Astronomers have detected a large amount of water vapour in the protoplanetary disk around a young star. There\u2019s at least three times as much water among the dust as there is in all of Earth\u2019s oceans combined. And it\u2019s not spread throughout the disk; it\u2019s concentrated in the inner disk region.<\/p>\n
<\/p>\n No water means no life, so finding this much water in the part of a protoplanetary disk where rocky planets form is an intriguing discovery. And this isn\u2019t just any disk. It\u2019s a cold, stable disk, the type most likely to form planets. <\/p>\n The findings are presented in a new paper published in Nature Astronomy. It\u2019s titled \u201cResolved ALMA observations of water in the inner astronomical units of the HL Tau disk.\u201d The lead author is Stefano Facchini, an astronomer at the Dipartimento di Fisica, Universit\u00e0 degli Studi di Milano, Milano, Italy.<\/p>\n \u201cI had never imagined that we could capture an image of oceans of water vapour in the same region where a planet is likely forming,\u201d said Facchini.<\/p>\n The star, HL Tau (HL Tauri), is a young star about 450 light-years away. It\u2019s likely less than 100,000 years old, making it a prime observing target in the quest to understand planet formation. When it comes to seeing inside the gas and dust surrounding young stars like this, ALMA is our best tool. One of ALMA\u2019s first high-resolution images is of HL Tau and its disk. The image shows rings in the disk that indicate where young planets are probably forming. <\/p>\n HL Tau has always intrigued scientists, and now that they\u2019ve detected such a large amount of water vapour in its planet-forming disk, the young star is an even more compelling target for observations. <\/p>\n \u201cThese observations pave the way to the characterization of the water content of the inner regions of protoplanetary disks,\u201d the researchers write in their paper. \u201cThe tremendous angular resolution and sensitivity of the ALMA telescope, even in spectral ranges of low atmospheric transmission, are providing spatially and spectrally resolved images of the vapour of the main water isotopologue in a planet-forming disk.\u201d<\/p>\n Not only did ALMA detect the water, but it also determined where it is in the disk and how much of it there is. \u201cOur analysis implies a stringent lower limit of 3.7 Earth oceans of water vapour available within the inner 17 astronomical units of the system,\u201d the researchers write in their paper. <\/p>\n When planets take shape in a protoplanetary disk like the one around HL Tauri, they clear out lanes in the dust. Nothing else is likely to create the tell-tale gaps that signal the presence of young, still-forming planets. We have the powerful ALMA to thank for this understanding. <\/p>\n \u201cIt is truly remarkable that we can not only detect but also capture detailed images and spatially resolve water vapour at a distance of 450 light-years from us,\u201d said study co-author Leonardo Testi, an astronomer at the University of Bologna, Italy. The spatial resolution Testi is referring to is thanks to ALMA. The radio interferometer allowed astronomers to see how the water vapour is distributed throughout the disk. \u201cTaking part in such an important discovery in the iconic HL Tauri disc was beyond what I had ever expected for my first research experience in astronomy,\u201d added Mathieu Vander Donckt from the University of Lie?ge, Belgium, a master\u2019s student when he participated in the research.<\/p>\n ALMA is a radio interferometer, meaning it observes wavelengths from 0.3 mm to 3.6 mm, which correspond to the range from 84 GHz to 950 GHz. In this study, the researchers observed different \u201cflavours\u201d of water molecules at different temperatures. \u201cWe observed HL Tau in two different ALMA bands (band 5, originally developed with the goal of studying water in the local Universe, and band 7) to target three transitions of water,\u201d the researchers explain. <\/p>\n The observations didn\u2019t just find water in the inner region where rocky planets form. It found water in one of the gaps that indicate a planet is sweeping up disk material and adding it to its mass. \u201cOur recent images reveal a substantial quantity of water vapour at a range of distances from the star that includes a gap where a planet could potentially be forming at the present time,\u201d said Facchini. The natural conclusion is that the water is becoming part of the planet. <\/p>\n These results are all thanks to ALMA\u2019s power. It\u2019s the only facility we have that can detect water in a disk like this. \u201cTo date, ALMA is the only facility able to spatially resolve water in a cool planet-forming disc,\u201d said study co-author Wouter Vlemmings, a professor at the Chalmers University of Technology in Sweden.<\/p>\n ALMA\u2019s different observational frequencies capture water as it transitions, and part of this research looks at water as it\u2019s liberated from dust particles. The relationship between water and dust in a planet-forming disk is important. Where it\u2019s cold enough for water to freeze onto dust particles, the particles stick together more readily, aiding the planet formation process.<\/p>\n \u201cIt is truly exciting to directly witness, in a picture, water molecules being released from icy dust particles,\u201d said Elizabeth Humphreys, an astronomer at ESO who also participated in the study. <\/p>\n \n![\"This](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2024\/02\/Water-Vapour-HL-Tauri.png\")