Astronomers discover ‘snow line’ on exoplanet

Scientists observing a newborn star and its newly emerging solar system may have traced where future comets and some dwarf planets may eventually arise. The team, which includes researchers from North America, Europe, and Asia, calculated the location of its “carbon monoxide snow line,” the point within the disk of matter surrounding the nascent star that carbon monoxide freezes.

They discerned this point to lie at a distance from the star roughly equivalent to the distance between our sun and Neptune. The freezing gases would be important to the formation of the solar system’s outer edges at this distance, the scientists explained.
According to Chunhua Qi,

astrophysicist with the Harvard-Smithsonian Center for Astrophysics and the study’s principal researcher, different elements and compounds have different snow lines of their own, and each one has considerable bearing on the formation of planets and other orbiting bodies. Water’s snow line, for instance, is a vast gulf of distance closer to the given system’s star.

Any solar system begins with huge clouds of gas and dust spinning around a new star. Gravity and particle bonds bring clumps of matter together, and progressively more matter joins with them to gradually form large planets, comets, asteroids, and moons. Frozen compounds—whether they’re carbon monoxide, ice, or any other “volatile”—help the formation processes along by providing more solid grains to which particles can attach.

Finding any volatile from afar, including carbon monoxide, is a challenge. Qi and his colleagues worked around this by searching not for carbon monoxide, but for signs of its effects. From the Chile-based Atacama Large Millimeter Array (ALMA), they scanned the TW Hydrae system for an ion called diazenylium (N2H+). Carbon monoxide gas destroys N2+, so when the ion is abundant, that is a clear sign that the carbon monoxide has frozen out.

Other researchers might cross-apply these snow-line-assessment techniques to more stars. TW Hydrae is a great test case, in part because of its relative closeness to Earth—its location in the constellation Hydra, at just 176 light-years away, makes it the nearest star with an orbiting disk rich in gases. Also important is its size: According to Qi and his colleagues, our sun and solar system were of very similar proportions in their earliest stages.

As such, the snow lines of our own solar system might be strikingly similar to the ones that research find in the TW Hydrae star system. We could learn more about our own solar system’s earliest years by studying this newest arrival.sciencerecorder