December 17, 2017

02.05.10- Star-birth in the Early Universe.

Astronomers are shedding new light across the spectrum on an old cosmological mystery. It’s well documented that the rate of star formation today is much less than what it was early on in the history of the universe; what isn’t completely understood is why. Was there simply an abundance of star forming material available, or was the process of star formation more efficient? Either trend may have a huge significance as to how the current and future evolution of the universe plays out; stars such as our Sun are metal rich and formed as a result of the recycling of cosmic material from that first primeval generation of stars. Even non-fusion sustaining bodies such as the Earth, Sandra Bullock, and your IPad owe their elemental composition largely to those original stars.  Now, a team led by Michael Cooper of the University of Arizona’s Steward Observatory is tackling the dilemma from a fresh angle. The galaxies in question are about 4 billion years old; the universe is an estimated 13.7 billion years of age. In that tender young era, the rate of observed star formation was about 10 times what we see today. Traditional surveys have looked at larger, brighter, and more easily observable galaxies in the energetic throes of star formation. But is that the best approach? This method largely ignores the vast population of fainter, harder to spot galaxies. “It is a little like studying only individuals who are seven feet tall instead of those who fall in a more common range of height,” stated Cooper. Their unique approach has been to examine a selection of average galaxies culled from 50,000 objects to study across a range of wavelengths. Instruments called into action included the Hubble and Spitzer Space telescopes as well as an array of ground-based radio telescopes. Analysis across the spectrum shows that a much greater concentration of gas and dust was available to fuel star formation than what we see today; these galaxies also really light up in the radio and infrared, as pictured above… could we be looking at snapshots resembling our galaxies’ grandparents?

24.04.10-Our Existence: Justified.

The formation of the Earth poses a key dilemma to planetary accretionary theory; namely, why are we here at all? Standard models would say that the Earth and other planets coalesced out of the proto-solar nebula to form. However, spiral density waves within the same nebula should have drawn down orbital energy to shorten the planets orbit, slowly drawing it in. Looking at other “hot Jupiter” systems, that’s just what we see; large gas giant worlds that formed further out, only to migrate inward into tight orbits… just how did we end up in our nice, neat orbit?

Now, computational astrophysicist Mordecai-Mark Mac Loc at the American Museum of Natural History may have the answer. Accounting for temperature and spin variability, resonance key holes can occur; planets like Earth may simply spiral inward and get hung up in these safe zones between dragging pressure waves. Of course, a majority of proto-planets don’t make the cut and simply spiral inward to a fiery end, but they’re not around for us to see today. One discovery that would perhaps give observational weight to this theory would be the discovery of exo-Earths also parked in nice neat orbits… the Kepler space telescope may pave the way for this discovery as it stares off into Cygnus. For now, thank computational mathematics that you’re here reading this, just as it says you should be!

23.04.10-SDO Unveiled.

Cool images Alert: NASA’s recently launched Solar Dynamics Observatory (SDO) has released some fairly mind-blowing pics and videos this week. The video below is but a small sampling of the capabilities showcased by this Sun-monitoring spacecraft. “We’ve seen prominences before, but not like this!” states Alan Title of Lockheed Martin. SDO was launched on February 11th, 2010 and studies the Sun from a polar inclined geosynchronous orbit. Equipped with high definition cameras and a 4096x 4096 –pixel array, you haven’t seen the Sun the way SDO has revealed it. Part of NASA’s Living With a Star program, SDO will provide a continuum in solar astronomy started by the ESA’s SOHO satellite in the 1990’s. One can only hope that SDO’s data will be as easily accessible and provide real time access to the public as SOHO has done. Not only will SDO have the capability to monitor the Sun in ultraviolet and extreme ultraviolet, but it also possesses an Atmospheric Imaging Assembly (AIA) and a Helioseismic and Magnetic Imager. But beyond pretty pictures, SDO also promises to give us a unique insight into the inner workings of our Sun. And with sunspot cycle #24 just gearing up, this capability may have come none too soon!

Review: The Five Ages of the Universe by Fred Adams and Greg Laughlin.

