Hubble Heritage | 2012 July 03
Hubble Basks in the Glare of a Cosmic Rocket
Herbig-Haro objects are nebulae observed near forming stars. Although they are found in a wide array of shapes, the basics stay the same: twin jets of heated gas shoot off in opposite directions away from a newborn star. These outflows stream through space, stretching out to scales so gargantuan that they dwarf our solar system more than a thousand times over.
When these energetic jets run into colder gas, the collision plays out like a traffic jam on the interstate. Gas within the shock front slows to a crawl, but more mass piles up as the jet continues to slam into the shock from behind. Temperatures skyrocket, and this curving, flared region glows brightly. These "bow shocks" are so named because they resemble the waves that form at the front of a boat.
In the case of the HH 110 jet, astronomers observe an unusual permutation on this basic model. Careful study has repeatedly failed to find the source star driving HH 110, which also lacks a counter-jet pointing in the opposite direction. But there may be good reason for this: perhaps the HH 110 outflow is itself generated by another jet.
Astronomers now believe that the nearby HH 270 jet grazes an immovable obstacle — a much denser, colder molecular cloud core — and caroms off at about a 60-degree angle. The jet goes dark and then reemerges, having reinvented itself as HH 110.
The ridges inside HH 110 show that these stellar fireworks are produced like the erratic outbursts from a Roman candle. As fast-moving blobs of gas catch up and collide with slower blobs downstream, new shock fronts arise along the jet's interior. Emission from hot, excited gas causes these inner boundaries to glow.
The exact way HH jets are launched is still a mystery, but the outline is known — at least in broad strokes. As a disk of leftover material rotates around a newborn star, friction within the spinning disk causes particles to slowly spiral inward. Upon reaching the disk's innermost rim, the infalling gas hops onto magnetic field lines connected to the star. Slow-moving gas can latch onto lines that lead to the star's poles, but gas particles with more angular momentum are banished for their impatience. These faster particles are exiled to interstellar space along magnetic field lines that at first point radially away from the star, and then slowly curve upwards into streams that flow perpendicular to the disk.
This stunning view of the HH 110 jet combines data from Hubble's Advanced Camera for Surveys and the Wide Field Camera 3.
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
NASA's Hubble Views a Cosmic Skyrocket
NASA | STScI | HubbleSite | 2012 July 03
Resembling a Fourth of July skyrocket, Herbig-Haro 110 is a geyser of hot gas from a newborn star that splashes up against and ricochets off the dense core of a cloud of molecular hydrogen. Although the plumes of gas look like whiffs of smoke, they are actually billions of times less dense than the smoke from a July 4 firework. This Hubble Space Telescope photo shows the integrated light from plumes, which are light-years across.
Herbig-Haro (HH) objects come in a wide array of shapes, but the basic configuration stays the same. Twin jets of heated gas, ejected in opposite directions away from a forming star, stream through interstellar space. Astronomers suspect that these outflows are fueled by gas accreting onto a young star surrounded by a disk of dust and gas. The disk is the "fuel tank," the star is the gravitational engine, and the jets are the exhaust.
When these energetic jets slam into colder gas, the collision plays out like a traffic jam on the interstate. Gas within the shock front slows to a crawl, but more gas continues to pile up as the jet keeps slamming into the shock from behind. Temperatures climb sharply, and this curving, flared region starts to glow. These "bow shocks" are so named because they resemble the waves that form at the front of a boat.
In the case of the single HH 110 jet, astronomers observe a spectacular and unusual permutation on this basic model. Careful study has repeatedly failed to find the source star driving HH 110, and there may be good reason for this: perhaps the HH 110 outflow is itself generated by another jet.
Astronomers now believe that the nearby HH 270 jet grazes an immovable obstacle — a much denser, colder cloud core — and gets diverted off at about a 60-degree angle. The jet goes dark and then reemerges, having reinvented itself as HH 110.
The jet shows that these energetic flows are like the erratic outbursts from a Roman candle. As fast-moving blobs of gas catch up and collide with slower blobs, new shocks arise along the jet's interior. The light emitted from excited gas in these hot blue ridges marks the boundaries of these interior collisions. By measuring the current velocity and positions of different blobs and hot ridges along the chain within the jet, astronomers can effectively "rewind" the outflow, extrapolating the blobs back to the moment when they were emitted. This technique can be used to gain insight into the source star's history of mass accretion.
A geyser of hot gas flowing from a star
ESA/HEIC Hubble Photo Release | 2012 July 03
The NASA/ESA Hubble Space Telescope has captured a new image of Herbig-Haro 110, a geyser of hot gas flowing from a newborn star.
Although Herbig–Haro (HH) objects come in a wide array of shapes, the basic configuration is usually the same. Twin jets of heated gas, ejected in opposite directions from a forming star, stream through interstellar space. These outflows are fueled by gas falling onto the young star, which is surrounded by a disc of dust and gas. If the disc is the fuel tank, the star is the gravitational engine, and the jets are the exhaust.
In Hubble’s image of HH 110, one such turbulent streamer of gas can clearly be seen streaking across the frame.
The intricate structures within HH 110 and other Herbig–Haro objects exist because the jets are not being blown through a pure vacuum. When the energetic and fast-moving Herbig–Haro jets slam into colder gas, they form shock fronts that look and behave much like the bow waves that form in front of a boat. These so-called bow shocks, which glow thanks to very high temperatures, are a distinctive feature of Herbig-Haro objects.
The structure of HH 110 and other objects like it acts like a ticker-tape, recording the activity of the star that is the origin of the jet. Erratic outbursts from the star happen at times when more matter is falling in, and these are recorded as brighter knots or blobs within the Herbig-Haro object, which move along the jet over the years. Although the jets are very fast-moving, they are also very large: the streamer of gas in this image is around half a light-year in length. This means that the motion appears quite slow from our vantage point, even when measured over years (see heic1113).
By measuring the current speed and positions of blobs within a Herbig-Haro object, astronomers can rewind time, projecting the motion of the knots backwards to the moment when they were emitted. This in turn tells the scientists about the environment directly around the forming star.
Fireworks Erupt From Newborn Star
Universe Today | Nancy Atkinson | 2012 July 03
Newborn star makes a cosmic bank shot
Discover Blogs | Bad Astronomy | 2012 July 03