Teardrops in the sky

Young Stellar Object 177-341
Credit: ESO/M. L. Aru et al.

Is it a comet? Is it a spaceship? The object in this Picture of the Week might be a bit hard to recognise at first. It is in fact a young star — but why does it have such an unusual shape?

Young stars are surrounded by a disc of gas and dust: the building materials for planets. When other very bright and massive stars are present nearby, their light heats the young star’s disc, stripping away part of its material. The teardrop-shaped object in this image, 177-341 W, is in the Orion Nebula. The stars eroding away the disc of 177-341 W are out of the frame past the upper-right corner; when their radiation clashes with the material around the young star, it creates the bright, bow-like structure seen here in yellow. The tail extending from the star towards the lower-left corner is material being dragged away from 177-341 W by the stars out of the field of view. This type of objects — ionised protoplanetary discs — are known as “proplyds”.

This observation is presented in a new paper led by Mari-Liis Aru (ESO) and taken with the Multi Unit Spectroscopic Explorer (MUSE) instrument on ESO’s Very Large Telescope (VLT) in Chile. The colours shown in this image map different elements like hydrogen, nitrogen, sulfur and oxygen. But this is just a small fraction of all the data gathered by MUSE, which actually takes thousands of images at different colours or wavelengths simultaneously. This allows astronomers to study the physical properties of protoplanetary discs in great detail, including the amount of mass that they lose. This new paper presents MUSE observations of many other proplyds in Orion, part of a project led by Carlo F. Manara (ESO) which will help astronomers understand how stars and planetary systems form in these stellar nurseries.

Links

• The young stellar object 177-341 W as seen with Hubble and VLT
• Video: A MUSE view of the 177-341 W young stellar object

Source: ESO/Images

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Hubble Sees the Force Awakening in a Newborn Star

 

Herbig-Haro Jet HH 24

Acknowledgment: NASA, ESA, the Hubble Heritage (STScI/AURA)/Hubble-Europe (ESA) Collaboration, D. Padgett (GSFC), T. Megeath (University of Toledo), and B. Reipurth (University of Hawaii).  Credit: NASA and ESA. Release Images

This is an artist's concept of the fireworks that accompany the birth of a star. The young stellar object is encircled by a pancake-shaped disk of dust and gas left over from the collapse of the nebula that formed the star. Gas falls onto the newly forming star and is heated to the point that some of it escapes along the star's spin axis. Intertwined by magnetic fields, the bipolar jets blast into space at over 100,000 miles per hour. As seen from far away, they resemble a double-bladed lightsaber from the Star Wars film series. Credit: NASA, ESA, and A. Feild (STScI)

Just about anything is possible in our remarkable universe, and it often competes with the imaginings of science fiction writers and filmmakers. Hubble's latest contribution is a striking photo of what looks like a double-bladed lightsaber straight out of the Star Wars films. In the center of the image, partially obscured by a dark, Jedi-like cloak of dust, a newborn star shoots twin jets out into space as a sort of birth announcement to the universe. Gas from a surrounding disk rains down onto the dust-obscured protostar and engorges it. The material is superheated and shoots outward from the star in opposite directions along an uncluttered escape route — the star's rotation axis. Much more energetic than a science fiction lightsaber, these narrow energetic beams are blasting across space at over 100,000 miles per hour. This celestial lightsaber does not lie in a galaxy far, far away but rather inside our home galaxy, the Milky Way.

Just in time for the release of the movie "Star Wars Episode VII: The Force Awakens," NASA's Hubble Space Telescope has photographed what looks like a cosmic, double-bladed lightsaber.

In the center of the image, partially obscured by a dark, Jedi-like cloak of dust, a newborn star shoots twin jets out into space as a sort of birth announcement to the universe.

"Science fiction has been an inspiration to generations of scientists and engineers, and the film series Star Wars is no exception," said John Grunsfeld, astronaut and associate administrator for NASA's Science Mission Directorate. “There is no stronger case for the motivational power of real science than the discoveries that come from the Hubble Space Telescope as it unravels the mysteries of the universe."

This celestial lightsaber does not lie in a galaxy far, far away, but rather inside our home galaxy, the Milky Way. It's inside a turbulent birthing ground for new stars known as the Orion B molecular cloud complex, located 1,350 light-years away.

When stars form within giant clouds of cool molecular hydrogen, some of the surrounding material collapses under gravity to form a rotating, flattened disk encircling the newborn star.

