Sunday, May 27, 2012

M 109

Similar to our galaxy in size and shape (it's a barred spiral galaxy), our sister lies 83 million light years away towards the Ursa Major constellation.

When I first saw it nine years ago as a faint patch of light near the bright star Phecda, I imagined exactly this: 

Monday, May 21, 2012

Peak District: cold, night, spring

Twilight arrives finally in UK's Peak District National Park. Charged with color beauty, Venus trails along the Pleiades on it's journey away from the Sun: it is the last time it goes away from it before the famous Venus transit this June (more about that soon!).

  Even though it's cold, some people do look up, through the dense photon cloud of light pollution

The road to light below us (it was oriented towards West :) )

        ... and he stands below all that is timeless for most humans: stars!

Saturday, May 5, 2012

Super, super Moon!

  March 19th 2011 full Moon vs May 4th 2012 full Moon    ====    ~357 300 km vs ~358 000 km 

      The orbits of the planets around the Sun are not circular but elliptical, as are the orbits of the satellites around planets.

      Also, the Moon orbits the Earth on an orbit which can be quite well approximated by an ellipse. This means that sometimes it is father away from the Earth (farthest point being named apogee) and sometimes closer (closest point named perigee). The numbers for this would be: average distance - 384 399 km , apogee distance - 405 410 km and perigee distance - 362 570 km, only a 14% difference between the farthest and closest points! :)

      To put in in context, the Wikipedia animation below shows the Earth, Moon and their average distance to scale (with the yellow line simulating a beam of light travelling from Earth to the Moon in real time). I placed the arrow about where the perigee of the Moon would be.

                                                                                                                                                                                                  perigee   |

      Imagine yourself noticing from 100m away that a plant has grown from 45cm to 48 cm, seeing it one month after the first time. Most people will definitely not notice the size difference, but the power of suggestion is strong enough that it might really seem that it is smaller, or larger (depending on what that person was told).

        It is quite fashionable today for the mass-media to report the weirdest things and not discriminate between being informative and the opposite. We will most likely have this "supermoon effect" for the next years, just as we have the "Mars Hoax" every late august since 2003, when Mars came closest to Earth in many years (still some 55 million km away though). 

       Speaking of weird things that some people say without any kind of research whatsoever: do you remember the devastation that last year's March 19 brought? No? Well, the Moon was then even closer than now when full, yet nothing out of the ordinary happened. The March 11 Japan earthquake took place when the Moon was just leaving the apogee, being 398 000 km away.

The rise of  March 19th 2011 "SuperMoon" over the DHL Tower in Bonn, Germany

      In conclusion: enjoy the Moon, whether it's half, full or a beautiful thin crescent and while thinking that some things in astronomy can only be measured with a more precise device than the human eye.

Friday, May 4, 2012

Celestial highway

Planets wander on the sky on their own highway: the zodiacal band. Even dust in the solar system is somewhat confined to this plane and you can see it here as a lighter conical region in the middle of the image. Sometimes the planets and the Moon catch up in meetings as beautiful as this one:

Moon-Venus-Jupiter conjunction

Sitting on the caldera edge of the Taburiente supervolcano in the Atlantic ocean, a true photon feast!

Wednesday, May 2, 2012

Crab nebula and polarized light

      Besides wavelength (color), photons have other properties too: if seen as a wave their electric field oscillates in a plane which can remain fixed or rotate in time and by convention we describe this polarization state by specifying the orientation of the electric field over one oscillation.

      Polarimetry is a very useful tool for determining what kind of physical processes are at work in the light source (especially for synchrotron radiation) and the distribution of magnetic fields in it: there is much more to light than just color!

     Polarimetry color information superimposed on a "normal" photograph of Crab nebula creates the unusual picture below. The red color in the nebula comes from an arbitrary initial polarisation angle (we weren't able to find out yet the true polarizing angle), the green shows 45 degrees more and the blue is with the filter rotated by 90 degrees compared to the original position.

The image has been made by me (color and luminance data) and David Muelheims (polarized data), in Bonn, Germany.

        And although "popular wisdom" might tell you that the human eye cannot distinguish between polarization states, it's not really true, as Haidinger found out many, many years ago :)

Dubna наукоград: noctilucent!

A rather cryptic title for a post with some clouds over a lake or something, right? 

     Dubna naukograd, the science city! It is an international center for nuclear physics and so much has been done here (and is being done here) that we even named an element after it: Dubnium (A=105)!
     While spending the summer there I had the chance to do two things: live in a perpetual state of light and twilight (the sun was barely setting before going up again, Dubna is quite up north) and witness magnificent displays of noctilucent clouds. 


       What clouds?!? While taking an airplane sometimes people might say that "you're above all the clouds!"; this is quite far away from the truth, as there are clouds "slightly higher" than where the usual stratospheric planes fly, at 10-12 km altitude. These special clouds are so high that are way beyond stratosphere and at the edge of space: ~85 km high, in the mesosphere, just below the mesopause. It's very cold there (-125 Celsius degrees) and guess what: we don't really know what they are and how they form. To solve this, we launched a satellite, the Aeronomy of Ice in the Mesosphere (AIM) which started it's mission quite recently.

      Wispy, electric blue, at the edge of space and seen at the end of twilight close to the summer solstice in regions as far away from the poles as 45 degrees latitude, they are a joy to watch and observers gather their sightings and more information here. As the climate gets warmer, the mesosphere gets colder and they are becoming a more common sight closer and closer to the tropical regions of our planet.

   ...and yes, these pictures are taken at midnight! :)