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.

Posted on by Fraser Cain

Close Up on Enceladus

This image was taken during Cassini’s first close approach to Enceladus.

The image was taken on February 17, 2005 in visible light with the narrow angle camera from a distance of approximately 10,750 kilometers (6,680 miles). Resolution in the image is 60 meters (197 feet) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Original Source: NASA/JPL/SSI Release

Posted on by Fraser Cain

Galaxy Clusters Formed Early

Image credit: Subaru Telescope
Galaxies often congregate to form clusters of galaxies. At the present day, clusters have tens and hundreds of member galaxies and are the largest astronomical objects in the Universe. Knowing how they formed is a key to understanding the past and future of the Universe.

To study how the Universe has changed over large scales in space and time, it is essential to observe deeply a wide area of the sky. A large number of researchers are now studying the Subaru-XMM Deep Survey Field (SXDS), an approximately one square degree area of the sky in the direction of the constellation Cetus, the Whale, at many wavelengths using several telescopes. (Note 1)

To understand the origin of galaxy clusters, Masami Ouchi, currently at the Space Telescope Science Institute, decided to study how galaxies approximately 12.7 billion light years away (a red shift of 5.7) were distributed in the SXDS. By using the color of galaxies as a guide to their distance, Ouchi and his collaborators found 515 galaxies in a volume 500 million light years in height and width and 100 million light years in depth in images from Subaru’s prime focus camera (Suprime-Cam). (Note 2)

Figure 1 shows a density map of the galaxies in this volume as seen on the sky. This map represents the physical structures in the Universe at the farthest distances and the earliest times that astronomers have been able to observe to date. The yellow regions are where there are the highest concentration of galaxies. (Note 3)

In the bottom portion of this map, the researchers found a concentration of galaxies that could not be explained by chance. By obtaining accurate distance estimates to these galaxies using Subaru’s Faint Object Camera and Spectrograph (FOCAS), the researchers confirmed that there were six galaxies concentrated in a small volume only 3 million light years in diameter, forming a galaxy cluster. Figure 2 identifies the six member galaxies of the cluster.

The cluster has several properties that reveal its young age. It is one hundred times less massive than present day galaxy clusters and has significantly fewer members. Moreover, its member galaxies are producing stars at one hundred times the rate of galaxies outside the cluster.

The infant galaxy cluster existed at a time when the Universe was only one billion years old. The youngest portraits of galaxy clusters that astronomers previously had were from the Universe at an age of one and a half billion years. As any parent would attest, young children change rapidly. The portrait of a galaxy cluster at a younger age fills a significant gap in our knowledge of the early history of the Universe when stars, galaxies, and clusters were first forming.

“The fact that a cluster is already forming so soon after the Big Bang puts strong constraints on the fundamental structure of the Universe”, says Ouchi. The prevailing theory of cosmology postulates that smaller mass structures form first and then grow into more massive structures. “Our results seem to contradict the prevailing wisdom, but the real challenge is in understanding how well the distribution of visible matter such as galaxies correlates with the distribution of mass in general. As we continue to fill in the gaps in the early history of clusters, we should be able to resolve such ambiguities”, he says.

These results were published in the February 10, 2005, edition of the Astrophysical Journal (ApJ 620, L1-L4) and will be presented at the meeting “The Future of cosmology with clusters of Galaxies” beginning on February 26, 2005, in Waikoloa, Hawaii.

Note 1: For more information on the Subaru/XMM-Newton Deep Survey field, see the June 2004 press release on the SXDS public data release and the SXDS home page.

Note 2 : For more information on how astronomers use colors to look for distant galaxies see the March 2003 press release on the discovery of one the most distant galaxies currently known.

Note 3: Maps of the cosmic microwave background such as those from COBE or WMAP show the unevenness in the heat left over from the Big Bang that eventually led to the physical structures revealed in the new map.

Original Source: Subaru Telescope News Release

Posted on by Fraser Cain

Saturn’s Mysterious Auroras Explained

Scientists studying data from NASA’s Cassini spacecraft and Hubble Space Telescope have found that Saturn’s auroras behave differently than scientists have believed for the last 25 years.

