Hubble Reveals Two Dust Disks Around Nearby Star

Jun 27, 2006
Hubble Reveals Two Dust Disks Around Nearby Star
Credit: Credit: NASA, ESA, D. Golimowski (Johns Hopkins University), D. Ardila (IPAC), J. Krist (JPL), M. Clampin (GSFC), H. Ford (JHU), and Garth Illingworth (UCO/Lick) and the ACS Science Team

NASA's Hubble Space Telescope has revealed two dust disks circling the nearby star Beta Pictoris. The images confirm a decade of scientific speculation that a warp in the young star's dust disk may actually be a second inclined disk, which is evidence for the possibility of at least one Jupiter-size planet orbiting the star.

The disk is fainter than the star because, at the visible wavelengths measured, its dust only reflects light. To see the faint disk, astronomers used Hubble’s Advanced Camera for Surveys' coronagraph, which blocked the light from Beta Pictoris. The images clearly show a distinct secondary disk that is tilted by about four degrees from the main disk. The secondary disk is visible out to roughly 24 billion miles from the star, and probably extends even farther. The finding appears in the June 2006 issue of the Astronomical Journal.

The best explanation for the observations is that a suspected unseen planet, up to 20 times the mass of Jupiter and in an orbit within the secondary disk, is using gravity to sweep up material from the primary disk.

"The Hubble observation shows that it is not simply a warp in the dust disk but two concentrations of dust in two separate disks," said lead astronomer David Golimowski of Johns Hopkins University in Baltimore. "The finding suggests that planets could be forming in two different planes. We know this can happen because the planets in our solar system are typically inclined to Earth's orbit by several degrees. Perhaps stars forming more than one dust disk may be the norm in the formative years of a star system."

Computer models by David Mouillet and Jean-Charles Augereau of Grenoble Observatory in France suggest how a secondary dust disk can form. A massive planet in an inclined orbit gravitationally attracts small bodies of rock and/or ice, called planetesimals, from the main disk, and moves them into an orbit aligned with that of the planet.

These perturbed planetesimals then collide with each other, producing the tilted dust disk seen in the new Hubble images.

"The actual lifetime of a dust grain is relatively short, maybe a few hundred thousand years," Golimowski said. "So the fact that we can still see these disks around a 10- to 20-million-year-old star means that the dust is being replenished by collisions between planetesimals."

Astronomers do not know how the massive planet, if it exists, settled into an inclined orbit. However, computer simulations by multiple research teams show planet embryos, which start out in a very thin plane, can, through gravitational interactions, scatter into orbits that become inclined to the primary disk.

Beta Pictoris is located 63 light-years away in the southern constellation Pictor. Although the star is much younger than the sun, it is twice as massive and nine times more luminous. Beta Pictoris entered the limelight more than 20 years ago when the multinational Infrared Astronomical Satellite detected excess infrared radiation from the star. Astronomers attributed this excess to the presence of warm dust in a disk around the star. The dust disk was first imaged by ground-based telescopes in 1984. The images showed the disk is seen nearly edge-on from Earth. Hubble observations in 1995 revealed an apparent warp in the disk. Subsequent images obtained in 2000 by Hubble's Imaging Spectrograph confirmed the warp.

The latter study was led by Sara Heap of NASA's Goddard Space Flight Center in Greenbelt, Md. Heap and her colleagues suggested the apparent warp may be an unresolved secondary disk tilted about four degrees from the main disk. Several teams of astronomers attributed the warp to a planet in a tilted orbit out of the plane of the main disk.

Astronomers using ground-based telescopes also found various asymmetries in the star's disk. Infrared images taken in 2002 by the Keck II Observatory in Hawaii showed that another smaller inner disk may exist around the star in a region the size of our solar system. Golimowski's team did not spot the inner disk because it is small and blocked by the Advanced Camera's coronagraph. This possible inner disk is tilted in the opposite direction from the disk seen in the new Hubble images. This misalignment implies the tilted disks are not directly related. Nevertheless, they both may bolster evidence for the existence of one or more planets orbiting the star.

Source: NASA

Explore further: Possible bright supernova lights up spiral galaxy M61

add to favorites email to friend print save as pdf

Related Stories

Image: Hubble views the whirling disk of NGC 4526

Oct 30, 2014

This neat little galaxy is known as NGC 4526. Its dark lanes of dust and bright diffuse glow make the galaxy appear to hang like a halo in the emptiness of space in this image from the NASA/ESA Hubble Space ...

Planet-forming lifeline discovered in a binary star system

Oct 29, 2014

Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) have detected a streamer of dust and gas flowing from a massive outer disk toward the inner reaches of a binary star system. This never-before-seen ...

Hubble finds jets and explosions in NGC 7793

Sep 29, 2014

( —This new image from the NASA/ESA Hubble Space Telescope shows NGC 7793, a spiral galaxy in the constellation of Sculptor some 13 million light-years away from Earth. NGC 7793 is one of the brightest ...

Light scattering on dust holds clues to habitability

Sep 25, 2014

We are all made of dust. Dust particles can be found everywhere in space. Disks of dust and debris swirl around and condense to form stars, planets and smaller objects like comets, asteroids and dwarf planets. ...

Recommended for you

Possible bright supernova lights up spiral galaxy M61

1 hour ago

I sat straight up in my seat when I learned of the discovery of a possible new supernova in the bright Virgo galaxy M61. Since bright usually means close, this newly exploding star may soon become visible ...

Fifteen years of NASA's Chandra X-ray observatory

2 hours ago

This Chandra X-ray Observatory image of the Hydra A galaxy cluster was taken on Oct. 30, 1999, with the Advanced CCD Imaging Spectrometer (ACIS) in an observation that lasted about six hours.

Confirming a 3-D structural view of a quasar outflow

2 hours ago

A team of astronomers have observed a distant gravitationally-lensed quasar (i.e., an active galactic nucleus) with the Subaru Telescope and concluded that the data indeed present a 3-D view of the structure ...

Hubble sees 'ghost light' from dead galaxies

17 hours ago

( —NASA's Hubble Space Telescope has picked up the faint, ghostly glow of stars ejected from ancient galaxies that were gravitationally ripped apart several billion years ago. The mayhem happened ...

When did galaxies settle down?

Oct 30, 2014

Astronomers have long sought to understand exactly how the universe evolved from its earliest history to the cosmos we see around us in the present day. In particular, the way that galaxies form and develop ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.