Category: Astronomy

Michiel Min is a research student at the Astronomical Institute, University of Amsterdam, who carried out much of the data analysis behind the current ESO release, see: Ingredients are There to Make Rocky Planets. Michiel was able to talk with Universe Today in between his studies.

Universe Today: Do your findings help to explain the origin of our own solar system in better detail?

Michiel Min: The timescale of planet formation is still under debate. Our findings provide evidence that the small dust grains are already growing after a billion years. Our observations do provide a unique view of the building blocks of planets. It is clear from our findings that the building blocks of Earth-like planets, close to the star, are crystals (crystalline silicates), while the building blocks of the planets further out, are amorphous silicates. Also we see that the growth of dust grains seems to go easier closer to the star.

Have your observations provided an answer as to how these planetary systems around giant stars may have formed?

The main reason that only giant planets in close orbits have been found has to do with the way of detecting these systems. Taking into account the gravitational pull of the planet on the star does this. Most likely, these planetary systems formed in a similar way as our own solar system. However, in these systems, most likely, the planet has moved inwards due to friction in the disk. If a planet forms very close to the star, it is more likely that it will be a rockier, earth-like planet since its atmosphere will greatly evaporate. Detecting smaller, earth-like planets directly is very hard. At the moment, planet-finders like Darwin are being build to search, in a very clever way, for the signal of Earth-like planets. Our findings give us a look in the birthplace of these planets.

So, how close would a giant planet need to be to its parent star for its atmosphere not to evaporate away?

This depends all on the mass of the planet itself and the temperature of the star. Most likely, giant planets only form at distances beyond ~5 AU [750 million kilometres] around a solar type star. But this is only a very rough number. If one considers for example Pluto, which is a rocky planet that formed quite far away, it is clear that there is not a simple answer to this.

Michiel, could you please say a little about yourself, and how you became interested in astronomy?

Yes, I am a PhD student at the University of Amsterdam. I will finish my PhD in April 2005. I have always been interested in science and how nature works. I studied physics in Amsterdam, at the Free University. After this, I got interested in astronomy because it is one of the few fields in physics where you meet all the extremes of nature. I think this provides a unique challenge for the mind. The study of planetary systems is one of the most down-to-earth subjects in astronomy. It is directly related to our own Earth. I think the question ‘what created this planet?’ is fascinating. Also, the question how planetary systems form, can provide us with an answer to how unique our own solar system is, and how easy one forms a planet like the Earth around other stars.

Looking toward the future, how long do you think it will be before astronomers have the technical ability to detect earth-like planets?

There are currently two project running to make instruments for detecting planets: DARWIN (ESA) and Terrestrial Planet Finder (NASA). Both missions are planned for launch in the year 2014. Both these missions should be able to detect Earth-like planets.

I think we are in a very exciting time in that respect. Our findings imply that all the materials to form Earth-like planets are available in the regions where liquid water can exist. Also, the process of dust growth has started its way to forming larger bodies. In my opinion, this implies that it is very likely that the planet finders of ESA and NASA will detect planets around solar type stars. Our understanding of Venus, the Earth and Mars, puts nice constraints on the conditions we can expect on these planets, and if these conditions support the possibility of life. Therefore I hope, and think, the question if our solar system is unique or not, will be answered in the coming 10-15 years.

This research project was a collaboration with the Astronomical Institute of the University of Amsterdam, The Netherlands (NOVA PR) and the Max-Planck-Institute f?r Astronomie (Heidelberg, Germany (MPG PR). The Amsterdam team consists of Roy van Boekel, Michiel Min, Rens Waters, Carsten Dominik and Alex de Koter.

By Science Correspondent Richard Pearson.

Images of beautiful galaxies, and in particular of spiral brethren of our own Milky Way, leaves no-one unmoved. It is difficult indeed to resist the charm of these impressive grand structures. Astronomers at Paranal Observatory used the versatile VIMOS instrument on the Very Large Telescope to photograph two magnificent examples of such “island universes”, both of which are seen in a southern constellation with an animal name. But more significantly, both galaxies harboured a particular type of supernova, the explosion of a massive star during a late and fatal evolutionary stage.

This image is of the impressive spiral galaxy NGC 6118 [1], located near the celestial equator, in the constellation Serpens (The Snake). It is a comparatively faint object of 13th magnitude with a rather low surface brightness, making it pretty hard to see in small telescopes. This shyness has prompted amateur astronomers to nickname NGC 6118 the “Blinking Galaxy” as it would appear to flick into existence when viewed through their telescopes in a certain orientation, and then suddenly disappear again as the eye position shifted.

There is of course no such problem for the VLT’s enormous light-collecting power and ability to produce sharp images, and this magnificent galaxy is here seen in unequalled detail. The colour photo is based on a series of exposures behind different optical filters, obtained with the VIMOS multi-mode instrument on the 8.2-m VLT Melipal telescope during several nights around August 21, 2004.

