This artist's concept illustrates the idea th...
Earth-hunting, guerilla style
Minerva is a grassroots planet-hunting machine
September 06, 2012
Like a lot of other astronomers, Caltech’s John Johnson is interested in looking for exoplanets that could be like Earth. And like a lot of those astronomers, he’s found that instruments that can help in the search are not only hard to find, but tend to be booked for months on end by scientists doing non-exoplanet observations. Building new, large telescopes for planet-hunting takes years of planning, design, and funding coordination efforts.
“We’re in this exciting new era of discovery, but it’s so difficult to make observations with the telescopes that are already out there,” Johnson explains. “We’ve learned a lot in the past two decades of planet hunting, but it’s time for more dedicated exoplanet instruments, and I didn’t want to wait around.” So, along with Penn State University and the University of Montana, he’s decided to build an exoplanet finding telescope system on Palomar Mountain in California called Minerva. “Kepler has shown us the power of a dedicated exoplanet instrument—it has revolutionized the entire field in just a couple years…now we know that small, rocky planets are probably the most common. Build a dedicated instrument and you will find planets…you will find Earths.”
One of the individual telescopes of the Minerva project.
Compared to many other telescopes, especially ones powerful enough to spot the exceedingly faint signatures of Earth-size exoplanets, Minerva is designed to be deployed quickly and relatively inexpensively. The system will eventually consist of four 0.7-meter, off-the shelf telescopes set up in an array on Palomar Mountain in southern California. Each telescope will be able to observe targets either on its own or in sync with the others, giving the system a large amount of flexibility. Using the small telescopes together will give Minerva the power of a much larger telescope and make it one of the only ground-based instruments capable of finding rocky exoplanets like Earth.
Minerva is designed from the ground-up to be a lean, mean exoplanet-finder. “The telescopes are operated robotically. They are small, cheap, and easy to stabilize,” Johnson explains. While many exoplanet astronomers may only get a few days a year to use a particular telescope, Minerva will make only exoplanet observations. “We will look at fewer stars, but we will observe each one, in-depth, every single night.” Johnson hopes that Minerva will be able to find how many “super-Earths”—rocky planets 2-3 times the size of our own—orbit in the habitable zones of nearby stars.
Johnson says that Minerva will focus mainly on finding Earth-like exoplanets that are close to our own solar system. “Looking for Earths and super Earths around nearby stars will help us understand more about what’s close by,” Johnson said. “It’ll also make it easier for us to follow up on our discoveries and make more detailed observations of the planets we find.” Caltech graduate students and postdocs will operate and manage the telescope, and an emphasis will be placed on making the equipment available for other exoplanet researchers to use.
Minerva will also be the only exoplanet-focused telescope with the ability to search for planets using the two most popular methods of exoplanet-hunting: the transit method, which looks for the dip in light caused by exoplanets passing in between Earth and their host stars, and the radial-velocity method, which looks for stars that very slightly “wobble” in space due to the gravity of their planets. Using both methods can provide astronomers with a wealth of information about the planets they observe, such as their radii and internal structure.
A diagram of one of the Minverva project enclosures with two telescopes.
Originally an acronym for an earlier iteration of the telescope, Minerva is named for a Roman goddess that was born from the head of the god Jupiter—in the same way that the project was developed by the collective brains of Johnson’s ExoLab team.
Johnson and his collaborators expect Minerva to begin observations on Palomar Mountain in 2014, with the first telescope being installed next spring. Johnson's team is currently testing the operation of the first telescope with its custom designed enclosure and suite of auxiliary equipment.Along with the recently-deployed Project 1640, the installation of Minerva will make Palomar a hotbed of cutting-edge, dedicated exoplanet instruments.
Johnson explains that Minerva is a major step forward in the rapidly expanding world of exoplanet research, both for its flexible, modular design and the way it has been jointly funded by the involved institutions. “We need telescopes that are dedicated to exoplanets, and we don’t want to wait years for them to be designed and funded and built,” he says. Johnson hopes that a successful Minerva will inspire other astronomers to look for ways to continue pushing the envelope despite monetary and planning obstructions that can make building new equipment a long process. “We’re doing this more guerilla-style, finding the money to do it and building it ourselves.”