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- The Sky this Week: October 9-18, 2015
The Sky this Week: October 9-18, 2015
Your daily digest of celestial events coming soon to a sky near you.
By Richard Talcott | Published: Friday, October 9, 2015
Friday, October 9
Look high in the east after darkness falls this week and you should see autumn’s most conspicuous star group. The Great Square of Pegasus stands out in the evening sky at this time of year, though it appears balanced on one corner and looks more diamond-shaped. These four almost equally bright stars form the body of Pegasus the Winged Horse. The fainter stars that form the rest of this constellation’s shape trail off to the square’s west.
Look high in the east after darkness falls this week and you should see autumn’s most conspicuous star group. The Great Square of Pegasus stands out in the evening sky at this time of year, though it appears balanced on one corner and looks more diamond-shaped. These four almost equally bright stars form the body of Pegasus the Winged Horse. The fainter stars that form the rest of this constellation’s shape trail off to the square’s west.
Saturday, October 10
The predawn sky glitters with a trio of bright planets this week. Venus, Mars, and Jupiter all lie against the background stars of Leo the Lion with 12° separating them this morning. The first to rise is brilliant Venus, which shines at magnitude –4.6 and pokes above the eastern horizon by 3:30 a.m. local daylight time. Roughly a half-hour later, the ruddy light of magnitude 1.8 Mars comes into view. And then, 15 minutes after that, magnitude –1.7 Jupiter rises. A half-hour after Jupiter comes up, a 6-percent-lit crescent Moon climbs above the horizon. All these objects are up well before morning twilight starts to paint the sky. When viewed through a telescope, Venus spans 29" and appears about 40 percent lit while Jupiter measures 32" across and is fully illuminated. Unfortunately, Mars shows little detail on its 4"-diameter disk.
The predawn sky glitters with a trio of bright planets this week. Venus, Mars, and Jupiter all lie against the background stars of Leo the Lion with 12° separating them this morning. The first to rise is brilliant Venus, which shines at magnitude –4.6 and pokes above the eastern horizon by 3:30 a.m. local daylight time. Roughly a half-hour later, the ruddy light of magnitude 1.8 Mars comes into view. And then, 15 minutes after that, magnitude –1.7 Jupiter rises. A half-hour after Jupiter comes up, a 6-percent-lit crescent Moon climbs above the horizon. All these objects are up well before morning twilight starts to paint the sky. When viewed through a telescope, Venus spans 29" and appears about 40 percent lit while Jupiter measures 32" across and is fully illuminated. Unfortunately, Mars shows little detail on its 4"-diameter disk.
Methane in Uranus’ atmosphere absorbs red light, giving the planet a distinctive bluish hue through amateur instruments. This Keck Telescope image also records atmospheric structure and a faint ring.
Lawrence Sromovsky (University of Wisconsin)/W. M. Keck Observatory
Sunday, October 11
Uranus reaches opposition and peak visibility tonight. Opposition officially arrives at midnight EDT, when the outer planet lies opposite the Sun in our sky. This means it rises at sunset, climbs highest in the south around 1 a.m. local daylight time, and sets at sunrise. The magnitude 5.7 planet lies in southern Pisces in the same binocular field as the 5th-magnitude star Zeta (z) Piscium. Although Uranus shines brightly enough to glimpse with the naked eye under a dark sky, use binoculars to locate it initially. A telescope reveals the planet’s blue-green disk, which spans 3.7".
Uranus reaches opposition and peak visibility tonight. Opposition officially arrives at midnight EDT, when the outer planet lies opposite the Sun in our sky. This means it rises at sunset, climbs highest in the south around 1 a.m. local daylight time, and sets at sunrise. The magnitude 5.7 planet lies in southern Pisces in the same binocular field as the 5th-magnitude star Zeta (z) Piscium. Although Uranus shines brightly enough to glimpse with the naked eye under a dark sky, use binoculars to locate it initially. A telescope reveals the planet’s blue-green disk, which spans 3.7".
The Moon has one final hurrah this morning before it disappears into the Sun’s glare. The waning crescent, now just 2 percent lit, slides within 1° of Mercury. The pair rises some 80 minutes before the Sun and climbs more than 5° above the horizon 45 minutes ahead of sunrise. Mercury shines at magnitude 0.2 and should stand out in the twilight through binoculars. Later this week, the innermost planet puts on its best morning display of 2015.
The Moon reaches apogee, the farthest point in its orbit around Earth, at 9:18 a.m. EDT. It then lies 252,518 miles (406,388 kilometers) from Earth’s center.
Monday, October 12
The variable star Algol in Perseus reaches minimum brightness around 11:02 p.m. EDT, when it shines at magnitude 3.4. Over the next few hours, you can watch it more than triple in brightness, to magnitude 2.1. This eclipsing binary star runs through a cycle from minimum to maximum and back every 2.87 days. Algol remains visible all night, passing nearly overhead around 3 a.m. local daylight time.
The variable star Algol in Perseus reaches minimum brightness around 11:02 p.m. EDT, when it shines at magnitude 3.4. Over the next few hours, you can watch it more than triple in brightness, to magnitude 2.1. This eclipsing binary star runs through a cycle from minimum to maximum and back every 2.87 days. Algol remains visible all night, passing nearly overhead around 3 a.m. local daylight time.
New Moon occurs at 8:06 p.m. EDT. At its new phase, the Moon crosses the sky with the Sun and so remains hidden in our star’s glare.
Under a dark sky, you can spot the ethereal zodiacal light before dawn this week.