Though planets will later congeal in the disk, at this early stage the protostar is feeding on the disk with a Jabba-like appetite. Gas from the disk rains down onto the protostar and engorges it. Superheated material spills away and is shot outward from the star in opposite directions along an uncluttered escape route — the star's rotation axis.

Shock fronts develop along the jets and heat the surrounding gas to thousands of degrees Fahrenheit. The jets collide with the surrounding gas and dust and clear vast spaces, like a stream of water plowing into a hill of sand. The shock fronts form tangled, knotted clumps of nebulosity and are collectively known as Herbig-Haro (HH) objects. The prominent HH object shown in this image is HH 24.

Just to the right of the cloaked star, a couple of bright points are young stars peeking through and showing off their own faint lightsabers — including one that has bored a tunnel through the cloud towards the upper-right side of the picture.

Overall, just a handful of HH jets have been spotted in this region in visible light, and about the same number in the infrared. Hubble's observations for this image were performed in infrared light, which enabled the telescope to peer through the gas and dust cocooning the newly forming stars and capture a clear view of the HH objects.

These young stellar jets are ideal targets for NASA's upcoming James Webb Space Telescope, which will have even greater infrared wavelength vision to see deeper into the dust surrounding newly forming stars.

For additional information, contact:

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu

Mathias Jäger
ESA/Hubble, Garching, Germany
011-49-176-6239-7500
mjaeger@partner.eso.org

Deborah Padgett
NASA Goddard Space Flight Center, Greenbelt, Maryland
deborah.l.padgett@nasa.gov

Bo Reipurth (available only after Jan. 8, 2016)
University of Hawaii, Hilo, Hawaii
reipurth@ifa.hawaii.edu

Tom Megeath
University of Toledo, Toledo, Ohio
megeath@physics.utoledo.edu

Source: HubbleSite

Outbursts from a newborn star

HH 212

Credit: ESO/M. McCaughrean

A pair of jets protrude outwards in near-perfect symmetry in this image of Herbig-Haro object (HH) 212, taken by ESO’s already decommissioned Infrared Spectrometer And Array Camera (ISAAC).

The object lies in the constellation of Orion (The Hunter) in a dense molecular star-forming region, not far from the famous Horsehead Nebula. In regions like this, clouds of dust and gas collapse under the force of gravity, spinning faster and faster and becoming hotter and hotter until a young star ignites at the cloud’s centre. Any leftover material swirling around the newborn protostar comes together to form an accretion disc that will, under the right circumstances, eventually evolve to form the base material for the creation of planets, asteroids and comets.

Although this process is still not fully understood, it is common that a protostar and its accretion disc, as seen here edge-on, are the cause of the jets in this image. The star at the centre of HH 212 is indeed a very young star, at only a few thousand years old. Its jets are remarkably symmetric, with several knots appearing at relatively stable intervals. This stability suggests that the jet pulses vary quite regularly, and over a short timescale — maybe even as short as 30 years! Further out from the centre, large bow shocks spread out into interstellar space, caused by ejected gas colliding with dust and gas at speeds of several hundred kilometres per second.

Source: ESO

A young star takes centre stage

LDN 981/Lynds 981

Credit: ESA/Hubble, NASA, Karl Stapelfeldt (GSFC), B. Stecklum and A. Choudhary (Thüringer Landessternwarte Tautenburg, Germany)

With its helical appearance resembling a snail’s shell, this reflection nebula seems to spiral out from a luminous central star in this new NASA/ESA Hubble Space Telescope image.

The star in the centre, known as V1331 Cyg and located in the dark cloud LDN 981 — or, more commonly, Lynds 981 — had previously been defined as a T Tauri star. A T Tauri is a young star — or Young Stellar Object — that is starting to contract to become a main sequence star similar to the Sun.

What makes V1331Cyg special is the fact that we look almost exactly at one of its poles. Usually, the view of a young star is obscured by the dust from the circumstellar disc and the envelope that surround it. However, with V1331Cyg we are actually looking in the exact direction of a jet driven by the star that is clearing the dust and giving us this magnificent view.

This view provides an almost undisturbed view of the star and its immediate surroundings allowing astronomers to study it in greater detail and look for features that might suggest the formation of a very
low-mass object in the outer circumstellar disc.

