Herschel space telescope in Europe has imaged one of the most popular subjects in the sky – the Horsehead Nebula – and its environs.
Horsehead Nebula is a distinctively shaped molecular gas cloud sited some 1,300 light-years from Earth in the Constellation Orion.
It is in a region of space undergoing active star formation – something Herschel has been most keen to study.
The Hubble space observatory has also returned to the Horsehead scene, to celebrate 23 years in orbit.
Together, these two great facilities give scientists a much broader insight into what is taking place in this familiar patch of the heavens.
“You need images at all scales and at all wavelengths in astronomy in order to understand the big picture and the small detail,” said Prof. Matt Griffin, the principal investigator on Herschel’s SPIRE instrument.
“In this new Herschel view, the Horsehead looks like a little feature – a pimple. In reality, of course, it is a very large entity in its own right, but in this great sweep of a picture from Herschel you can see that the nebula is set within an even larger, molecular-cloud complex where there is a huge amount of material and a great range of conditions,” the Cardiff University, UK, researcher said.
To provide a sense of scale, the Horsehead Nebula, also known in the catalogues as “Barnard 33”, is about five light-years “tall”.
Hubble telescope sees the Horsehead in near-infrared light. Herschel, on the other hand, goes to much longer wavelengths. This allows it to see the glow coming directly from cold gas and dust – the material that will eventually collapse under gravity to form the next generation of stars.
Horsehead Nebula is a distinctively shaped molecular gas cloud sited some 1,300 light-years from Earth in the Constellation Orion
Scientists are particularly keen to understand the mechanisms that drive the production of the biggest stars – objects much more massive than our own Sun that form relatively fast, burn bright but brief lives, and interact strongly with their environment, influencing the next round of star formation.
The Orion Molecular Cloud Complex is one of the best and nearest regions in space to study this activity.
Prof. Matt Griffin explained: “You can see all the things we look for in Herschel images – the filaments, the bubbles; the wispy material, the reddish material that hasn’t yet actually started to form stars.
“You can also see nebulosity where material has been lit up from inside by stars; and features like the Horsehead Nebula where that star formation has yet to really get going.”
Hubble telescope’s new view was acquired by its Wide Field Camera-3 instrument, which was installed by astronauts on the last shuttle servicing mission in 2009.
The image was taken to celebrate its 23rd birthday in orbit. It was launched on April 24, 1990.
The much shorter wavelengths at which Hubble works means it can produce finer, sharper detail than Herschel.
It illustrates particularly well the way the ultraviolet glare and stellar winds from nearby stars are sculpting the dusty stellar nursery.
Hubble hopefully has quite a few years of operations left in it. Herschel does not.
Scientists are expecting to lose the telescope any day now.
The superfluid helium it uses to cool its instruments and their detectors is all but gone. When the supply runs completely dry, Herschel will warm from its ultra-low functioning temperature and go blind.
A scholarly paper describing Herschel’s investigation of the Orion Molecular Cloud Complex has been published in the journal Astrophysical Journal Letters.
In a new study, Hubble astronomers have observed deeper into space than ever before.
In doing so, they have identified six new galaxies of stars that formed just a few hundred million years after the Big Bang itself.
The study also updates a distance estimate for a seventh galaxy, placing it further back in time than any object previously identified.
Called UDFj-39546284, this is seen when the cosmos was less than 3% of its current age.
The new Hubble telescope investigation was led by Richard Ellis from the California Institute of Technology (Caltech) and colleagues at Edinburgh University, Jim Dunlop and Ross McLure.
Its significance is that it gives us the clearest insight into how some of the earliest years of cosmic history unfolded.
The data supports the notion that the first galaxies assembled their constituent stars in a smooth fashion – not in some sudden burst.
“Of course, the most distant object is interesting, but it’s the census – the seven objects – that gives us the first indication of the population of objects in the heart of this… era,” said Prof. Richard Ellis.
“If you compare the number of galaxies that we see to the abundance of objects once the Universe had expanded a little bit, we describe a very smooth decline in the number of objects as we go back into cosmic history,” he told reporters.
The new results stem from a project called UDF12 and centre on a tiny patch of sky in the Constellation Fornax (The Furnace).
This is the location where Hubble has repeatedly stared since 2003, trying to build up a picture of objects whose separation from us is so great that their light arrives in dribs and drabs.
Richard Ellis’s and colleagues’ work adds more than 100 hours of observations to this extraordinary Ultra Deep Field imagery – one of Hubble’s greatest accomplishments.
The light being seen from the remotest objects in the UDF would have started out as short wavelength (ultraviolet) emission that was then subsequently stretched to longer (infrared) wavelengths by the expansion of the Universe. And because it has taken so long for this light to reach us, the observations are effectively looking back in time.
This is difficult work, however. By the time the “redshifted” light lands on Hubble’s powerful Wide Field Camera 3 instrument, it has been stretched to the very edge of what is detectable by this equipment.
Looking back in time with the Hubble Space Telescope
Nonetheless, the team believes the data is robust enough to certify the six new galaxies and the one re-classification.
The objects lie in a range that covers redshifts 8.2-11.9 – the technical way of describing a period in time that runs from about 600 million years to 380 million years after the Big Bang (current cosmology suggests the Big Bang occurred some 13.77 billion years ago).
The most distant object, UDFj-39546284, was first announced by Garth Illingworth and Rychard Bouwens in a Nature paper in 2011. They gave it a redshift of 10 (480 million years after the Big Bang).
But the improved and extended dataset from Prof. Richard Ellis’s group strongly suggests this galaxy really lies at an even greater distance. Either that or it has properties in its light emission that hitherto have never been noted in a closer object.
Scientists are very keen to probe these colossal separations in time and distance because they will learn how the early Universe grew its structures, and that in turn will help them explain why the cosmos looks the way it does now.
In particular, they want to see more evidence for the very first populations of stars. These hot giants would have grown out of the cold neutral gas that pervaded the young cosmos.
These behemoths would have burnt brilliant but brief lives, producing the very first heavy elements.
They would also have “fried” the neutral gas around them – ripping electrons off atoms – to produce the diffuse intergalactic plasma we still detect between nearby stars today.
John Grunsfeld, NASA’s associate administrator for science and the astronaut known as the “Hubble repair man” because of the number of servicing missions he flew to the telescope, commented on the latest research: “These are baby pictures of the Universe.”
“These images are giving us the tantalizing view of what happened in the very earliest stages of the Universe. This is the time when the Universe was filled with hydrogen and starts to make stars and galaxies that make the chemical elements that we are primarily made out of – the oxygen we breathe, the iron in our blood, the calcium in our bones.”
Going even deeper in time is going to be extremely difficult with Hubble. This will likely have to wait for its successor, the James Webb Space Telescope (JWST), due for launch in 2018.
JWST will have a bigger mirror and more capability in the infrared regions where the light from the very first objects is expected to be found.
What Hubble can do, however, is broaden its search, conducting deep field observations in other places on the sky. This will provide more reliable statistics on early populations, giving astronomers reassurance that the Fornax UDF does not represent some sort of cosmic quirk.
Scholarly papers describing the Ellis group’s work are being published in Astrophysical Journal Letters.
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