Pulsars are the strongly magnetised spinning cores of dead stars, each one just 20 kilometres across yet containing approximately 1.4 times the mass of the Sun.
Neutron stars are formed with temperatures of more than billion (1012 K) degrees during the collapse of massive stars. As soon as they are born they begin to cool down. How they cool must depend on the physical properties of the superdense matter inside them.
Picture with the x-ray spectrum taken of the pulsar in the crab nebula
Observations with previous X-ray satellites have shown that the X-rays from cooling neutron stars come from three regions of the pulsar:
• the whole surface is so hot that it emits X-rays.
• there are charged particles in the pulsar’s magnetic surroundings that also emit X-rays as they
move outwards, along the magnetic field lines.
• younger pulsars show X-ray hotspots at their poles.
Until now, astronomers accepted that hotspots are produced when the charged particles collide with the pulsar’s surface at the poles. However, the latest XMM-Newton results have cast doubt on this view. New data from ESA’s XMM-Newton X-ray observatory has shown that the prevailing theory of how pulsars generate their X-rays needs revising - the energy needed to generate the million-degree polar hotspots on cooling neutron stars may come from inside the pulsar, not from the collision of particles from outside the pulsar.
The lack of the polar hotspots in old pulsars is a big surprise and shows that the heating of the polar surface regions by particle bombardment is not efficient enough to produce a significant thermal X-ray component.
An international team of astronomers have recently performed one of the most detailed surveys of the most distant galaxies. These galaxies are so far away, we see them as they looked when the Universe was less than half its current age. One of the big surprises of this survey; however, is how much these young galaxies match the structures we see in the current Universe. This means that galaxies probably evolved through collisions and mergers much earlier than previously believed.
The Hubble ultra deep field shows many early galaxies
The knowledge of early galaxies has made major progress in the past ten years. Astronomers are using the new "Lyman-break technique" (combining ultraviolet and infrared measurements). This technique allows very distant galaxies to be detected. They are seen as they were when the Universe was much younger, thus providing clues to how galaxies formed and evolved. Stars in these distant galaxies (most are spiral galaxies) formed at a rate of a few hundred to one thousand stars per year (only a few stars currently form in our Galaxy each year). Up to now, distant galaxies were believed to be mainly interacting galaxies, with irregular and complex shapes. It has now been shown that these galaxies, seen when the Universe was about 40% of its current age, have regular shapes.
Brown dwarfs are too massive to be a planet and not massive enough to be a star. Brown dwarfs are sometimes called “failed stars”. They are too small to trigger the fusion of hydrogen that keeps stars like our sun shining for billions of years. Instead, over tens of millions of years brown dwarfs slowly cool and fade. To get a better "look" at brown dwarfs, scientists have been using infrared-capable telescopes and mathematical models. Over time, as the glowing body of a brown dwarf cools, metallic clouds form. The iron condenses to form iron-rich clouds and droplets of liquid-iron rain. While aging, brown dwarfs are releasing heat and should be getting more dim. However, astronomers found that the older brown dwarfs shined brighter than the warmer, younger ones. With cooling, a brown dwarf's cloud layer sinks closer to its surface. As the clouds form deeper in the atmosphere, they are more sensitive to the winds and convective motions in the atmosphere. This probably leads to the destruction of the clouds. But there are still many unanswered questions. For instance, what do these storms look like? Scientists predicts that in the next 10 to 15 years very large telescopes will exist, making it possible to gather more detailed information about these storms.
Discovered by The Spitzer Infrared Space Telescope
NASA's Spitzer Space Telescope has recently discovered potential solar systems surrounding two massive stars, 30 and 70 times the mass of our Sun. These two huge stars are circled by disks of what might be planet-forming dust. The disks surrounding these stars might contain massive quantities of icy material, similar to the Kuiper belt found in our own Solar System. Astronomers estimate that the stars' disks are spreading all the way out to an orbit about 60 times more distant than Pluto's around the Sun. The disks might represent theplanet-forming process. Stars as massive as these don't live very long. They burn through all of their nuclear fuel in only a few million years, and end up in fiery explosions called supernovae. Their short life spans don't leave much time for planet. Any planets that might crop up would probably be destroyed when the stars blast apart.
Observations and research from the Chandra x-ray observatory and other ground based telescopes suggest that astronomers have found a new type of supernova that until now has only existed theoretically. The supernova itself is the result of a massive star’s death, SN2006gy went out with a very a bang very different from what astronomers had originally thought.
Using the Hubble telescope researchers may have found what could be the most convincing evidence to date for the existence of dark matter; a theoretical elementary particle that pervades the universe.
The team turned Hubble’s camera on a cluster of galaxies 5 billion light years from earth classified as CI 0024+17 and what they found was both unexpected and unprecedented. Stretching 2.6 million light years across was a ring of dark matter that surrounds the cluster of galaxies, thought to be caused by the collision of two massive galactic clusters 1 to 2 billion years ago. Using computer simulations the team has determined that the ring could indeed be the result of such a collision that separated the normal matter in the cluster from the dark matter in the cluster.
