Photos of the Earth from a significant distance are always fascinating, dating back to the spectacular shot of the rising Earth over lunar mountains taken by Apollo 8 in December of 1968. The image below, showing Earth and its Moon, comes from the Messenger spacecraft, taken at a distance of some 183 million kilometers. I see things like this and think about our future imaging of exoplanets, and the possibilities of space-based missions that can study their atmospheres. Learning how we look helps us understand what to look for around other stars, and also offers a bit of the 'wow' factor. We're nowhere near this kind of imaging with exoplanets but we're getting better all the time, and that's providing some curious results. HR 8799 is the interesting young system some 130 light years from Earth (in Pegasus) that has yielded direct images of three planets. Some eighteen months after the discovery of the system here, we've now managed to get a spectrum of HR 8799b, useful for what it...

An individual meteorite can tell us much about the composition of ancient Solar System material, but today I want to mention a project that is taking the aggregate view. Chris Crawford has set up the Perseid Laptop Meteor Observation Project as a way to use 'crowd-sourcing' to build up a three-dimensional map of the Perseid meteor stream. Here's what Chris said about it in a recent email: This will be one of the better years for Perseids; the Moon, which often interferes with the Perseids, will not be a problem this year. So I'm putting together something that's never been done before: a spatial analysis of the Perseid meteor stream. We've had plenty of temporal analyses, but nobody has ever been able to get data over a wide area -- because observations have always been localized to single observers. But what if we had hundreds or thousands of people all over North America and Europe observing Perseids and somebody collected and collated all their observations? This is crowd-sourcing...

The planet known as TrES-2b is an interesting and useful place. Just over Jupiter mass, it orbits a solar mass star some 717 light years from Earth, a 'hot Jupiter' in a tight 2.47-day orbit. It's also a transiting planet, discovered by the Trans-Atlantic Exoplanet Survey, which uses small, automated equipment and off-the-shelf technology to get the job done, feeding planet candidates to larger installations like the Keck Observatory and Palomar Observatory. But TrES-2b has a new and important distinction: It's in the field of view of the space-based Kepler telescope. Now we're really in business. Exomoon-hunter David Kipping (University of London) said in a recent email that when this planet is viewed in 'short-cadence mode' with Kepler, it's like seeing transits in High Definition. And indeed, that seems to be the case, as you can see in the diagram below. Kepler offers two measurement cadences: 1 minute cadence for up to 512 targets and a 30 minute cadence for up to 170,000 stars....

When does it make sense to build a starship? Back in the late 1960s, Freeman Dyson went to work on the question of how much an interstellar probe might cost. Extrapolating from nuclear pulse propulsion and the state of the art in spacecraft design as then understood, Dyson arrived at an estimate of $100 billion to build the craft, which translates into roughly $650 billion today. Though stark, that figure is by no means as eye-popping as one of the estimates drawn up by the original Project Daedalus team: $100 trillion in 1978 dollars. These figures numb the senses, and you may recall the recent work by Ralph McNutt (Johns Hopkins Applied Physics Laboratory) and team, which pegged the cost of a series of human expeditions into the outer Solar System at $4 trillion. It's helpful to remember, though, that calculating when a project becomes fiscally feasible can be a useful undertaking in itself. Richard Obousy goes to work on these matters in a recent post in the Project Icarus blog,...