About 80 million light-years away, NGC 6118 is a grand-design spiral seen at an angle, with a very small central bar and several rather tightly wound spiral arms (it is classified as of type “SA(s)cd” [2]) in which large numbers of bright bluish knots are visible. Most of them are active star-forming regions and in some, very luminous and young stars can be perceived.

Of particular interest is the comparatively bright stellar-like object situated directly North of the galaxy’s centre, near the periphery (see PR Photo 33b/04): it is Supernova 2004dk that was first reported on August 1, 2004. Observations a few days later showed this to be a supernova of Type Ib or Ic [3], caught a few days before maximum light. This particular kind of supernova is believed to result from the demise of a massive star that has somehow lost its entire hydrogen envelope, probably as a result of mass transfer in a binary system, before exploding.

Also visible on the image is the trail left by a satellite, which passed by during one of the exposures taken in the B filter, hence its blue colour. This is an illustration that even in such a remote place as the Paranal Observatory in the Atacama desert, astronomers are not completely sheltered from light pollution.

The second galaxy imaged by the VLT is another spiral, the beautiful multi-armed NGC 7424 that is seen almost directly face-on. Located at a distance of roughly 40 million light-years in the constellation Grus (the Crane), this galaxy was discovered by Sir John Herschel while observing at the Cape of Good Hope.

This other example of a “grand design” galaxy is classified as “SAB(rs)cd” [2], meaning that it is intermediate between normal spirals (SA) and strongly barred galaxies (SB) and that it has rather open arms with a small central region. It also shows many ionised regions as well as clusters of young and massive stars. Ten young massive star clusters can be identified whose size span the range from 1 to 200 light-years. The galaxy itself is roughly 100,000 light-years across, that is, quite similar in size to our own Milky Way galaxy.

Because of its low surface brightness, this galaxy also demands dark skies and a clear night to be observed in this impressive detail. When viewed in a small telescope, it appears as a large elliptical haze with no trace of the many beautiful filamentary arms with a multitude of branches revealed in this striking VLT image. Note also the very bright and prominent bar in the middle.

On the evening of 10 December 2001, Australian amateur astronomer Reverend Robert Evans, observing from his backyard in the Blue Mountains west of Sydney, discovered with his 30cm telescope his 39th supernova, Supernova 2001ig in the outskirts of NGC 7424. Of magnitude 14.5 (that is, 3000 times fainter than the faintest star that can be seen with the unaided eye), this supernova brightened quickly by a factor 8 to magnitude 12.3. A few months later, it had faded to an insignificant object below 17th magnitude. By comparison, the entire galaxy is of magnitude 11: at the time of its maximum, the supernova was thus only three times fainter than the whole galaxy. It must have been a splendid firework indeed!

By digging into the vast Science Archive of the ESO Very Large Telescope, it was possible to find an image of NGC 7424 taken on June 16, 2002 by Massimo Turatto (Observatorio di Padova-INAF, Italy) with the FORS 2 instrument on Yepun (UT4). Although, the supernova was already much fainter than at its maximum 6 months earlier, it is still very well visible on this image (see PR Photo 33d/04).

Spectra taken with ESO’s 3.6-m telescope at La Silla over the months following the explosion showed the object to evolve to a Type Ib/c supernova. By October 2002, the transition to a Type Ib/c supernova was complete. It is now believed that this supernova arose from the explosion of a very massive star, a so-called Wolf-Rayet star, which together with a massive hot companion belonged to a very close binary system in which the two stars orbited each other once every 100 days or so. Future detailed observations may reveal the presence of the companion star that survived this explosion but which is now doomed to explode as another supernova in due time.

[1] NGC stands for “New General Catalogue”. Published in 1888 by J.L.E. Dreyer, this New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel contains 7840 objects of which 3200 are galaxies.

[2] Spiral galaxies take their name from the spectacular spiral arms that wind around in a very thin disc. Following the celebrated classification by American astronomer Edwin Hubble, spiral galaxies are classified into two families, so-called normal spirals (SA) and barred spirals (SB), and are further divided into types Sa, Sb and Sc depending on the opening of the spiral arms and the relative brightness of the central area. In barred spiral galaxies, the nucleus is crossed by a bar of stars at the ends of which the spiral arms begin. The (rs) in the classification testifies to the presence of an internal ring (r) surrounding the nucleus of the galaxy as well as to the fact that the spiral arms begin directly at the nucleus (s).

[3] Supernovae are classified into different types, depending on the appearance of their spectrum. Type II supernovae show the presence of hydrogen lines in their spectra while Type I lack this signature. Type I have been subdivided into Type Ia, Ib and Ic. Type I supernovae are all believed to arise in binary stellar systems.

