Click on the image for animation
Birth of 'Phoenix' Planets?
This artist's concept depicts a type of dead star called a pulsar and the
surrounding disk of rubble discovered by NASA's Spitzer Space Telescope.
The pulsar, called 4U 0142+61, was once a massive star until about 100,000
years ago when it blew up in a supernova explosion and scattered dusty
debris into space. Some of that debris was captured into what astronomers
refer to as a "fallback disk," now circling the remaining stellar core, or
pulsar. The disk resembles protoplanetary disks around young stars, out of
which planets are thought to be born.
Supernovas are a source of iron, nitrogen and other "heavy metals" in the
universe. They spray these elements out into space, where they eventually
come together in clouds that give rise to new stars and planets. The
Spitzer finding demonstrates that supernovas might also contribute heavy
metals to their own planets, a possibility that was first suggested when
astronomers discovered planets circling a pulsar called PSR B1257+12 in
1992.
Birth of 'Phoenix' Planets? About the Movie
This artist's animation depicts the explosive death of a massive star,
followed by the creation of a disk made up of the star's ashes. NASA's
Spitzer Space Telescope was able to see the warm glow of such a dusty disk
using its heat-seeking infrared vision. Astronomers believe planets might
form in this dead star's disk, like the mythical Phoenix rising up out of
the ashes.
The movie begins by showing a dying massive star called a red giant. This
bloated star is about 15 times more massive than our sun, and
approximately 40 times bigger in diameter. When the star runs out of
nuclear fuel, it collapses and ultimately blows apart in what is called a
supernova. A lone planet around the star is shown being incinerated by the
fiery blast. Astronomers do not know if stars of this heft host planets,
but if they do, the planets would probably be destroyed when the stars
explode.
All that remains of the dead star is its shrunken corpse, called a neutron
star. Neutron stars are incredibly dense, with masses nearly
one-and-one-half times that of our sun squeezed into bodies roughly 10
miles wide (16 kilometers). They are so dense that their gravity causes
light to bend and warp around them. The particular neutron star depicted
here, called a pulsar, spins and pulses with X-ray radiation.
Some debris, or ashes, from the supernova can be seen settling into a disk
in orbit around the pulsar. This material never reached the velocity
needed to escape the gravity of the pulsar, and can be thought of as
falling back toward the star. The resulting "fallback disk" resembles
protoplanetary disks around young stars, out of which planets are thought
to form.
The pulsar observed by Spitzer, called 4U 0142+61, is13,000 light-years
away in the northern constellation Cassiopeia. Its disk orbits about 1
million miles (1.6 million kilometers) away from it, and probably contains
about 10 Earth-masses of material -- only a few millionths of the mass of
the material expelled in the supernova.
At the end of the movie, small asteroids begin to form within the disk.
This first step towards planet formation might be happening in this system
already.