Posted on by Fraser Cain

Audio: Into the Submillimeter

Artist illustration of the Atacama Large Millimeter Array currently under construction. Image credit: ESO. Click to enlarge.
Listen to the interview: Get Ready for Deep Impact (4.8 MB)

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Fraser Cain: Can you give me some background on the submillimeter spectrum? Where does that fit?

Paul Ho: The submillimeter, formally, is at a wavelength of 1 millimeter and shorter. So 1 millimeter wavelength in frequency corresponds to about 300 gigahertz or 3×10^14 hertz. So, it is a very short wavelength. From that down to a wavelength of about 300 microns, or a third of a millimeter, is what we call the submillimeter range. It is sort of what we call the end of the atmospheric window as far as the radio is concerned, because shorter, about a third of a millimeter they sky becomes essentially opaque due to the atmosphere.

Fraser: So, these are radio waves, like what you’d listen to on the radio, but much shorter – nothing I could ever pick up on my FM radio. Why are they good for viewing the Universe where it’s cold?

Ho: Any object that we know of, or see, typically is radiating a spread of energy characterizing the materials that we’re talking about, so we call this a spectrum. And this energy spectrum typically has a peak wavelength – or the wavelength at which the bulk of the energy is radiated. That characteristic wavelength depends on the temperature of the object. So, the hotter the object, the shorter the wavelength comes out at, and the cooler the object, the longer the wavelength comes out at. For the Sun, which has a temperature of 7,000 degrees, you’d have a peak wavelength which comes out in the optical, which is of course why our eyes are tuned to the optical, because we live near the Sun. But as the material cools, the wavelength of that radiation gets longer and longer, and when you get down to a characteristic temperature of say 100 degrees above Absolute Zero, that peak wavelength comes out somewhare in the far infrared or submillimeter. So, a wavelength on the order of 100 microns, or a little bit longer than that, which puts it into the submillimeter range.

Fraser: And if I were able to swap out my eyes, and replace them with a set of submillimeter eyes, what would I be able to see if I looked up into the sky?

Ho: Of course, the sky would continue to be quite cool, but you’d begin to pick up a lot of things that are rather cold that you would not see in the optical world. Things like materials that are swirling around a star which are cool, on the order of 100 Kelvin; pockets of molecular gas where stars are forming – they would be colder than 100 K. Or in the very distant, early Universe when galaxies are first assembled, this material is also very cold, which you would not be able to see in the optical world, that you might be able to see in the submillimeter.

Fraser: What instruments are you using, either here or in space?

Ho: There are ground and space instruments. 20 years ago, people began to work in the submillimeter, and there were a few telescopes that were beginning to operate in this wavelength. In Hawaii, on Mauna Kea, there are two: one called the James Clerk Maxwell Telescope, which has a diameter of about 15 metres, and also the Caltech Submillimeter Observatory, which has a diameter of about 10 metres. We have built an interferometer, which is a series of telescopes which are coordinated to operate as a single instrument on top of Mauna Kea. So 8 6-metre class telescopes which are linked together and can be moved apart or moved closer together to a maximum baseline of, or separation, of half a kilometre. So this instrument is simulating a very large telescope, on the size of half a kilometre at its maximum, and therefore achieving a very high angle of resolution compared to existing single element telescopes.

Fraser: It’s much easier to combine the light from radio telescopes, so I guess that’s why you’re able to do that?

Ho: Well, the interferometer technique has been used in radio for quite some time now, so we have perfected this technique fairly well. Of course, in the infrared and optical, people are also beginning to work in this way, working on interferometers. Basically, combining the radiation, you have to keep track of the phase front of the radiation coming in. Normally I explain this as if you had a very large mirror and broke it so you just reserve a few pieces of the mirror, and then you want to reconstruct the information from those few pieces of mirror, there are a few things you need to do. First, you have to be able to keep the mirror pieces aligned, relative to each other, just like it was when it was one whole mirror. And second, to be able to correct for the defect, from the fact that there’s a lot of missing information with so many pieces of mirror that are not there, and you’re only sampling a few pieces. But this particular technique called aperture synthesis, which is to make a very large aperture telescope by using small pieces, of course, is the produce of Nobel prize winning work by Ryle and Hewish some years ago.

Fraser: What instruments are going to be developed in the future to take advantage of this wavelength?

Ho: After our telescopes are built and we’re working, there will be an even larger instrument that’s being constructed now in Chile called the Atacama Large Millimeter Array (ALMA), which will consist of many more telescopes and larger apertures, which will be much more sensitive than our pioneering instrument. But our instrument will hopefully begin to discovery the signs and the nature of the world in the submillimeter wavelength before the larger instruments come along to be able to follow along and do more sensitive work.

