Posted on by Fraser Cain

Smallest Galactic Black Hole Found

Image credit: Hubble
A group led by astronomers from Ohio State University and the Technion-Israel Institute of Technology have measured the mass of a unique black hole, and determined that it is the smallest found so far.

Early results indicate that the black hole weighs in at less than a million times the mass of our sun -? which would make it as much as 100 times smaller than others of its type.

To get their measurement, astronomers used NASA?s Hubble Space Telescope and a technique similar to Doppler radar — the method that meteorologists use to track weather systems.

The black hole lies 14 million light-years away, in the center of the galaxy NGC 4395. One light-year is the distance light travels in one year — approximately six trillion miles.

Astronomers consider NGC 4395 to be an ?active galaxy,? one with a very bright center, or nucleus. Current theory holds that black holes may literally be consuming active galactic nuclei (AGNs). Black holes in AGNs are supposed to be very massive.

NGC 4395 appears to be special, because the black hole in the center of the galaxy is much smaller than those found in other active galaxies, explained Ari Laor, professor of astronomy at the Technion, in Haifa, Israel, and Brad Peterson, professor of astronomy at Ohio State.

While astronomers have found much evidence of black holes that are larger than a million solar masses or smaller than a few tens of solar masses, they haven?t found as many midsize black holes — ones on the scale of hundreds or thousands of solar masses.

Black holes such as the one in NGC 4395 provide a step in closing that gap.

Laor and Peterson and their colleagues used the Doppler radar-like technique to track the movement of gas around the center of NGC 4395. Whereas radar bounces a radio frequency signal off of an object, the astronomers observed light signals that naturally emanated from the center of the galaxy, and timed how long those signals took to reach the orbiting gas.

The method is called reverberation mapping, and Peterson?s team is among a small number of groups who are developing it as a reliable means of measuring black hole masses. The method works because gas orbits faster around massive black holes than it does around smaller ones.

Peterson reported the early results Saturday at the meeting of the American Association for the Advancement of Science in Washington, DC.

Two of the team members — Luis Ho of the Observatories of the Carnegie Institution of Washington, and Alex Fillippenko of the University of California, Berkeley — were the first to suspect that the black hole mass was very small. Filippenko and Wallace L.W. Sargent of the California Institute of Technology first discovered the black hole in 1989.

This is the first time astronomers have been able to measure the mass of the black hole in NGC 4395, and confirm that it is indeed smaller than others of its kind.

Peterson and Laor emphasized that the results are very preliminary, but the black hole seems to be at least a hundred times smaller than any other black hole ever detected inside an AGN.

The astronomers want to refine that estimate before they address the next most logical question: why is the black hole so small?

?Is it the runt of the litter, or did it just happen to form under special circumstances? We don?t know yet,? Peterson said.

NGC 4395 doesn?t appear to have a dense spherical nucleus, called a galactic bulge, at its center; it could be that the black hole ?ate? all the stars in the bulge, and doesn?t have any more food within reach. That would keep the black hole from growing.

Team members are most interested in what the black hole measurement can tell astronomers about AGNs in general. Any new information could help astronomers better understand the role that black holes play in making galaxies like our own form and evolve. To that end, the team is also studying related data from NASA?s Chandra X-ray Observatory and ground-based telescopes.

?It?s these extreme types of objects that really allow you to test your theories,? Peterson said.

Original Source: OSU News Release

Posted on by Mark Mortimer

Book Review: Deep Sky Observer’s Guide

Deep sky observing is the sport of picking out significant, night-time, light sources with the aid of an optical lens. More than just enlarging pinpricks, the lens or lenses evolve the light sources into patterns, shapes and even distinct colours. Of course, with people having stared up at the night sky for ages, with and without aids, some significant knowledge gets built up. There are the shapes that form the signs of the zodiac, precession that defines epochs and historians who record the rise and fall of stellar blazes. As a backdrop to all of these, there are literally billions of other lights sources. This is where the guide’s strength lies as it helps a viewer enter this realm via useful guideposts, notices and advertisements.

In particular, this guide details over 200 night time sparkles. Seven chapters divide these into well known stellar entities, such as galaxies and nebulae. Each individual description includes some basic information; the popular name, where its located (right ascension and declination) and its magnitude. Then, more useful for the amateur viewer, come tricks on seeing the correct sparkle through your binoculars or telescope; the best magnification, viewing style (direct or averted) and any locating stars. Often, bonus comments supply details on the history of its observations, perhaps a bit on the physics involved (e.g. the light is from emissions due to depleted oxygen atoms capturing an electron), and a bit on the stellar activity (e.g. part of a galaxy’s spiral arms ). Having over 400 years of observations to consider makes a guide book like this an extremely practical starting point before venturing into the night time skies.

To further help the amateur astronomer in their activities, Neil Bone fills out his guide with some useful background information. Each chapter begins with a snippet of information about the category. For instance, galaxies, we’re told, are collections that formed in the early stages of the universe and have a uniform field of motion. Where appropriate, morphological classifications further divide categories. Again for galaxies, Edwin Hubble’s “tuning fork” model sets the delineations. And in extending this background further, Bone provides a quick synopsis on the mechanics or evolutions of the subject and expectations for change. Planetary nebulae, for instance, result from a normal star aging into a red star, which subsequently swells further and expels vast amounts of itself in a very vivid explosion, the after effects being the observed nebula. With all this information, the night time sparkles do indeed look more and more take on the value of diamonds.

