So, What Do Astronomers Do With A 55 Meter-Long Image?

The new 55-meter image that was unveiled today is impressive, but does it hold any scientific value? A resounding yes to that question came from astronomers who helped work on this project, and given the standing room only for the oral presentation of the scientific research going into this image, plenty of other astronomers are interested in the discoveries from Spitzer’s five-year effort of gathering infrared data of our home galaxy. “This is a legacy science project,” said Barbara Whitney of the Space Science Institute, “that shows star formation as never seen before on both the large and small scale. Most of these star forming regions are being seen for the first time.”

“This is the highest-resolution, largest, most sensitive infrared picture ever taken of our Milky Way,” said Sean Carey of NASA’s Spitzer Science Center. “Where previous surveys saw a single source of light, we now see a cluster of stars. With this data, we can learn how massive stars form, map galactic spiral arms and make a better estimate of our galaxy’s star-formation rate,” Carey explained.

From our vantage point on Earth, we see the Milky Way as a blurry, narrow band of light that stretches across the sky. In the visible, we only see about 5% of what’s actually out there. But with Spitzer’s dust-piercing infrared eyes, astronomers have peered 60,000 light-years away into this fuzzy band, called the galactic plane, and saw all the way to the other side of the galaxy.

The result is a cosmic tapestry depicting an epic coming-of-age tale for stars.

While evolved stars are seen as blue, the star forming regions are seen as green. The regions where young stars reside are revealed as “bubbles,” or curved ridges in the green clouds. These bubbles are carved by the winds from the outflow of dust from the young stellar objects. The starlets appear as yellow and red dots, and wisps of red are dust particles.

“With these Spitzer data, we’ve been able to catalogue more than 100 million stars,” said Edward Churchwell of the University of Wisconsin, at Madison.

“This picture shows us that our Milky Way galaxy is a crowded and dynamic place. We have a lot to learn. I’ve definitely found a lot of things in this map that I didn’t expect to see,” said Carey.

How Cold is Mars?

Mars Polar Ice Cap. Image credit: NASA/JPL

How cold is Mars? Now, that is a fine question. The average temperature across the Martian surface is -63 C. Parts of Mars have been known to drop as low as -123 C. There are two main reasons that Mars is colder than Earth: it is farther from the Sun and it has an atmosphere that is too thin to retain heat.

The Martian atmosphere contains greenhouse gases that would cause a much warmer surface if the planet had the gravity and magnetic field that would allow it to hold onto gases. What little atmosphere(only 1% as thick as Earth’s) that clings to Mars is 95.32% carbon dioxide. As we know from experience here on Earth, higher amounts of CO2 cause higher temperatures. We call it a greenhouse gas and blame global warming on the increase in these gases. If Mars could hold its carbon dioxide content, there would be runaway global warming across the planet.

The gravity on Mars is only 38% as strong as it is here on Earth. That low gravity allows many of the gases needed to retain heat close to the surface to escape into space. The core of the planet is thought to be solid. Without a spinning, molten core Mars is unable to generate a magnetic field. Without a magnetic field, the solar wind and radiation constantly bombard the Martian atmosphere, blowing away another portion of the gases needed to heat the planet.

There is evidence that Mars has not always been a frigid planet. Some probe instruments on the Mars Express suggest that at one time Mars was warm enough to support liquid water. A radar instrument has found water ice, a mineral mapping instrument discovered chemicals only formed in a wet environment, and a camera has shown features formed by running water. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) has probed down to thousands of meters finding water ice along the way. The OMEGA Visible and Infrared Mineralogical Mapping Spectrometer has detected clay-like minerals that form during long-term exposure to water, sulphates(a mineral that forms when water evaporates), and ferric oxide. Each indicate the long term presence of liquid water on the surface. Images from the High Resolution Stereo Camera(HRSC) show features that could only be formed by erosion from flowing water.

The quick answer to ”how cold is Mars?” is -63 C on average. If you look into the contributing factors of that temperature, you must also look into the planet’s past. Some scientists think that Mars could have been a lush jungle like planet if it had not lost its atmosphere.

How cold is Mars? Read this article and learn that Mars is REALLY cold. And evidence that Mars has been cold for billions of years.

More information on Mars is available Hubblesite’s News Releases about Mars. Here’s an article from Space.com about how microbes can survive cold temperatures, maybe even some day on Mars.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

Sources:
NASA Solar System Exploration Guide
NASA Mars Fact Sheet

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

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.

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

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.)

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

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.

2006 Arctic Mars Analogue Svalbard Expedition (Jake Maule)

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

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…

The classical Kristian Birkeland experiment in 1902 (from The Norwegian Aurora Polaris Expedition 1902-1903, Volume 1)
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