Fraser: How far will those new instruments be able to look? What could they be able to see?

Ho: One of the targets for our discipline of submillimeter astronomy is to look back in time at the earliest part of the Universe. As I mentioned earlier, in the early stage of the Universe, when it was forming galaxies, they tend to be much colder in the early phases when galaxies were being assembled, and it will radiate, we think, principly in the submillimeter. And you can see them, for example, using the JCM telescope on Mauna Kea. You can see some of the early Universe, which are very highly redshifted galaxies; these are not visible in the optical, but they are visible in the submillimeter, and this array will be able to image them, and locate them very actively as to where they are located in the sky so that we can study them further. These very early galaxies, these early formations, we think are at very high redshifts – we give this number Z, which is a redshift of 6, 7, 8 – very early in the formation of the Universe, so looking back to perhaps 10% of the time when the Universe was being assembled.

Fraser: My last question for you… Deep Impact is coming up in a few weeks. Will your observatories be watching this as well?

Ho: Oh yes, of course. The Deep Impact indeed is something we’re interested in. For our instrument, we have been studying Solar System type bodies, and this includes not only the planets, but also the comets as they come close or impact, we expect to see material to spew off, which we should be able to track in the submillimeter because we’ll be looking not only at the dust emissions, but we will be able to watch the spectral lines of the gasses which come out. So, we’re expecting to be able to turn our attention to this event, and to also be imaging it.

Paul Ho is an astronomer with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

Posted on by Fraser Cain

What’s Up This Week – June 20 – June 26, 2005

View of Mars. Image credit: NASA/JPL. Click to enlarge.
Monday, June 20 – Have you checked out Mars lately? Today Mars crosses the celestial equator positioning it higher amoungst the constellations. Since we are focusing on planetary motions this week, see in your mind’s eye that we are on a type of racetrack. Since Earth is closer to the Sun than Mars, we move around that inside track much quicker, and right now we are coming up behind Mars at a speed of 23,500 mph, which means Mars getting bigger and brighter every day – and will be spectacular by October. Now rather “football” shaped, be sure to look in a telescope to see if you can catch a glimpse of the polar caps. Be sure to check next week when the crescent Moon and Mars make a pleasing conjunction in the morning sky!

Tonight on the lunar surface, use binoculars to spot the dark oval of Grimaldi just south of central on the terminator. If you chose to scope, look for the great form of Pythagorus to the north and its sharp central peak.

Although the peak time for the June Ophiuchids happened in the early morning hours, you still might catch some of the stream tonight. Its radiant is near Sagittarius and the fall rate varies from 8 to 20, with possibility of many more.

Tuesday, June 21 – Today the Sun achieves its highest point for the year at midday for the northern hemisphere. Known as the Summer Solstice the exact moment occurs at 06:46 UT, and also marks the Winter Solstice for our friends in the Southern Hemisphere.

For most observers, the Moon will appear to be full, but will not actually reach that point until 04:14 UT tomorrow morning. Just take some time to watch it rise! Known as the Rose Moon, Strawberry Moon and Honey Moon, if atmospheric conditions are right, you might see an orangish tint to its form, but the real fun is “moon illusion”! Everyone knows the Moon looks larger on the horizon, but did you know this is a psychological phenomena and not a physical one? Prove it to yourself by looking at the rising Moon upright… It looks larger, doesn’t it? Now stand on your head, or find a way comfortable to view it upside down… Now how big is it?

Wednesday, June 22 – Today celebrates the founding of the Royal Greenwich Observatory in 1675. That’s 330 years of astronomy! Also on this date in history, in 1978 James Christy of the US Naval Observatory in Flagstaff, AZ discovered Pluto’s satellite Charon.

Tonight let’s race ahead of the rising Moon and capture comet 9/P Tempel 1. (Remember there are very accurate night-by-night locator charts on Heavens Above.) If you can find Jupiter, then you’re definitely in the neighborhood to locate this comet. Just to Jupiter’s east is Omicron Virginis. Consider this to be “one step”. Now take two more “steps” east and you are in the general vicinity. While the comet is still rather faint for smaller instruments, magnitude 10 should still be within the reach of most backyard scopes.

Thursday, June 23 – The time has come at last! In case the weather should turn cloudy, be sure to go out tonight and enjoy the western horizon just after sunset. The grouping of Venus, Saturn, and Mercury low in the west-northwest should not to be missed. Venus, by far the brightest of the three, sits central. Mercury will appear just slightly more than one degree to Venus’ lower right and Saturn about two and half degrees to Venus’ upper left. Timing is critical, so start your observations about 30 to 45 minutes after sunset.

