Sunspot Pair Observed Today – Is Solar Cycle 24 Waking Up?

The August 21st sunspots as observed from Slovakia (© Pavol Rapavy)

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Amateur astronomers have observed the first sunspots to appear on the solar surface for weeks. This period of extreme magnetic calm has made some scientists believe that Solar Cycle 23 might be a quiet affair. This comes in stark contrast to NASA’s 2006 forecast that this cycle would be a “doozy.” Whether or not the slow start of solar activity is indicative of things to come, we’re not sure, but it sure is great to see activity starting to churn on the solar surface once more…

The sunspots as observed in the UK (© Pete Lawrence)
The sunspots as observed in the UK (© Pete Lawrence)

Ever since the official beginning of Solar Cycle 24 at the start of the year, when a sunspot pair was observed with opposite magnetic polarity to spots in the previous cycle, we have been (im)patiently watching the solar disk for activity. In a 2006 article, NASA had already gotten us excited that Cycle 24 would be more active than the previous cycle (a record breaker in itself), but after that first observed spot in January, nothing. By June, even seasoned solar physicists were hinting at their concerns for the lack of activity. “It continues to be dead. That’s a small concern, a very small concern,” said Saku Tsuneta, program manager for the Hinode mission and Japanese solar physics heavyweight at a June conference. Although nobody seriously hinted that this cycle was going to continue to be dead for the whole cycle, there was some confusion about the nature of our Sun.

To make the situation even more cloudy, back in March, we had a false alarm. Suddenly, the Sun erupted to life, only three months after the start of Cycle 24 was announced. Sunspots, flares and Coronal Mass Ejections sprung to life around the solar equator. You would have been forgiven for thinking the Sun was going to make good on the NASA 2006 forecast. But it wasn’t to be. Critically, these active sunspots were “left overs” from the previous cycle. Like revellers turning up an hour after the party had finished, these sunspots were overlapping remainders of the previous cycle.

At the root of all these observations is space weather prediction. All our activities in space are in some way influenced by solar activity, so it would be advantageous if we could predict when the next solar storm is coming. We have complex models of the Sun and our observational skills are becoming more and more sophisticated, but we still have a very basic grasp on what makes the Sun “tick.”

So today’s discovery, although a little overdue, will excite solar physicists and astronomers the world over. But will the solar activity continue? Is this just an isolated occurrence? For now, we just do not know. We have to sit back, observe and enjoy what surprises the Sun has in store for us in Cycle 24.

Original source: Space Weather

Real Hitchhiker’s Guide to the Solar System on the Way

A NASA image of asteroid Eros (left) and Robert Gaskell's shape model of the asteroid (right). Credit: PSI

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Thinking about trekking across Titan or meandering around Mercury? Along with your backpack and towel, you’ll also want to pack one of Robert Gaskell’s maps. Gaskell, a senior scientist at the Planetary Science Institute, is working on creating real hitchhiking guides to the various bodies in our solar system. He’s been equated to the final frontier what Lewis and Clark were to the American West – the guy producing the most accurate and detailed maps available. And thanks to current space missions sending back loads of data, Gaskell is beginning to work on creating precise maps of Mercury, the asteroid Eros, and eight moons of Saturn including Enceladus. Gaskell has created sophisticated software that combines hundreds of spacecraft images of varying resolution to create the maps. He’s been developing the software for nearly 25 years, and if you want to map a planet, moon, or asteroid, he’s the guy to ask.

Gaskell uses a method called stereo-photo-clinometry, or SPC. Just as stereo-phonic means sound from different directions, stereo-photo means light from different directions, and clinometry means that slopes, or inclines, are being measured. So SPC means finding slopes from the way the surface looks under different illuminations, and once we know the slopes we can find the heights.

Four computers in Gaskell’s office grind out mapping data nearly 24/7. But despite his quarter century of mapping work, Gaskell says he’s just getting started. “There are thousands of objects in the solar system, and so far, I’ve barely scratched the surface, if you’ll pardon the expression,” he said.

Gaskell has won an NASA Exceptional Achievement medal for his detailed maps of the asteroid Itokawa.

