Universe Today

June 3, 2008December 24, 2015 by Fraser Cain

The Milky Way Has Only Two Spiral Arms

If you were stuck inside your house, you’d never know what it looks like from the outside. That’s the situation with the Milky Way. We’re inside it, so we don’t really know what its structure looks like. There are other examples of grand spirals that we can see, but this is like seeing other houses outside your window; you just can’t be sure. Astronomers have developed a detailed map of the Milky Way, and realized that they were giving our home galaxy too many arms; it’s only got 2, and not 4 like astronomers originally thought.

The new revelation was made possible thanks to NASA’s Spitzer Space Telescope, which sees in the infrared spectrum, and can peer though the gas and dust that obscures the plane of the Milky Way.

Previous maps of the Milky Way were first developed in the 1950s, when astronomers used radio telescopes to trace out the spiral arms of our home galaxy. They focused on gas clouds, and revealed what they thought were 4 major star-forming arms: Norma, Scutum-Centaurus, Sagittarius and Perseus.

We live in minor arm called the Orion Arm, or the Orion Spur, located between the Sagittarius and Perseus Arms.

And then in 2005, astronomers used infrared telescopes to pierce through the clouds of gas and dust to see that the central bar in the middle of the Milky Way extends much further than previously believed.

In a new survey by Spitzer, astronomers merged together 800,000 photographs containing over 110 million stars. Software counted up the number of stars and measured their density.

As expected, astronomers found an increase in density in stars towards the Scutum-Centaurus Arm, but no increase towards the Sagittarius and Norma arms. The Perseus arm wraps around the outer portion of our galaxy and can’t be seen in the Spitzer images.

This helps make the case that the Milky Way only has two spiral arms; a commonly seen situation where a galaxy has a long central bar.

Original Source: NASA/JPL News Release

June 3, 2008December 24, 2015 by Astronomy Cast

Podcast: The Search for Water on Mars

With the successful touchdown of the Phoenix Lander, NASA is continuing its quest to find evidence of past and present water on Mars. This week we discuss the geologic history of Mars, and explain why NASA thinks the story of water on Mars is so important. And how this ties into the search for life on the Red Planet.

Click here to download the episode

The Search for Water on Mars – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

June 3, 2008December 24, 2015 by Fraser Cain

The Case of the Missing White Dwarf

Despite their name, planetary nebulae have nothing to do with planets. They’re created when stars like our Sun enter the last stages of life, and puff off their outer layers. Then they shrink down to become a white dwarf star. This must have happened in the case of planetary nebula SuWt 2, located about 6,500 light-years away from Earth. Except there’s a problem: the white dwarf remnant has gone missing. The Hubble Space Telescope has been called in to help in the search, but so far, nothing has turned up.

The case of the missing white dwarf was announced today at the 212th meeting of the American Astronomical Society by astronomers from the Space Telescope Science Institute in Baltimore, and other British and American colleagues.

With most planetary nebulae, there are beautiful and delicate rings; the remnants puffed off by the dying star. There should also be a white dwarf star shining in the middle of the nebula.

At the center of SuWt 2, there two tightly bound stars orbiting one another in just 5 days – neither of these are white dwarfs. Both are hotter than our own Sun, but they’re not hot enough to actually make the nebula glow. To get the nebula as bright as it is, you need a bright source of ultraviolet radiation coming from a white dwarf. Once again… where did it go?

All the evidence points towards that binary pair of stars orbiting within the nebula. The astronomers think that there used to be three stars orbiting one another. The most massive star evolved into a red giant, which temporarily engulfed the other two stars. Trapped inside the red giant’s envelope, they slowed down and spiraled inward.

The spiraling stars caused the red giant’s envelope to spin up so fast that the outer layers were ejected into space, causing the beautiful rings of debris we see today. This might also help explain why the two stars are rotating more slowly than expected.

The exposed core of the red giant might have blasted out ultraviolet radiation that caused the nebula to glow. And then shortly after that, the red giant shrunk down to become a dim white dwarf – one that’s too faint to be detected, even by Hubble.

