Research topics

Visualization of a simulated black hole with jets.  (Visualization: Ralf Kaehler Simulation: Jonathan McKinney, Alexander Tchekhovskoy, Roger Blandford.) When a giant star—about 10 to 30 times the mass of the Sun—exhausts its fuel, gravity can pull the star's core into a sphere a tiny fraction of its original size. The shrinkage is so drastic that stars millions of miles across can collapse to roughly 10 kilometers in diameter. These are known as neutron stars. In extreme cases, stars can contract even further under their own gravity to an infinitely dense point, or singularity, called a black hole.
agn Nature has provided us with spectacular particle accelerators called active galactic nuclei, or AGN. These are tremendously large black holes at the centers of galaxies, some of which are known to be a million times heavier than our sun. These distant celestial laboratories allow researchers to study physics at energies orders of magnitude greater than what can be generated by the most powerful man-made accelerators on Earth. Many—if not all—galaxies contain supermassive black holes in their centers; there is even a prominent one in the heart of our own Milky Way. So what makes a supermassive black hole an AGN?
A simulation of the period of reionization, when the Universe became transparent to light and let the cosmic microwave background escape. (Visualization: Ralf Kaehler, Marvelo Alvarez, Tom Abel Simulation: Marvelo Alvarez, Tom Abel.) The cosmic microwave background (CMB) is a faint glow in microwave radiation that is almost perfectly uniform across the sky.  This thermal radiation was emitted about 380,000 years after the Big Bang, as the Universe became transparent for the first time. The CMB peaks at a wavelength of about 2mm with a nearly perfect blackbody spectrum corresponding to a temperature of 2.73 K. Although the CMB is extremely uniform, there are slight polarizations and variations in temperature throughout.  These very faint features offer important glimpses into the physics of the early Universe.
The Bullet Cluster. (Credit: NASA, ESA, CXC, M. Bradac (University of California, Santa Barbara), and S. Allen (Stanford University).) To better understand the Universe, it is often necessary to estimate the mass of an astrophysical object. Those objects span a vast range of sizes, from the Sun, to the solar system, to the Milky Way, and even up to the entire Universe. Researchers use a number of techniques to measure the mass of extremely large objects. One way to estimate an object’s mass is by observing its light output. If the object does not emit its own light, researchers can examine the way in which the light of background sources bends around it. Another technique is to examine the dynamic motion of objects around it.
Simulation of dark matter scaffolding for baryonic matter galaxies. (Visualization: Ralf Kaehler, Carter Emmart, Tom Abel Simulation: Tom Abel, Oliver Hahn.) A leading hypothesis on the nature of dark matter is that it is comprised of Weakly Interacting Massive Particles, or WIMPs, which were produced moments after the Big Bang. If WIMPs are dark matter, then their presence in our galaxy may be detectable via scattering from atomic nuclei that make up the substance of special detectors, two of which KIPAC has a major role in constructing: SuperCDMS SNOLAB and LZ.
Hubble image showing the galaxy cluster RXC J0142.9+4438. (Credit: NASA / ESA / Hubble / RELICS.) Galaxy clusters are the largest objects in the universe, spanning distances up to ten million light years, and containing the equivalent mass of a million, billion suns. Our research examines the physics of these remarkable systems using the best available multi-wavelength data, and uses the observed properties of clusters to probe the nature of dark matter, the weakly interacting yet dominant matter component of the universe, and dark energy, the driving force behind cosmic acceleration. Most of the normal, baryonic matter in galaxy clusters—as in the rest of the Universe—is in gaseous form. In galaxy clusters, enormous gravity (from the dominating dark matter) squeezes this gas, heating it to 100 million degrees and causing it to shine brightly at X-ray wavelengths.
Simulation of a proto-galaxy. (Visualization: Ralf Kaehler, Tom Abel Simulation: John Wise, Tom Abel.) Galaxies are collections of stars, gas and dark matter that play host to some of the most extreme processes in nature. Galaxies are also the signposts of the Universe, beacons of light scattered throughout a mostly dark cosmos. There are millions of known galaxies in the Universe and they come in various shapes, sizes and colors. These physical properties are thought to be determined, in part, by a galaxy’s surrounding conditions. Galaxies found in galaxy clusters, for example, tend to be elliptical and have little ongoing star formation. Isolated galaxies, on the other hand, are typically spiral in shape, blue in color and have active star formation. (The blue coloration is a product of star formation, which is a key characteristic of young galaxies; elliptical galaxies are redder since they are composed of old stars, which emit light on the red end of the spectrum.) Though galaxies are filled with the visible “stuff” of the cosmos, they are also critical laboratories in our search to understand the invisible: mysterious dark matter and dark energy.
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We cannot see one of the universe’s primary constituents: dark matter.  The reason is simple: it's dark. However, we can infer where it is located from observations of distant galaxies because of a key property of light, namely that it does not always travel in straight lines.

