Posted on by Tammy Plotner

2010 Perseid Meteor Shower


In just a few days – during the evening hours of August 12 and morning of August 13 – one of the year’s most reliable meteor showers is about to grace this year’s dark skies. Not only will we be in for some celestial fireworks, but the planets are going to put on a show as well. Who, what, when, where, why and how? Then step inside and let’s talk about the 2010 Perseid meteor shower…

During the latter half of July and the beginning of August, the Earth cruises through several minor cometary debris streams – producing equally minor meteor showers which meander through the constellations of Cygnus, Capricornus and Aquarius. This is the type of normal activity which is enjoyed by both the northern and southern hemisphere. One any given good, dark night, you might spot as many as a dozen meteors during an evening’s observing session. It’s a nice transition in the weather for both halves of Earth and this period of time makes for comfortable watching. While I love catching a sparkling trail when I really wasn’t expecting or waiting for one, there’s nothing in the heavens that can make me yell out loud like being witness to a productive meteor shower.


And the Perseids produce…

Where exactly did all the “stuff” come from that causes the annual Perseid meteor shower to be so reliable? Try periodic comet 109P/Swift-Tuttle. Discovered in 1862, Swift-Tuttle is called “periodic” because it makes a pass through our solar system about every 133-135 years leaving behind a debris trail. As early as 36 AD, Chinese astronomers began to notice a sharp peak of meteor activity during this time and began keeping record. Other astronomers followed suit until astronomy became a rather dangerous occupation and facts and figures began to dwindle. Although often referred to as “the tears of St. Lawrence” to celebrate the martyr’s death on August 10, it wasn’t until 1835 and Adolphe Quetelet that the annual Perseid was actually given credit to an individual for pinpointing its radiant and peak date.

Within four years, sharp-eyed observers had not only began to note the Perseid presence, but to make an accurate hourly account of the fall rate as well. In 1839, E. Heis gave us his first written documentation of a maximum rate of 160 per hour and over the next several decades, many other observers joined him. What they noticed through their observations was the fall rate changed from year to year… Why?

Between 1864 and 1866, Giovanni Schiaparelli also took an interest in the Perseids and computed the stream’s orbit. What he discovered was astounding. It nearly matched that of a comet discovered just two years earlier – 109P/Swift-Tuttle. After that, it didn’t take very long to figure out each high spike in fall rates also corresponded with the comet’s known perihelion. It was the very first time a meteor shower had been positively identified with a comet!

But, when it comes to science, proving a speculation is everything. Record keeping for that period of time wasn’t exactly the best and in 1973 astronomer Brian Marsden was busy trying to predict the return of comet Swift/Tuttle. His chosen date was 1981 and as annual activity of the Perseid meteor shower increased, so did the excitement of recapturing the comet. However, like so many astronomical predictions, the traveler from Oort Cloud failed to make its debut appearance Needless to say, between disappointment and lunar interference, interest in the Perseid’s cometary originator quickly faded. However, Marsden wasn’t about to give up. Choosing another documented comet seen in 1737, he made another prediction… Swift/Tuttle would return in 1992.

This time was sweet success.

With 18 years between now and comet Swift/Tuttle’s last perihelion, will the 2010 Perseid meteor activity be a smashing shower or a dwindling display? It’s really hard to say because the stream is so wide and complex. We know when the Earth passes through this outgassing of materials that we can expect a certain amount of activity during a marginal time period – but we can only make a guess at how much material was expelled. There may have been time centuries ago when the comet did something very unexpected (as comets have a way of doing) and left a dense cloud just waiting for us to orbit through… And it may be burning itself out during each successive pass around Sol. So many things can happen! Jupiter may have affected the stream’s position – or a huge flurry of activity might occur during daylight. But what about this year?

