Dr. Aaron Geller studies how stars and planets are born and how they change with time, both through observations and numerical simulations. In particular, he is interested in how gravitational interactions between stars and planets in star clusters shape the stellar and (exo)planetary systems that we observe. He also focusses on strange, exotic stars that don’t conform to our standard understanding of stellar evolution, and compact objects like black holes and neutron stars. In addition, Dr. Geller develops visualizations of his and others’ work for both research and outreach purposes, and for use at Northwestern, the Adler Planetarium, within classroom lessons, and for the general astronomy enthusiast.
Aaron Geller
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Gallery Contributions
Dense, swirling winds help supermassive black holes grow
Dense, swirling winds help supermassive black holes grow
By studying nearby galaxy ESO320-G030, a team of international astronomers led by CIERA Postdoctoral Fellow Mark Gorski has discovered extremely dense and powerful rotating, magnetic winds help the galaxy’s central supermassive black hole grow. This image, created by CIERA Professor Aaron Geller, depicts this phenomenon. The process is strikingly similar to the birth of new
M. D. Gorski/Aaron M. Geller
- Science
Brightest gamma-ray burst of all time came from the collapse of a massive star
Brightest gamma-ray burst of all time came from the collapse of a massive star
In October 2022, an international team of researchers, including Northwestern University astrophysicists, observed the brightest gamma-ray burst (GRB) ever recorded, GRB 221009A. In a paper published in April 2024, a team led by CIERA Postdoctoral Fellow Peter Blanchard has confirmed that the phenomenon responsible for the historic burst — dubbed the B.O.A.T. (“brightest of all time”)
Aaron M. Geller / Northwestern / CIERA / IT Research Computing and Data Services
- Science
‘Teenage galaxies’ are unusually hot, glowing with unexpected elements
‘Teenage galaxies’ are unusually hot, glowing with unexpected elements
Light from 23 distant galaxies, identified with red rectangles in the Hubble Space Telescope image at the top, were combined to capture incredibly faint emission from eight different elements, which are labelled in the JWST spectrum at the bottom. Although scientists regularly find these elements on Earth, astronomers rarely, if ever, observe many of them
Aaron M. Geller, Northwestern, CIERA + IT-RCDS
- Science
Bursts of star formation explain mysterious brightness at cosmic dawn
Bursts of star formation explain mysterious brightness at cosmic dawn
Artist conception of early starbursting galaxies. Stars and galaxies are shown in the bright white points of light, while the more diffuse dark matter and gas are shown in purples and reds. When scientists viewed the James Webb Space Telescope’s (JWST) first images of the universe’s earliest galaxies, they were shocked. The young galaxies appeared
Aaron M. Geller, Northwestern, CIERA + IT-RCDS
- Science
Unveiling the origins of merging black holes in galaxies like our own
Unveiling the origins of merging black holes in galaxies like our own
A 31.5 solar-mass black hole with an 8.38 solar-mass black hole companion viewed in front of its (computer generated) stellar nursery prior to merging. The distant band of the Milky Way can be seen toward the lower-left of the black hole pair. Light is warped nearby the black holes due to their strong gravity. The
Aaron M. Geller / Northwestern CIERA & NUIT-RCS; ESO / S. Brunier
- Science,
- Interdisciplinary,
- Data Science & Computing
Aaron Geller and Alex Gurvich showcase Firefly on AAS Journal Author Series
Aaron Geller and Alex Gurvich showcase Firefly on AAS Journal Author Series
On May 27, 2023, CIERA Research Assistant Professor Aaron Geller and former NSF Graduate Fellow Alex Gurvich were featured on the American Astronomical Society (AAS) Journal Author Series to showcase Firefly, their new browser-based interactive tool for visualizing 3D particle data sets. Geller and Gurvich were interviewed by the AAS’s Frank Timmes. Read the full news story
- Event
Firefly visualization of the ESA Gaia DR3 dataset
Firefly visualization of the ESA Gaia DR3 dataset
Firefly video visualization of data from the the European Space Agency’s (ESA) Gaia satellite. The full demo enables users to explore all 1.46 billion stars in the Gaia DR3 dataset in real time. Firefly is a browser-based interactive particle visualization app created by CIERA researchers Alex Gurvich and Aaron Geller, in a joint venture with
- Interdisciplinary,
- Outreach,
- Education,
- Data Science & Computing
Firefly visualization of the ESA Gaia DR3 dataset
Firefly visualization of the ESA Gaia DR3 dataset
Still image from a Firefly video visualization of data from the the European Space Agency’s (ESA) Gaia satellite. The full demo enables users to explore all 1.46 billion stars in the Gaia DR3 dataset in real time. Firefly is a browser-based interactive particle visualization app created by CIERA researchers Alex Gurvich and Aaron Geller, in
- Data Science & Computing,
- Interdisciplinary,
- Outreach,
- Education
