John Gizis
Professor, Physics and Astronomy | University of Delaware
Newark, DE, UNITED STATES
Prof. Gizis focuses his research on improving the understanding of stars and brown dwarfs (failed stars).
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Biography
John Gizis, a professor in Physics and Astronomy, focuses his research on improving understanding of stars and brown dwarfs. Gizis uses both ground-based and space-based telescopes to characterize the faint, cool objects.
Industry Expertise (1)
Aerospace
Areas of Expertise (7)
Brown Dwarfs and Binaries
Cool Stars
Stars
Solar System
Cosmology
Astronomy
Telescopes
Media Appearances (5)
Delawareans will be treated to a partial eclipse on Aug. 21
WDDE-FM Online online
2017-08-04
But while Delaware isn't on the path of totality, John Gizis, a physics and astronomy professor at the University of Delaware, says there is still something to look forward to in the First State. “Many more people will see a partial solar eclipse. Here in Delaware, the moon will cover 80 percent of the sun, which is a lot but it’s not gonna make the really dramatic thing where day turns to night,” Gizis said.
Esteemed UDel scientist Dr. Gizis talks space discoveries and aliens
The Tab online
2017-05-08
Using technologies with gamma rays, scientists are planning to check to see if any other forms of intelligent life could be sending us messages using lasers. As a dedicated professor to his University of Delaware students since 2001, Gizis agreed to sit down with The Tab and discuss his discoveries, his career, and, of course, aliens.
UD professor made historic star discovery
The News Journal online
2017-03-08
Yet, somehow, a star discovered by Gizis in 1999, nearly two decades ago, is host to not one, but seven Earth-like planetary objects, NASA recently announced. And it's only 40 light years, or 235 trillion miles, away. That's close enough that it could be captured by the Kepler Telescope — raw data from the new system is scheduled to be released later Wednesday. "I was very excited," Gizis said of the discovery. "And maybe a little bit jealous, too. Personally, it is an honor to have found something that came out in the long term."
Enlighten Me: 18 years later, UD professor's celestial discovery found as hub for 7 planets
WDDE-FM Online online
2017-03-03
But when physics and astronomy professor John Gizis discovered a red dwarf called “2MASS” in the late ‘90s (called "TRAPPIST-1" by NASA), he did not suspect there were planets orbiting the star. “We did always say that it was important to find red dwarfs because someday someone might find planets around them,” Gizis said, “but we had no idea that this particular star was special.”
23-million-year-old brown dwarf flashes brighter than the sun's most powerful flares
Phys.org online
2016-06-13
"This brown dwarf is very young by star standards—only 23 million years old," Gizis said. "It has lots of flares that are as hot as or hotter than the flares coming off full-fledged stars. This shows that the warmer brown dwarfs can generate flares from magnetic field energy just like stars. Our work shows, however, that colder brown dwarfs cannot generate flares even though they also have magnetic fields."
Articles (5)
JWST/NIRCam Discovery of the First Y+Y Brown Dwarf Binary: WISE J033605.05-014350.4
The Astrophysical Journal2023 We report the discovery of the first brown dwarf binary system with a Y dwarf primary, WISE J033605.05-014350.4, observed with NIRCam on JWST with the F150W and F480M filters. We employed an empirical point-spread function binary model to identify the companion, located at a projected separation of 0.″084, position angle of 295°, and with contrasts of 2.8 and 1.8 mag in F150W and F480M, respectively. At a distance of 10 pc based on its Spitzer parallax, and assuming a random inclination distribution, the physical separation is approximately 1 au. Evolutionary models predict for that an age of 1-5 Gyr, the companion mass is about 4-12.5 Jupiter masses around the 7.5-20 Jupiter mass primary, corresponding to a companion-to-host mass fraction of q = 0.61 ± 0.05. Under the assumption of a Keplerian orbit the period for this extreme binary is in the range of 5-9 yr. The system joins a small but growing sample of ultracool dwarf binaries with effective temperatures of a few hundreds of Kelvin. Brown dwarf binaries lie at the nexus of importance for understanding the formation mechanisms of these elusive objects, as they allow us to investigate whether the companions formed as stars or as planets in a disk around the primary.
