Astronomy

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make a 10 ̊ sweep east with a wide-field

eyepiece. You are within striking range of

another celebrated pack of reasonably

bright galaxies: M95, M96, and M105.

M95 and M96 are separated (east-west)

by only 42'; both magnitude 9.5 barred spi-

rals are about 7' wide, with tight arms that

wind around a bright core, forming both a

bright inner annulus and a fainter outer

ring. Only M95 is seen nearly face-on

(looking like the Death Star from Star

Wars), while M96 is inclined 45 ̊. M96 is

also the more curious of the two, as it is a

one-armed spiral that loops around the

core from the southwest to perform a tight

counterclockwise inner swirl, forming an

ill-defined inner annulus before looping

again to form a warped outer loop, the

northern rim of which is rife with star

formation. And this is where it gets

interesting.

About 1 ̊ east-northeast of M96 lies its

extragalactic neighbor M105, with two

close attendants: the 11th-magnitude len-

ticular galaxy NGC 3384 about 7' to the

northeast and 12th-magnitude NGC 3389

(which is most likely a background galaxy)

near equidistant to the southwest. We can

now imagine the location of the Leo Ring,

a giant blossom of cold gas that surrounds

these galaxies; it once was one of the night

sky’s most dramatic and mysterious clouds

of intergalactic gas in the radio spectrum.

First detected by radio telescopes in

1983, the ring was further studied in 2009

by the ultraviolet vision of NASA’s GALEX,

which detected emissions interpreted as

dwarf galaxies forming out of primordial

gas. A year later, astronomers using the

Canada-France-Hawaii Telescope found

optical emissions associated with the ring

— not from dwarf galaxies, but from bursts

of star formation along the ring. Their

models indicate that the gas is not primor-

dial, but formed by a billion-year-old colli-

sion between M96 and NGC 3384.

Let’s slip far to the northwest corner of

Leo’s boundaries, about 5 ̊ southeast of

Alpha Lyncis, where we’ll find the “other”

Leo Triplet: 12th-magnitude NGC 2964,

13th-magnitude NGC 2968, and 14th-

magnitude NGC 2970. Included in

Astronomy contributing editor Phil

Harrington’s Cosmic Challenge, this triad

appears through modest-sized telescopes as

a series of extragalactic “dust motes.”

Whereas NGC 2964 is oriented east-

west, measures 3' by 1.5' across, and sports

a tiny, fuzzy core, NGC 2968 is oriented

northeast-southwest, measures 2' by 1.5',

and reveals no core. In reality, NGC 2964 is

a mixed spiral galaxy, and NGC 2968 is an

irregular galaxy with a peculiar S-shaped

dust lane running lengthwise through its

body. But there’s more! A tidal tail con-

nects NGC 2968 and NGC 2970, extending

to the northeast. NGC 2970 is a true visual

dust mote, measuring only 0.5'.

NGC 2968 is very distorted and sur-

rounded by shells. What’s more, a super-

nova occurred in 1970 on the luminous

bridge, confirming a physical association

between NGC 2968 and NGC 2970.

If you make an astonishing observation

of any of these exotic features, send an

email to [email protected].

Stephen James O’Meara is a well-known

observer, author of many books, and a

contributing editor of Astronomy.

Left: Another trio in Leo consists of M95 (left),

M96 (above center), and the elliptical galaxy

M105 (right). Other galaxies lie near M105,

including NGC 3384 (above and right of M105)

and NGC 3389 (above NGC 3384). DANIEL B. PHILLIPS

Above: The 12th-magnitude galaxy NGC 2964

(top right) lies near another strange galaxy,

NGC 2968, which has a twisting dark lane

running across its midsection. JOHN BESWETHERICK/

ADAM BLOCK/NOAO/AURA/NSF

NGC 3628 has a tail

that looks like an

ocean liner trailing

smoke. Can it be

seen visually? And if

so, at what aperture

and magnification?