aquariid meteors. The meteors we see are particles shed by Halley’s comet long ago. Every year, as Earth passes through the orbital path of Comet Halley, bits and pieces shed by this comet burn up in the Earth’s atmosphere as Eta Aquariid meteors.

Sunday night, watch for the waxing gibbous Moon to pair up with Jupiter. The Moon and Jupiter are separated by less than 1.5 degrees as evening twilight fades. The star below the Moon and Jupiter is Spica, the brightest star in the constellation Virgo, the Maiden. On Sunday, Jupiter reaches transit altitude of 43 degrees south at 10:48pm and sets at 4:38am the following day. Spica reaches transit altitude of 36 degrees south at 11:17pm and sets at 4:41am the following day.

Saturday marks the birthdate of Willem de Sitter. Born on May 6 1872, the Dutch mathematician, astronomer, and cosmologist developed theoretical models of the universe based on Albert Einstein’s general theory of relativity. He re-determined the fundamental constants of astronomy and determined the variation of the rotation of the earth. He is best known for his contributions to cosmology. His 1917 solution to Albert Einstein’s field equations showed that a near-empty universe would expand. Later, he and Einstein found an expanding universe solution without space curvature.

Skywatch Line for Wednesday, May 3rd, and Thursday, May 4th, 2017

This is the Dudley Observatory Skywatch Line for Wednesday, May 3rd, and Thursday, May 4th, written by Louis Suarato.

The 56 % illuminated, waxing gibbous Moon rises at 12:48 p.m. in the constellation Leo. As the sky darkens, look for Leo’s brightest star, Regulus, 8 degrees to the left of the Moon. At magnitude +1.35, Regulus is the 21st brightest star in the sky. Of all the brightest stars, at .46 degree, Leo is closest to the ecliptic, and frequently occulted by the Moon, and occasionally occulted by Mercury or Venus. Also known as Alpha Leonis, Regulus is a multiple star system comprised of four stars, approximately 79 light-years away. The Moon and Regulus will close to within 4 degrees before setting at 2 a.m. Thursday. Look for M44, the Beehive cluster, between the Moon and the stars Castor and Pollux in Gemini. This week’s visible planets include Mars, which can be seen low in the west-northwest after sunset. At twilight, look for Jupiter about 30 degrees above the southeastern horizon. Saturn rises at 11:21 p.m., to the upper right of the Trifid Nebula, and to the right of the Eagle and Omega nebulae. Venus rises at 4:06 a.m. in Pisces. Look for International Space Station to emerge out of the south-southeast at 5:02 a.m. Thursday. The ISS will travel eastward, passing asclose as 2 degrees of Venus at 5:07. May 4th is the anniversary date of the launching of the Magellan Space Probe aboard Space Shuttle Atlantis. In 1989, Magellan became the first planetary spacecraft to be released from a shuttle in Earth orbit. Magellan arrived at Venus on August 10, 1990, and circled the planet every 3 hours and 15 minutes until October 11, 1994, when it was directed to the surface, collecting data until burning up in Venus’ atmosphere.