Astronomy Archives

March 3, 2009December 24, 2015 by Nancy Atkinson

A Supernova Story

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SN 2009ab as seen by the AlbaNova Telescope in Stockholm, Sweden. Credit: Magnus Persson, Robert Cumming and Genoveva Micheva/Stockholm University

Have you ever discovered a supernova? Well, I haven’t, but I can only imagine finding a star that has blown itself to smithereens must be pretty exciting. At least that’s what I thought, anyway….

Seemingly, a fair amount of folks must be out there who have found supernovae. In 2008 alone, 278 supernovae were found, one by a 14-year old girl. But 2008 was a really slow year in the supernova department. In 2007, 584 were discovered – a record number – and in 2006, 557 supernovae were spied by astronomers, both professional and amateur. 40 have been found so far in 2009. But even with those fairly big numbers, I still gotta believe that finding a supernova must be absolutely incredible. So when someone I knew, Robert Cumming from Stockholm University in Sweden, recently played a part in finding a supernova, I emailed him my congratulations. Imagine my surprise when he replied, “It’s no big deal, really.”

But Robert, it’s a SUPERNOVA!

I had heard of Scandinavian stoicism, but this was off the charts! Besides that, I knew Robert is not originally from Sweden.

So, I begged him to tell me all about it.

“Well, since you ask,” he said with a smile. Okay, maybe, just maybe he was more excited than he was letting on.

Here’s the story of how Supernova 2009ab was discovered:

“I’ve observed a few supernovae before and I’ve had my name on the odd IAU circular, but this is the first time I’ve been one of the first to actually confirm one,” said Robert, with just a hint of excitement in his voice.

On February 8, the Katzman Automatic Imaging Telescope (KAIT), a 30-inch fully robotic telescope at the Lick Observatory on Mt. Hamilton in California discovered a bright spot not seen before in the outskirts of the spiral galaxy UGC 2998, 150 million light years away. Astronomers from KAIT wanted to make a second observation to verify, but bad weather made it impossible for them to confirm that the new object was not an asteroid or instrumental error. So, the KAIT astronomers requested observations from other telescopes around the world.

Magnus Persson, also from the Stockholm University was getting ready to do some observations using the University’s AlbaNova Telescope, when Robert received an email from KAIT about needing confirmation observations.

AlbaNova Telescope. Credit: Teresa Riehm/Stockholm University.

“I knew Magnus was going to be observing – he was planning to take some pictures of the Crab nebula for a colleague,” said Robert. “And I had this mail from the KAIT in California.”

So, the two set to work in an effort to locate the possible supernova.

Robert and Persson used different filters and took a few images of galaxy UGC 2998. “The supernova was right there on our first 45-second exposure – we were kind of amazed!” he said.

The two astronomers from Sweden were able to establish that the new light source showed all the signs of being a supernova. The supernova shines in a blue color, in contrast to the stars in the galaxy which are generally old and red, and the other stars in the image which lie in our galaxy. Shortly after the explosion, such a supernova emits as much energy as the entire host galaxy.

“We did the observations properly, and then I picked the best data to make very rough photometry, got comparison magnitudes from Gregor Dusczanowicz, Sweden’s amateur supernova discoverer, talked to a colleague to check we hadn’t forgotten anything important, and mailed off the measurements to the Central Bureau for Astronomical Telegrams.”

Other telescopes have now observed SN 2009ab, but the AlbaNova telescope was the first to successfully take images and confirm it as a new supernova. The following day, astronomers on the Canary Islands took a spectrum using the considerably bigger Telescopio Nationale Galileo and were able to determine the supernova was of type Ia, that is a white dwarf star which had exploded in a binary system. As Magnus’ and Robert’s confirmation was published in an astronomical telegram, the new supernova was named SN 2009ab, this year’s 28th supernova.

So, SN 2009ab is a story of the cooperative camaraderie that exists between astronomers, working together to verify and cross-check their findings. Here’s a list of everyone who contributed in the discovery of this supernova.

It’s also the story of a new telescope in an unlikely location being used to make new and exciting — yes exciting –discoveries. The Stockholm University Department of Astronomy uses the AlbaNova telescope, a 1-meter reflector, mainly for education and instrumental development. Robert said the plan is to use the telescope to do environmental monitoring, using LIDAR to monitor ozone and particle pollution in the city.

But Robert said the discovery of the supernova shows it is also possible to do scientifically interesting astronomical observations with the telescope, despite the limitations from Stockholm’s bad weather and light pollution.

