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filter because it gives a nice balance of

nebular detail and stars.

The Flame hides a star cluster made

up of some 800 newly formed stars and

protostars, ages 0.2 to 1.5 million years

old, with the newest clustering toward

its centre. Discovered by near-infrared

observations, the vast majority of

these stars seem to have circumstellar

discs. We can’t see this cluster at visual

wavelengths, but it’s fascinating to

know it’s in there.

The Flame is approximately the

same distance away as IC 434, the

Horsehead, M42 and all the other

nebulaeinthisregion—about1,400

light-years—becausethey’reallpart

of the Orion Molecular Cloud. We can

thinkofthemasbeingthebrightest

parts of the same nebula. The main

difference is that their illuminating

stars energise them to different degrees

andfromdifferentangles.

IC 431,IC 432andIC 435are

smaller,fainterversionsofNGC2023

— stars surrounded by faint reflection

nebulosity — and bracket the Flame

Nebula to its southeast and northwest.

They’re fun to track down if you can

tear yourself away from the more

famous and obvious sights in the area.

ThemultiplestarSigmaOrionisthat’s

energising IC 434 shines at magnitude

3.8 and is surrounded by a loose cluster

of low mass and brown dwarf stars. It’s

also part of the Orion OB 1 b stellar

association, which includes all three of

the Orion’s Belt stars.

Ofcourse,byfarthemostobvious

and spectacular object in this area is

Alnitak. At magnitude 1.8, it’s actually

a close visual double star, with its A and

B components shining at magnitude

1.9 and 3.7, respectively, and separated

by about 3′′.They’reabeautifulsight

when the seeing is steady enough to

splitthemcleanly.Athird,unseenstar

was discovered spectroscopically. The

AcomponentisthebrightestOstar

inthesky,withtheothertwostars

belonging to spectral typeB.

All this starry brilliance should

XTHE HORSE’S HEAD UP CLOSEThis

European Southern Observatory image of

theHorseheadNebulawasobtainedwiththe

8.2-metreKueyentelescope,oneofthefour

VeryLargeTelescopeunitsatCerroParanal

intheAtacamaDesert,Chile.Notethebright

edge along the top of the horse’s mane, head,

browandmuzzle,allofwhichcanbedetected

by visual observers. The more diffuse area

alongthebottomofthemuzzlecanalsobe

seenbutismuchmoredifficultbecauseof

lowercontrast.Themostchallengingareais

theever-so-slightlylessdarkareainteriorto

themane.Theorientationisthesameasinthe

other images.

be placed outside the field of view

when trying to observe the Horsehead

throughawide-fieldinstrument.Even

so, it’s possible to see both at the same

time if you keep the Horsehead Nebula

in the sweet spot of your averted

vision, then move Alnitak into the field

of view.

This corner of Orion would be

irresistible even without the Horsehead

Nebula, but there’s no doubt this most

famous of the dark nebulae is the main

attraction. Its shape

reallycanlooklike

theprofileofahorse’s

head, and even

though I sometimes

think of the chess

piece, there’s no more

aptly named object in

the sky.

„HOWARD BANICH

and Chuck Dethloff,

friends who’ve

observed together

since 1991, still get

excited about a great

view of the Horsehead

Nebula. Howard

can be reached at

[email protected].

STHE HORSEHEAD AND COMPANIONS This labelled version of the author’s sketch helps

set the scale of the Horsehead with its surroundings. The ½° circle centred on the Horsehead

is about the same apparent size as the full Moon, and the Horsehead itself is nearly the same

apparent size as the Dumbbell Nebula. The hydrogen-beta filter tends to produce its highest

contrast views when used with an eyepiece that gives a 4-mm to 7-mm exit pupil, so try to use

eyepieces that fall in this range.

SKETCH: HOWARD BANICH; CLOSE UP: ESO

NE

IC 434

IC 435

IC 434

IC 434

IC 431

IC 432

NGC 2023

NGC 2024

(The Flame Nebula)

Zeta Orionis

(Alnitak)

B33

The Horsehead Nebula

Sigma Orionis

0.5 degree circle