The VLBI Space Observatory Programme (VSOP) mission is a Japanese-led project to study radio sources with submilliarcsecond angular resolution, using an orbiting 8 m telescope on board the satellite HALCA with a global Earth-based array of telescopes. A major program is the 5 GHz VSOP Survey Program, which we supplement here with Very Long Baseline Array observations to produce a complete and flux density-limited sample. Using statistical methods of analysis of the observed visibility amplitude versus projected (u, v) spacing, we have determined the angular size and brightness temperature distribution of bright radio emission from active galactic nuclei. On average, the cores have a diameter (full width, half-power) of 0.20 mas, which contains about 20% of the total source emission, and 14% AE 6% of the cores are less than 0.04 mas in size. About 20% AE 5% of the radio cores have a source frame brightness temperature T b > 1:0 ; 10 13 K, and 3% AE 2% have T b > 1:0 ; 10 14 K. A model of the high brightness temperature tail suggests that the radio cores have brightness temperatures %1 ; 10 12 K and are beamed toward the observer with an average bulk motion of ¼ 0:993 AE 0:004.

Prestellar cores are self-gravitating dense and cold structures within molecular clouds where future stars are born. They are expected, at the stage of transitioning to the protostellar phase, to harbor centrally concentrated dense (sub)structures that will seed the formation of a new star or the binary/multiple stellar systems. Characterizing this critical stage of evolution is key to our understanding of star formation. In this work, we report the detection of high density (sub)structures on the thousand-au scale in a sample of dense prestellar cores. Through our recent ALMA observations towards the Orion molecular cloud, we have found five extremely dense prestellar cores, which have centrally concentrated regions ∼ 2000 au in size, and several 10 7 cm −3 in average density. Masses of these centrally dense regions are in the range of 0.30 to 6.89 M . For the first time, our higher resolution observations (0.8 ∼ 320 au) further reveal that one of the cores shows clear signatures of fragmentation; such individual substructures/fragments have sizes of 800 -1700 au, masses of 0.08 to 0.84 M , densities of 2 − 8 × 10 7 cm −3 , and separations of ∼ 1200 au. The substructures are massive enough ( 0.1 M ) to form young stellar objects and are likely examples of the earliest stage of stellar embryos which can lead to widely (∼ 1200 au) separated multiple systems.

We report on OH maser emission toward G336.644−0.695 (IRAS 16333−4807), which is a H 2 O maser-emitting Planetary Nebula (PN). We have detected 1612, 1667, and 1720 MHz OH masers at two epochs using the Australia Telescope Compact Array, hereby confirming it as the seventh known case of an OH-maser-emitting PN. This is only the second known PN showing 1720 MHz OH masers after K 3−35 and the only evolved stellar object with 1720 MHz OH masers as the strongest transition. This PN is one of a group of very young PNe. The 1612 MHz and 1667 MHz masers are at a similar velocity to the 22 GHz H 2 O masers, whereas the 1720 MHz masers show a variable spectrum, with several components spread over a higher velocity range (up to 36 km s −1 ). We also detect Zeeman splitting in the 1720 MHz transition at two epochs (with field strengths of ∼2 to ∼10 mG), which suggests the OH emission at 1720 MHz is formed in a magnetized environment. These 1720 MHz OH masers may trace short-lived equatorial ejections during the formation of the PN.

We present the first 1.3 mm (230 GHz) very long baseline interferometry model image of an AGN jet using closure phase techniques with a four-element array. The model image of the quasar 1924-292 was obtained with four telescopes at three observatories: the James Clerk Maxwell Telescope (JCMT) on Mauna Kea in Hawaii, the Arizona Radio Observatory's Submillimeter Telescope (SMT) in Arizona, and

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