Ian O'Neill, Author at Universe Today

March 6, 2008December 26, 2015 by Ian O'Neill

Origins of the Earth’s Atmospheric “Hiss” Energizing Van Allen Belt Particles Revealed

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Scientists working at the University of California, Los Angeles (UCLA) have identified the origin behind the upper atmospheric “hiss” that energizes the high-energy particles bouncing around inside Earth’s radioactive Van Allen Belts. This is significant, as this has been a very long wait for answers to the origin of this low-frequency radio wave emissionâ€¦ after 40 years of looking, we may now have an answerâ€¦

The Van Allen Belts surrounding Earth can be a terrifying place for spacecraft and astronauts. Occupying a volume 200 km above the surface and can extend as far as seven Earth radii (over 44,000 km). These volumes of highly energetic particles are trapped by the Earth’s magnetosphere, bouncing electrons and protons back and forth in their magnetic prison. The Van Allen Belts are variable and closely related to solar activity. As the solar wind hits the Earth’s magnetosphere, solar wind particles will fall into the polar cusp regions, entering the atmosphere and creating aurorae in Northern and Southern Polar regions (Aurora Borealis and Aurora Australis respectively). However, some particles are fed into the magnetosphere and become trapped between the onion skin-like layers of magnetic field lines and cannot escape.

This is how the Van Allen Belts are supplied, and the population of protons and electrons are expected to increase and become more energetic during solar storms. Although we know a lot about these regions, very little is known how the trapped electrons and protons are energized so much that they can penetrate lead up to 1 mm deep. This has obvious design implications for the thousands of satellites orbiting the Earth, and poses a serious health risk to astronauts spending long periods in space.

In new research published in Nature today, the UCLA research group believe they have found the origin of upper atmospheric “hiss”. The hiss has radio wave frequencies and has been observed since early missions into space in the 1960s. Thought to originate from magnetic interactions in the magnetosphere itself, or even from intense lightning storm emissions into the upper atmosphere, definitive proof for the source of this strange phenomenon was proving very elusive. Putting classical ideas to one side, Jacob Bortnik’s work focuses on a totally different form of electromagnetic wave called “chorus”. This wave was thought to have no connection with radio hiss, but Bortnik proves that chorus waves, travelling many thousands of kilometres, can evolve into the hiss which characterizes the Van Allen Belts.

“Here, we show that a different wave type, called chorus, can propagate into the plasmasphere from tens of thousands of kilometers away and evolve into hiss. Our new model naturally accounts for the observed frequency band of hiss, its incoherent nature, its day-night asymmetry in intensity, its association with solar activity and its spatial distribution. The connection between chorus and hiss is very interesting because chorus is instrumental in the formation of high-energy electrons outside the plasmasphere, while hiss depletes these electrons at lower equatorial altitudes.” â€“ Jacob Bortnik.

The UCLA group were actually not researching the atmospheric hiss, but were working on chorus waves â€“ that typically propagate outside the plasmasphere â€“ and realized they could evolve into the “hiss” responsible for particle energization in the Van Allen Belts.

This research has massive consequences for the prediction of space weather. The conditions of the space between the Sun and Earth is very important when predicting the onset of a solar storm, but the reaction of the Earth’s upper atmosphere is critical when understanding how potentially damaging particles are energized to such a large extent.

Source: Physorg.com

March 6, 2008April 26, 2016 by Ian O'Neill

Extreme Observations of the Aurora in a Land of Polar Bears and Frostbite – Images of Research in the Freezer

Solar-terrestrial physics observations are about to get even more exciting. The University Centre on Svalbard (UNIS) has completed the construction of a brand new observatory, The Kjell Henriksen Observatory (KHO), providing researchers with a shiny-new ringside seat to observe a dazzling atmospheric phenomena, the Aurora Borealis (a.k.a. the Northern Lights). It is probably one of the most extreme places on the planet, with temperatures dropping below minus 35 degree Celsius (-31F) and where humans are no longer at the top of the food chain, working on Svalbard can be challenging, but very rewarding. Witnessing the aurora erupt overhead is an awe inspiring sight, to observe and research this reaction between the solar wind and upper atmosphere is a chance in a lifetime. What’s more… I’ve been there…

