Universe Today

August 15, 2009December 24, 2015 by John Carl Villanueva

Structure of the Universe

Galaxy cluster Abell 85, seen by Chandra, left, and a model of the growth of cosmic structure when the Universe was 0.9 billion, 3.2 billion and 13.7 billion years old (now). Credit: Chandra

[/caption]The large-scale structure of the Universe is made up of voids and filaments, that can be broken down into superclusters, clusters, galaxy groups, and subsequently into galaxies. At a relatively smaller scale, we know that galaxies are made up of stars and their constituents, our own Solar System being one of them.

By understanding the hierarchical structure of things, we are able to gain a clearer visualization of the roles each individual component plays and how they fit into the larger picture. For example, if we go down to the world of the very small, we know that molecules can be chopped down into atoms; atoms into protons, electrons, and neutrons; then the protons and neutrons into quarks and so on.

But what about the very large? What is the large-scale structure of the universe? What exactly are superclusters and filaments and voids? Let’s start by looking at galaxy groupings and move on to even larger structures.

Although there are some galaxies that are found to stray away by their lonesome, most of them are actually bundled into groups and clusters. Groups are smaller, usually made up of less than 50 galaxies and can have diameters up to 6 million light-years. In fact, the group in which our Milky Way is a member of is made up of only a little over 40 galaxies.

Generally speaking, clusters are bunches of 50 to 1,000 galaxies that can have diameters of up to 2-10 megaparsecs. One very peculiar property of clusters is that the velocities of their galaxies are supposed to be too high for gravity alone to keep them bunched together … and yet they are.

The idea that dark matter exists starts at this scale of structure. Dark matter is believed to provide the gravitational force that keeps them all bunched up.

A great number of groups, clusters and individual galaxies can come together to form the next larger structure – superclusters. Superclusters are among the largest structures ever to be discovered in the universe.

The largest single structure to be identified is the Sloan Great Wall, a vast sheet of galaxies that span a length of 500 million light-years, a width of 200 million light-years and a thickness of only 15 million light-years.

Due to the limitations of today’s measuring devices, there is a maximum level to which we can zoom out. At that level, we see a universe made up of mainly two components. There are the threadlike structures known as filaments that are made up of isolated galaxies, groups, clusters and superclusters. And then there are vast empty bubbles of empty space called voids.

You can read more about structure of the universe here in Universe Today. Want to read about the cosmic void: could we be in the middle of it? We’ve also written about probing the large scale structure of the universe.

There’s more about it at NASA. Here are a couple of sources there:

Here are two episodes at Astronomy Cast that you might want to check out as well:

Sources: NASA WMAP, NASA: Sheets and Voids

August 14, 2009December 24, 2015 by Nancy Atkinson

Ares I-X Fully Stacked

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For the first time in more than a quarter-century, a new space vehicle stands ready in NASA’s Vehicle Assembly Building. But will it fly without violent vibrations, and what verdict will the Augustine Commission give the Constellation program? Only time will tell, but for now the Ares I-X is at its fully assembled height of 100 meters (327 feet) and is one of the largest rockets ever put together in the VAB’s High Bay 3. Ares I-X rivals the height of the Apollo Program’s 364-foot-tall Saturn V. The Ares I-X flight test currently is targeted for Oct. 31. Ares I-X consists of a four-segment first stage solid rocket motor, and a simulated upper stage that represents the weight and shape of the Ares 1 rocket and Orion crew vehicle. It will be launched in a suborbital arc into the Atlantic to collect data on its flight dynamics and parachute recovery performance.

The flight of the unpiloted Ares I-X will be an important step in confirming that the rocket design is safe and stable in flight before piloted flights of Ares I begin in the middle of the next decade.

But — even before the launch of Ares I-X — a critical series of ground tests will take place to confirm that the vehicle’s dynamic response will respond to launch loads and vibrations the way that computer analytical models have predicted it will respond.