Once you’ve viewed the planets, let’s set a telescope toward 6 Comae, just east of Denebola. Less than a degree (50′) to its southeast, you will find the spectacular M99. Discovered by Mechain in 1781 and then confirmed by Messier, this magnitude 10.5 spiral beauty has wonderful structure and a highly apparent arm to smaller scopes on the west side. Return to 6 Comae and travel a half degree to the west and you will find M98. Again discovered by Mechain in 1781, this nearly edge-on spiral has a bright nucleus and is very extended for the larger scope.

Friday, June 24 – On this day in 1881, Sir William Huggins makes the first photographic spectrum of a comet (1881 III) and discovers the cyanogen (CN) emission at violet wavelengths. This discovery caused near mass hysteria some 29 years later when Earth passed through the tail of Halley’s Comet.

Our trio of planets, Saturn, Venus and Mercury have now come together within two and a half degrees of each other, making the area small enough to fit easily within most all binocular’s field of view. The orbital motions of Venus and Mercury are carrying them past Saturn, so watch as the “Ring King” drops away over the next few days. Please take the time to look at the extraordinary display of planetary motion!

Since Huggins viewed a comet 124 years ago on this night, why don’t we? The “Magnificent Machholz” is still around and sailing through Canes Venetici. Locate bright Cor Caroli and head south about two degrees to identify star 14. You will find C/2004 Q2 just about a degree to its southeast.

Saturday, June 25 – The planetary show just keeps getting better as our trio reaches its tightest configuration after sunset tonight. Saturn, Venus and Mercury are now within a degree and half of each other, and easily covered by your thumb held at arm’s length. Their relative positions planets are changing rapidly, with Saturn dropping to the lower left of Venus and Mercury to the lower right. This will be an awesome photographic opportunity and I wish all of you success and clear skies!

Sunday, June 26 – Today is the birthday of none other than Charles Messier, the famed French comet hunter. Born in 1730, Messier is best known for cataloging the 100 or so bright nebulae and star clusters the we now refer to as the Messier objects. The catalog was to keep both Messier and others from confusing these stationary objects with possible new comets. In 1949, asteroid Icarus was discovered on a 48-inch Schmidt plate made nine months after the telescope went into operation, and just prior to the beginning of the multi-year National Geographic – Palomar Sky Survey. The asteroid was found to have a highly eccentric orbit and a perihelion distance of just 17 million miles, closer to the Sun than Mercury, giving it its unusual name. It was just four million miles from Earth at the time of discovery, and variations in its orbital parameters have been used to determine Mercury’s mass and test Einstein’s theory of general relativity.

And what of Mercury? Tonight both Mercury and Venus have moved above Saturn by about a degree and a half, almost doubling that separation. Get out your scopes, because Venus and Mercury now are only 0.2 degrees apart. But wait… The show gets even better tomorrow night! Be sure to look for next week’s “What’s Up”!

For now, the Moon rises later and later each night allowing us more opportunity to study the deep sky! May all your journeys be at Light Speed… ~Tammy Plotner

Posted on by Fraser Cain

Saturn’s Ripply F-Ring

Saturn’s F-Ring with Pandora, one of its shepherd moons. Image credit: NASA/JPL/SSI. Click to enlarge.
The shepherd moon, Pandora, is seen here alongside the narrow F ring that it helps maintain. Pandora is 84 kilometers (52 miles) across.

Cassini obtained this view from about four degrees above the ringplane. Captured here are several faint, dusty ringlets in the vicinity of the F ring core. The ringlets do not appear to be perturbed to the degree seen in the core.

The appearance of Pandora here is exciting, as the moon’s complete shape can be seen, thanks to reflected light from Saturn, which illuminates Pandora’s dark side. The hint of a crater is visible on the dark side of the moon.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 4, 2005, at a distance of approximately 967,000 kilometers (601,000 miles) from Pandora and at a Sun-Pandora-spacecraft, or phase, angle of 117 degrees. The image scale is 6 kilometers (4 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. For additional images visit the Cassini imaging team homepage http://ciclops.org.

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Few Planets Will Have Time to Form Complex Life

NASA Pathfinder mission exploring the surface of Mars. Image credit: NASA/JPL. Click to enlarge.
Whether life exists on other planets remains one of the great unanswered questions of science. Recent research argues that an atmosphere rich in oxygen is the most feasible source of energy for complex life to exist anywhere in the Universe, thereby limiting the number of places life may exist.

Professor David Catling at Bristol University, along with colleagues at the University of Washington and NASA, contend that significant oxygen in the air and oceans is essential for the evolution of multicellular organisms, and that on Earth the time required for oxygen levels to reach a point where animals could evolve was almost four billion years.