Original Source: ESO News Release

Subaru telescope has witnessed a large galaxy in the act of devouring a small companion galaxy in a new image obtained by Yoshiaki Taniguchi (Tohoku University), Shunji Sasaki (Tohoku University), Nicolas Scoville (California Institute of Technology) and colleagues. The evidence is a wispy band of stars extending over 500 thousand light years, the faintest and longest known example of its kind.

Current theories of galaxy formation suggest that large galaxies like the Milky Way grow by consuming smaller dwarf galaxies. Evidence of this process can be found in our own galactic neighborhood. Some stars in the Milky Way appear to have once belonged to a small nearby galaxy called the Sagitarius Dwarf. Our closest large neighbor galaxy Andromeda also shows evidence for past galactic astronomy. However, in both cases these conclusions are inferred from “post-digestive” observations.

The destruction of dwarf galaxies is difficult to observe because dwarf galaxies are inherently faint and their light becomes increasingly diffuse as stars get pulled away by a larger galaxy. The only previously known observation of the destruction of a dwarf galaxy in progress is from the Advanced Camera for Surveys on the Hubble Space Telescope.

Taniguchi, Sasaki, Scoville and colleagues serendipitously discovered the large elliptical galaxy (COSMOS J100003+020146) pulling apart the dwarf galaxy (COSMOS J095959+020206) while observing an area of sky in the constellation Sextans to study the properties of galaxies over large scales in space and time. The pair of galaxies is about one billion light years away and the distance between the two galaxies is about 330 thousand light years.

The thin band of stars extending from the dwarf galaxy both toward and away from the large elliptical galaxy reveals that the gravity of the elliptical is tidally tearing the dwarf apart. Stars that are closest to the elliptical galaxy experience a stronger pull than stars in the center of the dwarf galaxy, and stars on the opposite side experience a weaker pull. As a result, the dwarf galaxy becomes stretched and looks as if it’s being pulled from two opposite directions even though there is only one galaxy doing the pulling. This effect is comparable to how two areas on the opposite sides of Earth experience high tide at the same time even though there is only one Moon tugging on Earth’s oceans.

The tidally torn strip of stars in the newly observed pair of galaxies is five times more extended and three times fainter in surface brightness than the one observed with Hubble Space Telescope. Subaru telescope’s ability to gather large amounts of light and focus it into a superbly sharp image was essential for this new discovery.

As astronomers find more examples of galactic cannibalism in action, our knowledge of the history of galaxies should become increasingly vivid. Although no human alive today will be able to witness the ultimate of fate of the newly discovered pair, chances are the elliptical galaxy will be able to complete the meal it’s begun and fully consume its neighbor.

Original Source: Subaru News Release

Star formation is one of the most basic phenomena in the Universe. Inside stars, primordial material from the Big Bang is processed into heavier elements that we observe today. In the extended atmospheres of certain types of stars, these elements combine into more complex systems like molecules and dust grains, the building blocks for new planets, stars and galaxies and, ultimately, for life. Violent star-forming processes let otherwise dull galaxies shine in the darkness of deep space and make them visible to us over large distances.

Star formation begins with the collapse of the densest parts of interstellar clouds, regions that are characterized by comparatively high concentration of molecular gas and dust like the Orion complex (ESO PR Photo 20/04) and the Galactic Centre region (ESO Press Release 26/03). Since this gas and dust are products of earlier star formation, there must have been an early epoch when they did not yet exist.

But how did the first stars then form? Indeed, to describe and explain “primordial star formation” – without molecular gas and dust – is a major challenge in modern Astrophysics.

A particular class of relatively small galaxies, known as “Blue Dwarf Galaxies”, possibly provide nearby and contemporary examples of what may have occurred in the early Universe during the formation of the first stars. These galaxies are poor in dust and heavier elements. They contain interstellar clouds which, in some cases, appear to be quite similar to those primordial clouds from which the first stars were formed. And yet, despite the relative lack of the dust and molecular gas that form the basic ingredients for star formation as we know it from the Milky Way, those Blue Dwarf Galaxies sometimes harbour very active star-forming regions. Thus, by studying those areas, we may hope to better understand the star-forming processes in the early Universe.

Very active star formation in NGC 5253
NGC 5253 is one of the nearest of the known Blue Dwarf Galaxies; it is located at a distance of about 11 million light-years in the direction of the southern constellation Centaurus. Some time ago a group of European astronomers [1] decided to take a closer look at this object and to study star-forming processes in the primordial-like environment of this galaxy.

True, NGC 5253 does contains some dust and heavier elements, but significantly less than our own Milky Way galaxy. However, it is quite extreme as a site of intense star formation, a profuse “starburst galaxy” in astronomical terminology, and a prime object for detailed studies of large-scale star formation.