The AlbaNova Observatory in Stockholm. Credit: Magnus Näslund/Stockholm University

“Our site is right in the city, so our sky brightness is scary. So far we haven’t measured just how bad it is, so it was a really nice surprise to get something out of it,” he said.

“The telescope is still pretty new, and with the Stockholm weather lately the experience of observing at all is pretty exciting,” Robert said. “And it is exciting that the telescope is now in full use. If we can do observations like these, we can do much more.”

So finally, I got Robert to admit he was excited. But the Scandinavian modesty and stoicism quickly returned.

“But the supernova itself is no big deal really, and our picture isn’t that good,” he said. “Many amateurs take pictures better than ours.”

Well, Robert, I’m excited for you! Congratulations!

Learn more about the AlbaNova Telescope.

Listen to Robert Cumming on the March 2 “365 Days of Astronomy” podcast, “Astrosvenska for Anyone: Space Swedish in Ten Ridiculously Short Lessons” (you’ll enjoy hearing his “Swedish” accent).

Robert Cumming also writes for a Swedish astronomy website, Populär Astronomi

March 2, 2009December 24, 2015 by Fraser Cain

Circumference of the Earth

The circumference of the Earth in kilometers is 40,075 km, and the circumference of the Earth in miles is 24,901. In other words, if you could drive your car around the equator of the Earth (yes, even over the oceans), you’d put on an extra 40,075 km on the odometer. It would take you almost 17 days driving at 100 km/hour, 24 hours a day to complete that journey.

If you like, you can calculate the Earth’s circumference yourself. The formula for calculating the circumference of a sphere is 2 x pi x radius. So, the radius of the Earth is 6371 km. Plug that into the formula, and you get 2 x 3.1415 x 6378.1 = 40,074. It would be more accurate if you use more digits for pi.

You might be interested to know that the circumference of the Earth is different depending on how you measure it. If you measure the circumference around the Earth’s equator, you get the 40,075 km figure I mentioned up to. But if you measure it from pole to pole, you get 40,007 km. This is because the Earth isn’t a perfect sphere; it bulges around the equator because it’s rotating on its axis. The Earth is a flattened sphere, and so the distance around the equator is further than the circumference around the poles.

Want some comparison? The circumference of the Moon is 10,921 km, and the circumference of Jupiter is 500,000 km.

Here are a bunch of measurements for you:
Circumference of the Earth in kilometers: 40,075 km
Circumference of the Earth in meters: 40,075,000 meters
Circumference of the Earth in centimeters: 4,007,500,000 centimeters

Circumference of the Earth in miles: 24,901 miles
Circumference of the Earth in feet: 131,477,280 feet
Circumference of the Earth in inches: 1,577,727,360 inches

We have written many articles about Earth for Universe Today. Here are some photos of the Earth and Moon together, and here are the 10 most impressive impact craters on Earth.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

Reference:
NASA Solar System Exploration: Earth Facts and Figures

February 28, 2009December 24, 2015 by Ian O'Neill

New Technique Allows Astronomers to Discover Exoplanets in Old Hubble Images

Using a new imaging technique on an 11 year old Hubble observation, an exoplanet has been discovered orbiting the young star HR 8799 (NASA/HST)

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The Hubble Space Telescope has recently provided us with some astonishing images of exoplanets orbiting distant stars. This is a departure from the indirect detection of exoplanets by measuring the “wobble” of stars (revealing the gravitational presence of a massive planetary body) or the transit of exoplanets through the line of sight of the parent star (causing its brightness to dim). Scientists have refined Hubble’s exoplanet hunting abilities to directly image these alien worlds in visible light. However, astronomers now have another trick to find these mysterious worlds. A new imaging technique is allowing us to see exoplanets already hiding in archival Hubble data…

It has been estimated that another 100 previously unknown exoplanets could be discovered in old Hubble data. The technique being tested by astronomers at the University of Toronto could be a very powerful new way to reveal the existence of a huge number of buried jewels buried by the glare of star light.

In November 2008, a spate of direct imagery of exoplanets showed the world how advanced our ground and space-based observatories were becoming. One such discovery was an observing campaign of the young star HR 8799 by the near-infrared adaptive optics observations of the Gemini and Keck telescopes. HR 8799 (140 light years away, approximately 50% more massive than our Sun) plays host to three massive gas giants (10, 10 and 7 times the size of Jupiter). Now that HR 8799 is known to have large exoplanets orbiting around it, the University of Toronto astronomers, headed by David Lafrenière, have re-examined images taken by Hubble of that same star in 1998, to see if there is any trace of these exoplanets in the old data. In 1998, HR 8799 appeared to be a lonely star, with no associated exoplanets.