“While we are confident in the predicted model results and simulations, these ground tests are critical because we have no experience launching rockets as long and slender as Ares I-X,” according to Paul Bartolotta, Ares I-X Modal Test Lead who is responsible for leading a NASA-wide Modal Test Team from his office at NASA’s Glenn Research Center, Cleveland, Ohio.

Saturn V, Ares I-X and Delta IV. Credit: NASA

With its height and average diameter of approximately 4 meters (14 feet), Ares I-X has a high “slenderness ratio” compared to other launch vehicles. The similarly-shaped Delta IV, for instance, is about 5.2 meters (17 feet) in average diameter and 69 meters (225 feet) long. The Saturn V was about 10 meters (33 feet) in average diameter and 111 (363 feet) in length.

Due to its long slender shape, the Ares I-X is unique from a flight dynamics standpoint.

“We’re going to be shaking the vehicle to make sure our structural models match the actual vehicle characteristics,” said Kurt Detweiler, Ares I-X Lead Systems Engineer, based at NASA Langley. “This is important for determining how the vehicle will respond during flight. If the vehicle doesn’t match the analytical model, its guidance, navigation and control systems will be off,” he added.

A series of sensors strategically located throughout the stacks will measure the amount and direction of movement, as the shakers impose random loads to determine the rocket segment’s first several bending modes. A comparison will be made between predicted and measured mode shapes to verify the Ares I-X flight dynamics model.

Sources: NASA on Facebook, NASA

August 14, 2009December 24, 2015 by Nancy Atkinson

Planck Starts Collecting Light Left Over From Big Bang

Artists concept of the Planck spacecraft. Credit: JPL

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As of August 13, 2009, the Planck mission is officially in business. It is now seeing light billions of years old, left over from the Big Bang. From its location in the L2 point, the spacecraft started collecting science data as part of the “First Light Survey” which is intended to check out all the systems. If all goes as planned, these observations will be the first of 15 or more months of data gathered from two full-sky scans.

Researcher Chris North wrote on the Planck website that “the major science results will take quite a while to come out due to the immense amount of computation needed to analyse them, and are expected in around 3 years’ time. These results will be a full-sky map of the Cosmic Microwave Background, and more accurate measurements of the parameters which have governed how our Universe has evolved.”

The mission, which is led by the European Space Agency with important participation from NASA, will help answer the most fundamental of questions: How did space itself pop into existence and expand to become the universe we live in today? The answer is hidden in ancient light, called the cosmic microwave background, which has traveled more than 13 billion years to reach us. Planck will measure tiny variations in this light with the best precision to date.

After the 15 month prime mission, Planck will continue to scan the sky until its coolant runs out.

For more on Planck, check out these websites:

Cardiff University’s Planck website
ESA’s Planck Website
NASA’s Planck website
Planck Blog

August 14, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – August 14-16, 2009

Greetings, fellow SkyWatchers! Have you had a wonderful week chasing the Perseid Meteor shower? Well, the show isn’t over yet. Enjoy this weekend’s darker skies and keep watching! While you’re out, why not take a pair of binoculars with you and do a little cluster hunting? If you’re feeling energetic – take out the telescope and resolve them. Who knows what you might learn if you listen to what’s out there… Things like where to find chemically peculiar stars – or a runaway black hole! It’s all waiting for you in the night….

Friday, August 14, 2009 – If you were up well before dawn this morning watching the Perseids, did you notice the Pleiades brushing by the Moon? What a lovely sight! I wonder if it was an occultation event somewhere?

Tonight let’s venture about three finger-widths northeast of Lambda Sagittarii to visit a well known but little visited galactic cluster—M25 (RA 18 31 42 Dec -19 07 00). Discovered by Cheseaux and then cataloged by Messier, it was observed and recorded by William Herschel, Johann Elert Bode, Admiral Smythe, and T.W.Webb but never added to the NGC catalog of John Herschel! Thanks to J.L.E. Dreyer, it did make the second Index Catalog as IC 4725.