This week, we’re going to look at a classic book on cosmology that is both fascinating and frightening. About 10 years ago, I read the Five Ages of the Universe by Fred Adams and Greg Laughlin.  This book built upon information gathered in the swiftly growing field of cosmology, a science that has just come into its own from one largely of late night philosophy to one of hard science with real observational data. Five Ages does nothing short of trace the history of the universe from its first moments to its logical end, or lack thereof. The discovery that we appear to live in an open universe that will indeed expand ad infinitum holds some very bizarre and disconcerting conclusions, all of which the authors explore in vivid detail using the most up-to-date data available. It’s strange to think that we may occupy a tiny sliver of space and time where life can occur, and a vast, infinite stretch of nothing may be in store. However, the authors are careful to make every attempt to abandon their own human bias towards the current era, and instead look at subsequent epochs on their own terms.

When dealing with a topic as expansive as the history and fate of the universe, one has to become accustomed to discussing extremely large numbers. Creationists aside, we live in a universe that is about 13.7 billion years old, give or take about 100 million years. But that is peanuts compared to the gargantuan timescales discussed in this book. Instead, the authors resort to what are termed cosmological decades, (henceforth called CDs) exponential scales where each decade is ten times longer than the last. Thus we are said to exist at the very beginning of the 10th decade, or 1010, which began 3.7 billion years ago and will last until decade 11 over 96 billion years from now. And trust me, the time scales just get larger from there…

The first era covered is termed the primordial epoch, from the moment time and space began until CD 6. During this time of rapid inflation matter coalesced via nucleosythesis, the cosmic microwave background separated out the cooling universe, and the first stars began to shine.

The next era explored is our own, termed the stelliferous era. This is the time we see today and are most familiar with. Stars shine via fusion, galaxies collide, and the processes that power life that is possible to contemplate the wonder of it all and write books (and blogs about books!) is possible. During this period, which is expected to last up until about CD 15, stars will pass through their life cycle until the universe is littered with white dwarfs, pulsars, and black holes. Miserly red dwarf stars, with an expected fusion producing life span of up to about 10 trillion years are expected to be the last stars to go. Then the universe gets really weird…

From CD 15-40 we enter what is known as the degenerate era, a time when white dwarfs turn black, protons decay, and dark matter annihilates the galactic halo. Perhaps an occasional brown dwarf pair will merge in this far-off time and an old school star will shine briefly in the void. But by CD 40, the start of the black hole era, only the stellar remnants of black holes will remain. Even these are anticipated to decay via the process of Hawking radiation with even one million solar mass monsters dissipating after around CD 83. Axions are also predicted to decay into photons at about this time.

Of course, what happens during the final dark era of about CD100 on is highly speculative. Will time itself cease to exist? Will quantum fluctuations randomly spout new universes? Will a sort of cosmological phase transition reconstruct our present universe? Keep in mind, long before this time, the edge of the observable universe will have expanded to a mindboggling point, as if it’s not brain blowing big enough now. In fact, the distance between whatever passes for individual particles in the far off dark era will be larger than the observable universe today!

Read The Five Ages of the Universe to gain a cosmic perspective on the consequences of just what living in an infinite universe might mean. Each chapter also opens with an engaging “you are there” narrative to help gain a perspective on these alien realms through the forces propelling the universe through its transitions. Perhaps I would first read Stephen Hawkings’ landmark A Brief History of Time to provide some background, and then follow up Ages with Douglas Adams Hitch-hikers Guide to the Galaxy as a way to cheer oneself up as to the inevitability of it all!

 

21.04.10-The Puzzle of Blue Stragglers.

Astronomers may have recently solved a half a century long mystery of stellar evolution. Since the 1950’s a type of star known as  a blue straggler has stubbornly refused to fit the Hertzsprung-Russell diagram mold. These older stars should be approaching seniority, but instead burn brightly and spin energetically as if they had somehow gained mass. Most exist in globular or open clusters, and were first identified in the M3 globular cluster. The most well studied example of this stellar sub-class exist in NGC 188, a star cluster about 6,000 light years distant where 21 have been identified. Now, astronomers Robert Mathieu and Aaron Geller of the University of Wisconsin Madison have gained insight into the formation of these elusive beasties and come up with three leading hypotheses;

  1. Matter is accreted from an aging red giant star onto a main sequence companion similar to the process seen in a type IA supernova, but not as massive, causing the star to re-energize;
  2. Two lower mass stars collide, an improbable but not impossible scenario in a densely packed globular cluster;
  3. A third stellar companion perturbs the orbit of a tightly knit binary pair, causing them to merge.