Svalbard is a strange but magical place. Found high in the Arctic Circle, half-way between Norway and the North Pole, the archipelago attracts international attention for its untouched landscape and unique location. Famed as the magical destination for a series of novels (Philip Pullman’s “His Dark Materials” trilogy) and a blockbuster movie (“The Golden Compass“), the main island of Spitsbergen plays host to some of the most dramatic scenery on Earth. The panserbjÃ¸rne may not be armour-plated, but there are bears nonetheless, insuring humans take special precautions.

Although life can be tough up there – temperatures plummeting lower than minus 35 degrees Celsius; over four months of Arctic night; the constant need to carry a rifle when travelling beyond settlement limits – people live very comfortably, mainly working in coal mine towns, for the local tourism industry or studying biology, physics or technology in the worlds most northerly university called “UNIS”.

I had the amazing fortune to live there for five months, in the spring of 2002, as part of an exchange program between the University of Wales, Aberystwyth (UK) and the University of TromsÃ¸ (Norway). A group of five of us British guys set off to the Arctic to study the physics behind the Earth’s magnetosphere, the solar wind and the aurora.

Nothing can really prepare you for a trip to this extraordinary place. Trying to study in 24 hour Arctic night is hard (dragging yourself out of bed is a mission in itself!), but it makes for magnificent viewing of the Aurora Borealis on an inky-black backdrop of the night sky. Actually, it was the 24 hour day light that affected me the most. As the Sun slowly crept above the frozen horizon during March 2002, the darkness was sadly lost and the Northern Lights were never to be seen again.

I remember one night in particular, probably early February 2002. As part of our study for the “Upper Polar Atmosphere” course, we had to carry out some actual space research. The task was to track the effects of a Coronal Mass Ejection (CME) as it travelled from the Sun and impacted the Earth’s atmosphere. A seemingly massive task, but an exciting one – after all we were sitting below the lightshow very few people were able to experience, and we’d been set the goal of explaining how this amazing phenomenon actually works! That freezing February night, we had all been driven to the “Auroral Station” situated just outside Longyearbyen, the capital city (I say “city”, but only 2000 people live there) of Svalbard.

Resembling part-laboratory/part-shed, the Auroral Station (known as “Nordylysstatsjonen”) was a strange fixture to see standing in the snow. On entering we were faced with an observatory crammed with computers and cameras. This was the home of the “All Sky Camera” (ASC), a basic wide-angled camera looking up into the sky. On active nights, the ASC could take in a 360Â° view, from horizon to zenith, watching the auroral lightshow erupt overhead, watching the effects of solar particles impact the Earths upper atmosphere, and emitting light.

Unfortunately, the aurora didn’t show after several hours of waiting, looking through the bubble-shaped windows in the roof of the station.

In those long moments of waiting, it was very obvious that the days of observing the night sky in this little observation post were numbered. To the south-eastern skies, a creeping glow of street lights were of constant annoyance to the station scientists – even a town as tiny as Longyearbyen was putting out enough light pollution to interfere with the sensitive instruments. The outlook wasn’t good, the town was expanding and the pollution could only get worse.

Kjell Henriksen Observatory
The answer to this problem was obvious back then… the station would have to be moved, away from the excess light pollution. Exactly six years later, the solution has been realized.

On February 20th, 2008, the new state of the art observatory was completed. Situated 6 km (3.7 miles) up the fjord from the original location, the Kjell Henriksen Observatory is now proudly positioned 500 meters up a mountain overlooking a long valley called Adventdalen.

The new observatory was opened by Norway’s Minister for Research and Higher Education, Tora Aasland, announcing:

“The International Polar Year 2007-2008 is a huge international research effort of great importance to the northern region, as well as to global challenges. When the new observatory was planned, the goal was to have it ready for the Polar Year. I am very pleased that this goal was reached” – Tora Aasland

The new installation houses an impressive suite of instruments. In all over 15 optical and non-optical instruments are based here, operated by a range of international collaborators, observing mid- to upper-atmospheric phenomena. Even some of the most advanced all-sky cameras are now up and running during this “auroral season”.

