Jane Houston Jones from JPL provides a preview of what you can expect to see in the night skies in May, 2011.
A New Spin on Galactic Evolution
There’s a new concept in the works regarding the evolution of galactic arms and how they move across the structure of spiral galaxies. Robert Grand, a postgraduate student at University College London’s Mullard Space Science Laboratory, used new computer modeling to suggest that these signature features of spiral galaxies – including our own Milky Way – evolve in different ways than previously thought.
The currently accepted theory is as spiral galaxies rotate, the “arms” are actually transient structures that move across the flattened disc of stars surrounding the galactic bulge, yet don’t directly affect the movement of the individual stars themselves. This would work in much the same way as a “wave” goes across a crowd at a stadium event. The wave moves, but the individual people do not move along with it – rather, they stay seated after it has passed.
However when Grand researched this suggested motion using computer models of galaxies, he and his colleagues found that this was not what tended to happen. Instead the stars actually moved along with the arms, rather than maintaining their positions.
Also it was observed in these models that the arms themselves are not permanent features, but rather break up and reform over the course of 80 to 100 million years. Grand suggests that this may be due to the powerful gravitational shear forces generated by the spinning of the galaxy.
“We simulated the evolution of spiral arms for a galaxy with five million stars over a period of 6 billion years. We found that stars are able to migrate much more efficiently than anyone previously thought. The stars are trapped and move along the arm by their gravitational influence, but we think that eventually the arm breaks up due to the shear forces.”
– Robert Grand
The computer models also showed that the stars along the leading edge of the arms tended to move inwards toward the galactic center while the stars lining the trailing ends were carried to the outer edge of the galaxy.
Since it takes hundreds of millions of years for a spiral galaxy to complete even just one single rotation, observing their evolution and morphology is impossible to do in real time. Researchers like Grand and his simulations are key to our eventual understanding of how these islands of stars formed and continue to shape themselves into the vast, varied structures we see today.
“This research has many potential implications for future observational astronomy, like the European Space Agency’s next corner stone mission, Gaia, which MSSL is also heavily involved in. As well as helping us understand the evolution of our own galaxy, it may have applications for regions of star formation.”
– Robert Grand
The results were presented at the Royal Astronomical Society’s National Astronomy Meeting in Wales on April 20. Read the press release on the Royal Astronomical Society’s website here.
Top image: M81, a spiral galaxy similar to our own Milky Way, is one of the brightest galaxies that can be seen from Earth. The spiral arms wind all the way down into the nucleus and are made up of young, bluish, hot stars formed in the past few million years, while the central bulge contains older, redder stars. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)
Behind the Scenes at SpaceX’s Space Launch Complex 40
[/caption]
CAPE CANAVERAL – Space Exploration Technologies (SpaceX) took members of the media on a tour of Launch Complex 40, where the NewSpace firm has successfully launched two of its Falcon 9 rockets and one of its Dragon spacecraft (the first entity other than nations or government bodies to do so). For the media, this tour was an eye-opening experience.
SpaceX had obviously worked long and hard to allow the world to get a grasp what it is that they are doing – while at the same time avoiding International Travel in Arms Regulations (ITAR) related issues. In a well-choreographed affair the tour was split into two separate groups, one checked out the Falcon 9 hangar, while the other group inspected the launch pad that sent last December’s Falcon 9 flight on its date with history.
One enters the hangar and is greeted by the impressive site of nine Merlin engines facing them – the business end of the next Falcon 9 rocket being prepped for launched. Despite the eye-candy on display it is the simple elegance of what is described that sells this place. The horizontally integration system allows the rocket to be extremely mobile (about four people could move one of the rocket’s stages around). The system’s frictionless design is what allows SpaceX such ease of mobility.
“Our concept of operations is unlike anybody else’s that is flying these days with the exception of the Russians and maybe Sea Launch,” said SpaceX’s Director of Mission Assurance and Integration Scott Henderson. “We use horizontal integration, we will build an entire booster here in the hangar so you have the first stage and the interstage are here now, the second stage will arrive, the Dragon and trunk will arrive and we’ll put all that together, test it inside the hangar and then when we are ready to roll out for launch we’ll open this hangar door, you saw the vertical transporter-erector outside, that would lower down on pistons, we’d roll that whole structure…into the hangar drive the transporter-erector beneath the rocket, then roll out to the launch pad and lift it vertical.”
