We analyse eight epochs of Hubble Space Telescope Hα+[N II] imaging of η Carinae's outer ejecta. Proper motions of nearly 800 knots reveal that the detected ejecta are divided into three apparent age groups, dating to around 1250 A.D., to around 1550 A.D., and to during or shortly before the Great Eruption of the 1840s. Ejecta from these groups reside in different locations and provide a firm constraint that η Car experienced multiple major eruptions prior to the nineteenth century. The 1250 and 1550 events did not share the same axisymmetry as the Homunculus; the 1250 event was particularly asymmetric, even one-sided. In addition, the ejecta in the S ridge, which have been associated with the Great Eruption, appear to predate the ejection of the Homunculus by several decades. We detect essentially ballistic expansion across multiple epochs. We find no evidence for large-scale deceleration of the observed knots that could power the soft X-ray shell by ploughing into surrounding material, suggesting that the observed X-rays arise instead from fast, rarefied ejecta from the 1840s overtaking the older dense knots. Early deceleration and subsequent coasting cannot explain the origin of the older outer ejecta -significant episodic mass loss prior to the nineteenth century is required. The time-scale and geometry of the past eruptions provide important constraints for any theoretical physical mechanisms driving η Car's behaviour. Non-repeating mechanisms such as the merger of a close binary in a triple system would require additional complexities to explain the observations.

HH 900 is a peculiar protostellar outflow emerging from a small, tadpole-shaped globule in the Carina nebula. Previous Hα imaging with HST /ACS showed an ionized outflow with a wide opening angle that is distinct from the highly collimated structures typically seen in protostellar jets. We present new narrowband near-IR [Fe ii] images taken with the Wide Field Camera 3 on the Hubble Space Telescope that reveal a remarkably different structure than Hα. In contrast to the unusual broad Hα outflow, the [Fe ii] emission traces a symmetric, collimated bipolar jet with the morphology and kinematics that are more typical of protostellar jets. In addition, new Gemini adaptive optics images reveal near-IR H 2 emission coincident with the Hα emission, but not the [Fe ii]. Spectra of these three components trace three separate and distinct velocity components: (1) H 2 from the slow, entrained molecular gas, (2) Hα from the ionized skin of the accelerating outflow sheath, and (3) [Fe ii] from the fast, dense, and collimated protostellar jet itself. Together, these data require a driving source inside the dark globule that remains undetected behind a large column density of material. In contrast, Hα and H 2 emission trace the broad outflow of material entrained by the jet, which is irradiated outside the globule. As it get dissociated and ionized, it remains visible for only a short time after it is dragged into the H ii region.

We present proper motion measurements of 37 jets and HH objects in the Carina Nebula measured in two epochs of H α images obtained ∼10 yr apart with Hubble Space Telescope/Advanced Camera for Surveys (ACS). Transverse velocities in all but one jet are faster than 25 km s −1 , confirming that the jet-like H α features identified in the first epoch images trace outflowing gas. Proper motions constrain the location of the jet-driving source and provide kinematic confirmation of the intermediate-mass protostars that we identify for 20/37 jets. Jet velocities do not correlate with the estimated protostar mass and embedded driving sources do not have slower jets. Instead, transverse velocities (median ∼75 km s −1 ) are similar to those in jets from low-mass stars. Assuming a constant velocity since launch, we compute jet dynamical ages (median ∼10 4 yr). If continuous emission from inner jets traces the duration of the most recent accretion bursts, then these episodes are sustained longer (median ∼700 yr) than the typical decay time of an FU Orionis outburst. These jets can carry appreciable momentum that may be injected into the surrounding environment. The resulting outflow force, dP/dt, lies between that measured in low-and high-mass sources, despite the very different observational tracers used. Smooth scaling of the outflow force argues for a common physical process underlying outflows from protostars of all masses. This latest kinematic result adds to a growing body of evidence that intermediate-mass star formation proceeds like a scaled-up version of the formation of low-mass stars.

We present the first results from our survey of the star-forming complex W3, combining V RI photometry with multiobject spectroscopy to identify and characterize the high-mass stellar population across the region. With 79 new spectral classifications, we bring the total number of spectroscopicallyconfirmed O-and B-type stars in W3 to 105. We find that the high-mass slope of the mass function in W3 is consistent with a Salpeter IMF, and that the extinction toward the region is best characterized by an R V of approximately 3.6. B-type stars are found to be more widely dispersed across the W3 giant molecular cloud (GMC) than previously realized: they are not confined to the high-density layer (HDL) created by the expansion of the neighboring W4 H II region into the GMC. This broader B-type population suggests that star formation in W3 began spontaneously up to 8-10 Myr ago, although at a lower level than the more recent star formation episodes in the HDL. In addition, we describe a method of optimizing sky subtraction for fiber spectra in regions of strong and spatially-variable nebular emission.

We report the discovery and orbital solutions for two new OB binaries in the Cygnus OB2 Association, MT311 (B2V + B3V) and MT605 (B0.5V + B2.5:V). We also identify the system MT429 as a probable triple system consisting of a tight eclipsing 2.97 day B3V+B6V pair and a B0V at a projected separation of 138 AU. We further provide the first spectroscopic orbital solutions to the eclipsing, double-lined, O-star binary MT696 (O9.5V + B1:V), the double-lined, early B binary MT720 (B0-1V + B1-2V), and the double-lined, O-star binary MT771 (O7V + O9V). These systems exhibit orbital periods between 1.5 days and 12.3 days, with the majority having P <6 days. The two new binary discoveries and six spectroscopic solutions bring the total number of known massive binaries in the central region of the Cygnus OB2 Association to 20, with all but two having full orbital solutions.