The Newsletter of the Friends of Palomar Observatory, Vol. 17 No. 1 – June 2022

Native Americans Name Asteroid 'Ayló'chaxnim or “Venus Girl”

By Whitney Clavin

The orbits of Earth, Venus and Mercury, and 'Ayló'chaxnim. Light vertical lines illustrate the 3D orientation of each orbit relative to the main plane of the Solar System. The dots show the exact positions of planets at the time of discovery on January 4, 2020, when both 'Aylóchaxnim and Venus were in the evening sky over Palomar Mountain. (Caltech-IPAC/R. Hurt)

On 7 June 2022, members of the Pauma band (part of the Luiseño or Payómkawichum indigenous peoples) gathered at Palomar to celebrate the naming of the first known asteroid to circle entirely within the orbit of Venus. The asteroid was originally discovered in 2020 by the Zwicky Transient Facility (ZTF). Sometime after its discovery, the ZTF team decided to ask the Pauma band, whose ancestral lands include the mountainous region where the observatory is located, if they would like to bestow the new cosmic find with a name of their choosing. Ultimately, the indigenous group chose to name the asteroid 'Ayló'chaxnim, which means “Venus girl” in the Luiseño language.

Discovery data. This picture combines data from four different images obtained by Palomar's Zwicky Transient Facility at different times during the night of 4 January, 2020. Each image is assigned a different color (red, yellow, green, and blue) and then added together. The blended light of stationary stars appear white, but the single object moving through the frame—'Ayló'chaxnim—reveals itself as a series of colored dots. (NEOZTF/G. Helou)

The Palomar naming ceremony included blessings, traditional Pauma songs, and a reading of a poem titled Luiseño Songs of the Seasons, which describes how “it will soon be time for the acorns to fall from the trees” when “Venus is rising.” Jonas Zmuidzinas (BS '81), director of Caltech Optical Observatories and Caltech's Merle Kingsley Professor of Physics, addressed the Pauma band at the ceremony:

The systematic study of the night sky is actually a very ancient pursuit. It's easy to understand why—just look up on a dark, clear night, especially at a place like Palomar, and let the magnificent beauty of the night sky fill you with a sense of wonder and awe. Your ancestors, going back many thousands of years, were very skilled at studying the night sky, and used their knowledge to develop calendars, to mark the seasons, and to find their way on journeys. They recognized planets, stars, constellations, and the Milky Way, they had names for them, and told stories about the heavens that handed down their knowledge from generation to generation, much like scientists today write papers about their discoveries. The ancestors of the Pauma band were in fact the first Palomar astronomers, as our friend Ed Krupp, the Director of the Griffith Observatory in Los Angeles, noted in a paper he wrote.

Luiseño cosmogonic stories and astronomy, and the people's relationship with Palomar Mountain and surrounding land, were explored in a previous article contributed by Palomar Docent Phaedra Hopper.

Asteroid 'Ayló'chaxnim laps the Sun every 151 days while staying entirely within the orbit of Venus. It was discovered in January of 2020 by ZTF's Twilight program, which searches for asteroids at dusk or dawn that are otherwise hard to see due to their orbits close to the Sun. “An encounter with a planet probably flung the asteroid into Venus's orbit,” explained Tom Prince, the Ira S. Bowen Professor of Physics, Emeritus, at Caltech and a co-investigator of ZTF, in a previous Caltech story about the finding. If similar asteroids with orbits that fall entirely within the orbit of Venus are discovered in the future, they will belong to the 'Ayló'chaxnim family of asteroids (the official names of asteroid families derive from the name of the first object found in the class).

George Helou, a ZTF co-investigator and the director of IPAC, an astronomy center at Caltech, says the ZTF team asked the Pauma band to name the asteroid as a “celebration of their language, history, and connection to the night sky.” Patti Dixon, a Pauma band member and a professor of American Indian Studies at Palomar College outside San Diego, says she and her fellow tribe members initially wanted to name the asteroid “Venus's daughter,” but the word was too long in their native Luiseño language to be accepted by the International Astronomical Union (IAU), the official organization that assigns names to celestial bodies. Dixon said she thought the word “daughter” conveyed that the asteroid is a part of Venus, but in the end, they settled on “Venus girl,” or 'Ayló'chaxnim.

Guests of all ages toured the Hale Telescope prior to attending the main asteroid-naming event. (Palomar/Caltech)

The Pauma band, known formally as the Pauma Band of Mission, or Luiseño, Indians, is one of six tribes of native people in the San Diego area that belong to the Luiseño Indian tribe. The ancestral lands of the Luiseño peoples include Palomar Mountain, where Palomar Observatory is based. “Some of the best-tasting acorns, the black oak acorns, can only be found at the top of the mountain,” explains Dixon. “As part of our traditions, we take our burlap sacks to the mountain, gather the acorns, haul and dry them, crush and leech them, and ultimately make a Jell-O-like meal called wíiwish.” “Hunting and gathering are part of our traditions,” she says, “The movement of the stars and Venus are also parts of our traditions. Science can affirm the traditional truths but also show that science will not harm the truths.”

