Australian Sky & Telescope - June 2018

58 AUSTRALIAN SKY & TELESCOPE July 2018

M8

M16

M17

M18

M20

M21

M22

M23

M24 Star Cloud

M25

M28

May

1

22 June

5 19 July 3 17 31 Aug 14

May 1

8

15

22

29

June 5

12

19

26

July 3

10

17 24

31

Aug 7

14

21

28

Sept 4

a

h

+

e

j

j

SERPENS CAUDA

SAGITTARIUS

OPHIUCHUS

Path of Vesta

Path of Saturn

18 h 40 m 18 h 30 m 18 h 20 m 18 h 10 m 18 h 00 m 17 h 50 m 17 h 40 m 17 h 30 m 17 h 20 m

–14°

–16°

–18°

–20°

–22°

–24°

M9

Star magnitudes

2 3 4 5 6 7

TVesta’spositionismarkedwithatickat

0 hUT every seven days.

VESTA: NASA / JPL-CALTECH / UCLA / MPS / DLR / IDA

VESTA’S OPPOSITION by S. N. Johnson-Roehr

See Vesta

at its best

Asteroid 4 Vesta is nice and close,

a lustrous light in the southern sky.

V

esta, the fourth-discovered

asteroid, reaches opposition

(opposite the Sun in the sky

when viewed from Earth) on June 19.

Though neither the largest nor the most

massive of the main belt asteroids,

Vesta is the brightest of them all when

it is at opposition. This year it shines in

Sagittarius at magnitude 5.3 and will

be visible without optical aid under

reasonably dark skies. It’ll be a bit

dimmer for the rest of June and into

July, ranging from magnitude 5.6 to 5.9,

but still within reach of the naked eye

under good skies.

There’s something intrinsically

interesting about observing asteroids

— they’re giant space rocks, after

all — but the success of NASA’s Dawn

mission turned Vesta into a particularly

compelling target. While the Hubble

Space Telescope had resolved some of

its largest surface features in the 1990s,

it wasn’t until the Dawn spacecraft

dropped in on Vesta in 2011 that

scientists were able to study the asteroid

in detail. Vesta is almost, but not quite,