Using a new technique to extract the weak exoplanet emission in the Hubble image, Lafrenière’s team have been able to cut down the glare of the parent star to reveal the presence of the outermost exoplanet of the trio known to be orbiting HR 8799 (pictured top). The other two exoplanets remain too close to the star to be resolved.

The University of Toronto result “definitely indicates that we should reanalyze all the existing Hubble images of young stars with the new approach — there’s probably 100 to 200 stars where planets could be seen,” comments planet-hunter Bruce Macintosh of the Lawrence Livermore National Laboratory in California. Many of these stars have already been studied by the powerful Keck observatory in Hawaii, so astronomers now have an exciting and powerful new analysis tool to hopefully reveal more overlooked exoplanets.

However, this most recent result was achieved by using a space-based observatory, as some of the near-infrared emission from the exoplanet will be absorbed by the Earth’s atmosphere.

The new exoplanet discovery potential has excited many astronomers, and it has highlighted the importance of maintaining a good archive of astronomical observations. “The first thing it tells you is how valuable maintaining long-term archives can be. Here is a major discovery that’s been lurking in the data for about 10 years!” said Matt Mountain, director of the Space Telescope Science Institute in Baltimore. “The second thing its tells you is having a well calibrated archive is necessary but not sufficient to make breakthroughs — it also takes a very innovative group of people to develop very smart extraction routines that can get rid of all the artifacts to reveal the planet hidden under all that telescope and detector structure.”

Hopefully we’ll be seeing even more exoplanet discoveries over the coming months, not just from new observing campaigns, but possibly from old observations using archived observatory data. Exciting times!

Source: Science News

February 27, 2009December 24, 2015 by Nancy Atkinson

Ancient Pulsar Still Pulsing

Artist concept of ancient pulsar J0108. Image credit: X-ray: NASA/CXC/Penn State/G.Pavlov et al. Optical: ESO/VLT/UCL/R.Mignani et al. Illustration: CXC/M. Weiss

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It may be old, but it ain’t dead. The Chandra X-Ray Observatory has found the oldest isolated pulsar ever detected. While this pulsar is ancient, this exotic object is still kicking and is surprisingly active. According to radio observations, the pulsar, PSR J0108-1431 (J0108 for short) is about 200 million years old. Among isolated pulsars — ones that have not been spun-up in a binary system — it is over 10 times older than the previous record holder. A team of astronomers led by George Pavlov of Penn State University observed J0108 in X-rays with Chandra, and found that it glows much brighter in X-rays than was expected for a pulsar of such advanced years.

At a distance of 770 light years, it is also one of the nearest pulsars we know of.

Pulsars are created when stars that are much more massive than the Sun collapse in supernova explosions, leaving behind a small, incredibly weighty core, known as a neutron star. At birth, these neutron stars, which contain the densest material known in the Universe, are spinning rapidly, up to a hundred revolutions per second. As the rotating beams of their radiation are seen as pulses by distant observers, similar to a lighthouse beam, astronomers call them “pulsars”.

Astronomers observe a gradual slowing of the rotation of the pulsars as they radiate energy away. Radio observations of J0108 show it to be one of the oldest and faintest pulsars known, spinning only slightly faster than one revolution per second.

J0108 in a combination of optical and X-ray. Image credit: X-ray: NASA/CXC/Penn State/G.Pavlov et al. Optical: ESO/VLT/UCL/R.Mignani et al.

Some of the energy that J0108 is losing as it spins more slowly is converted into X-ray radiation. The efficiency of this process for J0108 is found to be higher than for any other known pulsar.

“This pulsar is pumping out high-energy radiation much more efficiently than its younger cousins,” said Pavlov. “So, although it’s clearly fading as it ages, it is still more than holding its own with the younger generations.”

It’s likely that two forms of X-ray emission are produced in J0108: emission from particles spiraling around magnetic fields, and emission from heated areas around the neutron star’s magnetic poles. Measuring the temperature and size of these heated regions can provide valuable insight into the extraordinary properties of the neutron star surface and the process by which charged particles are accelerated by the pulsar.

The younger, bright pulsars commonly detected by radio and X-ray telescopes are not representative of the full population of objects, so observing objects like J0108 helps astronomers see a more complete range of behavior. At its advanced age, J0108 is close to the so- called “pulsar death line,” where its pulsed radiation is expected to switch off and it will become much harder, if not impossible, to observe.