Robert Gaskell.  Credit:  PSI
Robert Gaskell. Credit: PSI

His newest project will create highly accurate maps of the entire surface of Mercury based on images sent back by NASA’s MESSENGER spacecraft. MESSENGER flew by Mercury in January and will fly by again in October before going into orbit of Mercury in 2011.

Currently Gaskell is combining images from the January flyby with those taken by Mariner 10, which visited Mercury in 1973, to produce initial maps. But the sun angle for the Mariner 10 photos was the same for three flybys and so far there is only one flyby for MESSENGER.

“It won’t be until we get overlapping data from different sun directions that it will really start making a lot of sense,” Gaskell said. “It does give a reasonable solution now, but I don’t completely trust it.”

Gaskell’s maps not only give scientists useful information about a body’s surface, they also can be used for navigating spacecraft, calibrating spacecraft instruments, and gaining information about the geology, internal structure and past history of an object.

In addition to Mercury, Gaskell is mapping eight of Saturn’s moons, including Enceladus, a frigid world punctuated by icy geysers. In October, NASA may use those maps as navigational tools to plot – and possibly adjust – the Cassini spacecraft’s trajectory as it flies past Enceladus.

Once Gaskell’s computers produce maps covering an entire body, they yield a very accurate image of the object’s shape. The moons of Saturn, for instance, have changed orbits during their history and gravitationally interact with one another. Once their shape became fixed, it recorded the tidal stresses at the time they froze, which gives scientists a way of determining the orbital history of the system.

For Io, Jupiter’s highly volcanic moon, mapping its shape provides planetary geologists with part of the data they need to determine what processes may be going on inside its fluid core, which is being heavily torqued by the giant planet’s intense gravitational field.

Describing himself as an evangelical stereo-photo-clinometrist, he is sharing his work with others and recruiting more researchers into the long-term effort to map the solar system. Some of those are at the Jet Propulsion Laboratory, The University of Arizona, the Johns Hopkins Applied Physics Laboratory, and USGS.

With so many planets, moons and asteroids to explore and map, “It’s like being in a big candy shop,” Gaskell said.

Source: Planetary Science Institute

Sloan Digital Sky Survey: Changing How Scientists – and the Public – Do Astronomy

The 2.5 meter SDSS telescope at Apache Point Observatory in New Mexico. Credit: SDSS

Recently we’ve had articles on Universe Today that have discussed the outer Milky Way Galaxy, dark matter, and the discovery of a new minor planet. These articles have a common thread: The discoveries all come from the Sloan Digital Sky Survey (SDSS). If you aren’t familiar with SDSS, it encompasses a comprehensive survey lasting more than eight years, which has so far covered more than one-quarter of the sky.

Using a dedicated 2.5 meter telescope equipped with a 125- megapixel digital camera and spectrographs that can observe 640 stars and galaxies at a time, the SDSS has created terabytes of data that include thousands of deep, multi-color images. It’s also measured the distances to nearly one million galaxies and over 100,000 quasars to create the largest ever three-dimensional maps of cosmic structure.

The SDSS archive represents a thousand-fold increase in the total amount of data that astronomers have collected to date. But almost equally impressive is the easy-to-use interface that allows anyone in the world to access the SDSS data online. Whether you are a research astronomer looking for information to help solve a cosmological puzzle or an armchair astronomy enthusiast who just likes looking at pretty pictures of the universe, SDSS is at your disposal.

Astronomers gathered in Chicago earlier this week to celebrate the accomplishments and look ahead to the future of SDSS. “What amazes me is the huge range of the discoveries that have come from SDSS data,” said SDSS-II Director Richard Kron, an astronomer at the University of Chicago and Fermilab. “We designed it primarily as a survey to map the distribution of galaxies and quasars, but it’s also had a huge impact on the study of stars, the structure of our own Galaxy, and even solar system objects.”

SDSS has found new dwarf companion galaxies to the Milky Way, confirmed Einstein’s prediction of cosmic magnification, and observed the largest known structures in the universe. The new survey, SDSS-III, will continue to expand our horizons with new studies of the structure and origins of the Milky Way Galaxy and the nature of dark energy.

