for Research and Education
The Thacher Observatory is a small telescope observatory located on the campus of The Thacher School in Ventura County, California, with a legacy of astronomy research that dates back to the late 1950’s. In 2016, the observatory was renovated and converted into a fully automated, research-grade facility. The low-elevation site is bordered by the Los Padres National Forest and therefore affords dark to very dark skies allowing for accurate and precise photometric observations. The education and research goals of the Thacher Observatory go hand in hand as our mission is to engage in meaningful and relevant astronomical research as a means for learning physics, astronomy, and programming while also providing a motivating force that encourages students to strive for excellence, build practical skills, engage in equitable collaboration, and hone our ability to communicate in a professional setting.
Location: 34° 28' 0.5'' W119° 10' 38.5''
Elevation: 1623' (494.7 m)
Telescope primary mirror diameter: 0.7m
Filter set: g, r, i, z, Johnson-V, [SII], [OIII], H-alpha
Camera: Andor iKON-L 936 BV
CCD: e2v back-illuminated 2048 x 2048, 13.5µm pixels
FOV: 20.8' x 20.8'
Plate Scale: 0.608''/pixel
Median seeing: ~2.8''
Sky brightness: ≤ 22 mags/sq. arcsec in V
Zeropoint magnitudes: 22.0 (g), 21.7 (V), 21.9 (r), 21.3 (I), 20.0 (z)
The Thacher Observatory specializes in accurate and precise photometry in the visible (470nm to 1µm) part of the spectrum. We have in-house expertise in the fields of exoplanets, low-mass stars, and planet and star formation. However, our facility is a powerful tool for all transient astronomical phenomena, and with the help of our collaborators, we have been able to make significant contributions to fields as wide-ranging as gravitational wave sources and supernovae.
LOW-MASS STARS AND THEIR PLANETS
Low-mass stars—often referred to as "red dwarfs" or "M-dwarfs"—comprise 75% of all stars in our Galaxy. However, not one red-dwarf is visible to the unaided eye. It is now known that low-mass stars harbor on average at least 2 planets per star, amounting to a staggering number of planets, many of which are likely habitable! Since an accurate characterization of an exoplanet depends on an accurate characterization of the host star, a large motivating factor for the study of low-mass stars is to understand the planet populations around them. Thacher Observatory measures the light variations in low-mass eclipsing stellar systems as a means of measuring the basic properties of stars.
Image credit: Artist’s impression of Earth-sized planets orbiting a red dwarf star. Image credit: NASA, ESA, and G.Bacon (STScI).
With facilities like PanSTARRS, the Zwicky Transient Facility, and ASAS-SN, tens of thousands of supernovae are discovered every year. This places a large burden on follow-up facilities to track, characterize, and draw scientifically meaningful conclusions about these cosmic explosions. Our facility is nicely poised to respond quickly to transient events and provide long term monitoring of interesting objects.
Image credit: The brightness of Type Ia supernova SN2020hvf over the course of a few months. Unpublished data produced by Thacher's Astronomy Researchers.
Having complete control of a research-grade observatory offers the flexibility to do long-term monitoring of astronomical sources that vary in brightness over time. This program began with our work on Boyajian's Star—which continues today—and has now expanded to include other variable stars and active galactic nuclei. Our typical cadence is nightly. However, we have the capability to monitor astronomical sources on various time scales as the scientific objectives require.
Image credit: Artist's impression of one possible explanation for the chaotic changes in brightness seen toward Boyajian's Star: a swarm of comets [NASA/JPL-Caltech]
TESS FOLLOW-UP OBSERVING PROGRAM (TFOP -SG1)
Expanding upon the Kepler and K2 missions, NASA's Transiting Exoplanet Survey Satellite (TESS) aims to create a catalog of thousands of exoplanets using the transit method, which looks for periodic dips in star brightness, suggesting the potential presence of an exoplanet. The Thacher Observatory is one of many facilities that contribute ground-based follow-up observations of specified targets to confirm true exoplanets and rule out false positives. An example of our data is shown to the right, which can be used with other information to measure the radius, mass and composition of the distant worlds.
Image credit: Brightness of the star XO-2 as a function of time in two photometric bands showing the signature dipping indicative of an exoplanet eclipsing its host star. Unpublished data produced by Thacher's Astronomy Researchers.