Thankfully there will be no Moon to obscure fainter meteors and zenith hourly rates may approach up to nearly 100 per hour. But that’s a very optimistic estimate since the Perseids are notoriously fast – burning through our atmosphere at 140,000 mph – and sometimes very faint. As the evening begins, facing east/northeast will be best for most northern hemisphere observers, and follow Perseus to the north as it rises. Unfortunately, southern hemisphere observers aren’t likely to see any of this activity – but it never hurts to keep watch to the northern horizon if you’re out. If you have to be selective about the times you watch, the very best views will be had when the constellation is at its highest – after local midnight through local dawn.

Don’t wait until the peak date to begin your observations. Perseid activity is already underway at 15 to 20 per hour and the fall rate will only continue to increase as it nears the night of August 12/13th when up to 75 meteors may grace the starry skies. If you live in a light polluted area, make plans to get rural. Many farmers and home owners in the countryside are more than happy to grant you permission to choose a safe observing spot on their land if you explain what you’re doing – so ask! Be sure to take along things which will aid in your comfort, such as a reclining lawn chair or blanket (meteor neck sucks). Make it a popcorn and soda family event! But stay away from white light. If being in the wild scares you a bit, create your own “night vision friendly” flashlight by stretching a red balloon over the lens. If you arrive at sunset? Then check out the beautiful conjunction of Mercury Mars, Saturn, Venus and the very tender crescent Moon….

Wishing you clear skies and the very best of luck!

Here’s information on the 2009 Perseids.

Posted on by Steve Nerlich

Astronomy Without A Telescope – Strange Stars

(Caption) One step closer to a black hole? A hypothetical strange star results from extreme gravitational compression overcoming the strong interaction that holds neutrons and protons together. Credit Swinburne University - astronomy.swin.edu.au

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Atoms are made of protons, neutrons and electrons. If you cram them together and heat them up you get plasma where the electrons are only loosely associated with individual nuclei and you get a dynamic, light-emitting mix of positively charged ions and negatively charged electrons. If you cram that matter together even further, you drive electrons to merge with protons and you are left with a collection of neutrons – like in a neutron star. So, what if you keep cramming that collection of neutrons together into an even higher density? Well, eventually you get a black hole – but before that (at least hypothetically) you get a strange star.

The theory has it that compressing neutrons can eventually overcome the strong interaction, breaking down a neutron into its constituent quarks, giving a roughly equal mix of up, down and strange quarks – allowing these particles to be crammed even closer together in a smaller volume. By convention, this is called strange matter. It has been suggested that very massive neutron stars may have strange matter in their compressed cores.

However, some say that strange matter has a more fundamentally stable configuration than other matter. So, once a star’s core becomes strange, contact between it and baryonic (i.e. protons and neutrons) matter might drive the baryonic matter to adopt the strange (but more stable) matter configuration. This is the sort of thinking behind why the Large Hadron Collider might have destroyed the Earth by producing strangelets, which then produce a Kurt Vonnegut Ice-9 scenario. However, since the LHC hasn’t done any such thing, it’s reasonable to think that strange stars probably don’t form this way either.

More likely a ‘naked’ strange star, with strange matter extending from its core to its surface, might evolve naturally under its own self gravity. Once a neutron star’s core becomes strange matter, it should contract inwards leaving behind volume for an outer layer to be pulled inwards into a smaller radius and a higher density, at which point that outer layer might also become strange… and so on. Just as it seems implausible to have a star whose core is so dense that it’s essentially a black hole, but still with a star-like crust – so it may be that when a neutron star develops a strange core it inevitably becomes strange throughout.

Anyhow, if they exist at all, strange stars should have some tell tale characteristics. We know that neutron stars tend to lie in the range of 1.4 to 2 solar masses – and that any star with a neutron star’s density that’s over 10 solar masses has to become a black hole. That leaves a bit of a gap – although there is evidence of stellar black holes down to only 3 solar masses, so the gap for strange stars to form may only be in that 2 to 3 solar masses range.

By adopting a more compressed 'ground state' of matter, a strange (quark) star should be smaller, but more massive, than a neutron star. RXJ1856 is in the ballpark for size, but may not be massive enough to fit the theory. Credit: chandra.harvard.edu

The likely electrodynamic properties of strange stars are also of interest (see below). It is likely that electrons will be displaced towards the surface – leaving the body of the star with a nett positive charge surrounded by an atmosphere of negatively charged electrons. Presuming a degree of differential rotation between the star and its electron atmosphere, such a structure would generate a magnetic field of the magnitude that can be observed in a number of candidate stars.