Original Source: Hubble News Release

June 3, 2008December 24, 2015 by Nancy Atkinson

Largest Picture of the Milky Way Unveiled

The Milky Way is a large place, and getting all the stars together, even from just the inner galaxy, for a family photo requires a big canvas. The imaging team from the Spitzer Space Telescope today unveiled the largest, highest resolution infrared picture ever taken of the Milky Way. The photo spans 55 meters (180 feet), and takes up almost one entire wall in the huge exhibit hall here at the AAS meeting in St. Louis (above.) The image is made of 800,000 snapshots taken by Spitzer, amassing 39,000 X 6000 pixels, and shows an area of sky 120 degrees longitude by 2 degrees latitude. It provides 100 times better angular resolution than any previous survey and is 100 times more sensitive. There’s also an online version….

This “chops” up the image into five strips, and certainly isn’t as impressive as the 55 meter version! However, there’s another, more spectacular way to view this spectacular image. The GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) Image Viewer provides a great way to view and browse this image. The viewer boasts the following tagline: “One spacecraft, 5 infrared bands, 800,000 images, 4 billion pixels of data.” It lets you scan the image with both the IRAC (Infrared Array Camera) on Spitzer, or the MIPS (Multiband Imaging Photometer.)

June 3, 2008March 29, 2013 by Nancy Atkinson

Watch Press Conferences on Astronomy Cast LIVE

UPDATE: NEW LINK for Noon conference
Wish you were here? Join us today from the AAS meeting in St. Louis. We’ll be live-streaming video of the press conferences on the Astronomy Cast UStream channel. You can participate via chat if you go to the link above, or watch it live below.

Today’s Press Conference schedule (all times CDT):
9:40 am: Weird Binary Stars
12:00pm: The Milky Way

Also, Pamela’s session at 10:00 am will be available live: Round Table: Connecting Local and National New Media Programs in the IYA 2009.

Live Videos provided by Ustream.TV

June 2, 2008December 24, 2015 by Ian O'Neill

Mars Settlement Pioneers Will Face Huge Psychological Challenges

Artist impression of an astronaut on Mars (NASA)

Imagine you are on the crew of a Mars mission and you fall out with a fellow crew member. You can’t walk away from them. Imagine you are on the surface of Mars and you suffer terrible home sickness. You can’t simply fly back to your family. Imagine there is a medical emergency in your team en-route to the Red Planet. You can’t call emergency services, you’re on your own. These issues with long-period missions into space, especially on future missions to colonize Mars, could cause serious psychological issues and may jeopardise the mission. Many groups are currently working on understanding how humans could react in these situations when they are isolated and confined so far away from home, and “Mars Analogues” based here on Earth are proving to be very useful…

It may seem obvious that it is going to be mentally (let alone physically) tough for future astronauts on the first manned missions to Mars, but space organizations (like NASA and ESA) and voluntary groups such as the Mars Society are gaining a valuable insight to how we function when restricted to very confined spaces with only a handful of people for company. Mars settlement mock-ups known as “Mars analogue environments” based in locations like the Utah Desert or the Arctic island of Spitsbergen are extremely valuable to mission planners when researching how to live and work on the Martian surface. However, they are also proving to be very influential when selecting crew members who will spend all of their time together. This psychological factor may be key to the future of Mars missions that could last years.

Plans are afoot for a long 520-day mock Mars mission this year to study the effects isolation has on a group of 12 volunteers. The study is being carried out by ESA and the Russian Institute of Biomedical Problems so psychological issues can be identified and understood. It is work like this on Earth that will influence the selection of astronauts to be sent to Mars who are compatible in a work and social environment.

A lot of research has been done on astronauts ever since Yuri Gagarin was launched into orbit alone in 1961. Before Gagarin’s historic journey, doctors were very concerned that weightlessness may cause acute mental disorders such as schizophrenia. Fortunately, this was not to be the case, but there are many disorders we cannot fully test until man ventures far into interplanetary space.

It seems natural that Mars astronauts will want gifts, luxuries and other “reminders from home”, as is possible on the International Space Station, but they will be totally isolated with no ferrying of items when they leave the safety of Earth. This need can be subdued by regular communications with home (although a 40+ minute delay for communications between Earth and Mars will make any “live” conversation impossible), and generally we know the problems we’ll face should these “homesick” feelings surface.

But what happens when man loses sight of Earth? Dr. Nick Kanas, who has studied astronaut psychology at UC San Francisco, is concerned about this unknown factor. He has even given this situation a name: the “Earth out of view” phenomenon.

