Comet Research Group

Auburn Comet 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).

Expand the boxes below for more details on our research activities.
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 Chandra 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 are developing an experimental set up at Auburn to investigate electron impact dissociation processes, and we collaborate with the Comenius University in Bratislava (Slovakia) to characterize the light emitted when these reactions occur. 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 Hubble Space Telescope and the Neil Gehrels-Swift observatory 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.

News and Press

Steve Bromley wins the 2022 Lab-astro dissertation prize of the American Astronomical Society!

Feb 25, 2022 | Congratulations to Steve for winning the American Astronomical Society's Laboratory Astrophysics Dissertation prize! His dissertation, 'Atomic data needs in laboratory astrophysics: experimental methods for spectroscopy and charge exchange with ions' earned him a PHD from Clemson University in 2020. It descibres the design of a gas cell developed for measuring absolute cross sections of charge exchange reactions, and the results of guest experiments done at Auburn to characterize the spectrum of gold atoms and ions. From the citation: "Dr. Bromley’s research is at the intersection of plasma physics and high-energy laboratory astrophysics. Applying a variety of experimental techniques, his groundbreaking laboratory measurements on the spectra of Au I and Au II generated critical data for our understanding of heavy metal formation in neutron star mergers. "

Welcome Mohi Saki

July 7, 2021 | We are happy to announce that Dr. Mohi Saki has joined the comet research group. Mohi got his Ph. D. degree from the Missouri University of Science and Technology in St. Louis, MO for his studies the molecular composition of comets using ground-based telescopes such as NASA's Infrared Telescope Facility and the W. M. Keck observatory.

Projects he will work on at Auburn include the storage and release of volatiles in cometary nuclei, and ground breaking observations of small bodies using the James Webb Space Telescope.

Johannes Allen awarded 2021 Auburn University research fellowship

May 31, 2021 | Johannes Allen has won a AU undergraduate research fellowship to investigate Hubble Space Telescope observations of an outburst of comet 29P/Schwassmann-Wachmann 1.

Iron and nickel vapors present in most comets?

May 19, 2021 | The detection of iron and nickel vapours in a broad range of Solar System comets, and of nickel vapour in a comet from outside the Solar System, provides a glimpse into the organic chemistry of young planetary systems.

Dennis Bodewits and Steve Bromley wrote a Nature 'News and Views' summary about the implications of this discovery. Temperatures on the surfaces of cometary nuclei are too low to sublimate nickel and iron grains directly, indicating there must be some chemical intermediate - possibly carbonyls or polycyclic aromatic hydrocarbons.

Thomas Deskins secures observing time with the NICER X-ray telescope on the Space Station

March 02, 2021 | Graduate student Thomas Deskins succesfully lead a proposal to use the NICER X-ray telescope mounted on the International Space Station to observe two comets previously visited by space craft, 19P/Borrelly and 67P/Churyumov-Gerasimenko. Deskins will research interactions between the solar wind, a plasma emitted by the sun, and the two comets.

Read more about Thomas' experience in this online profile .

English translation of Haser's 1957 paper on the distribution of fragment species in the coma

Dec. 23, 2020 | The mathematical model for the distribution of fragment molecules such as OH in cometary atmospheres was first described in a classic paper by L. Haser in 1957. Unfortunately, this paper is hard to find and written in French. Auburn graduate student Shawn Oset translated the paper into English and it is now publicly available in The Planetary Science Journal. The paper was part of the special issue dedicated to the late Mike A'Hearn.

New paper: How can we study comets around other stars?

Oct. 20th, 2020 | Exocomets are comets orbiting around other stars. We have studied thousands of comets around the Sun, and visited a handful of them with planetary missions. How can we extend what we know about our comets to exocomets? What observational techniques could we use to learn what these exocomets are made of? These questions are discussed in a review paper in the Publications of the Astronomical Society of the Pacific, along with an overview of our current understanding about small bodies around other stars.

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.

NASA recently included this work as an historic highlight in the interactive Hubble History Timeline.

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 our 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.

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. John Noonan (Visiting Research Scholar)

I completed my bachelor's degree in astrophysics and planetary sciences from the University of Colorado, Boulder in 2016, graduating summa cum laude with an honors thesis investigating UV comet emissions. Following undergrad I worked for the Southwest Research Institute as an analyst for the Alice UVS and flight controller for NASA's Cyclone Global Navigation Satellite System (CYGNSS), ultimately starting my Ph.D. at the Lunar and Planetary Laboratory at the University of Arizona in 2017.

My Ph.D. work focuses heavily on the UV emissions of comets, whether observed from the European Space Agency's Rosetta spacecraft by the Alice instrument or by the Hubble Space Telescope. These emissions are essentially impossible to observe from any ground-based observatory due to the Earth's atmosphere's ozone layer, and are thus more difficult to obtain and often more poorly understood, especially during periods of high activity.

