We present the results of multi-epoch very long baseline interferometry (VLBI) water (H 2 O) maser observations carried out with the VLBI Exploration of Radio Astrometry (VERA) toward the Cepheus A HW3d object. We measured for the first time relative proper motions of the H 2 O maser features, whose spatio-kinematics traces a compact bipolar outflow. This outflow looks highly collimated and expanding through ∼ 280 AU (400 mas) at a mean velocity of ∼ 21 km s −1 (∼ 6 mas yr −1 ) without taking into account the turbulent central maser cluster. The opening angle of the outflow is estimated to be ∼ 30 • . The dynamical time-scale of the outflow is estimated to be ∼ 100 years. Our results provide strong support that HW3d harbors an internal massive young star, and the observed outflow could be tracing a very early phase of star formation. We also have analyzed Very Large Array (VLA) archive data of 1.3 cm continuum emission obtained in 1995 and 2006 toward Cepheus A. The comparative result of the HW3d continuum emission suggests the possibility of the existence of distinct young stellar objects (YSOs) in HW3d and/or strong variability in one of their radio continuum emission components.

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Planetary nebulae (PNe) have diverse morphological shapes, including pointsymmetric and multipolar structures. Many PNe also have complicated internal structures such as torus, lobes, knots, and ansae. A complete accounting of all the morphological structures through physical models is difficult. A first step toward such an understanding is to derive the true three-dimensional structure of the nebulae. In this paper, we show that a multipolar nebula with three pairs of lobes can explain many of such features, if orientation and sensitivity effects are taken into account. Using only six parameters − the inclination and position angles of each pair − we are able to simulate the observed images of 20 PNe with complex structures. We suggest that the multipolar structure is an intrinsic structure of PNe and the statistics of multipolar PNe has been severely underestimated in the past.

From near-infrared and molecular hydrogen imaging observations, we have discovered that the planetary nebula NGC 6072 has a multipolar structure with a prominent equatorial ring. We have modeled the object by a double bipolar system, each with an equatorial ring and a pair of bipolar lobes. The bipolar axes of the two systems are estimated to be separated by 47 •. The existence of such a double bipolar system suggests that the object has undergone separate fast outflow episodes separated by several thousand years.