After this segment of the tour wraps up we move outside to the launch pad. The most striking contrast to other launch sites at Kennedy Space Center and Cape Canaveral Air Force Station is that it isn’t vertically-based. Rather the Falcon 9 rolls out horizontally and is moved into the vertical position much in the same way as the Russian Soyuz and Progress vehicles are. Also, the launch pad has been simplified, this highlights SpaceX’s philosophy as well as helps the company. If something does get damaged during launch, it requires minimal effort to repair and reset the launch pad for the next mission on the horizon.
Transiting Super-Earth Detected Around Naked Eye Star
One of the first known stars to host an extrasolar planet, was that of 55 Cancri. The first planet in this system was reported in 1997 and today the system is known to host at least five planets, the inner most of which, 55 Cnc e, was recently discovered to transit the star, giving new information about this planet.
55 Cnc is an interesting system in many respects. Being a mere 41 lightyears from the Earth, the system is composed of a primary, yellow dwarf star in a wide binary orbit (1,000 AU) with a red dwarf. The planetary system lies within this orbit. The primary star is just brighter than 6th magnitude meaning it is visible to the naked eye under good viewing conditions.
One of these planets, 55 Cnc e, was discovered in this system via radial velocity measurements in 2004. At that point, the planet was reported to have a period of 2.8 days, and a minimum mass of 14.2 times the mass of the Earth. However, in 2010, Rebekah Dawson and Daniel Fabrycky from the Harvard-Smithsonian Center for Astrophysics argued that gaps in the observational period skewed the statistics and the true period the planet should be a short 0.7365 days.
One of the results of this was that the planet would have to orbit closer to the parent star. In turn, this increased the likelihood that the planet could transit the star from 13% to 33%. A team led by Joshua Winn from the Massachusetts Institute of Technology went searching for this faint transit and report its detection in a recent paper. But while the star itself is one of the brightest stars in our sky to harbor known extrasolar planets, the eclipse is far from visible without precise observations, changing by only 0.0002%, one of the smallest changes known. The timing of the eclipses confirms that correction by Dawson and Fabrycky and adds new information about the body.
Given the radius determined as well as the mass, the team was able to estimate the structure of the planet and report that the mass is 8.57 ± 0.64 Earth masses. The reported radius is 1.63 ± 0.16 times that of Earth, and the density is 10.9 ± 3.1 g cm-3 (the average density of Earth is 5.515 g cm-3). This places the planet firmly into the categories of a rocky super-Earth.
The team also explores whether or not the planet could retain an atmosphere in such a close orbit (only three times the radius of the star itself). At this close range, the planet would likely be tidally locked and with an albedo typical of rocky planets, the planet would likely have an average temperature of nearly 2970 K (5,000° F). If the planet were able to redistribute the heat, it may be as low as 2100 K (3,300° F). Either way, a planet of such mass would have difficulty retaining any primordial, gaseous atmosphere. However, the team reports that it may be possible for volcanic activity to create a thin atmosphere of high molecular weight components.
While this new report adds precious little in the grand scheme of the rapidly growing body of knowledge of exoplanets, the authors close with the note that, “there is some pleasure in being able to point to a naked-eye star and know the mass and radius of one of its planets.”
Endeavour’s Final Launch further delayed another Week or more
[/caption]
KENNEDY SPACE CENTER – The final launch of shuttle Endeavour will be further delayed, perhaps by a week or more – to May 6 or 11 time frame – as technicians working at the pad seek to determine the cause of the failure of multiple heaters in auxiliary power unit-1 (APU) which caused the scrub of Endeavour’s launch attempt on Friday, with just 4 hours remaining in the countdown. The six man crew of Endeavour had just departed for the launch pad inside the Astrovan and was forced to turn around soon thereafter. We saw them pass us by, heading back to crew quarters to await a resolution of the issues.
The launch delay came as a huge disappointment to NASA and the enormous crowd estimated at 750.000 people who came to Florida to watch the momentous liftoff in person for what many call a “life changing experience”. Even President Obama and the entire first family were on hand to witness Endeavour’s launch. But the top priority is to launch the shuttle safely and the launch team emphasized that they made absolutely no changes to the countdown procedures.
APU-1 is located on the left side of the orbiter in the aft section behind the end of the payload bay.
The heaters play a critical role in keeping the APU hydrazine fuel from freezing in orbit and remain in a fluid state. If the hydrazine were to freeze and then thaw back to a liquid, it would expand and potentially rupture the fuel lines with devastating consequences.
The orbiter has three APU’s. Only one is required to fly safely. Three units provide redundancy and all must be in working order before launch. Otherwise the launch commit criteria would be violated, forcing a launch scrub. The APUs provide the hydraulics to maneuver the main engine nozzles, elevons, rudder, body flap, landing gear brakes and nose wheel steering system.
