Dudley Observatory Skywatch Line for Friday, April 15, through Sunday, April 17, 2016

This is Dudley Observatory’s Skywatch Line for Friday, April 15, through Sunday, April 17, written by Sam Salem.

On Friday, the Sun rises at 6:15am and sets at 7:39pm. Look for the waxing gibbous Moon with 65% of its visible disk illuminated on Friday, increasing to 74% on Saturday, and 82% on Sunday night. The Moon sets at 2:58 am on Friday, 3:34 am on Saturday, 4:06 am on Sunday, and 4:36 am on Monday.

On Friday evening, the Moon forms a curving row with Regulus to its left and then Jupiter.  Look above the Moon after dusk, on Saturday, for Regulus, the bottom of the now-vertical Sickle of Leo.  Regulus is the brightest star in the constellation Leo.  On Sunday, watch as the Moon pays a visit to the brightest planet of the night, Jupiter, as both rise in the southern sky.

Mars begins its retrograde motion westward in the sky, on Sunday.  Mars will continue its backward march until June 30.  For a couple of months every two years, Mars changes the direction of its motion against the backdrop of fixed stars. This apparent reversal is due to the fact that Earth is orbiting closer to the sun than Mars and is moving faster on its orbital track. That means our planet periodically passes Mars, creating the illusion that it has changed course. Seen from Mars, Earth appears to be in retrograde during this time.

Mid-April Mars is 63,236,776 miles away from Earth.  Now is the time to start exploring Mars through the telescope.  It blazes highest in the south before the first light of dawn, to the right of dimmer Saturn and above Antares.  In a telescope Mars grows this week from 13 to 14 arc-seconds in diameter.   By the time of its opposition and closest approach in late May, Mars will triple in brightness and grow to 18.8 arc-seconds wide.

Saturn is also moving retrograde but at much slower speed than Mars.  The pair moves apart from each other then start to converge and pass each other on August 25.

By early dawn, Saturn and Mars stand in the south-southwest.  Saturn, Mars, and Antares form a triangle.  Saturn stands on the left, Mars stands on the right, and the fainter, Mars-colored Antares stands beneath Mars.  Antares is the brightest star in the constellation Scorpius.  It is often referred to as “the heart of the scorpion”.  Along with Aldebaran, Regulus, and Fomalhut, Antares comprises the group known as the “Royal Stars of Persia”.   They were regarded as the guardians of the sky during the time of the Ancient Persians.  Persians believed that the sky was divided into four districts with each district being guarded by one of the four Royal Stars.

Skywatch Line For Wednesday, April 6th and Thursday, April 7th, 2016

This is the Dudley Observatory Skywatch Line For Wednesday, April 6th and Thursday, April 7th written by Louis Suarato

Wednesday, just after sunset, you may be able to see Mercury about 10 degrees above the western horizon. Mercury will become more visible after its trek around the Sun, and now in the evening sky. After Mercury sets, the Pleiades star cluster sinks into the western horizon. In the east, Virgo is the first constellation to rise after sunset. You’ll find Jupiter above Virgo,and about 50 degrees above the southeastern horizon. A telescopic view of Jupiter will reveal its moon, Io, crossing the face of the planet from 9:52 p.m. to 12:07 a.m. Thursday. Io’s shadow follows its source from 10:32 p.m. to 12:47 a.m.,Thursday. Europa, the smallest of the Galilean satellites, and sixth largest moon in the solar system, hides behind Jupiter at 10:48 p.m.

Mars rises in Scorpius at 11:40 p.m., Wednesday, followed by Saturn at 15 minutes at past midnight. The red and ringed planets are separated by about 8.5 degrees. Watch Mars’ magnitude, and apparent size through a telescope, increase, as it approaches opposition in May. Saturn will reach opposition in June. Mars and Saturn form a triangle with Scorpius’ brightest star, Antares. To the upper right of Antares, you’ll find the globular cluster, M4. Discovered by Philippe Loys de Chéseaux in 1746 and catalogued by Charles Messier in 1764,M4 is approximately 7,200 light-years away. M4 contains some the earliest stars, some aged at 13 billion years, about 820 billion years after the origin of the universe.

The New Moon occurs at 7:24 a.m. Thursday. Lunar perigee occurs 6 hours later at 1:36 p.m., when the Moon will be 221,931 miles from Earth. Expect higher, and lower than normal tides during this time.

The Albany Area Amateur Astronomers will be hosting a star party at Grafton Lakes State Park this Friday. If Friday night’s event is cancelled, it will be rescheduled for Saturday night. This weekend is also the time for the annual Northeast Astronomy Forum (NEAF), held at Rockland Community College. A wealth of knowledge can be obtained from experts and vendors about telescopes and related equipment. It would be a good opportunity to obtain a Sun-safe filter or telescope to view the transit of Mercury on May 9th.

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.