X-ray: NASA/CXC/SAO/Univ
Mexico/S. Estrada-Dorado et al.; Ultraviolet: NASA/JPL; Optical: NASA/ESA/STScI
(M. Meixner)/NRAO (T.A. Rector); Infrared: ESO/VISTA/J. Emerson; Image
Processing: NASA/CXC/SAO/K. Arcand;
A planet may have been destroyed by a white dwarf at the center of a planetary nebula — the first time this has been seen. As described in our latest press release, this would explain a mysterious X-ray signal that astronomers have detected from the
Helix Nebula for over 40 years. The Helix is a planetary nebula, a late-stage
star like our Sun that has shed its outer layers leaving a small dim star at
its center called a white dwarf.
This composite image contains X-rays from Chandra (magenta), optical light data from Hubble (orange, light blue), infrared data from ESO (gold, dark blue), and ultraviolet data from GALEX (purple) of the Helix Nebula. Data from Chandra indicates that this white dwarf has destroyed a very closely orbiting planet.
This artist’s impression shows a planet (left) that
has approached too close to a white dwarf (right) and been torn apart by tidal
forces from the star. The white dwarf is in the center of a planetary nebula
depicted by the blue gas in the background. The planet is part of a planetary
system, which includes one planet in the upper left and another in the lower
right. The besieged planet could have initially been a considerable distance
from the white dwarf but then migrated inwards by interacting with the gravity
of other planets in the system.
CXC/SAO/M.Weiss
An artist’s concept shows a planet (left) that has approached too close to
a white dwarf (right) and is being torn apart by tidal forces from the star. The white dwarf is in the center of a planetary nebula
depicted by the blue gas in the background. The planet is part of a planetary
system, which includes one planet in the upper left and another in the lower
right. The besieged planet could have initially been a considerable distance
from the white dwarf but then migrated inwards by interacting with the gravity
of the other planets in the system.
Eventually debris from the planet
will form a disk around the white dwarf and fall onto the star’s surface,
creating the mysterious signal in X-rays that astronomers have detected for
decades.
Dating back to 1980, X-ray missions, such as the Einstein Observatory and ROSAT telescope, have picked up an unusual reading from the center of the Helix Nebula. They detected highly energetic X-rays coming from the white dwarf at the center of the Helix Nebula named WD 2226-210, located only 650 light-years from Earth. White dwarfs like WD 2226-210 do not typically give off strong X-rays.
In about 5 billion years, our Sun will run out of fuel
and expand, possibly engulfing Earth. These end stages of a star’s life can be
utterly beautiful as is the case with this planetary nebula called the Helix
Nebula.
X-ray: NASA/CXC/SAO/Univ Mexico/S. Estrada-Dorado et
al.; Ultraviolet: NASA/JPL; Optical: NASA/ESA/STScI (M. Meixner)/NRAO (T.A.
Rector); Infrared: ESO/VISTA/J. Emerson; Image Processing: NASA/CXC/SAO/K.
Arcand;
A new study featuring the data from Chandra and XMM-Newton may finally have
settled the question of what is causing these X-rays from WD 2226-210: this
X-ray signal could be the debris from a destroyed planet being pulled onto the
white dwarf. If confirmed, this would be the first case of a planet seen to be
destroyed by the central star in a planetary nebula.
Observations by ROSAT, Chandra, and
XMM-Newton between 1992 and 2002 show that the X-ray signal from the white
dwarf has remained approximately constant in brightness during that time. The
data, however, suggest there may be a subtle, regular change in the X-ray
signal every 2.9 hours, providing evidence for the remains of a planet
exceptionally close to the white dwarf.
Previously scientists determined
that a Neptune-sized planet is in a very close orbit around the white dwarf —
completing one revolution in less than three days. The researchers in this
latest study conclude that there could have been a planet like Jupiter even
closer to the star. The besieged planet could have initially been a
considerable distance from the white dwarf but then migrated inwards by
interacting with the gravity of other planets in the system. Once it approached close enough to
the white dwarf the gravity of the star would have partially or completely torn
the planet apart.
WD 2226-210 has some similarities
in X-ray behavior to two other white dwarfs that are not inside planetary
nebulas. One is possibly pulling material away from a planet companion, but in
a more sedate fashion without the planet being quickly destroyed. The other
white dwarf is likely dragging material from the vestiges of a planet onto its
surface. These three white dwarfs may constitute a new class of variable, or
changing, object.
A paper describing these results
appears in The Monthly Notices of the Royal Astronomical Society and is available online. The authors of the paper are Sandino Estrada-Dorado
(National Autonomous University of Mexico), Martin Guerrero (The Institute of
Astrophysics of Andalusia in Spain), Jesús Toala (National Autonomous
University of Mexico), Ricardo Maldonado (National Autonomous University of
Mexico), Veronica Lora (National Autonomous University of Mexico), Diego
Alejandro Vasquez-Torres (National Autonomous University of Mexico), and
You-Hua Chu (Academia Sinica in Taiwan).
NASA’s Marshall Space Flight Center
manages the Chandra program. The Smithsonian Astrophysical Observatory’s
Chandra X-ray Center controls science operations from Cambridge, Massachusetts,
and flight operations from Burlington, Massachusetts.
Read
more from NASA’s Chandra X-ray Observatory.
Learn more about the Chandra X-ray
Observatory and its mission here:
Visual Description
This release features two images; a
composite image of the Helix Nebula, and an artist’s rendering of a planet’s
destruction, which may be occurring in the nebula’s core.
The Helix Nebula is a cloud of gas
ejected by a dying star, known as a white dwarf. In the composite image, the
cloud of gas strongly resembles a creature’s eye. Here, a hazy blue cloud is
surrounded by misty, concentric rings of pale yellow, rose pink, and blood
orange. Each ring appears dusted with flecks of gold, particularly the outer
edges of the eye-shape.
The entire image is speckled with
glowing dots in blues, whites, yellows, and purples. At the center of the hazy
blue gas cloud, a box has been drawn around some of these dots including a
bright white dot with a pink outer ring, and a smaller white dot. The scene
which may be unfolding inside this box has been magnified in the artist’s
rendering.
The artist’s digital rendering shows a possible cause of the large white dot with the pink outer ring. A brilliant white circle near our upper right shows a white dwarf, the ember of a dying star. At our lower left, in the relative foreground of the rendering, is what remains of a planet. Here, the planet resembles a giant boulder shedding thousands of smaller rocks. These rocks flow off the planet’s surface, pulled back toward the white dwarf in a long, swooping tail. Glowing orange fault lines mar the surface of the crumbling planet. In our upper left and lower right, inside the hazy blue clouds which blanket the rendering, are two other, more distant planets. After the rocks from the planet start striking the surface of the white dwarf, X-rays should be produced.
By: Lee Mohon
Source: X-ray Signal Points to Destroyed Planet, Chandra Finds - NASA