SDSS was undertaken to update the database of information about the sky with current technology. The previous comprehensive guide to the heavens was the Palomar Sky Survey that was conducted in the 1950’s and used glass photographic plates to store the data.

Not only has SDSS updated the technology, but it has changed the way astronomers do business. Astronomers who are doing research or have a question can look at the existing data in SDSS rather than having to pore through the sky, taking their own data with hard-to-get telescope time.

Dr. Pamela Gay, professor at Southern Illinois University Edwardsville and host of the Astronomy Cast podcast said SDSS not only helps her research, but enhances her work in the classroom. “It’s a wonderful project,” she said. “I’m at a small state university and while I did my dissertation on galaxies, when I landed at a state school, I thought I’d never be able to do this (study galaxies) again because I don’t have access to a large telescope. But because of the Sloan Digital Sky Survey, and because of the easy to use tools where I can say to my undergraduate students, ‘go find all the data on these clusters,’ it’s possible for people at small schools to do amazing, amazing research and explore the entire universe.”

SDSS also powers the popular Galaxy Zoo website, where anyone in the world can help classify galaxies via the internet. From the work done by the public from their home computers, Galaxy Zoo has submitted peer reviewed research articles to astronomical journals.

Visit the SDSS website to take a look at the images and discoveries made possible by this comprehensive survey. The Sky Server interface on the SDSS website provides the tools you need to start perusing the universe, and has educational activities for teachers and students as well.

Jim Gunn, SDSS Project Scientist from Princeton University, who has guided the project since its inception said that more than any single discovery, he is proud of the quality and scope of the SDSS data sets. “Visible light is where we understand the universe best, but when we began the SDSS, there were no sensitive, well characterized, visible-light catalogs that covered a large area of sky,” he said. “Now we have multi-color images of 300 million celestial objects, 3-dimensional maps and detailed properties of well over a million of them, and it’s all publicly available online. That changes everything.”

Phoenix Lander: The Digging Continues

This mosaic of images shows the Phoenix worksite. Credit: NASA/JPL/Caltech/U of Arizona

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Scientists and engineers from NASA’s Phoenix Mars Lander continue with digging operations around the lander with the spacecraft’s robotic arm. They are looking for new materials to analyze and are examining the soil and ice subsurface structure. “We expect to use the robotic arm heavily over the next several weeks, delivering samples to our instruments and examining trench floors and walls to continue to search for evidence of lateral and vertical variations in soil and ice structures,” said Ray Arvidson, Phoenix’s “dig czar,” from Washington University in St. Louis. New trenches opened recently and shown in the image here include the “Burn Alive 3” trench in the eastern portion of the arm’s reachable workspace.

The team is excavating one side of this trench down to the ice layer and plans to leave about 1 centimeter (0.4 inch) of soil above the ice on the other side. From this intermediate depth is where scientists hope to test a sample of soil in Phoenix’s Thermal and Evolved Gas Analyzer (TEGA).

Near the western end of the arm’s workspace, the team plans to dig as deep as possible in the “Cupboard” excavation area to study properties of the soil and ice in one of the polygon trough areas. Like on Earth, the polygon patterns form in areas of permafrost that goes through cycles of swelling and shrinking as the ground thaws and refreezes.

A sample from the Cupboard area may be delivered to the lander’s wet chemistry lab, part of the Microscopy, Electrochemistry and Conductivity Analyzer (MECA) to test for the presence of salts. In addition, the robotic arm will try to acquire ice-rich soil from “Upper Cupboard” and observe the material in the arm’s scoop to determine whether the sample sublimates. Melting is an indication of the presence of salt. If the sample melts and leaves behind a salty deposit, “Upper Cupboard” would be the location for the next sample for the wet chemistry lab. If no salts are detected, the team would
continue with plans to use the “Stone Soup” trench for acquiring the next wet chemistry lab sample.

If you’re wondering about the interesting names of the different areas, the team names the areas and trenches to make identification easier (instead of saying something like “that trench in the upper left corner of the image taken on Sol 45.”) The names are chosen from various fairy tales and myths.