ESO PR Photo 31a/04 provides an impressive view of NGC 5253. This composite image is based on a near-infrared exposure obtained with the multi-mode ISAAC instrument mounted on the 8.2-m VLT Antu telescope at the ESO Paranal Observatory (Chile), as well as two images in the optical waveband obtained from the Hubble Space Telescope data archive (located at ESO Garching). The VLT image (in the K-band at wavelength 2.16 ?m) is coded red, the HST images are blue (V-band at 0.55 ?m) and green (I-band at 0.79 ?m), respectively.

The enormous light-gathering capability and the fine optical quality of the VLT made it possible to obtain the very detailed near-infrared image (cf. PR Photo 31b/04) during an exposure lasting only 5 min. The excellent atmospheric conditions of Paranal at the time of the observation (seeing 0.4 arcsec) allow the combination of space- and ground-based data into a colour photo of this interesting object.

A major dust lane is visible at the western (right) side of the galaxy, but patches of dust are visible all over, together with a large number of colourful stars and stellar clusters. The different colour shades are indicative of the ages of the objects and the degree of obscuration by interstellar dust. The near-infrared VLT image penetrates the dust clouds much better than the optical HST images, and some deeply embedded objects that are not detected in the optical therefore appear as red in the combined image.

Measuring the size and infrared brightness of each of these “hidden” objects, the astronomers were able to distinguish stars from stellar clusters; they count no less than 115 clusters. It was also possible to derive their ages – about 50 of them are very young in astronomical terms, less than 20 million years. The distribution of the masses of the cluster stars ressembles that observed in clusters in other starburst galaxies, but the large number of young clusters and stars is extraordinary in a galaxy as small as NGC 5253.

When images are obtained of NGC 5253 at progressively longer wavelengths, cf. ESO PR Photo 31c/04 which was taken with the VLT in the L-band (wavelength 3.7 ?m), the galaxy looks quite different. It no longer displays the richness of sources seen in the K-band image and is now dominated by a single bright object. By means of a large number of observations in different wavelength regions, from the optical to the radio, the astronomers find that this single object emits as much energy in the infrared part of the spectrum as does the entire galaxy in the optical region. The amount of energy radiated at different wavelengths shows that it is a young (a few million years), very massive (more than one million solar masses) stellar cluster, embedded in a dense and heavy dust cloud (more than 100,000 solar masses of dust; the emission seen in PR Photo 31c/04 comes from this dust).

A view towards the beginnings
These results show that a galaxy as tiny as NGC 5253, almost 100 times smaller than our own Milky Way galaxy, can produce hundreds of compact stellar clusters. The youngest of these clusters are still deeply embedded in their natal clouds, but when observed with infrared-sensitive instruments like ISAAC at the VLT, they stand out as very bright objects indeed.

The most massive of these clusters holds about one million solar masses and shines as much as 5000 very bright massive stars. It may well be very similar to the progenitors in the early Universe of the old globular clusters we now observe in large galaxies like the Milky Way. In this sense, NGC 5253 provides us with a direct view towards our own beginnings.

Note
[1] The group consists of Giovanni Cresci (University of Florence, Italy), Leonardo Vanzi (ESO-Chile) and Marc Sauvage (CEA/DSN/DAPNIA, Saclay, France). More details about the present investigation is available in a research paper (“The Star Cluster population of NGC 5253” by G. Cresci et al.) to appear soon in the leading research journal Astronomy & Astrophysics (a preprint is available as astro-ph/0411486).

Original Source: ESO News Release

Here’s more information about how are stars formed.

The invention of the CAT scan led to a revolution in medical diagnosis. Where X-rays give only a flat two-dimensional view of the human body, a CAT scan provides a more revealing three-dimensional view. To do this, CAT scans take many virtual “slices” electronically and assemble them into a 3D picture.

Now a new technique that resembles CAT scans, known as tomography, is poised to revolutionize the study of the young universe and the end of the cosmic “dark ages.” Reporting in the Nov. 11, 2004, issue of Nature, astrophysicists J. Stuart B. Wyithe (University of Melbourne) and Abraham Loeb (Harvard-Smithsonian Center for Astrophysics) have calculated the size of cosmic structures that will be measured when astronomers effectively take CAT scan-like images of the early universe. Those measurements will show how the universe evolved over its first billion years of existence.

“Until now, we’ve been limited to a single snapshot of the universe’s childhood-the cosmic microwave background,” says Loeb. “This new technique will let us view an entire album full of the universe’s baby photos. We can watch the universe grow up and mature.”

Slicing Space
The heart of the tomography technique described by Wyithe and Loeb is the study of 21-centimeter-wavelength radiation from neutral hydrogen atoms. In our own galaxy, this radiation has helped astronomers to map the Milky Way’s spherical halo. To map the distant young universe, astronomers must detect 21-cm radiation that has been redshifted: stretched to longer wavelengths (and lower frequencies) by the expansion of space itself.

