Comet Research Group

Our research centers on the physical and chemical behavior of comets. What processes affect the observable gas surrounding comets? How are they connected to the formation of our solar system? How do they evolve through atomic and molecular reactions? We try to answer these questions by combining telescopic observations (Hubble, Chandra, Swift), laboratory astrophysics, and in-situ exploration by planetary missions (Rosetta, Deep Impact/EPOXI, and Stardust NExT).

Swift observations of comet Lulin reveal the emission from neutral gas (blue) and the light coming from solar wind ions reacting with it.

The gas around comets is altered by sun light, by the interaction with the solar wind, and by physical and chemical reactions. Planets and comets emit X-rays through charge exchange between the solar wind and the neutral molecules in their atmospheres. We study the underlying charge exchange reactions in the lab and use telescopes like XMM-Newton, NICER on the ISS, and the Chandra X-ray Observatory to remotely study the plasma environments of comets.

Rosetta observations of comet 67P/Churyumov-Gerasimenko revealed that under certain conditions, electron impact reactions can be the most important reactions in the coma. We collaborate with the Comenius University in Bratislava (Slovakia) to characterize these reactions. A major goal of our project is to determine how to use the emission from electron collisions to study gases in comets and the atmospheres of other small bodies, such as Europa.

Cometary activity changes as active areas on the surface rotate in and out of sunlight. This variability is caused by changes in the distribution of sunlight as the comet rotates (diurnal variation) and orbits the sun (seasonal variation and evolution). Using telescopes such as the Discovery Channel Telescope, the Neil Gehrels-Swift observatory, and Spitzer, we study the variability of cometary activity to explore the evolution and chemical heterogeneity of their nuclei.

Comet outburst can be spectacular, turning a modestly active comet into a naked eye object. Rosetta observations suggest mini-outburst may occur on a daily basis. We use the Zwicky Transient Facility (ZTF) to systematically monitor all observable comets in the Northern sky. ZTF will be an early warning system for comet outbursts. Using rapid-follow up telescopes such as the Las Cumbres Observatory and the Neil Gehrels-Swift observatory we investigate where in comets’ orbits outbursts occur, the frequency and duration of outbursts, and determine the composition of the ejected material.

Our group has been involved in three missions to comets: Deep Impact/EPOXI, which flew by comet 103P/Hartley 2; Stardust-NExT to comet 9P/Tempel 1; and Rosetta, which orbited 67P/Churyumov-Gerasimenko for over two years. Dennis Bodewits was a co-investigator on Rosetta's OSIRIS camera system and lead the investigation of the gases imaged in its coma.

Dennis Bodewits is also a co-investigator on the CAESAR mission study, which NASA considered for their New Frontiers Program. The mission intended to return over 100 grams of comet material from the surface of 67P to Earth by 2038.

Team Members

Dr. Dennis Bodewits (Associate Professor)

Dennis Bodewits is an associate professor of Physics at Auburn University. Born in Hoogezand-Sappemeer, the Netherlands, I studied experimental physics and astronomy at the University of Groningen. I got my Ph.D. after writing a dissertation on charge exchange emission from solar wind ions interacting with cometary atmospheres at the Center for Advanced Radiation Technology (KVI-CART) at the University of Groningen. Being awarded a NASA Postdoctoral Program fellowship I moved to Washington DC and started observing comets and asteroids with the Swift space telescope at the Goddard Space Flight Center. Between 2010 and 2018 I was a member of the Small Body Group at the University of Maryland, where I got involved in the comet fly-bys of the Deep Impact and Stardust-NEXT missions, and in the Rosetta mission that orbited comet 67P/Churyumov-Gerasimenko for over two years. I joined the Physics Department at Auburn University in 2018. The IAU honored me by assigning asteroid 10033 the formal name 'Bodewits' in 2017. Fun fact: I am one out of a dozen people who ever flew a man-powered helicopter (the University of Maryland’s Gamera II).

Dr. Emamnuele Bonamente (Postdoctoral Scientist)

During my academic career, I moved from high-energy astrophysics, where I obtained a first PhD in γ-ray astronomy with the Fermi observatory searching for dark matter emission, to zero-energy environmental engineering, where I obtained a second PhD focusing in renewable sources for energy efficiency and mitigation of global warming before being appointed assistant professor in applied and environmental physics.

