Universe Today

September 15, 2009December 24, 2015 by Jean Tate

Barred Spiral Galaxy

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As its name implies, a barred spiral galaxy is a spiral galaxy with a bar through the center.

Hubble introduced the ‘tuning fork’ scheme for describing the shapes of galaxies (“morphologies” in astronomer-speak) in 1936. In this, the two arms of the fork are barred spirals (from SBa to SBc) and spirals without bars (from Sa to Sc); the S stands for spiral, B for ‘it’s got a bar’, and a/b/c for how tightly wound the spiral arms are. This was later extended to a fourth type, SBm and Sm, for irregular barred spiral galaxies which have no bulge.

In 1959, Gérard de Vaucouleurs extended the scheme to the one perhaps the most commonly used by astronomers today (though there’ve been some mods since). In this scheme spirals without bars are SA, and those which have really weak bars are SAB; barred spirals remain SB. He also added a ‘d’ (SAd, SBd), and a few other things, like rings.

About half of spiral galaxies are barred; examples include M58 (SBc), M61 (SABbc), the Large Magellanic Cloud (LMC, Sm), … and our own Milky Way galaxy!

The bars are mostly stars (usually), unlike spiral arms (which have lots of gas and dust besides stars). The formation and evolution of bars is an active area of research in astronomy today; they seem to form from close encounters of the galaxy kind (galaxy near-collisions), funnel gas into the central bulge (where the super-massive black holes there snack on it), and are sustained by the same density waves which keep the arms alive.

Why not join the Galaxy Zoo project, and have some fun classifying spiral galaxies into whether they have bars or not (and getting to see some amazing sights too)?

Hubble Early Release Observation of Barred Spiral NGC 6217, Two Galaxies Walk Into a Bar…, and The Milky Way Has Only Two Spiral Arms; just some of the Universe Today stories on barred spiral galaxies.

Astronomy Casts featuring barred spiral galaxies include The Story of Galaxy Evolution, and Galaxies.

September 15, 2009December 24, 2015 by Fraser Cain

Satellite Map of the World

There’s no better way to appreciate the planet you live on than to have a great big picture of it on your wall. Here are some ways you can get your hands on a satellite map of the world.

If you’ve got a nice printer and you’d like to save yourself some money, why not download a satellite map of the world for free from NASA. You can get free satellite images from the NASA Earth Observatory.

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Each month NASA releases a new composite satellite image of the entire planet. This lets you track changes from month to month. You can view the full images on this page.

You can also get a free satellite map of the world captured at night. This photo shows whole planet Earth, but now you’re seeing it at night. The bright spots are cities and populated areas. It’s easy to see the differences between 1st world countries and more developing nations.

If you want to just buy a poster that you can put on your wall, you can find a bunch of satellite world maps from Amazon.com. Here’s a link to buy the Earth at night poster. And here’s an image of the whole Earth by day.

September 15, 2009December 24, 2015 by Nancy Atkinson

Astro Art: Artist Creates Portrait Gallery of Astronomers

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Art and astronomy often intersect, and it’s wonderful when art can provide an emotional connection to science. Amateur astronomer and artist Sayward Duffano has captured the personalities of several astronomers through history as well as individuals in astronomy related fields in a gallery of paintings she created especially for the International Year of Astronomy. “I knew I wanted to paint something special for the IYA,” she said. “So last year I had started painting a few astronomers, some planets, and some other types of astro art.”

And Sayward says she is looking for a place to display her work.

“Originally, I was working on a print and book project, but due to the recent downturn in the economy, those plans were not able to be realized,” she said. “I’m not trying to sell the originals, but I do want them to be able to be seen because of their subject matter and they were painted especially for the IYA.”

Andromedan Gothic. Painting by Sayward Duffano.

Her gallery includes astronomy notables like Galileo, Ptolemy, Cassini, Sagan and Levy and astronauts like Yuri Gagarin, Neil Armstrong, Christa McAuliffe, and even Laika the astro-dog. She also has a collection of the solar system and other astronomical objects, and a few humorous works, such as her “Andromedan Gothic” spoof, above.