Aside from expanding on what’s viewed in the lens, Bone’s guide also provides some useful insight on periphery issues. The equipment; binoculars, refractors, mounts and eyepieces get their due. Hints abound throughout, such as the benefits of portable equipment to allow for the necessary commute away from obscuring city lights. The history of viewing identifies some of the important individuals as well as some of their unique instruments. For example, most subjects come with their Messier’s identification. We also learn about de Chesaux’s catalogue of 9776 objects. Bode identified 77 nebulous groups while Hershel had his own list of 400. Reworking through any of these lists could be a lifetime challenge but then there’s the Messier Marathon. Here, a person tries to observe each of the 110 Messier objects in one night. To aid in this or more leisurely pursuits, the guide comes well abridged with field sketches, pictures and diagrams. Wide-field star charts and deep sky listings by constellation, season and magnitude complete the tidbits of information.

Listing stellar objects vitals could very easily have resulted in an extremely dry text. Luckily Bone doesn’t fall completely into this trap. There are many charts and tables, and though each description reads like a recipe, there are also many personal anecdotes and opinions to remind the reader that this book is for the hobbyist who wants to enjoy their pastime. This, together with the provision of club names as well as national and international organizations, give great ideas on how to inflame an amateur viewer’s passion.

Having a handy back pocket reference is essential for star-parties or any late night venues where the stars come into focus. Neil Bone, in his book Deep Sky Observer’s Guide gives this excellent reference for this activity. With descriptions aplenty and star charts spanning all the heavens, this book will enable you to leap to the rescue when someone wonders, “What’s that dot up there?”.

To get your own copy, visit Amazon.com.

Review by Mark Mortimer

Posted on by Fraser Cain

What’s Up This Week – Feb 21 – 27, 2005

M 41 credit: NOAO/AURA/NSF
Monday, February 21 – Tonight let’s head four degrees south of the incredible Sirius and locate an easy binocular or telescope object – M 41. Noted as early as 325 B.C. by Aristotle – and cataloged by Messier in 1765, the M 41 is a beautiful, loose, looping collection of around two dozen bright stars and many more faint members that range with aperture. At around 2,300 light years away, it’s remarkable we can see it at all! Spanning approximately 25 light years, it is estimated this cluster could be as much as 240 million years old. Although the presence of the Moon will harm some of its fainter members, the M 41 sports many red “giant” stars – especially the one in the center!

Now, let’s have a look at the Moon and identify a new crater. Near the terminator and south of Mare Humorum you will find a very notable walled plain known as Schickard. While it doesn’t appear to be much, Schickard is almost as large as the Netherlands! Notice its bright white wall underscored with shadow along the northeast inner wall. Schickard is an unusual crater because of its curvature – it’s convex! At its center, the walled plain is just a little bit more than 213 meters (700 feet) higher than the area at the edges. If you were standing in the middle of this crater and scanning the horizon, you could never see the walls!

Tuesday, February 22 – Since the Moon will dominate the evening sky, let’s start by observing and identifying an “on the edge” feature. Return to previous study area, Sinus Iridum and head north! Near the terminator you will see a slender, bright ellipse with a bright northwest wall and a dark southeast wall. This is the deep, walled plain of class one Pythagoras. Note the bright twin central peak that rises around 1829 meters (6000 feet) high. Considering the angle that we see this area from, that type of elevation is comparable to the height of El Cielo – Mexico’s “Cloud Forest”!

And while we have our head in the clouds, let’s have a look at the eighth brightest star in the sky – Procyon. At around 11.3 light years away from us, the “Little Dog Star” is the fifth nearest star to Earth. It is well known that Procyon is a double star – but that’s a challenge beyond the ordinary backyard scope. Very much like Sirius, the 13th magnitude companion is also a dwarf star – one that’s about twice the size of our Earth!

Wednesday, February 23 – Although the Moon appears full tonight, it’s just not official. According to folklore, this is known as both the “Snow Moon” and the “Storm Moon”… Let’s hope that doesn’t mean certain areas of the world are about to get buried again! Tonight let’s have a look at Selene with either binoculars or telescope. We are looking for the pale, shallow form of Langrenus on the eastern edge of Mare Fecunditatis. It won’t appear very impressive tonight, but let’s see how much it changes in 48 hours!

With incredibly bright skies tonight, let’s turn a little attention toward the dominant star in Auriga – Capella. As the sixth brightest star in the sky, lovely yellow Capella is around 45 light years away. As with most stars, the “Goat” is actually a multiple system! Although its members are too close to be split with average equipment, if skies are steady you might be able to glimpse 10th magnitude red dwarf – Capella H – toward the southeast!

Thursday, February 24 – It’s official… Full Moon at 4:54 UT! Tonight let’s scan the western limb of the Moon and look for the Cordillera Mountains south of Grimaldi. Although this will appear as nothing more than a rough edge, we do this so we may see the effects of lunar libration. Remember what you see… We’ll be back in two days.