Although the Northern Lights did not put on a show for the grand opening, and snow drizzled on the event, I hope the new observatory will be as successful as its predecessor and help to entice many more students (like myself, six years ago) into a research career focused on the Sun and its intrinsic relationship with the Earth.

For full details on the opening of the Kjell Henriksen Observatory, visit the UNIS news pages.

Source: UNIS, The Kjell Henriksen Observatory

March 6, 2008December 26, 2015 by Ian O'Neill

Observing the Atmospheres of Venus and Mars Leak into Space (Video)

It turns out that Venus and Mars aren’t actually that different after all. Although Mars has very little atmosphere to speak of and Venus has a stifling, thick, poisonous one, they have one thing in common: the Sun. The solar wind constantly batters the Solar System’s planets, stripping their atmospheres into space. Is it possible that Mars may once have had a thick atmosphere like Venus’, but has long since leaked away?

The twin ESA spacecraft, Venus Express and Mars Express, have very similar instruments on board and are currently orbiting the two planets. Mars Express arrived on December 25th 2003 and Venus Express arrived on April 11th 2006. Venus Express was intended as a “copy” of the older Mars Express design, but some upgrades were required. Primarily, as Venus is two times closer to the Sun, Venus Express needed better protection from solar radiation. There will also be an increase in ionizing high-energy particles hitting the orbiter, so this had to be taken into account.

Apart from a few minor upgrades, the twin Express missions are able to carry out the same observations on both planets, providing ESA scientists with a unique opportunity to compare results of both spacecraft. In fact, for the first time ever, researchers are able to carry out comparative planetology of two planets with two orbiting spacecraft as they are carrying similar instrumentation.

One such instrument is the Analyser of Space Plasmas and Energetic Atoms (ASPERA) that can be found on both spacecraft. ASPERA has detected atmospheric particles leaking into space as the solar wind hits the planetary atmospheres. Both Mars and Venus, despite their difference in orbits and size, exhibit similar patterns of particle loss. As the planets have no uniform magnetic field surrounding the atmosphere, atmospheric particles are easily swept away. In the case of the Earth, our atmosphere is protected by a strong magnetosphere blanketing us from the ferocious solar wind.

Ultimately ESA scientists hope to analyse the rate of particle loss from Mars and Venus so a better picture of planetary evolution can be arrived at. It is possible that the solar wind may be responsible for the very thin Martian atmosphere. Mars is a tiny planet (only half the size of Earth); whereas Venus is often considered to be Earth’s “sister” as it is approximately the same size. Perhaps the low Mars gravity allowed a higher rate of atmospheric loss than Venus.

What ever the conclusion, mission scientists have a lot of work to do. The results will not only help us understand the development of Mars and Venus, it will also aid our understanding about how the Earth is evolving and may give us some clues to the future.

Video: The strong interaction of the solar wind with the atmosphere of Venus (ESA)

Source: ESA

March 3, 2008December 26, 2015 by Ian O'Neill

HiRISE Captures Stunning Images of Mars Avalanches in Action

A Mars Avalanche, taken by NASAs HiRISE instrument on the Mars Reconnaisance Orbiter (Credit: NASA/HiRISE)

Magnificent images of avalanches of ice and rock in the northern polar regions of Mars have been captured by NASA Mars Reconnaissance Orbiter’s (MRO) High Resolution Imaging Science Experiment (HiRISE). These images are not of landslides that have happened in the past, they are actual Mars avalanches happening at the moment of observation. This rare event will be of tremendous value to Mars scientists currently analysing the effects of seasons on the landscape and will provide information on the geological activity of the planet…

This event occurred along a scarp (a distinct cliff, with a steep runoff) around the North Polar Region where surface ice can be found in large quantities. The HiRISE instrument was being used to assess seasonal changes around the North Pole when four areas of activity were seen along the scarp. HiRISE was witness to something more familiar on Earth than on Mars: avalanches.