This is not the first time asteroids discovered at Palomar have been named in the Luiseño language. In the late 2000s Jean Mueller, a retired telescope operator who worked at Palomar for 29 years, collaborated with the Pauma band to name three asteroids she discovered (among Mueller’s many discoveries). The three asteroids named after Luiseño gods are: Tukmit (Father Sky), Tomaiyowit (Earth Mother), and Kwiila (Black Oak). A ceremony recognizing this naming was held at the observatory in April 2009.

The asteroid naming and related activities will inspire Pauma children to learn more about science, says Jessica Petri, director of the Pauma band education center. “This event will expose children to the awesome observatory in their backyard," she says.

Hale Observations in Modern Astrophysics: Compact Binaries

By Andy Boden

Continuing a thread from last year, this time I thought I’d tell you about some of the exciting work supported by Palomar observations in the field of stellar astrophysics in general, and on compact binary stars in particular.

Binary stars are remarkable:

• Binaries are prevalent (e.g. roughly 50% of solar-like stars have a gravitationally-bound stellar companion) and thus a common outcome of the star formation process,
• Astrophysically important as their component interactions lead to all kinds of remarkable behavior such as supernovae and the role they play in elemental enrichment,
• Provide a unique window into how stars work by providing a context to study their structure and function through component interactions—gravitational and otherwise.

Recently Caltech astrophysicists Tom Prince, Kevin Burdge (now at MIT), Jan van Roestel, and collaborators have led an active binary science program with Palomar telescopes. Using the Zwicky Transient Facility (ZTF) survey camera on the 48-inch Samuel Oschin Telescope (SOT), Prince and collaborators have developed novel methods (specifically crowded-field photometry) to search for variable sources in the dense starfields of the galactic plane. With these methods the team has been successful in finding rare short-period (so-called “compact”) eclipsing binary system candidates in ZTF data. These sources are “exotic” in that they are relatively rare instances of systems that exhibit novel behavior not seen in more common contexts.

Binned CHIMERA photometry of ZTF J1539+5027, phase-folded on the 6.91 minute system orbital period. The system exhibits a deep primary eclipse (where the primary is obscured by the secondary—defined as phase 0). Outside of the eclipses, there is a quasi-sinusoidal modulation because the primary star heavily irradiates one side of its companion. At phases ±0.5, the secondary eclipse occurs as the hot primary transits the irradiated face of its companion. Frames from the system animation are shown at the top aligned with the orbital phase when they occur. (Adapted from Burdge et al 2019)

Orbit period evolution for ZTF J1539+5027. Deviation of the estimated eclipse times as a function of time, compared to a system with constant orbital period is shown; the orbital period decreases with time. The inferred orbital decay is consistent with that expected from gravitational wave emission. Timing estimates prior to 2018 discovery are derived from PTF/iPTF archival photometry, and post-discovery estimates result from data obtained with CHIMERA and KPED. (Adapted from Burdge et al 2019)

Among the first notable successes for the team was the discovery of “ZTF J1539+5027”—a short-period double white dwarf binary system (Burdge et al 2019). Identified as a candidate short-period variable source in ZTF data, the system exhibits prominent primary and shallow secondary eclipses with a period of 6.91 minutes in followup high-cadence photometry with the CHIMERA camera at the Hale Telescope prime focus. Similar to the famous “Hulse-Taylor Binary Pulsar” (more on that in a minute), the system orbital period is so short that the loss of energy and angular momentum from gravitational radiation as predicted by General Relativity (GR) results in measurable changes (decreases) in the system period. Using archival Palomar Transient Factory (PTF)/SOT observations and more recent CHIMERA photometry Burdge et al 2019 showed clear evidence of system period evolution. Eventually this orbital decay will result in the merging of the two components. The ZTF J1539+5027 system represents a possible (so-called “double-degenerate”) prototype channel for supernovae Type 1a progenitors.

On background: the Hulse-Taylor Binary Pulsar (PSR J1915+1606) was discovered using the Arecibo radio telescope by R. Hulse and J. Taylor Jr. in 1974. One system component exhibits detectable radio pulses (thus a “pulsar” similar to the Crab Nebula pulsar—a magnetized spinning neutron star that emits beams of radiation from its magnetic poles). Precisely-measured pulse timing variations led Hulse and Taylor to recognize the system as a binary and infer orbital evolution as predicted by General Relativity. The observed sign of orbital decay in PSR J1915+1606 was the first convincing evidence for the existence of gravitational waves—which extract energy and angular momentum from the system orbit at discernable levels. Hulse and Taylor shared the 1993 Nobel Prize in Physics “for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation.”

