Page 42 - Astronomy - October 2017 USA

— Continued from page 37
Watch a star disappear
WHEN TO VIEW THE PLANETS N
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EVENING SKY MIDNIGHT MORNING SKY
Mercury (southwest) Uranus (southeast) Venus (east)
Jupiter (west) Neptune (southwest) Mars (east)
Saturn (southwest) Uranus (west)
Uranus (east) h
Neptune (southeast)
E
4U 410-143659
Aquarii. Neptune appears 0.6° passes directly in front of a
east-southeast of Lambda on star. Viewers in the northeast- Neptune
October 1 and the same dis- ern United States and eastern
tance due south of the star Canada can view this rare
on the 31st. occultation on the evening of AQUARIUS
You should be able to iden- the 5th; those in the United
tify Neptune from its position Kingdom, western Europe, 0.2°
because no star in the immedi- and northwestern Africa can Neptune’s moon Triton slides in front of 12th-magnitude 4U 410-143659
ate area shines as brightly. But witness it on the morning of the night of October 5/6. The star will dim visibly for up to 161 seconds.
you can remove any doubt by the 6th. A 6-inch scope will
pointing a telescope in its show the event. and 24h00m UT), depending bright as possible. But the
direction. Only the planet The magnitude 12.4 star, on their location. The finder appearance of an outer planet
shows a discernible disk, which cataloged as 4U 410-143659, chart above pinpoints the star. changes slowly, and Uranus
has a diameter of 2.3" and a dims by 1.4 magnitudes as the Uranus reaches opposition maintains its magnitude 5.7
distinctive blue-gray color. magnitude 13.5 moon occults October 19. It then lies directly peak throughout October.
Keep your scope handy for it. Viewers will see the star opposite the Sun in our sky, so The ice giant lies among
Neptune’s event of the month: disappear for up to 161 sec- it remains visible all night. It the background stars of
On the night of October 5/6, onds sometime between 7:44 also lies closest to Earth at Pisces. It starts the month 1.3°
the planet’s big moon, Triton, and 8:00 p.m. EDT (23h44m opposition, rendering it as northwest of magnitude 4.3

COMETSEARCH

The Pleiades adds a sister Comet PANSTARRS (C/2015 ER61)

N
For the past two months, Comet should be ideal. PANSTARRS
PANSTARRS (C/2015 ER61) has then appears some 30° above Pleiades
been floating near the Pleiades the eastern horizon at 11 P.M.
star cluster (M45), or Seven local daylight time.
Sisters, in northwestern Taurus. Apart from sharing the same
They remain neighbors during area of sky, the comet and E
October, though PANSTARRS’ Pleiades showcase a common Oct 1 Path of ARIES
Comet PANSTARRS
slow westward motion carries it phenomenon of physics: light 6
into eastern Aries by the month’s scattering (or reflecting) off 11
final week. The solar system dust. Comet dust arises when 16 o
object should glow around 11th sunlight turns the ices on the 21
TAURUS
magnitude as it heads back body’s nucleus directly into a
26
toward the distant Oort Cloud gas, and carries dust away in the
from which it came. That bright- process. These particles form a 31
1°
ness pushes the limits of a shroud around the nucleus that
4-inch telescope under a dark appears yellow because it This visitor from the distant Oort Cloud should glow at 11th magnitude
sky, but should pose little prob- reflects sunlight. Far in the back- in October as it gradually moves away from the Pleiades star cluster.
lem through an 8-inch or larger ground, the Pleiades’ stars are
instrument. plowing through a cloud of cos- dust production is dropping the center. The comet’s small
You’ll want to avoid viewing mic dust. These particles scatter with each passing night. size and low surface brightness
during October’s first 10 days, the blue light radiated by the Through most telescopes, it mean you might not see this
when a bright Moon shares the cluster’s many hot, young stars. likely will look like an unimpres- structure at first under low
evening sky. The two-week win- As Comet PANSTARRS moves sive elliptical galaxy — mostly power, but at 120x or more, it
dow of dark skies that follows steadily away from the Sun, its round and a bit brighter toward should show quite nicely.

42 ASTRONOMY • OCTOBER 2017