The Sky This Week from October 18 to 27 – Astronomy Magazine
An Orionid meteor meets a tall mountain
As morning twilight began October 22, 2015, at Yading National Nature Reserve in the Sichuan Province of China, an Orionid meteor streaked over the sacred Jampayang snow mountain. This pyramidal mountain rises 19,547 feet (5,958 meters) above sea level.
Jeff Dai
Although the Orionid meteor shower peaks this morning, a fat crescent Moon shares the sky and will drown out some of the fainter “shooting stars.” The Orionids typically produce up to 20 meteors per hour, but the Moon’s presence likely will cut that number in half. Your best bet is to find an observing site where you can place the Moon behind a building or trees. Orionid meteors appear to radiate from the northern part of the constellation Orion the Hunter.
The variable star Algol in Perseus reaches minimum brightness around 11:04 p.m. EDT, when it shines at magnitude 3.4. If you start tracking it this evening, you can watch it more than triple in brightness (to magnitude 2.1) by dawn. 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 2 a.m. local daylight time.
Wednesday, October 23
Jupiter continues to dominate the early evening sky from its perch in southern Ophiuchus the Serpent-bearer. The giant planet shines at magnitude –1.9 and stands 15° above the southwestern horizon an hour after sunset. When viewed through a telescope, Jupiter shows a 34″-diameter disk with striking details in its dynamic atmosphere. You also should see four bright points of light arrayed around the planet: the Galilean moons Io, Europa, Ganymede, and Callisto.
Thursday, October 24
Neptune appeared at its best at opposition in September, but its visibility hardly suffers in October. The outermost major planet lies some 35° above the southeastern horizon once darkness falls and climbs highest in the south around 10 p.m. local daylight time. Neptune glows at magnitude 7.8, which is bright enough to spot through binoculars if you know where to look. The trick is to find the 4th-magnitude star Phi (φ) Aquarii, which lies about 15° (two binocular fields) east-southeast of Aquarius’ distinctive Water Jar asterism. Tonight, Neptune appears 1.2° west-southwest of Phi. When viewed through a telescope, the ice giant planet shows a blue-gray disk measuring 2.3″ across. To learn more about viewing Neptune and its outer solar system cousin, Uranus (which reaches opposition at the end of this week), see “Observe the ice giants” in October’s Astronomy.
Friday, October 25
Look high in the southeast 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 26
Saturn remains a glorious sight this week. The ringed planet resides among the background stars of Sagittarius the Archer, a region that appears 25° high in the south-southwest as twilight fades to darkness and doesn’t set until close to 10:30 p.m. local daylight time. Saturn shines at magnitude 0.5 and appears significantly brighter than any of its host constellation’s stars. Although a naked-eye view of the planet is nice, seeing it through a telescope truly inspires. Even a small instrument shows the distant world’s 16″-diameter disk and spectacular ring system, which spans 37″ and tilts 25° to our line of sight.
The Moon reaches perigee, the closest point in its orbit around Earth, at 6:39 a.m. EDT. It then lies 224,508 miles (361,311 kilometers) away from us.