“Nobody in the history of mankind has ever experienced the Earth as a pale, insignificant blue dot in the sky. What that might do to a crew member, nobody knows.” – Dr. Nick Kanas.

This is the nature of the task in hand, humans are going to be pushed beyond what we would consider to be a “natural” situation. Perhaps we might surprise ourselves and find that space exploration is as natural to us as it was for our ancestors to discover new continents. In fact, many astronaut psychologists are looking back into the history books to gain an insight as to what it was like for early pioneers of global exploration.

“When early explorers left their home countries on the seas, they didn’t see their home countries anymore. They didn’t even have a dot to look at. It was out of sight on the other side of the world. It is not like we are reinventing the wheel. We are just doing the same thing in a different environment that was just as demanding then.” – Walter Sipes, NASA psychologist, Johnson Space Center, Houston.

These factors combined with space euphoria and the “Overview Effect”, our future Mars astronauts are possibly in for a bumpy psychological ride…

Source: CNN

June 2, 2008December 24, 2015 by Ian O'Neill

How do you Model the Earth’s Magnetic Field? Build your own Baby Planet…

The model Earth, can a magnetic field be modelled in the lab? (Flora Lichtman, NPR)

The Earth’s magnetic field is quite a mystery. How is it generated? How does it remain so stable? We have known of the Earth’s magnetic field for hundreds of years and the humble compass has been telling us the direction of magnetic North Pole since the 12th Century. Animals use it for navigation and we have grown dependent on its existence for the same reason. What’s more, the magnetosphere gives us a powerful shield against the worst solar storm. Yet we still have little idea about the mechanisms generating this field deep in the core of the Earth. In the hope of gaining a special insight to the large-scale, planetary magnetic field, a geophysicist from the University of Maryland has built his very own baby Earth in his laboratory, and it will be spinning (liquid metal included) by the end of the year…

This story reminds me of a classic experiment carried out by Norwegian Kristian Birkeland at the turn of the 19th Century. In an attempt to understand the dynamic Aurora Borealis (Northern Lights), Birkeland experimentally proved that electrical currents could flow along magnetic field lines (a.k.a. Birkeland, or “field-aligned” currents, pictured left). This can be observed in nature as charged particles from the solar wind interact with the Earth’s magnetosphere and are then guided down to the Earth’s magnetic poles. As the particles flow into the upper polar atmosphere, they collide with atmospheric gases, generating a colourful light display called aurorae. However, this early experiment simulated a magnetic field; it did not model how the Earth generates it in the first place.

Now, in a laboratory in the University of Maryland, geophysicist Dan Lathrop is pursuing this mystery by building his very own scale version of the Earth (pictured top). The model is set up on apparatus that will spin the 10-foot diameter ball to an equatorial speed of 80 miles per hour. To simulate the Earth’s molten outer core, Lathrop will fill the sphere with molten metal. The whole thing will weigh in at 26 tonnes.

This is Lathrop’s third attempt at generating a scale model of the Earth’s magnetic field. The last two attempts were much smaller, so this large experiment had to be constructed by a company more used to engineering heavy-duty industrial equipment.

It is believed that the Earth’s molten outer core, starting 2,000 miles below the Earth’s crust, generates the global magnetic field. This “dynamo effect” is somehow created through the interaction of turbulent liquid iron flow (which is highly conductive) with the spin of the planet. In Lathrop’s model, he will be using another conductive liquid metal, sodium. Molten iron is too hot to maintain in this environment, sodium exists at a liquid phase at far lower temperatures (it has a melting point close to that of the boiling point of water, nearly 100°C), but there are some serious hazards associated with using sodium as an iron analog. It is highly flammable in air and is highly reactive with water, so precautions will have to be taken (for one, the sprinkler system has been disabled, water in the case of a sodium fuelled fire will only make things worse!). This whole experiment, although risky, is required as there is no direct way to measure the conditions in the outer core of the Earth.

