Alan MacRobert
SkyandTelescope.com July 2014 51
Learn how to use detailed star charts to fi nd the faintest things with your telescope: skypub.com/charts.
live near 40°° north latitude.
Mars and Spica are your naked-eye starting points, as
shown on the wide-fi eld chart at left. Mars and Spica are
14 ° apart on American evening of June 1st, 5½° on July
1st, and 1.3° on July 13th, their own date of least angular
separation (appulse).
Quite near the two asteroids on the sky, though utterly
invisible from Earth, is NASA’s Dawn spacecraft. It’s
en route from its successful 2011–12 mission at Vesta to
its next mapping project at Ceres, where it will take up
permanent orbit in spring 2015.
Although the two asteroids look close together, they
June 26
27
28
29
30
July
1 2 3 4 5 6 7 8 9
10
June
26
27
28
29
30
July
1 2 3 4 5 6 7 8 9
10
c
VIRGO
Pa
th
o
f^ V
es
P ta
at
h^
of
C
er
es
13 h 36 m 13 h 32 m 13 h 28 m 13 h 24 m
–2°
–1°
Star magnitudes
4 5 6 7 8 9
10
11
Vesta is 7th magnitude and Ceres is 8th as
they swing together near Mars and Spica. The
date ticks are plotted for 0:00 Universal Time.
Interpolate to put a pencil mark on each of the
paths for the date and time you plan to look.
Opposite page: Stars are plotted to magnitude
9.0 and galaxies (in the Virgo Cluster) to 11.5.
Third-magnitude Gamma (γ) Virginis is an equal
double star with a current separation of 2.1′′.
The black rectangle shows the area of the close-
up chart on this page.
Ceres and Vesta Paired
Date (0 mag. mag.h UT) Ceres Vesta Separation
May 1 7.2 6.0 2.6°
June 1 7.8 6.6 2.1°
July 1 8.4 7.1 0.4°
Aug. 1 8.8 7.4 2.2°
Sept. 1 9.0 7.7 5.0°
Ceres
mag.
- 2
- 8
8.4 - 8
9.0
Separation
- 6 °°
2.1°° - 4 °°
2.2°° - 0 °°
JULY METEORS
Several minor, long-lasting meteor showers with radi-
ants in the southern sky are active in July, including the
Alpha Capricornids, Piscis Austrinids, and Delta Aquari-
ids. Together they increase the chance that a meteor you
see late on a July night will be fl ying out of the south.
On the morning of July 19th, the faint asteroid
611 Valeria will black out an 8.7-magnitude star in
Pisces for up to 4 seconds as seen from a track
predicted to cross northern Mexico, Texas, the
Deep South (including the Atlanta area), and the
Carolinas. The occultation will happen within
a couple minutes of 9:10 UT in Texas and 9:12
UT in the Carolinas, where dawn will be getting
under way.
For a map, fi nder charts, more about asteroid
occultations, and additional predictions, see
skypub.com/july2014asteroidoccultation.
Asteroid Occultation
are not. Ceres is a good 46 million miles (74 million km)
in the background of Vesta around their appulse date.
That’s part of the reason why Ceres looks fainter. Ceres,
with a diameter of 585 miles (940 km), is actually almost
twice as large as Vesta. But it’s farther from the Sun as
well as from Earth, and it has much darker surface mate-
rial. Vesta is medium-gray, refl ecting 42% of the sunlight
striking it (a high albedo for an asteroid), whereas Ceres
is a more typical dark gray-brown with an albedo of only
9%. But patchy brighter and darker markings on Ceres,
revealed in Hubble images, hint of interesting landscapes
awaiting Dawn.
DAVID MAYHEW