ALMA Eyes Icy Ring around Young Planetary System

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ALMA Eyes Icy Ring around Young Planetary System

Postby bystander » Thu May 18, 2017 4:18 pm

ALMA Eyes Icy Ring around Young Planetary System
ALMA | NRAO | NAOJ | ESO | 2017 May 18

Observations Suggest Chemical Kinship to Comets in Our Own Solar System

Click to view full size image 1 or image 2
Composite image of the Fomalhaut star system. The ALMA data, shown in orange, reveal
the distant and eccentric debris disk in never-before-seen detail. The central dot is the
unresolved emission from the star, which is about twice the mass of the Sun. Optical
data from the Hubble Space Telescope is in blue; the dark region is a coronagraphic
mask, which filtered out the otherwise overwhelming light of the central star.
Credit: ALMA (ESO/NAOJ/NRAO), M. MacGregor;
NASA/ESA Hubble, P. Kalas; B. Saxton (NRAO/AUI/NSF)

An international team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) has made the first complete millimeter-wavelength image of the ring of dusty debris surrounding the young star Fomalhaut. This remarkably well-defined band of rubble and gas is likely the result of exocomets smashing together near the outer edges of a planetary system 25 light-years from Earth.

Earlier ALMA observations of Fomalhaut — taken in 2012 when the telescope was still under construction – revealed only about one half of the debris disk. Though this first image was merely a test of ALMA’s initial capabilities, it nonetheless provided tantalizing hints about the nature and possible origin of the disk.

The new ALMA observations offer a stunningly complete view of this glowing band of debris and also suggest that there are chemical similarities between its icy contents and comets in our own solar system. ...

Fomalhaut is a relatively nearby star system and one of only about 20 in which planets have been imaged directly. The entire system is approximately 440 million years old, or about one-tenth the age of our solar system.

As revealed in the new ALMA image, a brilliant band of icy dust about 2 billion kilometers wide has formed approximately 20 billion kilometers from the star.

Debris disks are common features around young stars and represent a very dynamic and chaotic period in the history of a solar system. Astronomers believe they are formed by the ongoing collisions of comets and other planetesimals in the outer reaches of a recently formed planetary system. The leftover debris from these collisions absorbs light from its central star and reradiates that energy as a faint millimeter-wavelength glow that can be studied with ALMA.

Using the new ALMA data and detailed computer modeling, the researchers were able to calculate the precise location, width, and geometry of the disk. These parameters confirm that such a narrow ring is likely produced through the gravitational influence of planets in the system ...

A Complete ALMA Map of the Fomalhaut Debris Disk - Meredith A. MacGregor et al
Detection of Exocometary CO Within the 440-Myr-old Fomalhaut Belt:
A Similar CO+CO2 Ice Abundance in Exocomets and Solar System Comets
- Luca Matrà et al
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