“We can now explore the properties of this pulsar in a regime where no other pulsar has been detected outside the radio range,” said co- author Oleg Kargaltsev of the University of Florida. “To understand the properties of ‘dying pulsars,’ it is important to study their radiation in X-rays. Our finding that a very old pulsar can be such an efficient X-ray emitter gives us hope to discover new nearby pulsars of this class via their X-ray emission.”

The Chandra observations were reported by Pavlov and colleagues in the January 20, 2009, issue of The Astrophysical Journal. However, the extreme nature of J0108 was not fully apparent until a new distance to it was reported on February 6 in the PhD thesis of Adam Deller from Swinburne University in Australia. The new distance is both larger and more accurate than the distance used in the Chandra paper, showing that J0108 was brighter in X-rays than previously thought.

“Suddenly this pulsar became the record holder for its ability to make X-rays,” said Pavlov, “and our result became even more interesting without us doing much extra work.” The position of the pulsar seen by Chandra in X-rays in early 2007 is slightly different from the radio position observed in early 2001. This implies that the pulsar is moving at a velocity of about 440,000 miles per hour, close to a typical value for pulsars.

Currently the pulsar is moving south from the plane of the Milky Way galaxy, but because it is moving more slowly than the escape velocity of the Galaxy, it will eventually curve back towards the plane of the Galaxy in the opposite direction.

Source: NASA

February 27, 2009December 24, 2015 by Anne Minard

Titan Dunes Turn Climate Models Upside Down

Map of dunes on Titan, with arrows indicating the general wind direction. Dark areas without arrows might have dunes but have not yet been imaged with radar. Credit: NASA/JPL/Space Science Institute (Boulder, Colorado)

Scientists have mapped vast dune fields on Titan that may align with the wind on Saturn’s biggest moon — flowing opposite the way climate models had predicted.

The maps, as above, represent four years of radar data collected by the Cassini spacecraft. They reveal rippled dunes that are generally oriented east-west, which means Titan’s winds probably blow toward the east instead of the west. If so, Titan’s surface winds blow opposite the direction suggested by previous global circulation models. On the example above, the arrows indicate the general wind direction. The dark areas without arrows might have dunes but have not yet been imaged.

“At Titan there are very few clouds, so determining which way the wind blows is not an easy thing, but by tracking the direction in which Titan’s sand dunes form, we get some insight into the global wind pattern,” says Ralph Lorenz, Cassini radar scientist at Johns Hopkins University in Maryland. “Think of the dunes sort of like a weather vane, pointing us to the direction the winds are blowing.”

Titan’s dunes are believed to be made up of hydrocarbon sand grains likely derived from organic chemicals in Titan’s smoggy skies. The dunes wrap around high terrain, which provides some idea of their height. They accumulate near the equator, and may pile up there because drier conditions allow for easy transport of the particles by the wind. Titan’s higher latitudes contain lakes and may be “wetter” with more liquid hydrocarbons, not ideal conditions for creating dunes.

“Titan’s dunes are young, dynamic features that interact with topographic obstacles and give us clues about the wind regimes,” said Jani Radebaugh, from Brigham Young University in Utah. “Winds come at these dunes from at least a couple of different directions, but then combine to create the overall dune orientation.”

Researchers say the wind pattern is important for planning future Titan explorations that might involve balloon-borne experiments. Some 16,000 dune segments were mapped out from about 20 radar images, digitized and combined to produce the new map, which is available at http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. A paper based on the new findings appeared in the Feb. 11 issue of Geophysical Research Letters.

Cassini, which launched in 1997 and is now in extended mission operations, continues to blaze its trail around the Saturn system and will visit Titan again on March 27. Seventeen Titan flybys are planned this year.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet propulsion Laboratory (JPL) in Pasadena, California manages the Cassini-Huygens mission. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

LEAD IMAGE CREDIT: NASA/JPL/Space Science Institute (Boulder, Colorado)

Source: NASA

February 27, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast: February 27 – March 1, 2009

Greetings, fellow SkyWatchers! Are you ready for the weekend? Then let’s tackle both fun and serious studies as we take on a bright open star cluster, Herschel 400 objects, lunar subjects, planets, comets and even a galaxy cluster. If you’re ready to learn more about the history behind the observing and have some fun under the stars, then just follow me…

Friday, February 27, 2009 – Today let’s celebrate the 1897 birth on this date of Bernard Lyot, master of optics. He invented the polariscope, and produced the first solar coronagraph. He also made the first motion pictures of solar prominences. Lyot was an astute observer, and realized that the lunar surface had similar properties to volcanic dust. He didn’t see canals on Mars but observed sandstorms there, as well as atmospheric conditions on other planets. The Lyot filter is well known, and so is his micrometer, a device used to make precise distance measurements, especially those between close double stars. By all accounts a wonderful and generous man, Lyot sadly died of a heart attack while returning from seeing an eclipse.