Artist’s impression of GRB 211211A (Surprise kilonova upends established understanding of long gamma-ray bursts)
Artist’s impression of GRB 211211A (Surprise kilonova upends established understanding of long gamma-ray bursts)
The kilonova and gamma-ray burst is on the right. The blue color represents material squeezed along the poles, while the red colors indicate material ejected by the two inspiralling neutron stars that is now swirling around the merged object. A disk of ejecta emitted after the merger, hidden behind the red and blue ejecta, is shown in
Aaron M. Geller/Northwestern/CIERA and IT Research Computing Services
SN 2019ehk
SN 2019ehk
Artist’s interpretation of the calcium-rich supernova 2019ehk. Shown in orange is the calcium-rich material created in the explosion. Purple coloring represents gas shedded by the star right before the explosion, which then produced bright X-ray emission when the material collided with the supernova shockwave. Learn more: Calcium-rich supernova examined with X-rays for first time
Aaron M. Geller, Northwestern University
SN2016aps
SN2016aps
A supernova at least twice as bright and energetic, and likely much more massive than any yet recorded has been identified by an international team of astronomers. Continue to the full article at University of Birmingham News. View the Nature Astronomy article, “An extremely energetic supernova from a very massive star in a dense medium”
Aaron M. Geller – Northwestern IT
Masses in the Stellar Graveyard
Masses in the Stellar Graveyard
Supported Browsers: Windows: Google Chrome Mac: Google Chrome or Safari
Visualization: LIGO -Virgo / Frank Elavsky, Aaron Geller / Northwestern
- Science,
- Education
Final Flight of a Neutron Star Pair: GW170817 from Birth to Merger in Galaxy NGC 4993
Final Flight of a Neutron Star Pair: GW170817 from Birth to Merger in Galaxy NGC 4993
This video illustrates the collision of two neutron stars (GW170817).
LIGO-Virgo / Northwestern
- Education,
- Science
Final Flight of a Neutron Star Pair
Final Flight of a Neutron Star Pair
This interactive allows you to investigate possible past lives of the two neutron stars that merged in an event called GW170817 in the galaxy NGC 4993. The pair of stars—a neutron star and a normal star—orbit quietly, until the normal star undergoes a supernova, spawning a second neutron star and “kicking” the system into an elliptical orbit.
LIGO-Virgo / Aaron Geller / Northwestern
- Education,
- Science
Stellar encounters: Binary+single (exchange and collision)
Stellar encounters: Binary+single (exchange and collision)
Binary+single encounter that leads to an exchange, followed by a second binary+single encounter that leads to a collision Within star clusters, close encounters between single and multiple stars can be frequent and may lead to the production of exotic stars like X-ray sources and blue stragglers. By using the small-N-body code FEWBODY and another visualization
Movies by Aaron Geller using IDL and MPEG Streamclip; dynamical calculation performed using FEWBODY / Funding: NSF
Stellar encounters: Triple+binary (collision)
Stellar encounters: Triple+binary (collision)
Triple+binary encounter that leads to a collision Within star clusters, close encounters between single and multiple stars can be frequent and may lead to the production of exotic stars like X-ray sources and blue stragglers. By using the small-N-body code FEWBODY and another visualization software, a few visualizations of interesting stellar encounters were created. In
Movies by Aaron Geller using IDL and MPEG Streamclip; dynamical calculation performed using FEWBODY / Funding: NSF
Stellar encounters: Binary+single (collision)
Stellar encounters: Binary+single (collision)
Binary + single encounter that leads to a collision Within star clusters, close encounters between single and multiple stars can be frequent and may lead to the production of exotic stars like X-ray sources and blue stragglers. By using the small-N-body code FEWBODY and another visualization software, a few visualizations of interesting stellar encounters were
Movies by Aaron Geller using IDL and MPEG Streamclip; dynamical calculation performed using FEWBODY / Funding: NSF
Stellar Encounters: Binary+single (exchange)
Stellar Encounters: Binary+single (exchange)
Binary+single encounter that leads to an exchange Within star clusters, close encounters between single and multiple stars can be frequent and may lead to the production of exotic stars like X-ray sources and blue stragglers. By using the small-N-body code FEWBODY and another visualization software, a few visualizations of interesting stellar encounters were created. In
Movies by Aaron Geller using IDL and MPEG Streamclip; dynamical calculation performed using FEWBODY / Funding: NSF
The Late Evolution of Our Solar System
The Late Evolution of Our Solar System
This movie, Life of the Pleiades, was generated from an interactive visualization that Aaron Geller developed with Mark SubbaRao using Uniview. The interactive version can be shown on a planetarium dome, or rendered into a movie (as shown here). A 3D version of this movie exists in the Space Visualization Lab at the Adler Planetarium.