Redshift is directly correlated to distance. The farther a cloud of hydrogen is from the Earth, the more its radiation is redshifted. Therefore, by looking at a specific frequency, astronomers can photograph a “slice” of the universe at a specific distance. By stepping through many frequencies, they can photograph many slices and build up a three-dimensional picture of the universe.

“Tomography is a complicated process, which is one reason why it hasn’t been done before at very high redshifts,” says Wyithe. “But it’s also very promising because it’s one of the few techniques that will let us study the first billion years of the universe’s history.”

A Soap Bubble Universe
The first billion years are critical because that is when the first stars began to shine and the first galaxies began to form in compact clusters. Those stars burned hotly, emitting huge amounts of ultraviolet light that ionized nearby hydrogen atoms, splitting electrons from protons and clearing away the fog of neutral gas that filled the early universe.

Young galaxy clusters soon were surrounded by bubbles of ionized gas much like soap bubbles floating in a tub of water. As more ultraviolet light flooded space, the bubbles grew larger and gradually merged together. Eventually, about a billion years after the Big Bang, the entire visible universe was ionized.

To study the early universe when the bubbles were small and the gas mostly neutral, astronomers must take slices through space as if slicing a block of swiss cheese. Loeb says that just as with cheese, “if our slices of the universe are too narrow, we’ll keep hitting the same bubbles. The view will never change.”

To get truly useful measurements, astronomers must take larger slices that hit different bubbles. Each slice must be wider than the width of a typical bubble. Wyithe and Loeb calculate that the largest individual bubbles reached sizes of about 30 million light-years across in the early universe (equivalent to more than 200 million light-years in the expanded universe of today). Those crucial predictions will guide the design of radio instruments to conduct tomographical studies.

Astronomers soon will test Wyithe and Loeb’s predictions using an array of antennas tuned to operate at the 100-200 megahertz frequencies of redshifted 21-cm hydrogen. Mapping the sky at these frequencies is extremely difficult because of manmade interference (TV and FM radio) and the effects of the earth’s ionosphere on low-frequency radio waves. However, new low-cost electronics and computer technologies will make extensive mapping possible before the end of the decade.

“Stuart and Avi’s calculations are beautiful because once we have built our arrays, the predictions will be straightforward to test as we take our first glimpses of the early universe,” says Smithsonian radio astronomer Lincoln Greenhill (CfA).

Greenhill is working to create those first glimpses through a proposal to equip the National Science Foundation’s Very Large Array with the necessary receivers and electronics, funded by the Smithsonian. “With luck, we will create the first images of the shells of hot material around several of the youngest quasars in the universe,” says Greenhill.

Wyithe and Loeb’s results also will help guide the design and development of next-generation radio observatories being built from the ground up, such as the European LOFAR project and an array proposed by a US-Australian collaboration for construction in the radio-quiet outback of Western Australia.

Original Source: Harvard CfA News Release

Image credit: NASA/JPL
Pluto’s status as our solar system’s ninth planet may be safe if a recently discovered Kuiper Belt Object is a typical “KBO” and not just an oddball.

Astronomers have new evidence that KBOs (Kuiper Belt Objects) are smaller than previously thought.

KBOs – icy cousins to asteroids and the source of some comets – are the leftover building blocks of the outer planets. Astronomers using the world’s most powerful telescopes have discovered about 1,000 of these objects orbiting beyond Neptune since discovering the first one in 1992. These discoveries fueled debate on whether Pluto is a planet or a large (1,400-mile diameter) closer-in KBO.

Researchers estimate that the total mass of the Kuiper Belt is about a tenth of Earth’s mass. Most theorize that there are more than 10,000 KBOs with diameters greater than 100 kilometers (62 miles), compared to 200 asteroids known to be that large in the main asteroid belt between Mars and Jupiter.

“People were finding all these KBOs that were huge – literally half the size of Pluto or larger,” University of Arizona astronomer John Stansberry said. “But those supposed sizes were based on assumptions that KBOs have very low albedos, similar to comets.”

Albedo is a measure of how much light an object reflects. The more light an object reflects, the higher its albedo. Actual data on Kuiper Belt Object albedos have been hard to come by because the objects are so distant, dim and cold. Many astronomers have assumed that KBO albedos – like comet albedos – are around four percent and have used that number to calculate KBO diameters.

However, in early results from their Spitzer Space Telescope survey of 30 Kuiper Belt Objects, Stansberry and colleagues found that a distant KBO designated 2002 AW197 reflects 18 percent of its incident light and is about 700 kilometers (435 miles) in diameter. That’s considerably smaller and more reflective than expected, Stansberry said.