Honor Lyot’s work by studying two open clusters, found about a fist-width north of Xi Puppis. The brighter of the two – M47 (RA 07 36 36 Dec -14 29 00) – is 1,600 light-years away and a glorious object for binoculars. Filled with mixed-magnitude stars that resolve fully to aperture, M47 features the matched-magnitude double star Struve 1211 near its center. For all its bright beauty, this stellar swarm has the most ironic of histories. Probably discovered first by Hodierna but kept secret, it was independently recovered by Charles Messier, but its position was logged incorrectly. Later, it was cataloged by both William and Caroline Herschel. . .and yet again by John Herschel, who said: ‘‘This cluster has not since been observed. It is probably very loose and poor one.’’ Even Dreyer had a hard time nailing it down! Funny, considering it has only been there for 78 million years…

While M47 is a Herschel object, look just slightly north (about a field of view) to pick up another cluster that borders it, NGC 2423 (RA 07 40 45 Dec -9 09 00). This compressed cluster contains more than two dozen faint stars with a lovely golden binary at its center. By comparing the two clusters telescopically, you are also expanding your own studies by viewing two different types of stellar evolution: M47 is very similar to the Pleiades, while NGC 2423 more closely resembles the Hyades.

Saturday, February 28, 2009 – If you didn’t notice the beautiful visage of the tender young Moon and Venus last night at sunset, try again tonight. The pair will be even closer! For most observers, Venus will be only slightly more than a degree away from the Moon’s limb. Have you checked Venus’s phase in the telescope lately? Just like our own Moon, the inner planets (Mercury and Venus) have phases. Because they’re inside Earth’s orbital path, we only see a thin crescent when they first emerge from the Sun’s glare, and they become gibbous as they are about to pass behind the Sun from our point of view. That’s also the reason why we only see these two planets either after sunset or before sunrise!

Take a closer look at the slender crescent Moon. It, too, has only just emerged from the Sun’s glare, and now is the time to get a great look at two craters – Langrenus and Vendelinus. If you remember Mare Fecunditatis, you won’t have any trouble spotting Langrenus on its south shore about mid-way along the Moon’s visible limb. It’s a very old crater with an approximate diameter of 132 kilometers, and appears to binoculars as a shallow, bright ring; featuring a central peak. Further south is equally old Vendelinus. Slightly larger and spanning 147 kilometers, it will appear even more shallow – because it is. It lacks a central peak, but telescopes at high power can resolve its few minor interior craters.

Keep your binoculars or telescopes out for a while after the Moon sets, and let’s head a little less than a fist-width east-southeast of Alpha Monocerotis (RA 08 00 01 Dec -10 46 12) to check out NGC 2506. On a dark night, this nearly 7th magnitude object is one of the most impressive of the Monoceros open star clusters. Caught in a chain of stars, it displays a rich concentration, almost appearing like a globular cluster. NGC 2506 has been used to study old, metal-poor galactic clusters. Evolution has enriched its iron content, and – despite its extreme age – it is still a beauty. Be sure to mark your Hershel ‘‘400’’ notes!

Sunday, March 1, 2009 – In 1966, Venera 3 became the first craft to touch another planet when it impacted Venus on this date. Although communications failed before it could transmit data, it was still a milestone achievement. If you’re out at sunset, be sure to have a look at Venus and say “Spaseba!”

Once you’ve viewed Venus, let’s turn our observations toward tonight’s Moon and begin by identifying some prominent lunar craters around Mare Crisium that can be spotted easily with a small telescope. North you’ll spy Cleomides and at the western edge, Proclus. Near the terminator northwest is Macrobius, and southwest is Taruntius. Power up and identify the small wells of Peirce, Picard, and Lick inside the smooth sands of Crisium. Lather, rinse and repeat… The more often you repeat crater names to yourself (and aloud) the greater the chances are that you’ll retain these names in your memory. Now, let the Moon wester and we’ll go again…

In 2003, another Deep-Sky Companion book by notable observer and author Stephen O’Meara premiered. Known for his high-quality sketches of Solar System objects and uncanny observing skills, O’Meara was the first to sight Comet Halley in 1985, and sketch the dark spokes in Saturn’s rings (before Voyager had imaged them). Still part of the editorial staff at Sky & Telescope, and a treasured lecturer, let’s take just a moment to congratulate Steve on a lifetime of achievement! (folks? you will never meet a more genuinely kind person and one who treats fellow amateur astronomers with such huge respect. i have met a great many of my astronomy “heroes” over the years and steve-o is most definitely the kind of star i’d like to be some day.)