M25 is seen even with the slightest optical aid, and this 5th magnitude cluster contains two G-type giants as well as a Delta Cephei-type variable with the designation of U, which changes about 1 magnitude in a period of less than a week. It’s very old for an open cluster, perhaps near 90 million years, and the light you see tonight left the cluster over 2,000 years ago. Although binoculars will see about a double handful of bright stars overlying fainter members, telescopes will reveal more and more as aperture increases. At one time it was believed to have only about 30 members, but this was later revised to 86. But recent studies by Archinal and Hynes indicate it may have as many as 601 member stars!

Saturday, August 15, 2009 – On this date in 2006, Voyager 1, the most distant manmade object, reached 100 astronomical units (AUs) from the Sun—meaning 100 times more distant from the Sun than Earth—about 15,000 million kilometers (9,300 million miles). Voyager 1 continues traveling at a rate of about a million miles per day and could cross into interstellar space within 10 years. What fanastic sights do you think it is seeing?

Tonight we’ll head toward the riches of Scorpius to have a look at three pristine open clusters. Begin your starhop at the colorful southern Zeta pair and head north less than 1 degree for NGC 6231 (RA 16 54 08 Dec -41 49 36).

Wonderfully bright in binoculars and well resolved in the telescope, this tight-open cluster was discovered by Hodierna before 1654. De Cheseaux cataloged it as object 9, Lacaille as II.13, Dunlop as 499, Melotte as 153, and Collinder as 315. No matter what catalog number you choose to put in your notes, you’ll find the 3.2-million-year young cluster shining as the ‘‘Northern Jewelbox!’’ For high power fans, look for the brightest star in this group, called van den Bos 1833, a
splendid binary.

About another degree north is the loose open cluster Collinder 316, with its stars scattered widely across the sky. Caught on its eastern edge is another cluster known as Trumpler 24, a site where new variables might be found. This entire region is encased in a faint emission nebula called IC 4628, making this low-power journey through southern Scorpius a red-hot summer treat!

Sunday, August 16, 2009 – Before dawn, look for the close pair of Mars and the Moon celebrating the 1744 birth on this date of Pierre Mechain! We know Mechain as Charles Messier’s assistant, but Mechain was himself a fine astronomer and mathematical prodigy. He discovered 11 comets, and provided 26 entries to Messier’s catalog. If he were alive today, Pierre would be eager to join us tonight for our studies.

Begin about a degree and a half south of twin Nu Scorpii for NGC 6242 (RA 16 55 36 Dec -39 28 00).

Discovered by Lacaille and cataloged as I.4, this object is also known as Dunlop 520, Melotte 155, and Collinder 317. At roughly magnitude 6, this open cluster is within binocular range but truly needs a telescope to appreciate its fainter stars. Although NGC 6242 might seem like nothing more than a pretty little cluster with a bright double star, it contains an X-ray binary that is a ‘‘runaway’’ black hole, surmised to have formed near the galactic center and vaulted into an eccentric orbit when the progenitor star exploded. Its kinetic energy is much like that of a neutron star or a millisecond pulsar, and it was the first black hole confirmed to be in motion.

Now head a little more than a degree east-southeast for NGC 6268 (RA 17 02 40 Dec -39 44 18).

At a rough magnitude of 9, this small open cluster can be easily observed in smaller scopes and resolved in larger ones. NGC 6268 itself is somewhat lopsided, with more of its members clustered near its western border. Although it, too, might not seem particularly interesting, this young cluster is highly evolved and contains some magnetic, chemically peculiar stars; it has some Be-class, or metal weak, members as well.

Until next week? Keep on yelling when the Perseids fly over! I’m sure St. Lawrence would approve…

This week’s awesome images are (in order of appearance): M25 (credit—Palomar Observatory, courtesy of Caltech), Voyager 1 (credit—NASA), NGC 6231, NGC 6242 and NGC 6268 (credit—Palomar Observatory, courtesy of Caltech). We thank you so much!

August 14, 2009December 24, 2015 by Nancy Atkinson

Found: Planetary Nebula Around Heavy Stars

An optical image from the 0.6-m University of Michigan/CTIO Curtis Schmidt telescope of the brightest Radio Planetary Nebula in the Small Magellanic Cloud, JD 04. The inset box shows a portion of this image overlaid with radio contours from the Australia Telescope Compact Array. The planetary nebula is a glowing record of the final death throes of the star. (Optical images are courtesy of the Magellanic Cloud Emission Line Survey (MCELS) team).