A change has taken place for the scientists and engineers working with Phoenix. They are now working on Earth time instead of Mars time. This eliminates the constantly transitioning work period as a Mars sol is about 40 minutes longer than an Earth day. Undoubtedly, this has to make their lives much easier, instead of juggling their Earth life and Mars work every day.

Daily activities are being planned for the spacecraft as the lander performs activities that were sent up the previous day. Digging and documenting are done on alternate days to allow the science team time to analyze data and adjust activities accordingly.

In upcoming sols, the team plans to scrape the “Snow White” trench and experiment with acquiring and holding samples in the shade versus the sun. They want to find out if prolonged exposure to sunlight causes the acquired material to stick to the scoop, as has occurred with previous samples.

Source: Phoenix News site

The TeleVue Plossl – Unsung Eyepiece Hero

If you’re into telescopy, then you know the name Televue needs little or no introduction at all. The name is absolutely synonymous with the most outstanding quality and high performance optics in the business and every product is backed by uncompromising standards. Of course, if you’re like me, the moment I see the name Televue little dollar signs start swimming around in front of my eyes. Would you like me to shoo them away for you?

I’ve been playing the astronomy game for a long time now and I know when it comes to optics that you get what you pay for. But, one of my favorite things to do is to find products that give you more than what you expect. Go anywhere. Look any place. Check out plossl eyepieces. The four element Plossl design is perhaps the most popular telescope eyepiece design on today’s market and just about every manufacturer makes one. It provides excellent image quality, good eye relief and just about all of them have an apparent field of view of about 50 degrees. But is one plossl really better than another?

The answer is yes. And here’s why…

The names TeleVue and Al Nagler are synonymous among the international astronomy community with revolutionary telescope and eyepiece designs in production since 1977. Beginning his career with amateur astronomy and telescope making, Mr. Nagler enjoyed an illustrious career in optics and eventually became involved in the design of the NASA Apollo program astronaut lunar landing visual simulator by designing a probe which simulated a field of up to 140 degrees! Establishing TeleVue Optics Incorporated in 1977, Uncle Al’s mind eventually turned to a field which hadn’t progressed in nearly a century – telescope eyepiece designs – and thus was born a legend. Says Mr. Nagler in his Company 7 interview: “I have worked on eyepieces, telescopes and viewing devices with two major goals: to make astronomy as easy and versatile as possible to encourage, rather than discourage, newcomers, and secondly, to provide a visual experience as close to a “space walk” as possible by obtaining the widest, sharpest, highest contrast views. I am deeply gratified that my work has enhanced the pleasure and growth of the hobby.”

Televue demands a certain standard that can and will be met – and nothing says it more clearly than their very affordable line of Televue Plossl Eyepieces. At right around $100 per eyepiece, this is not only competitive with other manufacturers – it’s meeting their price point and delivering far better performance. In a side by side comparison with a 2″ Meade 26mm QX Wide Angle Eyepiece which supposedly offers a 70 degree field of view, the 1.25″ Televue 25mm Plossl absolutely buried it. Why? By all design rights, the QX should have outperformed it – yet it did not. Telescope after telescope, focal length after focal length… The results were the same. The Televue Plossl consistently gave outstandingly better edge of eyepiece performance, far more contrast and sharper images.

Now for a 1.25″ Celestron 12mm Omni Plossl compared to a 1.25″ Televue 11mm Plossl. Again, we have near dead-ringers in design, magnification, field of view and eye relief – but not performance. Putting in the Televue Plossl was like the different between day and night. Contrast improved significantly and image sharpness doubled. When Jupiter would near the edge of the eyepiece field, it didn’t distort! Telescope after telescope… Focal length after focal length… Same results.

Did I spend several evenings switching out eyepieces? Yes. Refractor, reflector and SCT… I went through a very serious collection of eyepieces that ranged from Antares to William Optics and I am very impressed with what these very affordable plossl eyepieces can do. Before anyone even considers buying a plossl eyepiece from another manufacturer, stop and think Televue. Their prices are exactly the same and I guarantee you the performance is far superior. Now… There’s only one eyepiece left to try, and that test belongs to my much beloved Meade 12.5″ study grade reflector.