The researchers, led by John Clarke of Boston University, found the planet’s auroras, long thought of as a cross between those of Earth and Jupiter, are fundamentally unlike those observed on either of the other two planets. The team analyzing Cassini data includes Dr. Frank Crary, a research scientist at Southwest Research Institute in San Antonio, Texas, and Dr. William Kurth, a research scientist at the University of Iowa, Iowa City.

Hubble snapped ultraviolet pictures of Saturn’s auroras over several weeks, while Cassini’s radio and plasma wave science instrument recorded the boost in radio emissions from the same regions, and the Cassini plasma spectrometer and magnetometer instruments measured the intensity of the aurora with the pressure of the solar wind. These sets of measurements were combined to yield the most accurate glimpse yet of Saturn’s auroras and the role of the solar wind in generating them. The results will be published in the February 17 issue of the journal Nature.

The findings show that Saturn’s auroras vary from day to day, as they do on Earth, moving around on some days and remaining stationary on others. But compared to Earth, where dramatic brightening of the auroras lasts only about 10 minutes, Saturn’s can last for days.

The observations also show that the Sun’s magnetic field and solar wind may play a much larger role in Saturn’s auroras than previously suspected. Hubble images show that auroras sometimes stay still as the planet rotates beneath, like on Earth, but also show that the auroras sometimes move along with Saturn as it spins on its axis, like on Jupiter. This difference suggests that Saturn’s auroras are driven in an unexpected manner by the Sun’s magnetic field and the solar wind, not by the direction of the solar wind’s magnetic field.

“Both Earth’s and Saturn’s auroras are driven by shock waves in the solar wind and induced electric fields,” said Crary. “One big surprise was that the magnetic field imbedded in the solar wind plays a smaller role at Saturn.”

At Earth, when the solar wind’s magnetic field points southward (opposite to the direction of the Earth’s magnetic field), the magnetic fields partially cancel out, and the magnetosphere is “open”. This lets the solar wind pressure and electric fields in, and allows them to have a strong effect on the aurora. If the solar wind’s magnetic field isn’t southward, the magnetosphere is “closed” and solar wind pressure and electric fields can’t get in. “Near Saturn, we saw a solar wind magnetic field that was never strongly north or south. The direction of the solar wind magnetic field didn’t have much effect on the aurora. Despite this, the solar wind pressure and electric field were still strongly affecting auroral activity,” added Crary. Seen from space, an aurora appears as a ring of energy circling a planet’s polar region. Auroral displays are spurred when charged particles in space interact with a planet’s magnetosphere and stream into the upper atmosphere. Collisions with atoms and molecules produce flashes of radiant energy in the form of light. Radio waves are generated by electrons as they fall toward the planet.

The team observed that even though Saturn’s auroras do share characteristics with the other planets, they are fundamentally unlike those on either Earth or Jupiter. When Saturn’s auroras become brighter and thus more powerful, the ring of energy encircling the pole shrinks in diameter. At Saturn, unlike either of the other two planets, auroras become brighter on the day-night boundary of the planet which is also where magnetic storms increase in intensity. At certain times, Saturn’s auroral ring is more like a spiral, its ends not connected as the magnetic storm circles the pole.

The new results do show some similarities between Saturn’s and Earth’s auroras: Radio waves appear to be tied to the brightest auroral spots. “We know that at Earth, similar radio waves come from bright auroral arcs, and the same appears to be true at Saturn,” said Kurth. “This similarity tells us that, on the smallest scales, the physics that generate these radio waves are just like what goes on at Earth, in spite of the differences in the location and behavior of the aurora.”

Now with Cassini in orbit around Saturn, the team will be able to take a more direct look at the how the planet’s auroras are generated. They will next probe how the Sun’s magnetic field may fuel Saturn’s auroras and learn more details about what role the solar wind may play. Understanding Saturn’s magnetosphere is one of the major science goals of the Cassini mission.

For the latest images and information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

The Cassini-Huygens mission is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Office of Space Science, Washington, D.C.

Original Source: NASA/JPL News Release