SOCORRO, N.M. August 3, 2009 – An interdisciplinary team of scientists at New Mexico Tech is embarking on a mission to examine planets circling other stars, thanks to a NASA grant for $732,000.
|An artist's rendering of an exoplanet with a moon orbiting its star. The New Mexico Exoplanet Spectroscopic Survey Instrument project will focus Magdalena Ridge Observatory's 2.4 meter on such exoplanets to study their atmospheres. Graphic by G. Bacon/Courtesy of NASA, ESA and the Space Telescope Science Institute.
Tech scientists will team with colleagues at the Jet Propulsion Laboratory, or JPL, at California Institute of Technology. The team will design, build and implement an infrared spectrometer at the Magdalena Ridge Observatory’s 2.4-meter telescope. The new spectrometer will be capable of assessing the atmospheres of exoplanets – planetary bodies orbiting stars outside of the solar system. The equipment will be capable of quantifying atmospheric chemistry, temperature and winds.
The Magdalena Ridge Observatory team includes physicists Michelle Creech-Eakman, Colby Jurgenson and Dave Westpfahl and microbiologist Penelope Boston. The JPL team includes Mark Swain, Gautam Vasisht, Pieter Deroo and Pin Chen.
The JPL team, led by Swain, has devised a novel approach to using infrared data from ground-based observatories to deduce information about exoplanetary atmospheres.
The team applied for the NASA grant through the state of New Mexico’s Experimental Program to Stimulate Competitive Research, or EPSCoR.
Westpfahl, the science director for the MRO, said this project is exactly the type of progress the observatory needs.
“Enough extra-solar planets have been found that there’s a whole science of comparative planetology that didn’t exist a few years ago,” he said. “When we started the MRO we couldn’t anticipate everything that would happen, but this is the kind of thing we wanted to happen.”
Jurgenson, who will be designing the instrument, said working with world-renowned scientists at the Jet Propulsion Lab is an important milestone for New Mexico Tech and an exciting opportunity for him.
“That’s one of the most appealing aspects of this project,” he said. “This is high-level science. One big challenge for us is that we’re trying to be at the forefront of this field. We have a really tight schedule. We’re pushing to get it up and running quickly so New Mexico Tech and JPL can be the first to do this.”
The next year will be spent designing the spectrometer, with installation in late 2010. The team hopes to begin gathering data by mid-2011.
As early as the 19th century, astronomers inferred the existence of exoplanets, but the first confirmed exoplanet was discovered in 1988. In the last decade, astronomers have been increasingly discovering new exoplanets orbiting nearby stars. As of July 2009, 353 exoplanets were listed in the Extrasolar Planets Encyclopedia, with more being discovered every month. This project does not aim to find new exoplanets, but will train the instruments on already discovered bodies.
An artist's rendering of an exoplanet and its star. This graphic depicts HD 189733b, an exoplanet about 63 light years from Earth. Art by C.Carreau/ Courtesy of the European Space Agency.
The New Mexico Exoplanet Spectroscopic Survey Instrument project, or NESSI, will examine exoplanets in our galaxy, mostly within 100 light years from our solar system.
“The exoplanet field of study is moving quickly,” Creech-Eakman said. “We are studying them more and more every year – pending eventual missions to explore them. The field sparks the interest of the general public. What do these worlds look like? Could these exoplanets have the sort of atmosphere that could foster or indicate life?”
The “holy grail” in the study of exoplanets is the search for an atmosphere with a chemical disequilibrium – which would be a solid indicator of potential life.
“Venus and Mars have reached atmospheric equilibrium – they are essentially ‘dead planets’,” Creech-Eakman said. “The atmosphere might be affected by solar radiation or volcanism, but it’s in a steady, stable state. They’ve had the same chemicals for hundreds or millions of years. When you add the presence of living things – whether simple like bacteria or complex like humans – we do things to change the atmosphere. We change the chemistry. Creatures from elsewhere looking at Earth would notice that we have disequilibrium chemistry.”
Creech-Eakman, Earth science professor Boston, and biologist Tom Kieft, team-teach Tech’s astrobiology course. This exoplanet survey project was partially an outgrowth of that class. Boston, who specializes in the geomicrobiology, or the study of microbial life in extreme environments, said this project will provide groundbreaking details about potential life on other planets.
