Posted on by Fraser Cain

Book Review: Bad Astronomy by Phil Plait

Astronomer Phil Plait has found a great niche for himself – debunking bad science, specifically Bad Astronomy. He’s been at it on the web for years, and it came as no surprise to me when I found out there was a book deal in the works.

Astronomer Phil Plait has found a great niche for himself – debunking bad science, specifically Bad Astronomy. He’s been at it on the web for years, and it came as no surprise to me when I found out there was a book deal in the works.

Bad Astronomy: Misconceptions and Misuses Revealed, from Astrology to the Moon Landing “Hoax” is exactly what it sounds like. For 260ish pages Phil takes a look at many of the common misconceptions that have plagued astronomy for years.

The first half of the book is interesting reading, but it’s more of a science book. Phil looks at many of the commonly misunderstood concepts in astronomy and sets the record straight. I’d like to think I know a little about astronomy, so I was pretty surprised to learn I was misinformed about many aspects of the basics: tides, meteors, gravity.

It’s in the second half of the book where Plait really hits his stride as he examines some of the “bad astronomy” hatched more recently: Apollo moon landing hoaxes, UFOs etc. Because the culprits are still spinning out the bad science, Phil firmly debunks their “theories”. I especially enjoyed the Top Ten Examples of Bad Astronomy in Hollywood.

If I had a complaint, it’s that Phil spends a little too much time explaining how to balance an egg in any season (a whole chapter!, but I guess he was trying to make a point). Seriously, though, it’s a great book, not Bad Astronomy at all.

Click here to find out more from Amazon.com.

Fraser Cain
Publisher, Universe Today

Posted on by Fraser Cain

When Galaxies Collide

Image credit: Chandra

A new image taken by the Chandra X-Ray Observatory has provided one of the best views of two galaxies similar to our own Milky Way in the midst of a collision. All galaxies, including our own, have gone through this kind of merger in the past, so this image helps astronomers understand how the Universe came to look like it does today. The galaxies began their slow collision 10-million years ago and have already created regions of intense star formation and may eventually create a supermassive black hole.

NASA’s Chandra X-ray Observatory has provided the best X-ray image yet of two Milky Way-like galaxies in the midst of a head-on collision. Since all galaxies – including our own – may have undergone mergers, this provides insight into how the universe came to look as it does today.

Astronomers believe the mega-merger in the galaxy known as Arp 220 triggered the formation of huge numbers of new stars, sent shock waves rumbling through intergalactic space, and could possibly lead to the formation of a supermassive black hole in the center of the new conglomerate galaxy. The Chandra data also suggest that merger of these two galaxies began only 10 million years ago, a short time in astronomical terms.

“The Chandra observations show that things really get messed up when two galaxies run into each other at full speed,” said David Clements of the Imperial College, London, one of the team members involved in the study. “The event affects everything from the formation of massive black holes to the dispersal of heavy elements into the universe.”

Arp 220 is considered to be a prototype for understanding what conditions were like in the early universe, when massive galaxies and supermassive black holes were presumably formed by numerous galaxy collisions. At a relatively nearby distance of about 250 million light years, Arp 220 is the closest example of an “ultra-luminous” galaxy, one that gives off a trillion times as much radiation as our Sun.

The Chandra image shows a bright central region at the waist of a glowing, hour-glass-shaped cloud of multimillion-degree gas. Rushing out of the galaxy at hundreds of thousands of miles per hour, the super-heated as forms a “superwind,” thought to be due to explosive activity generated by the formation of hundreds of millions of new stars.

Farther out, spanning a distance of 75,000 light years, are giant lobes of hot gas that could be galactic remnants flung into intergalactic space by the early impact of the collision. Whether the lobes will continue to expand into space or fall back into Arp 220 is unknown.

The center of Arp 220 is of particular interest. Chandra observations allowed astronomers to pinpoint an X-ray source at the exact location of the nucleus of one of the pre-merger galaxies. Another fainter X-ray source nearby may coincide with the nucleus of the other galaxy remnant. The X-ray power output of these point-like sources is greater than expected for stellar black holes accreting from companion stars. The authors suggest that these sources could be due to supermassive black holes at the centers of the merging galaxies.