And speaking of two, let’s try our hand at Rigel tonight . As you may have noticed for the most part – the brighter the stars are – the closer they are. Not so Rigel! As the seventh brightest star in the sky, it breaks all the “rules” by being an amazing 900 light years away! Can you imagine what an awesome supergiant this white hot star really is? Rigel is actually one of the most luminous stars in our galaxy and if it were as close as Sirius it would be 20% as bright as tonight’s Moon! As an added bonus, most average backyard telescopes can also reveal Rigel’s 6.7 magnitude blue companion star. And if these “two” aren’t enough – note the companion is also a spectroscopic double!

Friday, February 25 – Before the rising Moon interferes tonight, let’s have a go at C/2003 K4 LINEAR. At around magnitude 9, this small comet will be fairly easy to locate telescopically just west of Tau 3 Eridanus.

Let’s return to the Moon tonight to have another look at class 1 crater Langrenus. What a difference! Instead of the bright ring we saw two nights ago, Langrenus is now alive with detail. With the lunar terminator just to its east, we can now see its dual central mountain. Just outside of the crater rim to the northwest, a cluster of three tiny punctuations are revealed – Langrenus F (Bilharz), B (Naonobu) and K (Atwood). Look for tiny crater Acosta just to the north, and Lohse to the south!

Saturday, February 26 – For those living in time zones where 13:00 UT (5:00 a.m. PST) presents you with an opportunity to look at the moon, the libration will now be correct for Mare Oriental. Return to the Cordillera Mountains south of Grimaldi and see if the extra 5.7 degrees of shift reveals the dark edge of this seldom seen area!

Tonight Atlas and Hercules will steal the lunar show to the north, but let’s head to the south and identify class crater Rheita on the terminator. Although the crater itself is not terribly impressive, look closely at its west rim. You will pick up on a very noticeable black streak with a bright edge to the east. This is the Rheita Valley, and much older than the crater which bears its name! It curves slightly south-east towards the terminator and it is believed to be a chain of craters which have merged ending in larger crater Young.

Sunday, February 27 – Heads up for Southern Australia! The Moon will occult Jupiter for you on this universal date. Please check IOTA for the viewing area and universal timing. We wish all of you clear skies for this awesome event!!

If the Sun is shining today in the northern hemisphere, have a look at your “marker” that we picked at solstice. You’ll see its shadow is one-third shorter!

And for those in the north, Comet Machholz is still putting on a wonderful display as it has become a circumpolar object. Before “you know who” decides to light up the night sky, try looking east of Gamma Cepheus. By this time, the “Magnificent Machholz” with be approaching magnitude 6, but it will still be a great object even for small binoculars!

As we visit the Moon again tonight, we will be looking a rather prominent feature south of Mare Nectaris – Piccolomini. In bold black and white relief, you can’t miss this small crater’s striking central peak!

Until next week, remember Saturn and Jupiter also are wonderful things to look at during “moonshine”, and don’t forget double stars! Me? I’m looking forward to dark skies again! Light speed… ~Tammy Plotner

Posted on by Fraser Cain

Your First Scope! What’s Next?

Image credit: Astro.Geekjoy
Like many hobbies, an interest in amateur astronomy can suddenly flare up or be the natural out-working of many years of quiet contemplation. Developing that interest further can occur through sheer whim and fancy – or follow a carefully thought-through process of selective reasoning. Like the proverbial race between the hare (“Lepus”) and the tortoise (“Al Shilyak”), the hobby of amateur astronomy can move in fits and starts – or maintain a constant momentum. Following either approach can lead to the finish line. But in amateur astronomy the “finish line” is but the beginning of a longer journey – one that starts with the acquisition of that very first astronomical instrument of long-seeing (the telescope).

Are you the kind of person who plots and plans? Or the kind that pots and pans? Most of us lie somewhere between. We peek and poke around a thing until critical mass is achieved. Then we overcome rolling resistence, toss down some hard-earned cash, and walk away with our shiny new scope in excited anticipation of that first night out amongst the stars. But before first light comes the first rite.

Will the ritual of putting that scope together lead to “buyer’s remorse” or “great of course!”? Somehow we must successfully assemble that new scope, align it for practical use, and overcome the initial bump in the learning curve that could block us from achieving our astronomical potential and fulfilling our aspirations.

A telescope typically starts out in a variety of pieces. These pieces come in boxes. The first order of the day – not the night – is to pull all these parts together to make a working scope. To help in this an instruction manual should have arrived with your scope. Ideally that manual should provide all the clues needed – in word and picture – to make scope assembly possible.

Before you start make sure that all the parts needed came in those boxes and that each part appears to be in good working order. Anything missing? Contact the vendor. Anything damaged? Contact the vendor. Anything you don’t understand? Contact…

“And thus great things have smaller things, smaller things that bind them, and these small things have smaller things, hopefully not ad infintem.”

But right here is your first “gotcha” – you need to have a basic understanding of how that telescope works – along with a practical grasp of the purpose of each conmponent and the practical relationships between them.

