A Lightless Galaxy: Scientists Discover a Starless, Spinning Ghost

Astronomers whitethorn person conscionable stumbled crossed a shade postulation hiding successful plain show — a small, starless, fast-moving unreality of state that checks each the boxes for what’s known arsenic a “dark galaxy.” And if the find holds up, it could assistance plug 1 of cosmology’s astir puzzling holes: the mysterious “missing satellite” problem.

The team’s research, published contiguous successful Science Advances, describes AC G185.0–11.5, a compact hydrogen unreality tucked wrong a larger high-velocity unreality (HVC) known arsenic AC-I. The unreality was spotted by an planetary probe squad utilizing China’s immense FAST vigor telescope. While HVCs are known to zoom astir astatine speeds beyond that of our Milky Way’s rotation, astir are comparatively featureless state blobs. But the precocious spotted state unreality is different: it spins.

FAST’s ultra-sensitive observations revealed a wide rotational signifier successful the cloud, whose state is arranged successful a disk signifier — the benignant of operation you’d expect from a dwarf galaxy. But something’s amiss: there’s nary motion of stars successful the cloud, and nary molecular state (the accustomed star-forming stuff) to beryllium found. AC G185.0–11.5 is seemingly constituted of conscionable hydrogen gas, swirling successful space, with thing wrong it lighting it up. Ergo, a acheronian galaxy.

Using galactic question equations and a cosmic yardstick called the Tully-Fisher relation, the squad estimated the cloud’s region from Earth: astir 278,000 light-years. That puts the unreality comfortably wrong the Local Group, our galactic neighborhood. As for mass, the unreality sits betwixt 30 cardinal and astir 500 cardinal Solar masses—not huge, but capable to beryllium considered a postulation successful its ain right.

But what gives AC G185.0–11.5 its nifty statement of “dark galaxy” is its acheronian substance content. The researchers judge the unreality is held unneurotic by a monolithic acheronian substance halo, making it an perfect acheronian postulation campaigner — a theoretical benignant of postulation made mostly of acheronian matter, with small oregon nary disposable stars.

This isn’t the archetypal clip scientists person suspected that immoderate high-velocity clouds mightiness really beryllium hidden galaxies, but astir different candidates person lacked wide rotation oregon person been excessively hard to separate from the Milky Way’s halo. AC G185.0–11.5 looks similar the existent woody — perchance the champion grounds yet for a postulation that’s each nutrient and nary potatoes. You know, if potatoes were stars.

If the campaigner acheronian postulation is confirmed arsenic such, it could rewrite however we deliberation astir postulation formation. The unreality offers a tantalizing hint astir wherever each the “missing” tiny galaxies mightiness beryllium hiding — not missing, conscionable sitting lightless successful plain sight.