Another distinct feature should be a size that is smaller than most neutron stars. One strange star candidate is RXJ1856, which appears to be a neutron star, but is only 11 km in diameter. Some astrophysicists may have muttered hmmm… that’s strange on hearing about it – but it remains to be confirmed that it really is.

Further reading: Negreiros et al (2010) Properties of Bare Strange Stars Associated with Surface Electrical Fields.

Posted on by Nancy Atkinson

Space Telescopes Team Up to Capture Spectacular Galactic Collision

A new image of two tangled galaxies has been released by NASA's Great Observatories. The Antennae galaxies, located about 62 million light-years from Earth, are shown in this composite image from the Chandra X-ray Observatory (blue), the Hubble Space Telescope (gold and brown), and the Spitzer Space Telescope (red). The Antennae galaxies take their name from the long antenna-like arms seen in wide-angle views of the system. These features were produced in the collision. Image credit: Chandra: NASA/CXC/SAO, Spitzer: NASA/JPL-Caltech, Hubble: NASA/STScI

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From JPL:

A new image of two tangled galaxies has been released by NASA’s Great Observatories. The Antennae galaxies, located about 62 million light-years from Earth, are shown in this composite image from the Chandra X-ray Observatory (blue), the Hubble Space Telescope (gold and brown), and the Spitzer Space Telescope (red). The Antennae galaxies take their name from the long, antenna-like arms seen in wide-angle views of the system. These features were produced in the collision.

The collision, which began more than 100 million years ago and is still occurring, has triggered the formation of millions of stars in clouds of dusts and gas in the galaxies. The most massive of these young stars have already sped through their evolution in a few million years and exploded as supernovas.

The X-ray image from Chandra shows huge clouds of hot, interstellar gas, which have been injected with rich deposits of elements from supernova explosions. This enriched gas, which includes elements such as oxygen, iron, magnesium and silicon, will be incorporated into new generations of stars and planets. The bright, point-like sources in the image are produced by material falling onto black holes and neutron stars that are remnants of the massive stars. Some of these black holes may have masses that are almost one hundred times that of the sun.

The Spitzer data show infrared light from warm dust clouds that have been heated by newborn stars, with the brightest clouds lying in the overlap region between the two galaxies. The Hubble data reveal old stars and star-forming regions in gold and white, while filaments of dust appear in brown. Many of the fainter objects in the optical image are clusters containing thousands of stars.

Posted on by Nancy Atkinson

There’s Water On the Moon’s Surface, But Interior Could Be Dry

Hadley Rille, the landing site for Apollo 15. Credit: NASA

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With all the recent news of water on the Moon, a new paper published today in the journal Science may offer a surprise – or it may bring us back to previous assumptions about the Moon. A new analysis of eleven lunar samples from the Apollo missions by Zachary Sharp from the University of New Mexico and his colleagues indicates that when the Moon formed, its interior was essentially dry. While the recent findings of ubiquitous water and hydroxyl on the surface as well as water ice in the lunar poles are not challenged by this new finding, it does dispute — somewhat — two other recent papers that proposed a wetter lunar interior than previously thought. “The recent LCROSS findings were of water on the lunar surface due to cometary impacts, and the ice is from the comets themselves,” Sharp told Universe Today. “We are talking about water that was present in the molten early Moon 4.5 billion years ago.”

The accepted theory of how the Moon formed is that a Mars-sized body slammed into our early Earth, creating a big disk of debris that would ultimately form into the Moon.

Although planetary scientists are still refining models of the Moon’s formation, there is much to suggest a dry Moon. Any water would have been vaporized by the high temperatures generated by the impact and cataclysm that followed, and vapor would have escaped into space. The assumption is that the only way there could be water in the Moon’s interior if is the impactor was especially water-rich, and also if the Moon solidified quickly, which is considered unlikely.

