f humanity ever wants to colonize a planet beyond the solar system, it's going to need a really big spaceship.
The founding population of an interstellar colony should consist of 20,000 to 40,000 people, said Cameron Smith, an anthropologist at Portland State University in Oregon. Such a large group would possess a great deal of genetic and demographic diversity, giving the settlement the best chance of survival during the long space voyage and beyond, he explained.
The largest solar sail ever constructed is headed for the launch pad in 2014 on a mission to demonstrate the value of "propellantless propulsion"— the act of using photons from the sun to push a craft through space.
What causes the structure in Comet Lovejoy's tail? Comet C/2014 Q2 (Lovejoy), which is currently at naked-eye brightness and near its brightest, has been showing an exquisitely detailed ion tail. As the name implies, the ion tail is made of ionized gas -- gas energized by ultraviolet light from the Sun and pushed outward by the solar wind. The solar wind is quite structured and sculpted by the Sun's complex and ever changing magnetic field. The effect of the variable solar wind combined with different gas jets venting from the comet's nucleus accounts for the tail's complex structure. Following the wind, structure in Comet Lovejoy's tail can be seen to move outward from the Sun even alter its wavy appearance over time. The blue color of the ion tail is dominated by recombining carbon monoxide molecules, while the green color of the coma surrounding the head of the comet is created mostly by a slight amount of recombiningdiatomic carbon molecules.
ScienceNASA hopes to launch 'flying saucer' after delay
NASA hopes to try again to launch a "flying saucer" into Earth's atmosphere to test Mars mission technology after losing the chance because of bad weather, project managers said Thursday. The space agency is working with the U.S. Navy on the Hawaiian island of Kauai to see if it can get the experimental flight off the ground in June. During the current two-week launch window, the team came "tantalizingly close," but winds spoiled every opportunity, said project manager Mark Adler of the NASA Jet Propulsion Laboratory.