It's hard to put into words just how striking this new observation of the
Orion Nebula
is -- but it's not only its striking beauty that has captivated astronomers.
Using the
HAWK-I infrared instrument
on the
ESO's Very Large Telescope (VLT)
located high in the Atacama Desert in Chile, this deepest ever look into the famous star-forming region 1,350 light-years away has revealed a previously hidden population of brown dwarfs and planetary mass objects. The discovery,
according to an ESO news release
, challenges some widely accepted theories as to how the nebula evolved.
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Brown dwarfs are too massive to be planets and yet too small to be classified as stars; they form a bridge between the largest gas giant planets and the smallest red dwarf stars while possessing characteristics of both. Some of the higher-mass brown dwarfs could sustain fusion in their cores early in their evolution, but for the most part, fusion didn't take hold. It is for this reason that brown dwarfs are often called "failed stars," though they could just as well be known as "overachieving planets."
Welcome to the Orion Nebula, as you've never seen it before.
ESO/H. Drass et al.
The Orion Nebula spans around 25 light-years across and, if you have clear skies, it can be seen without the aid of a telescope or binoculars in the constellation of Orion as a small fuzzy cloud. Its clarity therefore provides astronomers with a nearby laboratory in which they can see the active process of star birth.
But now that many more sub-stellar mass objects have been detected in the nebula, confusion as to how they got there has inspired new ideas as to how many smaller objects are being born within the Orion Nebula when compared with other nebulae that have a slower rate of star formation and yet generate larger stars.
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"Understanding how many low-mass objects are found in the Orion Nebula is very important to constrain current theories of star formation," said Amelia Bayo, of the Universidad de Valparaíso in Chile and the Max-Planck Institut für Astronomie, Königstuhl, in Germany. "We now realize that the way these very low-mass objects form depends on their environment." Bayo is co-author of a new study published in the Monthly Notices of the Royal Astronomical Society.
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The VLT has counted ten-times more sub-stellar objects than previously known, potentially transforming our view on the mechanics of star formation within different nebulae.
Though an exciting development, there could be many more planetary-mass objects in the Orion Nebula, but we'll need a more powerful observatory to look even deeper into the twisted knots of gas and dust. And it just so happens, only a 30 minute drive from the VLT, a monster telescope is planned.
This image shows some highlights from a spectacular new image of the Orion Nebula star-formation region by the VLT.
ESO/H. Drass et al.
Called the European Extremely Large Telescope (E-ELT), this 40 meter optical/near-infrared telescope will be the largest on the planet and is scheduled to begin operations in 2024. It's these sub-stellar objects, generating a faint infrared glow, that will be a tantalizing target.
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"Our result feels to me like a glimpse into a new era of planet and star formation science," said lead-author Holger Drass of the Ruhr-Universität Bochum in Germany and Pontificia Universidad Católica de Chile, Santiago, Chile. "The huge number of free-floating planets at our current observational limit is giving me hope that we will discover a wealth of smaller Earth-sized planets with the E-ELT."
Not only has this beautiful observation of the Orion Nebula given us a new appreciation for how many brown dwarfs are birthed in nebulae, it could be a prelude to the discovery of a huge number of free-floating planets that swarm in star-forming regions.
GALLERY: When Runaway Stars Shock Interstellar Space
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NASA/JPL-Caltech
At the American Astronomical Society meeting in Kissimmee, Fla.
, this week, astronomers using data from NASA's Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE) missions presented their findings of a special class of star and their associated "bow shocks."
Here are a few of the stunning examples of "runaway stars" and their impact on interstellar gases.
Image: As seen by Spitzer, the star Kappa Cassiopeiae (HD 2905) is generating a dazzling infrared bow shock. The star's stellar wind and magnetic field are hitting the thin interstellar gases, highlighting the star's direction of travel (toward the lower right of the image).
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NASA/JPL-Caltech
As a boat cruises through the ocean, water at the bow of the vessel will be pushed against water flowing in the opposite direction. The resulting wave is descriptively known as a "bow wave," which trails away from the boat as it continues on its way. Now imagine a star, powering through the interstellar medium. That star is itself pumping out stellar gases. In the direction the star is travelling, the stellar winds buffer against the interstellar gases and a huge bow shock -- not too dissimilar to our boat analogy -- is generated. Depending on the conditions in the interstellar medium and the speed at which the star is moving, these shocks can be detected from Earth -- the heated gases are spotted via their infrared signature.
This stunning Spitzer observation shows the striking detail that can be revealed in the bow shocks of some of the speediest stars. This particular example shows the star Zeta Ophiuchi (Zeta Oph) traveling at around 54,000 mph (24 kilometers
per second
) relative to its surroundings. Runaways are a special type of star that is alone and the nature of their bow shock can reveal some information about their origins.
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NASA/JPL-Caltech/UCLA
This observation is also of Zeta Oph but imaged by the WISE mission. The infrared signature as seen by WISE is more diffuse than the Spitzer view as cooler dust and gas is being detected by the space telescope's filters.
The size and shape of a particular star's bow shock also reveals some information about the star's mass and speed. Zeta Oph is around 20 times more massive than our sun, generating more powerful stellar winds and is traveling faster. Its bow shock will therefore be more dramatic than anything our sun can generate.
"Some stars get the boot when their companion star explodes in a supernova, and others can get kicked out of crowded star clusters," said William Chick from the University of Wyoming in Laramie, at the AAS meeting. "The gravitational boost increases a star's speed relative to other stars."
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NASA/JPL-Caltech/University of Wyoming
Interestingly, the researchers used archival data from both WISE and Spitzer to identify the presence of bow shocks throughout the galaxy, finding 200 candidate signals. Although some of the signals were in fact glowing star-formation nebulae, ground observatories confirmed that most were indeed caused by runaway stars.
"We are using the bow shocks to find massive and/or runaway stars," said Henry "Chip" Kobulnicky, also from the University of Wyoming. "The bow shocks are new laboratories for studying massive stars and answering questions about the fate and evolution of these stars."
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NASA/JPL-Caltech/University of Wyoming
Another group of researchers, who also presented their results this week, are going about the "bow shock hunt" in a different way.
"WISE and Spitzer have given us the best images of bow shocks so far," said Cintia Peri of the Argentine Institute of Radio Astronomy. "In many cases, bow shocks that looked very diffuse before, can now be resolved, and, moreover, we can see some new details of the structures."
Peri's team is seeking out the speedy stars first and then finding their associate bow shocks after.
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NASA/JPL-Caltech/University of Wyoming
The diffuse glow of a star's bow shock can also be seen in this Spitzer observation. Of all the runaway stars identified in this new study, all ranged in mass from 8 to 30 solar masses.
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NASA/ESA
Bow shocks haven't only been detected by WISE and Spitzer. WISE's predecessor, NASA's Infrared Astronomical Satellite (IRAS), scanned the whole sky in 1983 and identified the first glowing bow shocks emanating from runaway stars. Other missions, including the Hubble Space Telescope, have also spied the phenomenon, but not just from the speedy stars.
In this stunning observation by Hubble, a very young star called LL Ori was spied with a very pronounced bow shock. As young stars evolve furiously, they generate very powerful stellar winds that ram into the surrounding gases inside their star forming nebulae -- in this case inside the star factory in the heart of the Orion nebula. The result of the collision of supersonic gases powering through the nebula can also create bow shocks, sans runaway star.
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Source:
NASA/JPL-Caltech