## From The California Institute of Technology: “Mathematically Percolating”

From The California Institute of Technology

8.5.22

Tom Hutchcroft explains why phase transitions in percolation models are so fascinating. Credit: Caltech.

These images show three different phases in a percolation model: before, at, and beyond the critical phase transition. As the probability of an edge being blue, or p, goes up (from left to right), it becomes easier for the blue portions to spread across the grid. At the point of the phase transition (middle), fractal-like clusters emerge that take long, meandering paths across the grid. Credit: Nils Berglund.

When water flows through a bed of ground espresso beans, ultimately resulting in a delicious latte, the water is undergoing a process called percolation. The water slowly meanders through the coffee at just the right rate to extract the rich coffee flavors. In general, percolation refers to liquids filtering through a porous medium. The process can describe not only the generation of lattes, but also a host of other phenomena, such as how diseases spread and even physics concepts such as magnetism.

For mathematicians like Tom Hutchcroft, who joined the Caltech faculty last year as a professor of mathematics, the most interesting aspect of percolation is what happens during a phase transition, the point where an abrupt qualitive change in the system occurs. “You only change one factor in the system a tiny bit, and then you get a big change,” he says. A classical phase transition occurs when water freezes.

In mathematical percolation models, phase transitions can result in “really interesting mathematical behavior,” according to Hutchcroft, including fractal patterns; fractal refers to self-similar patterns seen at different scales.

Hutchcroft is studying how the geometry of fractal trees like the one depicted here change when viewed in different dimensions.

Hutchcroft, who was born and raised in England, earned his bachelor’s degree in mathematics from Cambridge University in 2013 and his PhD in mathematics from the University of British Columbia, Canada, in 2017. He held internships at Microsoft Research Theory Group during his graduate studies, and later completed postdoctoral fellowships at University of Cambridge from 2017 to 2021.

We met with Hutchcroft over Zoom to learn more about the math of percolation and what he is enjoying about Caltech so far.

What does percolation have to do with the spread of a disease?

Percolation theory is a way of describing clustered components in random networks and can be applied to complex things like the spread of an infection through a population. Systems like these have phase transitions. With epidemics, there’s a critical point or phase transition called “R nought,” or R0. This value depends on the average number of people that an infected person infects. When R nought is below 1, the epidemic will die out; when it’s above 1, it will grow exponentially. When R is exactly 1, the infection will die out but very slowly. When you look at this point in models, you tend to have a lot of mathematically interesting behavior. And when you use branching, tree-like models for epidemics, which are a form of a percolation model, you’ll get some interesting fractal geometry in the tree. This has been well understood since the 1990s. But even though you are doing something very simple, you get really mathematically rich objects coming out at the end.

How do mathematicians study these percolation models?

While physicists and other scientists may study the statistical physics or statistical mechanics of similar systems as a means to explain the behavior of the components, we mathematicians are interested in the pure math, which can be very complex and interesting. In general, we draw out grids, with edges and nodes, where the edges connect the nodes. These are the percolation models that explain how liquid can flow through a porous media. Imagine that for each edge of this grid, you flip a coin that has a probability “p” of being heads. If the coin comes out heads, you keep the edge, and if it comes out tails, you delete the edge.

When p is small, or the probability of keeping an edge is small, you will end up with small clusters of connections that are like small islands that don’t connect to anything else. When p is greater than the critical parameter at which a phase transition occurs, called pc [pronounced pee-cee], you will get one big, connected cluster. When p is exactly equal to pc, we expect to get large, fractal-like clusters that permeate across the grid but do so in a zero-density way, with extremely long, tortuous paths.

So, if this model were explaining coffee percolation, then when p is less than pc, the water would not get through the coffee—it would get stuck in the islands of small clusters. When p is larger than pc, the water would readily flow through. When p is equal to pc, at the phase transition, the water would slowly meander through the grinds, which is what you would want for a good cup of espresso.

If you look at the connections between the nodes at this phase transition and under different scales you will start to see the fractal and winding math.

What problems are you working on in this field?

The two-dimensional models are very well understood and even models with 100 dimensions are easier to understand. But the three- four- and five-dimensional cases are extremely hard to study. One thing I’m working on is trying to crack the three-dimensional problem. The most basic question is to figure out if the phase transition occurs with a jump-what we call discontinuous-or more smoothy-what we call continuous. This problem has been open for a really long time and needs to be solved before we can move on to understanding all the cool fractal stuff that should be happening at the phase transition. I’m also working on other related problems, such as long-range percolation where the probability of two nodes having an edge between them depends on the distance between the nodes. Changing how this probability falls off with the distance has a surprisingly similar effect to changing the dimension of the grid and lets us treat the dimension like a continuous parameter.

What do you love about working on these math problems?

A lot of the appeal for me is that it’s fun. When you get a good problem, you get hooked on it. Math is like the king of all puzzle games, but it goes beyond puzzles in that you the solution is very insightful. You not only solve the problem, but you build new conceptual frameworks for understanding other math problems.

How do you like Caltech so far?

One of the things that drew me to Caltech was the small class size. It feels less like lecturing and more like doing a seminar where you get to interact with everyone individually. I like the tight community here. Of course, the small size of Caltech can mean less interaction with mathematical peers, but a lot of that is going to be balanced out by the fact that the American Institute of Mathematics is moving its headquarters to Caltech. That’s going to bring a lot more activity here, and people will be passing through regularly.

I also like the mountains in the Pasadena area, which we don’t have back home in the UK. We’ve been going out hiking. You can look at a mountain on campus and then get in the car and be there in 15 minutes.

Anything else you’d like to add?

Since coming to Caltech, I’ve also set up the LA Probability Forum, a monthly mini-conference for the LA-area probability community, so that I get to regularly interact with my colleagues at UCLA and USC, and anyone else who would like to be involved. This has been really enriching for me both scientifically and socially.

Stem Education Coalition

Caltech campus

The The California Institute of Technology 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.