Since four billion years is almost half the anticipated life-time of our sun, life on other planets orbiting short-lived suns may not have had sufficient time to evolve into complex forms. This is because levels of oxygen will not have had time to develop sufficiently to support complex life, before the sun dies. Professor Catling said: “This is a major limiting factor for the evolution of life on otherwise potentially habitable planets.”

The research is published in the June 2005 issue of Astrobiology.

Professor Catling is also part of the science team for NASA’s Phoenix Lander, which recently got the go-ahead to put a long-armed lander on Mars in 2007. A robotic arm on the lander will dig a metre into the soil to examine its chemistry. “A key objective is to establish whether Mars ever had an environment conducive to more simple life”, said Professor Catling.

Professor Catling is one of the country’s first Professors of Astrobiology and has recently returned from the USA to take up a post at the University of Bristol. He took up a prestigious ‘Marie Curie Chair’, an EU-funded position designed to help reverse the brain drain, particularly to the USA, and to encourage leading academics to return to and work in Europe. These posts aim to attract world-class researchers. Professor Catling is an internationally recognised researcher in planetary sciences and atmospheric evolution.

As well as his research into the surface and climate of Mars, Professor Catling aims to produce a more quantitative understanding of how the Earth’s atmosphere originated and evolved.

He comments: “Earth’s surface is stunningly different from that of its apparently lifeless neighbours, Venus and Mars. But when our planet first formed its surface must also have been devoid of life. How the complex world around us developed from lifeless beginnings is a great challenge that involves many scientific disciplines such as geology, atmospheric science, and biology”.

Professor Catling grew up in Suffolk and received his doctorate from Oxford, but he has been working in the USA for the past decade: six years as a NASA scientist, followed by four years at the University of Washington in Seattle.

Professor Catling is now based in the Department of Earth Sciences at the University of Bristol. He said of his return to the UK: “It’s great to be back and I’m looking forward to getting started at Bristol. My research will focus on how Earth and Mars evolved over the history of the solar system to produce such startlingly different environments at their surface.”

Professor Catling will give a public lecture approximately every nine months on topics such as the question of life on Mars, or results from recent missions to Mars.

Original Source: Bristol University News Release

Posted on by Fraser Cain

Progress 18 Docks

Ground controllers watching video of the final moments of docking. Image credit: Energia. Click to enlarge.
An unpiloted Russian cargo ship linked up to the International Space Station today to deliver more than two tons of food, fuel, oxygen, water, supplies and spare parts.

The ISS Progress 18 craft docked to the aft port of the Zvezda Service Module at 7:42 p.m. CDT as the Station flew 225 statute miles near Beijing, China. Within minutes, hooks and latches between the two ships engaged, forming a tight seal. The docking completed a two-day journey for the cargo ship since its liftoff Thursday from the Baikonur Cosmodrome in Kazakhstan.

As the Progress approached the Station, Expedition 11 Commander Sergei Krikalev had to take over manual control of the docking of the Progress due to a Russian ground station problem that prevented commands to be uplinked to the cargo ship for its final approach for an automated docking. Nonetheless, Krikalev executed a flawless linkup. NASA Flight Engineer and Science Officer John Phillips took video and still photos of the arrival.

The Progress is loaded with 397 pounds of propellant, 242 pounds of oxygen and air, 926 pounds of water and more than 3,000 pounds of spare parts, life support system components and experiment hardware. In addition, the Progress carries 40 new solid-fuel oxygen generating canisters as a supplemental source of oxygen, if required. The crew will open the Progress hatch later today but will not begin to unload the ship?s cargo until Sunday.

Among the items on the Progress is a new digital camera to be used by the Expedition 11 crew to capture images of the thermal protection system on the Shuttle Discovery during its approach to the Station during the STS-114 mission in July. The camera replaces a similar one that is no longer operable. The photos are part of the imagery-gathering effort to ensure that the Shuttle has no threatening damage to its heat shielding.

Information on the crew’s activities aboard the Space Station, future launch dates, as well as Station sighting opportunities from anywhere on the Earth, is available on the Internet at:

http://www.nasa.gov

Original Source: NASA News Release

Posted on by Fraser Cain

Redesigning Universe Today

You might have noticed, I’m starting to implement my new design for Universe Today into the website – folks reading the newsletter have seen this for a few weeks already. What I’m hoping is that this new design is simpler and cleaner, and lets you get to the news with less distractions. I’ve made the text a little larger to go with the bigger pictures, and put a big list of the last 30 articles over onto the right-hand side of the page, so you can see what’s on the site at a glance. It has less advertising… for now. It’s also much easier for me to maintain. Most of the site has adopted this new look, but I still have lots of copy-pasting to do to get everything fully going, so you’ll see the old site peeking through here and there. I’m also going to be tweaking it endlessly, so things will continue to shift and change.