Technical teams got to work inside the orbiter on Saturday after the rotating service structure was rolled back around the orbiter to enable access. If the problem is deeper within the orbiter at the Load Control Assembly it will take several additional days to fix the problem. Retesting of any new components inside the LCA will take at least 48 hours. Furthermore if any ordnance needs to be disconnected, a further delay of multiple additional days is inevitable.
In order to launch Endeavour on Monday, May 2, at 2:34 p.m. EDT, NASA must resume the countdown on Sunday afternoon. NASA only has until May 4 to get Endeavour off the ground until they would be forced to stand down to make way for the May 6 blastoff of an Atlas V rocket carrying an Air Force early-warning missile detection satellite.
NASA officials are in touch with Air Force officials to determine if the Air Force could be flexible in changing their launch date in the event that Endeavour would be ready to launch on the blackout dates of May 5 to 7.
NASA will hold a news briefing at 2 p.m. on Sunday to update reporters on the situation.
Read my related stories about the STS-134 mission here:
On the Cusp of Endeavour’s Final Flight
Brush Fires Erupt at Kennedy Space Center during Endeavour’s Last Countdown
Commander Mark Kelly and STS-134 Crew Arrive at Kennedy for Endeavour’s Final Flight
President Obama to Attend Endeavour’s Last Launch on April 29
Shuttle Endeavour Photo Special: On Top of Pad 39A for Final Flight
Endeavour Mated to Rockets for Last Flight Photo Album
Endeavour Rolls to Vehicle Assembly Building for Final Flight
Timelapse: Shuttle RSS Retract
Here’s an amazing, quick look at the Rotating Service Structure being moved away from around space shuttle Endeavour late last Thursday night. David Gonzales and Mike Deep from Project Soar created this timelapse for Universe Today, and David said being able to see the shuttle up close reinforced that the shuttle really is a machine of beauty.
Look for more timelapse and special projects by David and Mike here on Universe Today.
Astronomy Without A Telescope – Cosmic Magnetic Fields
[/caption]
The mention of cosmic-scale magnetic fields is still likely to met with an uncomfortable silence in some astronomical circles – and after a bit of foot-shuffling and throat-clearing, the discussion will be moved on to safer topics. But look, they’re out there. They probably do play a role in galaxy evolution, if not galaxy formation – and are certainly a feature of the interstellar medium and the intergalactic medium.
It is expected that the next generation of radio telescopes, such as LOFAR (Low Frequency Array) and the SKA (Square Kilometre Array), will make it possible to map these fields in unprecedented detail – so even if it turns out that cosmic magnetic fields only play a trivial role in large-scale cosmology – it’s at least worth having a look.
At the stellar level, magnetic fields play a key role in star formation, by enabling a protostar to unload angular momentum. Essentially, the protostar’s spin is slowed by magnetic drag against the surrounding accretion disk – which allows the protostar to keep drawing in more mass without spinning itself apart.
At the galactic level, accretion disks around stellar-sized black holes create jets that inject hot ionised material into the interstellar medium – while central supermassive black holes may create jets that inject such material into the intergalactic medium.
Within galaxies, ‘seed’ magnetic fields may arise from the turbulent flow of ionised material, perhaps further stirred up by supernova explosions. In disk galaxies, such seed fields may then be further amplified by a dynamo effect arising from being drawn into the rotational flow of the whole galaxy. Such galactic scale magnetic fields are often seen forming spiral patterns across a disk galaxy, as well as showing some vertical structure within a galactic halo.
Similar seed fields may arise in the intergalactic medium – or at least the intracluster medium. It’s not clear whether the great voids between galactic clusters would contain a sufficient density of charged particles to generate significant magnetic fields.
Seed fields in the intracluster medium might be amplified by a degree of turbulent flow driven by supermassive black hole jets but, in the absence of more data, we might assume that such fields maybe more diffuse and disorganised that those seen within galaxies.
The strength of intracluster magnetic fields averages around 3 x 10-6 gauss (G), which isn’t a lot. The Earth’s magnetic fields averages around 0.5 G and a refrigerator magnet is about 50 G. Nonetheless, these intracluster fields offer the opportunity to trace back past interactions between galaxies or clusters (e.g. collisions or mergers) – and perhaps to determine what role magnetic fields played in the early universe, particularly with respect to the formation of the first stars and galaxies.
Magnetic fields can be indirectly identified through a variety of phenomena:
• Optical light is partly polarised by the presence of dust grains which are drawn into a particular orientation by a magnetic field and then only let through light in a certain plane.
• At a larger scale, Faraday rotation comes into play, where the plane of already polarised light is rotated in the presence of a magnetic field.