Are you ready to practice Steve’s powers of observation? Then begin with Comet Lulin – now speeding in the eastern edge of the dim constellation of Cancer. If you have difficulty finding it, look for the large, backwards question mark of the prominent asterism of Leo. The bright star you see that’s the “period” of the question mark is Regulus – and Comet Lulin is a couple of binocular fields west. Once you’ve spied it, try comparing details to what you may have observed of Lulin’s previous behavior and appearance. Is the comet moving faster than when you first began observing it? It the tail longer? Brighter? What direction does it point in? Has the coma become more diffuse or larger? Does the comet display a nucleus? Is the anti-tail still visible? Asking yourself simple questions like these will help you become a far better observer!

Now wait until Saturn has cleared the horizon murk and let’s take a close look at this fascinating planet. Look for details such as ring shadows on the planet and planet shadows on the rings. Can you see the Casinni Division? How about Saturn’s satellites? Tonight you’ll find Titan leading the way well outside to the west. To the western ring edge, you’ll see Tethys… And clustered together on the eastern ring edge are Rhea, Dione and Enceladus. You won’t need the Hubble Space Telescope to see these kinds of details – just a steady sky and around a 4″ telescope. Take your time and enjoy your studies!

Ready for some serious studies? Then let’s talk about George Abell, who was born this day in 1927. Abell was responsible for cataloging 2,712 clusters of galaxies from the Palomar sky survey, a task he completed in 1958. Using these plates, Abell proposed that the grouping of such clusters delineated the arrangement of matter in the universe. He developed the luminosity function, which shows the relationship between brightness and the number of members in each cluster, allowing you to infer the cluster’s distance. Abell also discovered planetary nebulae, and developed the theory (along with Peter Goldreich) of their evolution.

For seasoned observers, wait until the Moon has set and honor Abell by viewing one of his galaxy clusters – Abell 1367, located about a degree southwest of 93 Leonis (RA 11 44 44 Dec +19 41 59). It’s an area of challenging intrigue for a large scope – spanning a degree of sky and containing as many as two dozen small galaxies – a gemstone for the galaxy collector!

Until next week? Ask for the Moon… But keep on reaching for the stars!

This week’s awesome images are: Bernard Lyot (public image), M47 and NGC 2423 (Credit: Palomar Observatory, courtesy of Caltech), Langrenus and Vendelinus (Credit: Dave Nash), NGC 2506 (credit – Palomar Observatory, courtesy of Caltech), Crisium area (Credit: Greg Konkel), Stephen James O’Meara (Credit: Sky & Telescope), Saturn & Moons (Credit: NASA), George Abell (Credit: American Institute of Physics), Abell 1367 (Credit: Palomar Observatory, courtesy of Caltech). We thank you so much for sharing the history and mystery with us!

February 26, 2009December 24, 2015 by Nancy Atkinson

Intergalactic Dust Could Be Messing Up Observations, Calculations

Spiral galaxies seen edge-on often show dark lanes of interstellar dust blocking light from the galaxy's stars, as in this image of the galaxy NGC 4565 from the Sloan Digital Sky Survey (SDSS-II).

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“Just like household dust, cosmic dust can be a nuisance,” said astronomer Ryan Scranton of the University of California, Davis. Scranton is part of a team of researchers from the Sloan Digital Sky Survey that have been analyzing the colors of distant quasars whose light passes in the vicinity of foreground galaxies on its way to the Earth. What they found is that the vast expanses of intergalactic space appear to be filled with a haze of tiny, smoke-like “dust” particles that dim the light from distant objects and subtly change their colors. “Galaxies contain lots of dust, most of it formed in the outer regions of dying stars,” said team leader Brice Ménard of the Canadian Institute for Theoretical Astrophysics. “The surprise is that we are seeing dust hundreds of thousands of light-years outside of the galaxies, in intergalactic space.”

An implication of this finding means that since most distant supernovae are seen through some haze, our current estimates of their distances may be affected.

Dust grains block blue light more effectively than red light. “We see this when the sun sets: light rays pass through a thicker layer of the atmosphere,” said Scranton, “absorbing more and more blue light, causing the sun to appear reddened. We find similar reddening of quasars from intergalactic dust, and this reddening extends up to ten times beyond the apparent edges of the galaxies themselves.”