These two remnant sources are relatively weak, and provide strong evidence to support the theory that the extraordinary luminosity of Arp 220 – about a hundred times that of our Milky Way galaxy – is due to the rapid rate of star formation and not to an active, supermassive black hole in the center.

However, in a few hundred million years, this balance of power may change. The two massive black holes could merge to produce a central supermassive black hole. This new arrangement could cause much more gas to fall into the central black hole, creating a power source equal to or greater than that due to star formation.

“The unusual concentration of X-ray sources in the very center of Arp 220 suggests that we could be observing the early stages of the creation of a supermassive black hole and the eventual rise to power of an active galactic nucleus,” said Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, another member of the team studying Arp 220.

Clements and McDowell were joined on this research by an international group of researchers from the United States, United Kingdom and Spain. Chandra observed Arp 220 on June 24, 2000, for approximately 56,000 seconds using the Advanced CCD Imaging Spectrometer (ACIS) instrument.

ACIS was developed for NASA by Pennsylvania State University, University Park, PA, and the Massachusetts Institute of Technology, Cambridge, MA. NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program, and TRW, Inc., Redondo Beach, Calif., is the prime contractor. The Smithsonian’s Chandra X-ray Center controls science and flight operations from Cambridge, Mass.

Posted on by Fraser Cain

ESA Plans Another Look at the Moon

The European Space Agency is working on a new spacecraft that will visit the Moon and map its surface in great detail. The SMART-1, due for launch in 2003 will arrive at the Moon and begin a detailed analysis of the surface from different angles, in regular light, infrared and X-ray and then produce a three-dimensional map. Smart-1 will visit the dark southern pole of the Moon for the first time and help investigate areas which have never been touched by the Sun.

Posted on by Fraser Cain

NASA Approves Shuttleworth’s Visit

NASA has given its blessing for millionaire space tourist Mark Shuttleworth to visit the International Space Station. The previous paying visitor, Dennis Tito, was permitted into the station, but required constant supervision. Shuttleworth will lift off Thursday on board a Russian Soyuz rocket from the Baikonur cosmodrome in Kazakhstan and dock with the station Saturday.

Posted on by Fraser Cain

Hubble Helps with New Measurement for Universe’s Age

Image credit: Hubble

Thanks to the Hubble Space Telescope, astronomers are using ancient stars in the Milky Way to come up with an independent estimate about the age of the Universe. In the past, astronomers have calculated this age using its rate of expansion, and pegged it between 13-14 billion years old. Under this new method, the astronomers targeted ancient white dwarf stars which cool down at a very predictable rate. These stars were formed near the beginning of the Universe, and the astronomers were able to estimate that they are between 12-13 billion years old. Close enough.

Pushing the limits of its powerful vision, NASA’s Hubble Space Telescope has uncovered the oldest burned-out stars in our Milky Way Galaxy. These extremely old, dim “clockwork stars” provide a completely independent reading on the age of the universe without relying on measurements of the expansion of the universe.

The ancient white dwarf stars, as seen by Hubble, turn out to be 12 to 13 billion years old. Because earlier Hubble observations show that the first stars formed less than 1 billion years after the universe’s birth in the big bang, finding the oldest stars puts astronomers well within arm’s reach of calculating the absolute age of the universe.

Though previous Hubble research sets the age of the universe at 13 to 14 billion years based on the rate of expansion of space, the universe’s birthday is such a fundamental and profound value that astronomers have long sought other age-dating techniques to cross-check their conclusions. “This new observation short-circuits getting to the age question, and offers a completely independent way of pinning down that value,” says Harvey Richer of the University of British Columbia, Canada.

The new age-dating observations were done by Richer and colleagues by using Hubble to go hunting for elusive ancient stars hidden inside a globular star cluster located 5,600 light-years away in the constellation Scorpius. The results are to be published in the Astrophysical Journal Letters.

Conceptually, the new age-dating observation is as elegantly simple as estimating how long ago a campfire was burning by measuring the temperature of the smoldering coals. For Hubble, the “coals” are white dwarf stars, the burned out remnants of the earliest stars that formed in our galaxy.

Hot, dense spheres of carbon “ash” left behind by the long-dead star’s nuclear furnace, white dwarfs cool down at a predictable rate ? the older the dwarf, the cooler it is, making it a perfect “clock” that has been ticking for almost as long as the universe has existed.