The California Institute of Technology 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, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology 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 The California Institute of Technology. Although The California Institute of Technology 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 The California Institute of Technology 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 The California Institute of Technology, 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 The California Institute of Technology. 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 as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology 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; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology 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 NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology 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, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles 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.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

## From The California Institute of Technology Via “Science Alert (AU)” : “Incredible ‘Shrinking’ Planets Could Be a Missing Link Between Worlds”

From The California Institute of Technology

Via

5 AUGUST 2022
MICHELLE STARR

The discovery of multiple exoplanets that appear to be shrinking appears to resolve a ‘missing link’ in planetary evolution.

Artist’s impression of a shrinking exoplanet. (M. Kornmesser/NASA/ESA/Hubble.

Four mini-Neptunes in close proximity to their stars have been found leaking their atmospheres at a rate consistent with eventual total loss. This suggests that these worlds will eventually shrink into terrestrial, roughly Earth-sized planets – and moreover, it’s the fault of their stars that they will do so.

Although scientists have long thought that these two types of exoplanets were linked, the pathway by which the mini-Neptunes lost their atmospheres was unknown.

While other mechanisms might still be at play, the newly identified shrinking worlds suggests that stripping by way of stellar irradiation is a leading one.

The Milky Way galaxy is a big, diverse place, and there are many kinds of exoplanets that have been identified to date that are very different from what we find in our own Solar System. One of those is the mini-Neptune – the most common kind of world detected by the Kepler mission, but notably absent from our own little corner of the galaxy.

These are worlds that are more massive than Earth, and less massive than Neptune, but still shrouded in a Neptune-like thick atmosphere of hydrogen and helium. Interestingly, these exoplanets seem to get no smaller than around twice the radius of Earth.

Super-Earths are the next category down, exoplanets that are between 1 and 1.5 times the radius of Earth. Between around 1.5 and 2 Earth radii, there’s a curious gap in which exoplanets are extremely scarce. This is known as the small planet radius gap.

Scientists believe that this gap exists because, above a certain critical limit, exoplanets have enough mass to retain a substantial primordial atmosphere that inflates their size, putting them in the class of mini-Neptunes. Super-Earths, on the other hand, don’t have enough mass, and either lost their primordial atmospheres, or never had them to start with.

The next question is then if these exoplanets started out with primordial atmospheres, how did they get lost?

One potential pathway, called core-powered mass loss, is the internal heat resulting from planetary formation, in which gravitational binding energy is converted into heat that ejects the primordial atmosphere. The other is called photoevaporation, in which intense X-ray and ultraviolet irradiation from the young star strips away the exoplanet’s atmosphere.

Determining which of these scenarios leads the transformation of mini-Neptunes into super-Earths requires observing leaking exoplanets, and determining the rate at which they are losing mass.

This brings us back to a new paper, from a team of researchers led by astronomer Michael Zhang of the California Institute of Technology (Caltech). They used spectroscopy to study the atmospheres of four young, nearby mini-Neptunes orbiting orange dwarf stars, to determine the rate at which these exoplanets are leaking helium into space.

These four mini-Neptunes include one called TOI 560b, which has a radius 2.8 times that of Earth’s, the analysis of which was published by Zhang and his colleagues earlier this year.

The other three are new: TOI 1430.01, at 2.1 times the size of Earth; TOI 1683.01, at 2.3 times the size of Earth; and TOI 2076b, at 2.52 times the size of Earth.

All four planets had significant helium outflows, the team found, at a rate consistent with photoevaporation, rather than core-powered mass loss. In addition, this loss rate is sufficient to strip the atmospheres of these exoplanets in just a few hundred million years, the team found – that’s a pretty short timescale in cosmic contexts.

The team says their findings suggest that most mini-Neptunes orbiting Sun-like stars probably turn into super-Earths, and do so via photoevaporation.

“We conclude that many, if not all, of these planets will lose their hydrogen-rich envelopes and become super-Earths,” Zhang and colleagues write in their paper, which awaits peer review.

“Our results demonstrate that most mini-Neptunes orbiting Sun-like stars have primordial atmospheres, and that photoevaporation is an efficient mechanism for stripping these atmospheres and transforming these planets into super-Earths.”

The research has been submitted to The Astronomical Journal.

Stem Education Coalition

Caltech campus

The The California Institute of Technology 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.

The California Institute of Technology 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, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology 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 The California Institute of Technology. Although The California Institute of Technology 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 The California Institute of Technology 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 The California Institute of Technology, 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 The California Institute of Technology. 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 as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology 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; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology 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 NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology 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, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles 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.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

## From The California Institute of Technology: “New Optical Switch Could Lead to Ultrafast All-Optical Signal Processing”

From The California Institute of Technology

7.29.22
Robert Perkins
(626) 395‑1862
rperkins@caltech.edu

An artist’s illustration of an optical switch, splitting light pulses based on their energies. Credit: Y. Wang, N. Thu, and S. Zhou.

Engineers at Caltech have developed a switch—one of the most fundamental components of computing—using optical, rather than electronic, components. The development could aid efforts to achieve ultrafast all-optical signal processing and computing.

Optical devices have the capacity to transmit signals far faster than electrical devices by using pulses of light rather than electrical signals. That is why modern devices often employ optics to send data; for example, think of the fiberoptic cables that provide much faster internet speeds than conventional Ethernet cables.

The field of optics has the potential to revolutionize computing by doing more, at faster speeds, and with less power. However, one of the major limitations of optics-based systems at present is that, at a certain point, they still need to have electronics-based transistors to efficiently process the data.

Now, using the power of optical nonlinearity (more on that later), a team led by Alireza Marandi, assistant professor of electrical engineering and applied physics at Caltech, has created an all-optical switch. Such a switch could eventually enable data processing using photons. The research was published in the journal Nature Photonics [below] on July 28, 2022.

Switches are among the simplest components of a computer. A signal comes into the switch and, depending on certain conditions, the switch either allows the signal to move forward or halts it. That on/off property is the foundation of logic gates and binary computation, and is what digital transistors were designed to accomplish. However, until this new work, achieving the same function with light has proved difficult. Unlike electrons in transistors, which can strongly affect each other’s flow and thereby cause “switching,” photons usually do not easily interact with each other.

