The skies cleared on Friday evening of Family Weekend, and it was a dark, moonless night — just in time for the Perkin Observatory Open House. We started with a brief constellation tour. At the end of the tour, we pointed the green laser pointer to one last faint-looking star. But it wasn’t just one star. It was about one trillion (1,000,000,000,000) stars — the Andromeda Galaxy. We’re able to see some of the collective starlight from Andromeda with our naked eye, as the galaxy is the largest one in the galaxy cluster we live in and happens to be the closest major galaxy to us. All of the stars we saw from Memorial Field are tens to only a few thousand lightyears away, but Andromeda is about 2.5 million lightyears away. Light takes one year to travel one lightyear, so, light from Andromeda takes 2.5 million years to reach Earth. When we look at Andromeda, we are looking 2.5 million years back in time.
We moved into the Observatory for a closer look at Andromeda. The Observatory classroom was packed, but everyone had a view of the projector. The telescope was equipped to photograph Andromeda, and the audience got to see how the various instruments and software work together to perform astronomical imaging. Students and younger siblings got to operate the computer controls. After taking one long exposure of Andromeda that revealed a lot of faint, fuzzy light around the bright core of the galaxy, we discussed the further steps required to best capture the detail of the galaxy. Many frames of Andromeda must be acquired and averaged in a way to minimize the random “noise” due to the brightness of the background sky itself (the camera sensor is very sensitive!). Also, many calibration frames must be used to correct for inherent imperfections in the performance of the camera and optical system.
Our last look at Andromeda (shown below) was an image that is the result of a full imaging process that the Observatory performed earlier in October.
The final image was produced from 100 individual frames of Andromeda and 100 calibration frames. Looking at the image, we see not any distinct stars in Andromeda but now its collective light in much greater detail. The distinct stars are all way in front of Andromeda; they are in our galaxy, the Milky Way. Starlight can be seen from two other galaxies; they are small galaxies in orbit around Andromeda.
We ended the evening by taking single long exposures of two other types of objects. One was of a section of the Cygnus Loop supernova remnant, and the other was of the Pelican Nebula.
Thank you to all the families that participated in the Open House! We hope your visit has made you think of many more questions and that these questions may bring you back to the Observatory or lead you to other opportunities to explore the Universe.