This particular scarp is a high cliff over 700 m (2300 ft) tall and slopes at over 60 degrees. A mixture of ice, rock and dust can be seen, frozen in time, as it is plummeting down the slope, ejecting a plume of dust as the debris begins to settle on the gentle slope at the bottom of the cliff. The ejected cloud is approximately 180 meters across and extends about 190 meters beyond the base of the cliff. It is worth noting that the clouds are large 3D structures reaching into the Martian atmosphere and not 2D patterns on the surface (shadows from the plume can be seen to the lower left of the clouds of dust).

The Martian landscape does not change very much over millions of years. Unlike the Earth, Mars does not have a thick, eroding atmosphere blasting away at the surface features. The lack of water also reduces these erosion effects. Mars also has very little geological activity as core reactions are thought to have slowed or even stopped – there is therefore very little tectonic movement, no major earthquakes and no evidence for present volcanic activity.

So what caused these avalanches? HiRISE scientists have some ideas:

Disappearance of carbon dioxide frost, dislodging rocks.
Expansion and contraction of ice due to seasonal temperature differences.
Small Mars-quakes.
A nearby meteorite impact.
Vibrations from other avalanches causing other avalanches along the scarp

It seems most likely that the trigger may be down to seasonal changes. As the North Polar RegionÂ heats up (progressing toward summer), solid carbon dioxide (“dry ice”) may beÂ subliming, weakening rocks around theÂ edge of the cliff. The same could be said for the thermal expansion and contraction of water iceÂ as the seasonalÂ air temperature becomes warmer or cooler.

Whatever the cause, we are very lucky to have captured this event,Â the science collected from these observations will be critical to understanding how the Martian landscape can change very rapidly. The HiRISE instrument continues to return the most magnificently detailed images of the Red Planets surface, these observations of Mars avalanches will certainly go into the Mars Reconnaissance Orbiter’s Hall of Fame…

Source: HiRISE Project Site

March 3, 2008April 26, 2016 by Ian O'Neill

Tracking Debris from US Spy Satellite USA 193; Delays to Rocket Launch

The shoot down of US spy satellite USA 193 was condemned by some quarters of the international community. However, the fact remains, this was a resounding success for the US military. Observers of the operation to destroy the potentially dangerous satellite likened it to “trying to fire a missile through the eye of a needle”. After all, the dead satellite was orbiting at a height of about 250 km, and the satellite-killing missile was fired from a boat; assuring impact with an object the size of a small bus was never going to be easy. But the mission was a success and the satellite disintegrated into bits (no bigger than a football). Now the task of tracking the debris is under way, and the fallout from last months fireworks are impacting the scheduled launch of other space missions…

According to CelesTrak, there are 52 catalogued bits of USA 193 orbiting the Earth. The pieces range in altitude from 167 km (at the closest approach) to over 2,600 km (at apogee – the highest point of orbit) and they are being tracked with great accuracy (pictured above).

The 5,000 pound (2,300 kg) satellite apparently disintegrated into many small pieces of debris, each no bigger than the volume of a football (equivalent to a circle with a diameter of 20 cm). Anything smaller than 10 cm cannot be tracked with any degree of accuracy, so an analysis by CelesTrak (pictured left) shows the upper and lower bounds of debris that can be tracked and how long they are likely to stay in orbit.

As a rule, larger pieces of debris will remain in orbit for longer, whilst the smaller objects will have less momentum to stay above the Earths atmosphere. As can be seen, most of the debris can be expected to burn up through atmospheric re-entry within 30 days, but there is a massive difference in the lifetime of the remaining 10 cm debris when compared with the 20 cm debris. The remaining 5% of large chunks of satellite are projected to stay in orbit for 50 days longer than their smaller cousins.

Tracking these bits of debris is an arduous task, but the monitoring continues. The destruction of USA 193 has influenced the scheduled launch of rockets since February 20th, and disruption is likely to continue should these larger pieces of debris pass through spacecraft launch windows. The launch of a US National Reconnaissance Office NROL-28 reconnaissance satellite last Friday from Vandenberg Air Force Base in California, has been postponed for two weeks until the USA 193 debris poses no threat of collision.