One might ask how we can ever even know dark matter is out there. The answer, gravity! Though we can not directly detect dark matter, because it does not interact with light, we can see it though its gravitational effect. Called gravitational lensing the technique looks at the distortion of background galaxies caused by a lensing effect of the dark matter’s gravity, then by analyzing the distortion of light coming from these background galaxies the mass can be determined and thus the amount of dark matter.
The Wilkinson Microwave Anisotropy Probe or WMAP for short, is a NASA probe to detect and record the cosmic microwave background radiation that is still left over from the original energy of the big-bang. By using this probe they have been able to not only detect the backgrond radiation but they have been able to map it with a fair amount of accuracy, seeing the universe at a point in it's history when it was still very young. By mapping this they hope to help provide answers to some of the biggest questions about the origin and fate of our universe.
The resulting data map from the WMAP.
Blue sections show cooler areas where the matter in the universe first was able to collect.
The most comprehemsive map of the visible universe ever yet attempted.
The Sloan Digital Sky Survey or SDSS is a study dedicated to mapping the visible universe. Already it has a achieved a level never before reached. The dedicated telescope was automated and mapped out the tiny points of light that in most cases are stars and galaxies. It shows us undeniably that the universe is full of variety and beauty on a scale hard to understand.
A team of astronomers using the Subaru and Keck telescopes on Mauna Kea has discovered giant, three-dimensional filaments of galaxies extending across 200 million light-years of space - the largest-known structures ever discovered. The filaments containing large concentrations of gas (each up to ten times as massive as The Milky Way Galaxy) formed 2 billion years after the birth of the Universe. These giant gas clouds are probably the progenitors of the most massive galaxies that exist in the Universe today.
From the millenium simulation showing the filamentary structure; Image Credit: Max Planck Institute for Astrophysics
This finding gives new insight into the large-scale structure of the Universe. Astronomers expect the universe to look relatively smooth 2 billion years after the birth of the universe. In summarizing the importance of this finding, astronomer Ryosuke Yamauchi from Tohoku University said, “The structure we discovered and others like it are probably the precursors of the largest structures we see today which contain multiple clusters of galaxies.”
Until 1995 astronomers had concluded that there must be planets outside our solar system but had lacked the ability to observe them and therefore prove the hypothesis, but in 95’ the discovery of extra-solar planets rocked the astronomy world and over 200 have been found since, with the number almost assured to keep rising as technologies catch up to ideas.
The search for exoplanets, which just means planets outside our own solar system, has intrigued many an astronomer and there are now several projects dedicated to finding these treasured spheres. Most of the planets found so far are not like earth (terrestrial) but rather have much more in common with the gas giants found in our solar system. Called hot Jupiters, these most plentiful of planets found so far orbit very near their parent star and transit, or move across the star, in very short periods of time, most of them only days. This is partly because of the main method used to discover exoplanets, which is a method that looks at a star for either a dip in light from the spectrum of the star, which indicates a transiting planet or looks for a gravitational wobble from the host star. The second is caused by the mutual gravitation of a planet and its star, the planets gravity pulls on the star just a little and so the star wobbles back and forth. Astronomers are able to detect this wobble and thereby make calculations on the size of the planet causing it.
Though in many ways the search for exoplanets is in its infancy the development in the recent years and in the near future will enable astronomers to make more accurate observations of these bodies and find smaller and smaller worlds. The goal of many of these projects is to find another earth like planet. While there have been great discoveries of terrestrial planets that are much more massive than the earth astronomers still search for one that is near earth size.
The picture below was the first image of a planet outside our solar system, taken in the infrared it is a composite of multiple photos showing the parent star in blue and the planet in red.
First picture of an exoplanet taken by the European Southern Observatory
Since then the number of planets found has increased immensely and the most exciting discovery as of late is one made by a European team that has claimed to have found a terrestrial planet five times the mass of earth that is orbiting a red dwarf star. The star is much cooler then our own sun and the planet orbits much closer to it’s star then we do, but is none the less in the habitable zone of it’s solar system, which is the zone where water could be liquid. Called Gliese 581c the planet is being called the super earth and likely has twice the gravity of the earth. The exciting part about all this is that the team has discovered terrestrial planets orbiting a red dwarf which is the most common type of star in our galaxy and this one (Gliese) is one of the 100 closest stars to us. It is in astronomical terms fairly close to us, in our neighborhood if you will, but at 20.5 light years away it is still a monumental distance from earth. More research needs to be done and without speculating but the news of this newly found body is still very important because it increases the odds in many peoples minds that one day we will find another earth like planet.
Artist rendering of what gliese 581c might look like.