My deep interest and motivation in understanding the physics governing what surrounds us, and especially that beyond unknown processes, led me to this new adventure in the field of cometary science. I am trying to understand the details of the mechanisms triggering high-energy (X-rays) emission from comets as an effect of the interactions with the highly-charged ions emitted by the sun, which represents a direct monitor of the solar wind and an experimental investigation of not yet well understood atomic processes, and UV-optical emission produced when comets are exposed to intense sunlight, which helps us understanding the conditions in which these primordial objects formed.

Dr. Steve Bromley (Postdoctoral Scientist)

In 2015 I moved to Clemson in South Carolina, intending to become a high-energy astronomer. I instead found myself developing an interest in the atomic physics underpinning astronomy. In my graduate work, I worked in the Marler Group at Clemson University developing methods and apparatus’ for studying charge exchange (CX) with highly charged ions (HCIs). This experimental work piqued my interest as I was involved in every step of the process from experimental conception to design, testing, and ultimate use to measure atomic properties. In the latter half of my PhD work, I became involved with a new collaboration to study emission spectra of heavy elements relevant to neutron star merger ejecta. This effort will continue in my postdoctoral work as we extend our experiments and analysis to other heavy elements.

As a postdoc, my research goals are to understand the role of atomic collisions in exotic environments, including both neutron star merger ejecta and the interface between the solar wind and cometary nuclei. For the latter, I will be studying electron-molecule collisions to extract cross sections, line ratios, and other diagnostics for understanding the thin plasmas around comets. Additionally, I will be working alongside collaborators at Clemson University to bring a Cold Target Ion Momentum Spectroscopy (COLTRIMS) on-line at the Clemson University Electron Beam Ion Trap (CUEBIT). This work will produce nl-resolved CX cross sections for many HCIs present in the solar wind. It is expected that these measurements will resolve standing issues within the literature, including uncertainties in diagnostic line ratios and the proper energy regimes of various CX emission models.

In my spare time, I frequent mountain bike trails as often as the weather permits, and won’t hesitate to photograph a great view!

Dr. Kumar Venkataramani (Postdoctoral Scientist)

I am a post-doctoral scientist in the physics department, Auburn University. I was born and brought up in the city of Mumbai, India. I have always been a night-sky enthusiast right from schooling days in Mumbai. I completed my PhD in physics from Indian Institute of Technology, Gandhinagar. All of my research work was carried out at Physical Research Laboratory, Ahmedabad, India. My PhD thesis work was to study the gas and dust abundances in various comets as a function of their distance from Sun. This was done by monitoring and measuring the amount of emissions from various molecular and ionic species seen in the optical spectrum of the comets. My research work included observing comets and asteroids using ground based telescopes.

As a post doctoral researcher, I am involved in the project to study comet 9P/Tempel 1. The images of this comet were aquired using the comet specific narrow band filters in the medium resolution instrument of the Deep Impact Spacecraft. I will also be involved in projects to study some of the other comets in the UV region of their spectra, where we see a lot more emissions from different molecules in the coma.

Apart from research, I really like to travel and explore new places. Its pretty exciting to learn about different cultures and to understand the way in which people think about various aspects of life. I am also a nature admirer and I love animals (especially cats).

Thomas Deskins (Graduate Student)

My name is Thomas Deskins and I am a Ph.D. student in the department of physics at Auburn University. Born and raised in Baltimore in the state of Maryland, I earned a bachelor’s degree (2017) and a master’s degree (2018) in chemical and biomolecular engineering from the University of Maryland, College Park.

My previous research has been on modeling atmospheric emissions of volatile chemicals and performing numerical simulations of microfluidic transport processes. After earning my master’s degree, I moved to Beijing to teach at an international boarding school. After a year, I returned to the United States to begin graduate studies in physics at Auburn University. I joined Dr. Dennis Bodewits’ research group in April 2020. I am currently using data from the European Space Agency’s XMM-Newton, an X-ray space observatory, to investigate the X-ray emissions of comets.

Aside from research and other scholarly things, I enjoy playing guitar, woodworking, hiking, and gardening.

Shawn Oset (Graduate Student)

I am a phD student here at Auburn University working in astrophysics. After earning degrees from the University of South Alabama in Physics and Mathematics, I developed a heavy interest in computation and its interaction with physics.

A love of science fiction and all things space-related brought me to my current field studying cometary phenomena after a short time in theoretical condensed matter physics, studying the properties of half-metals and related magnetic materials for applications in spintronics.

In my free time I enjoy cooking, trying new foods, learning as many languages as I can, programming, and reading. I like animals, especially horses and dogs, and being outside in general.

