Discover 3

March 2018^ DISCOVER^35

ROBERTO ABRAHAM

he proposed. Yet with little in the way of supporting

data, the prophecy gained little traction.

That changed a decade later, when astronomers

stumbled upon a galaxy unlike anything they’d ever seen.

A GIANT GALACTIC GHOST

Intrigued by faint blurs on old photographic plates of

the Virgo galaxy cluster, a nearby region teeming with

galaxies, Oregon’s Bothun and colleagues wondered if

the apparitions might be smallish galaxies with “low

surface brightness” — astronomer-speak for emitting

less light per unit area than typical galaxies.

Using Puerto Rico’s Arecibo radio telescope in

1986 to detect galactic hydrogen gas clouds, Bothun

and colleagues uncovered a vast game changer of a

galaxy a billion light-years away. Dubbed Malin 1,

it’s been heavily studied ever since, and it remains the

largest known spiral galaxy, seven times wider than

The spiral galaxy M101 takes center stage in this photo from the Dragonfly telescope, but astronomers are also interested

in the fainter galaxies lurking in the background.