2024年12月9日 · Comets are cosmic snowballs of frozen gases, rock, and dust that orbit the Sun. When frozen, they are the size of a small town. When a comet’s orbit brings it close to the Sun, it heats up and spews dust and gases into a giant glowing head larger than most planets.

2025年1月14日 · Comets are large objects made of dust and ice that orbit the Sun. Best known for their long, streaming tails, these ancient objects are leftovers from the formation of the solar system 4.6 billion years ago. Comets, such as the comet ISON pictured here, are thought to hold material from the time when the Sun and planets were forming.

2024年7月25日 · A comet warms up as it nears the Sun and develops an atmosphere, or coma. The Sun’s heat causes the comet’s ices to change to gases so the coma gets larger. The coma may extend hundreds of thousands of kilometers.

5 天之前 · Pictured are images of Comet G3 ATLAS on successive January nights taken from Río Hurtado, Chile. Clearly, the comet's head is brighter and more centrally condensed on the earlier days (left) than on later days (right). A key reason is likely that the comet's nucleus of ice and rock, at the head's center, has fragmented.

2024年10月11日 · The comet hails from the Oort Cloud, which scientists think is a giant spherical shell surrounding our solar system. It is like a big, thick-walled bubble made of icy pieces of space debris the sizes of mountains and sometimes larger.

5 天之前 · In mid-January 2025, the ESA (European Space Agency) and NASA Solar and Heliospheric Observatory (SOHO) watched comet C/2024 G3 (ATLAS) pass about 8 million miles from the Sun. In this image sequence, captured by SOHO’s Large Angle and Spectrometric Coronagraph (LASCO), the Sun is blocked by a disk (at the bottom), and the white circle …

2022年4月12日 · NASA’s Hubble Space Telescope has determined the size of the largest icy comet nucleus ever seen by astronomers. The estimated diameter is approximately 80 miles across, making it larger than the state of Rhode Island.

2000年6月7日 · * Comets are small, fragile, irregularly shaped bodies composed of a mixture of grains and frozen gases. They have highly elliptical orbits that repeatedly bring them very close to the Sun and then swing them deeply into space, often beyond the orbit of Pluto.

2023年5月15日 · Using Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, astronomers have confirmed gas – specifically water vapor – around a comet in the main asteroid belt for the first time, indicating that water ice from the primordial solar system can be …

2025年1月13日 · A bright comet could be visible in skies across the globe over the coming days for the first time in 160,000 years. Nasa said the future brightness of a comet is "notoriously hard" to predict, but ...