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Planetary nebula – the glowing gaseous shells thrown off by stars during the latter stages of their evolution – were thought to only form around stars the size of our Sun or smaller. Although astronomers had predicted these shells should form around “heavier” stars, none had ever been detected. Until now. An international team of scientists have discovered a new class of object which they call “Super Planetary Nebulae,” found around stars up to 8 times the mass of the Sun.

“This came as a shock to us,” said Miroslav Filipovic from the University of Western Sydney “as no one expected to detect these object at radio wavelengths and with the present generation of radio telescopes. We have been holding up our findings for some 3 years until we were 100% sure that they are indeed Planetary Nebulae”.

The team surveyed the Magellanic Clouds, the two companion galaxies to the Milky Way, with radio telescopes of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Australia Telescope National Facility. They noticed that 15 radio objects in the Clouds match with well known planetary nebulae observed by optical telescopes.

The new class of objects are unusually strong radio sources and are associated with larger original stars (progenitors), up to 8 times the mass of the Sun. The nebular material around each star may have as much as 2.6 times the mass of the Sun.

Filipovic’s team argues that the detections of these new objects may help to solve the so called “missing mass problem” – the absence of planetary nebulae around central stars that were originally 1 to 8 times the mass of the Sun. Up to now most known planetary nebulae have central stars and surrounding nebulae with respectively only about 0.6 and 0.3 times the mass of the Sun but none have been detected around more massive stars.

Some of the 15 newly discovered planetary nebulae in the Magellanic Clouds are 3 times more luminous than any of their Milky Way cousins. But to see them in greater detail astronomers will need the power of a coming radio telescope – the Square Kilometre Array planned for the deserts of Western Australia.

The scientist’s paper appears in the journal Monthly Notices of the Royal Astronomical Society.

Lead image caption: An optical image from the 0.6-m University of Michigan/CTIO Curtis Schmidt telescope of the brightest Radio Planetary Nebula in the Small Magellanic Cloud, JD 04. The inset box shows a portion of this image overlaid with radio contours from the Australia Telescope Compact Array. The planetary nebula is a glowing record of the final death throes of the star. (Optical images are courtesy of the Magellanic Cloud Emission Line Survey (MCELS) team).

Source: RAS

August 13, 2009December 24, 2015 by Nancy Atkinson

Hunt for Supernovae With Galaxy Zoo

How would you like to find a supernova? I can’t think of anyone who wouldn’t be proud to say they have spotted an exploding star. And now, perhaps you can – and without all the work of setting up your telescope and staying up all night (well, that can be fun, too, but…). The great folks who brought you Galaxy Zoo have now partnered with the Palomar Transient Factory to offer the public a chance to hunt and click for supernovae from the comfort of your own computer. And yes, you can still classify galaxies at Galaxy Zoo, but now you can search for for the big guns out in space, too. Sound like fun?

The Palomar Transient Facory uses the famous Palomar Observatory and the Samuel Oschin 1.2 m telescope to look for anything that’s changing in the sky — whether it’s a variable star, an asteroid moving across the sky, the flickering of an active galaxy’s nucleus or a supernova. For now, though, the partnership with Galaxy Zoo will concentrate on finding supernovae, and in particular Type 1A supernovae.

According to Scott Kardel of the Palomar Observatory, “the quantity and quality of the new data that’s been coming in are absolutely mind blowing for astronomers working in this field. On one recent night PTF patrolled a section of the sky about five times the size of the Big Dipper and found eleven new objects.” For the supernova search, it returns to the same galaxies twice a night, every five nights.

That’s where the Zooites from Galaxy Zoo come in: searching through all specially chosen PTF data and looking for supernovae.

“Your task is to search through the candidates found by PTF” said the Galaxy Zoo team. “Waiting for your results are two intrepid Oxford astronomers, Mark and Sarah, who have travelled out to the Roque de los Muchachos Observatory on the Canary Island of La Palma. They have time allocated on the 4.2m William Herschel Telescope to follow up the best of our discoveries.”