She says she saw Vincent Van Gogh’s “Starry Night” when she was very young, and it inspired her to study art and created a bond with the night sky. “As time went on, I did more studying on the night sky and space, and realized it was a much bigger, more complex place than I had previously thought.

You can listen to Sayward talk about how astronomy has inspired art through the years on the Sept. 14 edition of 365 Days of Astronomy podcast.

After attending a star party a few years ago, she found the dark, unpolluted skies to be very inspiring. She began painting some Messier objects and some abstracts inspired by vintage copies of Sky and Telescope.

Astronaut Fred Haise with Sayward Duffano. Courtesy Sayward Duffano

In February of this year, she found out that Apollo 13 astronaut Fred Haise was coming to a nearby college campus in Long Beach, Mississippi. “I had painted his portrait, and wanted to give it to him,” she said. “It’s not every day (for me, at least!) I get to meet an astronaut. We went to his lecture, which was awesome, and afterward I gave it to him. He loved it.”

Sayward says she likes the abstractness of the moon and planetary surfaces. “Even the smallest craters and crevasses never fail to inspire, and the colors in space are always inspiring as well. The strange brightness of the sunny side of any planet reveals unusual earth tones, the vibrant oranges and yellows of Mars, the pale cream and contrasting red of Jupiter, the yellow ocher of Saturn, the icy greys of our Moon. They are vibrant, yet subdued in their own way.”

Sayward says she grinds many of her own paints and primarily work with Mars pigments. “I feel these colors are perfect for studying the planets via brush. There are reds, browns, yellows, oranges, violets, and black in the Mars color series, usually a light and dark of the same color. The pigment comes in powder form, and it is beautiful in itself. It’s like I’m mulling Martian soils.”

“Jupiter is probably my favorite planet,” she said. “I say probably because it’s almost a tie between it, Mars and Saturn. You have the cool rings around Saturn, and that strange, irresistible orange of Mars- but Jupiter is something else all together. It reminds me of a huge, ever changing marble.”

The astronomers, planets and other studies in this series of painting for IYA are all done on archivally sound recycled materials.

Any planetarium, science center or other place interested in displaying this collection can contact Sayward through her website, SaywardStudio.com.

September 15, 2009December 24, 2015 by Fraser Cain

International Space Station Pictures

International Space Station. Credit: NASA

With most of the construction of the International Space Station now complete, it’s quite an impressive sight to see. In fact, the space station is the brightest manmade object in space. It’s easy to see if you just know when and where to look. Check out our ISS tracking page with links to resources to find the station.

Here are some cool International Space Station pictures.

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This is a classic artist’s rendering of what the International Space Station will look like when all of its modules have been attached.

The International Space Station. Credit: NASA

And here’s another cool picture of the International Space Station.

Space station above the Earth. Image credit: NASA

Here’s a cool image of the International Space Station captured by the space shuttle. It shows the station in orbit above the Earth.

Our Earth's horizon and the International Space Station's solar array panels are featured in this image photographed by the Expedition 17 crew in August 2008. Credit: NASA

You don’t get to see the full station in this picture, but it’s a beautiful view of the Earth’s horizon off to the side.

Another great image of the International Space Station.

We have written many many articles about the International Space Station for Universe Today. Here’s an article about how the station is so bright now it’s visible during the daytime. Here’s a link to NASA’s gallery of space station images.

September 15, 2009April 26, 2016 by Nancy Atkinson

New Evidence of Dry Lake Beds on Mars

Desiccation patterns on Earth (left) and Mars (right). Credit: Google/NASA/JPL

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Networks of giant polygonal troughs found in crater basins on Mars are cracks caused by evaporating lakes. These landforms had been attributed to thermal contractions in the Martian permafrost, similar to what the Phoenix lander explored near the north pole on the Red Planet. But these polygon-shaped cracks are too large to be caused by thermal contractions and provide further evidence of a warmer, wetter Martian past.