“2002 AW197 is believed to be one of the largest KBOs thus far discovered,” he said. “These results indicate that this object is larger than all but one main-belt asteroid (Ceres), about half the size of Pluto’s moon, Charon, and about 30 percent as large and a tenth as massive as Pluto.”

Stansberry and his colleagues took the data with Spitzer’s Multiband Imaging Photometer (MIPS) on April 13, 2004. George Rieke’s team at the University of Arizona developed and built the extremely heat-sensitive MIPS. It detects heat from very cold objects by taking images at far-infrared wavelengths.

In this case, MIPS detected heat from a Kuiper Belt Object with a surface temperature of around minus 370 degrees Fahrenheit at an astonishing distance of 4.4 billion miles (7 billion kilometers), or one-and-a-half times farther away frm the sun than Pluto.

Without MIPS, astronomers operating under the assumption that 2002 AW197 reflects four percent of its incident light would calculate that it is 1500 kilometers (932 miles) in diameter, or two-thirds as large as Pluto, Stansberry said.

“We’re finally starting to get data on the basic physical parameters of KBOs,” Stansberry said. “That will help us determine what their compositions are, how they evolve, how massive they are, what their real size distributions and dynamics are and how Pluto fits into the whole picture,” he said.

Such data will also offer insight on how comets are processed on their successive journeys around the sun, he added.

“It’s not surprising that comets are darker than KBOs,” Stansberry said.”When something in the Kuiper Belt chips off a piece of a Kuiper Belt Object, presumably that piece would have a higher albedo on its first swing through the inner solar system. But it doesn’t take long before it loses its high albedo surface and builds up a lot of very dark materials, at least in its outermost surface.”

Others with Stansberry in this Spitzer study are Dale Cruikshank and Josh Emery of NASA Ames Research Center, Yan Fernandez of the University of Hawaii, George Rieke of the University of Arizona and Michael Werner of NASA’s Jet Propulsion Laboratory.

Stansberry said the team will finish collecting their KBO data with Spitzer soon.

“We’ll know a lot more about how big and bright these things are by this time next year,” he said.

Stansberry is presenting the research today at the 86th annual meeting of the American Astronomical Society Division of Planetary Science in Louisville, Ky.

More information about this and other new results from the Spitzer Space Telescope is on the Web at http://www.spitzer.caltech.edu/Media/index.shtml The Spitzer Space Telescope is managed for NASA by the Jet Propulsion Laboratory in Pasadena, Calif.

Original Source: University of Arizona News Release

Two new results from NASA’s Spitzer Space Telescope released today are helping astronomers better understand how stars form out of thick clouds of gas and dust, and how the molecules in those clouds ultimately become planets.

Two discoveries — the detection of an oddly dim object inside what was thought to be an empty cloud, and the discovery of icy planetary building blocks in a system believed to resemble our own solar system in its infancy — were presented today at the first Spitzer science conference in Pasadena, Calif. Since Spitzer science observations began less than one year ago, the infrared capabilities of the space observatory have unveiled hundreds of space objects too dim, cool or distant to be seen with other telescopes.

In one discovery, astronomers have detected a faint, star-like object in the least expected of places — a “starless core.” Named for their apparent lack of stars, starless cores are dense knots of gas and dust that should eventually form individual newborn stars. Using Spitzer’s infrared eyes, a team of astronomers led by Dr. Neal Evans of the University of Texas at Austin probed dozens of these dusty cores to gain insight into conditions that are needed for stars to form.

Starless cores are fascinating to study because they tell us what conditions exist in the instants before a star forms. Understanding this environment is key to improving our theories of star formation, said Evans.

But when they looked into one core, called L1014, they found a surprise — a warm glow coming from a star-like object. The object defies all models of star formation; it is fainter than would be expected for a young star. Astronomers theorize that the mystery object is one of three possibilities: the youngest “failed star,” or brown dwarf ever detected; a newborn star caught in a very early stage of development; or something else entirely.

This object might represent a different way of forming stars or brown dwarfs. Objects like this are so dim that previous studies would have missed them. It might be like a stealth version of star formation, Evans said. The new object is located 600 light-years away in the constellation Cygnus.

In another discovery, Spitzer’s infrared eyes have peered into the place where planets are born — the center of a dusty disc surrounding an infant star — and spied the icy ingredients of planets and comets. This is the first definitive detection of ices in planet-forming discs.

This disc resembles closely how we imagine our own solar system looked when it was only a few hundred thousand years old. It has the right size, and the central star is small and probably stable enough to support a water-rich planetary system for billions of years into the future, said Dr. Klaus Pontoppidan of Leiden Observatory in the Netherlands, who led the team that made this discovery.

