Peptides are one of the smallest biomolecules and are one of life’s critical building blocks. New research shows that they could form on the surfaces of icy grains in space. This discovery lends credence to the idea that meteoroids, asteroids, or comets could have given life on Earth a kick start by crashing into the planet and delivering biological building blocks.Continue reading “One of Life’s Building Blocks can Form in Space”
Star formation is a topic astronomers are still trying to fully understand. We know, for example, that stars don’t form individually, but rather are born within vast interstellar molecular clouds. These stellar nurseries contain gas dense enough for gravity to trigger the formation of stars. In spiral galaxies, these molecular clouds are most commonly found within spiral arms, which is why stars are most often born in spiral arms.Continue reading “Astronomers Find a Giant Cavity in Space, Hollowed out by an Ancient Supernova”
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How do stars form?
We know they form from massive structures called molecular clouds, which themselves form from the Interstellar Medium (ISM). But how and why do certain types of stars form? Why, in some situations, does a star like our Sun form, versus a red dwarf or a blue giant?
That’s one of the central questions in astronomy. It’s also a very complex one.Continue reading “This is a Simulation of the Interstellar Medium Flowing Like Smoke Throughout the Milky Way”
A new study shows how massive young stars create the kind of organic molecules that are necessary for life.
A team of researchers used an airborne observatory to examine the inner regions around two massive young stars. Along with water, they found things like ammonia and methane. These molecules are swirling around in a disk of material that surrounds the young stars.
That material is the same stuff that planets form from, and the study presents some new insights into how the stuff of life becomes incorporated into planets.Continue reading “We’re Made of Starstuff. Especially From Extremely Massive Stars”
The Corona Australis is a constellation in the southern hemisphere. It’s name literally means “southern crown.” One of its features is the Corona Australis molecular cloud, home to a star-forming region containing young stars and proto-stars. It’s one of the closest star-forming regions to us, only about 430 light years away.
The ESA has given us a new composite image of the cloud with data from the Herschel Space Observatory and the Planck Space Observatory.Continue reading “The Corona Australis Molecular Cloud. Normally this Looks Like a Dark Blob in the Sky. But in Infrared, it Looks Like This.”
What a stunning view of this dark region of space! This image, by astrophotographer Callum Hayton shows LDN 673, a molecular cloud complex that lies in the constellation Aquila. This region is massive — around 67 trillion kilometers (42 trillion miles across), and it is between 300-600 light years from Earth. Observers in the northern hemisphere can find this region in the summer skies near the bright star Altair and the Summer Triangle.
Because the cloud lies on the galactic plane, the dark dust is back-lit by millions of stars in the Milky Way galaxy. This dusty cloud likely contains enough raw material to form hundreds of thousands of stars. Hayton explained on Flickr how the dust gets “eroded” away by stellar formation:
“When some of these clouds reach a certain mass they begin to collapse and fragment creating protostars,” Hayton wrote. “As the temperature and pressure at the centre of the protostar rises, sometimes it becomes so great that nuclear fusion begins and a star is born. In this image you can see where at least two young stars have eroded the dust around them and are now above the clouds casting light down on to the dust below.”
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It didn’t happen overnight. By studying the properties of giant molecular clouds in the Whirlpool Galaxy for several years with the millimeter telescopes of IRAM, the Institut de Radioastronomie Millimétrique, astronomers have been given a whole, new look at star formation. Encompassing 1,500 maps of molecular clouds, this new research has found these building blocks of future suns to be encased in a sort of molecular hydrogen mist. This ethereal mixture appears to be far denser than speculated and is found throughout the galactic disc. What’s more, it would appear the pressure created by the molecular fog is a critical factor in determining whether or not stars are able to form within the clouds.
Stars form in the molecular clouds housed within all galaxies. These formations are vast areas of hydrogen molecules with masses which total from a thousand to several million times that of the Sun. When an area of the cloud folds under the weight of its own gravity, it collapses. Pressure and temperature rise and nuclear fusion begins. A star is born.
This exciting new research is changing the way astronomers think about starbirth regions. Study leader Eva Schinnerer (Max Planck Institute for Astronomy) explains: “Over the past four years, we have created the most complete map yet of giant molecular clouds in another spiral galaxy similar to our own Milky Way, reconstructing the amounts of hydrogen molecules and correlating them with the presence of new or older stars. The picture that is emerging is quite different from what astronomers thought these clouds should be like.” The survey, known as PAWS, targeted the Whirlpool galaxy, also known as M51, at a distance of about 23 million light-years in the constellation Canes Venatici – the Hunting Dogs.