Two things made the breakthrough possible: the material Marandi’s team used, and the way in which they used it. First, they chose a crystalline material known as lithium niobate, a combination of niobium, lithium, and oxygen that does not occur in nature but has, over the past 50 years, proven essential to the field of optics. The material is inherently nonlinear: Because of the special way the atoms are arranged in the crystal, the optical signals that it produces as outputs are not proportional to the input signals.

While lithium niobate crystals have been used in optics for decades, more recently, advances in nanofabrication techniques have enabled Marandi and his team to create lithium niobate-based integrated photonic devices that allow for the confinement of light in a tiny space. The smaller the space, the greater the intensity of light with the same amount of power. As a result, the pulses of light carrying information through such an optical system could provide a stronger nonlinear response than would otherwise be possible.

Marandi and his colleagues also confined the light temporally. Essentially, they decreased the duration of light pulses, and used a specific design that would keep the pulses short as they propagate through the device, which resulted in each pulse having higher peak power.

The combined effect of these two tactics—the spatiotemporal confinement of light—is to substantially enhance the strength of nonlinearity for a given pulse energy, which means the photons now affect each other much more strongly.

The net result is the creation of a nonlinear splitter in which the light pulses are routed to two different outputs based on their energies, which enables switching to occur in less than 50 femtoseconds (a femtosecond is a quadrillionth of a second). By comparison, state-of-the-art electronic switches take tens of picoseconds (a picosecond is a trillionth of a second), a difference of many orders of magnitude.

Science paper:
Nature Photonics

Stem Education Coalition

Caltech campus

The The California Institute of Technology 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.

The California Institute of Technology 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, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology 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 The California Institute of Technology. Although The California Institute of Technology 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 The California Institute of Technology 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 The California Institute of Technology, 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 The California Institute of Technology. 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 as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology 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; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology 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 NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology 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, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles 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.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

## From The California Institute of Technology: “An Ocean of Galaxies Awaits”

From The California Institute of Technology

July 13, 2022
Whitney Clavin
(626) 395‑1944
wclavin@caltech.edu

New COMAP radio survey will peer beneath the “tip of the iceberg” of galaxies to unveil a hidden era of star formation.

Sometime around 400 million years after the birth of our universe, the first stars began to form. The universe’s so-called dark ages came to an end and a new light-filled era began.

More and more galaxies began to take shape and served as factories for churning out new stars, a process that reached a peak about 4 billion years after the Big Bang.

Luckily for astronomers, this bygone era can be observed. Distant light takes time to reach us, and our telescopes can pick up light emitted by galaxies and stars billions of years ago (our universe is 13.8 billion years old). But the details of this chapter in our universe’s history are murky since most of the stars being formed are faint and hidden by dust.

A new Caltech project, called COMAP (CO Mapping Array Project), will offer us a new glimpse into this epoch of galaxy assembly, helping to answer questions about what really caused the universe’s rapid increase in the production of stars.

“Most instruments might see the tip of an iceberg when looking at galaxies from this period,” says Kieran Cleary, the project’s principal investigator and the associate director of Caltech’s Owens Valley Radio Observatory (OVRO). “But COMAP will see what lies underneath, hidden from view.”

The current phase of the project uses a 10.4-meter “Leighton” radio dish at OVRO to study the most common kinds of star-forming galaxies spread across space and time, including those that are too difficult to view in other ways because they are too faint or hidden by dust. The radio observations trace the raw material from which stars are made: cold hydrogen gas. This gas is not easy to pinpoint directly, so instead COMAP measures bright radio signals from carbon monoxide (CO) gas, which is always present along with the hydrogen. COMAP’s radio camera is the most powerful ever built to detect these radio signals.

Based on observations taken one year into a planned five-year survey, COMAP set upper limits on how much cold gas must be present in galaxies at the epoch being studied, including the ones that are normally too faint and dusty to see. While the project has not yet made a direct detection of the CO signal, these early results demonstrate that it is on track to do so by the end of the initial five-year survey and ultimately will paint the most comprehensive picture yet of the universe’s history of star formation.

“Looking to the future of the project, we aim to use this technique to successively look further and further back in time,” Cleary says. “Starting 4 billion years after the Big Bang, we will keep pushing back in time until we reach the epoch of the first stars and galaxies, a couple of billion years earlier.”

Anthony Readhead, the co-principal investigator and the Robinson Professor of Astronomy, Emeritus, says that COMAP will see not only the first epoch of stars and galaxies, but also their epic decline. “We will observe star formation rising and falling like an ocean tide,” he says.

COMAP works by capturing blurry radio images of clusters of galaxies over cosmic time rather than sharp images of individual galaxies. This blurriness enables the astronomers to efficiently catch all the radio light coming from a larger pool of galaxies, even the faintest and dustiest ones that have never been seen.

“In this way, we can find the average properties of typical, faint galaxies without needing to know very precisely where any individual galaxy is located,” explains Cleary. “This is like finding the temperature of a large volume of water using a thermometer rather than analyzing the motions of the individual water molecules.”

The project has received funding from the Keck Institute for Space Studies (for critical early technology development) and from the National Science Foundation (NSF), for building the “Pathfinder” early phase of the project and performing the survey. The project is a collaboration between Caltech; the Jet Propulsion Laboratory (JPL), which is managed by Caltech for NASA; New York University; Princeton University; Stanford University; Université de Genève; University of Oslo; The University of Manchester; University of Maryland; University of Miami; and the University of Toronto (including the Canadian Institute for Theoretical Astrophysics and the Dunlap Institute for Astronomy and Astrophysics).

Science paper:
The first science results from the project have just been published in seven papers in The Astrophysical Journal. The collaboration’s Early Science Paper I provides an overview of the current findings in The Astrophysical Journal.

From Early Science Paper I The Astrophysical Journal
Left: a simulated 2.5 deg2 field showing galaxy positions in gray (adapted from Kovetz et al. 2017). Center: simulated CO intensity map of the same field in a slice of 40 MHz bandwidth, corresponding to a redshift interval Δz = 0.004. The VLA would take about 4500 hr to cover the same area, but would detect just 1% of the galaxies (shown in red on the left). COMAP, on the other hand, is sensitive to the aggregate emission from all galaxies in the line of sight, including those too faint to detect individually. Right: a representative power spectrum for the intensity map shown in the center panel. The spectrum is composed of two components: one from the clustering of galaxies on large scales and a second that arises from the scale-independent shot noise, which dominates on small scales. The shaded region indicates schematically the scales to which the Pathfinder is most sensitive. Credit: The Astrophysical Journal (2022)

Stem Education Coalition

Caltech campus

The The California Institute of Technology 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.