NEARBY SUPERNOVA SEARCH
Studies of distance Type Ia supernova have shown that the expansion rate of the universe is accelerating. These intriguing explosions are useful standard candles as they are extraordinarily bright, relatively common, and occur in galaxies for which a recessional velocity can be observed. However, most Type Ia supernovae discovered are very far away where they are hard to characterize and understand. Thacher hopes to add scientifically valuable Type Ia supernovae to the present sample by monitoring 1300 nearby galaxies waiting for one of these explosions to occur. Catching these explosions early is key to understanding how to calibrate their intrinsic luminosities. While we have not yet been the first to discover a nearby supernova, we have detected multiple supernovae allowing us to confirm the viability of this ongoing program. Currently, the Thacher Observatory Supernova Search (TOSS) has obtained more than 14,000 images of 500 different galaxies, and we are currently working on a home-grown image recognition machine-learning algorithm to autonomously identify candidate supernovae in our data.
Image credit: One example of the automated supernova searching algorithms used by the Thacher Observatory which subtract a template image from a new image to look for residual point sources. This example shows the real detection of a new supernova.
This is a complete, chronological list of refereed publications associated with the Thacher Observatory.
Kilpatrick, C. et al. (Yang, G. & Swift, J. J. co-authors), 2023. Type II-P supernova progenitor star initial masses and SN 2020jfo: direct detection, light-curve properties, nebular spectroscopy, and local environment. MNRAS, 524, 2161.
Singh, M. (DiLullo, N., Scheer, J., Swift, J. J., Yang, G. & Zhou, H. co-authors), 2023. Observational properties of a bright type Iax SN 2018cni and a faint type Iax SN 2020kyg. arXiv.
Wang, Q. (DiLullo, N., Swift, J. J., & Yang, G. co-authors) 2023. Flight of the Bumblebee: the Early Excess Flux of Type Ia Supernova 2023bee revealed by TESS, Swift and Young Supernova Experiment Observations, arXiv.
Hosseinzadeh, G. (Leung, C., Swift, J. J. & Yang, G. co-authors) 2022. Weak Mass Loss from the Red Supergiant Progenitor of the Type II SN 2021yja. ApJ, 935, 24
Swift, J. J.; Andersen, K.; Arculli, T.; Browning, O.; Ding, J;. Edwards, N,.; Fanning, T.; Geyer, J.; Huber, G.; Jin-Ngo, D.; Kelliher, B.; Kirkpatrick, C.; Kirkpatrick, L.; Klink, D.; Lavine, C.; Lawrence, G.; Lawrence, Y.; Leung, F-L. C.; Luebbers, J.; Myles, J.; O'Neill, T.; Osuna, J.; Phipps, P.; Rahman, G.; Rosenbaum, T.; Stacey, H.; Stacey, P.; Tang, H.; Wood, A.; Wilcox, A.; Vyhnal, C. R.; Yang, G.; Yim, J.; Yin, Y.; Zhang, J. (and 6 co-authors) 2022. The Renovated Thacher Observatory and First Science Results. PASP, 134, 1033.
Dimitriadis. G. et al. (Swift, J. J. as part of the Young Supernova Experiement) 2022. A Carbon/Oxygen-dominated Atmosphere Days After Explosion for the "Super-Chandrasekhar" Type Ia SN 2020esm. ApJ, 927, 78.
Gagliano, A. et al. (Stacey, H. & Swift, J. J. as part of the Young Supernova Experiment) 2022. An Early-Time Optical and Ultraviolet Excess in the type-Ic SN 2020oi. ApJ, 924, 55
Tinyanont, S. et al. (Swift, J. J. as member of Young Supernova Experiment) 2022. Progenitor and close-in circumstellar medium of type II supernova 2020fqv from high-cadence photometry and ultra-rapid UV spectroscopy. MNRAS, 512, 2777.
Kilpatrick, C. et al. (Swift, J. J. as member of Gravity Collective) 2021. The Gravity Collective: A Search for the Electromagnetic Counterpart to the Neutron Star-Black Hole Merger GW190814. ApJ, 923, 258.
Barna, B. et al. (Swift, J. J., Stacey, H., & Rahman, M. 23rd) 2021. SN 2019muj - a well-observed Type Iax supernova that bridges the luminosity gap of the class. MNRAS, 501, 1078.