Zexi Xing (Visiting Graduate Student)

Zexi Xing is a Ph.D. student in the department of physics at the University of Hong Kong. I have a general interest in physics, especially astrophysics, and currently focus on Ultraviolet and X-ray observations of comets and asteroids. Abundance, activities and history of the small bodies are intriguing for me. The Neil Gehrels Swift Observatory is my great friend. In 2018 I got my B.Sc. in astronomy from Nanjing University, where many plane trees and cats live pretty happily. In addition to research, I am a great fan of nature and street photography, I love running outdoors with music, I love taking planes, and I really love dogs!

News and Press

Hubble observations reveal the origins of interstellar comet Borisov

April 20th, 2020 | Our team led observations of interstellar comet 2I/Borisov with the Hubble Space Telescope and discovered that it is unexpectedly rich in carbon monoxide. These results, published in Nature Astronomy today, can be used to infer where and how it was formed.

Welcome Kumar Venkataramani and Emanuele Bonamente!

Jan 15, 2020 | I am happy to announce that Drs. Kumar Venkataramani and Emanuele Bonamente joined the group as postdoctoral scientists.

Kumar's main research interest is the observational study of comets and asteroids. The key research goal during his PhD was to investigate the molecular abundances in comets and to study the coma morphology using the techniques of spectroscopy and narrow band imaging using various telescopes in India, his home country. Projects he will work on at Auburn University include the 46P/Wirtanen campaign and narrow band images acquired by the Deep Impact mission to comets Tempel 1 and Hartley 2.

Emanuele holds PhD's in both High Energy Astrophysics and Energy Engineering from the University of Perugia, Italy. At Auburn University, he will work on X-ray observations of solar wind charge exchange in comets, and on spectroscopic observations of comets and asteroids with the X-ray and Ultraviolet-Optical Telescopes on the Neil Gehrels-Swift observatory.

New paper: Electron impact on water molecules

November 12, 2019 | Rosetta discovered that under certain conditions, electron impact reactions drive reactions and the emission of light from the inner coma. To better understand these processes and to be able to use them to study comets and small bodies such as Europa, we collaborated with the Comenius University in Bratislava, Slovak Republic. There, we conducted experiments to measure the exact fingerprint of reactions between electrons and water vapour. When water molecules are struck by electrons of sufficient energy, they fragment into many excited pieces (OH, OH+, H2O+, H, ..), all of which can emit light at near-UV and optical wavelengths. The results are summarized in this paper that appears today in the Astrophsyical Journal.

Welcome Zexi (Lucy) Xing!

October 1st, 2019 | Zexi Xing will join my group at Auburn University as a visiting scholar for six months between October 2019 - April 2020.

Zexi is an expert in observations of comets in Ultraviolet and X-ray wavelenghts. She got her B.Sc. in astronomy from Nanjing University in 2018, and is currently a graduate student at Hong Kong University. Zexi will work on observations by the Neil Gehrels-Swift observatory of comets and asteroids. Welcome Zexi!

2019 Annual Auburn University Duncan lecture about 'Water in our solar system'

April 18, 2019 | The famous “Pale Blue Dot” photo taken of Earth as just a single pixel from almost four billion miles away by the Voyager spacecraft signifes the importance of water and how it covers more than 70 percent of our planet. This water is essential for life on our planet. We now know that there is or was water on many places in the solar system – including, Mars, moons, asteroids, and comets. Hear directly from Auburn University’s Dr. Dennis Bodewits, an astrophysicist who recently spent two days using the Hubble Space Telescope and other leading facilities around the world to conduct research on Comet 46P/Wirtanen. He will share the study of the origins and the fascinating history of water in our solar system.

This year’s lecture will also feature artwork based on photos taken from the Rosetta spacecraft painted in 30 - 40 layers to achieve a specifc, unique texture to represent water. Ekaterina Smirnova, a Seattle-based artist, will share her insight about how science inspires her artwork. Until April 19, her artwork will be on display in the Grand Gallery at the Jule Collins Smith Museum of Fine Art.

Chandra guest blog on Comet X-ray observations

Jan 3, 2019 | I wrote a guest blog about cometary X-ray observations for the website of the Chandra X-ray observatory.

Close approach of Comet 46P/Wirtanen: a space mission in reverse!

Dec 7, 2018 | On December 16th, comet 46P/Wirtanen will make an historically close approach to Earth passing within 30 Lunar distances (11.5 million km). We have organized a large observing campaign that includes Chandra, Hubble , the Neil Gehrels-Swift Telescopeand the Las Cumbres Observatory. These telescopes will study the comet's rotation, chemical composition, and its interaction with the solar wind.