The California Institute of Technology 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, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology 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 The California Institute of Technology. Although The California Institute of Technology 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 The California Institute of Technology 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 The California Institute of Technology, 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 The California Institute of Technology. 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 as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology 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; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology 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 NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology 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, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles 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.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

## From The California Institute of Technology: “Why Does the Inside of the Solar System Not Spin Faster? An Old Mystery Has a Possible New Solution”

From The California Institute of Technology

July 06, 2022

Artist’s conception of planetary system formation. Credit: Shutterstock.

The motion of a tiny number of charged particles may solve a longstanding mystery about thin gas disks rotating around young stars, according to a new study from Caltech.

These features, called accretion disks, last tens of millions of years and are an early phase of solar system evolution. They contain a small fraction of the mass of the star around which they swirl; imagine a Saturn-like ring as big as the solar system. They are called accretion disks because the gas in these disks spirals slowly inward toward the star.

Scientists realized long ago that when this inward spiraling occurs, it should cause the radially inner part of the disk to spin faster, according to the law of the conservation of angular momentum. To understand conservation of angular momentum, think of spinning figure skaters: when their arms are outstretched, they spin slowly, but as they draw their arms in, they spin faster.

Angular momentum is proportional to velocity times radius, and the law of angular momentum conservation states that the angular momentum in a system stays constant. So, if the skater’s radius decreases because they have drawn their arms in, then the only way to keep angular momentum constant is to increase the spin velocity.

The inward spiral motion of the accretion disk is akin to a skater drawing their arms in—and as such, the inner part of the accretion disk should spin faster. Indeed, astronomical observations show that the inner part of an accretion disk does spin faster. Curiously, though, it does not spin as fast as predicted by the law of conservation of angular momentum.

Over the years, researchers have investigated many possible explanations for why accretion disk angular momentum is not conserved. Some thought friction between the inner and outer rotating parts of the accretion disk might slow down the inner region. However, calculations show that accretion disks have negligible internal friction. The leading current theory is that magnetic fields create what is called a “magnetorotational instability” that generates gas and magnetic turbulence—effectively forming friction that slows down the rotational speed of inward spiraling gas.

“That concerned me,” says Paul Bellan, professor of applied physics. “People always want to blame turbulence for phenomena they do not understand. There’s a big cottage industry right now arguing that turbulence accounts for getting rid of angular momentum in accretion disks.”

A decade and a half ago, Bellan began investigating the question by analyzing the trajectories of individual atoms, electrons, and ions in the gas that constitutes an accretion disk. His goal was to determine how the individual particles in the gas behave when they collide with each other, as well as how they move in between collisions, to see if angular momentum loss could be explained without invoking turbulence.

As he explained over the years in a series of papers and lectures that were focused on “first principles”—the fundamental behavior of the constituent parts of accretion disks—charged particles (i.e., electrons and ions) are affected by both gravity and magnetic fields, whereas neutral atoms are only affected by gravity. This difference, he suspected, was key.

Caltech graduate student Yang Zhang attended one of those talks after taking a course in which he learned how to create simulations of molecules as they collide with each other to produce the random distribution of velocities in ordinary gases, such as the air we breathe. “I approached Paul after the talk, we discussed it, and ultimately decided that the simulations might be extended to charged particles colliding with neutral particles in magnetic and gravitational fields,” Zhang says.

Ultimately, Bellan and Zhang created a computer model of a spinning, super-thin, virtual accretion disk. The simulated disk contained around 40,000 neutral and about 1,000 charged particles that could collide with each other, and the model also factored in the effects of both gravity and a magnetic field. “This model had just the right amount of detail to capture all of the essential features,” Bellan says, “because it was large enough to behave just like trillions upon trillions of colliding neutral particles, electrons, and ions orbiting a star in a magnetic field.”

The computer simulation showed collisions between neutral atoms and a much smaller number of charged particles would cause positively charged ions, or cations, to spiral inward toward the center of the disk, while negatively charged particles (electrons) spiral outward toward the edge. Neutral particles, meanwhile, lose angular momentum and, like the positively charged ions, spiral inward to the center.

A careful analysis of the underlying physics at the subatomic level—in particular, the interaction between charged particles and magnetic fields—shows that angular momentum is not conserved in the classical sense, though something called “canonical angular momentum” is indeed conserved.

Canonical angular momentum is the sum of original ordinary angular momentum plus an additional quantity that depends on the charge on a particle and the magnetic field. For neutral particles, there is no difference between ordinary angular momentum and canonical angular momentum, so worrying about canonical angular momentum is unnecessarily complicated. But for charged particles—cations and electrons—the canonical angular momentum is very different from the ordinary angular momentum because the additional magnetic quantity is very large.

Because electrons are negative and cations are positive, the inward motion of ions and outward motion of electrons, which are caused by collisions, increases the canonical angular momentum of both. Neutral particles lose angular momentum as a result of collisions with the charged particles and move inward, which balances out the increase in the charged-particle canonical angular momentum.

It is a small distinction, but makes a huge difference on a solar system-wide scale, says Bellan, who argues that this subtle accounting satisfies the law of conservation of canonical angular momentum for the sum of all particles in the entire disk; only about one in a billion particles needs to be charged to explain the observed loss of angular momentum of the neutral particles.

Furthermore, Bellan says, the inward motion of cations and outward motion of electrons results in the disk becoming something like a gigantic battery with a positive terminal near the disk center and a negative terminal at the disk edge. Such a battery would drive electric currents that flow away from the disk both above and below the plane of the disk. These currents would power astrophysical jets that shoot out from the disk in both directions along the disk axis. Indeed, jets have been observed by astronomers for over a century and are known to be associated with accretion disks, though the force behind them has long been a mystery.

