Indeed, as we search for life on other planets, we've used the Earth as our standard reference. Practically speaking, it's the only model we've got — and it appears to be a pretty damned good one; Earth has been teeming with life for billions of years and, quite importantly, it's even spawned a radio-capable, space-faring civilization.
That being said, what makes us so sure it's the best model for habitability? Could other planets or moons be even more suitable for life? A pair of astrobiologists say yes. To find a habitable and ultimately an inhabited world, they argue we should adopt a biocentric approach rather than a geo- or anthropocentric one.
The morning sky will play host to a spectacular gathering of solar system objects grouped closely together tomorrow (Nov. 22), but it won't be easy for observers on Earth to see it.
The sun, moon, three planets and the dwarf planet Ceres will all appear within a 20-degree span of sky. (For reference, your clenched fist held up to the sky measures about 10 degrees across.) Mercury and Saturn will be just west of the sun and new moon, while Venus and Ceres will be to the east. Unfortunately, the bright sun will wash out the beautiful "conjunction," but interested observers can still use a planetarium software program like Starry Night to check out the stunning event.
"Planet X" might actually exist — and so might "Planet Y."
At least two planets larger than Earth likely lurk in the dark depths of space far beyond Pluto, just waiting to be discovered, a new analysis of the orbits of "extreme trans-Neptunian objects" (ETNOs) suggests.
Researchers studied 13 ETNOs — frigid bodies such as the dwarf planet Sedna that cruise around the sun at great distances in elliptical paths.