As a visiting research scholar with the Comet Research Group I'll be continuing this investigation of UV comet emissions, working on a comprehensive examination of all Alice and OSIRIS data to analyze trends in emission mechanisms, analyzing HST observations of both comets and their more enigmatic progenitors the Centaurs, and developing more accessible software for the generation of fluorescence efficiencies for atoms, molecules, and ions. Outside of academics I also race bikes, road and cyclocross, to keep my adrenaline up and stay in shape to balance out my other hobby, cooking.

Dr. Youssef Moulane (Postdoctoral Scientist)

In 2013, I got my bachelor degree in physics and a master's degree in astrophysics at Cadi Ayyad university (Morocco). For my Master’s thesis, I worked on the automatic detection of moving objects, including asteroids and comets, based on a data acquired with Oukaimeden Observatory. In this context, I started my PhD in , studying comets using TRAPPIST telescopes.

For my PhD work at both Cadi Ayyad University and the University of Liege (Belgium), I used the two robotic TRAPPIST telescopes to monitor bright comets. These telescopes are equipped with narrow-band cometary filters that allow us to record images of a comet at wavelengths where the light is emitted by the main gaseous species. I used these photometric data to derive the physical and chemical properties of the observed comet sample. During this time, I visited Le Havre University (France) to study collisions of electrons and molecular cations, and obtained a 2-year studentship at ESO (Chile) to work on optical spectroscopy of comets observed with the VLT.

As a postdoctoral researcher, I will be working on Deep Impact data to study comet 9P/Tempel 1 using narrow-band filters. I will also be involved in a project to study comet 29P/S-W with space telescopes, including Swift and Hubble, to understand its activity behavior and the possible mechanism of its large outbursts. Apart from research, I like doing astronomy outreach activities. I like doing sports, running, biking, swimming and gym activities. I like to travel and explore new places.

Dr. Mohi Saki (Postdoctoral Scientist)

I studied the behavior of molecules and ions in atomic mass spectrometers for my first master’s degree at the Amir Kabir University of Technology (Tehran Polytechnic). In 2015, I joined the Astronomy team at the University of Missouri, St. Louis to study comets and received my second master’s degree in Astrophysics in 2017. I received my Ph.D. from Missouri University of Science and Technology in 2021.

For my Ph.D. dissertation, I studied the chemical composition of long-period and short-period comets observed in the near infrared wavelength (~ 1-5 microns) in order to enhance our understanding of solar system formation. These comets are among the most pristine remnants of solar system formation time, so any opportunity to study them could be of a potential high impact. For this, I used the near infrared spectrographs such as iSHELL at the 3m NASA Infrared Telescope Facility (NASA-IRTF) and NIRSPEC 2 at the 10 m W. M. Keck II observatory both located on top of Mauna Kea, Hawaii.

I have more than 10 years of teaching experience from high school to college physics courses. I joined the Auburn comet research team to continue comet studies in a different range of wavelength (UV and Optical) using the best space-based telescopes in the world such as Hubble, James Webb Space Telescope (JWST), and Swift. Aside from Physics and Astronomy, I enjoy swimming and scuba diving for fun.

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!

  • Publications
  • 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!

    Undergraduate Students

      Rachel Fulda (Physics/Photography), Multiwavelength observations of comets

      Johannes Allen (Physics/Aerospace Eng.), HST observations of the aftermath of an outburst of 29P/Schwassmann-Wachmann 1

      Jacob Duffy (Physics/Computer Science), Neutral density distribution around comets

      Tanner Finlay (Physics/Computer Science), X-ray spectra of highly charged ions


Dr. Emanuele Bonamente, Postdoctoral Fellow (2020), X-ray observations of comets

Dr. Kumar Venkataramani, Postdoctoral Fellow (2020-2022), HST and Deep Impact observations of comets

Lauren Lyons (Software Eng.), Undergraduate Researcher, Modeling of the distribution of fragment species in cometary atmospheres

Valory (Val) Green (Physics/Education), Undergraduate Researcher, Cometary X-rays


Applications of Quantum Mechanics (PHYS 5100/6100)

Quantum mechanics allows us to understand atoms and nuclei, but also how stars work and formed the elements. It allowed us to discover the laser, the atomic clock, and the silicon chip. It explains the structure and strength of neutron stars and a block of copper at the same time.

This course covers the experimental and theoretical foundation of quantum mechanics. It includes applications in fields such as astronomy, nuclear physics, and solid state physics. It is intended for undergraduate and graduate students that have taken at least one introductory quantum mechanics course.

Astrobiology (PHYS 3500)

Astrobiology is an interdisciplinary field that asks profound scientific questions. How did life originate on the Earth? How has life persisted on the Earth for over three billion years? Is there life elsewhere in the Universe? What is the future of life on Earth?

The course will introduce the structure of living things, the formation of the elements for life in the Universe, the biological and geological history of the Earth and the habitability of other planets in our own Solar System and beyond. It includes subjects from astronomy, biology, atmospheric science, chemistry, and planetary science.

Honors Physics 1 (PHYS 1607)

This course will introduce you to the laws of physics governing the motion of objects. Topics include kinematics, laws of motion, energy, collisions and rotational motion. We will also discuss gravity, fluids, oscillation, and wave motion.