Jacobsen-Galán, W. et al. (Rahman, M, Stacey, H., & Swift, J. J. 23rd) 2020. SN 2019ehk: A Double-peaked Ca-rich Transient with Luminous X-Ray Emission and Shock-ionized Spectral Features. ApJ, 898, 166.
Swift, J. J., Yin, Y. et al. 2019. LIGO/Virgo S190814bv: no counterpart candidates in Thacher imaging. GCN Circular, No. 25351.
Swift, J. J., Yin, Y. et al. 2019. LIGO/Virgo S190720a: Thacher Observatory follow-up observations. GCN Circular, No. 25147.
Han, E., Muirhead, P. & Swift, J. J. 2019. Magnetic Inflation and Stellar Mass. IV. Four Low-mass Kepler Eclipsing Binaries Consistent with Non-magnetic Stellar Evolutionary Models. AJ, 158, 19.
Wilson, M. et al. (Lawrence, G., Leubbers, J. & Swift, J. J. 15th) 2019. First radial velocity results from the MINiature Exoplanet Radial Velocity Array (MINERVA). PASP, 131, 5001.
Healy, B. et al. (Swift, J. J. 7th), 2019. Magnetic Inflation and Stellar Mass. III. Revised Parameters for the Component Stars of NSVS 07394765. AJ, 158, 89.
Vyhnal, C. & Swift, J. J. 2018. A Century of Astronomy at The Thacher School. Robotic Telescopes, Student Research and Education (RTSRE) Conference Proceedings, San Diego, California, Jun 18-21, 2017. vol 1, p. 65.
Boyajian, T. et al. (Edwards, N & Swift, J. J. nth) 2018. The First Post-Kepler Brightness Dips of KIC 8462852. ApJ, 853, 8.
Swift, J. J. & Vyhnal, C. 2018. The Astronomy Program at the Thacher School. Robotic Telescopes, Student Research and Education (RTSRE) Conference Proceedings, San Diego, California, Jun 18-21, vol. 1, p. 281.
Han, E., Muirhead, P., Swift, J., et al. 2017. Magnetic Inflation and Stellar Mass. I. Revised Parameters for the Component Stars of the Kepler Low-mass Eclipsing Binary T-Cyg1-12664. AJ, 150, 100.
Mann, A. et al. (Swift, J. J. 8th) 2017. The Gold Standard: Accurate Stellar and Planetary Parameters for Eight Kepler M Dwarf Systems Enabled by Parallaxes. AJ, 153, 267.
Vanderburg, A. et al. (Swift, J. J. 5th) 2016. Radial velocity planet detection biases at the stellar rotational period. MNRAS, 459, 3565.
Swift, J. J. et al. 2015. Characterizing the Cool KOIs. VIII. Parameters of the Planets Orbiting Kepler’s Coolest Dwarfs. ApJS, 218, 26.
This is a complete, chronological list of professional conferences attended by students and faculty of the Thacher Astronomy Research Program. Each name is linked to their contribution to the conference if available.
In attendance: Heldridge, E., Zhou, H., McGawn, B., Gudebski, T. & Swift, J. J.
In attendance: Swift, J. J., Vyhnal, C. R., Meyer, K., Klink, D., Osuna, N., & Sondland, M.
- Thu, Mar 04Mar 04, 2021, 6:30 PM – 7:30 PMMar 04, 2021, 6:30 PM – 7:30 PMMeet us on the Upper Field to learn about our new eVscope, look at some deep sky objects and talk about becoming an Astronomy Ambassador, getting involved in the Astronomy Program, summer opportunities in astronomy, and more. Bring layers for warmth, and bring a headlamp that has a red light setting
- Mon, Nov 23Nov 23, 2020, 1:20 PMNov 23, 2020, 1:20 PMThe Astronomy Research students put together professional style research proposal presentations that will be used to guide the research they conduct for the rest of the year. Presentations can be viewed at these links: https://tinyurl.com/y6chks5x and https://tinyurl.com/y455oxhy
- Fri, Oct 30Oct 30, 2020, 8:30 PM – 9:30 PMOct 30, 2020, 8:30 PM – 9:30 PMExplore the sky with the Observatory Heads and Dr. Swift. Activities will include sky viewing through our telescope, orienting ourselves in the cosmos, and an astrophotography workshop. Unfortunately, due to COVID, this event is only open to the Thacher community.