Universe Today coverage of the demise of satellite USA 193:

Original Source: CelesTrak

March 3, 2008December 26, 2015 by Ian O'Neill

UK Urged to Focus on Satellite Technology, not Manned Exploration of Space

The UK is the only G8 country (the eight richest countries in the world) without a manned space program. 20 years ago, Prime Minister Margaret Thatcher put pay to any hope for a British astronaut by opting out of plans citing it as “too expensive” for the island nation. However, the UK government signalled last month they were considering a review of this space exploration policy, receiving a mixed reaction. A prominent satellite manufacturer has come forward with a suggestion that the UK may after all be better suited to constructing a space exploration “infrastructure” and leaving manned exploration to the ESA and NASA…

In 1986, the UK was effectively ruled out of manned expeditions into space. Plans outlined by the European Space Agency (ESA) at the time were considered too expensive for the nation to pursue, so the UK concentrated on its civil and defence space capabilities through robotic explorers rather than participating in any national or international collaboration.

As of 2007, after two decades of research and development, Britain spends over Â£200 million ($400 million) a year on space initiatives, putting some of the world’s most advanced technology into space. UK companies such as SSTL, Qinetiq, Logica and Astrium are leading the world in certain space technology areas as a result. Many in the industry (especially the satellite manufacturing sector) would agree that the lack on participation in a manned space program has provided growth in robotic exploration sectors.

This may be the case, but there is pressure for the UK to catch up with the other seven nations of the G8 and begin sending British astronauts into space rather than depending on NASA and the ESA. British-born astronauts have been into space, such as Piers Sellers (pictured above), Michael Foale (dual nationality – Britain and USA) and Nicholas Patrick; Helen Sharman was the first Briton in space in 1991. All British astronauts were either naturalized American or involved with other space programs,Â little investment was made by the UK government in any manned mission.

Many academics would disagree with the UK’s past unwillingness to “get involved” in a manned program. As the worlds nations become more and more space-worthy, many believe the UK is being left behind and the dependence on NASA and ESA will become problematic as time goes on. There would be economic and educational value in starting a UK manned space program too. Looking back on the stimulation that the Apollo program had on the US in the 1960’s, the nation saw a surge of interest in the sciences and engineering subjects. This educated an entire generation of college and university students who have formed the foundations of the hugely influential space program that exists today.

“The UK needs to take early steps for a future role in a human exploration programme. It can stimulate education and excite the young to get involved in science and technology.” – Professor Frank Close, Oxford University and Chairman of the UK Space Exploration Working Group (in an interview with The Independent Online).

But the idea of a UK manned space program may push the nation beyond its means according to David Williams, head of Avanti, a satellite communications company. Williams believes that the UK, after many years of space innovation and robotic exploration of space and the planets, is ideally placed to dominate the world’s communication ability with deep space missions.

“If mankind is going to exploit the resources of the solar system, you are going to have to travel over very long distances and you are going to have to communicate over very long distances and you will need a network of data-relay satellites. The UK has a big advantage. We have the opportunity to control the space internet, which is going to be this network of data-relay satellites.” – David Williams.

Following this logic, as space exploration is an international effort, letting big space agencies such as ones controlled by the USA, Russia and Europe pursue manned exploration, the UK has an important role to play to insure advanced communication technology keep the international manned space efforts in touch with Earth.

Either way, this is an exciting time for UK space efforts. Although recently buffeted by funding shortages, there appears to be some positive movement toward greater involvement in international collaboration and investment in satellite technologies.

