Dear friends,
Our observations with the Green Bank Telescope on April 27, 2018 went extremely well. We observed 15 solar-type stars (and their presumed planetary systems) that are located in the plane of the Milky Way. In astronomical parlance, these stars are G-type main-sequence stars (spectral type G and luminosity class V), with masses between approximately 0.84 and 1.15 solar masses and with surface temperatures between 5300 and 6000 K. Solar-type stars are not particularly common: only about 8% of all main-sequence stars are type G. However, they are sensible targets for the search for life in the universe because we know that life is possible in the vicinity of G-type stars. Most searches tend to focus on M-type stars, which have a longer lifespan and are therefore more abundant (about 76% of all main-sequence stars are type M). In my view, the focus on M-type stars is largely due to the fact that they are the easiest lampposts to search under, and not because they are superior targets for the search for life.
|
|
|
|
The UCLA Spring 2018 SETI class during our observations with the Green Bank Telescope on April 27, 2018. The telescope control windows can be seen projected on the screen in the background.
|
|
|
|
|
|
|
Students in the SETI course finalized their target list on April 25, 2018, which coincided with a massive data release related to the European Space Agency's Gaia mission. Gaia provides important distance measurements (stellar parallax) and other information for at least 1.3 billion stars, and there had been much anticipation about this data release. Astronomers worldwide downloaded the huge catalog that day, bringing data servers to their knees and preventing students from accessing the catalog. I had asked the students to obtain the Gaia estimate of the distance to their targets, but I had not appreciated that it would be impossible for the students to do so that day. Fortunately, the Gaia servers recovered the next day, and we now have precise estimates of the distances to all of our targets, a welcome improvement compared to the incomplete distance information in previous editions of the course. Distances to our 2018 targets span the range 100–500 light years.
|
|
|
|
All-sky image (equirectangular projection) of the Milky Way and neighboring galaxies based on the newly released Gaia data. All of our 2018 targets lie in the galactic plane, which appears as the bright horizontal structure in the middle of the image.
Image credit: Gaia Data Processing and Analysis Consortium (DPAC).
|
|
Students in the course have followed the usual sequence of learning about Fourier transforms, writing code to compute power spectra with the Fast Fourier Transform (FFT) algorithm, arranging consecutive power spectra in time-frequency diagrams, and looking for narrowband signals that drift through frequency as expected of extraterrestrial emitters. Our favorite practice signal was once again the carrier signal emitted by the Voyager 1 spacecraft, humanity's most distant ambassador. For a comprehensive description of these analysis steps, please see the May 2, 2016 issue of our newsletter.
As pointed out by one of the students, one of the most satisfying aspects of the course is that this class of students is building on the work done by the classes of students that preceded them. Our processes and algorithms are getting better each year. This year, for instance, we have already identified over a million candidate signals in our data, something that we were not able to achieve in previous years until the end of the academic year. Because we are further along in the analysis this year, we will be able to devote additional time to improving our data processing pipeline and exploring new computational challenges. I am eager to see what the students in this class will accomplish.
Warm regards,
Jean-Luc Margot
|
|
|
|
|
