Although our Sun is an ordinary star, the Solar System is the only planetary system known to harbor life. Studying the Solar System enables us to learn how stable planetary systems form and how planets develop the conditions needed for life.
The solar system is comprised of a variety of bodies, from giant planets like Jupiter to the smallest asteroids and everything in between. RG astronomers use the Submillimeter Array to measure both the thermal emission from solar system objects and spectral lines from their atmospheres. These measurements allow one to infer surface temperatures as well as atmospheric composition, thermal structure, and dynamics on bodies as diverse as Neptune, Mars, Titan, and Pluto.
The CfA has joined the Pan-STARRS-1 Science Consortium. Pan-STARRS-1 is a 1.8m aperture telescope located on Haleakala. Its 1.4 gigapixel, 7 square degree camera will repeatedly image the entire sky north -30 degrees declination. Roughly 60% of the observing time of the PS1 telescope will be dedicated to the "3pi steradian" survey with an observing cadence that is optimized for the detection of near-Earth asteroids and slow-moving solar system bodies.
The solar wind originates in the million-degree solar corona and flows out from the sun at a million miles per hour. Most of the ions in the wind are hydrogen and helium, but a small fraction are heavier elements such as carbon, oxygen, and neon. When those heavy ions collide with neutral gas in comets, planetary atmospheres, or very tenuous gas throughout the solar system, they emit X-rays via a process called charge exchange. Many comets and planets have been observed using X-ray telescopes.
Solar and Stellar X-Ray Group (SSXG) researchers study solar and stellar atmospheres which are composed of extremely hot, highly dynamic plasma. SSXG activities include designing, testing, building and operating instruments, analyzing space and ground-based observations, and creating theoretical models. SSXG researchers are major partners in the Atmospheric Imaging Assembly (AIA) investigation on the Solar Dynamics Observatory, which is set to launch in 2008.
The heliosphere is a bubble of hot gas in interstellar space stretching from the Sun to greater than 100 Sun-Earth distances. It contains some fraction of inflowing neutral interstellar hydrogen and helium atoms. Highly charged positive ions emanate from the Sun in the solar wind and impact the neutral material. The ions capture electrons from the atoms into high excited states that radiate primarily in the soft X-ray spectral region. The spectra provide information about the solar wind composition and velocity and the distribution of atoms in the heliosphere.
Studies of the atmospheres of planets in our solar system (including Earth).
The Smithsonian Astrophysical Observatory has been awarded a NASA space flight project to build the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument, the first NASA Earth Venture Instrument. Earth Venture missions, part of the Earth System Science Pathfinder program, are small, targeted science investigations that complement NASA's larger research mission.
Roughly 4.5 Gyr ago, the Solar System formed in a disk surrounding the proto-Sun. Within this disk, the gas giants grew to their current sizes in a few Myr; the rocky planets took a few tens of Myr to reach their present masses.
Besides keeping track of the myriad objects in the Solar System, SSP scientists use data on the compositions, masses, and positions of these objects along with theoretical models to learn how planets form and evolve in time.
Every planetary system forms in a thin disk of gas and dust orbiting a young star. Small dust grains, a micron or two in size, collide and merge into large aggregates that settle into the midplane of the disk. In the midplane, aggregates grow into planetesimals with diameters of roughly 1 km. Collisions between planetesimals produce planets. SSP scientists use theoretical calculations to understand how dust grains evolve and how planetesimals become planets.
Our Sun is an excellent laboratory for studying the everyday phenomena of a typical star. SSP scientists are experts in analyzing observations and developing theoretical models of the solar atmosphere, which produces the light we see and where powerful magnetic fields produce hot plasma and accelerate high energy particles that interact with the atmospheres of the Earth and other planets.
Probably the most surprising objects observed in X-rays are comets. Comets were described by Fred Whipple as being "dirty snowballs". So how does a snowball make X-rays? Through a phenomenon called charge exchange.