Let’s dance.

The 2″ Televue 55mm Plossl is a serious chunk of glass. But when you look through this one, you’ll be blown away. The eye relief is simply outstanding! Can you imagine seeing entire vistas like the Lagoon and Trifid Nebulae together? Can you picture the Sagittarius Star Cloud spraying out across the night? Holy cow… Have you ever seen all the stuff that’s really around the Ring Nebula? Have you spotted the little galaxy that’s near the M13 at the same time? You can’t image what the Dumbbell really looks like until you’ve captured it with the whole field around it…

Is it the same spacewalk effect produced by Nagler’s other famous eyepieces? Yes. But to a lesser degree. I have seen through even wider field Televue eyepieces and I can tell you that my eye can never take it all in. To me, the plossl is perfect. Here I see such a large, true field that I wish I had this around when it was galaxy season! Yes, I’m babbling. Every one that has a light bucket telescope should own one of these! What all this distills down to is this particular eyepiece is just slightly over $200 (US), ships anywhere in the world and comes with a 5-year Televue warranty and it’s not going back.

It’s a keeper.

The Televue Plossl Eyepieces for this product review were provided by Oceanside Photo and Telescope. We thank them for their generous loan and the check for the 55mm is in the mail. If Universe Today readers should choose to order from OPT, please type in “Universe Today Astronomers” into the Club Affiliation section of your order to receive your rewards discount!

The Iranian Satellite Rocket Saga

Iran has some big ambitions for space (Reuters)

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On August 16th, Iran triumphantly announced that they had sent a rocket into space, transporting a “dummy” satellite into orbit. According to Iranian state TV, the night-time launch of the two-stage Safir-e Omid (or Ambassador of Peace) rocket was a resounding success, transmitting video of the launch amid cheers of delight. The nation has never hidden its space ambitions, and in 2005 Iran launched its first commercial satellite on board a Russian rocket. This confirmed concerns of Russia’s co-operation with the Iranian government to bolster the country’s space-faring ability. However, US officials have spoken out against Iranian claims that Saturday’s launch went as planned; according to one official, Iran’s launch was a “dramatic failure.” Regardless, Iran appears to be upbeat about it’s future in space, and today the Iranian Space Organization Chief has announced that Iran will launch a man into space within a decade

Tensions between Iran and the West are edgy to say the least. For one, Iran’s nuclear program is causing obvious upset in the region; neighbouring countries concerned the balance of power is shifting toward Iranian President Mahmoud Ahmadinejad’s regime. Israel, in particular, has traded threats with Iran, and its close proximity to Tehran (only 600 miles) only helps to intensify the distrust in the region. Now, if the Iranian claims are to be believed, Ahmadinejad is able to order the launch of domestically built satellites, but more worryingly, this sabre rattling shows to the world they are able to launch long-range ballistic missiles to wherever they like. Combine this missile capability with the pressing nuclear threat (although Iran maintains that the Uranium enrichment is for peaceful purposes only), and we have a huge politically unstable situation. The bad blood between the US and Iran is all too obvious, this will only help to increase tensions.

However, the Iranian celebrations may be short lived. It is notoriously difficult to gain any verification that Iran did launch a two-stage rocket into space, let alone carry a “dummy” satellite into orbit. Yesterday, US officials made an announcement claiming that Iran was falsifying the launch and that the rocket failed soon after launch. Looking at the Iranian news footage, we only see the first few seconds of launch, so these doubts are justified.

The vehicle failed shortly after liftoff and in no way reached its intended position. It could be characterized as a dramatic failure […] The failed launch shows that the purported Iranian space program is in its nascent stages at best — they have a long way to go.” – Unnamed US official.


See the Iranian state TV footage of the Safir-e Omid launch (AP) »

Although a failed launch seems highly probable (as we all know, rocket science isn’t easy!), prompting the Iranian government to distribute false information about the “successful” launch to save face, but the US official gives no indication about how the US authorities know the launch was a failure. I think it’s going to be some time before these questions can be answered as neither side will want to reveal too much.