Bellan and Yang’s paper was published in The Astrophysical Journal on May 17, 2022.

Stem Education Coalition

Caltech campus

The The California Institute of Technology 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.

The California Institute of Technology 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, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology 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 The California Institute of Technology. Although The California Institute of Technology 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 The California Institute of Technology 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 The California Institute of Technology, 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 The California Institute of Technology. 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 as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology 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; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology 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 NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology 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, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles 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.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

## From The California Institute of Technology: “Cosmic Radio Pulses Probe Hidden Matter Around Galaxies”

From The California Institute of Technology

July 04, 2022

Distant Fast Radio Bursts piercing the gaseous dark matter halos of galaxies in the local universe. Credit: Courtesy of Charles Carter.

Powerful radio pulses originating deep in the cosmos can be used to study hidden pools of gas cocooning nearby galaxies, according to a new study appearing in the journal Nature.

So-called fast radio bursts, or FRBs, are pulses of radio waves that typically originate millions to billions of light-years away (radio waves are electromagnetic radiation like the light we see with our eyes but have longer wavelengths and frequencies). The first FRB was discovered in 2007, and since then, hundreds more have been found. In 2020, Caltech’s STARE2 instrument (Survey for Transient Astronomical Radio Emission 2) and Canada’s CHIME (Canadian Hydrogen Intensity Mapping Experiment) detected a massive FRB that went off in our own Milky Way galaxy.

Those earlier results helped confirm the theory that the energetic events most likely originate from dead, magnetized stars called magnetars.

As more and more FRBs roll in, researchers are now asking how they can be used to study the gas that lies between us and the bursts. In particular, they would like to use the FRBs to probe halos of diffuse gas that surround galaxies. As the radio pulses travel toward Earth, the gas enveloping the galaxies is expected to slow the waves down and disperse the radio frequencies. In the new study, the researchers looked at a sample of 474 distant FRBs detected by CHIME, which has discovered the most FRBs to date, and showed that the subset of two dozen FRBs that passed through galactic halos were indeed slowed down more than non-intersecting FRBs.

“Our study shows that FRBs can act as skewers of all the matter between our radio telescopes and the source of the radio waves,” says lead author Liam Connor, the Tolman Postdoctoral Scholar Research Associate in Astronomy, who works with assistant professor of astronomy and study co-author, Vikram Ravi.

“We have used fast radio bursts to shine a light through the halos of galaxies near the Milky Way and measure their hidden material,” Connor says.

The study also reports finding more matter around the galaxies than expected—specifically, about twice as much gas as theoretical models predicted.

All galaxies are surrounded and fed by massive pools of gas out of which they were born. However, the gas is very thin and hard to detect. “These gaseous reservoirs are enormous. If the human eye could see the spherical halo that surrounds the nearby Andromeda galaxy, the halo would appear one thousand times larger than the moon,” Connor says.

Researchers have developed different techniques to study the hidden halos. For instance, Caltech professor of physics Christopher Martin and his team developed an instrument at the W. M. Keck Observatory called the Keck Cosmic Webb Imager (KCWI) that can probe the filaments of gas that stream into galaxies from the halos.

This new FRB method allows astronomers to measure the total amount of material in the halos, which will help piece together a picture of how galaxies grow and evolve over cosmic time.

“This is just the start,” says Ravi. “As we discover more FRBs, our techniques can be applied to study individual halos of different sizes and in different environments, addressing the unsolved problem of how matter is distributed in the universe.”

In the future, the FRB discoveries are expected to continue streaming in. Caltech’s 110-dish Deep Synoptic Array, or DSA-110, has already detected several FRBs and identified their host galaxies. Funded by the National Science Foundation (NSF), this project is located at Caltech’s Owen Valley Radio Observatory near Bishop, California.

In the coming years, Caltech researchers have plans to build an even bigger array, the DSA-2000, which will include 2,000 dishes and be the most powerful radio observatory ever built. The DSA-2000, currently being designed with funding from Schmidt Futures and the NSF, will detect and identify the source of thousands of FRBs per year.

The science paper is published in Nature.

Stem Education Coalition

Caltech campus

The The California Institute of Technology 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.

The California Institute of Technology 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, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology 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 The California Institute of Technology. Although The California Institute of Technology 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 The California Institute of Technology 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 The California Institute of Technology, 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 The California Institute of Technology. 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 as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology 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; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology 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 NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology 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, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles 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.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

## From The California Institute of Technology via “phys.org” : “Astronomers discover two new polars”

From The California Institute of Technology

via

“phys.org”

June 20, 2022
Tomasz Nowakowski

Folded light curve of ZTFJ0850+0443 (top, orbital perdiod = 1.72 hours) over ZTF forced photometry. Large amplitude variations (1–2 mag) are characteristic of cyclotron beaming in polars. Credit: Rodriguez et al, 2022.

By analyzing the data from the Spektr-RG (SRG) space observatory and from the Zwicky Transient Facility (ZTF), astronomers from the California Institute of Technology (Caltech) and elsewhere have discovered two new polars. The discovery is reported in a paper submitted to The Astrophysical Journal.

Cataclysmic variables (CVs) are binary star systems comprising a white dwarf and a normal star companion. They irregularly increase in brightness by a large factor, then drop back down to a quiescent state. Polars are a subclass of cataclysmic variables distinguished from other CVs by the presence of a very strong magnetic field in their white dwarfs.

Now, a team of astronomers led by Caltech’s Antonio C. Rodriguez has found two new polars which received designation ZTFJ0850+0443 and ZTFJ0926+0105. The detection is a result of crossmatching the eROSITA Final Equatorial Depth Survey (eFEDS) catalog with forced photometry of ZTF Data Release 5 (DR5).

“We have discovered two polars: ZTFJ0850+0443 and ZTFJ0926+0105, through a crossmatch of the eFEDS dataset and ZTF archival photometry,” the researchers wrote in the paper.

According to the study ZTFJ0850+0443 is an eclipsing polar with an orbital period of 1.72 hours at a distance of some 3260 light years away from the Earth. Its white dwarf has a mass of about 0.81 solar masses, while the companion star’s mass was estimated to be approximately 0.12 solar masses. The results suggest that ZTFJ0850+0443 is likely a low-field polar with magnetic field strength below 10 MG.