But earlier this year, Francis McCubbin and his team from the Carnegie Institution for Science released their findings of a surprisingly high abundance of water molecules — as high as several thousand parts per million — bound to phosphate minerals within volcanic lunar rocks, which would have formed well beneath the lunar surface and date back several billion years.

Additionally, in 2008, Alberto Saal of Brown University and colleagues found a slightly lower abundance of water in the lunar mantle, but it was significantly higher than the previous estimate of 1 part per billion.
These two findings have been pushing lunar scientists to find possible alternative explanations for the Moon’s formation to account for all the water.

But now, Sharp and his team studied a wide range of lunar basalts and measured the composition of chlorine isotopes. Using gas source mass spectrometry they found a wide range of chlorine isotopes contained in the samples which are 25 times greater than what is found in rocks and minerals from Earth and from meteorites.
Chlorine is very hydrophilic, or attracted to water, and is an extremely sensitive indicator of hydrogen levels. Sharp and his team say that, if lunar rocks had initial hydrogen contents anywhere close to those of terrestrial rocks, then the fractionation of chlorine into so many different isotopes would never have happened on the Moon. Because of this Sharp and his colleagues say their results suggest a very dry interior of the Moon.

Sharp proposes that Saal and McCubbin’s calculations of high hydrogen contents in some lunar samples are not typical, and perhaps those samples are the product of certain igneous processes that resulted in their “extremely volatile enrichment.” They do not, however, represent the high and variable isotopic chlorine values reported in the majority of lunar rocks, Sharp said.

Still, there could be a compromise between the varied findings. “There are uncertainties that one has to take into account when doing this type of study, ” Sharp told Universe Today, “and if we take the low estimates of Saal and McCubbin’s papers, they are not so different from our findings.”

But the discrepancies, however small, show that perhaps we can’t make generalizations about the entire Moon from limited samples.

“We have not yet looked for water in a wide range of lunar samples,” said Jeff Taylor from the University of Hawaii, who was not involved in any of the aforementioned studies. “It is quite possible that the initial differentiation of the Moon and subsequent processes such as mantle overturn concentrated whatever water the Moon had into certain areas. Until we measure more samples, including samples from the farside (represented by many of the lunar meteorites and eventually by sample-return missions), we will not know for sure how much water is in the bulk Moon.”

In combination, all the recent studies of the lunar surface show there is likely a complex chemistry on the Moon that we have yet to understand.

“In other words,” said Taylor, “we need more work!”

Source: Science News

Earlier Papers:

Nominally hydrous magmatism on the Moon by Francis McCubbin et al., 2010.

Volatile content of lunar volcanic glasses and the presence of water in the Moon’s interior, Alberto Saal et al. Nature.

Posted on by Nancy Atkinson

Stunning Aurora Videos

If you weren’t lucky enough to be in the right place or the right time to see any of the aurora produced by the Sun’s recent spate of activity, skywatchers around the world have started posting videos online of some really spectacular Northern Lights. Above, is the view on August 4, 2010 from Telemark, Norway. Below are more sights, also from August 4, from Latvia and Risør, Norway. These videos were posted on CitizenTube, a newsy version of YouTube.
Continue reading “Stunning Aurora Videos”

Posted on by Tammy Plotner

Observing Spotlight – Whatever Happened to M71?

The M71 Globular Cluster, as pictured by the Hubble space telescope. Credit: NASA

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In our rush to look at the bright and beautiful objects in the night, we often overlook celestial curiosities in favor of a more splashy neighbor. How many times have you looked at the Andromeda Galaxy, but really didn’t take the time to power up and study M110? Perhaps you spent a whole evening studying the intricacies of the Great Orion Nebula – but totally forgot about striking M78? It’s the way of things. But, next time you drop by the Dumbbell Nebula, spend some Hubl time with the sparkling stars of Messier 71…

Discovered by Philippe Loys de Cheseaux in 1746 and researched by Charles Messier then added his catalog of comet-like objects in 1780, this brilliant globular cluster let’s its presence be known at a distance of about 12,000 light years away from Earth. Covering an area measuring approximately 27 light years across, it shines with a luminosity of around 13,200 suns – not bad for a conglomeration of stars which could be as old as 9-10 billion years. Until about four decades ago, Messier 71 was believed to be a dense galactic cluster – nearly devoid of RR Lyrae “cluster” variable stars and rich in metallicity.

