From Caltech: “The Shape of Star Explosions”

Caltech Logo

From Caltech

March 11, 2021
Whitney Clavin
(626) 395‑1944

Caltech Palomar 200 inch Hale Telescope, Altitude 1,713 m (5,620 ft), located in San Diego County, California, U.S.A.

New polarization instrument at Palomar Observatory delivers first results.

When massive stars end their lives in fiery explosions called supernovae, their ashes fly outward to form expanding clouds of debris. While these clouds may look roughly spherical, astronomers think that star explosions are in fact lopsided events in which different amounts of material shoot outward in different directions.

Three-Dimensional Core-Collapse Supernova (highest resolution).

Now, astronomers have a new tool to better understand the asymmetrical shapes of supernova explosions, and thus how stars explode in the first place. An instrument called “WIRC+Pol,” located at Caltech’s 200-inch Hale Telescope at Palomar Observatory, has delivered its first science results, which show that a supernova called SN 2018hna exploded in a shape more like an ellipse than a sphere, similar to the well-studied supernova remnant called SN 1987A.

The WIRC+Pol instrument in the 200-inch Hale dome at Palomar. Credit: K. Tinyanont/Caltech.

“We believe all supernovae explode asymmetrically but we need an instrument like this to confirm that theory and to teach us more about how stars explode as well as the environments they explode into,” says Samaporn (Kaew) Tinyanont (MS ’17, PhD ’20), lead author of a new study reporting the findings in the journal Nature Astronomy. Tinyanont helped commission the WIRC+Pol instrument as part of his PhD thesis. His advisors were Caltech astronomy professors Mansi Kasliwal (MS ’07, PhD ’11) and Dimitri Mawet; Mawet is also affiliated with NASA-JPL/Caltech(US), which is managed by Caltech for the National Aeronautics and Space Administration(US).

WIRC+Pol, which was designed to study brown dwarfs and supernovae, is an adaptation of a previous instrument that operated at Palomar called the Wide-Field Infrared Camera. With these modifications, WIRC+Pol now has the ability to capture spectra of polarized light, hence its name. When light from a supernova explosion scatters off the supernova’s debris clouds, that light can become polarized, which means that some of the light waves become oriented in the same direction. The more asymmetrical the explosion, the more the light will be polarized. Thus, the degree of the light’s polarization, as measured from Earth, can be used to determine the shape of the explosion.

WIRC+Pol employs a thin sheet of liquid crystal polymer called polarization grating to split infrared light from an object into different polarization signals. Infrared light works better than optical light in polarization instruments because infrared light is not blocked by dust that causes contaminating polarization signatures. The infrared light beams with different polarization signals are simultaneously further split into different wavelengths to create the spectra. The efficiency of the new polarization grating is much higher compared with traditional gratings used previously. WIRC+Pol is the first instrument that employs a polarization grating on a large telescope, and the first with the sensitivity to observe supernovae.

“The vast majority of supernovae that are not in our own Milky Way and the nearby Magellanic Clouds are so far away that they appear as a point in our images even with the highest power telescopes. Polarization allows us to infer the shape of these supernovae.”

See the full article here.

Please help promote STEM in your local schools.

Stem Education Coalition

The California Institute of Technology(US) is a private research university in Pasadena, California. The university is known for its strength in science and engineering, and is one among a small group of institutes of technology in the United States which is primarily devoted to the instruction of pure and applied sciences.

Caltech was founded as a preparatory and vocational school by Amos G. Throop in 1891 and began attracting influential scientists such as George Ellery Hale, Arthur Amos Noyes, and Robert Andrews Millikan in the early 20th century. The vocational and preparatory schools were disbanded and spun off in 1910 and the college assumed its present name in 1920. In 1934, Caltech was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration (US)’s Jet Propulsion Laboratory, which Caltech continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

Caltech has six academic divisions with strong emphasis on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. First-year students are required to live on campus, and 95% of undergraduates remain in the on-campus House System at Caltech. Although Caltech has a strong tradition of practical jokes and pranks, student life is governed by an honor code which allows faculty to assign take-home examinations. The Caltech Beavers compete in 13 intercollegiate sports in the NCAA Division III’s Southern California Intercollegiate Athletic Conference (SCIAC).

As of October 2020, there are 76 Nobel laureates who have been affiliated with Caltech, including 40 alumni and faculty members (41 prizes, with chemist Linus Pauling being the only individual in history to win two unshared prizes). In addition, 4 Fields Medalists and 6 Turing Award winners have been affiliated with Caltech. There are 8 Crafoord Laureates and 56 non-emeritus faculty members (as well as many emeritus faculty members) who have been elected to one of the United States National Academies. Four Chief Scientists of the U.S. Air Force and 71 have won the United States National Medal of Science or Technology. Numerous faculty members are associated with the Howard Hughes Medical Institute(US) as well as National Aeronautics and Space Administration(US). According to a 2015 Pomona College(US) study, Caltech ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.


Caltech is classified among “R1: Doctoral Universities – Very High Research Activity”. Caltech was elected to the Association of American Universities in 1934 and remains a research university with “very high” research activity, primarily in STEM fields. The largest federal agencies contributing to research are National Aeronautics and Space Administration(US); National Science Foundation(US); Department of Health and Human Services(US); Department of Defense(US), and Department of Energy(US).

In 2005, Caltech had 739,000 square feet (68,700 m^2) dedicated to research: 330,000 square feet (30,700 m^2) to physical sciences, 163,000 square feet (15,100 m^2) to engineering, and 160,000 square feet (14,900 m^2) to biological sciences.

In addition to managing JPL, Caltech also operates the Caltech Palomar Observatory(US); the Owens Valley Radio Observatory(US);the Caltech Submillimeter Observatory(US); the W. M. Keck Observatory at the Mauna Kea Observatory(US); the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Richland, Washington; and Kerckhoff Marine Laboratory(US) in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at Caltech in 2006; the Keck Institute for Space Studies in 2008; and is also the current home for the Einstein Papers Project. The Spitzer Science Center(US), part of the Infrared Processing and Analysis Center(US) located on the Caltech campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

Caltech partnered with University of California at Los Angeles(US) to establish a Joint Center for Translational Medicine (UCLA-Caltech JCTM), which conducts experimental research into clinical applications, including the diagnosis and treatment of diseases such as cancer.

Caltech operates several Total Carbon Column Observing Network(US) stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

Caltech campus