A second notable success for the Caltech team is the first optical discovery of a “Black Widow” system in ZTF survey data. Burdge et al 2022 reports on the discovery of ZTF J1406+1222, a hierarchical triple system with an inner component that exhibits large (> 10X) sinusoidal flux variations with a period of 62 minutes. The team interprets the extraordinary light curve as evidence for one ZTF J1406+1222 component to be a compact, dark object such as a pulsar which heats a tidally-locked white dwarf companion. The evocative name “Black Widow” reflects the expectation that intense radiation from the pulsar that heats the white dwarf is also slowly but surely disrupting it; other Black Widow systems show signs of debris from such destruction.

Among many other scientific threads, ZTF’s ability to collect large statistical samples enables the discovery and followup study of rare stellar systems that had previously only been theorized. Such exotic systems serve as new astrophysical laboratories to study their nature and the role they play in shaping our universe. ZTF and Caltech team’s compact binary program are just one more way that Palomar remains as relevant as ever in modern astronomy.

References

1. K. B. Burdge et al (July 2019) General relativistic orbital decay in a seven-minute-orbital-period eclipsing binary system. Nature, 571(7766):528–531.
2. K. B. Burdge et al (May 2022) A 62-minute orbital period black widow binary in a wide hierarchical triple. Nature, 605(7908):41–45.
3. A. Duquennoy & M. Mayor (August 1991) Multiplicity among Solar Type Stars in the Solar Neighbourhood - Part Two - Distribution of the Orbital Elements in an Unbiased Sample, A&A, 248(2):485–524.
4. G. Hale (April 1928) The Possibilities of Large Telescopes. Harper's Magazine, 156:639–646.
5. G. Hale to H. Thorkelson (24 August 1928) on the 200-inch telescope.
6. G. Hale (9 November 1928) The Astrophysical Observatory of the California Institute of Technology. Science, 68(1767):435–437.

The Universe in Color Digital Exhibit

By Annie Mejía

William C. Miller is not a household name; even to those familiar with Palomar history the name may not ring a bell. Miller served in relative obscurity as the designated research photographer for the Hale Observatories (Mt. Wilson and Palomar). Before the wide-spread availability of Hubble Space Telescope imagery, astronomy enthusiasts embraced Miller’s pioneering natural color photographs of deep-sky objects. These images were made famous by popular magazines and astronomy books from the late 50s to the early 80s. Behind the scenes, Miller transformed our appreciation of deep-sky objects, and inspired an entire generation of astrophotographers and imaging enthusiasts.

slideshow. Click ► to start. Use < or > to reverse or advance one slide, or the progress dots to jump slides (this pauses the slideshow). Click any image to enlarge and  on some captions for extended context. Visit the Universe in Color exhibit page for more information, credits, and references.

I first became aware of and interested in investigating the first color deep-sky images, which were taken with the Palomar telescopes, when I was creating the Observatory's chronology page a handful of years ago as I came across the April 1959 Engineering and Science article “Color in the Universe.” But the person behind the project is not mentioned anywhere in the article–eventually I found Miller’s name only in the credits for the cover and article images on page 3 (the magazine’s table of contents). As time went on, I realized that about once or twice a year, we receive requests from publishers or academics seeking reproduction-quality versions of (what I now know are) Miller’s color astrophotographs. A recent request for Miller imagery to be incorporated in a mural became the tipping point for my interest in developing this digital exhibit. Quickly enough I found articles in Life and National Geographic magazines (also published in the spring of 1959) that better contextualized how extraordinary these images were at the time, to both scientists and the public.

The format of our new digital exhibits seemed like the perfect way to explore Miller’s images in context, and the result has been recently published on the Palomar website: https://sites.astro.caltech.edu/​palomar/​media/​slideshows/​deepsky.html.

“The Universe in Color” digital exhibit not only showcases many of Miller’s iconic deep-sky images, but also explores their significance as well as the technical challenges overcome by Miller in producing them. Details on Miller himself are scarce, but thanks to the Life magazine’s image archive on Google Arts and Culture, wonderful email exchanges with astrophotographer David Malin (who personally knew Miller), and the finding aid for the Miller papers at the Museum of Northern Arizona, I was able to piece together a little about the man himself.

Miller’s work led him to develop novel photographic techniques that bridged the gap between conventional photography and what we today would recognize as image processing—techniques which he shared widely and generously. Yet Miller felt unappreciated during his lifetime for his work supporting Palomar and Mt. Wilson astronomers. From my perspective Miller should be credited with giving us all a greater sense of connection to astronomy through his unprecedented photography. In this regard Miller’s work was revolutionary—transforming our perception of the cosmos with photographs that were beautiful separately from and in addition to scientifically impactful.

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Big Eye 17-1
Last updated: 13 June 2022 AFB/ACM