At a distance of about 1200 light years ZTFJ0926+0105 is a non-eclipsing polar with an orbital period of about 1.48 hours. It has a more typical magnetic field strength of polars—at least 26 MG. Given that ZTFJ0926+0105 is not eclipsing, the team was not able to measure the mass of its white dwarf.

The astronomers concluded that their discovery shows how important the eFEDS survey is in supplementing ZTF for the detection of new cataclysmic variables. Moreover, they added that by making use of ESA’s Gaia satellite, it will be possible to obtain precise luminosities of the newfound polars. The recent Gaia Data Release 3 (DR3), published June 13, may be very useful in this context.

“Schwope et al (2021) identified an eclipsing polar through an eROSITA/SRG crossmatch with Gaia using a proprietary eRASS dataset,” the scientists noted.

The research conducted by Rodriguez’s team is part of a larger follow-up analysis of the eFEDS/ZTF footprint. Such studies could be useful in overcoming observational biases in previous optical-only searches for cataclysmic variables, and would directly lead to accurate volume-limited studies of CVs.

Stem Education Coalition

Caltech campus

The The California Institute of Technology 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.

The California Institute of Technology 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, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology 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 The California Institute of Technology. Although The California Institute of Technology 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 The California Institute of Technology 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 The California Institute of Technology, 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 The California Institute of Technology. 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 as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology 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; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology 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 NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology 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, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles 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.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

## From The California Institute of Technology: “Thousands of Galaxies Shine in Ultraviolet Light in New Hubble Image”

From The California Institute of Technology

June 14, 2022
Whitney Clavin
(626) 395‑1944
wclavin@caltech.edu

This image captured by the Hubble Space Telescope shows a region of about 5,000 galaxies located billions of light-years away. The region is located within a cosmic field called the Extended Groth Strip, one of five well-studied fields that were observed in a program called CANDELS, for Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. In this new view, taken as part of a program called UVCANDELS, ultraviolet and blue optical light have been added into the imagery, in addition to the optical and infrared light observed previously. Ultraviolet light and blue optical light are shown in blue; red light appears green; and near-infrared light is red. The region pictured covers 9 square arcminutes, which is the equivalent of about one percent the size of the full moon on the sky. Credit: NASA/STScI/Harry Teplitz (Caltech/IPAC)

Images may help reveal how the first stars ended universe’s dark ages.

A new image from NASA’s Hubble Space Telescope is brimming with distant galaxies in an assortment of shapes.

Some are seen face-on and appear oval or as disks or spirals, while others are seen edge-on and look more like cigars. The new image differs from past views of the same field of galaxies in that it now includes observations made in ultraviolet light.

“Ultraviolet light comes from the most massive stars, which are also the youngest and hottest of stars, and it provides a unique insight into ongoing star formation in galaxies both near and far,” says Xin Wang, a postdoctoral scholar at Caltech’s IPAC, an astronomy center. Wang presented the results June 14 at the 240th meeting of the American Astronomical Society (AAS) in Pasadena.

Wang and his colleagues, led by Harry Teplitz, a staff scientist at IPAC, used the Hubble Space Telescope to survey ultraviolet light coming from distant galaxies in a collection of different patches of sky known collectively as CANDELS, for Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. They surveyed a large portion of the CANDELS fields, covering an amount of sky equivalent to about 60 percent the size of the full moon. In total, the new program, called UVCANDELS, imaged about 140,000 galaxies and amounted to about 10 days of Hubble time.

The result is the largest ultraviolet Hubble survey of distant galaxies to date. The researchers say the images will ultimately help with a mystery dating back to the early chapters of our universe, to an epoch known as reionization. This is when extreme, or high-energy, ultraviolet light from the first stars and galaxies ionized a fog of hydrogen gas, splitting atoms into charged electrons and protons. After the fog burned away, light could travel through the universe unimpeded, bringing an end to the so-called dark ages. Exactly how this happened is not clear, but by studying the extreme ultraviolet light emitted by distant galaxies, scientists will gather new clues.

“We can’t see the extreme ultraviolet light coming from the first galaxies because those photons are absorbed before they reach us,” says Teplitz. “We look instead at very similar, or analogous, galaxies that are not quite as far away—11 billion light-years instead of more than 13 billion—to try to understand the physical conditions that enabled the first galaxies to cause reionization.”

Stem Education Coalition

Caltech campus

The The California Institute of Technology 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.

The California Institute of Technology 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, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology 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 The California Institute of Technology. Although The California Institute of Technology 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 The California Institute of Technology 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 The California Institute of Technology, 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 The California Institute of Technology. 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 as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology 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; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology 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 NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology 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, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles 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.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

## From The California Institute of Technology: “Lab Earthquakes Show How Grains at Fault Boundaries Lead to Major Quakes”

From The California Institute of Technology

June 06, 2022

Contact
Robert Perkins
(626) 395‑1862
rperkins@caltech.edu

By simulating earthquakes in a lab, Caltech engineers have provided strong experimental support for a form of earthquake propagation now thought responsible for the magnitude-9.0 earthquake that devastated the coast of Japan in 2011.

Along some fault lines which are the boundaries of tectonic platesa fine-grained gravel is formed as the plates grind against one another. The influence of this gravel on earthquakes has long been the subject of scientific speculation. In a new paper appearing in the journal Nature on June 1, the Caltech researchers show that the fine gravel-known as rock gouge-first halts earthquake propagation but then triggers the rebirth of earthquakes to generate powerful ruptures.

“Our novel experimental approach has enabled us to look into the earthquake process up close, and to uncover key features of rupture propagation and friction evolution in rock gouge,” says Vito Rubino, research scientist and lead author of the Nature paper. “One of the main findings of our study is that fault sections previously thought to act as barriers against dynamic rupture may in fact host earthquakes as a result of the activation of co-seismic friction weakening mechanisms.”

