The announcement yesterday of the discovery of the closest Earth-sized planet found so far that also exists in the habitable zone around its star is certainly exciting (read our previous article for all the details). Gliese 581g is surely a potential habitable planet where liquid water could exist on the planet‘s surface, and many are touting the old adage of where’s there’s water, there’s life. However, some quotes from one of the scientists involved in the discovery might be feeding some wild speculation about the potential for life on this extrasolar planet and elsewhere.
“Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say, my own personal feeling is that the chances of life on this planet are 100 percent,” said discoverer and astronomer Steven Vogt during a press briefing yesterday. “I have almost no doubt about it.”
Astronomers have taken the best picture yet of a planetary system being born. The image, taken by the Atacama Large Millimeter/submillimeter Array (ALMA) in the high-altitude desert in Chile, reveals a planet-forming disk of gas around a young, sun-like star, in great detail.
“The first time I saw this image, I thought it was actually probably a simulation—it was way too good,” said Tony Beasley, director of the National Radio Astronomy Observatory, in a video accompanying a press release. The NRAO helps operate ALMA.
The disk has gaps and rings that are carved out by nascent planets—features that have only been modeled in computer simulations. The star, named HL Tau, is 450 light-years away in the constellation Taurus. It’s only about a million years old—remarkably young to be already giving birth to planets.
Here's an interesting comment posted to the Wired store linked above:
pjcamp fractalsphere • 8 hours ago
About 145 AU diameter, about 450 light years distant. You can find this sort of thing in the online catalog of circumstellar disks.
Compared to the solar system is a tricky thing -- what do you consider to be the edge? Neptune's orbit? That's at 30 AU. The Kuiper belt? That's at about 30 to 55 AU. The Oort cloud? That starts at around 5000 AU and extends out to 100,000 at which point the Sun's gravitational field is weaker than nearby stars.