Please give me any feedback, suggestions or let me know if you find any bugs. You can always email me at [email protected]

Fraser Cain
Publisher, Universe Today

Posted on by Fraser Cain

A Star in the Making

Examples of Bok globules. Image credit: SAAO. Click to enlarge.
Our Sun has been around for almost five billion years. Throughout most of its history the Sun has pretty much appeared the way it does today – a vast sphere of radiant gas and dust lit to incandescence by heat liberated through hydrogen fusion near its core. But before our Sun took form, matter had to be drawn together from the interstellar medium (ISM) and compacted in a small enough region of space to pass a critical balance between further condensation and stability. For this to occur, a delicate balance between outwardly exerted internal pressure and inward moving gravitational influence had to be overcome.

In 1947, Harvard observational astronomer Bart Jan Bok announced the result of years of study of an important subset of cold gases and dust often associated with extended nebulosity. Bok suggested that certain isolated and distinct globules obscuring background light in space were in fact evidence of an important preliminary stage in the formation of protostellar disks leading to the birth of stars such as our sun.

Subsequent to Bok’s announcement, many physical models emerged to explain how Bok globules could come to form stars. Typically, such models begin with the notion that matter comes together in regions of space where the interstellar medium is especially dense (in the form of nebulosity), cold, and subject to radiation pressure from neighboring stars. At some point enough matter may condense into a small enough region that gravitation overcomes gas pressure and the balance tips in favor of star formation.

According to the paper “Near Infrared Imaging Survey of Bok Globules: Density Structure”, published June 10, 2005 Ryo Kandori and a team of fourteen other investigators “suggest that a nearly critical Bonner-Ebert sphere characterizes the critical density of starless globules.”

The concept of a Bonner-Ebert sphere originates with the idea that a balance of forces can exist within an idealized cloud of gas and dust. Such a sphere is held to have a constant internal density while maintaining equilibrium between the expansionary pressure caused by gases of a given temperature and density and the gravitational influence of its total mass assisted by any gas or radiation pressure exerted from neighboring stars. This critical state relates to the diameter of the sphere, its total mass, and the amount of pressure generated by latent heat within it.

Most astronomers have assumed that the Bonner-Ebert model – or some variation thereof – would ultimately prove accurate in describing the point when a particular Bok globule crosses the line to become a protostellar disk. Today, Ryo Kandori et al have gathered enough evidence from a variety of Bok globules to strongly suggest that this notion is correct.

The team started by selecting ten Bok globules for observation based on small apparent size, near-circular shape, distance from neighboring nebulosity, proximity to the Earth (less than 1700 LYs away), and accessibility to near-infrared and radio wave collecting instruments located in both the northern and southern hemispheres. From a list of nearly 250 such globules, only those meeting the above criteria were included. Among those selected only one showed evidence of a protostellar disk. This one disk took the form of a point source of infrared light detected during an all-sky survey performed by IRAS (Infrared Astronomy Satellite – a joint project of the US, UK, and Netherlands). All ten globules were located in star and nebulosity rich regions of the Milky Way.

Once candidate Bok globules were selected, the team subjected each of them to a battery of observations designed to determine their mass, density, temperature, size, and if possible, the amount of pressure applied on them by the ISM and neighboring starlight. One important consideration was to get a sense if there were any variations in density throughout the globule. The presence of uniform pressure is particularly important when it comes to determining which of a variety of theoretical models best mapped against the constitution of the modules themselves.

Using a ground-based instrument (the 1.4 meter IRSF at the South African Astronomical Observatory) in 2002 and 2003, near-infrared light in three different bands (J, H, & K) was collected from each globule to magnitude 17 plus. The images were then integrated and compared to light originating from the background star region. This data was subjected to several analysis methods to allow the team to derive the density of gas and dust across each globule down to the level of resolution supported by seeing conditions (roughly one arc second). That work basically determined that each globule showed a uniform density gradient based on its projected three-dimensional distribution. The Bonner-Ebert sphere model looked like a very good match.

The team also observed each globule using the 45 meter radio telescope of the Nobeyama Radio Observatory in Minamisaku, Nagano, Japan. The idea here was to collect specific radio frequencies associated with excited N2H+ and C18O. By looking at the amount of blur in these frequencies the team was able to determine the internal temperature of each globule which, along with the density of the gas, can be used to approximate the gas pressure internal to each globule.

After gathering the data, subjecting it to analysis, and quantifying the results, the team “found that more then half of the starless globules (7 out of 11 sources) are located near the (Bonner-Ebert) critical state. Thus we suggest that a nearly critical Bonner-Ebert sphere characterizes the typical density structure of starless globules.” In addition the team determined that three Bok globules (Coalsack II, CB87 & Lynds 498) are stable and clearly not in process of star formation, four (Barnard 66, Lynds 495, CB 161 & CB 184) are poised near the stable Bonner-Ebert state but tending toward star formation based on that model. Finally the remaining six (FeSt 1-457, Barnard 335, CB 188, CB 131, CB 134) are clearly moving toward gravitation collapse. Those six “stars in the making” include globules CB 188 and Barnard 335 already known to possess protostellar disks.