Thankfully – compared to particle accelerators for instance – telescopes are relatively simple devices. One part of the telescope gathers the light to form an image, another reveals that image to the eye. A third helps you find what you’re looking for, and a forth holds things together enough so you can enjoy looking at it. If you already know the names for these four basic assemblies you are already on your way to making sense out of the instructions coming with your new scope. If not, you may want to spend some quality-time with the person who sold it to you…

So now we assume you’ve installed the finder on the optical tube assembly, placed an eyepiece in the focuser, and mated the telescope to its fully assembled mount. The next step is to get all these parts working together as a team.

Presumably your first scope is small enough that mount and scope, finder and eyepiece can all be hand carried out onto the front drive where you can point it at a distant tower or building. If the scope uses a non-tracking altazimuth or dobsonian mount you should have no trouble figuring out how to get the telescope tube to swing toward any chosen target. If you are one of the brave souls who chooses to master the complexities of the equatorial mount, you may be in for a shock – the thing just doesn’t make sense!

Equatorial mounts are enigmatic for one very good reason: they are meant for astronomical – not terrestrial use. The key to the equatorial mount is to think astronomically! And to think astronomically you need but ask one simple question: “What part of the sky does not move as the Earth turns?”

If you came up with “the north or south pole” you have the IQ for the EQ. That “T”-shaped part of your german equatorial mount must be aimed precisely as possible at a celestial pole (depending on your earthly latitude). So look at it this way, if you live among walruses and polar bears you would simply adjust that “T” as though it were a “T”. Everything celestial would appear to move in a great circle and your scope would follow that apparent motion in the sky. (Did you say: “I get it just like a dobsonian or altazimuth mount!”?) But if you live on the equator that T would be a “lazy-T” (-|) pointing off toward some distant point on the horizon. Those great arcs would sweep up, over, and down.

But where on the horizon precisely? Toward the same pole where the T pointed earlier – only now its harder to find. Since most folks don’t live on the equator, and none live at the poles, you simply adjust the angle of the “T” to the same angle as your geographic latitude and point it due north or south (not magnetic north – but physical). In fact many equatorial mounts include an angular scale to assist in this. Do you live at 42 degrees north latitude? Well then, swing that declination axis upward until the little arrow on the side of the mount settles on 42 degrees. Follow this by leveling the mount (using the leg extensions) whenever you set up outside for a night of astro-navigation. Don’t know where due north is? Point that same axis in the direction of Polaris! Live south of the equator? Things get more complicated (since there is no Polaris-star-south to guide her by) – but the equatorial can still be used – polar alignment just gets a bit more complicated.1.

But right now you have everything setup outside. If the optical tube is on an equatorial mount, the base of the “T” points toward the pole. (If an altazimuth, the single pivoting shaft points straight up. If a dobsonian, the “rocker box” holding the newtonian telescope is level.) Your next challenge is to align the finderscope with the main tube using the most distant target possible. (This overcomes parallaxial shift between the two instruments).

Amateur astronomers vary in type finderscope favored. The traditional finder takes the form of a small refractor telescope of 2 (or fewer) inches in aperture and less than 10 power magnification. It typically includes crosshairs to simplify precise sighting. Such a finder shows less than 10 degrees of the sky in a single view. (10 degrees is roughly the apparent width of your fist arm extended.) Other amateurs favor “unit finders” of one type or another. Unit finders are simple sighting devices. More sophisticated models include an illuminated reticle to center specific stars or regions of the sky while less sophisticated ones simply display a red dot to “hide” the star intended. Irrespective of finder type, the task at hand is to align it to center on whatever is seen in the main telescope.

Most telescopes come with at least two eyepieces. Of the two, the physically larger one is likely to give the lowest power (and largest field of view). You can confirm this by inspecting each eyepiece for a stamped or silk-screened number (typically designated in mm’s refering to the eyepiece’s focal length). Contrary to what you might expect, the larger the focal length the lower the power of that particular eyepiece. (To actually determine the power selected, you must also know the focal length of the telescope itself – something that will matter more once you have more experience.)

After installing the low power eyepiece, sight along the tube at the most distant target possible. Now for the moment of clarity: Place your observing eye about one inch above the eyepiece. Shift your head slightly until you see a bright region right in its midst. Slowly lower your head allowing this region (the exit pupil) to expand until you can look inside the eyepiece and take in the entire dark perimeter of the field stop in one glance. Holding still, carefully reach for the focusing knob and turn it first one way then the other to get a sense of what direction the focuser needs to move in order to sharpen the image. Then go for it! Sharpen that image as much as possible – overshoot, undershoot, and settle in on the very best position of the eyepiece – relative to the objective lens or mirror – that gives the very best view2.

Make a mental note of whatever it is that you are looking at then shift over to the finder. Make the mechanical adjustments needed to center the very same target in the finder without moving the main tube. (It doesn’t matter at this point if the target you originally selected is the one you end up with in this first rough pass at finderscope alignment.) Once the same target is centered in both the finder and the main scope then drop in the higher power eyepiece and attempt to lock on the original (most distant) target and repeat the alignment procedure.