Deep drilling in the time domain with DECam: survey characterization
Monthly Notices of the Royal Astronomical Society2023 This paper presents a new optical imaging survey of four deep drilling fields (DDFs), two Galactic and two extragalactic, with the Dark Energy Camera (DECam) on the 4-m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO). During the first year of observations in 2021, >4000 images covering 21 deg2 (seven DECam pointings), with ~40 epochs (nights) per field and 5 to 6 images per night per filter in g, r, i, and/or z have become publicly available (the proprietary period for this program is waived). We describe the real-time difference-image pipeline and how alerts are distributed to brokers via the same distribution system as the Zwicky Transient Facility (ZTF). In this paper, we focus on the two extragalactic deep fields (COSMOS and ELAIS-S1) characterizing the detected sources, and demonstrating that the survey design is effective for probing the discovery space of faint and fast variable and transient sources. We describe and make publicly available 4413 calibrated light curves based on difference-image detection photometry of transients and variables in the extragalactic fields. We also present preliminary scientific analysis regarding the Solar system small bodies, stellar flares and variables, Galactic anomaly detection, fast-rising transients and variables, supernovae, and active Galactic nuclei.
Young Stellar Objects, Accretion Disks, and Their Variability with Rubin Observatory LSST
The Astrophysical Journal Supplement Series2023 Vera C. Rubin Observatory, through the Legacy Survey of Space and Time (LSST), will allow us to derive a panchromatic view of variability in young stellar objects (YSOs) across all relevant timescales. Indeed, both short-term variability (on timescales of hours to days) and long-term variability (months to years), predominantly driven by the dynamics of accretion processes in disk-hosting YSOs, can be explored by taking advantage of the multiband filters option available in Rubin LSST, in particular the u, g, r, i filters that enable us to discriminate between photospheric stellar properties and accretion signatures. The homogeneity and depth of sky coverage that will be achieved with LSST will provide us with a unique opportunity to characterize the time evolution of disk accretion as a function of age and varying environmental conditions (e.g., field crowdedness, massive neighbors, metallicity) by targeting different star-forming regions. In this contribution to the Rubin LSST Survey Strategy Optimization Focus Issue, we discuss how implementing a dense observing cadence to explore short-term variability in YSOs represents a key complementary effort to the Wide-Fast-Deep observing mode that will be used to survey the sky over the full duration of the main survey (≈10 yr). The combination of these two modes will be vital to investigate the connection between the inner-disk dynamics and longer-term eruptive variability behaviors, such as those observed on EX Lupi-type objects.
Early Release Science of the exoplanet WASP-39b with JWST NIRCam
Nature2023 Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining the dominant chemical processes at work and, if in equilibrium, revealing planet formation histories. Transmission spectroscopy (for example, refs. 1,2) provides the necessary means by constraining the abundances of oxygen- and carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution and high precision, which, together, are not achievable with previous observatories. Now that JWST has commenced science operations, we are able to observe exoplanets at previously uncharted wavelengths and spectral resolutions. Here we report time-series observations of the transiting exoplanet WASP-39b using JWST's Near InfraRed Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength photometric light curves span 2.0-4.0 micrometres, exhibit minimal systematics and reveal well defined molecular absorption features in the planet's spectrum. Specifically, we detect gaseous water in the atmosphere and place an upper limit on the abundance of methane. The otherwise prominent carbon dioxide feature at 2.8 micrometres is largely masked by water. The best-fit chemical equilibrium models favour an atmospheric metallicity of 1-100-times solar (that is, an enrichment of elements heavier than helium relative to the Sun) and a substellar C/O ratio. The inferred high metallicity and low C/O ratio may indicate significant accretion of solid materials during planet formation (for example, refs. 3,4,) or disequilibrium processes in the upper atmosphere (for example, refs. 5,6).
Identification of carbon dioxide in an exoplanet atmosphere
Nature2023 Carbon dioxide (CO2) is a key chemical species that is found in a wide range of planetary atmospheres. In the context of exoplanets, CO2 is an indicator of the metal enrichment (that is, elements heavier than helium, also called `metallicity')1-3, and thus the formation processes of the primary atmospheres of hot gas giants4-6. It is also one of the most promising species to detect in the secondary atmospheres of terrestrial exoplanets7-9. Previous photometric measurements of transiting planets with the Spitzer Space Telescope have given hints of the presence of CO2, but have not yielded definitive detections owing to the lack of unambiguous spectroscopic identification10-12. Here we present the detection of CO2 in the atmosphere of the gas giant exoplanet WASP-39b from transmission spectroscopy observations obtained with JWST as part of the Early Release Science programme13,14. The data used in this study span 3.0-5.5 micrometres in wavelength and show a prominent CO2 absorption feature at 4.3 micrometres (26-sigma significance). The overall spectrum is well matched by one-dimensional, ten-times solar metallicity models that assume radiative-convective-thermochemical equilibrium and have moderate cloud opacity. These models predict that the atmosphere should have water, carbon monoxide and hydrogen sulfide in addition to CO2, but little methane. Furthermore, we also tentatively detect a small absorption feature near 4.0 micrometres that is not reproduced by these models.
Education (2)
Caltech: PhD, Astronomy 1997
Yale University: BS, Astronomy and Physics 1992
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Languages (1)
- English
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