The team analyzed the colors of about 100,000 distant quasars located behind 20 million galaxies, using images from SDSS-II. “Putting together and analyzing this huge dataset required cutting-edge ideas from computer science and statistics,” said team member Gordon Richards of Drexel University. “Averaging over so many objects allowed us to measure an effect that is much too small to see in any individual quasar.”

Supernova explosions and “winds” from massive stars drive gas out of some galaxies, Ménard explained, and this gas may carry dust with it. Alternatively, the dust may be pushed directly by starlight.

“Our findings now provide a reference point for theoretical studies,” said Ménard.

Intergalactic dust could also affect planned cosmological experiments that use supernovae to investigate the nature of “dark energy,” a mysterious cosmic component responsible for the acceleration of the expansion of the universe.

Intergalactic dust doesn’t remove the need for dark energy to explain current supernova data, Ménard explained, but it may complicate the interpretation of future high-precision distance measurements. “These experiments are very ambitious in their goals,” said Ménard, “and subtle effects matter.”

The new findings are reported in a paper titled “Measuring the galaxy-mass and galaxy-dust correlations through magnification and reddening,” submitted to the journal Monthly Notices of the Royal Astronomical Society, and posted today on the web site arXiv.org.

Source: Sloan Digital Sky Survey

February 26, 2009December 24, 2015 by Nancy Atkinson

New Issue of Space Lifestyle Magazine Now Available

Have you heard about Space Lifestyle Magazine? It’s a digital magazine, with a full color layout just like a print magazine, but its all online. And the winter issue of Space Lifestyle Magazine is now online and available for free. SLM has feature articles about all aspects of space — NewSpace, NASA, military, science and astronomy — but mostly it’s about the people that make the space sector tick.

In the latest issue, you’ll find a bang-up article written by UT’s Ian O’Neill about SpaceX. Ian actually toured the SpaceX facility and took some great pictures and wrote a very comprehensive article about SpaceX’s recent successful launch to orbit. Other features include an interesting overview about the work being done to create magnetic shielding for spacecraft that will help repel radiation.

There’s also a feature story about South Korea’s Yecheon Astro Space Center selecting XCOR Aerospace services – specifically their Lynx Mark II suborbital vehicle – as its preferred supplier of suborbital space launch services.

There’s also a comprehensive rundown of the X PRIZE Lunar Lander Challenge competition last fall, and much more including book reviews (Death From the Sky by Phil Plait) and a special discount for the National Space Symposium to be held March 30-April 2 in Colorado Springs, Colorado. If you haven’t already “subscribed” to SLM, please do so for the chance to win a Zero-G parabolic flight and other prizes. Enjoy!

Check out Space Lifestyle Magazine.

February 25, 2009December 24, 2015 by Anne Minard

Jupiter, Saturn Plowed Through Asteroids, Study Says

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When Mars and Jupiter migrated to their present orbits around 4 billion years ago, they left scars in the asteroids belt that are still visible today.

The evidence is unveiled in a new paper in this week’s issue of the journal Nature, by planetary scientists David Minton and Renu Malhotra from the University of Arizona in Tucson.

The asteroid belt has long been known to harbor gaps, called Kirkwood gaps, in distinct locations. Some of these gaps correspond to unstable zones, where the modern-day gravitational influence of Jupiter and Saturn eject asteroids. But for the first time, Minton and Malhotra have noticed that some clearings don’t fit the bill.

“What we found was that many regions are depleted in asteroids relative to other regions, not just in the previously known Kirkwood gaps that are explained by the current planetary orbits,” Minton wrote in an email. In an editorial accompanying the paper, author Kevin Walsh added, “Qualitatively, it looks as if a snow plough were driven through the main asteroid belt, kicking out asteroids along the way and slowing to a stop at the inner edge of the belt.”

Walsh hails from the Observatoire de la Côte d’Azur in France. In his News and Views piece, he explains that the known Kirkwood gaps, discovered by Daniel Kirkwood in 1867, “correspond to the location of orbital resonances with Jupiter — that is, of orbits whose periods are integer ratios of Jupiter’s orbital period.” For example, if an asteroid orbited the Sun three times for every time Jupiter did, it would be in a 3:1 orbital resonance with the planet, he wrote. Objects in resonance with a giant planet have inherently unstable orbits, and are likely to be ejected from the solar system. When planets migrated, astronomers believe objects in resonance with them also shifted, affecting different parts of the asteroid belt at different times.