With the finder scope aligned you can now begin practicing with your scope. Pick out distant targets from all around you. Make sure that each target is at least several hundred meters away. Get accustomed to shifting the scope to all angles – but DON’T turn your scope anywhere near the sun!!! (Danger Will Robinson, Danger!) Practice centering your eye over the eyepiece alot. (It’ll be tougher in the dark and you won’t have a bright circle to guide your eye position.)

Now you’re ready for first (astronomical) light. Right after sunset, set up your telescope outside in an open area. (The best spot will have a north-south view.) Give it a chance to cool down to air temperature. It’s best to leave dust caps on the scope but if temperatures are dropping quickly remove the one on the main tube to speed up cool down – but there’s no reason to expose the eyepieces or finder to dust. If the Moon isn’t up, grab yourself a cup of tea while you do some homework on the web or in books to see “What’s up” in the early evening sky. Some forty-five minutes after sunset the very first bright stars (Vega, Deneb, Fomalhaut, Rigil, Capella, Sirius, Procylon, Rigil Kentaurus, Canopus etc.) or planets (Venus, Mars, Jupiter, and Saturn) will peek out. Start practicing with your telescope at low power. Get used to slewing your scope around and finding things. Work on your focusing and eye centering technique. Try different eyepieces – but always come back to the lowest power before searching for the next celestial study. Don’t be surprised at how fast things move across the field of view – especially at higher powers! Get “the drift” of this and learn how to anticipate the motion by slewing your mount slowly. Don’t use any tracking drive until after you’ve mastered manual slewing. And yes, take some time to really appreciate what you are looking at! This is the time to develop some positive observing habits.

Within an hour and a half of sunset skydark will arrive. Conditions should be ripe for your first deepsky study. What’s going to be first? How about that Whirlpool Galaxy – ain’t she a beaut?

Like “Dirty Harry” said: “Know your limitations.” First you’ll need to find your way around the night sky. Start with the circumpolar constellations. Think of them as “jumping off points” – based on the time of night and the seasons of the sky. If the Big Dipper (Ursa Major) is high overhead – look further south and you’ll see bright Regulus and well-formed Leo the Lion. Want more of a challenge? Find Leo Minor between them. If the circumpolar constellations are not visible to you, start with the zodiac. Some – Taurus, Gemini, Leo, Scorpio, and Sagittarius – include bright stars or are easily grasped by the imagination. Others (Aries, Virgo, and Libra) are bright enough but less easily traced out against the sky. Capricorn, Aquarius, Pisces, and Cancer are relatively obscure and take some real concentration. Once you know your way around the circumpolars and zodiacals try your eye on those constellations bathed in the light of the Milky Way. From then on out just let whim or necessity drive your wanderings – they’ll always be plenty of opportunity to go a wandering and a wondering!

Be sure to get a good set of star charts – nothing too sophisticated at first. You won’t be tracking down IC (Index Catalog) galaxies right away. Practical charts include stars visible to magnitude 5.5 at least. It should also include all 109 Messier deep sky studies plus a half-dozen or so findable double stars in each of the major constellations. Software programs are also available on the open market or can be downloaded off the web. You may even have received a free software CD with your telescope. Such programs are very useful in determining the location of the Moon, planets, and certain periodic comets. They also include logs for archiving your observing notes. (These are often transcribed from a tape recorder or brief notes taken during observing sessions. Your observing notes are your future gift to self – and possibly others. They are the legacy of your love for the Night Sky.)

Your immediate goal is to learn how to use your scope and really enjoy whatever you see. As you learn the constellations set goals like finding anything in the night sky brighter than the 6th magnitude – including studies like magnitude 5.9 M13, the Great Cluster in Hercules; magnitude 3.5, the Great Galaxy in Andromeda and magnitude 4.0, the Great Nebula in Orion. Keep in mind that just because a study doesn’t include the appellation “Great” doesn’t mean that it won’t be “great” to find and observe. Also keep in mind that you will not get views like those seen through the telescopes in the “Great” Observatories either. But you will get views that are very unique and personal to you, your scope, and the sky through which you observe.

Ultimately you may discover that amateur astronomy is one of the “greatest” of all hobbies – one that knows no limits in terms of experience – personal and social. There is also no limit to what can be learned. After all, astronomy covers the whole universe – and there’s no reason to think the it only comes out at night or ends with the horizon…

1Once your equatorial mount is set up for your latitude (using the vertical compass and index mark), the first step in locating the south celestial pole is to find the southern cross (Crux). Once this bright tight constellation is found, extend your fist an arms length away from you and follow the cross south three fists (or five cross) lengths. Orient your declination axis toward that point. Then sight the scope itself on any bright star well away from the pole (most are!) Install your highest power eyepiece. Center the star in your eyepiece field and allow it to drift across the field. Bring the star back to its original position by adjusting only the azimuth position of the mount until the star always returns to the center of the field. To simplfy future polar alignment, rotate the finderscope crosshairs until that same star skims across one of them perfectly. Then during future setup simply reposition the tripod legs until you can reproduce the skimming effect by moving the telescope slow motion along that same axis. (This last works fine north of the equator too.)