Image Credit: ESO
Astronomers using the Spitzer space telescope have developed the first map of an exoplanet's weather. The planet, designated as HD189733b, is located in the constellation Vulpecula and is the closest transiting planet to us, meaning that it passes in front of and behind its star from our line of sight. The planet is classified as a hot-Jupiter, which is a planet that orbits very close to its parent star and is a gas giant not unlike our own giant neighbor Jupiter.
Looking at the surface of this world through the infrared eyes of the Spitzer telescope the team was able to determine differences in the atmosphere. The temperatures ranges from about 650 degrees Celsius on the night side to around 930 Celsius on the day side, showing that the difference is fairly mild which the team thinks suggests that winds in the atmosphere must be responsible for distributing the heat from one side to the other. This conclusion is partly due to the idea that a planet this close to its star would be tidally locked with one side constantly facing the parent star, not unlike our moon.
The map developed of HD189733b
At around 60 light years away HD189733b is close in astronomical terms but still a great distance away in our own ideas of distance. The ability of the Spitzer team to determine these temperature variations and then create a map of them is nothing less than remarkable.
For more information on this topic and others relating to exoplanets visit the Spitzer Space Telescope website: http://www.spitzer.caltech.edu/
Celebrating its 17th year in operation Hubble has released an impressive image of a portion of the Carina Nebula 50 light years wide. The image shows a panorama of a region of star birth and death that is brilliantly illuminated and shaped by the energy of these massive stars.
Section of carina nebula
Deployed in 1990 this mechanical achievement was named for Edwin Hubble, an American astronomer who through observation discovered that the universe was expanding, supporting the big-bang theory. Throughout its many years in use the Hubble space telescope has provided us with an incredible amount of valuable data. Hubble has helped us to confirm many theories through observation. It has helped us to track and estimate the expansion rate of the universe, searched for and found the supper-massive black holes that lie at the center of galaxies, and provided us with stunning photos of the cosmos, like the ultra-deep field, an image that contains galaxies almost as old as the universe itself. When we look far, far out in the universe we are in effect looking back in time because the light has taken so long to get to us and the Hubble offers us a magnificent view of the past.
Above is a diagram of how the Hubble works and beside it is a picture of the famous Orion nebula taken by Hubble
Its mission was originally forecasted for five years but has now been extended to 10 years and this NASA telescope shows no signs of stopping.
Artist representation of Chandra in space
The Chandra x-ray observatory has allowed different scientists from around the world to observe the x-ray universe with a quality second to none. By using the images Chandra takes researchers hope to shed light on the evolution and structure of the universe.
Named for an Indian-American Nobel Laureate who did amazing work looking at the structure and evolution of stars and was one of the first astronomers to combine astronomy and physics in the sciences. Through this telescope there have been some impressive discoveries: the first observation of a black hole, explained the mystery of the spiral arms in galaxy NGC 4258, for the first time detected sound waves from a black hole and provided us with what may be the first conclusive evidence of dark matter; a mysterious matter that occupies most of the universe and is believed to be an unknown elementary particle. The discoveries of the Chandra are not only amazingly interesting but spectacularly breathtaking in showing the beauty of the unseen world of the x-ray.
Picture taken by Chandra of the spiral arms in galaxy NGC 4258
In August of 2003 NASA launched the last of its four great observatories; The Spitzer Space Telescope. Its mission was to search the universe in the infrared spectrum between wavelengths of 3 and 180 microns, which can only be done from space, outside the earth’s atmosphere. The Spitzer is the largest infrared telescope in space with a mirror of .85 meters and cryogenically cooled instruments. This infrared telescope has opened a world that visible light observation would never have yielded.
Infrared image of the center of our own galaxy
The Spitzer continues to return exciting information to the team at JPL/Caltech. It has seen what could be the light from the first star formations in the universe, inside proto-planetary disks to reveal details of how planets are made, found hundreds of examples of nascent solar systems and more recently have proven invaluable in the search for exoplanets, (planets outside our own solar system). Because it sees in the infrared the telescope can see through things that would normally be an obstacle for visible light observations, the wavelength of infrared radiation is such that it can travel long distances through things like gas and dust clouds giving us a window into a hidden world. Using spectrum data the team with the Spitzer was the 1st to measure the temperature difference on the day and night side of an exoplanet. As well they have analyzed the molecules of an exoplanet to determine that it had silicates in the high atmosphere. The ability of Spitzer to investigate exoplanets was one largely unforeseen but never the less has and will continue to reveal stunning finds.
Known as GALEX, the galaxy evolution explorer was the first mission to conduct a survey of the entire sky outside our home galaxy; an extra-galatic survey. In operation for over four years now GALEX surveys the sky in ultra violet light mapping out galaxies and looking at thier star forming regions. The observatory helps astronomers to look at the gas and dust of star formation and study its effects on the formation of galaxies. It looks at the star formation rates of galaxies and puts that data together with the UV properties of galaxies and develops a history of star formation across the cosmos, trying to fill in the gaps of our knowledge.
Above left; image of NGC55 in UV and on the right is an image of a star gluster called M2