On any relatively cloudless day it doesn’t take much in the way of instrumentation to prove that one very unique and important ‘Bok globule’ existing some 5 billion years ago did manage to tip the scales and become a star in the making. Our Sun is firey proof that matter – once adequately condensed – can begin a process that leads to some extraordinary new possibilities.

Written by Jeff Barbour

Posted on by Fraser Cain

Early Black Holes Grew Up Quickly

Illustration of the early Universe. Image credit: NASA. Click to enlarge.
It all began a long time ago while the universe was very young. The earliest massive breeder stars frolicked in their youth – spinning and cavorting among rich green grasses of virgin matter. As their allotted time played out, nuclear engines boiled off expansive streams of hot hydrogen and helium gas – enrichening the interstellar media. During this phase, supermassive star clusters formed in small pockets near nascent galactic cores – each cluster a swim in small regions of primordial mini-halo matter.

Completing their cycle, the earliest breeder stars exploded, spewing forth heavy atoms. But before too much heavy matter accumulated in the Universe, the earliest black holes formed, grew rapidly through mutual assimilation, and accumulated enough gravitational influence to draw “Goldilocks” gases of precise temperatures and composition into large wide accretion disks. This supercritical phase of growth matured the earliest massive black holes (MBHs) rapidly to supermassive black hole (SMBH) status. Out of this the earliest quasars took residence within the fused mini-haloes of numerous protogalaxies.

This picture of early quasar formation emerged from a recent paper (published June 2, 2005) entitled “Rapid Growth of High Redshift Black Holes” written by Cambridge UK Cosmologists Martin J. Rees and Marta Volonteri. That study treats the possibility that a brief window of rapid SMBH formation opened after the time of universal transparency but before gases in the interstellar media fully re-ionized through stellar radiation and seeded with heavy metals by supernovae. The Rees-Volonteri model attempts to explain facts coming out of the Sloan Digital Sky Survey (SDSS) dataset. By 1 billion years after the Big Bang, many highly radiant quasars had already formed. Each with SMBHs having masses exceeding 1 billion suns. These had arisen out of “seed black holes” – gravitational cinders left behind after the earliest cycle of supernovae collapse among the first massive galactic clusters. By one billion years post Big Bang, it was all but over. How could so much mass condense so quickly into such small regions of space?

According to Volontari and Rees, “To grow such seeds up to 1 billion solar masses requires an almost continuous accretion of gas…” Working against such a high accretion rate, is the fact that radiation from matter falling into a black hole typically offsets rapid “weight gain”. Most models of SMBH growth show that about 30% of the mass falling toward an intermediate (massive – not supermassive) black hole is converted to radiation. The effect of this is two-fold: Matter that would otherwise feed the MBH is lost to radiation, and outward radiation pressure stifles the march of additional matter inward to feed rapid growth.

The key to understanding rapid SMBH formation lies in the possibility that early accretion disks around MBH’s were not as optically dense as they are today – but “fat” with tenuously distributed matter. Under such conditions, radiation has a wider mean free path and can escape beyond disks without impeding inward motion of matter. Fuel driving the entire SMBH growth process is delivered copiously into the black hole event horizon. Meanwhile, the type matter present in the earliest epoch was mainly monatomic hydrogen and helium – not the kind of heavy metal rich accretion disks of a later era. All of this suggests that early MBH’s grew up in a hurry, ultimately accounting for the many fully mature quasars seen in the SDSS dataset. Such early MBHs must have had mass-energy conversion ratios more typical of fully mature SMBH’s than the MBH’s of today.

Volontari and Rees say that earlier investigators have shown that fully developed “quasars have a mass-energy conversion efficiency of roughly 10%…” The pair cautions however that this mass-energy conversion value comes out of studies of quasars from a later period in Universal expansion and that “nothing is known about the radiative efficiency of pregalactic quasars in the early Universe.” For this reason “the picture we have of the low redshift Universe may not apply at earlier times.” Clearly the early Universe was more densely packed with matter, that matter was at a higher temperature, and there was a higher ratio of non-metals to metals. All these factors say that it?s almost anyone’s best guess as to the mass-energy conversion efficiencies of early MBHs. Since we now must account for why so many SMBHs exist among early quasars, it makes sense that Volontari and Rees use what they know of today’s accretion disks as a means to explain how they such disks may have been different in the past.