2Telescopes can only focus on studies at a limited range of distances. If you select an target too nearby, the focuser will fully extend away from the light-gathering objective lens or mirror without achieving focus. If however the focuser travels all the way in without focus, contact your vendor. Also note, some telescopes (SCT’s & MCTs) use primary mirror shift rather than eyepiece travel to set focus. If for some reason the mirror-shift mechanism is loose you will have trouble settling in at precise focus due to “image hop” as you turn the knob.

Acknowledgement: My Thanks to Anthony Jifkins of Melbourne, Australia who suggested that I write this article for publication at Universe Today.

About The Author:
Inspired by the early 1900’s masterpiece: “The Sky Through Three, Four, and Five Inch Telescopes”, Jeff Barbour got a start in astronomy and space science at the age of seven. Currently Jeff devotes much of his time observing the heavens and maintaining the website
Astro.Geekjoy.

Posted on by Fraser Cain

Ammonia Key to Titan’s Atmosphere

Cassini-Huygens supplied new evidence about why Titan has an atmosphere, making it unique among all solar system moons, a University of Arizona planetary scientist says.

Scientists can infer from Cassini-Huygens results that Titan has ammonia, said Jonathan I. Lunine, an interdisciplinary scientist for the European Space Agency’s Huygens probe that landed on Titan last month.

“I think what’s clear from the data is that Titan has accreted or acquired significant amounts of ammonia, as well as water,” Lunine said. “If ammonia is present, it may be responsible for resurfacing significant parts of Titan.”

He predicts that Cassini instruments will find that Titan has a liquid ammonia-and-water layer beneath its hard, water-ice surface. Cassini will see — Cassini radar has likely already seen — places where liquid ammonia-and-water slurry erupted from extremely cold volcanoes and flowed across Titan’s landscape. Ammonia in the thick mixture released in this way, called “cryovolcanism,” could be the source of molecular nitrogen, the major gas in Titan’s atmosphere.

Lunine and five other Cassini scientists reported on the latest results from the Cassini-Huygens mission at the American Association for the Advancement of Science meeting in Washington, D.C. today (Feb. 19).

Cassini radar imaged a feature that resembles a basaltic flow on Earth when it made its first close pass by Titan in October 2004. Scientists believe that Titan has a rock core, surrounded by an overlying layer of rock-hard water ice. Ammonia in Titan’s volcanic fluid would lower the freezing point of water, lower the fluid’s density so it would be about as buoyant as water ice, and increase viscosity to about that of basalt, Lunine said. “The feature seen in the radar data suggests ammonia is at work on Titan in cryovolcanism.”

Both Cassini’s Ion Neutral Mass Spectrometer and Huygen’s Gas Chromatograph Mass Spectrometer (GCMS) sampled Titan’s atmosphere, covering the uppermost atmosphere down to the surface.

But neither detected the non-radiogenic form of argon, said Tobias Owen of the University of Hawaii, a Cassini interdisciplinary scientist and member of the GCMS science team. That suggests that the building blocks, or “planetesimals,” that formed Titan contained nitrogen mostly in the form of ammonia.

Titan’s eccentric, rather than circular, orbit can be explained by the moon’s subsurface liquid layer, Lunine said. Gabriel Tobie of the University of Nantes (France), Lunine and others will publish an article about it in a forthcoming issue of Icarus.

“One thing that Titan could not have done during its history is to have a liquid layer that then froze over, because during the freezing process, Titan’s rotation rate would have gone way, way up,” Lunine said. “So either Titan has never had a liquid layer in its interior — which is very hard to countenance, even for a pure water-ice object, because the energy of accretion would have melted water — or that liquid layer has been maintained up until today. And the only way you maintain that liquid layer to the present is have ammonia in the mixture.”

Cassini radar spotted a crater the size of Iowa when it flew within 1,577 kilometers (980 miles) of Titan on Tuesday, Feb. 15. “It’s exciting to see a remnant of an impact basin,” said Lunine, who discussed more new radar results that NASA released at an AAAS news briefing today. “Big impact craters on Earth are nice places for getting hydrothermal systems. Maybe Titan has a kind of analogous ‘methanothermal’ system,” he said.

Radar results that show few impact craters is consistent with very young surfaces. “That means Titan’s craters are either being obliterated by resurfacing, or they are being buried by organics,” Lunine said. “We don’t know which case it is.” Researchers believe that hydrocarbon particles that fill Titan’s hazy atmosphere fall from the sky and blanket the ground below. If this has occurred throughout Titan’s history, Titan would have “the biggest hydrocarbon reservoir of any of the solid bodies in the solar system,” Lunine noted.

In addition to the question about why Titan has an atmosphere, there are two other great questions about Saturn’s giant moon, Lunine added.

A second question is how much methane has been destroyed throughout Titan’s history, and where all that methane comes from. Earth-based and space-based observers have long known that Titan’s atmosphere contains methane, ethane, acetylene and many other hydrocarbon compounds. Sunlight irreversibly destroys methane in Titan’s upper atmosphere because the released hydrogen escapes Titan’s weak gravity, leaving ethane and other hydrocarbons behind.

When the Huygens probe warmed Titan’s damp surface where it landed, its instruments inhaled whiffs of methane. That is solid evidence that methane rain forms the complex network of narrow drainage channels running from brighter highlands to lower, flatter dark areas. Pictures from the UA-led Descent Imager-Spectral Radiometer experiment document Titan’s fluvial features.

