Download A planet is forming in an Earth-like orbit around a young star

A planet is forming in an Earth-like orbit around a young star | Astronomy.com
A planet is forming in an Earth-like orbit around a young star
By Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, NRAO,
Charlottesville, VA | Published: Thursday, March 31, 2016
ALMA image of the planet-forming disk around the young Sun-like star TW Hydrae.
The inset image (upper right) zooms in on the gap nearest to the star, which is at the
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A planet is forming in an Earth-like orbit around a young star | Astronomy.com
5/5/16, 21:12
same distance as Earth is from the Sun, suggesting an infant version of our home
planet could be emerging from the dust and gas. The additional concentric light and
dark features represent other planet-forming regions farther out in the disk.
S. Andrews (Harvard-Smithsonian CfA)/ALMA (ESO/NAOJ/NRAO)
Disks of dust and gas that surround young stars are the formation sites of planets.
New images from the Atacama Large Millimeter/submillimeter Array (ALMA) reveal
never-before-seen details in the planet-forming disk around a nearby Sun-like star,
including a tantalizing gap at the same distance from the star as Earth is from the Sun.
This structure may mean that an infant version of our home planet, or possibly a more
massive “super-Earth,” is beginning to form there.
The star, TW Hydrae, is a popular target of study for astronomers because of its
proximity to Earth — approximately 175 light-years away — and its status as a veritable
newborn — about 10 million years old. It also has a face-on orientation as seen from
Earth. This affords astronomers a rare undistorted view of the complete disk.
“Previous studies with optical and radio telescopes confirm that this star hosts a
prominent disk with features that strongly suggest planets are beginning to coalesce,”
said Sean Andrews of the Harvard-Smithsonian Center for Astrophysics in Cambridge,
Massachusetts. “The new ALMA images show the disk in unprecedented detail,
revealing a series of concentric dusty bright rings and dark gaps, including intriguing
features that suggest a planet with an Earth-like orbit is forming there.”
Other pronounced gap features are located at distances from the central star of 2
billion miles (3 billion kilometers) and 4 billion miles (6 billion km), similar to the
distances from the Sun to Uranus and Pluto in our solar system. They, too, are likely
the result of particles that came together to form planets, which then swept their orbits
clear of dust and gas and shepherded the remaining material into well-defined bands.
For the new TW Hydrae observations, astronomers imaged the faint radio emission
from millimeter-sized dust grains in the disk, revealing details on the order of about 93
million miles (150 million km), or the distance between Earth and the Sun. These
detailed observations were made possible with ALMA’s high-resolution, long-baseline
configuration. When ALMA’s dishes are at their maximum separation, up to 9 miles (15
km), the telescope is able to resolve finer details. “This is the highest spatial resolution
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A planet is forming in an Earth-like orbit around a young star | Astronomy.com
5/5/16, 21:12
image ever of a protoplanetary disk from ALMA, and that won’t be easily beat going
forward,” said Andrews.
“TW Hydrae is quite special. It is the nearest known protoplanetary disk to Earth, and it
may closely resemble our solar system when it was only 10 million years old,” said
David Wilner, also with the Harvard-Smithsonian Center for Astrophysics.
Earlier ALMA observations of another system, HL Tau, show that even younger
protoplanetary disks — a mere 1 million years old — can display similar signatures of
planet formation. By studying the older TW Hydrae disk, astronomers hope to better
understand the evolution of our own planet and the prospects for similar systems
throughout the galaxy.
The astronomers’ next phase of research is to investigate how common these kinds of
features are in disks around other young stars, and how they might change with time
or environment.
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