Speaking at the European Planetary Science Conference, M. Ramy El Maarry of the Max Planck Institute for Solar System Research said was excited when he saw that the crater floor polygons seemed to be too large to be caused by thermal processes. “I also saw that they resembled the desiccation cracks that we see on Earth in dried up lakes,” he said. “These are the same type of patterns you see when mud dries out in your back yard, but the stresses that build up when liquids evaporate can cause deep cracks and polygons on the scale I was seeing in the craters.”

Detailed image of large-scale crater floor polygons, caused by desiccation process, with smaller polygons caused by thermal contraction inside. The central polygon is 160 metres in diameter, smaller ones range 10 to 15 metres in width and the cracks are 5-10 metres across. Credit: NASA/JPL

The polygons are formed when long cracks in the surface of the Martian soil intersect. El Marry investigated networks of cracks inside 266 impact basins across the surface of Mars and observed polygons reaching up to 250 metres in diameter. Polygonal troughs have been imaged by several recent missions and until now, were thought to have been created by the same conditions as at the polar regions.

El Maarry created an analytical model to determine the depth and spacing of cracks caused by stresses building up through cooling in the Martian soil. He found that polygons caused by thermal contraction could have a maximum diameter of only about 65 meters, much smaller than the troughs he was seeing in the craters.

El Maarry identified the crater floor polygons using images taken by the MOC camera on Mars Global Surveyor and the HiRISE and Context cameras on Mars Reconnaissance Orbiter. The polygons in El Maarry’s survey had an average diameter of between 70 and 140 meters, with the width of the actual cracks ranging between 1 and 10 meters.

Evidence suggests that between 4.6 and 3.8 billion years ago, Mars was covered in significant amounts of water. Rain and river water would have collected inside impact crater basins, creating lakes that may have existed for several thousand years before drying out. However, El Maarry believes that, in the northern hemisphere, some of the crater floor polygons could have been formed much more recently.

“When a meteorite impacts with the martian surface, the heat can melt ice trapped beneath the martian crust and create what we call a hydrothermal system. Liquid water can fill the crater to form a lake, covered in a thick layer of ice. Even under current climatic conditions, this may take many thousands of years to disappear, finally resulting in the desiccation patterns,” said El Maarry.

Source: Europlanet

September 15, 2009December 24, 2015 by Nancy Atkinson

Titan’s Haze Acts as Ozone Layer

Crucial building blocks in the organic haze layers of Titan and possibly of early Earth come from chemical reactions. Image credits courtesy of NASA-JPL, Dr. Xibin Gu, and Reaction Dynamics Group, University of Hawaii.

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Titan appears to be more like Earth all the time, and a new understanding of Titan’s hazy atmosphere could provide clues to the evolution of Earth’s early atmospheric environment and the development of life on our home planet. Researchers have discovered a series of chemical reactions on Saturn’s largest moon that may shield the moon’s surface from ultraviolet radiation, similar to how Earth’s ozone layer works. The reactions may also be responsible for forming the large organic molecules that compose the moon’s thick and hazy orange atmosphere.

Scientists have long understood that high in Titan’s atmosphere, sunlight breaks apart methane into carbon and hydrogen. These elements react with nitrogen and other ingredients to form a thick haze of complex hydrocarbons which completely enshrouds the moon.

But recently, the role of polyynes in the chemical evolution of Titan’s atmosphere has been vigorously researched and debated. Polyynes are a group of organic compounds with alternating single and triple bonds, such as diacetylene (HCCCCH) and triacetylene (HCCCCCCH). These polyynes are thought to serve as an UV radiation shield in planetary environments, and could act as prebiotic ozone. This would be important for any life attempting to form on Titan.

“Even if you form biologically important molecules (via other reactions) and there is no ozone or ozone like-layer, these molecules will not always survive the harsh radiation environment,” said Ralf Kaiser, lead scientist of the study.

However, the underlying chemical processes that initiate the formation and control the growth of polyynes have not been understood.

