The Solar System

Some shapes suggest bubbles

being inflated in the interstellar

medium. The Cat’s Eye is shown

at left, below, and on the facing

page.

The purple glow in the image above

is a region of X-ray bright gas with a

temperature measured in millions of

degrees. It is apparently driving the

The Hour Glass Nebula expansion of the nebula.

The Cat’s Eye Nebula

Menzel 3

The Egg Nebula

NASA
NASA

3.3 Visual NASA

NASA

NASA

Visual

Infrared

Jet

Disk

Jet

Visual

Visual + X-ray

Visual

Visual

Visual

The Egg Nebula

M2-9

The Cat’s Eye Nebula

Some planetary nebulae, such as

M2-9, are highly elongated, and it

has been suggested that the Ring

Nebula, at left, is a tubular shape

that happens to be pointed

roughly at Earth.

At visual wavelengths, the Egg

Nebula is highly elongated, as

shown below. The infrared image

at left reveals an irregular, thick

disk from which jets of gas and

dust emerge. Such beams may

create many of the asymmetries

in planetary nebulae.

3 Images from the Hubble Space Telescope reveal that

asymmetry is the rule in planetary nebulae rather than the

exception. A number of causes have been suggested. A disk of gas

around a star’s equator might form during the slow-wind stage and

then deflect the fast wind into oppositely directed flows. Another star

or planets orbiting the dying star, rapid rotation, or magnetic fields

might cause these peculiar shapes. The Hour Glass Nebula seems

to have formed when a fast wind overtook an equatorial disk (white

in the image). The nebula Menzel 3, as do many planetary nebulae,

shows evidence of multiple ejections.

4 Once an aging giant star

blows its surface into space to

form a planetary nebula, the remaining

hot interior collapses into a small,

intensely hot object containing a

carbon and oxygen interior surrounded

by hydrogen and helium fusion shells

and a thin atmosphere of hydrogen.

The fusion gradually dies out, and the

core of the star evolves to the left of

the conventional H–R diagram to

become the intensely hot nucleus of

a planetary nebulae. Mathematical

models show that these nuclei cool

slowly to become white dwarfs.

Hubble Heritage Team, AURA/STScI/NASAM57 The Ring Nebula Visual

JPL/NASA

106

104

102

1

10 –2

10 –4

100,00050,00030,000 10,000 5000

Mathematical

model of an 0.8-

solar-mass stellar

remnant contracting to

become a white dwarf.

Mathematical

model of an 0.8-

solar-mass stellar

remnant contracting to

become a white dwarf.

L/L

Temperature (K)

100,00050,00030,000 10,000 5000

Supe

rgiants

Giant

s

Wh

ite

dw

arfs

Ma

ins

equ

en

ce

Nuclei of

planetary

nebulae