The third question — one that Cassini was not really instrumented to answer — Lunine calls the “astrobiological” question. It is, given that liquid methane and its organic products rain down from Titan’s stratosphere, how far has organic chemistry progressed on Titan’s surface? The question is, Lunine said, “To what extent is any possible advanced chemistry at Titan’s surface at all relevant to prebiotic chemistry that presumably occurred on Earth prior to the time life began?”

The Cassini-Huygens mission is a collaboration between NASA, ESA and ASI, the Italian Space Agency. The Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, is managing the mission for NASA’s Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini oribter while ESA operated the Huygens probe.

Original Source: University of Arizona News Release

Posted on by Fraser Cain

Gamma Ray Flare Reaches Across the Galaxy

Forget “Independence Day” or “War of the Worlds.” A monstrous cosmic explosion last December showed that the earth is in more danger from real-life space threats than from hypothetical alien invasions.

The gamma-ray flare, which briefly outshone the full moon, occurred within the Milky Way galaxy. Even at a distance of 50,000 light-years, the flare disrupted the earth’s ionosphere. If such a blast happened within 10 light-years of the earth, it would destroy the much of the ozone layer, causing extinctions due to increased radiation.

“Astronomically speaking, this explosion happened in our backyard. If it were in our living room, we’d be in big trouble!” said Bryan Gaensler (Harvard-Smithsonian Center for Astrophysics), lead author on a paper describing radio observations of the event.

Gaensler headed one of two teams reporting on this eruption at a special press event today at NASA headquarters. A multitude of papers are planned for publication.

The giant flare detected on December 27, 2004, came from an isolated, exotic neutron star within the Milky Way. The flare was more powerful than any blast previously seen in our galaxy.

“This might be a once-in-a-lifetime event for astronomers, as well as for a neutron star,” said David Palmer of Los Alamos National Laboratory, lead author on a paper describing space-based observations of the burst. “We know of only two other giant flares in the past 35 years, and this December event was one hundred times more powerful.”

NASA’s newly launched Swift satellite and the NSF-funded Very Large Array (VLA) were two of many observatories that observed the event, arising from neutron star SGR 1806-20, about 50,000 light years from Earth in the constellation Sagittarius.

Neutron stars form from collapsed stars. They are dense, fast-spinning, highly magnetic, and only about 15 miles in diameter. SGR 1806-20 is a unique neutron star called a magnetar, with an ultra-strong magnetic field capable of stripping information from a credit card at a distance halfway to the Moon. Only about 10 magnetars are known among the many neutrons stars in the Milky Way.

“Fortunately, there are no magnetars anywhere near the earth. An explosion like this within a few trillion miles could really ruin our day,” said graduate student Yosi Gelfand (CfA), a co-author on one of the papers.

The magnetar’s powerful magnetic field generated the gamma-ray flare in a violent process known as magnetic reconnection, which releases huge amounts of energy. The same process on a much smaller scale creates solar flares.

“This eruption was a super-super-super solar flare in terms of energy released,” said Gaensler.

Using the VLA and three other radio telescopes, Gaensler and his team detected material ejected by the blast at a velocity three-tenths the speed of light. The extreme speed, combined with the close-up view, yielded changes in a matter of days.

Spotting such a nearby gamma-ray flare offered scientists an incredible advantage, allowing them to study it in more detail than ever before. “We can see the structure of the flare’s aftermath, and we can watch it change from day to day. That combination is completely unprecedented,” said Gaensler.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: CfA News Release

Posted on by Fraser Cain

Gmail Invites? I’ve Got Plenty Now

Google seems to have given me a bottomless set of Gmail invites, so I’ve got plenty now. If anyone wants to try out this free web-based email, send me an email at [email protected] and I’ll give you an invite. My favorite part about Gmail? It doesn’t classify Universe Today as SPAM, unlike Hotmail and Yahoo. 😉 (Oh, and if you do switch your email address, make sure you switch your subscription to Universe Today too.)

Fraser Cain
Publisher
Universe Today

P.S. A big thanks to Chris Uzal, who’s been helping to edit Universe Today for the last week, it’s been a big help.

Posted on by Fraser Cain

Fastest Spinning Pulsar Found

A scientific researcher from the University of Southampton is leading an international team that has discovered the fastest-yet-seen accreting X-ray pulsar.

Dr Simon Shaw of the University’s School of Physics and Astronomy is UK representative to the INTEGRAL Science Data Centre near Geneva, Switzerland (ISDC is part of the Geneva University Observatory). There he co-ordinates a team that receives and monitors data from INTEGRAL, a European Space Agency (ESA) satellite designed to detect X and gamma-ray radiation from space.

A previously unknown, bright source of X-rays was first spotted in INTEGRAL data at the ISDC in December 2004. It was named ‘IGR J00291+5934’ and its discovery was announced to astronomers around the world shortly after. Follow-up observations made in the next few weeks, during which time the source slowly faded, showed that IGR J00291+5934 was the fastest known accreting binary X-ray pulsar.