Kaiser and his colleagues studied the formation of triacetylene and larger organic molecules in the lab and in computer simulations. They found that triacetylene can be formed by collisions between two small molecules in a reaction that can be easily initiated under the cold conditions found in Titan’s atmosphere.

The authors suggest that triacetylene, an organic molecule that could act as a shield for ultraviolet radiation, may serve as the building block for creating complex molecules in Titan’s atmosphere.

“The present experiments are conducted with molecules containing carbon and hydrogen atoms only,” Kaiser told Universe Today. “To investigate the formation of astrobiologically important molecules on Titan, we have to ‘add’ oxygen and nitrogen, too.” Kaiser said they plan to do those type of experiments later this year.

The team said they hope their combined experimental,theoretical, and modeling study will act as a template, and trigger much needed, successive investigation of the chemistry of surrounding Titan so that a more complete picture of the processes involved in the chemical processing of moon’s atmosphere will emerge.

Lead image caption: Crucial building blocks in the organic haze layers of Titan and possibly of early Earth come from chemical reactions. Image credits courtesy of NASA-JPL, Dr. Xibin Gu, and Reaction Dynamics Group, University of Hawaii

Source: PNAS

September 14, 2009December 24, 2015 by Nancy Atkinson

Super Cell Lightning Storm Raging on Saturn Since January

Saturn lightning storm. Credit: RPWS Team/NASA/JPL/Space Science Institute

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The Cassini spacecraft has been in orbit around Saturn since 2004 and during its mission, has watched nine different lightning storms rage on the planet. But this latest one is the longest lasting and most powerful storm yet: it has been going on since mid-January 2009 with no end in sight. It broke the storm duration record of 7.5 months set by another thunderstorm observed by Cassin between November 2007 and July 2008. Lightning discharges in Saturn’s atmosphere emit very powerful radio waves which are about 10,000 times stronger than their terrestrial counterparts and the huge thunderstorms in Saturn’s atmosphere have diameters of about 3,000 km.

The storm is coursing through “Storm Alley,” a region which lies 35 degrees south of Saturn’s equator where these mammoth storms occur. On board Cassini measuring these storms are the antennas and receivers of the Cassini Radio and Plasma Wave Science (RPWS) instrument.

“These lightning storms are not only astonishing for their power and longevity,” Dr. Georg Fischer of the Austrian Academy of Sciences, “the radio waves that they emit are also useful for studying Saturn’s ionosphere, the charged layer that surrounds the planet a few thousand kilometers above the cloud tops. The radio waves have to cross the ionosphere to get to Cassini and thereby act as a natural tool to probe the structure of the layer and the levels of ionization in different regions.”

Image of a lightning storm on Saturn: Credit: NASA/JPL/Space Science Institute

The observations of Saturn lightning using the Cassini RPWS instrument are being carried out by an international team of scientists from Austria, the US and France. Results have confirmed previous studies of the Voyager spacecraft indicating that levels of ionization are approximately 100 times higher on the day-side than the night side of Saturn’s ionosphere.

“The reason why we see lightning in this peculiar location is not completely clear,” said Fischer. “It could be that this latitude is one of the few places in Saturn’s atmosphere that allow large-scale vertical convection of water clouds, which is necessary for thunderstorms to develop. However, it may be a seasonal effect. Voyager observed lightning storms near the equator, so now that Saturn has passed its equinox on 11 August, we may see the storms move back to equatorial latitudes.”

Saturn’s role as the source of lightning was given added confirmation during Cassini’s last close flyby of Titan on August 25. During the half hour that Cassini’s view of Saturn was obscured by Titan, no lightning was observed. “Although we know from Cassini images where Saturn lightning comes from, this unique event was another nice proof for their origin.” said Fischer.

Fischer presented his findings at the European Planetary Science Congress in Potsdam, Germany.

Source: Europlanet

September 14, 2009December 24, 2015 by Jean Tate

Hubble’s Law

velocity vs distance, from Hubble's 1929 paper

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“The distance to objects beyond the Local Group is closely related to how fast they seem to be receding from us,” that’s Hubble’s law in a nutshell.

