A Rogue World, Not A Failed Star
A Rogue World, not a Failed Star
At the scientific conference Cool Stars 22 hosted on the UC San Diego campus, there were numerous talks about stellar and substellar research. The last session on Friday was titled Brown Dwarfs and Giant Exoplanets: Future Prospects and Thirty Years of Discovery. The first talk was an invited review by Davy Kirkpatrick, a prolific brown dwarf researcher that has enabled my own research and the work of others. It was an overview starting from the discovery era into the characterization era we are in right now thanks to JWST.
I appreciated him openly saying that brown dwarf researchers need to stop letting people refer to brown dwarfs as "failed stars" and be careful when talking to media. This is crucial because brown dwarfs are not a typical astrophysical object people are exposed to. Many people know what galaxies, planets, and asteroids are and these objects have been repeatedly depicted in science fiction for decades. Many people may not have an image in their mind when they read the phrase "brown dwarf".
A brown dwarf is a Jupiter-sized (sized in radius, not mass) object that is mainly hydrogen and helium gas. Brown dwarfs are not massive enough to fuse hydrogen for energy like stars, but some of the most massive brown dwarfs can still fuse deuterium. They start out with whatever heat they were born with and cool down slowly over time. Brown dwarfs range in temperature from about 4400 to 35° C ( 2700 to 280 Kelvin). This temperature range extends from the bottom tail of the coolest stars to average room temperature. Such a massive spread in temperature leads to a large variety in the types of gases and clouds we see within their atmospheres.
Brown dwarfs are unique and dynamic worlds that exist outside of the context of not being able to fuse hydrogen like stars. Astronomers commonly see water vapor, methane, carbon monoxide, ammonia, or carbon dioxide in their atmospheres. Some warm brown dwarfs have clouds with sand-like material and the coldest ones could potentially host water clouds like the ones we see on Earth. Brown dwarfs even have weather. These objects are very successful at repeatedly challenging our understanding of how atmospheric chemistry works.
In my own head, I frequently imagine brown dwarfs as planet-like worlds. Essentially Jupiter with a different, but cooler color scheme. Maybe with less cloud coverage for the hottest brown dwarfs. I wonder what it would be like to live in a society among the cloud decks or even orbiting around a brown dwarf. If those beings had vision, they would very likely need to see in the infrared given the absence of a host star.
While doing my own work I would like to romanticize brown dwarfs a bit more and get back in touch with the wonder that led me to the field in the first place. One way I'm hoping to do that is by participating as an advisory board member for the in development planetarium show Rogue Objects. The planetarium show is being developed by Janani Balasubramanian who is an artist in residence with the Brown Dwarf New York City Research Group. I had an absolutely wonderful time chatting with them last year about what we thought brown dwarfs looked like and how they related to the everyday experiences of people.
More Posts from Infraredastronomy and Others
A History of Black Futures
This week I gave an invited talk at NASA Goddard and took a day to visit the Afrofuturism exhibit at the National Museum of African American History and Culture. I picked up the book inspired by this exhibit a year ago during an NYC trip and have been itching to go since.
This specific display in the photo made me tear up. From left to right it shows the flight suit of Trayvon Martin, the flight suit of Lieutenant Uhura from Star Trek, and the flight suit of astronaut and former administrator of NASA Charles Bolden. Three scenarios: A future taken away, a future imagined, and a future that has been realized. When Trayvon Martin was killed by George Zimmerman, he also took away his ability to be creative, curious, and explore the world around him.
“Out of the mountain of despair, a stone of hope”
Top: Cathedral of St. Augustine
Bottom: Piece from Juan Obando and Yoshua Okón: DEMO
The Importance of Deuterium
Deuterium is an isotope of hydrogen with one extra proton. The ratio of deuterium to hydrogen (D/H) is an indicator of mass in isolated substellar objects. Brown dwarfs that have more than 12 times the mass of Jupiter are theoretically warm enough to fuse deuterium, causing smaller atmospheric D/H ratios. In Solar System objects the D/H ratio can be altered by temperature, material transport, or atmospheric escape. In Rowland+ 2024 (accepted ApJL), we were able to detect deuterium for the first time outside of our solar system in WISE 0855, the coldest known brown dwarf.
The overall D/H ratio is inferred by detecting both deuterated methane (CH3D) and normal methane (CH4) in the atmosphere of WISE 0855. From the data we also estimate that WISE 0855 has two times more mass than Jupiter. Both the deueterium abundance and mass are consistent with theoretical expectations. Deuterium is not exclusive to gravitationally bound companions and can be used to infer mass in both brown dwarfs and exoplanets. I was super excited to be apart of this paper and also previous work demonstrating we could detect CH3D is most cold brown dwarfs.
LBT/NOMIC spectroscopy
NOMIC is one of the infrared cameras within the Large Binocular Telescope Interferometer. It is primarily used to take images at 8-13 microns. When NOMIC was built, a low resolution grism was installed within one of the filter wheels. Last Fall I was finally able to test it on sky to see how it performed. Lambda Persei is a relatively bright star with a spectral type of A0, similar to Vega. The NOMIC spectrum of Lambda Persei is shown in blue with black error bars. A spectrum of Vega from Rieke+ 2008 is shown in red. They match pretty well besides the region between 9.5 and 10 microns. This is likely due to the telluric calibrator star being observed at a very different air mass than the target. Getting a good telluric calibrator beyond 8 microns is very challenging for ground-based observations. A significant chunk of stars are too dim to get high signal-to-noise in a short period of time relative to the time required for science observations.
Reflections
I recently adopted a cat and have named him Lorenzo. At the shelter he was kind of a mean ass cat. Now that he lives as a solo cat I'm seeing a really soft side of him and it warms my heart. I also recently submitted an instrument concept for the Gemini Strategic Planning community input. Not entirely sure where that will go, but I'm proud that I put myself out there with my team.