Source: ESA/Hubble - Space Telescope

Twinkle, Twinkle New-Born Star

Newborn stars in the Rho Ophiuchi star-forming region as seen in the infrared by the Spitzer Space Telescope. The youngest stars, the reddest ones in the image, are surrounded by disks of dust and gas from which planetary systems are possibly forming. New observations of the light variability from these young stars confirm that probably all of them have clumpy dust disks. NASA/Spitzer

Stars are born in dense, cool clouds of molecular gas and dust. When the local density is high enough, the matter can gravitationally collapse to form a new star, a so-called young stellar object (YSO). In its early phases, a thick envelope dominates the infrared emission from the YSO, hiding what is going on within, but eventually the envelope flattens out into a warm circumstellar accretion disk. The disk emits more infrared than does the young star, and that excess radiation can be used to distinguish young stars from more mature stars whose disks and envelopes have disappeared. In recent years it has become possible to investigate these envelopes and disks in more detail, and astronomers have been building on these studies to address how planetary systems develop.

It turns out that an accretion disk does not extend all the way in to the central star. Instead, a gap is produced between the star and disk because the dust grains closer in are destroyed by the starlight or blown away by stellar winds. Disks can contain clumps or irregular structures which orbit around with the disk. 

When a YSO happens to be aligned such that we observe its light through its disk, these structures make it appear to twinkle, or more precisely, to vary in intensity. Clumps at a distance of about one astronomical unit (the average distance of the Earth from the Sun) produce flickering over times of years as they rotate, while those in the disk ten times closer in result in variations over timescales of days.

CfA astronomers Hans Gunther, Katja Poppenhaeger, Scott Wolk, and Joe Hora and their colleagues used the infrared camera, IRAC, on the Spitzer Space Telescope to monitor the variability of light from 882 previously identified YSOs in a nearby region of star formation, Lynds 1688, over a period of 1.6 years.

They report finding that seventy of them vary; ten have roughly periodic variations although none of these variations has the regularity or characteristics to suggest transit exoplanet transits. Combined with other information about these YSOs, the new results confirm that probably all YSOs are variable at infrared wavelengths to some degree, and moreover that the younger, more deeply embedded stars often have longer and larger intensity variations, consistent with the current disk evolution picture.

Reference(s):

"YSOVAR: Mid-Infrared Variability in the Star-Forming Region Lynds 1688," H. M. Gunther, A. M. Cody, K. R. Covey, L. A. Hillenbrand, P. Plavchan, K. Poppenhaeger, L. M. Rebull, J. R. Stauffer, S. J. Wolk, L. Allen, A. Bayo, R. A. Gutermuth, J. L. Hora, H. Y. A. Meng, M. Morales-Calder´on, J. R. Parks, and Inseok Song, ApJ 148, 122, 2014.

Source: Smithsonian Astrophysical Observatory

Light and dark

SSTC2D J033038.2+303212

Credit: ESA/Hubble & NASA

This new NASA/ESA Hubble Space Telescope image shows a variety of intriguing cosmic phenomena.

Surrounded by bright stars, towards the upper middle of the frame we see a small young stellar object (YSO) known as SSTC2D J033038.2+303212. Located in the constellation of Perseus, this star is in the early stages of its life and is still forming into a fully grown star. In this view from Hubble’s Advanced Camera for Surveys (ACS) it appears to have a murky chimney of material emanating outwards and downwards, framed by bright bursts of gas flowing from the star itself. This fledgling star is actually surrounded by a bright disc of material swirling around it as it forms — a disc that we see edge-on from our perspective.

However, this small bright speck is dwarfed by its cosmic neighbour towards the bottom of the frame, a clump of bright, wispy gas swirling around as it appears to spew dark material out into space. The bright cloud is a reflection nebula known as [B77] 63, a cloud of interstellar gas that is reflecting light from the stars embedded within it. There are actually a number of bright stars within [B77] 63, most notably the emission-line star LkHA 326, and its very near neighbour LZK 18.

These stars are lighting up the surrounding gas and sculpting it into the wispy shape seen in this image. However, the most dramatic part of the image seems to be a dark stream of smoke piling outwards from [B77] 63 and its stars — a dark nebula called Dobashi 4173. Dark nebulae are incredibly dense clouds of pitch-dark material that obscure the patches of sky behind them, seemingly creating great rips and eerily empty chunks of sky. The stars speckled on top of this extreme blackness actually lie between us and Dobashi 4173.

Link

• Hubble’s Advanced Camera for Surveys

Source: ESA/Hubble - Space Telescope