This approach has been recognized as more reliable than age-dating the oldest stars still burning by nuclear fusion, which relies on complex models and calculations about how a star burns its nuclear fuel and ages. White dwarfs are easier to age-date because they are simply cooling, but the trick has always been finding the dimmest and hence longest-running “clocks.”

As white dwarfs cool they grow fainter, and this required that Hubble take many snapshots of the ancient globular star cluster M4. The observations amounted to nearly eight days of exposure time over a 67-day period. This allowed for even fainter dwarfs to become visible, until at last the coolest ? and oldest ? dwarfs were seen. These stars are so feeble (at 30th magnitude ? which is considerably fainter than originally anticipated for any Hubble telescope imaging with the original cameras), they are less than one-billionth the apparent brightness of the faintest stars that can be seen by the naked eye.

Globular clusters are the first pioneer settlers of the Milky Way. Many coalesced to build the hub of our galaxy and formed billions of years before the appearance of the Milky Way’s magnificent pinwheel disk (as further confirmed by Richer’s observations). Today 150 globular clusters survive in the galactic halo. The globular cluster M4 was selected because it is the nearest to Earth, so the intrinsically feeblest white dwarfs are still apparently bright enough to be picked out by Hubble.

In 1928, Edwin Hubble’s measurements of galaxies made him realize that the universe was uniformly expanding, which meant the universe had a finite age that could be estimated by mathematically “running the expansion backward.” Edwin Hubble first estimated the universe was only 2 billion years old. Uncertainties over the true expansion rate led to a spirited debate in the late 1970s, with estimates ranging from 8 billion to 18 billion years. Estimates of the ages of the oldest normal “main-sequence” stars were at odds with the lower value, since stars could not be older than the universe itself.

In 1997 Hubble astronomers broke this impasse by triumphantly announcing a reliable age for the universe, calculated from a very precise measurement of the expansion rate. The picture soon got more complicated when astronomers using Hubble and ground-based observatories discovered the universe was not expanding at a constant rate, but accelerating due to an unknown repulsive force termed “dark energy.” When dark energy is factored into the universe’s expansion history, astronomers arrive at an age for the universe of 13-14 billion years. This age is now independently verified by the ages of the “clockwork” white dwarfs measured by Hubble.

Original Source: Hubble News Release

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Survey Confirms Dark Energy Theories

Image credit: Hubble

Recent evidence seems to indicate that the expansion of the Universe is actually accelerating – some kind of “dark energy” is pushing it apart. And a new redshift survey of galactic clusters seems to support this. Astronomers using data gathered by the Chandra X-Ray Observatory have determined that there is insufficient matter (both regular and dark matter) in various galactic clusters to account for their shape and position, so something else must be having an effect.

The universe appears to be permeated with an invisible force ? dark energy ? that is pushing it apart faster and faster. By conducting redshift surveys of galaxy clusters, astronomers hope to learn more about this mysterious force, and about the structure and geometry of the universe.

“Galaxy clusters consist of thousands of galaxies gravitationally bound into huge structures,” said Joseph Mohr, a professor of astronomy at the University of Illinois. “Because of the expansion of the universe, the clusters appear denser at larger redshifts, when the universe was younger and denser.”

Galaxy cluster surveys that probe the high-redshift universe can potentially provide a wealth of information about the amount and nature of both dark matter and dark energy, said Mohr, who will present the results of an ongoing study of galaxy clusters at a meeting of the American Physical Society, to be held in Albuquerque, N.M., April 20-23.

“Till now, galaxy clusters have only been used to study the dark matter component of the universe,” Mohr said. “We would measure the total mass in a galaxy cluster, and then determine the fraction of mass that was ordinary, baryonic matter.”

Those measurements have shown there is insufficient baryonic and dark matter to account for the geometry of the universe. Astronomers now believe the universe is expanding at ever-increasing speed, and is dominated by a mysterious dark energy that must be doing the pushing.

“The next step is to try to figure out some of the specifics of the dark energy, such as its equation of state,” Mohr said. “By mapping the redshift distribution of galaxy clusters, we should be able to measure the equation of state of dark energy, which would provide some important clues to what it is and how it came to be.”