Check out Galaxy Zoo’s Supernova page for more info and to sign up to be part of this exciting new Citizen Science project!

For more info on the Palomar Transient Factory, listen to Scott Kardel’s 365 Days of Astronomy podcast.

August 13, 2009December 24, 2015 by Nancy Atkinson

Naked Saturn

Saturn on August 12, 2009 just after equinox. Credit: NASA

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Here’s one of the first raw images of Saturn taken by the Cassini spacecraft just after equinox, on August 12, 2009. The planet sure looks naked without its rings! But not to fear, the rings are still there; we just can’t see them very well — only a thin line. That’s because the sun was shining directly straight-on at the rings at Saturn’s equinox, and the spacecraft was in the right place, too. Equinox occurs every half-Saturn-year which is equivalent to about 15 Earth years. The illumination geometry that accompanies equinox lowers the sun’s angle to the ringplane and causes out-of-plane structures and some moons to cast long shadows across the rings. The ring shadows themselves have become a rapidly narrowing band cast onto the planet. Below, see another image with the rings visible as the spacecraft changed its angle.

Check out more raw images from the equinox here.

August 13, 2009December 24, 2015 by Tammy Plotner

IYA Live Telescope Today: Delta Gruis and the “Tarantula Nebula”

Hey, folks! What a treat. The skies were clear and dark in central Victoria earlier and the beautiful double star – Delta Gruis – came out to play. Afterwards we homed in on the incredibly bright Tarantula Nebula. While you’re at it, you might want to update your bookmarks to this IYA Live Telescope link. Now… Go and look at our new video! Once in awhile you can even see other portions the Magellanic Cloud in there, too!

The stars that form Grus were originally considered part of Piscis Austrinus (the southern fish), and the Arabic names of many of its stars reflect this classification.

The stars were first defined as a separate constellation by Petrus Plancius, who created twelve new constellations based on the observations of Pieter Dirkszoon Keyser and Frederick de Houtman. Grus first appeared on a 35-cm diameter celestial globe published in 1597 (or 1598) in Amsterdam by Plancius with Jodocus Hondius. Its first depiction in a celestial atlas was in Johann Bayer’s Uranometria of 1603. Plancius chose the crane because that bird was considered to symbolise watchfulness. An alternative name for the constellation, Phoenicopterus (Latin for flamingo), was used briefly in England during the 17th century.

Now that it’s good and dark and we’ve got a bit before the Moon, let’s take a look at something even more fantastic… the Tarantula Nebula!

The Tarantula Nebula (also known as 30 Doradus, or NGC 2070) is an H II region in the Large Magellanic Cloud. It was originally thought to be a star, but in 1751 Nicolas Louis de Lacaille recognized its nebular nature.

The Tarantula Nebula has an apparent magnitude of 8. Considering its distance of about 180,000 light years, this is an extremely luminous non-stellar object. Its luminosity is so great that if it were as close to Earth as the Orion Nebula, the Tarantula Nebula would cast shadows. In fact, it is the most active starburst region known in the Local Group of galaxies. It is also the largest and most active such region in the Local Group with an estimated diameter of 200 pc.

The nebula resides on the leading edge of the LMC, where ram pressure stripping, and the compression of the interstellar medium
likely resulting from this, is at a maximum. At its core lies the extremely compact cluster of stars (~2.5 pc diameter) – R136a – that produces most of the energy that makes the nebula visible. The estimated mass of the cluster is 450,000 solar masses, suggesting it will likely become a globular cluster in future.

In addition to R136, the Tarantula Nebula also contains an older star cluster—catalogued as Hodge 301—with an age of 20–25 million years. The most massive stars of this cluster have already exploded in supernovae. The closest supernova since the invention of the telescope, Supernova 1987A, occurred in the outskirts of the Tarantula Nebula.

As always, check back periodically on the IYA “Live” telescope. It can’t be cloudy forever!