A three-dimensional visualization shows how rock gouge can arrest a rupture (in red) but, with a combination of dynamic stressing and dynamic weakening, will ultimately re-nucleate the rupture shortly thereafter (in blue). Credit: Rubino et. al., Nature, 2022.

In the paper, Rubino and his co-authors Nadia Lapusta, the Lawrence A. Hanson, Jr., Professor of Mechanical Engineering and Geophysics, and Ares Rosakis, Theodore von Kármán Professor of Aeronautics and Mechanical Engineering, show that so-called “stable” or “creeping” faults are not actually immune to major ruptures after all, as previously suspected. Such faults occur when tectonic plates slide past one another slowly, without generating big quakes (for example, the currently creeping section of the San Andreas Fault in central California).

Instead, rock gouge has a complex behavior. It first acts as a barrier to the rupture, absorbing energy and blocking its progress. But, when the plates slide past each other with high enough velocity, the rock gouge interface weakens and dramatically reduces friction between the two plates, causing the re-emergence of the quake. This process is known as “renucleation.”

“Based on the previous rich body of rock-friction experiments, we know that rock gouge can either strengthen with fault slip and act as a barrier, or weaken and promote earthquake rupture,” Lapusta says. “However, these behaviors are typically considered to be separated in space, with weakening and strengthening occurring on different fault locations. Our experiments show how these behaviors can combine on the same fault locations during the same slip event, over the timescales of dynamic rupture, leading to intermittent slip and potentially turning a fault barrier into an earthquake-prone region.”

The Nature study explores the role and reaction of rock gouge, a micrometer-sized granular material, to seismic activity. To simulate the effect of rock gouge on an earthquake’s propagation, the team used Caltech’s so-called “seismological wind tunnel”, founded by Rosakis and former Caltech Seismological Laboratory director Hiroo Kanamori, John E. and Hazel S. Smits Professor of Geophysics, Emeritus. The facility, in existence since 1999, allows engineers and scientists to study major earthquakes on a miniature scale.

To simulate an earthquake, the team first cut in half a transparent meter-sized block of a type of plastic known as Homalite. The bulk properties of Homalite enable dynamic rupture nucleation within samples as small as tens of centimeters in diameter; studying these effects in rock would require samples that are tens of meters in size.

The researchers then placed the two halves of the Homalite together under high pressure and shear (a situation in which the two halves want to slide against one another in opposite directions), simulating tectonic pressure that slowly builds up along a fault line. Between the pieces, fine-grained quartz powder was embedded as a stand-in for fault gouge. Next, the team put a small wire fuse between the two halves; its location was the “epicenter” of the earthquake they planned to simulate. As the simulated quake progressed, high-speed imaging technology was used to record its evolution, one millionth of a second at a time.

“Back in the late 1990s, when we were designing the ‘seismological wind tunnel,’ we could never have imagined its success in discovering such a rich spectrum of physical phenomena relating to frictional earthquake source processes and that such phenomena could rigorously be scaled to explain natural earthquake behavior occurring at massively different length scale around the globe,” Rosakis says. “This is a testament of the tremendous power of the discipline of mechanics.”

Next, the team plans to study the effects of fluids which are naturally present in Earth’s crust on the frictional behavior of rock gouge.

This research was funded by the National Science Foundation (NSF), the U.S. Geological Survey, the NSF–IUCRC program at Caltech’s Center for Geomechanics and Mitigation of Geohazards (GMG), and the Southern California Earthquake Center (SCEC).

Stem Education Coalition

Caltech campus

The The California Institute of Technology 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.

The California Institute of Technology 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, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology 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 The California Institute of Technology. Although The California Institute of Technology 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 The California Institute of Technology 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 The California Institute of Technology, 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 The California Institute of Technology. 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 as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology 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; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology 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 NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology 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, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles 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.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

## From The California Institute of Technology: “The 2022 Caltech Space Challenge—to Titan and Back”

From The California Institute of Technology

May 26, 2022

Titan appears before Saturn in this natural color view of Titan and Saturn from NASA’s Cassini spacecraft. (Credit: NASA/JPL-Caltech/Space Science Institute)

Titan, Saturn’s largest moon, is the only planetary body in our solar system besides Earth where there is clear evidence of surface liquid. This is an essential element to life as we know it and makes Titan a prime target in the search for extraterrestrial life.

Named after Christiaan Huygens, the Dutch astronomer who discovered Titan in 1655, the Huygens space probe successfully landed on Titan in 2005.

However, no instruments existed in 2005 that could capture and return a sample of Titan’s surface composition back to Earth. This is the basis for the 2022 Caltech Space Challenge, which took place from March 21–25 on the Caltech campus. Two teams of 16 space exploration enthusiasts, including five Caltech students along with university students from around the globe, were given five days to design an autonomous mission to collect three different samples from Titan. The teams also needed to safely contain those samples for the ascent off Titan and then bring those samples back to Earth. As the teams designed and modified their concepts throughout the week, mentors from JPL and Caltech provided essential support and guidance.

The two teams, appropriately named “Voyager” and “Explorer”, first met the Sunday before the challenge officially began. While all the participants knew the challenge involved a mission to Titan, the full scope of the challenge remained a secret. After listening to an inspiring speech by then-JPL interim director Lt. Gen. Larry D. James USAF (Ret.), the challenge participants learned they would not only need to obtain and return a single sample from Titan, but they would also need to collect and return three distinct samples from Titan’s surface.

Although designing and presenting a flagship sample-return mission in less than a week is no easy task, “the real challenge is teamwork,” says Nigel Angold, a mentor in this year’s challenge whose experience includes operations management for NASA and European Space Agency missions. Angold mentors the participants in teamwork and team building, and he has been a mentor for every iteration of the Caltech Space Challenge since its inception in 2011. As the teams wrestled with their mission concepts and proposals throughout the week, Angold was a ubiquitous figure, weaving in and out of the teams’ base camps to share his expertise and insight. The appreciation for Angold’s team-building wisdom was clear, as enthusiastic shouts of “Nigel! Nigel!” could be heard from challenge participants throughout the closing ceremony.

Student participants in the 2022 Caltech Space Challenge at the event’s opening ceremony.