And it is the earliest times – before radiation from numerous stars re-ionized gases within the inter-stellar media – that offered conditions ripe for rapid SMBH formation. Such conditions may well have lasted less than 100 million years and required an adept balance in the temperature, density, distribution, and composition of matter in the Universe.

To get the complete picture (as painted in the paper), we start with the idea that the early universe was populated by innumerable mini-halos comprised of dark and baryonic matter with highly massive but exceedingly dense star clusters in their midst. Due to the density of these clusters – and the massiveness of the stars comprising them – supernovae quickly developed to spawn numerous “seed black holes”. These seed BHs coalesced into massive black holes. Meanwhile gravitational forces and real motions rapidly brought the various mini-halos together. This created ever more massive halos capable of feeding MBHs.

In the early Universe, matter surrounding MBHs took the form of huge metal-poor spheroids of hydrogen and helium averaging some 8,000 degrees Kelvin in temperature. At such high temperatures, atoms remain ionized. Due to ionization, there were few electrons associated with atoms to act as photon traps. The effects of radiation pressure diminished to the point where matter fell more readily into a black holes event horizon. Meanwhile free electrons themselves scatter light. Some of that light actually re-radiates back toward the accretion disk and another source of mass – in the form of energy – feeds the system. Finally a dearth of heavy metals – such as oxygen, carbon, and nitrogen – means that monotomic atoms remain hot. For as temperatures fall below 4,000 degrees K, atoms de-ionize and again become subject to radiation pressure reducing the flux of fresh matter falling into the BH event horizon. All these purely physical properties tended to push mass-energy efficiency ratios down – allowing MBHs to put on weight rapidly.

Meanwhile as mini-halos coalesced, hot baryonic matter condensed into huge “thick” disks – not the thin rings seen around the SMBH’s today. This came about because halo matter itself completely surrounded the rapidly growing MBHs. This spheroidal distribution of matter provided a constant source of fresh, hot, virgin matter to feed the accretion disk from a variety of angles. Thick disks meant greater amounts of matter at lower optical density. Once again, matter managed to avoid being “solar-sailed” outward away from the looming maw of the MBH and mass-energy conversion ratios fell.

Both factors – fat disks and ionized, low mass atoms – say that during the golden age of an early green Universe, MBHs grew up fast. Within one billion years of the Big Bang they had settled down into a relatively quiet maturity efficiently converting matter into light and casting that light across vast reaches of time and space into a potentially ever-expanding Universe.

Written by Jeff Barbour

Posted on by Fraser Cain

Foton-M2 Mission Returns to Earth

Computer illustration of the Foton-M2 satellite. Image credit: ESA. Click to enlarge.
The re-entry module of the Foton-M2 spacecraft, which has been in low-Earth orbit for the last 16 days made a successful landing today in an uninhabited area 140 km south-east of the town of Kostanay in Kazakhstan, close to the Russian border at 09:37 Central European Time, 13:37 local time.

The unmanned Foton-M spacecraft, which was launched on 31 May from the Baikonur Cosmodrome in Kazakhstan, carried a European payload of 385 kg covering 39 experiments in fluid physics, biology, crystal growth, meteoritics, radiation dosimetry and exobiology.

All de-orbit to landing procedures went according to plan beginning with the jettison of the Foton-M2 battery module three hours prior to landing. At an altitude of about 300 kilometres, travelling at 7.8 km/s and 30 minutes prior to landing, the retro-rocket situated on the Foton service module was fired for 45 seconds slowing the spacecraft down to reduce its altitude. The Foton-M2 service module was hereafter separated from the re-entry module and, as planned, burnt up in Earth?s atmosphere.

Twenty minutes prior to landing the spherical re-entry module entered the stratosphere, experiencing temperatures up to 2000?C and an acceleration of up to 9g. At 8.5 minutes before landing, the drogue parachute was deployed, which in turn opened the brake parachute, reducing the descent speed from supersonic to subsonic. The main parachute was deployed thirty seconds later, at an altitude of 2.5 km, reducing the speed of the re-entry module to 10 m/s. Brake rockets finally reduced the speed of the re-entry module to 3 m/s, 0.35 seconds before landing impact.

ESA representatives were on hand at the landing site to undertake initial procedures related to European experiments. This included immediate retrieval of the Biopan, Stone and Autonomous Experiments. The same team removed the FluidPac experiment facility?s digital tape recorder and configured FluidPac for safe transport to the TsSKB-Progress factory in Samara. The Foton capsule is currently being transported to Samara where the FluidPac facility and the Telescience Support Unit will be removed from the capsule and shipped to ESA/ESTEC in Noordwijk, the Netherlands.