Regardless of the “did it launch or didn’t it” debate, Iran has today announced some pretty lofty plans for their future in space. Iran wants to send a man into space. Within ten years.

According to the Chinese news agency Xinhua, the Iranian Space Organization chief Reza Taghipour will set the exact date for a future manned mission within the year. Apparently, “Iran must win the first place in space technology in the region by the Iranian year of 1400 (the equivalent Christian year of 2021),” according to Xinhua (although it is unclear whether the Chinese source is quoting Taghipour or they are stating a fact). Iran also wants to launch a series of ten domestically-built satellites by 2010 to aid disaster relief operations.

Often it is hard to separate the facts from the fiction in the Middle East, but I can’t help but think these invigorated Iranian space ambitions are a ploy to wield their exaggerated military might in the region. Whether the dummy satellite was put into orbit or not seems to be rather academic, the fallout from the Iranian claim and US counter-claim will have severe consequences for US-Iran relations…

Sources: Space, Reuters, Xinhua

NASA Releases Images and Video of Orion Failed Parachute Test

The Orion parachute test drop didn't go so well... (NASA)

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As previously reported on the Universe Today, recent parachute test-drops for the Constellation Project have brought mixed results. The Ares I drogue parachute test appeared to perform flawlessly on July 24th, but the July 31st Orion test drop was a different story. Very early on in the parachute test, the “programmer parachute” (the first small parachute to be deployed, righting the descending crew module, setting Orion up for drogue deployment) failed after not inflating in the turbulent wake of the vehicle. This event set in motion complete parachute failure, ultimately forcing a hard-landing (crash) into the Arizona desert. Now NASA has released a video and pictures of the test…

The Parachute Test Vehicle is slid out of the aircraft. So far, so good (NASA)
The Parachute Test Vehicle is slid out of the aircraft. So far, so good (NASA)

On July 31st, hopes were high for a successful parachute test drop above the U.S. Army’s Yuma Proving Ground in Arizona. The week before, the Ares I re-usable booster rocket drogue parachutes had proven themselves, so pressure was on for the Orion analogue – the Parachute Test Vehicle (PTV) – to perform as it should.

A re-entering crew module has a complicated series of parachute deployments before it can land safely (a.k.a. a “soft” landing). Unfortunately, the July 31st test drop was anything but soft. Although the parachute deployment system performed as it should (i.e. the 18 parachutes opened at the correct time and in the correct manner), but the problem came right at the start of the chain: when the very first “programmer parachute” was deployed. As with any descending space vehicle, a programmer parachute needs to be deployed to ensure the crew module is a) the correct way up and b) set up for the critical “drogue parachute” deployment. The drogue reduces the vehicle’s velocity very quickly, moments before the main parachutes are deployed.

Flapping in the turbulent wake; the programmer parachute fails to open (NASA)
Flapping in the turbulent wake; the programmer parachute fails to open (NASA)

Alas, the programmer parachute never opened fully in the turbulent air behind the PTV, forcing the vehicle to swing wildly out of control. The drogue parachute had little chance to slow the descent as the spinning vehicle cased the inflating drogues to be ripped away. So the PTV went into freefall…

After falling for several seconds, the main parachutes made an appearance. Looking more like a party popper than a crew module, two of the main parachutes were ripped away like streamers, only one of the three parachutes remained connected. So its fate was sealed, the PTV was going to make a bone crushing hard-landing.

See the NASA video of the whole test, from drop to crash »

Only one main parachute remained as the PTV tumbled through the sky (NASA)
Only one main parachute remained as the PTV tumbled through the sky (NASA)

Oh well. I hope NASA has better luck next time. According to officials, this does not indicate an Orion technology failure, it was a “test technique failure” that was bound to frustrate the engineers on the ground. After all, the parachutes did deploy, they just didn’t open…

Suddenly the April hard-landing of the Russian Soyuz vehicle doesn’t seem so bad…

Source: NASA

Is This Black Hole Available in Size Medium?

