Like most people, I'm highly interested in the hunt for habitable worlds, planets that could truly be called Earth 2.0. But sometimes we need to step back from the 'habitable' preoccupation and think about the extraordinary range of worlds we've been finding. I'm reminded of something Caleb Scharf says in his new book The Copernicus Complex (Farrar, Straus and Giroux, 2014), in a chapter where he describes the work of Johannes Kepler and other astronomical pioneers. Kepler's laws of planetary motion first told us that planetary orbits are ellipses rather than the perfect circles envisioned by the school of Ptolemy. The implications are striking and lead us to expect just the kind of wild variety we find in the exoplanet hunt, where we're uncovering everything from 'hot Jupiters' to 'super-Earths' and a wide variety of Neptune-like worlds. Says Scharf: If planets follow elliptical paths as a general rule, and those paths need not be all within a single plane around a centrally massive...

While I'm in Houston attending the 100 Year Starship Symposium (about which more next week), Andrew LePage has the floor. A physicist and freelance writer specializing in astronomy and the history of spaceflight, LePage will be joining us on a regular basis to provide the benefits of his considerable insight. Over the last 25 years, he has had over 100 articles published in magazines including Scientific American, Sky & Telescope and Ad Astra as well as numerous online sites. He also has a web site, www.DrewExMachina.com, where he regularly publishes a blog on various space-related topics. When not writing, LePage works as a Senior Project Scientist at Visidyne, Inc. located outside Boston, Massachusetts, where he specializes in the processing and analysis of remote sensing data. by Andrew LePage Like many space exploration enthusiasts and professional scientists, I was inspired as a child by science fiction in films, television and print. Even as a young adult, science fiction...

Bringing some order into the realm of 'hot Jupiters' is all to the good. How do these enormous worlds get so close to their star, having presumably formed much further out beyond the 'snowline' in their systems, and what effects do they have on the central star itself? And how do 'hot Jupiter' orbits evolve so as to create spin-orbit misalignments? A team at Cornell University led by astronomy professor Dong Lai, working with graduate students Natalia Storch and Kassandra Anderson, has produced a paper that tells us much about orbital alignments and 'hot Jupiter' formation. It's no surprise that large planets -- and small ones, for that matter -- can make their stars wobble. This is the basis for the Doppler method that so accurately measures the movement of a star as affected by the planets around it. But something else is going on in 'hot Jupiter' systems. In our own Solar System the rotational axis of the Sun is more or less aligned with the orbital axis of the planets. But some...

In terms of habitability, it's clear that getting a world too close to its star spells trouble. In the case of Gliese 581c, we had a planet that some thought would allow liquid water at the surface, but subsequent work tells us it's simply too hot for life as we know it. With the recent dismissal of Gl 581d and g (see Red Dwarf Planets: Weeding Out the False Positives), that leaves no habitable zone worlds that we know about in this otherwise interesting red dwarf system. I'm glad to see that Stephen Kane (San Francisco State) and his team of researchers are working on the matter of distinguishing an Earth-like world from one that is more like Venus. We've made so much of the quest to find something roughly the same size as the Earth that we haven't always been clear to the general public about what that implies. For Venus is Earth-like in terms of size, but it's clearly a far cry from Earth in terms of conditions. Indeed, you would be hard-pressed to find a more hellish place than...

In Greg Bear's novel Queen of Angels (Gollancz, 1990), a robotic probe called AXIS (Automated eXplorer of Interstellar Space) has used antimatter propulsion to make a fifteen-year crossing to Alpha Centauri. The world's various networks of the future begin to feast on reports of what it finds, like this one: "In the past few weeks, AXIS has returned images of three planets circling Alpha Centauri B. As yet these worlds have not been named, and are called only B-1, B-2, and B-3. B-3 was already known to moonbased astronomers; it is a huge gas giant some ten times larger than Jupiter in our own solar system. Like Saturn, it is surrounded by a thin rugged ring of icy moonlets. B-1 is a barren rock hugging close to Alpha Centauri B, similar to Mercury. But the focus of our attention is now on B-2, a justright world slightly smaller than Earth. B-2 possesses an atmosphere closely approximating Earth's, as well as continents and oceans of liquid water. It is orbited by two moons each about...

For those of you who, like me, are fascinated with red dwarf stars and the prospects for life around them, I want to mention David Stevenson's Under a Crimson Sun (Springer, 2013), with the caveat that although it's on my reading list, I haven't gotten to it yet. More about this title after I've gone through it, but for now, notice that the interesting planet news around stars like Gliese 581 and GJ 667C is catching the eye of publishers and awakening interest in the public. It's easy to see why. Planets in the habitable zone of such stars would be exotic places, far different from Earth, but possibly bearing life. At the same time, we're learning a good deal more about both the above-mentioned stars. A new paper by Paul Robertson and Suvrath Mahadevan (both at Pennsylvania State) looks at GJ 667C with encouraging -- and cautionary -- results. The encouraging news is that GJ 667Cc, a super-Earth in the habitable zone of the star, is confirmed by their work. The cautionary note is...