Mohr is using data collected by NASA’s Chandra X-ray Observatory to study scaling relations ? such as the relationship between mass and luminosity or size ? of galaxy clusters and how they change with redshift. “These scaling relations are expected to evolve with redshift, reflecting the increasing density of the universe at earlier times,” Mohr said.

In particular, Mohr ? in collaboration with John Carlstrom at the University of Chicago and scientists at the University of California and Harvard Smithsonian Center for Astrophysics ? is studying the effect that hot electrons within galaxy clusters have on the cosmic microwave background, the afterglow of the big bang.

Galaxy clusters are filled with dark matter, galaxies and hot gas. Electrons in the gas scatter off the protons and produce X-rays. The emission of X-rays diminishes with higher redshift, because of the larger distances involved.

“There also is a tendency for the electrons to give some of their energy to the photons of the cosmic microwave background, which causes the blackbody spectrum to shift slightly,” Mohr said. “The resulting distortion ? called the Sunyaev-Zeldovich effect ? appears as a cold spot on the cosmic microwave background at certain frequencies. Because this is a distortion in the spectrum, however, it doesn’t dim with distance like X-rays.”

By comparing the X-ray emission and the Sunyaev-Zeldovich effect, Mohr can study even faint, high-redshift galaxy clusters that are currently inaccessible by other means. Such measurements, correlating galaxy cluster redshift distribution, structure and spatial distribution, should determine the equation of state of dark energy and, therefore, help define the essence of dark energy.

“Within the context of our standard structure formation scenario, galaxy surveys provide measurements of the geometry of the universe and the nature of the dark matter and dark energy,” Mohr said. “But, to properly interpret these surveys, we must first understand how the structure of galaxy clusters are changing as we look backward in time.”

Original Source: UIUC News Release

Posted on by Fraser Cain

Star Formation Exposed

Image credit: Chandra

A new photograph taken by the Chandra X-Ray Observatory shows a close up view of the dynamics of star formation in the Tarantula Nebula (aka 30 Doradus). This region, located 160,000 light years away is one of the most active star forming regions in our local group of galaxies and provides a lot of clues to astronomers. In this region, astronomers have identified at least 11 extremely massive stars with ages of only 2 million years with many more young stars packed together so tightly individual stars can’t be resolved.

The Chandra image of the Tarantula Nebula gives scientists a close-up view of the drama of star formation and evolution. The Tarantula, also known as 30 Doradus, is in one of the most active star-forming regions in our Local Group of galaxies. Massive stars are producing intense radiation and searing winds of multimillion-degree gas that carve out gigantic super-bubbles in the surrounding gas. Other massive stars have raced through their evolution and exploded catastrophically as supernovas, leaving behind pulsars and expanding remnants that trigger the collapse of giant clouds of dust and gas to form new generations of stars.

30 Doradus is located about 180,000 light years from Earth in the Large Magellanic Cloud, a satellite galaxy of our Milky Way Galaxy. It allows astronomers to study the details of starbursts – episodes of extremely prolific star formation that play an important role in the evolution of galaxies.

At least 11 extremely massive stars with ages of about 2 million years are detected in the bright star cluster in the center of the primary image (left panel). This crowded region contains many more stars whose X-ray emission is unresolved. The brightest source in this region known as Melnick 34, a 130 solar-mass star located slightly to the lower left of center. On the lower right of this panel is the supernova remnant N157B, with its central pulsar.

Two off-axis ACIS-S chips (right panel) were used to expand the field of view. They show SNR N157C, possibly a large shell-like supernova remnant or a wind-blown bubble created by OB stars. Supernova 1987A is also visible just above and to the right of the Honeycomb Nebula at the bottom center.

In the image, lower energy X-rays appear red, medium energy green and high-energy are blue.

Original Source: Chandra News Release

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Second Space Tourist Ready to Go

South African Mark Shuttleworth is all set to blast off in a Russian Soyuz rocket on Thursday. If all goes well, the Soyuz will lift off from the Baikonur cosmodrome in Kazakhstan and carry Shuttleworth, cosmonaut Yuri Gidzenko and Italian Roberto Vittori up to the International Space Station, where they will spend the next 10 days performing a series of experiments. It’s rumoured that the space tourist paid $20 million US for the flight.

