The Solar System

PART 4 | THE SOLAR SYSTEM

Thecoma of a comet is

the cloud of gas and dust

that surrounds the nucleus. It can

be over 1,000,000 km in diameter,

bigger than the sun.

Atype II

ordust

tail is produced

by dust that was

contained in the the

vaporizing ices of the

nucleus. The dust is pushed

gently outward by the pressure of

sunlight, and it reflects an absorption

spectrum, the spectrum of sunlight. The

dust is not affected by the magnetic field of

the solar wind, so dust tails are more uniform

than gas tails. Dust tails are often curved because

the dust particles follow their individual orbits around

the sun once they leave the nucleus. Because of the

forces acting on them, both gas and dust tails extend away

from the sun.

Comet Mrkos in

1957 shows how

the gas tail can change

from night to night due

to changes in the

magnetic field in the

solar wind.

The nucleus of
a comet (not visible
here) is a small, fragile lump of
porous rock containing ices of
water, carbon dioxide, ammonia,
and so on. Comet nuclei can be
10 to 100 km in diameter.

Thecoma of a comet is

the cloud of gas and dust

that surrounds the nucleus. It can

be over 1,000,000 km in diameter,

bigger than the sun.

Atype II

ordust

tail is produced

by dust that was

contained in the

vaporizing ices of the

nucleus. The dust is pushed

gently outward by the pressure of

sunlight, and it reflects an absorption

spectrum, the spectrum of sunlight. The

dust is not affected by the magnetic field of

the solar wind, so dust tails are more uniform

than gas tails. Dust tails are often curved because

the dust particles follow their individual orbits around

the sun once they leave the nucleus. Because of the

forces acting on them, both gas and dust tails extend away

from the sun.

Nucleus

Coma

Gas tail

(Type I)

Dust tail

(Type II)

Visual-wavelength images

Caltech

1

1a

1b

1c

Atype I or gas tail is produced by

ionized gas carried away from the

nucleus by the solar wind. The spectrum of

a gas tail is an emission spectrum. The

atoms are ionized by the ultraviolet light in

sunlight. The wisps and kinks in gas tails

are produced by the magnetic field

embedded in the solar wind.

Spectra of gas tails reveal atoms and ions

such as H 2 O, CO 2 , CO, H, OH, O, S, C,

and so on. These are released by the

vaporizing ices or produced by the

breakdown of those molecules. Some

gases, such as hydrogen cyanide (HCN),

must be formed by chemical reactions.

Atype I or gas tail is produced by
ionized gas carried away from the
nucleus by the solar wind. The spectrum of
a gas tail is an emission spectrum. The
atoms are ionized by the ultraviolet light in
sunlight. The wisps and kinks in gas tails
are produced by the magnetic field
embedded in the solar wind.

Spectra of gas tails reveal atoms and ions
such as H 2 O, CO 2 , CO, H, OH, O, S, C,
and so on. These are released by the
vaporizing ices or produced by the
breakdown of those molecules. Some
gases, such as hydrogen cyanide (HCN),
must be formed by chemical reactions.

Comet Mrkos in

1957 shows how

the gas tail can change

from night to night due

to changes in the

magnetic field in the

solar wind.

The nucleus of
a comet (not visible
here) is a small, fragile lump of
porous rock containing ices of
water, carbon dioxide, ammonia,
and so on. Comet nuclei can be
1 to 100 km in diameter.