These possibilities were advanced after Mathieu and Geller used observing time on the 3.5-meter WIYN telescope on Kitt Peak spanning the past decade. Studies involved NGC 188, the original “blue straggler” cluster. “These aren’t just normal stars that are straggling behind in their evolution,” stated Mathieu.” There is something unusual going on with their companions.” Computer models would suggest that door number #3 is the most likely candidate; the most logical proof that astronomers would like to have in hand would be to catch a merger in progress.  Interestingly, two known blue stragglers with white dwarf companions lie in the field of the Kepler space telescope, a plus for the accretionary camp. Will we soon have definitive evidence for the origins of these bizarre stars? Or is it perhaps a hybrid of the three models? Stay tuned…

Review: The Big Bang Theory.

In astronomical circles we’ve all met the guy who has memorized Pi to the nth degree, or can recite the periodic table backwards or knows every star in the Big Dipper by obscure Arabic name. Or perhaps you are that guy, with your atomic Green Lantern watch synchronized to both Universal and Local time and you’re reading this wondering; “so what? Everyone else I know is equally socially handicapped…”

[Read more...]

04.04.10-Fermi: Einstein Still Rules.

We just can’t seem to get enough of NASA’s Fermi Gamma-Ray Space Telescope. The successor to the late Compton observatory that was de-orbited in 2002, Fermi has already pinpointed over 1,000 discrete gamma-ray sources, five times more than previously known. Now Fermi has also provided a rare test of Einstein’s theories of relativity. Relativity says that all electromagnetic waves (including highly energetic gamma-rays) travel through space at the same cosmic speed of 186,282 miles per second. Being a classical theory, however, what Einstein doesn’t do is meld gravity satisfactorily with the other three fundamental forces; electromagnetism and the strong and weak nuclear forces. Gravity stubbornly refuses to be unified, and such a goal has been the holy grail of physics for over the last half century. An alternative model of gravity at the microscopic scale would say that the nature of space-time is “frothy,” and a predicted effect should be a measureable drag induced on high energy photons. Recently, Fermi had a chance to put this to the test; on May 10th of last year, GRB 090510, a short gamma-ray burst 7.3 billion light years distant, was measured by Fermi’s Large Area Telescope. The verdict; gamma-ray photons varying a by a factor of a million times in energy arrived just nine-tenths of a second apart, far below what would be predicted by “frothy” space… that’s round one for Einstein!

02.04.10- Cassiopeia A: A Quark Star?

The supernova remnant Cassiopeia A holds a compelling astrophysical mystery. Located about 10,000 light years away, this strong radio source was identified in 1947 and remains the most recent galactic supernova known. One slightly odd fact revolves around Cas A; despite its having burst about 325 years ago as seen from Earth, no reliable records exist of the event. Evidence of the event may have been obscured by intervening galactic dust.  Some intriguing indications show that John Flamsteed may have misidentified the supernova as a sixth magnitude star in Cassiopeia during one of his surveys, but now Cas A may be the home of a even more bizarre denizen; a quark star. This theory stems from the fact that the remnant host appears to be only 10 km across, smaller than your average neutron star. At that density, neutrons loose all individual identity and merge into a huge ball of quark strange matter, a “strange” object indeed. First spotted by the Chandra X-Ray observatory in 1999, this “quark star” would be the first of its kind. Of course, an alternative hypothesis, put forth by Wynn Ho and Craig Heinke of Southampton University, states that we’re merely seeing a normal neutron star of about 25 km in diameter shining through a carbon atom haze. Does astrophysics need to get any weirder?

27.03.10- Modeling Black Holes.

Researchers are calling in the big guns in the quest to understanding black holes. Specifically, scientists at the Rochester Institute of Technology are using time on some of the fastest and most powerful computers in use to model and predict the activity of super massive black holes. But these aren’t your ordinary off the shelf PCs; their laboratory New Horizons machine is a computer cluster of 85 nodes with 4 processors that is capable of passing data at a rate of 10 gigabytes per second. Try that on your family Mac book! Further grants totaling $2.9 million will enable the team to hone their theoretical models over the next 3 years on ever faster machines. “It’s a thrilling time to study black holes, ” states center director Manuela Campanelli. If predictions match observations, these models may also serve as the best proof yet of Einstein’s General Theory of Relativity…more to come!

20.03.10: Spying a Black Hole Welterweight.