?I am extremely pleased that the majority of experiments have performed well.? said ESA?s Project Manager for Foton missions, Antonio Verga. ?My thanks to the ESA Operations Team who has closely followed the mission from the Payload Operations Centre at Esrange in Kiruna, Sweden and our Russian counterparts at Roskosmos, TsSKB-Progress and the Barmin Design Bureau for General Engineering. The hard work and dedication of everyone involved has been crucial in making this mission a success and optimising the scientific returns from the mission?.

The Foton-M2 staff at Esrange, consisted of a team of 30 scientists, engineers and operators who worked in close coordination with the Mission Operation Centre at TsSKB, Samara, and with the Flight Control Centre in Moscow, which continuously reported and informed about the orbital phases of Foton-M2, via a powerful and effective data network operated and maintained by ESA?s European Space Operations Centre (ESOC) in Darmstadt, Germany.

Fluid physics experiments were conducted in the FluidPac and SCCO experiment facilities. The data return from these was nearly complete and most of the scientific objectives were achieved. The BAMBI experiment produced some excellent images, a substantial role in which was played by the on-line processing capability of TeleSupport Unit.

The Agat furnace performed flawlessly as well. The processed samples should provide the material science community with good specimens to analyse. Unfortunately, the Russian Polizon furnace suffered a failure due to as yet unknown reasons, which prevented the processing of the semiconductor alloys stored in its drum at the required high temperatures.

The very successful technology experiment MiniTherm was performed during the mission, which deals with the performance of a new design of heat pipes. This experiment was controlled from Esrange, during its 5 days-long execution.

Also numerous experiments attached to the outside of the Foton satellite were performed, which deal with space exposure and technology aspects.

The European Space Agency has been participating in this type of scientific mission for 18 years and with a total of 385 kg of European experiments and equipment, this mission constituted the largest European payload that has been put into orbit.

“The Foton-M2 mission has been a resounding success and I look forward to seeing the positive impact the results of the experiments will have in the future,? said Daniel Sacotte, ESA?s Director of Human Spaceflight, Microgravity and Exploration Programmes. ?I also look forward to building on this success with the Foton-M3 mission, which is planned to be launched in 2007.?

For more information on the Foton-M2 mission and the status of the ESA experiments: http://www.spaceflight.esa.int/foton

Original Source: ESA News Release

Posted on by Fraser Cain

Second MARSIS Boom Deployed

Artist illustration of Mars Express deploying its MARSIS boom. Image credit: ESA. Click to enlarge.
The second 20-metre antenna boom of the MARSIS instrument on board Mars Express was successfully ? and smoothly ? deployed, confirmed today by the ground team at ESA?s European Space Operations Centre.

The command to deploy the second MARSIS boom was given to the spacecraft at 13:30 CEST on 13 June 2005.

Shortly before the deployment started, Mars Express was set into a slow rotation to last 30 minutes during and after the boom extension. This rotation allowed all the boom?s hinges to be properly heated by the Sun.

Just after, an autonomous manoeuvre oriented the spacecraft towards the Sun, to have the spacecraft recharge its batteries and for a further heating of the hinges.

A first positive sign reached ground in the afternoon of 14 June, at 16:20 CEST, when Mars Express was able to properly re-orient itself and point towards Earth to transmit data.

The data received in the following hours confirmed that the initial spacecraft behaviour was consistent with two fully and correctly deployed booms and that the deployment had not induced disturbance frequencies that may have been dangerous for the spacecraft.

A series of tests during the following 48 hours was necessary to verify that the long boom was successfully locked and that the deployment did not affect the integrity of the spacecraft systems.

The complete success of the operation was announced today at 14:00 CEST, when the ground team had completed all tests on the spacecraft systems. This confirmed that the spacecraft is in optimal shape and under control, with the second MARSIS boom straight and locked into the correct position.

With the two MARSIS 20-metre radar booms fully deployed, Mars Express is already in principle capable of ?looking? beneath the Martian surface, and also studying its ionosphere (the upper atmosphere). The third 7-metre ?monopole? boom, to be deployed perpendicularly to the first two booms, will be used to correct some surface roughness effects on the radio waves emitted by MARSIS and reflected by the surface.

The third boom deployment, not considered critical because of its orientation and shorter length, will take place on 17 June 2005. It will be followed by further tests on the spacecraft and the MARSIS instrument for a few more days.

The radar, with its long booms, will allow Mars Express to continue its search for water on Mars. By night, it will be used to make soundings for water below the surface. By day, it will probe the structure of the ionosphere.

Jean-Jacques Dordain, ESA Director General, said: “This is a great success following some tense moments and careful judgements. The result shows the power of the teamwork between ESA, European industry and ESA’s partners in the scientific community in Europe and elsewhere.”

Original Source: ESA News Release