Previously, astronomers had seen ices, or ice-coated dust particles, in the large cocoons of gas and dust that envelop young stars. But they were not able to distinguish these ices from those in the inner planet-forming portion of a star’s disc. Using Spitzer’s ultra- sensitive infrared vision and a clever trick, Pontoppidan and his colleagues were able to overcome this challenge.

Their trick was to view a young star and its dusty disc at “dawn.” Discs can be viewed from a variety of angles, ranging from the side or edge-on, where the discs appear as dark bars, to face-on, where the discs become washed out by the light of the central star. They found that if they observed a disc at a 20-degree angle, at a position where the star peeks out like our Sun at dawn, they could see the ices.

“We hit the sweet spot,” said Pontoppidan. “Our models predicted that the search for ices in discs is a problem of finding an object with just the right viewing angle, and Spitzer confirmed that model.”

In this system, astronomers found ammonium ions as well as components of water and carbon dioxide ice.

The Spitzer science conference, “The Spitzer Space Telescope: New Views of the Cosmos,” is being held at the Sheraton Pasadena hotel.

JPL manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington, D.C. Science operations are conducted at the Spitzer Science Center, Pasadena, Calif. JPL is a division of Caltech. For more information about Spitzer visit www.spitzer.caltech.edu.

Original Source: NASA/JPL News Release

A team of UK astronomers working with international partners has produced the first ever image of an astronomical object using high energy gamma rays, helping to solve a 100 year old mystery – the origin of cosmic rays. Their research, published in the Journal Nature on November 4th, was carried out using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa.

The astronomers studied the remnant of a supernova that exploded some 1,000 years ago, leaving behind an expanding shell of debris which, seen from the Earth, is twice the diameter of the Moon. The resulting image helps to solve a mystery that has been puzzling scientists for almost 100 years – the origin of cosmic rays. Cosmic rays are extremely energetic particles that continually bombard the Earth, thousands of them passing through our bodies every day. The production of gamma rays in this supernova shock wave tells us that it is acting like a giant particle accelerator in space, and thus a likely source of the cosmic rays in our galaxy.

Dr Paula Chadwick of the University of Durham said “This picture really is a big step forward for gamma-ray astronomy and the supernova remnant is a fascinating object. If you had gamma-ray eyes and were in the Southern Hemisphere, you could see a large, brightly glowing ring in the sky every night.”

Professor Ian Halliday, CEO of PPARC which funds UK participation in HESS said “These results provide the first unequivocal proof that supernovae are capable of producing large quantities of galactic cosmic rays – something we have long suspected, but never been able to confirm.”

Gamma rays are the most penetrating form of radiation we know, around a billion times more energetic than the X-rays produced by a hospital X-ray machine. This makes it very difficult to use them to create an image – they just pass straight through any surface which we might use to reflect them, for instance. However, luckily for life on Earth, gamma rays from objects in outer space are stopped by the atmosphere; when this happens, a faint flash of blue light is produced, lasting for a few billionths of a second. The astronomers used images of these flashes of light, called Cherenkov radiation, to make a gamma ray ‘image’ for the first time.

Original Source: PPARC News Release

Image credit: University of Chicago
The big bang could be a normal event in the natural evolution of the universe that will happen repeatedly over incredibly vast time scales as the universe expands, empties out and cools off, according to two University of Chicago physicists.

?We like to say that the big bang is nothing special in the history of our universe,? said Sean Carroll, an Assistant Professor in Physics at the University of Chicago. Carroll and University of Chicago graduate student Jennifer Chen will electronically publish a paper describing their ideas at http://arxiv.org/.

Carroll and Chen?s research addresses two ambitious questions: why does time flow in only one direction, and could the big bang have arisen from an energy fluctuation in empty space that conforms to the known laws of physics?

The question about the arrow of time has vexed physicists for a century because ?for the most part the fundamental laws of physics don?t distinguish between past and future. They?re time-symmetric,? Carroll said.

And closely bound to the issue of time is the concept of entropy, a measure of disorder in the universe. As physicist Ludwig Boltzmann showed a century ago, entropy naturally increases with time. ?You can turn an egg into an omelet, but not an omelet into an egg,? Carroll said.

But the mystery remains as to why entropy was low in the universe to begin with. The difficulty of that question has long bothered scientists, who most often simply leave it as a puzzle to answer in the future.

Carroll and Chen have made an attempt to answer it now.

Previous researchers have approached questions about the big bang with the assumption that entropy in the universe is finite. Carroll and Chen take the opposite approach. ?We?re postulating that the entropy of the universe is infinite. It could always increase,? Chen said.

To successfully explain why the universe looks as it does today, both approaches must accommodate a process called inflation, which is an extension of the big bang theory. Astrophysicists invented inflation theory so that they could explain the universe as it appears today. According to inflation, the universe underwent a period of massive expansion in a fraction of a second after the big bang.