Source: The Guardian Online, The Independent Online

March 1, 2008December 26, 2015 by Ian O'Neill

Mars Gullies Produced by Dry Granular Debris and Not by Recent Water Flow

The High Resolution Imaging Science Experiment (HiRISE) on board NASA’s Mars Reconnaissance Orbiter (MRO) observed what appeared to be fresh gullies formed by a rapid release of water on the Martian surface in 2006. However, new computer models simulating the creation of gullies on the surface of Mars suggest that they are in fact created by the flow of dry debris (i.e. landslides) and not by the flow of water. A blow for the microbial life hunters and a huge blow for mission planners looking for easy sources of water for manned missions…

The MRO isn’t the only orbiter to view apparent gullies forged by spurts of water. The Mars Orbiter Camera (MOC) onboard NASA’s Mars Global Surveyor (MGS) also made news in 2006 when scanning the cratered regions of Terra Sirenum and Centauri Montes. Images taken several years apart revealed some changes in the most recent pictures, highlighting what looked like outflow channels from surges of liquid water (pictured below). What made this especially exciting was that this was possible evidence for the existence of liquid water flowing on Mars within the past few years (albeit very quickly).

New work by scientists at the University of Arizona appears to conflict with these observations. In an attempt to demonstrate the characteristics of water flowing in Martian conditions, Associate Professor Jon D. Pelletier (Geophysics) and colleagues used topological data from the HiRISE instrument (the most advanced imaging system currently orbiting Mars) and modelled the flow of water down a slope. What the simulation showed was a surprise; the researchers went into the project thinking they were going to prove that the gullies were formed by water. Instead, they had shown that the shapes and characteristics of the observed gullies most resembled that of the modelled gullies shaped by dry debris tumbling down a slope.

“The dry granular case was the winner. I was surprised. I started off thinking we were going to prove it’s liquid water.” – Jon D. Pelletier

Looking at the comparison between the two cases (water and dry debris flow) and the HiRISE observations, it is very easy to see the striking resemblance between dry debris flow and what is actually observed. The water simulation appears to be more diffuse, lacking the characteristic “fingers” reaching down the slope.

On hearing the news in 2006 that there was a possibility of liquid water flowing on the Martian surface, biologists hoped that a new tool had been found to pinpoint where sub-surface deposits of liquid water may be stored. This will have provided future missions with a location to hunt for life in the most likely place, near fresh gullies, near a source of water. Unfortunately it seems that these gullies are in fact shaped by small landslides, not by surges of water from a sub-surface reservoir.

Research to be published in the March issue of Geology, entitled: “Recent bright gully deposits on Mars: wet or dry flow?“.

Source: University of Arizona News

February 29, 2008December 26, 2015 by Ian O'Neill

First Experiment Starts in ISS Columbus Module Testing Plant Growth

The brand new ESA Columbus Module installed on the International Space Station (ISS) by the STS-122 crew last week is beginning a first run of biological experiments. This first experiment tests the reaction of root growth in different gravitational states. Of particular interest is how the roots of seeds develop in space when compared to terrestrial conditions. This has obvious applications for growing plants in space, underpinning agricultural science in some of the most extreme and challenging environments man will experience.

Today saw the first ever experiment on the ESA Columbus Module on board the ISS. European astronaut LÃ©opold Eyharts activated the Waving and Coiling of Arabidopsis Roots at Different g-levels (WAICO) experiment, comparing two types of arabidopsis seed (one wild and one genetically modified) in gravity conditions from zero to one Earth gravity (or 1G). The arabidopsis seed is derived from the arabidopsis thaliana plant which copes very well in restricted space and thrives in hostile surroundings.

The WAICO experiment will last for 10 to 15 days and the sprouted seeds will be returned by the STS-123 Space Shuttle mission due for launch on March 11th so the results can be analysed. Throughout the experiment, using the brand new “Biolab” equipment (pictured), the advanced telemetry of the Columbus Module will relay real-time video of seed development to ESA scientists in Germany.

The development of the root growth will be scrutinized; especially the amount of “waving” and “coiling” that occurs as a reaction to different gravity conditions. These experiments will also help terrestrial farming methods, giving farmers the opportunity to optimize plant growing conditions.