Edwin Hubble, the astronomer the Hubble Space Telescope is named after, first described the relationship which later bore his name in a paper in 1929; here is one of the ways he described it, in that paper: “The data in the table [of “nebulae”, i.e. galaxies] indicate a linear correlation between distances and velocities“; in numerical form, v = Hd (v is the speed at which a distant object is receding from us, d is its distance, and H is the Hubble constant).

Today the Hubble law is usually expressed as a relationship between redshift and distance, partly because redshift is what astronomers can measure directly.

Hubble’s Law, which is an empirical relationship, was the first concrete evidence that Einstein’s theory of General Relativity applied to the universe as a whole, as proposed only two years earlier by Georges Lemaître (interestingly, Lemaître’s paper also includes an estimate of the Hubble constant!); the universal applicability of General Relativity is the heart of the Big Bang theory, and the way we see the predicted expansion of space is as the speed at which things seem to be receding being proportional to their distance, i.e. Hubble’s Law.

Although other astronomers, such as Vesto Silpher, did much of the work needed to measure the galaxy redshifts, Hubble was the one who developed techniques for estimating the distance to the galaxies, and who pulled it all together to show how distance and speed were related.

Hubble’s Law is not exact; the measured redshift of some galaxies is different from what Hubble’s Law says it should be, given their distances. This is particularly noticeable for galaxy clusters, and is explained as the motion of galaxies within their local groups or clusters, due to their mutual gravitation.

Because the exact value of the Hubble constant, H, is so important in extragalactic astronomy and cosmology – it leads to an estimate of the age of the universe, helps test theories of Dark Matter and Dark Energy, and much more – a great deal of effort has gone into working it out. Today it is estimated to be 71 kilometers per second per megaparsec, plus or minus 7; this is about 21 km/sec per million light-years. What does this mean? An object a million light-years away would be receding from us at 21 km/sec; an object 10 million light-years away, 210 km/sec, etc.

Perhaps the most dramatic revision to the Hubble Law came in 1998, when two teams independently announced that they’d discovered that the rate of expansion of the universe is accelerating; the shorthand name for this observation is Dark Energy.

Harvard University’s Professor of Cosmology John Huchra maintains a webpage on the history of the Hubble constant, and this page from Ned Wright’s Cosmology Tutorial explains how the Hubble law and cosmology are related.

There are several Universe Today stories about the Hubble relationship and the Hubble constant; for example Astronomers Closing in on Dark Energy with Refined Hubble Constant, and Cosmologists Improve on Standard Candles Measurement.

And we have done some Astronomy Casts on it too, How Old is the Universe? and, How Big is the Universe?

Sources:
UT-Knoxville
NASA
Cornell Astronomy

September 14, 2009December 29, 2015 by Nancy Atkinson

Carnival of Space #120

This week’s Carnival of Space is hosted by Bruce Irving over at Music of the Spheres

Click here to read the Carnival of Space #120.

And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, let Fraser know if you can be a host, and he’ll schedule you into the calendar.

Finally, if you run a space-related blog, please post a link to the Carnival of Space. Help us get the word out.

September 14, 2009September 14, 2009 by Nancy Atkinson

Armadillo Powers Toward $1 Million Prize

A rocket powered vehicle successfully completed the first step toward qualifying to win a $1 million prize for NASA’s Northrop Grumman Lunar Lander Challenge. Armadillo Aerospace’s “Scorpius” lander set world records for vertical landings and takeoff flights by flying up 50 meters (164 feet) into the air, maneuvering over to land on a simulated rocky lunar surface 50 meters (164 feet) away, and then rising and flying back to land where it started. The flight included a requirement of at least 180 seconds of flying time. Watch the video from the second qualifying flight here. Armadillo is the first team of three teams looking to nab the prize this year.
Continue reading “Armadillo Powers Toward $1 Million Prize”