Posted on by Fraser Cain

Older Quasars a Source of Cosmic Rays

Image credit: NASA

NASA astronomers believe that retired quasars may be a source of rare, high-energy cosmic rays. They’ve identified four elliptical galaxies relatively nearby that contain massive black holes. If these black holes are spinning, they could be a source of ultra high-energy cosmic rays. The source of cosmic rays is a mystery, but astronomers have calculated that they must come from objects within 200 million light years from the Earth – these “retired quasars” could be the source.

They are old but not forgotten. Nearby “retired” quasar galaxies, billions of years past their glory days as the brightest beacons in the Universe, may be the current source of rare, high-energy cosmic rays, the fastest-moving bits of matter known and whose origin has been a long-standing mystery, according to scientists at NASA and Princeton University.

The scientists have identified four elliptical galaxies that may have started this second career of cosmic-ray production, all located above the handle of the Big Dipper and visible with backyard telescopes. Each contains a central black hole of at least 100 million solar masses that, if spinning, could form a colossal battery sending atomic particles, like sparks, shooting off towards Earth at near light speed.

These findings are discussed today in a press conference at the joint meeting of the American Physical Society and the High Energy Astrophysics Division of the American Astronomical Society in Albuquerque, N.M. The team includes Dr. Diego Torres of Princeton University and Drs. Elihu Boldt, Timothy Hamilton and Michael Loewenstein of NASA’s Goddard Space Flight Center in Greenbelt, Md.

Quasar galaxies are thousands of times brighter than ordinary galaxies, fueled by a central black hole swallowing copious amounts of interstellar gas. In galaxies with so-called quasar remnants, the black hole nucleus is no longer a strong source of radiation.

“Some quasar remnants might not be so lifeless after all, keeping busy in their later years,” said Torres. “For the first time, we see the hint of a possible connection between the arrival directions of ultra-high energy cosmic rays and locations on the sky of nearby dormant galaxies hosting supermassive black holes.”

Ultra high-energy cosmic rays represent one of astrophysics’ greatest mysteries. Each cosmic ray — essentially a single sub-atomic particle such as a proton traveling just shy of light speed — packs as much energy as a major league baseball pitch, over 40 million trillion electron volts. (The rest energy of a proton is about a billion electron volts.) The particles’ source must be within 200 million light years of Earth, for cosmic rays from beyond this distance would lose energy as they traveled through the murk of the cosmic microwave radiation pervading the Universe. There is considerable uncertainty, however, over what kinds of objects within 200 million light years could generate such energetic particles.

“The very fact that these four giant elliptical galaxies are apparently inactive makes them viable candidates for generating ultra high-energy cosmic rays,” said Boldt. Drenching radiation from an active quasar would dampen cosmic-ray acceleration, sapping most of their energy, Boldt said.

The team concedes it cannot determine if the black holes in these galaxies are spinning, a basic requirement for a compact dynamo to accelerate ultra-high energy cosmic rays. Yet scientists have confirmed the existence of at least one spinning supermassive black hole, announced in October 2001. The prevailing theory is that supermassive black holes spin up as they accrete matter, absorbing orbital energy from the infalling matter.

Ultra-high-energy cosmic rays are detected by ground-based observatories, such as the Akeno Giant Air Shower Array near Yamanashi, Japan. They are extremely rare, striking the Earth’s atmosphere at a rate about one per square kilometer per decade. Construction is underway for the Auger Observatory, which will cover 3,000 square kilometers (1,160 square miles) on an elevated plain in western Argentina. A proposed NASA mission called OWL (Orbiting Wide-angle Light-collectors) would detect the highest-energy cosmic rays by looking down on the atmosphere from space.

Loewenstein joins NASA Goddard’s Laboratory for High Energy Astrophysics as a research associate with the University of Maryland, College Park. Hamilton, also a member of the Lab, is a National Research Council fellow.

Original Source: NASA News Release

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Atlantis Returns to Florida

The space shuttle Atlantis touched down at NASA’s Kennedy Space Center on Friday completing an 11-day mission to upgrade the International Space Station. During their time in orbit, the seven shuttle astronauts completed 4 spacewalks and installed over $1 billion in equipment, including a 13.5 ton metal beam which will serve as the backbone for future modules on the station. Astronaut Jerry Ross made history with this flight, becoming the first person to go into space seven times.