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: Astrophysicists offer new research, tool for identifying habitable zones

add to favorites email to friend print save as pdf

Related Stories

How was the Earth formed?

Dec 10, 2014

Just how did the Earth—our home and the place where life as we know it evolved—come to be created in the first place? In some fiery furnace atop a great mountain? On some divine forge with the hammer ...

Warm gas pours 'cold water' on galaxy's star-making

Dec 08, 2014

Some like it hot, but for creating new stars, a cool cosmic environment is ideal. As a new study suggests, a surge of warm gas into a nearby galaxy—left over from the devouring of a separate galaxy—has ...

Effects of accretion disks around newborn stars

Dec 08, 2014

Stars are born in dense, cool clouds of molecular gas and dust. When the local density is high enough, the matter can gravitationally collapse to form a new star, a so-called young stellar object (YSO). In ...

10 facts about the Milky Way

Dec 04, 2014

The Milky Way Galaxy is an immense and very interesting place. Not only does it measure some 100,000–120,000 light-years in diameter, it is home to planet Earth, the birthplace of humanity. Our Solar System ...

Recommended for you

Image: Multicoloured view of supernova remnant

13 hours ago

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make ...

Ultra-luminous X-ray sources in starburst galaxies

13 hours ago

Ultra-luminous X-ray sources (ULXs) are point sources in the sky that are so bright in X-rays that each emits more radiation than a million suns emit at all wavelengths. ULXs are rare. Most galaxies (including ...

When a bright light fades

13 hours ago

Astronomer Charles Telesco is primarily interested in the creation of planets and stars. So, when the University of Florida's giant telescope was pointed at a star undergoing a magnificent and explosive death, ...

Image: Horsehead nebula viewed in infrared

14 hours ago

Sometimes a horse of a different color hardly seems to be a horse at all, as, for example, in this newly released image from NASA's Spitzer Space Telescope. The famous Horsehead nebula makes a ghostly appearance ...

The Milky Way's new neighbour

14 hours ago

The Milky Way, the galaxy we live in, is part of a cluster of more than 50 galaxies that make up the 'Local Group', a collection that includes the famous Andromeda galaxy and many other far smaller objects. ...

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.