Residual Map The Fermi-Large Angle Telescope (Fermi-LAT) probes photons of the highest energies. At such energy scales, these particles may exhibit signatures of the new physics, which deviate significantly from the Standard Model.  For instance, the currently accepted standard cosmological model predicts that the universe is composed of roughly 24 percent non-baryonic (i.e., not composed of quarks) dark matter (DM).  So far the existence of dark matter has been inferred only from its gravitational influence on large scales and several experimental techniques for detecting the dark matter particle are currently being pursued including direct searches with terrestrial detectors, production at an accelerator such as the Large Hadron Collider (LHC), and indirect detection through the measurement of the secondary products of dark matter annihilations or decays. 
A composite image of the Crab Nebula showing the X-ray (blue), and optical (red) images superimposed. The size of the X-ray image is smaller because the higher energy X-ray emitting electrons radiate away their energy more quickly than the lower energy optically emitting electrons as they move. (Credit: Optical: NASA/HST/ASU/J. Hester et al. X-Ray: NASA/CXC/ASU/J. Hester et al.) A neutron star is the product of the explosive transformation of a massive star. Any star's life is a careful balancing act: the gravity of its own material pulls inward, while pressure from the heat and light produced by the burning of hydrogen into helium in the star's core pushes outward. For a massive star, this delicate dance goes on for millions of years, until the hydrogen supply in the core runs low. Gravity begins to take over and the core contracts and heats up.  This increase in temperature allows the star to fuse helium into even heavier elements, temporarily staving off gravitational collapse.
Artist's rendering of LSST at night. (Credit: LSST Project/NSF/AURA.)

In the traditional model of astronomical observation, individual or small teams of astronomers study a select class of objects in a small region of sky. However, some of the most exciting cosmological and astrophysical results in recent years have required the study of millions of galaxies over thousands of square degrees of sky.

count map A long-standing mystery is the mechanism by which cosmic rays are accelerated in our galaxy.  While the most powerful accelerators on Earth, such as the Large Hadron Collider, can accelerate particles to teraelectronvolt, or TeV, energy scales, fluxes of cosmic rays reaching the Earth have been detected with energies up to one million times higher. Fermi-LAT’s high-energy gamma-ray emission data can be used to indirectly study the spatial distribution and energies of cosmic rays in distant astrophysical environments -- regions where cosmic-ray acceleration is believed to be taking place.
Map of the cosmic microwave background (CMB) polarization amplitude as observed by ESA’s Planck satellite. (Credit: ESA/Planck Collaboration.)

The universe began in a hot big bang 13.7 billion years ago. It is remarkably homogeneous on the large scale, and at the time period we're observe the cosmic microwave background, segments of the cosmos that are out of causal contact with each other are similar at the level of about ten parts per million. How did this remarkable synchronization come about?

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KIPAC's visualization and data analysis facilities provide hardware and software solutions that help users at KIPAC and SLAC to analyze their large-scale scientific data sets.

solar KIPAC members who are part of the Stanford Solar Observatories Group take part in observational and theoretical research on the physics of the Sun. A particular emphasis is on understanding solar variability (for example, determining the cause of the Sun's 11-year sunspot cycle) and how it impacts the Earth.
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Roughly 400,000 years after the Big Bang, the Universe—bathing in the afterglow of radiation that we see today as the cosmic microwave background—began to enter the cosmic “dark ages,” so named because the luminous stars and galaxies we see today had yet to form.