ESO/Y. Beletsky
Tuesday, October 13
The Moon’s absence from the morning sky these next two weeks provides observers with an excellent opportunity to view the zodiacal light. From the Northern Hemisphere, the time around the autumnal equinox (which occurred three weeks ago) is the best for viewing the elusive glow before sunrise. It appears slightly fainter than the Milky Way, so you’ll need a clear moonless sky and an observing site located far from the city. Look for a cone-shaped glow that points nearly straight up from the eastern horizon shortly before morning twilight begins (around 5:30 a.m. local daylight time at mid-northern latitudes). The Moon remains out of the morning sky until October 26, when the waxing gibbous returns and overwhelms the much fainter zodiacal light.
The Moon’s absence from the morning sky these next two weeks provides observers with an excellent opportunity to view the zodiacal light. From the Northern Hemisphere, the time around the autumnal equinox (which occurred three weeks ago) is the best for viewing the elusive glow before sunrise. It appears slightly fainter than the Milky Way, so you’ll need a clear moonless sky and an observing site located far from the city. Look for a cone-shaped glow that points nearly straight up from the eastern horizon shortly before morning twilight begins (around 5:30 a.m. local daylight time at mid-northern latitudes). The Moon remains out of the morning sky until October 26, when the waxing gibbous returns and overwhelms the much fainter zodiacal light.
Wednesday, October 14
Asteroid 4 Vesta reached opposition two weeks ago and remains an easy target throughout October. Although the minor planet is barely bright enough to see with the naked eye from under a dark sky (it shines at magnitude 6.5), binoculars or a telescope will make the task of finding it much easier. Vesta lies in the constellation Cetus the Whale. To find it, first locate 2nd-magnitude Beta (b) Ceti and then point your binoculars 10° to the north-northwest at magnitude 3.5 Iota (i) Ceti. Vesta is the brightest object southeast of Iota.
Asteroid 4 Vesta reached opposition two weeks ago and remains an easy target throughout October. Although the minor planet is barely bright enough to see with the naked eye from under a dark sky (it shines at magnitude 6.5), binoculars or a telescope will make the task of finding it much easier. Vesta lies in the constellation Cetus the Whale. To find it, first locate 2nd-magnitude Beta (b) Ceti and then point your binoculars 10° to the north-northwest at magnitude 3.5 Iota (i) Ceti. Vesta is the brightest object southeast of Iota.
Leo the Lion’s head offers several bright guide stars to steer you toward the active comet currently under surveillance by the Rosetta spacecraft.
Thursday, October 15
Mercury is now in the midst of its finest morning apparition of 2015. The planet reaches greatest elongation today, lying 18° west of the Sun and appearing 8° high in the east 45 minutes before sunrise. The inner world shines at magnitude –0.6, which is bright enough to see clearly with the naked eye. Binoculars can help you to pick it out of the twilight glow if you can’t spot it immediately. When viewed through a telescope, Mercury’s 7"-diameter disk appears half-lit.
Mercury is now in the midst of its finest morning apparition of 2015. The planet reaches greatest elongation today, lying 18° west of the Sun and appearing 8° high in the east 45 minutes before sunrise. The inner world shines at magnitude –0.6, which is bright enough to see clearly with the naked eye. Binoculars can help you to pick it out of the twilight glow if you can’t spot it immediately. When viewed through a telescope, Mercury’s 7"-diameter disk appears half-lit.
The European Space Agency’s Rosetta probe continues to study Comet 67P/Churyumov-Gerasimenko from up close, revealing stunning detail on the two-lobed object. For observers on Earth, mid-October provides perhaps the best chance to view this comet from afar. The comet lies in the morning sky among the background stars of Leo, not far from the trio of morning planets. Glowing around 11th magnitude, 67P should show up through an 8-inch telescope. The search will be particularly easy this morning, when the comet passes just 16' north of magnitude 3.5 Eta (h) Leonis.
Friday, October 16
The days of viewing Saturn in the evening sky are dwindling rapidly. You can find the ringed world about 10° above the southwestern horizon an hour after sundown all week, though the task is easier tonight because it hangs just a few degrees to the lower right of a thin crescent Moon. At magnitude 0.6, the planet stands out nicely against the twilight sky. A telescope still delivers decent views of Saturn’s ring system, which spans 35" and tilts 25° to our line of sight.
The days of viewing Saturn in the evening sky are dwindling rapidly. You can find the ringed world about 10° above the southwestern horizon an hour after sundown all week, though the task is easier tonight because it hangs just a few degrees to the lower right of a thin crescent Moon. At magnitude 0.6, the planet stands out nicely against the twilight sky. A telescope still delivers decent views of Saturn’s ring system, which spans 35" and tilts 25° to our line of sight.
On the evening of June 17, 1991, Venus gleamed above Jupiter while fainter Mars shone to their left. The same three planets converge in October’s morning sky.
Alan Dyer
Saturday, October 17
The stunning group of predawn planets takes on added luster this morning as Mars passes less than a Full Moon’s width north of Jupiter. Venus lies 6.7° west of the pair and is closing rapidly, setting the stage for a spectacular series of morning vistas during October’s final two weeks.
The stunning group of predawn planets takes on added luster this morning as Mars passes less than a Full Moon’s width north of Jupiter. Venus lies 6.7° west of the pair and is closing rapidly, setting the stage for a spectacular series of morning vistas during October’s final two weeks.
Sunday, October 18
The annual Orionid meteor shower is quickly ramping up toward its peak the night of October 21/22. You already should be seeing several shower members in the dark predawn sky. To tell an Orionid from a sporadic meteor, trace the path of the “shooting star” backward. An Orionid meteor will appear to radiate from the northern part of the constellation Orion the Hunter.
The annual Orionid meteor shower is quickly ramping up toward its peak the night of October 21/22. You already should be seeing several shower members in the dark predawn sky. To tell an Orionid from a sporadic meteor, trace the path of the “shooting star” backward. An Orionid meteor will appear to radiate from the northern part of the constellation Orion the Hunter.
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