Metallic Snow...

Really!

Transit of Venus...

A nice video compilation of observations of the recent transit of Venus, made by various scientific instruments operated by NASA.  More than anything I've seen recently, this video brings home just how much our solar observing capabilities have improved in just the past few years.  Most of the differences in the various views you'll see have to do with what wavelengths of light are being observed.  From APOD, of course – and when you click over there, don't miss the links to other photos of the transit.  Some of them are amazing!

Venus on the Edge...

A few days ago we had the rare transit of Venus across the sun (as seen from Earth, of course).  This image, captured by the Hinode spacecraft, a joint Japanese/U.S./U.K. mission.  It is in orbit around the Earth, so it saw the transit of Venus just as us surface-dwellers did.

This image shows Venus just as it crossed one edge of the sun.  If you click on the photo to enlarge it, you can clearly see a bright ring all the way around Venus – sunlight refracting through Venus' carbon dioxide rich atmosphere. 

Photo from APOD, of course...

The Transit of Venus...

Unless you've been living under a potted plant for the past month or so, you know that there will be a transit of Venus across the face of the sun next Tuesday evening (in the U.S.).  The next such transit of Venus won't happen until the year 2117 - so this is your last chance (in this lifetime, at least!).  At right is a photo of the last such transit, courtesy of APOD.

With the right equipment (inexpensive and easy to obtain) and some care, you can safely see this yourself.  Or you can watch it online, in real time.

More information about the transit and how to watch it yourself, here, here, and here...

Transit of Venus...

Just a month from now (June 5 or 6, depending on where you are), the planet Venus will move across the face of the sun (as seen from Earth).  Astronomers call these events “transits”.  This is the last transit of Venus over the sun for over 100 years, so if you want to see one, this would be the time to do it.  More information here and here.

Mercury MESSENGER

It’s been almost a year since I last posted about the MESSENGER mission to the planet Mercury. The long interlude isn’t from lack of interest — there just hasn’t been much happening. That’s because MESSENGER is one of the now-common missions that uses gravitational assists from planets to greatly lower the fuel requirements. In MESSENGER’s case, it will be getting a total of six such gravity assists from planetary flybys: one from Earth (last August), two from Venus (the first one on October 24, 2006), and three from Mercury. Not until 2011 will MESSENGER finally make its orbital insertion burn. Between now and then there’s not much happening, except for those planetary flybys, each of which is planned to generate much good science.

The picture at right was taking on the Earth flyby (click for a larger view).

The planned orbit around Mercury is interesting. From the MESSENGER official web site:

MESSENGER’s orbit about Mercury is highly elliptical (egg-shaped), 200 kilometers (124 miles) above the surface at the lowest point and more than 15,193 kilometers (9,420 miles) at the highest. The plane of the orbit is inclined 80° to Mercury’s equator, and the low point in the orbit is reached at a latitude of 60° north. The low-altitude orbit over the northern hemisphere allows MESSENGER to conduct a detailed investigation of the geology and composition of Mercury’s giant Caloris impact basin - the planet’s largest known surface feature.

About 33% of the spacecraft’s propellant is required for Mercury orbit insertion – the process of placing the spacecraft into its primary science orbit around Mercury. MESSENGER’s thrusters must slow the spacecraft by just over 0.83 kilometers (0.52 miles) per second. As the spacecraft approaches Mercury, the largest thruster must be pointed close to the forward velocity direction of the spacecraft. The first maneuver (lasting about 15 minutes) places the spacecraft into a stable orbit; it also sets up a much shorter cleanup maneuver two to three days later near the orbit’s lowest point.

We’ll be keeping an eye on this mission. In the meanwhile, visit the MESSENGER site for more information.