The Twilight's Last Gloaming

They've been breathless. Media organs worldwide have put out article after article about the discovery of an "Earth-like" planet orbiting Gliese 581, a red dwarf star twenty light-years from here: just down the street in astronomical terms. This isn't the first time that system had been the center of attention - last year the discovery of Gliese 581 e, orbiting on the outer edge of the star's habitable zone, marked the smallest planet yet discovered. It didn't take long for Gliese 581 g to break this record; the planet - quickly dubbed "Gloaming" by io9, which is admittedly a far more interesting name than "Gliese 581 g" - orbits well within the star's small "habitable zone," that being the area where the existence of liquid water on the surface is possible.

A chart of the Gliese 581 system superimposed on the inner Sol system. This image is a work of a National Science Foundation employee, taken or made during the course of the person's official duties. As a work of the U.S. federal government, the image is in the public domain.

The only problem is that the scientific vocabulary doesn't exactly intersect with the standard vernacular; indeed, there are plenty of occasions where a scientific term can easily be interpreted as something completely different by a layman. When scientists say "Earth-like," they mean that it's a rocky planet roughly similar in size to Earth. As far as the media is concerned, calling it "Earth-like" means we're just one breakthrough in theoretical physics away from being to sell vacation timeshares there.

Because really, it's "Earth-like" in many of the same ways that Mars is Earth-like. It orbits so close to its sun that it's tidelocked in the same way that Luna always presents the same face to Earth - one hemisphere of Gloaming is in constant light and the other in constant darkness, with only a thin "twilight band" around the terminator presenting the possibility of a more moderate climate. What's more, its surface gravity is likely even stronger than Earth's, presently estimated at between 1.1 and 1.7 g... and you thought launching stuff to orbit from Earth was expensive! That is, if anyone would want to live there in the first place: from what I've read, the extrapolated environmental conditions in the twilight band are disturbingly reminiscent of Yellowknife in December.

I don't know about you, but I think I've been down this road before - anyone else remember 70 Virginis b? It occupied the news for a brief time back in 1996, when it was believed it orbited within its own star's habitable zone, until further measurements refined our understanding of a far more elliptical, and far less salubrious, orbit. Admittedly the evidence for Gloaming's potential habitability is greater - but that's still all it is. While I think it's a bit early to throw Earth 2 marathons in honor of the discovery, I do find it comforting that so many people do seem so excited about this prospect.

What Gloaming's discovery really makes clear to me is that there's a massive eagerness for us to be told, authoritatively, that We Are Not Alone - or, failing that, that we've discovered where They might live, or have lived, or be yet to live, considering that technological civilizations would likely be separated just as vastly by time as they would by space.

Nevertheless, it's still an inspiring discovery. We've spent decades, centuries even, looking up at the night and guessing at what's there, hidden beyond our sight. Gloaming won't be the last we find, and in the meantime we need to encourage this interest, this thirst to know and understand what's out there, beyond. In a world of unstable economic recovery, an uncertain present, and unchecked greed, it's helpful to be able to look through our telescopes and see the future.