66 Eyes on the Sky: ALMA’s New Perspective

Jason Lozo

What did our solar system look like These tiny clumps stuck to other clumps in when it was in its infancy? What would an larger and larger sizes, colliding, shattering, outsider’s view show us? Thanks to ALMA, and re-forming in a chaotic and violent or Atacama Large Millimeter Array, a new process until eventually the solar system as radio telescope in the Atacama Desert in we know it was formed. Chile, we may now have a unique new way While this theory is widely accepted to see exactly what goes on in the early life today, since the 18th century it has fallen into of a planetary system. and out of favor several times, being The theory of the origin of our solar challenged and disputed over and over system is nothing new. In the 18th century, again. Part of the reason for the uncertainty Immanuel Kant, Pierre-Simon Laplace, and is that we have never been able to get a Emanuel Swedenborg proposed a model that bird’s eye view of this process first hand, at we still use in its refined but largely least, not until ALMA. unchanged form today. Their idea was that The ALMA radio telescope, located at some point around 4.6 billion years ago, a in the Atacama Desert in northern Chile, is pocket of swirling gas and dust collapsed in the latest international collaborative effort in on itself, gathering mass from the modern radio astronomy. It began in 1997 surrounding cloud until it was able to begin when the National Radio Astronomy fusing hydrogen, beginning the life cycle of Observatory (NRAO) in the United States a new star: our sun. In the remaining agreed to combine their efforts with the spinning disk of gas and dust, grains began European Southern Observatory (ESO) to to stick together forming small clumps. create a radio telescope with unrivaled

ALMA’s powerful dishes poised under a beautiful night sky. Credit: Christoph Malin, ESO, 2012, http://www.almaobservatory.org/en/visuals/images/?g2_itemId=4637 sensitivity and resolution. The United States Using ALMA, astronomers observed a T contributed the Millimeter Array (MMA), Tauri star named HL Tau. T Tauri stars are which offers exceptional frequency the youngest observable stars in the coverage, and the Europeans brought to the universe, still in the process of collapsing project their Large Southern Array (LSA), prior to fusion igniting in their cores and which offered unparalleled sensitivity. Later, moving them onto the main sequence. Since in 2004, the National Astronomical their core temperatures are too low for Observatory of Japan (NAOJ) would fusion, they are instead powered by the become a partner in the project, adding their release of gravitational energy as they Atacama Compact Array and three new contract. About half of the known T Tauri receiver bands to the array. stars have disks of gas and dust surrounding The array’s power as an observatory them, called protoplanetary disks because comes from the number and versatility of they are thought to be the progenitors of the antennas. Sixty-six separate antennas planetary systems. will be linked together to form what is called The ALMA astronomers found just an interferometer, which gives the telescope such a disk of gas and dust surrounding HL the effect of having a much greater diameter Tau. The disk surrounding this particular than it actually does, enhancing its ability to young star is warm enough to emit light in resolve distant objects. ALMA’s antennas the X ray bandwidth, making it appear to can be moved around the project site, giving ALMA as a glowing aura surrounding the it the ability to have separations ranging star. The accretion disk features prominent from about 150 meters to around 14 dark rings throughout, which are thought to kilometers, which gives astronomers an be regions of the young system where small instrument versatile enough to observe fledgling planets, or planetoids, are celestial objects from the very large to the “vacuuming up” all the dust and gas in their very small with better resolution than that orbits, expanding the rings as they grow from Hubble and the Very Large Array seen more and more massive. This finding in the movie Contact. appears to be direct visual evidence of This resolution allowed astronomers planets forming right before our eyes, giving to image the early stages of formation of a confirmation to the theories of the formation new planetary system like never before. of our own solar system. However, the data are not exactly configuration it was designed for, we can what astronomers expected. HL Tau is expect many more exciting discoveries in estimated to be around 100,000 years old, the future. ALMA is a gargantuan yet it already has planets forming in its undertaking by all the organizations circumstellar disk. This process was involved, but it is already clear that the previously thought to take much longer than payoff will be tremendous. According to the time period seen in HL Tau. According Tim de Zeeuw, Director General of the to Catherine Vlahakis of ALMA, "When we European Southern Observatory, “This high first saw this image we were astounded at resolution image of HL Tauri demonstrates the spectacular level of detail. HL Tauri is what ALMA can achieve when it operates in no more than a million years old, yet already its largest configuration and starts a new era its disk appears to be full of forming planets. in our exploration of the formation of stars This one image alone will revolutionize and planets.” Unique and wonderful theories of planet formation." discoveries are clearly just beyond the horizon. For more information about ALMA, please visit: • http://www.almaobservatory.org/en/a bout-alma • https://public.nrao.edu/telescopes/al ma Sources Cited NRAO. (n.d.). About ALMA. Retrieved from NRAO: https://public.nrao.edu/telescopes/alma NRAO. (n.d.). Birth of Planets Revealed in Image 1 - HL Tau and its circumstellar disk, Astonishing Detail in ALMA's 'Best Image showing prominent rings where planets are thought Ever'. Retrieved from NRAO: to be forming. https://public.nrao.edu/news/pressreleases/p Credit: ALMA (ESO/NAOJ/NRAO) anet-formation-alma http://www.eso.org/public/images/eso1436a/ O'Neill, I. (n.d.). 'Revolutionary' New View of Baby Planets Forming Around a Star. ALMA is currently approaching Retrieved from Discovery: http://news.discovery.com/space/astronom completion, and since this is its first y/revolutionary-new-view-of-baby- precision image in the almost-complete planets-forming-around-a-star- 141106.htm