Herbig–Haro object
Bright patches of nebulosity associated with newborn stars, formed by high-speed jets colliding with interstellar gas and dust.
Herbig–Haro (HH) objects are bright patches of nebulosity associated with newborn stars. They are formed when narrow jets of partially ionised gas ejected by stars collide with nearby clouds of gas and dust at several hundred kilometers per second. Herbig–Haro objects are commonly found in star-forming regions, and several are often seen around a single star, aligned with its rotational axis. Most of them lie within about one parsec (3.26 light-years) of the source, although some have been observed several parsecs away. HH objects are transient phenomena that last around a few tens of thousands of years. They can change visibly over timescales of a few years as they move rapidly away from their parent star into the gas clouds of interstellar space (the interstellar medium or ISM). Hubble Space Telescope observations have revealed the complex evolution of HH objects over the period of a few years, as parts of the nebula fade while others brighten as they collide with the clumpy material of the interstellar medium.
- discovered_by
- Sherburne Wesley Burnham (late 19th century)
- named_after
- George Herbig and Guillermo Haro
- type
- Emission nebula associated with star formation
- typical_velocity
- Several hundred kilometers per second
- typical_temperature
- 9,000–12,000 K
- typical_density
- A few thousand to a few tens of thousands of particles per cm³
- lifespan
- Around a few tens of thousands of years
Lore & Background
First observed in the late 19th century by Sherburne Wesley Burnham, Herbig–Haro objects were recognised as a distinct type of emission nebula in the 1940s. The first astronomers to study them in detail were George Herbig and Guillermo Haro, after whom they have been named. Herbig and Haro were working independently on studies of star formation when they first analysed the objects, and recognised that they were a by-product of the star formation process. Although HH objects are visible-wavelength phenomena, many remain invisible at these wavelengths due to dust and gas, and can only be detected at infrared wavelengths. Such objects, when observed in near-infrared, are called molecular hydrogen emission-line objects (MHOs). The Soviet astronomer Viktor Ambartsumian gave the objects their name (Herbig–Haro objects, normally shortened to HH objects), and based on their occurrence near young stars (a few hundred thousand years old), suggested they might represent an early stage in the formation of T Tauri stars.
Reader's Guide
Herbig–Haro objects are formed when narrow jets of partially ionised gas ejected by newborn stars collide with nearby gas and dust at high speeds. They are transient, lasting tens of thousands of years, and can change visibly over a few years. Many HH objects are invisible at visible wavelengths due to dust and gas, and are detected in infrared; these are called molecular hydrogen emission-line objects (MHOs).
Did You Know?
- The first HH object was observed in the late 19th century by Sherburne Wesley Burnham.
- HH objects are named after George Herbig and Guillermo Haro, who studied them independently in the 1940s.
- HH objects can change visibly over timescales of a few years as they move rapidly away from their parent star.
- Many HH objects are invisible at visible wavelengths and can only be detected in infrared.
More in Stars And Stellar Phenomena 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record