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Revolutionary Image of Planet Formation Around a Young Sun-like Star

November 8, 2014

A few days ago, astronomers using the Atacama Large Millimeter Array telescope (or, ALMA) released this astonishing image:

Protoplanetary disk surrounding the young star HL Tau (Credit: ALMA (NRAO/ESO/NAOJ); C. Brogan, B. Saxton (NRAO/AUI/NSF).

Protoplanetary disk surrounding the young star HL Tau (Credit: ALMA (NRAO/ESO/NAOJ); C. Brogan, B. Saxton (NRAO/AUI/NSF).

This is an image of a protoplanetary disk — the ring of gas and dust that astronomers think surrounds most forming stars (or, protostars). The image amazes for a few reasons. It is the first image to show the detailed concentric rings indicative of planet formation in a protoplanetary disk. This visualization of real-time planet formation looks startlingly like artistic renderings of protoplanetary disks often used in interpreting fuzzy astronomical images.

Artistic rendering of a protoplanetary disk around a young star, much like HL Tau. Planets are shown forming in the gaps in the disk (Credit: National Science Foundation, A. Khan).

Artistic rendering of a protoplanetary disk around a young star, much like HL Tau. Planets are shown forming in the gaps in the disk (Credit: National Science Foundation, A. Khan).

Even more interesting, perhaps, is that the protostar, HL Taurus (often referred to as HL Tau), is less than one million years old, too young, scientists thought, to have a forming system of planets. The now certain fact that there are orbiting bodies well on their way to planet hood implies that planets can form far earlier than originally thought. An earlier history for planet formation means that initial thinking on the chemistry and physics that drive planet formation will need to be reconsidered.

HL Tau is a Sun-like protostar that resides about 450 light-years from Earth in the constellation Taurus (the Bull), but being in the pre-star phase of its evolution and surrounded by a large disk of gas and dust renders it only visible at infrared wavelengths. Being similar in mass and type to our Sun, it is one of the best analogues for the early Solar System, and astronomers study the chemistry of the gas and dust surrounding this and other protostars like it to better understand how our own planetary system evolved.

This image is particularly fascinating for me, since my colleagues and I recently submitted for publication to The Astrophysical Journal (Smith et al., now in revision) one of the most detailed chemical analyses of HL Tau taken with the powerful Very Large Telescope (VLT) in Chile. Our analyses of our very high-resolution observations of carbon monoxide absorption lines in the gas surrounding this object revealed patterns in the oxygen isotopes that are consistent with the as-yet-unexplained patterns seen in the most primitive meteorites, hinting at early solar system processes that could have contributed to this unusual chemistry.

Spectrum of carbon monoxide gas in the protoplanetary disk surrounding the young protostar HL Tau, taken with the Very Large Telescope (Credit: R. Smith, Smith et al., The Astrophysical Journal, paper in revision).

Spectrum of carbon monoxide gas in the protoplanetary disk surrounding the young protostar HL Tau, taken with the Very Large Telescope (Credit: R. Smith, Smith et al., The Astrophysical Journal, paper in revision).

Now it seems that what we once considered primitive, pre-planetary processes could in fact be affecting planets directly as they form. These new revelations will likely change how we interpret our astronomical observations, and how we understand the early chemistry affecting planet formation, organic compounds, and, eventually, life.

You can watch a brief webcast from the National Radio Astronomical Observatory discussing this new image of the HL Tau exoplanetary system below:

 

Click the highlighted links to learn more about my research on solar system origins, and the Astronomy & Astrophysics Research Lab at the Museum!

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