A binary system is formed of two stars orbiting each other. If one of these stars undergoes a super-nova explosion it may collapse to form a ‘neutron star’ – an object composed entirely of neutrons. Neutron stars are incredibly dense, weighing slightly more than our Sun but compacted into a sphere with a size similar to Southampton; a spoonful of neutron star material would weigh about the same as the total weight of every person on Earth.

The strong gravitational field around the neutron star causes material to be pulled off the orbiting star, which spirals onto the neutron star, in a process known as ‘accretion’. The magnetic field of the neutron star causes the accreted matter to be channelled onto small ‘hot-spots’ on the neutron star surface where they radiate X and gamma-rays. A ‘pulsar’ is observed when regular flashes, or pulsations, are seen from the hot-spots as the neutron star spins; this can be thought of in exactly the same way as the periodic flashes seen from the rotating beam of light in a lighthouse.

However, this particular lighthouse is rotating approximately 600 times a second, equivalent to the surface of the pulsar moving at 30,000 km/second (10 per cent of the speed of light) – the fastest of its kind yet observed. The orbital period of the system is also impressive; the two stars orbit each other every 2.5 hours, but are separated by roughly the same distance as the Moon and the Earth. On the pulsar in IGR J00291+5934 a day lasts 0.0016 seconds and a year is 147 minutes!

‘The rate at which this object is spinning is truly amazing,’ commented Dr Shaw. ‘It gives us an opportunity to study the effects of such extreme forces of this rotation on the exotic material found in neutron stars, which does not exist on Earth. It is possible that there are more of these objects waiting to be discovered, possibly even faster ones; if they are there, INTEGRAL will find them.’

Dr Shaw is the lead author of a paper on the object accepted for publication by the journal Astronomy and Astrophysics. Pre-print available from http://arxiv.org/abs/astro-ph/0501507

Original Source:
University of Southampton News Release

Posted on by Fraser Cain

A Dozen New Planets Discovered

The past four weeks have been heady ones in the planet-finding world: Three teams of astronomers announced the discovery of 12 previously unknown worlds, bringing the total count of planets outside our solar system to 145.

Just a decade ago, scientists knew of only the nine planets – those in our local solar system. In 1995, improved detection techniques produced the first solid evidence of a planet circling another star. A proliferation of discoveries followed, and now dozens of ongoing search efforts around the globe add steadily to the roster of worlds. Most of these planets differ markedly from the planets in our own solar system. They are more similar to Jupiter or Saturn than to Earth, and are considered unlikely to support life as we know it.

The news of the past four weeks has included:

* The discovery of six new gas-giant planets by two teams of European planet-hunters was announced this week. Two of these planets are similar in mass to Saturn; three belong to a class known as “hot jupiters” because of their close proximity to the host stars. The sixth is a gas giant at least four-and-a-half times the mass of Jupiter.

All were discovered as part of the High Accuracy Radial velocity Planet Search (HARPS), an ongoing search program based at La Silla Observatory in Chile.

* On January 20, a paper posted in the online edition of the Astrophysical Journal described five new gas-giant type planets detected by a team of U.S. astronomers. These planets provide further statistical information about the distribution and properties of planetary systems, according to the paper.

The U.S. team based its finding on observations obtained at the W.M. Keck Observatory in Hawaii, which is jointly operated by the University of California and Caltech. Observation time was granted by both NASA and the University of California.

* Last week, Penn State’s Alex Wolszczan and Caltech’s Maciej Konacki announced the discovery of the smallest planet-like body detected beyond our solar system. The object belongs to a strange class known as “pulsar planets.” It is about one-fifth the size of Pluto and orbits a rapidly spinning neutron star, called a pulsar.

A pulsar is a dense and compact star that forms from the collapsing core left over from the death of a massive star. The new pulsar planet is the fourth to be discovered; all orbit the same pulsar, named PSR B1257+12.

Because the planets around the pulsar are continually strafed by high-energy radiation, they are considered extremely inhospitable to life. (Note: The current planet count posted on this website includes only planets around normal stars.)

Two methods of detection
The pulsar planet was discovered by observing the neutron star’s pulse arrival times, called pulsar timing. Variations in these pulses give astronomers an extremely precise method for detecting the phenomena that occur within a pulsar’s environment.

The gas-giant planets were detected using the radial velocity method, which infers the presence of an unseen companion because of the back-and-forth movement induced in the host star. This movement is detectable as a periodic red shift and blue shift in the star’s spectral lines. (For more about this method, see the article Finding Planets.)

The names of the new planets around main sequence stars are:

* HD 2638 b
* HD 27894 b
* HD 63454 b
* HD 102117 b
* HD 93083 b
* HD 142022A b
* HD 45350 b
* HD 99492 b
* HD 117207 b
* HD 183263 b
* HD 188015 b

Original Source: NASA Astrobiology Report

Posted on by Fraser Cain

Signs of Underground Life on Mars

NASA researchers believe they’ve found strong evidence that there could be underground life on Mars, huddled around pockets of liquid water. They haven’t found the life directly, but instead have discovered a unique methane signature that matches similar environments here on Earth, such as subsurface areas around Rio Tinto, a red-stained river in Spain. In order to get confirmation, NASA would need to send a spacecraft to Mars capable of drilling into the ground – unfortunately, none are planned currently.