And a concentrated cluster of stars it stayed until modern H-R diagram photometry picked up a short “horizontal branch” in its structure…

Who remembers to stop and study? While grandiose images like our Hubble lead-in photo might pique your curiosity for a moment, it’s the deep sky dedication and devotion revealed in the work of Bernhard Hubl which ignites the sense of wonder all over again…

M71 by Bernhard Hubl

Reach out and touch M71 for yourself. Located in the constellation of Sagitta at RA:19h 53m 48s Dec: +18°47′ and close to magnitude 7, it’s easily caught in average binoculars from a dark sky location, beauty revealed in smaller telescopes and breathtakingly resolved in large aperture telescopes. It’s really not hard to find if you just take the time to let your eyes relax to see Sagitta’s faint arrow-shaped signature asterism. Just aim mid-way between Gamma and Delta and be swept away…

Because it’s full of stars.

Many thanks go to Bernhard Hubl of Northern Galactic for his untold hours of work just to share the inspiration!

Posted on by Nicholos Wethington

Telescope’s Laser Pointer Clarifies Blurry Skies

The new laser adaptive optics system in action. At Mount Hopkins in Arizona, a bundle of five lasers is shot into the atmosphere to improve the imaging of the 6.3-meter MMT telescope. Image Credit: Thomas Stalcup

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While it’s handy for us humans (and all of the other life on our planet for that matter), the atmosphere is almost universally cursed among astronomers. It’s great for breathing, but when it comes to astronomical observations of faint objects, all the atmosphere tends to do is muck up the view. In the past 20 years, development of adaptive optics – essentially telescopes that change the shape of their mirrors to improve their imaging capability – has dramatically improved what we can see in space from the Earth.

With a new technique involving lasers (Yes! Lasers!), the images capable with an adaptive optics telescope could be nearly as crisp as those from the Hubble Space Telescope over a wide field of view. A team of University of Arizona astronomers led by Michael Hart has developed a technique that helps calibrate the surface of the telescope very precisely, which leads to very, very clear images of objects that would normally be very blurry.

Laser adaptive optics in telescopes are a relatively new development in getting better image quality out of ground-based telescopes. While it’s nice to be able to use space-based telescopes like the Hubble and the forthcoming James Webb Space Telescope, they are certainly expensive to launch and maintain. On top of that, there are a lot of astronomers competing for very little time on these telescopes. Telescopes like the Very Large Telescope in Chile, and the Keck Telescope in Hawaii both already use laser adaptive optics to improve imaging.

Initially, adaptive optics focused in on a brighter star near the area of the sky that the telescope was observing, and actuators in the back of the mirror were moved very rapidly by a computer to cancel out atmospheric distortions. This system is limited, however, to areas of the sky that contain such an object.

Laser adaptive optics are more flexible in their usability – the technique involves using a single laser to excite molecules in the atmosphere to glow, and then using this as a “guide star” to calibrate the mirror to correct for distortions caused by turbulence in the atmosphere. A computer analyzes the incoming light from the artificial guide star, and can determine just how the atmosphere is behaving, changing the surface of the mirror to compensate.

In using a single laser, the adaptive optics can only compensate for turbulence in a very limited field of view. The new technique, pioneered at the 6.5-m MMT telescope in Arizona, uses not just one laser but five green lasers to produce five separate guide stars over a wider field of view, 2 arc minutes. The angular resolution is less than that of the single laser variety – for comparison, the Keck or VLT can produce images with a 30-60 milli-arcsecond resolution, but being able to see better over a wider field of view has many advantages.