Can Medium Sized Black Holes be Found in Globular Clusters? Credit: NASA/JPL-Caltech/ NOAO/AURA/NSF

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Black holes are sometimes huge – supermassive as they are called, billions of times the mass of our sun. Other times they are petite with just a few times the sun’s mass. But do black holes also come in size medium? A new study suggests that, most likely, the answer is no. Astronomers have long suspected that the best place to find a medium-mass black hole would be at the core of a miniature galaxy-like object called a globular cluster. Yet nobody has been able to find one conclusively. And now, a team of astronomers has thoroughly examined a globular cluster called RZ2109 and determined that it cannot possess a medium black hole, leading researchers to believe that black holes don’t come in medium, or at most are very rare.

“Some theories say that small black holes in globular clusters should sink down to the center and form a medium-sized one, but our discovery suggests this isn’t true,” said Daniel Stern of NASA’s Jet Propulsion Laboratory. Stern is second author of a study detailing the findings in the Aug. 20 issue of Astrophysical Journal. The lead author is Stephen Zepf of Michigan State University, East Lansing.

Black holes are incredibly dense points of matter, whose gravity prevents even light from escaping. The least massive black holes known are about 10 times the mass of the sun and form when massive stars blow up in supernova explosions. The heftiest black holes are up to billions of times the mass of the sun and lie deep in the bellies of almost all galaxies.

That leaves black holes of intermediate mass, which were thought to be buried at the cores of globular clusters. Globular clusters are dense collections of millions of stars, which reside within galaxies containing hundreds of billions of stars. Theorists argue that a globular cluster should have a scaled down version of a galactic black hole. Such objects would be about 1,000 to 10,000 times the mass of the sun, or medium in size on the universal scale of black holes.

The research team used the Keck Observatory on Mauna Kea in Hawaii to look at the spectrum of the cluster, which revealed that the black hole is petite, with roughly 10 times the mass of our sun.
According to theory, a cluster with a small black hole cannot have a medium one, too. Medium black holes would be quite hefty with a lot of gravity, so if one did exist in a globular cluster, scientists argue that it would quickly drag any small black holes into its grasp.

“If a medium black hole existed in a cluster, it would either swallow little black holes or kick them out of the cluster,” said Stern. In other words, the small black hole in RZ2109 rules out the possibility of a medium one.

The researchers believe other globular clusters would have a similar makeup and the likelihood for finding a medium black hole is not good. Zepf said it is possible such objects are hiding in the outskirts and of galaxies like our Milky Way, either in surrounding so-called dwarf galaxies or in the remnants of dwarf galaxies being swallowed by a bigger galaxy. If so, the black holes would be faint and difficult to find.

News Source: JPL

The Sun and the Moon

Solar Eclipse. Image credit: NASA

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The Sun and the Moon are the two objects in the Solar System that influence Earth the most. Let’s take a look at all the different was we experience these two objects, how they’re similar, and how they’re mostly different.

The Size of the Sun and the Moon

In absolute terms, the Sun and the Moon couldn’t be more different in size. The Sun measures 1.4 million km across, while the Moon is a mere 3,474 km across. In other words, the Sun is roughly 400 times larger than the Moon. But the Sun also happens to be 400 times further away than the Moon, and this has created an amazing coincidence.

From our perspective, the Sun and the Moon look almost exactly the same size. This is why we can have solar eclipses, where the Moon passes in front of the Sun, just barely obscuring it from our view.

And this is just a coincidence. The gravitational interaction between the Moon and the Earth (the tides) are causing the Moon to slowly drift away from the Earth at a rate of 3.8 centimeters per year. In the ancient past, the Moon would have looked much larger than the Sun. And in the far future, the Moon will look much smaller. It’s just a happy coincidence that they look the same size from our perspective.

Gravity from the Sun and the Moon

Once again, the Sun is much larger and has a tremendous amount of mass. The mass of the Sun is about 27 million times more than the mass of the Moon. It’s this gravitational interaction that gives the Earth its orbit around the Sun, and the tiny pull of the Moon just causes the Earth to wobble a bit in its movements.

