Astronomy

54 ASTRONOMY • MAY 2018

M

ost deep-sky hunters

associate Leo with

galaxies ... and so

they should. Although

the celestial Lion has

other wonders (espe-

cially Regulus and Gamma Leonis, two

regal double stars), we can enjoy them on

our way to more exotic galaxies.

Most of these galaxies can be seen read-

ily through modest-sized apertures, but

some will require much greater apertures.

Others still are best appreciated by involv-

ing the imagination to see the delicate dra-

mas unfolding in and around them in

wavelengths that extend beyond the eye’s

visual range. After all, astronomy is half

science, half imagination.

I hope the latter exotics will inspire

astroimagers to capture these objects and

their demanding details and bring them to

light so the rest of us can enjoy them as

they truly are.

Hidden dwarfs

Leo harbors a fine selection of dwarf galax-

ies, many of which can be enjoyed by

observers using telescopes both large and

small. But we’ll start with a visual chal-

lenge: the 10th-magnitude dwarf spheroidal

Leo I.

Astronomy Senior Editor Michael E.

Bakich succinctly summarizes the situa-

tion: “Easy to find, hard to see.” The galaxy

lies only 20' north of Regulus (Alpha [α]

Leonis), but its light spreads across 12' by 9'

of sky. (That’s comparable in size to NGC

205, but two magnitudes fainter and with

no core!) Add in glare from Regulus, and

you’ve got a wonderful visual challenge.

Hints: Use a wide-field eyepiece that

provides moderate magnification (70x),

push Regulus out of the field of view, and

gently tap the tube as you look for a dim

and uniform carpet of ethereal light against

a bleak background of stars. At a distance

of 800,000 light-years, Leo I may be the

farthest satellite system orbiting our galaxy.

Regulus itself is a multiple star system

that can be seen with binoculars and tele-

scopes, and offers a secret challenge. This

glistening 1st-magnitude jewel shines with

a dazzling light. An 8th-magnitude “violet”

(a color-contrast illusion at low power)

companion (B) lies 3' to the northwest; B is

actually an orange dwarf. If you are using a

large aperture (12 inches and greater), don’t

stop there. Use 300x or more on a night of

excellent seeing to look for that orange

dwarf ’s 13th-magnitude red dwarf com-

panion (C) 2.5" to the east. The greater the

magnification, the greater the apparent

separation, and the greater your chances

are to see faint objects.

Yet there’s more! Even small-telescope

users can search for a 12th-magnitude line-

of-sight companion (D) 3' due west of

Regulus — a sneaky little star often missed

by the casual viewer. What you can’t see is

the spectroscopic object, speculated to have

once been a luminous giant greater than

Regulus but is now an Earth-sized high-

density white dwarf star of 0.3 solar mass.

Take a deep breath before you head to

our next challenge, Leo III (Leo A). This

enigmatic dwarf galaxy is one of the most

Below: Two odd galaxies, NGC 3226 and

NGC 3227, float in Leo as they gently lock

in a tidal embrace. NGC 3227 (right) is the

somewhat brighter barred spiral in this

interacting pair. Elliptical galaxy NGC 3226

lies to its left. ROBERT LOCKWOOD