“The conditions of the core are more hostile than the surface of the sun. It’s as hot as the surface of the sun but under extremely high pressures. So there’s no way to probe it, no imaginable technique to directly probe the core.” – Dan Lathrop

Spinning this heavy sphere should cause sustained turbulence in the flow of the liquid sodium and it is hoped a magnetic field can be generated. There are many puzzles this experiment hopes to solve, such as the mechanics behind magnetic polar shift. Throughout the Earth’s history there is evidence that the magnetic poles have switched polarity, prolonged spinning of the model may cause periodic magnetic pole reversal. Testing the conditions in the conductive liquid metal may shed some light on what influences this global pattern of polar shift.

This kind of experiment has been done before, but scientists have directed the flow of liquid metal through the use of pipes, but this model will allow the metal to naturally organize itself, creating its own turbulent flow. Whether or not this test generates a magnetic field it is unknown, but it should aid our understanding about how magnetism is generated inside the planets.

See the video at National Public Radio »

Source: National Public Radio

June 2, 2008December 24, 2015 by Fraser Cain

Double Your Science: Starburst Galaxies Found with Active Quasars

Astronomers now know that essentially every galaxy has a supermassive black hole at its center. When the black hole is actively feeding on material, the surrounding region can blaze brightly – this is a quasar, aka an active galaxy. The Hubble Space Telescope has been used to image a set of exotic active galaxies, known as post-starburst quasars.

What’s the relationship between galaxies and their supermassive black holes? Astronomers have been trying to work that out since these monster black holes were first discovered. One theory is that the growth of both go hand in hand through successive galactic mergers. Each merger adds new stars to the galaxy, as well as additional mass to feed the black hole.

With the galactic mergers, there are intense periods of new star formation. Gravitational interactions collapse clouds of gas and dust that go on to form stellar nurseries. The new star formation is hidden in the beginning, but the active quasar at the middle of the galaxy blows with a powerful wind that eventually blows out the obscuring dust.

Starburst galaxies aren’t bright for long, because all the hottest, most-luminous stars only last a few million years before detonating as supernovae. Astronomers were hoping to see galaxies right in the middle, where starburst activity is fading, at the same time that the quasar is blasting out radiation.

One transition galaxy like this had been discovered in the late 1990s. It possessed both the characteristics of a quasar and an older starburst galaxy. At the time it was discovered, the starburst period had happened 400 million years ago – that’s why it’s a post-starburst galaxy.

An international team of researchers used the Hubble Space Telescope to find another 29 examples of these post-starburst quasars. They searched through a candidate list of 15,000 quasars, and found the signatures of 600 post-starburst objects. With ground-based telescopes, these would just be smudges, but the full galactic shapes can be seen in the Hubble images.

Our galaxy will be colliding with Andromeda in about 3 billion years. When this happens, the Milky Way will burst with star formation. One day, we’ll be living in a post-starburst galaxy.

Original Source: Hubble News Release

June 2, 2008December 24, 2015 by Nancy Atkinson

Re-use, Recycle and Share Your Spacecraft to Find Exoplanets

How do you get the most out of one spacecraft and find exoplanets in the process? Re-use, recycle and share. The spacecraft bus that brought the Deep Impact “impactor” to comet Tempel 1 in July of 2005 is still out in its heliocentric orbit and has been put to work double time where two new missions are sharing the same spacecraft. The combined operation is called EPOXI, which is a combo-acronym of the two separate missions. The Deep Impact Extended Investigation (DIXI) of comets will observe comet 103P/Hartley 2 during a close flyby in October 2010. But of current interest is the other half of the dynamic duo, called the Extrasolar Planet Observation and Characterization (EPOCh) which is observing stars already known to have transiting giant planets. Since the orbital plane of the giant planet has been identified, EPOCh is looking in that same plane for planets closer to Earth size. So far, 4 new planets have been found with this spacecraft, using the transit method. But EPOCh is also looking back at our home planet, using Earth as a baseline to be able to identify features on an exoplanet, such as continents and oceans.

The EPOXI team has focused most of its attention on the star GJ436. This red dwarf star which is 32 light-years from Earth has a Neptune-sized planet that transits in front of the star. Spitzer observations have shown its orbit to be oval shaped, or eccentric. “That virtually guarantees there is a second planet in this system,” said Drake Deming, Deputy Principal Investigator for EPOXI . “We have three weeks of data on this system. The habitable zone corresponds with where we believe this planet to be, and we hope to be below the Earth as far as the size.”