Astronomers now have observational evidence for a missing class of black hole. Stellar mass black holes, those up to about 10 solar masses, are well known as the remnants of supernovae. Likewise for supermassive black holes of 10,000 solar masses or greater known to reside in the hearts of galaxies like our own. The “missing link” in astrophysics has been intermediate mass black holes, or those between 100 and 10,000 solar masses. Now, scientists at the Goddard Space Flight Center in Greenbelt Maryland have used the XMM-Newton and Swift X-ray satellites to pinpoint a likely candidate; NGC 5408 X-1, a black hole with about 1,000 to 9,000 solar masses in a galaxy about 15.8 million light years away in the constellation Centaurus. This would include an event horizon about 3,800 to 34,000 miles across. An X-ray flux occurs once every 115.5 days, strongly suggesting that NGC 5408 X-1 has a stellar companion accreting donor material. This star would be 3-5 times the Sun’s mass.   “Astronomers have been studying NGC 5408 X-1… because it’s one of the best candidates for an intermediate mass black hole.” States Philip Kaaret of the University of Iowa. The contributing companion also gives astronomers the unique opportunity to probe the near-space environment as well as study this intermediate class of enigmatic objects.

02.02.10 In Search of Life, Gravity Waves, and Everything.

Astronomers have added a key tool to their arsenal in probing the very early universe. LIGO, the Laser Interferometer Gravitational wave Observatory, is a pair of “observatories” one in Hanford, Washington, and one in Livingston, Louisiana that monitor the universe for that most exotic of beasts; gravity waves. Each L-shaped detector is comprised of two 2.25 mile long arms and by monitoring the minute changes in length as measured by laser beam, LIGO can detect changes as small as 1/1,000th of the width of an atomic nucleus.   By comparing the measurements from the two observatories and its sister companion, a European detector known as Virgo, directional magnitude of cosmic gravity waves can be measured. LIGO saw first “gravity light” in 2002. Late last year, data was released comprising two years’ worth of observations, and a sort of “all-sky map” in gravity waves is emerging. Unlike microwave energy, which can only probe the universe back to an age of about 380,000 years old, gravity waves were generated just moments after the Big Bang, and promise to paint a picture of that youthful era of our universe. LIGO may also prove to be one of the very few testable platforms for string theory, a theory that is very much in need of observational data. And be sure to keep an eye out in 2014 for Advanced LIGO, a detector to go online with 10x the present accuracy… can’t wait? YOU can join the citizen science brigade in the hunt for gravity waves before bedtime; checkout Einstein@home!

06.11.09:A New Type of Supernova?

Astronomers at  the University of California at Berkley may have added a new type of supernova to the list. Typical type I supernovae consist of a carbon-oxygen white dwarf accreting matter from a companion star until a runaway reaction occurs, while type II supernovae involve a collapse of a star perhaps nine times as massive as our Sun. Recently, astronomers uncovered evidence that an extragalactic supernova previously classified as a type II may in fact deserve a class of its own. Named SN 2002bj, this exploding star exhibited the characteristics of a garden variety nova, such as the brief flare up of in-falling hydrogen, but created an explosion 1,000 times more massive. In the case of SN 2002bj, however, the flash also had a conspicuous absence of hydrogen, with instead a strong helium flash and the presence of vanadium in its spectra, a first for a supernova. Theoretical models suggest that this may have been a binary white dwarf pair, with one feeding the other a steady flow of helium until it reached the collapse limit and burst. Also, unlike typical type Ia supernovae, the white dwarf involved survived the explosion. Another unusual signature to this supernova was the way it rapidly faded from sight in about 20 days, about four times faster than usual. SN 2002bj is located in the galaxy NGC 1821 and was spotted in February 2002. Does the classification of supernovae need tweaking?

25.10.09: In Search of a Mirror Universe.

There is one enduring mystery in cosmology that just won’t budge; namely, just what happened to all that pesky anti-matter that was presumably created during the Big Bang? Was it annihilated, only to leave the infinitesimally small faction of pedestrian “normal” baryonic matter that comprises the universe that we know and love, or are there still areas that antimatter predominates? Now, cosmologists are getting their wish in the form of the Alpha Magnetic Spectrometer (AMS), due to launch aboard the last shuttle flight and bound for the International Space Station late next year. Once installed, AMS will search the entire sky with an unprecedented accuracy looking for ultra-high energy cosmic rays in the form of anti-helium nuclei. Antimatter looks and behaves just like normal matter…except when it meets up with its mirror cousin. If you meet your anti-matter twin on the road, don’t shake hands with him or her, our you’ll both vanish in a flash of pure energy conversion Ala E=mc^2! The AMS will also look for such exotica as dark matter, micro-quasars, and strangelets, a proposed new form of matter. And that’s just the stuff we know about! I smell a possible Nobel in the works…are you reading this, CERN? The AMS has been an on-again, off-again payload that Congress just green-lighted last year. The AMS promises to reveal a big old, bizarre universe out there. With a sensitivity 200 times anything that’s flown previous, AMS should conclusively prove or disprove the potential existence of any lurking antimatter galaxies out to a radius of 100 mega-parsecs. Like CERN, AMS will also generate terabytes of data to keep astrophysicists awake nights, and will be a fitting end to the shuttle fleets’ career!