“I spent more than half my life waiting for exoplanets to be confirmed,” Boston said. “And I’ve spent the past 15 years keeping track of them. I have spent my entire life thinking about life in the galaxy. So, I’m extremely excited about this.”
The physicists will interpret data to explain what state of affairs exists on the exoplanets. Boston, as a biologist, will further explain and interpret what the physicists’ discoveries.
“In my mainstream research, I go to extreme environments to see how life is functioning against the envelope as practice for thinking of life elsewhere in the galaxy,” she said. “The ability to do this on a large and distant scale is the other end of the spectrum for me.”
Boston is most interested in studying large rocky, terrestrial planets, as opposed to gas giants.
“My interest is looking at the characterization data,” she said. “The variety of extra-solar planets, how they are formed and what they’re made out of and how they compare to known planets can only inform us increasingly about our own corner of the galaxy.”
|This graphic depicts how the transit method allows astronomers to "see" exoplanets. Courtesy graphic|
Mark Swain and Gautam Vasisht at JPL were on the team that confirmed the presence of methane on an exoplanet in March 2008, using the Hubble Space Telescope. Now, they have developed a new method of interpreting spectroscopic data, using information gathered from previous projects. With this new instrument, they propose to dedicate more human and scientific resources to the examination of these exoplanets.
The study of exoplanets has truly challenged some physics models, Creech-Eakman said. Scientists are trying to understand the processes at work in alien atmospheres with different sets of parameters than we apply in our own solar system.
“We’re trying to understand a completely different world,” she said. “We cannot conceive of all the interesting chemical constituents and combinations involved.”
“Life on other planets – that’s the perfect all-encompassing scientific question,” Creech-Eakman said. “If we see planets with different chemistries, what would that change? What if we found a planet with bacterial life?”
Scientists use a handful of different methods to gather data related to exoplanets. Creech-Eakman said Swain’s team uses the “transit method” of viewing exoplanets – meaning, the scientists will train the telescope and the spectrometer on planets as they pass in front of their sun, creating a shadow and making the exoplanets atmospheres visible.
“They figured out this new technique for examining the spectra and we realized that the Magdalena Ridge Observatory 2.4-meter telescope is precisely the right sort of telescope to do it,” said Creech-Eakman, who worked at JPL with Swain and Vasisht prior to coming to New Mexico Tech. “If you have an instrument that is sensitive enough, you can gather information from backlighting the exoplanet. By looking in the infrared light, we can see molecules in the atmosphere like water and methane, which are molecules associated with life on our own planet.”
The JPL team tested this concept with other facilities and that has proven successful. The new instrument, NESSI, will be the first permanent, dedicated spectrometer of its kind. The novelty of this project involves both the instrumentation and the interpretation of the data.
“In my mind, the primary function of NESSI is to do ultraprecision spectrometry,” Jurgenson said. “So the instrument has to be very stable. That’s the biggest technical challenge.”
Creech-Eakman said many telescopes are equipped with spectrometers, but most are attached to the back of the telescope. The NESSI spectrometer will be attached to the “Nasmyth focus,” which is a stationary fork aside the telescope, thus creating a more stable setting.
The spectrometer will operate in three bands of near-infrared, the J-, H- and K-band. Direct vision prisms and a grating prism, or “grism,” will disperse incoming light into the component wavelengths of light. By dispersing incoming light, scientists can determine the chemical and molecular constituents in the exoplanet’s atmosphere. The light data will allow scientists to develop a model for the spatial distribution of these atmospheric constituents – vertically, horizontally and temporally. Over time, the data will create a picture of these alien environments.
All ground-based spectrometry of exoplanets has inherent difficulties associated with viewing through the atmosphere and looking at faint targets near bright stars. Space-based telescopes make the job easier, but getting access to the Hubble Space Telescope is highly competitive. Creech-Eakman said the JPL team has devised methods of minimizing the ambient noise associated with these types of measurements, making ground-based observation an effective new tool for this project.
“For a long time, planetary atmospheric scientists were a wholly different group than those astronomers who studied stars,” Creech-Eakman said. “Now, these people are coming together to really understand the limitations of our models; we’re updating our models and gaining a deeper understanding of what we are actually observing.”
The Magdalena Ridge Observatory’s 2.4-meter telescope became operational in late 2007 and is still soliciting customers. Creech-Eakman said the new instrument is certain to attract astronomers and physicists who are studying exoplanets.
– NMT –
By Thomas Guengerich