Source: ESA

February 29, 2008December 26, 2015 by Ian O'Neill

Shuttle Endeavour to Launch on March 11th; View the STS-123 Interactive Mission Timeline

We haven’t had time to catch our breath after STS-122 touched down on February 20th, only nine days ago, and yet the next launch date to the International Space Station (ISS) has been announced today. The date? March 11th -Â only 11 days from now. This time NASA has put together a nice little interactive gadget so you can see the 17 day mission from day to day…

STS-122 was a highly successful round trip to the ISS. The Space Shuttle Atlantis crew delivered ESA’s Columbus science module without a hitch on February 11th. The only small problem arose when one of the crew members suffered an undisclosed minor medical problem, postponing installation for a day, but the crew adapted and performed excellently.

With Atlantis’ engines still warm, Endeavour is being prepared for launch on March 11th. This time the mission is to install a part of the Japanese laboratory complex called “Kibo”. In addition, a new Canadian robotics system will be attached to complement the existing robotic arm servicing the Harmony module.

STS-123 will be a complex mission for crew members Dominic Gorie (Commander), Gregory H. Johnson (Pilot), Rick Linnehan (Mission Specialist), Robert L. Behnken (Mission Specialist), Mike Foreman (Mission Specialist), Garret Reisman (Mission Specialist) and Japanese astronaut Takao Doi. Five spacewalks (EVAs) will need to be carried out to continue the expansion of the station.

The Associate Administrator for Space Operations, Bill Gerstenmaier, stated that there were very few issues with the pre-launch stages and said that Space Shuttle Endeavour is ready to blast off.

View the interactive guide of the STS-123 mission to the ISS.

Source: NASA

February 29, 2008December 26, 2015 by Ian O'Neill

Massive Stars Need Their Smaller Siblings To Grow

So how do rare massive stars grow 10 to 150 times the mass of our Sun? It turns out that a standard star-forming nebula is way too cold for big stars to form. So how can these clouds of gas and dust be prepared so massive stars can develop? Answer: Let small stars do the hard work and heat that nebula up…

This is the ultimate stellar crÃ¨che. Star-forming nebulae are vast regions of space filled with gas and dust. Proto-stars need a lot of hydrogen to form and begin fusion reactions in their young cores. The bigger the nebula, the bigger the star… or so you’d think.

The problem with these young nebulae is that they are cold; in fact they are very cold. Typical interstellar clouds of hydrogen have temperatures very close to absolute zero (the lowest temperature possible) due to the lack of heat in the far-off reaches of the cosmos. Cold clouds will fragment very easily, breaking up and forming smaller clouds of hydrogen. Eventually they will collapse to form stars, but these stars will be very small due to the lack of fuel in the nebula fragment. If this is the case, how are massive stars – the ones responsible for producing heavy elements including anything heavier than helium – formed at all? Surely all clouds of dust and gas are cold, and therefore fragment, only producing small stars?

From research publishedÂ in Nature this weekby Christopher F. McKee (a professor from UC Berkeley) and Mark R. Krumholz (Hubble postdoctoral fellow at Princeton), there is a possible solution to this problem. Perhaps young stars provide a heating source to warm up the surrounding nebula,Â preventing the surroundingÂ gas from fragmenting, allowing itÂ to collapse into progressively bigger stars.

Starting at temperatures only 10-20 degrees above absolute zero, clouds heated by young stars may increase in temperatures three-fold. However, researchers realize that a massive star-forming cloud needs to be several hundred degrees warmer than absolute zero to prevent the whole cloud from fragmenting, they also understand that the “zone of heating” forÂ each small star is limited in less dense clouds. This situation changes when the star-forming cloud is dense. The zone of influence each small star has will encompass the whole nebula. This collaborative heating effect by the small stars prevents fragmentation and allows larger volumes of gas to collapse, forming massive stars.

“It’s only the formation of these low-mass stars that heats up the cloud enough to cut off the fragmentation. It is as if the cold molecular cloud starts on the process of making low-mass stars but then, because of heating, that fragmentation is stopped and the rest of the gas goes into one large star.” – Christopher F. McKee.

A warmer cloud is a bigger cloud, providing more fuel, allowing massive stars to form. It is the ultimate stellar nursery; massive stars can only form once their smaller (and older) siblings warm up the cosmic nest for them to thrive.

View theÂ stunningÂ simulation of a massive star forming in a warm cloud (24Mb, .mpg)

Source: UC Berkley News