HR 4796A Stellar Dust Disk
This is a Hubble Space Telescope photo of a vast, complex dust
structure, about 150 billion miles across, enveloping the young star HR
4796A. A bright, narrow inner ring of dust is already known to encircle
the star and may have been corralled by the gravitational pull of an
unseen giant planet. This newly discovered huge dust structure around
the system may have implications for what this yet-unseen planetary
system looks like around the 8-million-year-old star, which is in its
formative years of planet construction. The debris field of very fine
dust was likely created from collisions among developing infant planets
near the star, evidenced by a bright ring of dusty debris seen 7 billion
miles from the star. The pressure of starlight from the star, which is
23 times more luminous than the Sun, then expelled the dust far into
space. Credit: NASA, ESA, and G. Schneider (University of Arizona)
Astronomers have used NASA’s Hubble Space Telescope to uncover a
vast, complex dust structure, about 150 billion miles across, enveloping
the young star HR 4796A. A bright, narrow, inner ring of dust is
already known to encircle the star and may have been corralled by the
gravitational pull of an unseen giant planet. This newly discovered huge
structure around the system may have implications for what this
yet-unseen planetary system looks like around the 8-million-year-old
star, which is in its formative years of planet construction.
The debris field of very fine dust was likely created from collisions
among developing infant planets near the star, evidenced by a bright
ring of dusty debris seen 7 billion miles from the star. The pressure of
starlight from the star, which is 23 times more luminous than the Sun,
then expelled the dust far into space.
But the dynamics don’t stop there. The puffy outer dust structure is
like a donut-shaped inner tube that got hit by a truck. It is much more
extended in one direction than in the other and so looks squashed on one
side even after accounting for its inclined projection on the sky. This
may be due to the motion of the host star plowing through the
interstellar medium, like the bow wave from a boat crossing a lake. Or
it may be influenced by a tidal tug from the star’s red dwarf binary
companion (HR 4796B), located at least 54 billion miles from the primary
star.
“The dust distribution is a telltale sign of how dynamically
interactive the inner system containing the ring is," said Glenn
Schneider of the University of Arizona, Tucson, who used Hubble’s Space
Telescope Imaging Spectrograph (STIS) to probe and map the small dust
particles in the outer reaches of the HR 4796A system, a survey that
only Hubble’s sensitivity can accomplish.
“We cannot treat exoplanetary debris systems as simply being in
isolation. Environmental effects, such as interactions with the
interstellar medium and forces due to stellar companions, may have
long-term implications for the evolution of such systems. The gross
asymmetries of the outer dust field are telling us there are a lot of
forces in play (beyond just host-star radiation pressure) that are
moving the material around. We’ve seen effects like this in a few other
systems, but here’s a case where we see a bunch of things going on at
once,” Schneider further explained.
Though long hypothesized, the first evidence for a debris disk around
any star was uncovered in 1983 with NASA’s Infrared Astronomical
Satellite. Later photographs revealed an edge-on debris disk around the
southern star Beta Pictoris. In the late 1990s, Hubble’s
second-generation instruments, which had the capability of blocking out
the glare of a central star, allowed many more disks to be photographed.
Now, such debris rings are thought to be common around stars. About 40
such systems have been imaged to date, largely by Hubble.
Schneider’s paper appears in the February 2018 Astronomical Journal.
The Hubble Space Telescope is a project of international cooperation
between NASA and ESA (European Space Agency). NASA’s Goddard Space
Flight Center in Greenbelt, Maryland, manages the telescope. The Space
Telescope Science Institute (STScI) in Baltimore conducts Hubble science
operations. STScI is operated for NASA by the Association of
Universities for Research in Astronomy, Inc., in Washington, D.C.
Releated links
Contact
Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu
Glenn Schneider
The University of Arizona, Tucson, Arizona
520-621-5865
gschneider@as.arizona.edu