When the Sun and the Moon are pulling on the Earth from the same direction, their gravity adds up, and we get the largest spring tides. And then, when they’re on opposite sides of the Earth, their forces cancel out somewhat, and we get neap tides.

Light from the Sun and the Moon

This is a bit of a trick, since the Sun is the only object in the Solar System actually giving out light. With its enormous mass, the Sun is able to fuse hydrogen into helium at its core, generating heat and light. This light shines in the Solar System, and bounces off the Moon so we can see it in the sky.

Astronomers measure brightness using a measurement called magnitude. The star Vega was considered 0 magnitude, and the faintest star you can see with the unaided eye is about 6.5 magnitude. Venus can get as bright as -3.7, the full Moon is -12.6, and the Sun is -26.73. These numbers sound similar, but it’s a logarithmic scale, where each value is twice the amount of the previous one. 1 is twice as bright as 2, etc.

So the Sun is actually 450,000 times brighter than the Moon. From our perspective.

Composition of the Sun and the Moon

Now here’s where the Sun and the Moon differ. The Sun is almost entirely composed of hydrogen and helium. The Moon, on the other hand, was formed when a Mars-sized object crashed into the Earth billions of years ago. Lighter material from the collision collected into an object in orbit – the Moon. The Moon’s crust is primarily oxygen, silicon, magnesium, iron, calcium, and aluminium. Astronomers think the core is metallic iron with small amounts of sulfur and nickel. And it’s at least partly molten.

Here’s an article about the distance from the Earth to the Sun, and here’s a view of the Earth and the Moon, seen from Mars.

Have you ever seen that picture of the Moon and the Sun “from the North Pole”, where the Moon looks huge? It’s actually a hoax, here’s more information from Astronomy Picture of the Day.

References:
NASA SOHO
NASA Starchild: Earth’s Natural Satellites
NASA Eclipse: Measuring the Moon’s Distance
NASA: Stellar Magnitude Scale

Hubble Spies Beautiful, Beastly Monster Galaxy

Complete with tentacles, a supermassive black hole and x-ray emitting gas, a monster of a galaxy has been found by NASA’s Hubble Space Telescope, and is helping astronomers answer a long-standing puzzle. The very active galaxy NGC 1275 has giant but beautiful and delicate filaments influenced and shaped by a beastly-strong extragalactic magnetic field. But how the delicate structures such as those found in this galaxy can withstand the hostile, high-energy environment has been a mystery. But researchers say the beauty and the beast co-exist and are dependent on each other for survival.

One of the closest giant elliptical galaxies, NGC 1275 hosts a supermassive black hole. Energetic activity of gas swirling near the black hole blows bubbles of material into the surrounding galaxy cluster. Long gaseous filaments stretch out beyond the galaxy, into the multimillion-degree, X-ray–emitting gas that fills the cluster. Astronomers thought these delicate filaments should have heated up, dispersed, and evaporated by now, or collapsed under their own gravity to form stars.

These filaments are the only visible-light manifestation of the intricate relationship between the central black hole and the surrounding cluster gas. They provide important clues about how giant black holes affect their surrounding environment.

Using Hubble’s view, a team of astronomers led by Andy Fabian from the University of Cambridge, UK, have for the first time resolved individual threads of gas that make up the filaments. The amount of gas contained in a typical thread is around one million times the mass of our own Sun. They are only 200 light-years wide, are often very straight, and extend for up to 20,000 light-years. The filaments are formed when cold gas from the core of the galaxy is dragged out in the wake of the rising bubbles blown by the black hole.

A new study published in the August 21 Nature magazine proposes that magnetic fields hold the charged gas in place and resist the forces that would distort the filaments. This skeletal structure is strong enough to resist gravitational collapse.

“We can see that the magnetic fields are crucial for these complex filaments – both for their survival and for their integrity,” said Fabian.

Similar networks of filaments are found around other more remote central cluster galaxies. However, they cannot be observed with comparable resolution to the view of NGC 1275. In future observations, the team will apply the understanding of NGC 1275 to interpret what they see in other, more distant galaxies.

News Source: Hubble Site