“Thus, if nothing has completely reshaped the asteroid belt since the planets settled into their current orbits, signatures of past planetary orbital migration may still remain,” Walsh wrote. And that’s exactly what Minton and Malhotra sought.

The asteroid belt easily gave up its secrets, showing the lingering evidence of planetary billiards on the inner edge of the asteroid belt and at the outer edge of each Kirkwood gap. The new finding, based on computer models, lends additional support to the theory that the giant planets — Jupiter, Saturn, Uranus and Neptune — formed twice as close to the sun as they are now and in a tighter configuration, and moved slowly outward.

“The orbit of Pluto and other Kuiper belt objects that are trapped in [orbits that resonate] with Neptune can be explained by the outward migration of Neptune,” Minton and Malhotra write in the new study. “The exchange of angular momentum between planetesimals and the four giant planets caused the orbital migration of the giant planets until the outer planetesimal disk was depleted.” Planetesimals are rocky and icy objects left over from planet formation.

“As Jupiter and Saturn migrated,” the authors continue, they wreaked havoc on the young asteroid belt, “exciting asteroids into terrestrial planet-crossing orbits, thereby greatly depleting the asteroid belt population and perhaps also causing a late heavy bombardment in the inner Solar System.”

The late heavy bombardment is proposed to have occurred about 3.9 billion years ago, or 600 million years after the birth of the Solar System, and it’s believed to account for many of the Moon’s oldest craters. Walsh said a reasonable next step, to corroborate the theory about the newly described clearings in the asteroid belt, is to link them chronologically with the bombardment.

LEAD PHOTO CAPTION: Artist’s depiction of the asteroid belt between Mars and Jupiter. Credit: David Minton and Renu Malhotra

Source: Nature

February 25, 2009December 24, 2015 by Anne Minard

Penetrating New View Into The Helix Nebula

The blue-green glow in the centre of the Helix comes from oxygen atoms shining under effects of the intense ultraviolet radiation of the 120 000 degree Celsius central star and the hot gas. Further out from the star and beyond the ring of knots, the red colour from hydrogen and nitrogen is more prominent. Cerdit: Max-Planck Society/ESO telescope at the La Silla observatory in Chile

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ESO’s La Silla Observatory has snapped a new image of the famous Helix planetary nebula, revealing a rich — and rarely photographed — background of distant galaxies.

The Helix Nebula, NGC 7293, about 700 light-years away in the constellation of Aquarius, is a Sun-like star in its final explosion before retirement as a white dwarf.

Shells of gas are blown off from the surface of such stars, often in intricate and beautiful patterns, and shine under the harsh ultraviolet radiation from the faint, hot central star. The main ring of the Helix Nebula is about two light-years across, or half the distance between the Sun and its nearest stellar neighbour.

Despite being photographically spectacular, the Helix is hard to see visually as its light is thinly spread over a large area of sky. The history of its discovery is rather obscure. It first appears in a list of new objects compiled by the German astronomer Karl Ludwig Harding in 1824. The name Helix comes from the rough corkscrew shape seen in the earlier photographs.

Although the Helix looks very much like a doughnut, studies have shown that it possibly consists of at least two separate discs with outer rings and filaments. The brighter inner disc seems to be expanding at about 100,000 km/h (about 62,000 miles/h) and to have taken about 12,000 years to form.

Because the Helix is relatively close — it covers an area of the sky about a quarter of the full Moon — it can be studied in much greater detail than most other planetary nebulae and has been found to have an unexpected and complex structure. All around the inside of the ring are small blobs, known as “cometary knots,” with faint tails extending away from the central star. Although they look tiny, each knot is about as large as our Solar System. These knots have been extensively studied, both with the ESO Very Large Telescope and with the NASA/ESA Hubble Space Telescope, but remain only partially understood. A careful look at the central part of this object reveals not only the knots, but also many remote galaxies seen right through the thinly spread glowing gas. Some of these seem to be gathered in separate galaxy groups scattered over various parts of the image.

For a sweet treat, throw a little of this into your coffee: Helix Nebula pan and zoom (video)

LEAD IMAGE CAPTION: The blue-green glow in the center of the Helix comes from oxygen atoms shining under effects of the intense ultraviolet radiation of the 120,000 degree Celsius (about 216,000 degrees F) central star and the hot gas. Further out from the star and beyond the ring of knots, the red color from hydrogen and nitrogen is more prominent. Credit: Max-Planck Society/ESO telescope at the La Silla observatory in Chile

Source: ESO