Annie Hughes, a post-doctoral researcher at MPIA involved in the study, says: “We used to think of giant molecular clouds as solitary objects, drifting within the surrounding interstellar medium of rarified gas in isolated splendor; the main repository of a galaxy’s supply of hydrogen molecules. But our study shows that 50% of the hydrogen is outside the clouds, in a diffuse, disk-shaped hydrogen fog permeating the galaxy!”
Not only does the enveloping gas play a critical part in star formation, but galaxy structure does as well. One galactic feature in particular is key – spiral arm structure. They sweep slowly around the core area like hands on a clock and are more populated with stars than the remainder of the galactic disk. Sharon Meidt, another MPIA post-doctoral researcher involved in the study, says: “These clouds are definitely not isolated. On the contrary, interactions between clouds, fog, and overall galactic structure appear to hold the key to whether or not a cloud will form new stars. When the molecular fog moves relative to the galaxy’s spiral arms, the pressure it exerts on any clouds within is reduced, in line with a physical law known as Bernoulli’s principle. Clouds feeling this reduced pressure are unlikely to form new stars. According to the press release, Bernoulli’s law is also thought to be responsible for part of the well-known shower-curtain effect: shower curtains blowing inward when one takes a hot shower, another display of reduced pressure.
Jerome Pety of the Institut de Radioastronomie Millimétrique (IRAM), which operates the telescopes used for the new observations, says: “It’s good to see our telescopes live up to their full potential. A study that needed such extensive observation time, and required both an interferometer to discern vital details and our 30 m antenna to put those details into a larger context, would not have been possible at any other observatory.”
Schinnerer concludes: “So far, the Whirlpool galaxy is one example which we have studied in depth. Next, we need to check that what we have found also applies to other galaxies. For our next steps, we hope to profit from both the extension NOEMA of the compound telescope on the Plateau de Bure and from the newly opened compound telescope ALMA in Chile, which will allow in-depth studies of more distant spiral galaxies.”
Original Story Source: Max Planck Institute for Astronomy News Release.
It’s beautiful…. But it’s cold. By utilizing the submillimetre-wavelength of light, the 12 meter APEX telescope has imaged the frigid, dusty clouds of star formation in the Carina Nebula. Here, some 7500 light-years away, unrestrained stellar creation produces some of the most massive stars known to our galaxy… a picturesque petri dish in which we can monitor the interaction between the neophyte suns and their spawning molecular clouds.
By examining the region in submillimetre light through the eyes of the LABOCA camera on the Atacama Pathfinder Experiment (APEX) telescope on the plateau of Chajnantor in the Chilean Andes, a team of astronomers led by Thomas Preibisch (Universitäts–Sternwarte München, Ludwig-Maximilians-Universität, Germany), in close cooperation with Karl Menten and Frederic Schuller (Max-Planck-Institut für Radioastronomie, Bonn, Germany), have been able to pick apart the faint heat signature of cosmic dust grains. These tiny particles are cold – about minus 250 degrees C – and can only be detected at these extreme, long wavelengths. The APEX LABOCA observations are shown here in orange tones, combined with a visible light image from the Curtis Schmidt telescope at the Cerro Tololo Interamerican Observatory.
This amalgamate image reveals the Carina nebula in all its glory. Here we see stars with mass exceeding 25,000 sun-like stars embedded in dust clouds with six times more mass. The yellow star in the upper left of the image – Eta Carinae – is 100 times the mass of the Sun and the most luminous star known. It is estimated that within the next million years or so, it will go supernova, taking its neighbors with it. But for all the tension in this region, only a small part of the gas in the Carina Nebula is dense enough to trigger more star formation. What’s the cause? The reason may be the massive stars themselves…
With an average life expectancy of just a few million years, high-mass stars have a huge impact on their environment. While initially forming, their intense stellar winds and radiation sculpt the gaseous regions surrounding them and may sufficiently compress the gas enough to trigger star birth. As their time closes, they become unstable – shedding off material until the time of supernova. When this intense release of energy impacts the molecular gas clouds, it will tear them apart at short range, but may trigger star-formation at the periphery – where the shock wave has a lesser impact. The supernovae could also spawn short-lived radioactive atoms which could become incorporated into the collapsing clouds that could eventually produce a planet-forming solar nebula.
Then things will really heat up!
Original Story Source: ESO News Release.
Star formation is an incredible process, but also notoriously difficult to trace. The reason is that the main constituent of stars, hydrogen, looks about the same well before a gravitational collapse begins, as it does in the dense clouds where star formation happens. Sure, the temperature changes and the hydrogen glows in a different part of the spectrum, but it’s still hydrogen. It’s everywhere!