But there?s a problem with that scenario: a ?skeleton in the closet,? Carroll said. To begin inflation, the universe would have encompassed a microscopically tiny patch in an extremely unlikely configuration, not what scientists would expect from a randomly chosen initial condition. Carroll and Chen argue that a generic initial condition is actually likely to resemble cold, empty space?not an obviously favorable starting point for the onset of inflation.

In a universe of finite entropy, some scientists have proposed that a random fluctuation could trigger inflation. This, however, would require the molecules of the universe to fluctuate from a high-entropy state into one of low entropy?a statistical longshot.

?The conditions necessary for inflation are not that easy to start,? Carroll said. ?There?s an argument that it?s easier just to have our universe appear from a random fluctuation than to have inflation begin from a random fluctuation.?

Carroll and Chen?s scenario of infinite entropy is inspired by the finding in 1998 that the universe will expand forever because of a mysterious force called ?dark energy.? Under these conditions, the natural configuration of the universe is one that is almost empty. ?In our current universe, the entropy is growing and the universe is expanding and becoming emptier,? Carroll said.

But even empty space has faint traces of energy that fluctuate on the subatomic scale. As suggested previously by Jaume Garriga of Universitat Autonoma de Barcelona and Alexander Vilenkin of Tufts University, these flucuations can generate their own big bangs in tiny areas of the universe, widely separated in time and space. Carroll and Chen extend this idea in dramatic fashion, suggesting that inflation could start ?in reverse? in the distant past of our universe, so that time could appear to run backwards (from our perspective) to observers far in our past.

Regardless of the direction they run in, the new universes created in these big bangs will continue the process of increasing entropy. In this never-ending cycle, the universe never achieves equilibrium. If it did achieve equilibrium, nothing would ever happen. There would be no arrow of time.

?There?s no state you can go to that is maximal entropy. You can always increase the entropy more by creating a new universe and allowing it to expand and cool off,? Carroll explained.

Original Source: University of Chicago News Release

A planetary conjunction occurs when two or more planets appear to be very close together in the night sky as seen from Earth. Conjunctions between Venus and Jupiter are fairly common, occurring as often as three times a year. But on the morning of November 5th, just before dawn, Venus and Jupiter will be less than one degree apart in the sky in the constellation of Virgo the Maiden. A degree is about the width of one finger held at arms distance. The pair will be at their closest at 1:58 UTC on the 5th, when they are 33 arc-minutes apart, or about 0.42 degrees.

This year’s conjunction is rare for two reasons. First, the two planets are less than one degree apart; and second, they are more than fifteen degrees from the sun. Large number conjunctions, such as the one that occurred in 1995, are less than fifteen degrees from the sun and therefore lost in the sun’s glare. The conjunction on November 5th is also special because it is the last close conjunction between Venus and Jupiter until September 1st 2005.

A conjunction very much like the one occurring on the 5th occurred in August of the year 3 B.C. This historic conjunction occurred on August 12th at 03:00 UTC and was widely visible from the Middle East. That year Venus and Jupiter were only 10 arc-minutes or 0.16 degrees apart in the constellation of Leo the Lion. With such a narrow separation, light reflected from the two would seem to merge into one as seen with the unaided eye.

Some scholars have speculated that this close conjunction may have been interpreted as a sign by a group known as the Magi. The Magi, or wise men, were priests of an ancient religion known as Zoroastrianism. Could this close conjunction have been what sent the wise men traveling to a far of city known as Bethlehem? Unfortunately we can’t draw any definitive conclusions. There are no known written records that tell exactly what the Magi saw, or how they interpreted it.

Regardless of what the Magi saw, modern computer software confirms that there was a very close conjunction between Venus and Jupiter in the year 3 B.C. The conjunction of 2004, while not as close, should be no less spectacular sight in the sky. Telescope or binocular users should have no difficulty fitting both planets into one field of view. This conjunction is also an excellent opportunity for aspiring (or seasoned) astro-photographers.

Exposures of from 1/15s to 1/60s are good for those using SLR’s with standard 50mm lenses. A zoom lens of 180mm can reduce the required shutter speed to a range of 1/60s to 1/250s depending on conditions. But as with any kind of astro-photography, the key is multiple exposures at various shutter speeds and apertures.

A planetary conjunction is a rare and beautiful sight. Because Venus and Jupiter are both so bright in the sky, the Venus-Jupiter conjunction of 2004 should not be missed. With a little imagination we can transport ourselves back in time to the Middle Eastern Skies before the Common Era, when a bright conjunction dominated the pre-dawn skies.

Rod Kennedy is a technician and education outreach coordinator at the Casper Planetarium, Wyoming’s first planetarium. He received his Chemistry degree from the University of Northern Colorado, and has been interested in astronomy for 10 years.