cometary nucleus

Most cometary nuclei are thought to be no more than about 10 miles (16 kilometers) across.

A cometary nucleus is composed of rock, dust, and frozen gases.

Cometary nuclei are among the darkest objects known to exist in the solar system.

These missions were only able to photograph and examine the surfaces of cometary nuclei from a distance.

Giotto was the first spacecraft to provide detailed pictures of a cometary nucleus.

Surprisingly, cometary nuclei are among the least reflective objects found in the Solar System.

"Turn the ship around, head back toward the cometary nucleus, and plunge the Grissom into the comet.

Cometary nuclei vary in size from a few hundreds of metres across or less to many kilometres across.

When they approach the Sun, large amounts of gas and dust are ejected by cometary nuclei, due to solar heating.

These complex molecules may exist within the cometary nucleus, or might be synthesised by reactions in the comet.

Cysat's drawings of cometary nuclei were included on the maps of others.

"My guess is a cometary nucleus.

"The Grissom will launch the probe toward a cometary nucleus on a ballistic trajectory.

In 1908, a 160-foot-wide cometary nucleus or stony meteor apparently disintegrated over Siberia at an altitude of five miles.

Of course, cometary nuclei are now known to be solid, not gaseous as Poe thought, and Earth has passed through comet tails without incident.

The coma of a comet is a very large but very tenuous atmosphere of dust and gas around the cometary nucleus.

An electromagnetic wave-front propagates through the cometary nucleus at a smaller velocity than in free space and loses energy in the process.

Astronomers said the echoes clearly showed the presence of a cometary nucleus surrounded by a coma consisting partly of gravel-size particles.

D-type and P-type asteroids have surface colors, and thus also surface mineralogies, similar to those of cometary nuclei.

None of the other three asteroids showed signs of the cometary emission that would be expected from a weakly active cometary nucleus.

It is therefore likely that the Comet of 1729 was an exceptionally large object, with a cometary nucleus of the order of 100 km in diameter.

Deep-freeze relics of the early solar system, cometary nuclei are porous and fragile mixes of dust and ices.

They appear to have resulted from the breaking off of fragments of the cometary nucleus - fragments that are emitting luminous gas and dust like miniature comets.

With a trillion cometary nuclei, each separated from the next by about as much as Mars is from Earth, there will be a great deal to do out there.

As well as these molecules, emission from heavy atoms such as iron, magnesium and silicon was detected, with abundances consistent with what would be found in a cometary nucleus.