A debris disk can look deceptively simple from a distance: a faint ring of dust surrounding a star, something like a scaled-up version of the Solar System’s asteroid belt or Kuiper Belt. But when astronomers observe these disks with instruments such as the Atacama Large Millimeter/submillimeter Array (ALMA), the Hubble Space Telescope, and the James … Read more

A Sun-like star may look perfectly ordinary in visible light while hiding a dusty secret. When astronomers observe some stars in infrared wavelengths, they detect more radiation than the stellar surface alone should produce. That extra infrared glow can come from microscopic grains orbiting the star. If the grains are relatively warm and are continually … Read more

A main-sequence star can look perfectly ordinary in visible light while hiding an entire architecture of dust around it. The star itself may dominate almost every photon reaching a telescope. Yet farther out, grains created by collisions among asteroids, comets, and larger planetesimals can form broad disks, narrow belts, halos, gaps, and rings. In some … Read more

Centaurs occupy one of the strangest neighborhoods in the Solar System. These small icy bodies generally orbit between Jupiter and Neptune, far beyond the region where ordinary comets become dramatically active. At such distances, sunlight is weak, temperatures are low, and water ice should remain almost completely frozen. Yet some Centaurs develop fuzzy comae, release … Read more

The outer solar system is not a quiet collection of planets moving through empty space. Between the orbit of Jupiter and the distant realm of Neptune lies a restless population of small icy bodies known as Centaurs. Centaurs are among the most intriguing objects in planetary science because they appear to occupy a transitional state … Read more

Dwarf planets in the outer Solar System are extraordinarily difficult worlds to study. Pluto, Eris, Makemake, and Haumea are so distant that even powerful telescopes often see them as little more than points of light. Their surfaces can be studied through spectroscopy, and their brightness can reveal clues about rotation and composition, but detecting a … Read more

When most people think of rings in the Solar System, Saturn immediately comes to mind. Jupiter, Uranus, and Neptune also have ring systems, so for a long time astronomers naturally associated rings with giant planets. Then something unexpected happened. Astronomers discovered rings around objects far smaller than planets, including the Centaur Chariklo, the dwarf planet … Read more

A star normally appears steady against the night sky. But under very specific circumstances, it can suddenly vanish, return, disappear again, and then reappear several times within a matter of seconds or minutes. This unusual celestial event is called a grazing stellar occultation. It occurs when the apparent edge of a nearby astronomical body, most … Read more

An asteroid may be millions of kilometers away, appear as little more than a faint point of light, and still have its size measured surprisingly well from Earth. The trick is not necessarily to photograph the asteroid itself. Instead, astronomers can wait for the asteroid to pass directly in front of a distant star. For … Read more

A tiny asteroid millions of kilometers away may be far too small to appear as anything more than a faint point of light in a telescope. Sometimes it cannot be imaged clearly at all. Yet astronomers can still measure an asteroid only a few kilometers across, refine its position, estimate its shape, and occasionally discover … Read more