Astronomy - February 2014

PERSEUS

CAMELOPARDALIS

1

4

2

3

Path of Comet ISON

Feb 1

4

7

10

13

NGC 1545

NGC 1528

h

1°

N

E

Comet ISON (C/2012 S1)

February 24, 9:30 P.M. EST 1'

Jupiter

Callisto

Io

Europa

Ganymede

S

W

Jupiter’s moons line up in order

42 ASTRONOMY t FEBRUARY 2014

along its orbit. The moon
moves behind Jupiter starting
at 8:56 p.m. EST. Exactly three
hours later, Io returns to view
as it exits Jupiter’s shadow 13"
from Jupiter’s eastern limb. It
takes this satellite three min-
utes to fully brighten.
Jupiter’s outermost major
moon, Callisto, transits Jupi-
ter on February 5 starting at
9:10 p.m. EST. Because Callisto
travels a wider orbit than Io, it
moves more slowly and takes
longer to cross Jupiter’s disk.
The transit doesn’t wrap up
until 12:34 a.m. It’s worth
staying up even later to see
Europa transit Jupiter. This
event begins at 3:53 a.m. EST;

12 minutes later, a large

shadow appears on the jovian

cloud tops. Don’t be fooled

— this is Callisto’s shadow,

not Europa’s. The outer

moon’s shadow trails its own

disk by seven hours.

You’ll have to wait until

late evening to view another

planet. Mars rises shortly after

11 p.m. local time in early Feb-

ruary and some 90 minutes

earlier by month’s end. On the

1st, the Red Planet stands 5°

north-northeast of blue-white

Spica, Virgo the Maiden’s

brightest star. At magnitude

0.2, Mars appears twice as

bright as 1st-magnitude Spica.

The planet’s slow easterly

motion carries it to a point

some 6° northeast of Spica by

February 28. Mars then shines

at magnitude –0.4 and bests

Spica by a factor of 3.6.

The planet’s rapid bright-

ening signals that it will soon

be making a close approach to

Earth. In early April, Mars

will appear brighter than at

any time since 2007 as it

reaches opposition and peak

visibility. The planet’s appar-

ent diameter also grows larger

as opposition looms. When

viewed through a telescope in

early February, it spans 8.9";

the disk swells by 30 percent

(to 11.5") by month’s close.

Eight-inch and larger scopes

should provide nice views of

martian surface features.

Plan to view Mars in the

early morning when it climbs

nearly halfway to the zenith in

the southern sky. Peak eleva-

tion comes around 5 a.m.

local time in early February

and shortly after 3 a.m. late in

the month. If you observe the

planet at the same time each

night, features slowly change

position because Mars takes

24 hours and 37 minutes to

complete a rotation.

The giant volcano Olym-

pus Mons lies near the mar-

tian disk’s center during

COMETSEARCH

As Comet ISON (C/2012 S1)

begins a long goodbye as it

departs from the inner solar

system in February, it should

remain a telescopic treat in the

rich star fields of the Perseus

Milky Way. After the waxing

Moon sets during the first 10

days of February, a 4-inch tele-

scope under a dark sky should

pull in the diffuse comet. From

the suburbs, however, the

comet may remain a disappoint-

ing smudge even through an

8-inch instrument. In the second

half of February, the Moon-free

observing window moves to

the evening sky as the celestial

visitor fades.

ISON should be fairly easy to

track down. It lies roughly mid-

way between brilliant Capella

(Alpha [α] Aurigae) and bright

Mirfak (Alpha Persei), drifting

near a crumpled box of stars

that represents the curled hand

of Perseus the Hero. Take a few

minutes to enjoy the open star

clusters NGC 1545 and NGC

1528. The former is smaller and
      looks like a dancing stick man,
      while the latter is a beautiful
      large group visible through
      finder scopes and binoculars.
      At low power, you might
      notice that ISON doesn’t appear
      like a typical round cotton ball.
      Bump up the power to 100x or
      more and take a closer look.
      Picture a slice of thin-crust pizza
      oriented almost edge-on with
      the point close to your nose.
      The comet’s coma (the point)
      should glow brightest with well-
      defined wings on each side. The
      fan-shaped dust tail (the pizza
      “toppings”) spans a broad angle
      but peters out quickly to the

north because of our shallow

observing angle.

Next month, we will leave

ISON behind and pick up a fresh

comet: PANSTARRS (C/2012 K1).

This dirty snowball promises to

be a nice target from now until

autumn. Meanwhile, we’ll leave

ISON’s retreat to imagers and

observers with large scopes.

ISON starts its trek back to the Oort Cloud

EVENING SKY MIDNIGHT MORNING SKY
Mercury (west) Mars (southeast) Mercury (southeast)
Jupiter (east) Jupiter (west) Venus (southeast)
Uranus (west) Mars (southwest)
Neptune (west) Saturn (south)

WHEN TO VIEW THE PLANETS

— Continued from page 37

The bright comet of November and December dims considerably as it moves

from Camelopardalis into Perseus in early February. ASTRONOMY: ROEN KELLY

The apparent distances from Jupiter of the four Galilean moons often don’t

match their orbital hierarchy, but they do February 24. ASTRONOMY: R O EN K EL LY