In the image on the left, the cluster M3 appears blurry with the laser adaptive optics system turned off. Things are much clearer using the system, and individual stars in the cluster become visible, as can be seen in the image on the right. Image Credit: Michael Hart

The ability to take the spectra of older galaxies, which are very faint, is possible using this technique. By taking their spectra, scientists are better able to understand the composition and structure of objects in space. Using the new technique, taking the spectra of galaxies that are 10 billion years old – and thus have a very high red shift – should be possible from the ground.

Supermassive clusters of stars would also be more easily scrutinized using the technique, as images taken in a single pointing of the telescope on different nights would allow astronomers to understand just which stars are part of the cluster and which are not gravitationally bound.

The results of the team’s efforts was published in the Astrophysical Journal in 2009, and the original paper is available here on Arxiv.

Source: Eurekalert, Arxiv paper

Posted on by Nancy Atkinson

Carnival of Space #165

This week’s Carnival of Space is hosted by our good friend Stu Atkinson his blog, Cumbrian Sky.

Click here to read the Carnival of Space #165.

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.

Posted on by Nancy Atkinson

Latest from Mars: Exposed Ice in Fresh Crater, Plus 100’s More New Images

At the center of this view of an area of mid-latitude northern Mars, a fresh crater about 6 meters (20 feet) in diameter holds an exposure of bright material, blue in this false-color image. Image Credit: NASA/JPL-Caltech/University of Arizona

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Mars-o-philes rejoice! New images from Mars galore, including this “after” image of Mars’ northern hemisphere which reveals a new crater was created sometime between April 2004 and January 2010. Intriguingly, scientists believe exposed ice is visible in this new image from the HiRISE camera. This is just one of the latest release of hundreds of high-resolution HiRISE images, so go get your fill of Mars at the HiRISE site. But what about that ice?

The crater is at a latitude of 44 degrees North and is itself located on the ejecta of a larger crater. The image was acquired in early summer, when frost at this latitude is not expected. That’s why the HiRISE science team believes the bright blue material in this false-color color image is sub-surface ice that was exposed by the impact.

This ice is probably at the same depth and has a similar origin to that excavated by the Phoenix lander back in 2008. The area of exposed ice based on the HiRISE images is about 1-2 square meters (10-20 square feet.

An intriguing image, and a great example of the treasures available in this newest release of images from Mars.

For more images, see the HiRISE website.

Posted on by Nancy Atkinson

Solar Storm Update: Best Times for Viewing Aurorae

Why is the Sun So Hot?
Image from the Solar Dynamics Observatory of the filaments coming from the Sun's surface. Credit: NASA

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The Harvard Smithsonian Center for Astrophysics released the latest information on the July 31/August 1 activity on the Sun that is just now reaching Earth. They predict we’ll have multiple opportunities for a display of the Northern Lights over the next two days. The latest word from the solar scientists is that the Sun erupted not just once, but four times. All four coronal mass ejections are headed toward Earth.

Space weather forecasts are even more challenging than regular weather forecasts, said Dr. Leon Golub, and a coronal mass ejection is like a hurricane: it’s large and fuzzy, and doesn’t always move at the same speed. Currently, the estimated arrival times are:

Wednesday, Aug. 4 – 3:00 a.m. EDT (0700 GMT on Aug. 5; aurorae not visible in daylight)
Wednesday, Aug. 4 – 1:00 p.m. EDT (1600 GMT, again the daylight issue)
Wednesday, Aug. 4 – 8:00 p.m. EDT (0000 GMT on Aug. 5)
Thursday, Aug. 5 – 2:00 a.m. EDT (0600 GMT)

Any one of these events may or may not generate an aurora. It depends on details like magnetic field orientation. If the magnetic field in the oncoming solar plasma is directed opposite Earth’s magnetic field, the result could be spectacular aurorae. If the fields line up, the coronal mass ejection could slide past our planet with nary a ripple.

The Center for Astrophysics suggested these two resources:

Map of current auroral activity

Chart of proton flux (watch for the numbers to go up as each wave arrives)

Source: Harvard Smithsonian Center for Astrophyics