# HH 30

HH-30 (also V1213 Tauri) is an edge-on protoplanetary disk that is surrounded by jets and a disk wind. HH-30 is located in the dark cloud LDN 1551 in the Taurus Molecular Cloud. The HH-30 disk is the prototype of an edge-on disk, due to its early discovery with Hubble.

## Discovery

HH 30 was published by George Herbig in 1974 in the "Draft Catalog of Herbig–Haro Objects" and notes: "HH-30 (4h 28m 44s) is a small, almost stellar spot 2' south of XZ and HL Tau. There is a fainter nebulosity immediately northeast. The small fuzzy spot of very similar appearance at 35" in 250° from HL Tau is not a HH Object, but a star having Hα in emission." In 1996 it became clear that the object is an edge-on protoplanetary disk with jets.

## The central star

The star is hidden behind the dust of the disk. The spectral type was measured around M0 with the Keck Observatory, corresponding to a temperature of around 3700 Kelvin. Disk rotation constrained the star mass to 0.45 M$_☉$. One study suggest that the central object is a binary star, due to the jet wiggling. A follow-up study found that the jet-producing primary has a mass of 0.31 ±0.04 M$_☉$ and that the secondary has a mass of 0.14 ±0.03 M$_☉$. Both objects should be separated by 18.0 ±0.6 astronomical units (AU).

## Protoplanetary disk

Observations with Hubble WFPC2 in 1996 discovered the disk, which has a radius of 250 AU. The disk is seen as a bi-reflection nebula and the disk blocks the light of the star. The northern part of the reflection nebula decreased in brightness by 0.5 mag between two observations, while the southern part increased in brightness by 0.5 mag. The disk around the star is a class II disk, meaning it contains both gas and dust particles. Observations with the Plateau de Bure interferometer detected the carbon monoxide (CO) emission and measured the rotation of the disk. Observations with the Atacama Large Millimeter Array (ALMA) showed the mid-plane of the disk in $^{13}$CO and also measured its rotation. A study with JWST and archived Hubble and ALMA data was published in 2024. This showed inefficient dust settling in the disk. Dust settling means that larger dust grains settle to the mid-plane of the disk. The observation also showed that the disk contains spiral-like and tail-like structure. The disk has a very high inclination of at least 84°.

### Jets

The jets were discovered in 1983 from CCD images at Calar Alto Observatory. A proper motion survey in 1990 showed a speed of around 170 km/s of the jets. This study also detected H-alpha, ionized nitrogen and sulfur in the jet. Early observations with Hubble showed that the knots of the jet have a speed of 100 to 300 km/s. JWST NIRCam and MIRI observations showed the previously observed jet and a bi-conical outflow. The jet is bright in the MIRI F1280W filter, likely tracing ionized neon emission. One knot was seen moving with around 121 km/s. The jet is seen with NIRSpec in ionized iron with a tight semi-opening angle of 1.4°±0.9°.

### Disk wind

A CO outflow was first resolved in 2006, and in 2024 the outflow was detected with ALMA in $^{12}$CO. The researchers found three distinct shells in the outflow and measured an outflow mass of (1.83 ±0.19)×10$^{‑4}$ M$_☉$. This outflow is expanding with a speed of around 4–6 km/s and possibly rotates with a speed of ≤0.5 km/s. These shells can be explained by a magnetocentrifugal disk winds (MHD wind). Another study using NIRSpec and ALMA, found that the outflow is nestled within each other. The jet is seen with a tight semi-opening angle of around 1.4°. The disk wind is seen with a wider semi-opening angle, with the molecular hydrogen (H$_2$) emission having a semi-opening angle of around 14°. But this emission is also nestled within cold carbon monoxide (CO) emission from ALMA.