So when astronomers want to search for denser regions of gas, they often turn to other atoms and molecules that can only form or be stimulated to emit under these relatively dense conditions. Common examples of this include carbon monoxide and hydrogen cyanide. However, a study published in 2005, led by David Meier at the University of Illinois at Urbana-Champaign, studied inner regions of the nearby face-on spiral by tracing eight molecules and determined that the full extent of the dense regions is not well mapped by these two common molecules. In particular, cyanoacetylene, an organic molecule with a chemical formula of HC3N, was demonstrated to correlate with the most active star forming regions, promising astronomers a peek into the heart of star forming regions and prompting a follow-up study.
The new study was conducted from the Very Large Array in late 2005. Specifically, it studied the emissions due to 5-4, 10-9, and 16-15 transitions which each correspond to different levels of heating and excitation. The dense regions uncovered by this study were consistent with the ones reported in 2005. One, discovered by the previous survey from another tracer molecule, was not found by this most recent study, but the new study also discovered a previously unnoticed giant molecular cloud (GMC) through the presence of HC3N.
Another technique that can be applied is examining the ratios of various levels of excitation. From this, astronomers can determine the temperature and density necessary to produce such emission. This can be performed with any type of gas, but using additional species of molecules provides independent checks on this value. For the area with the strongest emission, the team reported that the gas appeared to be a cool 40 K (-387°F) with a density of 1-10 thousand molecules per cubic centimeter. This is relatively dense for the interstellar medium, but for comparison, the air we breathe has approximately 1025 molecules per cubic centimeter. These findings are consistent with those reported from carbon monoxide.
The team also examined several of the star forming cores independently. By comparing the varying strengths of tracer molecules, the team was able to report that one GMC was well progressed in making stars while another was less evolved, likely still containing hot cores which had not yet ignited fusion. In the former, the HC3N is weaker than in the other cores explored, which the team attributes to the destruction of the molecules or dispersal of the cloud as fusion begins in the newly formed stars.
While using HC3N as a tracer is a relatively new approach (these studies of IC 342 are the first conduced in another galaxy), the results of this study have demonstrated that it can trace various features in dense clouds in similar fashions to other molecules.
Anyone who has looked at stars in the night sky (especially ones low on the horizon) has undoubtedly seen the common effect of twinkling. This effect is caused by turbulence in the atmosphere as small over densities cause the path of the light to bend ever so slightly. Often, vivid color shifts occur since the effects are wavelength dependent. All of this happens in the short distance between the edge of the atmosphere and our eyes. Yet often times, giant molecular clouds lie between our detectors and a star. Could these clouds of gas and dust cause a twinkling effect as well?
In theory, there’s no reason they shouldn’t. As the giant molecular clouds intercepting the incoming starlight move and distort, so too should the path of the light. The difference is that, due to the extremely low density and extremely large size, the timescales over which this distortion would take place would be far longer. Should it be discovered, it would provide astronomers another method by which to discover previously hidden gas.
Doing this is precisely the goals of a team of astronomers working from the Paris University and Sharif University in Iran. To get and understanding of what to expect, the team first simulated the effect, taking into account the properties of the cloud (distribution, velocity, etc…) as well as refraction and reflection. They estimated that, for a star in the Large Magellanic Cloud with light passing through typical galactic H2 gas, this would produce twinkles with changes taking around 24 minutes.
Yet there are many other effects which can produce modulations on the same timescale such as variable stars. Additional constraints would be necessary to claim that a change would be due to a twinkling effect and not a product of the star itself. As stated before, the effect is different for different wavelengths which would produce a “variation of the characteristic time scale … between the red side of the optical spectrum and the blue side.”
With expectations in hand, the team began searching for this effect in areas of the sky in which they knew especially high densities of gas to exist. Thus, they pointed their telescopes towards dense nebulae known as Bok globules like Barnard 68 (pictured above). Observations were taken using the 3.6 meter ESO NTT-SOFI telescope since it had the capabilities to also take infrared images and better explore the potential effects on the red side of the spectrum.
From their observations over two nights, the team discovered one instance in which the modulation of brightness in the different wavelengths followed the predicted effects. However, they note that from a single observation of their effects, it does not conclusively demonstrate the principle. The team also observed stars in the direction of the Small Magellanic Cloud to attempt to observe this twinkling effect in that direction due to previously undetected clouds along the line of sight. In this attempt, they were unsuccessful. Further similar observations along these lines in the future could help to constrain the amount of cold gas within the galaxy.