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Author(s): John J. Tobin (corresponding author) [1, 2]; Kaitlin M. Kratter [3]; Magnus V. Persson [2, 4]; Leslie W. Looney [5]; Michael M. Dunham [6]; Dominique Segura-Cox [5]; Zhi-Yun Li [...]

Author(s): John J. Tobin (corresponding author) [1]; Lee Hartmann [2]; Hsin-Fang Chiang [3, 4]; David J. Wilner [5]; Leslie W. Looney [3]; Laurent Loinard [6, 7]; Nuria Calvet [2]; Paola [...]

In their earliest stages, protostars accrete mass from their surrounding envelopes through circumstellar disks. Until now, the smallest observed protostar-to-envelope mass ratio was about 2. 1 (ref. 1). The protostar L1527 IRS is thought to be in the earliest stages of star formation (2). Its envelope contains about one solar mass of material within a radius of about 0.05 parsecs (refs 3,4), and earlier observations suggested the presence of an edge-on disk (5). Here we report observations of dust continuum emission and [sup.13]CO (rotational quantum number J = 2 [right arrow] 1) line emission from the disk around L1527 IRS, from which we determine a protostellar mass of 0.19 ± 0.04 solar masses and a protostar-to-envelope mass ratio of about 0.2. We conclude that most of the luminosity is generated through the accretion process, with an accretion rate of about 6.6 x [10.sup.-7] solar masses per year. If it has been accreting at that rate through much of its life, its age is approximately 300,000 years, although theory suggests larger accretion rates earlier (6), so it may be younger. The presence of a rotationally supported disk is confirmed, and significantly more mass may be added to its planet-forming region as well as to the protostar itself in the future., The protostar L1527 IRS (hereafter L1527), at a distance of about 140 pc, is one of the nearest class 0 protostars; this is the earliest phase of the star formation [...]

Water is a fundamental molecule in the star and planet formation process, essential for catalysing the growth of solid material and the formation of planetesimals within disks 1,2 . However, the water snowline and the HDO:H 2 O ratio within proto-planetary disks have not been well characterized because water only sublimates at roughly 160 K (ref. 3 ), meaning that most water is frozen out onto dust grains and that the water snowline radii are less than 10 AU (astronomical units) 4,5 . The sun-like protostar V883 Ori (M *  = 1.3 M ⊙ ) 6 is undergoing an accretion burst 7 , increasing its luminosity to roughly 200 L ⊙ (ref. 8 ), and previous observations suggested that its water snowline is 40-120 AU in radius 6,9,10 . Here we report the direct detection of gas phase water (HDO and [Formula: see text]) from the disk of V883 Ori. We measure a midplane water snowline radius of approximately 80 AU, comparable to the scale of the Kuiper Belt, and detect water out to a radius of roughly 160 AU. We then measure the HDO:H 2 O ratio of the disk to be (2.26 ± 0.63) × 10 -3 . This ratio is comparable to those of protostellar envelopes and comets, and exceeds that of Earth's oceans by 3.1σ. We conclude that disks directly inherit water from the star-forming cloud and this water becomes incorporated into large icy bodies, such as comets, without substantial chemical alteration., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)