Page 43 - Astronomy - October 2017 USA

Morning planets greet the Moon LOCATINGASTEROIDS

Keep an eye on Iris

The space between the orbits Iris lies within one binocular
of Mars and Jupiter is packed field of Aries the Ram’s bright-
with hundreds of thousands of est star — magnitude 2.0
small bodies known as aster- Hamal (Alpha [α] Arietis) — all
oids. Only a handful of these month. This area stands high in
objects are big enough and the east by midevening. Simply
come close enough to Earth to walk outside, dark adapt for
show up easily through binocu- five minutes, and then focus in
lars. Fortunately, October’s sky on Hamal.
features a fine specimen of this The easiest time to find Iris
rare breed. comes during October’s final
Asteroid 7 Iris ranks second week, when it shines brightest
only to 4 Vesta as the brightest and slides 1.7° due south of
asteroid of 2017. Iris glows at Hamal and 1.0° due south of
Venus appears 0.2° from Mars on October 5. On the 17th, a crescent Moon
magnitude 6.9 when it reaches magnitude 5.0 Kappa (κ) Ari. To
joins the two, mirroring this scene from January 31, 2017. MATTHEW DIETERICH
opposition and peak visibility confirm a sighting, sketch the
late this month. Eagle-eyed field with Alpha, Kappa, and
Omicron (ο) Piscium and ends 4th-magnitude star Sigma (σ)
observers under pitch-black several of the stars near the
the month 2.2° due west of this Leonis 0.3° north of Venus. skies might be able to glimpse asteroid’s position plotted
star. Once you locate Uranus Unfortunately, a telescope
it with their naked eye, but below. Return a night or two
through binoculars, set them doesn’t add much. Venus even newcomers should have later and identify the point of
aside and try to spot the planet spans 11" while Mars mea- little trouble finding it through light that changed position.
with your naked eye. You sures 4" across, and both binoculars from the suburbs. That “star” is Iris.
should be able to from under appear nearly full.
a dark sky. A telescope reveals The two planets move Iris butts the Ram’s head
Uranus’ 3.7"-diameter disk and eastward relative to the back-
impressive blue-green color. ground stars during October, N
The telescopic view should with Venus in its inner orbit
be especially good this month moving faster. It crosses the
because Uranus appears so border into Virgo on the 9th, Oct 1 _
high. From mid-northern lati- setting up a string of close stel- 6
tudes on the night of opposi- lar conjunctions. The bright 11 Path of Iris g
tion, the planet lies 60° above planet passes 0.8° northeast E 16
the southern horizon at its of 4th-magnitude Beta (β)
21
peak around 1 a.m. local day- Virginis on October 12,
light time. This is the highest 0.2° north of 4th-magnitude
26
it has appeared at opposition Eta (η) Vir on the 18th, 1.3°
since February 1963. southwest of 3rd-magnitude ARIES d 31
By the time twilight starts Gamma (γ) Vir on the
to paint the morning sky, 22nd, and 0.3° south of 4th- 0.5°
Uranus dips low in the west. magnitude Theta Vir on the
The action then shifts to the 29th. By the 31st, Venus stands This 7th-magnitude asteroid should be easy to find as it slides south of
eastern sky, where Venus and 16° east of Mars. 2nd-magnitude Alpha (α) Arietis, the brightest star in Aries the Ram.
Mars put on a marvelous show. The Red Planet runs a sim-
On October 1, they appear 2.5° ilar gauntlet, but at a slower
apart against the background pace. It crosses into Virgo on But the most spectacular appears only 2 percent illu-
stars of Leo. Magnitude –3.9 October 12 before sliding 0.5° conjunction takes place when minated and 6° to Venus’
Venus rises 13 minutes before north of Beta Vir on the 18th. the waning crescent Moon lower left.
magnitude 1.8 Mars. On the 30th, it lies 0.3° south- passes the two planets just
The gap between the two west of Eta Vir and nearly on after midmonth. On October Martin Ratcliffe provides plane-
closes until October 5, when top of 6th-magnitude 13 Vir. 17, the 5-percent-lit crescent tarium development for Sky-Skan,
just 0.2° — about half the Full As twilight begins on the East Moon stands 2° to Mars’ left Inc., from his home in Wichita,
Moon’s diameter — separates Coast, they lie just 44" apart; and 6° above Venus. Our satel- Kansas. Meteorologist Alister
them. The two haven’t been this from the West Coast, 4.2' sep- lite is much harder to see the Ling works for Environment
close since November 1995. If arate the two. following morning, when it Canada in Edmonton, Alberta.
you view the pair through bin-
GET DAILY UPDATES ON YOUR NIGHT SKY AT www.Astronomy.com/skythisweek.
oculars, you’ll also notice the
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