Monthly Archives: July 2009

some interesting IYA things

A few things have popped my way via the International Year of Astronomy, 2009.

Firstly, is there a correlation between a country’s wealth and its number of astronomers? This guy thinks there is and has correlated both members of the International Astronomical Union and professional publications by astronomers against GDP per citizen to show it. I might be more interested in how the numbers of amateur astronomers can be correlated to these professional indicators – plus the IAU has a rather low overall membership, I’m not convinced it can be divided up globally in this way.

Next, IYA2009 has been interviewing its national single point of contact for Puerto Rico to ask why did they take the job and what have they been doing for the past year?

Finally, the world tour of a production of Holst’s The Planets, accompanied by professional pictures has taken off and will be taking in these dates. Pictures from the events are here.

Possible new solar cycle found

via New Scientist.

The Sun undergoes a solar cycle on average once every 11 years, but this number can vary by as much as four years in either direction. During the solar cycle, the differential rotation of the Sun’s body – the fact that the equator spins on the solar axis faster than the poles – means that the solar magnetic field, which is embedded in the plasma that makes up the Sun, gets twisted. Over the course of the cycle, the twisting gets worse and worse, with loops of magnetic field sticking out of the body of the Sun, until the entire thing gives up and rearranges itself, turning north into south. Then it starts all over again.

The loops of magnetic field sticking out of the body show up as sunspots. Where each foot of the loop sticks into the surface of the Sun, the plasma is contained by the high magnetic field and forced to gyrate less – a phenomenon known as magnetic cooling. As a result, there’s a slightly lower amount of light sent out, making the sunspot appear darker than the rest of the solar disc.

Sunspots first appear midway between the equator and the poles in either hemisphere. Over the course of a cycle, new sunspots appear closer to the equator itself, each sunspot pair fading away after a few days. Graphs of sunspot locations with time are known as butterfly graphs for this reason, they seem to trace the outer edges of a butterflies wings.

Swiss astronomer Rudolf Wolf made it his business to count the number of sunspots occurring over time. This Wolf number gave the frequency of sunspots, but not their location. As there are more sunspots near the end of a cycle than there are at the beginning, Wolf used his numbers to determine when solar cycles began and ended. Compiling historical data, he determined that there was an extra long cycle between 1784 and 1799, lasting 15.5 years.

Even at the time this was published in the 19th century, there were doubts that there was such a long cycle then, and suggestions abounded that there were two shorter cycles in that period, but with nothing more definitive than Wolf’s frequencies of sunspots to go on, there wasn’t hard evidence either way.

However, Wolf got his numbers from somewhere and a team led by Ilya Usoskin of the University of Oulu in Finland went back to the original data – sunspot drawings by the Austrian Johann Staudecher. To these, the team added further drawings from the same period by James Archibald Hamilton and his assistant at Armargh Observatory. Now armed with both numbers and locations, a butterfly diagram could be constructed for the period.

Hamilton only drew sunspots between 1795 and 1797 and Staudecher made relatively few drawings in the period of interest, both of which increases statistical sampling errors from the new data. But Hamilton’s 1795 sunspots start of at around 15 degrees solar latitude, fairly high up for a late cycle sunspot. Staudecher’s sunspots suddenly started appearing at twenty degrees in 1793, not as high as they could be at the start of a fresh cycle, but certainly higher than they were. So it is possible that two solar cycles happened in the 1784-1799 period, one lasting nine years, the other lasting seven. But it is also possible that this is merely an exaggerated wobble that more data points might have ironed out.

The search goes on.

Mirror, mirror please don’t fall…

Testing of the enormous eighteen mirror segments that will be slotted together in space to form the 6.5m James Webb Space Telescope is underway. The eighteen mirror segments are to be exposed to conditions of temperature close to those they will experience in space. Changes in shape due to the temperature variations will be monitored to get an idea of how the segments will react to their new home.

Click here for images and videos.

Post landing news conference

Following the landing of the space shuttle Endeavour, after mission STS-127, NASA have put up a news conference on their Youtube Channel:

A picture of the shuttle kicking up dust during the landing is here.

The next mission is ISS construction mission STS-128, which will see the space shuttle Discovery put back into action. Launch is currently set for August 21st, moved back from the 18th. A briefing on the 13th will announce whether the launch stays there, moves forward or back. @Astro_Jose will be your mission commander then.

This week @NASA

The weekly NASA vodcast is up on NASA’s Youtube Channel:

Endeavour has landed!

Piloted by twitterer @Astro_127, the space shuttle Endeavour has completed its mission STS-127 by touching down at the Kennedy Space Center in Florida. Its journey took it to the International Space Station, where it constructed the outer porch of the Kibo laboratory, and then to low Earth orbit, where it deployed four satellites including DRAGONnet and ANDE2 as well as carrying out the Shuttle Exhaust Ion Turbulence Experiment. DRAGONnet is a student project to study automatous docking and rendezvous in space as well as GPS experiments. ANDE2 sees two 19 inch spheres, one weighing 25kg, the other 50kg, covered in reflective panels. They will be tracked as they decay in orbit to observe the effect of the atmosphere on identical objects of differing masses. SEIT saw a ten second burst of the engine directly into the Earth’s ionosphere, which will then be monitored by satellites to check the effect of such things on the upper atmosphere.

But it will be the ISS that this mission is most associated with, and which dominates the image gallery put out by NASA. NASA’s Youtube Channel now has a recording of the landing (shown below) and if you switch to NASA TV right now, you may catch the crew as they undergo medical checks and then make a statement on the runway:

Endeavour is Landing

Earlier today, the weather at the Kennedy Space Center was deemed fine so the crew were given the go ahead to drink fluids in preparation for re-entering the atmosphere. The space shuttle Endeavour then performed a de-orbital burn and began its descent, marking the end of mission STS-127 the ISS construction mission.

The descent can be followed on NASA TV and will be following the orbit 248 flightpath shown here. Touchdown is in about twenty minutes.