Hubble Space Telescope observations of Comet 46P/Wirtanen

Nov. 12, 2018 | Our team of Rosetta scientists have been awarded over two days on the Hubble Space Telescope to study the chemical composition of Comet 46P/Wirtanen, and atomic and molecular reactions near its nucleus and to use the comet as a natural laboratory to study plasma processes.

The unique close proximity of 46P allows us to study the inner part of the coma (within 150 km of the nucleus), a region rarely accessible to remote observations. These observations will allow us to detect the emission of short-lived species (such as S2, O2), of molecules not accessible from the ground (CO2), and to investigate the transitions between regions where either electrons or photons drive most of the chemistry in the coma. Because the comet is so close to Earth, we can compare the HST observations directly with the results of the Rosetta and Deep Impact missions to comets.

Guest experiments at Comenius University (Slovakia) in support of Rosetta

Sep. 10, 2018 | Rosetta surprisinly found that collisions with electrons were the most important reaction in the gas surrounding comet 67P. These reactions provide a fingerprint of the gases in the coma but may also be used to detect faint traces of gas around comets, asteroids, and moons in the solar system.

Together with Juraj Orszagh and Stefan Matejcik from the Comenius University in Bratislava, Slovakia, I am characterizing the probability of these reactions and of the emission they produce in optical and far-ultraviolet wavelengths. Preliminary results will be presented at the meeting of the AAS' Division of Planetary Sciences meeting in Knoxville, TN.

Rosetta reveals that rugged landscape forms jets

May 23, 2018 | The atmosphere of Rosetta’s comet 67P/Churyumov-Gerasimenko is far from homogeneous. In addition to sudden outbursts of gas and dust, daily recurring phenomena at sunrise can be observed. In these, evaporating gas and entrained dust are concentrated to form jet-like structures.

A new study, led by the Max Planck Institute for Solar System Research (MPS) in Germany and published in the journal Nature Astronomy, now identifies the rugged, duck-shaped structure of the comet as the main cause of these jets. Not only do concave regions collimate gas and dust emissions similar to an optical lens, the complex topography also provide some areas of the surface with more sunlight than others. (more)

Abrupt slow down in the rotation of comet 41P

Jan. 10, 2018 | Combining observations from Swift and Discovery Channel telescope we measured an unprecedented change in the rotation of a comet. Images taken in May 2017 reveal that comet 41P/Tuttle-Giacobini-Kresák was spinning three times slower than it was in March, when it was observed by the Discovery Channel Telescope at Lowell Observatory in Arizona. The results were published in Nature.

CAESAR comet sample return mission selected for Phase A development

Dec. 20, 2017 | Two University of Maryland astronomers will make key contributions to one of two final concepts that NASA selected for further development under its New Frontiers program.

If selected for deployment, the Comet Astrobiology Exploration Sample Return (CAESAR) mission will seek to retrieve primitive material from comet 67P/Churyumov-Gerasimenko. Comet 67P made headlines as the target of the European Space Agency’s Rosetta spacecraft mission, which orbited the comet from 2014 through 2016.

Dennis Bodewits and Michael Kelley, both associate research scientists in the UMD Department of Astronomy, will lead the Comet Environment Working Group for the CAESAR team. In this role, they will assess the risks that the comet’s harsh surface environment would pose to the spacecraft and will help define the technical requirements for the sample acquisition system (more) .

First light for Zwicky Transient Facility

Nov. 14, 2017 | A new robotic camera with the ability to capture dozens of comets and asteroids every night has taken its first image of the sky—an event astronomers refer to as "first light." The camera is the centerpiece of a new automated sky survey project called the Zwicky Transient Facility (ZTF), based at Caltech's Palomar Observatory near San Diego, California. I am part of a team that uses ZTF to monitor comet activity and looks for outbursts. (more).

Electrons make comet gas glow

Nov. 1, 2016 | The Rosetta spacecraft arrived at comet 67P/Churyumov-Gerasimenko in the summer of 2014. Using its OSIRIS cameras, we found that the comet was more than 100 times brighter than expected based on our models. It turns out that the conditions for 67P, far from the Sun, when the comet's activity was very low, were very different from those normally observed from Earth. In these conditions electron impact collisions produce much more light than reactions with Sun light. We published our results in the Astronomical Journal.