Exposed to the solar wind, the surface of the Moon is at the mercy of a powerful and constant stream of plasma moving radially out from the Sun. At certain points, such as crater walls and mountains at the poles, the flow of plasma is near horizontal. The obstruction causes a sort of wake to form on the sheltered side, over which some plasma tumbles.
The solar wind is composed of ions and electrons. The ions are a couple of thousand times more massive than the electrons and so take more energy to be displaced from their intended direction. The result is more electrons than positive ions tumble into sheltered areas. This creates an imbalance that has to then be shorted out somehow. The researchers have suggested a mechanism by which negatively charged dust rises from the surface to repel negatively charged electrons coming down. The Apollo astronauts in command modules above the surface of the Moon reported possible sightings of sun beams near crater edges at sunrise, suggesting some kind of particulate pollution in places. Further studies will be undertaken into this as the potential for electric discharges could damage equipment sent to study the Moon.
More detail with explanatory videos is here.
…or at least star birth in the galaxies.
Observations of galaxies in the relatively nearby parts of the Universe show a wide variety of different morphologies. One style is that of a blob of old red stars in which no star birth is present. Studies into why there are these ‘dead’ galaxies and more active star nurseries about have normally focused on ways to get star birth going – big disruptions to the gas and dust in the galaxy. However, a team of scientists using the Hubble space telescope and the Chandra x-ray space telescope have looked at this another way – what could happen to switch off a galaxy? The answer, they believe, lurks in the very centre of every galaxy – a supermassive black hole.
Using the x-ray space telescope to infer the presence of an active black hole and then Hubble to investigate the optical galaxy itself, they conclude that the effect of massive radiation from an overactive accretion disc around the black hole is expulsion of light gas from the galaxy. With little gas to then form new stars, the galaxy will simply age with its stars. They believe that with a third or so of galaxies hosting these killers, the black holes can be made to perform this deadly feat when, for example, two galaxies merge. They also believe that some galaxies holding overly violent black holes may be warped by their activity, explaining lens shaped galaxies that show no signs of collisions with others.
Last night at the Campus Party, the large gathering of techies from across the 27 EU member countries, an asteroid hunt was carried out. Advertised by post-it note and conducted through a remote telescope a review of events can be found here. The asteroid hunt was part of Global Astronomy Month. For those hoping for a more relaxed hunt for bits of spacebound rock, the Lyrid meteor shower seems to be putting on a few early shows. Last night saw a lot of radio activity and lots of individual meteors were seen including from Kendal. The shower peaks on the 21st/22nd of the month.
Forty years ago today, the crew of the mission Apollo 13 was brought back down to Earth safely, having seen off the danger of an explosion on their command module before they got to the Moon (the place they were hoping to land on and have a quick wander about).
After splashdown, the three members of the crew were picked up by a rescue helicopter from the USS Iwo Jima. From there, they were taken, again by helicopter, to American Samoa. At each point, there were people with their own cameras, including Robert Gillette, the science reporter for the San Fransisco Examiner, some of whose pictures have been published on Universe Today.