Earth observations will help to calibrate future observations of Earth-like exoplanets. EPOXI obtained a particularly interesting view of the Earth on May 29, when the Moon passed in front of the Earth as viewed from the spacecraft. This “transit” of the Moon is an event that may also be observed to occur for Earth-like exoplanets, and it may help us to deduce the nature of their surface features.

Deming and Deep Impact team leader Michael A’Hearn both said that sharing the spacecraft has gone smoothly. The EPOCh mission will continue until August 30 of this year, with the option of doing more planet searching if the team is able to preserve the margin of hydrazine fuel on board. “But,” said Deming, “when the hydrazine runs out we’re done for sure.”

Source: AAS press conference

June 2, 2008December 24, 2015 by Mark Mortimer

Book Review: Canada’s Fifty Years in Space – The COSPAR Anniversary

Technical ability signals a country’s advent into first world status. Amongst abilities, space travel sets the bar as paramount. Some nations with ready access to many people and large quantities of resources ascended and proclaimed their might. Other nations technical prowess came otherwise. Gordon Shepherd and Agnes Kruchio describe one such in their book “Canada’s Fifty Years in Space – The COSPAR Anniversary“. In it, they show that a nation’s limitations in people and resources doesn’t necessarily equate to a lack of technical ability or capability.

Canadians built the Alouette I satellite over a 4 year duration and saw it successfully launched in September 1962. Other than the US and the USSR, no other country had achieved such a feat. Yet, this wasn’t a one-of event. This satellite was a continuance of a Canadian specialty, the study of electron densities above the Earth. Following the launch, further studies added to the scientific knowledge of the aurora and the magnetic fields of the north. Expanding beyond this, Canadians have since studied life sciences and pushed the envelope in the field of robotics. Hence, even without an indigenous launch capability, Canada has made a positive impact in space science by carefully picking and choosing.

Shepherd and Kruchio’s book shows that Canadians have had a busy and productive 50 years in the field of space science. Their book starts with events a little bit earlier than in the title, with funding for studies being available in the early 1930s. Then, adventurers traveled into the cold Arctic winters to take timed exposures of Northern Lights. These stalwart types braved polar bears and isolation to gather the first organized review of one of nature’s most pleasant spectacles. But, their interest wasn’t all for pretty pictures. This book also shows their contributions were a true beginning into the study of the protective ionosphere about Earth. It also shows that as the years advanced, funding expanded. And, consequently, so did research. Rockets and balloons replaced ground-based photography. More people joined in. Yet, as becomes evident, the shear cost of doing research placed more and more restrictions on the scientists. With a fairly recent shift to remote sensing and astronauts, Canada now looks to fund applications of space science rather than delve in pure research. Thus, though barely two generations have passed, this book shows a busy past and a fundamental shift in one nation’s space research.

This book by Shepherd and Kruchio effectively brings together many aspects of Canada’s space science history. Vivid recollections recall the times of luminaries such as Dan Rose, Balfour Currie and Frank Davies. We read of programs that sprout from deep in the rooms of University of Saskatchewan, the launch pads at the Churchill Rocket Range and the laboratories at the DRTE. Devices such as ionosondes, interferometers and Lidar have brief technical descriptions and then a bit longer passage describing their use. Amongst all this data and information, the occasional reprints of some personal diary entries markedly and pleasantly contrast the otherwise dry prose.

As well as being dry, this book’s scope is another weakness. Typically a review of an expanding research field has more entries at the end than the beginning. This book, however, has most of its focus on the early and mid-term, when Canadians were studying the ionosphere. In comparison, the most recent science appears, briefly, toward the end and is like a collection of press releases. This, coupled with an out-of-place first chapter on COSPAR’s formation, detract from an otherwise intriguing review of science and scientists.

Yet, Canadian’s who are interested in knowing more of their country’s space accomplishments would enjoy this book. As well, industry watchers who wonder where some national organizations come from and go to might just get some answers within. And, anyone who thinks they’re too small to contribute could read this and get a great boost to their ego.

From so many perspectives, fifty years is an amazingly short time. But, in the field of science and technology, itâ€™s a vast duration. Gordon Shepherd and Agnes Kruchio’s book “Canada’s Fifty Years in Space – The COSPAR Anniversary” describe some of the scientific progress made by Canadians. With Canada and many more countries contributing to space science, the future years should see equal or greater accomplishments.