Almost a year ago, I posted a “bouldering” video which showed essentially no bouldering. The idea was borrowed from a friend’s photo essay assignment as an undergrad, where she had to document an activity without showing people actually engaging in that activity.
In the middle of a 100 hour (!) long observing block on the Arizona Radio Observatory‘s 12m telescope on Kitt Peak, I remembered this idea and thought it might be fun to do the same thing for a (remote) observing run.
I’m just wrapping up an observing run at the IRAM 30m radio telescope in Southern Spain. We have been trying to detect emission from molecules in galaxies undergoing mergers with other galaxies. These molecules are in gas clouds within the galaxies and because they have energy they rotate. Quantum mechanics dictates that they can only rotate at specific rates, with each rate corresponding to a different energy level. When the molecules jump from one rotation rate to another, they either emit or absorb a photon (depending on the difference between the energy levels). Because they can only rotate at specific rates, only specific differences in energy levels are allowed. By understanding the properties of a molecule you can predict the wavelengths of photons that will be emitted as that molecule changes rotation states.
So how do you observe these molecules? Because the photons are only be emitted at specific energies the emission from a molecule will be at a known frequency. For example, the carbon monoxide molecule (CO) emits a photon at 115.27120 GHz when it drops to the lowest rotational energy state from the state just slightly higher in energy. (This is called the J 1-0 transition). The wavelength of this photon is about 3mm, so you need a radio telescope to observe it. Other molecules will emit at different frequencies depending on their structure, but generally they emit in at millimeter wavelengths.
So you point your radio telescope at a galaxy and you might see emission from CO (J 1-0) as a spike at 115.27120 GHz, while the emission at nearby frequencies appears relatively flat. But how do you know it’s a real detection and you’re not just seeing noise in the system that is masquerading as emission from a molecule?
I am back at the IRAM 30m Telescope on Pico Veleta in the (original) Sierra Nevadas. We are 31 hours into a 60 hour block of observing time and the weather has been cooperating much more nicely than on our previous observing run in December 2010. So far we have been getting decent data on the colliding galaxies we are studying.
With the improvement in weather over my last trip here, I was able to step outside for a few minutes and get some good pictures of the telescope, and a nice shot of my co-observers and I with the telescope:
I had a small decision to make during my last afternoon at the Large Binocular Telescope. Should I go for a hike or watch the telescope be re-configured?
Well, that was easy… watch the telescope!
The LBT has system of swing-arms which move mirrors in and out of the telescope’s light path. This enables quick instrument changes, which results in flexibility while observing. While the telescope was being set up for the night’s observing, I went to the viewing gallery and shot some footage of the swing-arms in action:
Reconfiguring the Large Binocular Telescope from George Privon on Vimeo.
Continuing my odyssey of observing at any telescope that will have me, I spent 3 days last week at the MMT Observatory. The MMT (Magnum Mirror Telescope) was a test-bed for the use of multiple mirrors in a single telescope (hence the original name of the “Multiple Mirror Telescope”). In the late 1990s, the individual mirrors were replaced with a single 6.5m diameter mirror.
I have been fortunate enough to observe on a variety of different telescopes, but this is the largest I have used so far. The large collecting area enables observations of fainter objects, important for the galaxies I was observing on this run. For comparison, the last telescope I used (the VATT) would take approximately 13 times as long to collect the same amount of light from an astronomical object! Clearly having the bigger mirror is a time-saver when looking at faint objects.
More pictures of the MMT are in MMT Observing on flickr.