 

 

11.10.09: Zooming in on Blazars.

Astronomers have recently utilized an enormous radio telescope to examine some of the most exotic objects in the universe; active galactic nuclei. Sometimes called “Blazars”, these distant galaxies are spewing huge jets of particles at amazing relativistic speeds. These emit immense energy across the electromagnetic spectrum. NASA’s Fermi Gamma Ray Space Telescope has identified and monitored these sources since its launch in 2008 and now scientists at the Max Planck Institute for Radio Astronomy have used the National Science Foundation’s Very Long Baseline Array (VLBA) to map these jets with unprecedented accuracy. The VLBA is a series of 10 interlinked radio telescopes spanning an area from the Virgin Islands to Hawaii that utilize interferometry to produce an effective baseline of 5,300 miles and can resolve details less than 100 light years across at a distance of 7 billion light years. Fermi, the predecessor to the Compton Gamma Ray Observatory that was de-orbited in 2000, scans the entire sky once every three hours looking for gamma-ray bursts. First spotted in the early 70′s during global monitoring of nuclear weapons tests, pinning down gamma-ray bursts has been the name of the game in astrophysics over the past decades. The backup study proves the link between the gamma-ray emissions seen by Fermi and the energetic radio jets pinpointed by the VLBA… expect more high resolution radio maps to come!

4.10.9:A Gamma-Ray Burst for the Record Books.

A Gamma-ray burst from the primordial universe sent astronomers reeling earlier this year with the most distant sighting yet. The burst was picked up by NASA’s Swift spacecraft on April 23, 2009 at 3:55 EDT. E-mails and instant messages flew to observatories around the globe as astronomers raced to pin-point the fading afterglow. Dubbed GRB 090423, (get the year/month/day thing?) This burst measures in at a redshift of 8.2, or a distance of 13.035 billion light years. This hails from a time when the universe was a tender young age of only 630 years old, young, compared to our circa 14 billion year current age. The old record was a red shift of 6.7 set in September 2008. the current “holy grail” in cosmology is to break the “redshift 10″ barrier, which may well happen in the coming year. A gamma-ray burst occurs when a super massive star collapses into a black hole, briefly creating a “hyper-nova” in the process. Such events are the most luminous in the universe and are thought to have been common amoung first generation stars. Backup observations were provided by Italy’s Galileo national telescope in the Canary Islands and the ESO’s Very Large Telescope in Chile.

29.9.9:Hubble Spies a Galactic Jet.

The formerly ailing Hubble Space Telescope spied something remarkable earlier this year; a rapidly expanding jet around the massive galaxy M87. Dubbed HST-1, this blob of matter is the first object with a Hubble designation, and has been tracked for over seven years. Brighter than the galaxies’ own core, the gas knot is 214 light years from the core and receding. M87 is visible in the constellation Virgo with a backyard telescope, and is part of the massive Virgo cluster of galaxies about 54 million light years away. The growth of the brightness of the jet expanded by 90 fold over the past decade, giving astronomers the opportunity to examine an active galactic nucleus in action. As the refurbished Hubble begins to strut its stuff, doubtless HST-1 will be an object of increased scrutiny!

Review: Blast! A Film by Paul Devlin.

Blast! Can be seen as a documentary that was 13.7 billion years in the making. Directed by Paul Devlin, Blast! follows the exploits of a group of astrophysicists as they break new ground with a unique balloon borne telescope. BLAST stands for Balloon-Borne, Large Aperture Sub-millimeter Telescope. As reported earlier this week in our post “Antarctic Astronomy”, “Sub-millimeter” is the name loosely given to the wavelengths roughly between microwave and infra-red. [Read more...]

Review: Bang!

 

 

Think hard rock and astrophysics don’t mix? Think again. Recently, we had the pleasure of reading Bang! The Complete History of the Universe,” by astronomy heavyweights Brian May, Patrick Moore, and Chris Lincott… [Read more...]