Created by A. M. Geller and M. SubbaRao, using Uniview; music, narration and audio by A. M. Geller; dynamical calculation with stellar evolution performed using the NBODY6 code.
Dynamical Evolution of Star Clusters
Dynamical Evolution of Star Clusters
This movie, Life of the Pleiades, was generated from an interactive visualization that Aaron Geller developed with Mark SubbaRao using Uniview. The interactive version can be shown on a planetarium dome, or rendered into a movie (as shown here). A 3D version of this movie exists in the Space Visualization Lab at the Adler Planetarium.
Created by A. M. Geller and M. SubbaRao, using Uniview; music, narration and audio by A. M. Geller; dynamical calculation with stellar evolution performed using the NBODY6 code.
Evolution of the Color Magnitude Diagram of a Star Cluster
Evolution of the Color Magnitude Diagram of a Star Cluster
This is a movie of the evolving color-magnitude diagram from the N-body model of the old open cluster NGC 188. Binaries are plotted with blue points, and show the combined light of the unresolved system. Single stars are plotted in black points. The dynamical and stellar evolution calculations were performed using NBODY6, with some modifications
Movie by Aaron Geller using IDL and MPEG Streamclip; dynamical and stellar evolution calculations performed with NBODY6 / Funding: NSF
When Worlds Collide
When Worlds Collide
“Hot Jupiters” are Jupiter-like planets with orbits close to their host star. Their origins are debated, and some young planetary system may even host multiple Hot Jupiters. Here, we investigate a planetary system of two Hot Jupiters orbiting a Sun-like star. The system is born on the edge of instability, and over time, the planets’
Black Hole Encounter
Black Hole Encounter
In late 2015, LIGO discovered gravitational waves emitted by two black holes (each with a mass of about 30 times that of our Sun) that spiraled together and merged about 1.5 billion years ago. Astrophysicists are now debating which is the most likely mechanism that can bring two black holes like those observed so close
Firefly Demonstration
Firefly Demonstration
Firefly is a portable web-based 3d visualization software developed in partnership between the Northwestern University Galaxy Formation and Visualization groups. It was developed with the data output of the FIRE simulations in mind but can visualize any 3d dataset (in coordinate or phase space). In this video I demonstrate some of the key features of
Aaron Geller / Alex Gurvich / Northwestern
Firefly Visualization Platform
Firefly Visualization Platform
A screenshot from Firefly, an interactive, web-based, and publicly available particle visualization platform created by Aaron Geller and Alex Gurvich. Shown here is a snapshot in time from a simulation of a Milky Way-like galaxy with the stars in blue, the gas in red, and the dark matter in yellow. In the real universe the gas
Aaron Geller / Alex Gurvich / Northwestern
Shredded Star Cluster
Shredded Star Cluster
Most stars are born together in families of hundreds to thousands, known as star clusters. Over time, the pull of gravity from the galaxy can overcome the gravitational bond holding the family of stars together, shredding the star cluster apart. In this image, the lines show the paths of individual stars in a computer model
A. M. Geller and M. SubbaRao. CIERA/Northwestern
Birth of a Solar System
Birth of a Solar System
Gas-rich “proto-planetary” disks surround young, still forming stars, feeding them through accretion of dust and gas. These are the birthplaces of planetary systems. This image shows a simulation of a possible gas disk progenitor for the real exoplanetary system HR8799. Today, HR8799 has four, six-Jupiter-mass planets, 30 million years into their lives, surrounded by a
Aaron M. Geller and A. Dempsey. Simulation performed by A. Dempsey. CIERA/Northwestern