V883 Ori is a unique protostar whose
temperature is just hot enough that the water in its circumstellar disk has
turned to gas, making it possible for radio astronomers to trace the water's
origins. New observations with the Atacama Large Millimeter/submillimeter Array
(ALMA) have provided the first confirmation that the water in our Solar System
may come from the same place as the water in disks surrounding protostars
elsewhere in the Universe: the interstellar medium. Credit: ALMA (ESO/NAOJ/NRAO),
B. Saxton (NRAO/AUI/NSF)
Scientists
studying a nearby protostar have detected the presence of water in its
circumstellar disk. The new observations made with the Atacama Large
Millimeter/submillimeter Array (ALMA) mark the first detection of water being
inherited into a protoplanetary disk without significant changes to its
composition. These results further suggest that the water in our solar system
formed billions of years before the sun. The new observations are published
today in Nature.
V883 Orionis is a protostar located roughly 1,305 light-years from Earth in
the constellation Orion. The new observations of this protostar have helped
scientists to find a probable link between the water in the interstellar medium
and the water in our solar system by confirming they have similar composition.
"We can think of the path of water
through the universe as a trail. We know what the endpoints look like, which
are water on planets and in comets, but we wanted to trace that trail back to
the origins of water," said John Tobin, an astronomer at the National
Science Foundation's National Radio Astronomy Observatory (NRAO) and the lead
author on the new paper.
"Before now, we could link the
Earth to comets, and protostars to the interstellar medium, but we couldn't
link protostars to comets. V883 Ori has changed that, and proven the water molecules in that system and in our solar system have a
similar ratio of deuterium and hydrogen."
Observing water in the circumstellar
disks around protostars is difficult because in most systems water is present
in the form of ice. When scientists observe protostars they're looking for the
water snow line or ice line, which is the place where water transitions from
predominantly ice to gas, which radio astronomy can observe in detail.
"If the snow line is located too close to the star, there isn't enough gaseous water to be easily detectable and the dusty disk may block out a lot of the water emission. But if the snow line is located further from the star, there is sufficient gaseous water to be detectable, and that's the case with V883 Ori," said Tobin, who added that the unique state of the protostar is what made this project possible.
Most of the time, water in the circumstellar
disks surrounding protostars is in the form of ice, sometimes extending out
long distances from the star. In the case of V883 Ori, the snowline extends 80
au from the star; that's 80 times the distance between Earth and the Sun, as
shown in this animation. But, the temperature at V883 Ori is just hot enough
that much of the ice in its disk has turned to gas, making it possible for
radio astronomers to study that water in detail. New observations with the
Atacama Large Millimeter/submillimeter Array (ALMA) have revealed that the
water in V883 Ori's disk is of the same basic composition as water on objects
in our Solar System. This suggests that the water in our own Solar System
formed billions of years before the Sun in the interstellar medium. Credit:
ALMA (ESO/NAOJ/NRAO), J. Tobin, B.Saxton (NRAO/AUI/NSF)
V883 Ori's disk is quite massive
and is just hot enough that the water in it has turned from ice to gas. That
makes this protostar an ideal target for studying the growth and evolution of
solar systems at radio wavelengths.
"This observation highlights
the superb capabilities of the ALMA instrument in helping astronomers study
something vitally important for life on Earth: water," said Joe Pesce, NSF
Program Officer for ALMA. "An understanding of the underlying processes
important for us on Earth, seen in more distant regions of the galaxy, also
benefits our knowledge of how nature works in general, and the processes that
had to occur for our solar system to develop into what we know today."
To connect the water in V883 Ori's
protoplanetary disk to that in our own solar system, the team measured its
composition using ALMA's highly sensitive Band 5 (1.6mm) and Band 6 (1.3mm)
receivers and found that it remains relatively unchanged between each stage of
solar system formation: protostar, protoplanetary disk, and comets.
"This means that the water in our solar system was formed long before the sun, planets, and comets formed. We already knew that there is plenty of water ice in the interstellar medium. Our results show that this water got directly incorporated into the solar system during its formation," said Merel van 't 'Hoff, an astronomer at the University of Michigan and a co-author of the paper. "This is exciting as it suggests that other planetary systems should have received large amounts of water too."
While searching for the origins of water
in our Solar System, scientists homed in on V883 Orionis, a unique protostar
located 1,305 light-years away from Earth. Unlike with other protostars, the
circumstellar disk surrounding V883 Ori is just hot enough that the water in it
has transformed from ice into gas, making it possible for scientists to study
its composition using radio telescopes like those at the Atacama Large
Millimeter/submillimeter Array (ALMA). Radio observations of the protostar
revealed water (orange), a dust continuum (green), and molecular gas (blue)
which suggests that the water on this protostar is extremely similar to the
water on objects in our own Solar System, and may have similar origins. Credit:
ALMA (ESO/NAOJ/NRAO), J. Tobin, B. Saxton (NRAO/AUI/NSF)
Clarifying
the role of water in the development of comets and planetesimals is critical to
building an understanding of how our own solar system developed. Although the
sun is believed to have formed in a dense cluster of stars and V883 Ori is
relatively isolated with no nearby stars, the two share one critical thing in common: they
were both formed in giant molecular clouds.
"It is known that the bulk of the
water in the interstellar medium forms as ice on the surfaces of tiny dust
grains in the clouds. When these clouds collapse under their own gravity and
form young stars, the water ends up in the disks around them. Eventually, the
disks evolve and the icy dust grains coagulate to form a new solar system with
planets and comets," said Margot Leemker, an astronomer at Leiden
University and a co-author of the paper.
"We have shown that water that is produced in the clouds follows this trail virtually unchanged. So, by looking at the water in the V883 Ori disk, we essentially look back in time and see how our own solar system looked when it was much younger."
V883 Orionis is a protostar located
roughly 1,305 light-years from Earth in the constellation Orion. Credit:
IAU/Sky & Telescope
Tobin added, "Until now, the chain of water in the development of our solar system was broken. V883 Ori is the missing link in this case, and we now have an unbroken chain in the lineage of water from comets and protostars to the interstellar medium."
by Amy C. Oliver, National Radio Astronomy Observatory
Source: Millions of Galaxies Emerge in New Simulated Images From NASA's Roman | NASA
No comments:
Post a Comment