“Another Pale Blue Dot: Inside SETI Institute’s Exoplanet Search.”
Dr. Franck Marchis, Principal Investigator
Dr. Frank Drake’s 1980 vision of an organized Search for Extra-Terrestrial Intelligence [SETI] has become big science today. The SETI Institute boasts 200 scientists all working on the same seminal question, “Are We Alone?” The search is motivated by the facts that Hubble’s Ultra-Deep Field photo suggests trillions of galaxies in space and that life evolved only a half-million years after the planet Earth formed. Surely we will find evidence of life elsewhere.
The project is complex enough that three foci can be discerned in the Institute’s research today. First, the Technological Signals group continues sophisticated listening for non-random, intelligence-based radio signals from space. More specifically, from targeted exoplanets. This group has expanded to other bands of the E/M spectrum, including searching for laser light signals. If we know how to communicate on light waves, surely an advanced technological civilization would too.
Second, we must consider life in our Solar System. This includes studying extremophiles on Earth, living in niches previously thought inhospitable to DNA/carbon-based life. These scientists also help NASA and others devise instruments to search the moon, Mars, asteroids, and some moons of Jupiter and Saturn for “biologic signatures” of life, such as evolved gasses like CO2 , O2, O3 , besides water. Spectral analysis of light reflected from exoplanets could likewise serve as a biological signature of life.
Third, we need to consider our recent discovery of many exoplanets. The Kepler satellite studied 150,000 stars looking for a temporary dimming of their light as a planet crossed in front of the star. Decommissioned now, much of the satellite’s data must still be mined. Astronomers can now say that every star has at least two planets orbiting it. In other words, in Frank Drake’s equation the term fp, the fraction of stars with planets, is known to be 1. Amazingly, it’s even known that about 30% of discovered exoplanets are Earth-like in size, mass and are solid. This does not mean they can be listed as being in the “hospitable zone” in which liquid water could exist on the planet’s surface. That will require more precise examination of the star’s luminosity and distance from its exoplanet to compute the expected temperature at the planet’s surface. An interesting, breaking new consideration is that Jupiter and Saturn in combination may have channeled asteroids and comets towards the early Earth thereby delivering the water needed for life to evolve. If verified, the hospitable zone around a star may need to include a requirement for “cold Jupiters”, like in our Solar System, instead of the many “hot Jupiters” that have been discovered close to their star.
An unexpected and discouraging result so far is that only 8 to 15 “cold Jupiters” positioned far from their star, which is about 6%, have been detected. This may mean less viable exoplanets having liquid water than was previously hoped for. A follow-up satellite to Kepler called “TESS” will refine this measurement, once again by the transits of planets across their star.
Most research is focused on stars between 1 and 10 times our sun’s mass. The contrast and image quality of an exoplanet imaged next to its bright, large star is a major limitation, like trying to image a firefly flying near a bright lighthouse. One major advancement is adaptive optics in which a laser light wavefront is analyzed thousands of times per second, the telescope’s image is corrected for the variation using a deformable mirror that quickly moves to correct this perturbation. This produces an image as if the telescope were in space.
Dr. Marchis was a key developer of adaptive optics that took decades to be refined since its 1996 debut in Chile. He is part of a team initiated in 2003 on an ambitious project: to image Jupiter-sized exoplanets around another star. With adaptive optics installed on 8-10 meter ground-based telescopes they form better images than even the Hubble space telescope. In 2105 the GPIES survey began using adaptive optics to examine 650 southern stars. Tuned from 1 to 2.2 micron wavelengths, they were able to directly see and photograph several planets. Now, adaptive optics are being installed even on space telescopes.
The speaker is lobbying for a major space telescope around 2050 to study the nearby Alpha Centauri star system to get a precise count of Earth-sized planets in that system. This would be a short-cut method to complex surveys for getting the percentage of Earth-sized planets and determined if they could be habitable. With 20-40 meter space dishes, it will be possible to even detect oceans, continents, vegetation, air pollution, and even cities on such planets. In fact, the speaker assumes that if Earth has been investigated by satellites from highly technical aliens they would know as much about us as we might plan for in 30 years. It was revealed that there are high-level debates at the Institute about sending messages to stars we think have viable planets for life. Nicknamed “METI” it began privately with Dr. Drake who sent narrow-beamed music to certain stars. Some fear announcing ourselves to aliens, but most feel the effort is unnecessary and premature at this time, especially given the vast amount of radio and TV signals we continuously broadcast out to space.
The talk ended with a presentation of a new type telescope called eVscope initiated built by a company called “Unistellar”. It’s compact, smart, and powerful. It uses CMOS technology and real-time data processing to form an image of an object over several seconds to a minute. It then is presented to the observer in a digital eyepiece, as it is being processed and in its final form, with remarkable resolution and clarity. The hope is that a large cadre of amateurs with such a telescope can assist the SETI Institute in data collection and analysis. After the lecture a n umber of people waited in the bitter cold to observe objects in this telescope, including two galaxies and an open cluster. The eVscope is now on sale on the Unistellar website.