Caltech GALCIT graduate students Liam Heidt and Josefine Graebener ran and organized this year’s Space Challenge from start to finish. Heidt and Graebener, both international graduate students, were responsible for designing the mission parameters, securing sponsorship, obtaining the students, speakers, and mentors, selecting the jury, and advertising the event. “Every edition of the challenge has two new graduate students as the co-chairs, so there is certainly some pressure to pull off another successful event,” says Heidt. “However, we have an amazing support network made up of the previous co-chairs as well as KISS [Keck Institute for Space Studies] faculty and staff.”

This sense of community motivated Heidt and Graebener to take on the responsibilities of co-chairs. “I’ve always been interested in space as well as giving back to this amazing community, so being part of the Space Challenge was a no-brainer,” says Heidt.

“It’s very important to me to give international students the opportunity to experience life on the Caltech campus and work with these experts from JPL,” adds Graebener, “because it’s just not as easily obtainable for international students to collaborate with someone from JPL like it would be for someone from the U.S.”

Out of a record 912 applicants from 75 different countries and 332 universities, Heidt and Graebener narrowed the pool down to the final 32 students through a series of interviews. After assessing the academic backgrounds of each student, the two teams were then assembled so each included a fair distribution of experts in each area. “I really liked the applications where I could tell that they are enthusiastic about space and have historically sought out opportunities to pursue this passion of theirs,” says Heidt.

“If someone was really excited about the mission during the interview or application and stated some ideas that they already had about the challenge, some specific technology that they’re interested in investigating, that definitely stood out to me,” adds Graebener.

Adrian Dumitrescu was one such international student selected to participate in this year’s challenge. A member of Team Voyager, Dumitrescu is a PhD student at the University of Southampton in England, but he is originally from Romania. This was Dumitrescu’s third time applying for the Caltech Space Challenge, one of a few participants who have applied multiple times.

Before this year’s challenge commenced, Heidt and Graebener, who designed all facets of the Titan mission statement, anticipated what the teams’ biggest obstacles might be based on conditions near Titan’s surface liquid. “They have to collect a sample of the lake liquid, a sample of the atmosphere right above the lake, and a sample of the soil of either the ground of the lake or the shore of the lake,” says Graebener. “This is going to be really exciting; how they are going to figure out how to take these three samples and bring them back to Earth?”

“You don’t want to, for example, spend potentially billions of dollars to obtain these samples and have them leak out on their way back to Earth, which would obviously be a critical mission failure,” says Heidt, “so how to store these samples safely and obtain enough propellants or energy to be able to exit the strong gravitational field surrounding Saturn to come back to Earth—that’s definitely no easy feat.”

When asked what advice they would give to the students about to participate in this year’s challenge, both co-chairs offered salient points. “Getting enough sleep is definitely important; that’s something I’ve learned as a PhD candidate,” says Heidt.

“Be creative and don’t be intimidated,” says Graebener. “I’m 100 percent sure the teams are going to surprise us with their amazing mission concepts at the end. They just need to trust the process and trust themselves and their abilities, because they are the best of the best.”

“It was hard to gauge when we were good enough,” says Chloé Gentgen, a member of team Explorer and PhD student at MIT who is originally from France. The teams had free rein to design their concepts without much interference from the mentors or organizers, so determining when a design component was “good enough” required effective team communication and trust. “Playing Ninja was helpful,” says Gentgen, when referring to how team Explorer managed to build trust. Ninja is a team-building game in which you eliminate your opponents by swiping at their hands. It’s commonly played as an ice breaker and helps explain some of the sudden bursts of laughter heard around Caltech during the Space Challenge.

On the final day of the challenge, teams Voyager and Explorer presented their mission concepts to a jury made up of JPL scientists, Caltech faculty, and aerospace industry insiders. The teams were given 45 minutes to explain all aspects of their mission and field questions from the jury. This step of the challenge tested the teams’ ability to communicate effectively and remain graceful under pressure. During the closing ceremony, members of the jury expressed amazement at both teams’ composure and the scope of the mission concepts. Team Voyager was applauded for its elegant entry, descent, and landing (EDL) solution, and team Explorer was praised for its excellent written documentation and propulsion solution.

After an intense week and final debrief from jury members, team Voyager was revealed as the winner by a narrow margin. “This is one of those situations where it’s a bummer you have to choose a winner,” says George Whitesides, the lead juror and current chairman of the Space Advisory Board for Virgin Galactic. “Both teams worked their guts out for a week to produce something that many organizations would take months, if not years, to produce.”

Ultimately, the element of feasibility pushed team Voyager’s proposal over the edge. “The teams each figured out relatively elegant solutions to something that would instantly be the hardest thing that NASA has ever done robotically,” says Whitesides. “The ultimate reason that Voyager won was because we thought their proposal was more likely to be an implementable mission, something that a NASA-type organization might be able to afford.”

While competition can add a sense of drama, the value of the Space Challenge lies beyond a simple head-to-head battle. “I believe project-based learning is arguably the most effective type of learning that we can give students,” says Whitesides. “In one week, the students who participated in the 2022 Caltech Space Challenge learned the equivalent of months of systems design. This is exactly what both employers and other institutions want to see in the people they hire: the ability to work with other people in a group and successfully accomplish a shared goal.”

The student-designed-and-executed Space Challenge started relatively close to home in 2011 with a mission concept centered around a human mission to a near-Earth object and continues to expand in scope and distance from Earth. “The great thing about the Caltech Space Challenge is that it was a totally original idea thought up and executed by Caltech students,” says Tom Prince, Caltech Ira S. Bowen Professor of Physics, Emeritus and Allen V.C. Davis and Lenabelle Davis Leadership Chair, Keck Institute for Space Studies. “The Space Challenge has gotten even better with subsequent challenges, and I’m sure it will have a lasting legacy by helping to develop the next generation of space explorers.”

Stem Education Coalition

Caltech campus

The The California Institute of Technology 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.

The California Institute of Technology 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, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology 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 The California Institute of Technology. Although The California Institute of Technology 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 The California Institute of Technology 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 The California Institute of Technology, 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 The California Institute of Technology. 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 as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology 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; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology 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 NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology 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, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles 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.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r