Factual Information Source: Wikipedia

August 13, 2009December 24, 2015 by Nancy Atkinson

This Week’s WITU Challenge

I’m a day late (sorry!) but here’s this week’s image for the Where In The Universe Challenge, to test your visual knowledge of the cosmos. You know what to do: take a look at this image and see if you can determine where in the universe this image is from; give yourself extra points if you can name the spacecraft responsible for the image. We’ll provide the image today, but won’t reveal the answer until tomorrow. This gives you a chance to mull over the image and provide your answer/guess in the comment section. Please, no links or extensive explanations of what you think this is — give everyone the chance to guess.

UPDATE: The answer has now been posted below.

This is a dust devil on Mars, captured by the HiRISE camera on the Mars Reconnaissance Orbiter. The white mass is a swirling vortex of dust, and the darker line is a shadow cast by this swirling column of dust. This image is from some of the newest releases by HiRISE, see them all here. Find out more about this particular image here.

Check back next week for another WITU challenge!

August 13, 2009December 24, 2015 by Nancy Atkinson

NASA Doesn’t Receive Enough Money for Mandated Asteroid Search

Planet Killer — Artist's conception of an asteroid hitting Earth.

In 2005, the US Congress mandated that NASA discover 90 percent of all near-Earth objects 140 meters in diameter or greater by 2020. But they forgot one minor detail: Congress or the administration did not request or appropriate any new funds to meet this objective, and with NASA’s existing budget, there is no way NASA can meet the mandated goal.

Does anyone else see a pattern here?

“For the first time, humanity has the capacity and the audacity to avoid a natural disaster,” says Irwin Shapiro of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., who headed a National Research Council panel to asses NASA’s progress in reaching the asteroid detection goal . “It really is a question of how much to invest in an insurance policy for the planet.”

NASA was also directed by the Bush administration to build spacecraft to return to the Moon, and perhaps go on to Mars, but do the job (as well as complete the space station and make sure the shuttles can fly safely) with no real increase in budget.

From the report:

Currently, the U.S. government spends a relatively small amount of money funding a search and survey program to discover and track near-Earth objects, and virtually no money on studying methods of mitigating the hazards posed by such objects. Although Congress has mandated that NASA conduct this survey program and has established goals for the program, neither Congress nor the administration has sought to fund it with new appropriations. As a result, NASA has supported this activity by taking funds from other programs, while still leaving a substantial gap between the goals established by Congress and the funds needed to achieve them.

The report is available here (download the free pdf version)

But in summary, the report says that since only limited facilities are currently involved in the asteroid survey/discovery effort, NASA cannot meet the goals of the Congressional mandate on the existing budget. Instead, the three current survey efforts dedicated to the problem, supported at current levels, will likely find only about 15%.

The report also says that Harvard-Smithsonian’s Minor Planet Center is more than capable of handling the observations of the congressionally mandated survey, but there isn’t enough funds for adequate staffing.

If this is true, the facilities to do the job appear to be in place, and no new observatories need to be built or spacecraft need to be launched. How much more money would it take to hire enough people?

However, only three surveys are currently involved in the search (Catalina Sky Survey, Spacewatch and Lincoln Near Earth Asteroid Research), and the panel suggests that more telescopes and spacecraft would be beneficial to the search. Several ground-based telescopes have been proposed or are currently under development that could contribute substantially to meeting the goal established by Congress. However, none has yet been fully funded, nor principally dedicated to the NEO discovery goal.

Right now, the US is the only country that currently has an operating survey/detection program for discovering near-Earth objects. Canada and Germany are both building spacecraft that may contribute to the discovery of near-Earth objects, but neither mission will detect fainter or smaller objects than ground-based telescopes.

But the US isn’t alone in the non-funding of asteroid searches. “Virtually no international funds are spent supporting ground-based NEO surveys, and international NEO discovery efforts are largely conducted on an ad hoc, voluntary, or amateur basis. NASA is the agency that has funded more than 97 percent of the discoveries of NEOs in the last decade,” says the report.

Sources: USA Today, National Acadamies Press