• There’s also Zeeman splitting, where spectral lines – which normally identify the presence of elements such as hydrogen – may become split in light that has passed through a magnetic field.
Wide angle or all-sky surveys of synchrotron radiation sources (e.g. pulsars and blazars) allow measurement of a grid of data points, which may undergo Faraday rotation as a result of magnetic fields at the intergalactic or intracluster scale. It is anticipated the high resolution offered by the SKA will enable observations of magnetic fields in the early universe back to a redshift of about z =5, which gives you a view of the universe as it was about 12 billion years ago.
Further reading: Beck, R. Cosmic Magnetic Fields: Observations and Prospects.
The Early Morning Show – Eta Aquarid Meteor Showers While The Planets Align
[/caption]
Are you ready for the Eta Aquarid Meteor Shower? While the peak activity will be on the night of May 5/6, the offspring of Comet Halley are already beginning to make their appearance known. No matter where you live or what time zone you observe from, the best time to look for “shooting stars” is over the next week or so during the hours just before dawn.
Somewhere in the outer reaches of our solar system beyond the orbit of Jupiter, Comet Halley continues on its track – far away from its 1986 debris trail. However, now isn’t the only time we encounter this famous comet’s leftovers. Three times a year the Earth cruises through the dusty trail causing the Eta Aquarids, the Beta Aquarids (both in May) and the Orionids (during October). When a piece of this debris enters our atmosphere, it is traveling about 66 kilometers per second and can shine as brightly as the stars (3rd magnitude) in the constellation from which it appears to originate. Encountering a dense paticle stream may spark activity of up to 70 meteors per hour for lucky observers in the southern hemisphere, but don’t count yourself out if you live in the north! Because the constellation of Aquarius is relatively low for northern observers, this means we have at least a better chance of spotting those breathtaking Earth grazers!
Don’t be discouraged if you’re clouded out or unable to view at the peak time. The most wonderful part about the Eta Aquarids is the fact the stream is very broad and activity is extended from April 21 until May 12. And there’s an added treat – the ongoing planetary alignment…
Don’t let anyone discourage you from watching the Eta Aquarids if you have an opportunity. While it isn’t one of the most prolific showers of the year for the north, it is very well established and having dark skies will help tremendously. There is nothing finer than cradling a cup of hot coffee, sneaking a donut and waiting on the dawn while watching Kepler’s Laws of planetary motion in action. I am sure that you’ll come away feeling very happy indeed that you took the time to look for Comet Halley’s children racing by!
Why Endeavour scrubbed on Friday
We were not in the Spacevidcast studios for this one, but I kept getting questions about the APU and why we scrubbed. Thought it wise to create a quick little SpacePod to explain why the final launch of Space Shuttle Endeavour was delayed to No Earlier Than Monday, May 2nd, 2011.
Weekend Observing Project: T Pyxidis
Are you ready to observe a nova event which can be caught in simple binoculars? Then open your eyes wide and locate T Pyxidis! Right now it’s showing up as just slightly fainter than magnitude 7, which means it is going to appear as an “extra star” in an otherwise rather starless portion of the constellation of Pyxis. Are you ready? Then let’s dance…
T Pyxidis is actually a binary star – one much like our own Sun with a white dwarf companion. Thanks to its diminuative, heavy-weight companion, matter from the primary star is always being drawn toward the secondary causing periodic thermonuclear explosions. Since there hasn’t been any real activity in about 45 years, astronomers believed T Pyx could possibly have began evolving into an entirely new system and activity wouldn’t occur perhaps for centuries. But they were wrong…
With a normal magnitude of 15.5, T Pyxidis would only be visible to some of the largest of amateur telescopes, but right now it can easily be spotted with average binoculars. The first finder chart seen on this page will get you in the right area and the one below will get you spot on (RA 09h 04m 41.50s Dec -32° 22′ 47.5″).
The fun part about observing T Pxidis is that it’s an object well suited for both hemispheres – one where the south is a bit more favored than the north – and all the “buzz” that goes with it. According to many sources, the white dwarf may be nearing its Chandrasekhar limit and become a Type 1a supernova when it collapses under its own weight. Says Edward Sion (et al); “The recurrent nova T Pyxidis has had 5 recorded thermonuclear explosions, more than any other recurrent nova, with an average time between nova outbursts of 19 years. However, it has been 44 years since its last nova outburst in 1966, making it long overdue for the next nova (supernova?). ”
However, don’t worry about this 3,300 light year distant stellar explosion happening any time soon. It’s estimated that kind of action may take as long as another couple of million years. “A key fact about T Pyx is that its accretion rate has been secularly declining since before the 1890 eruption, with the current rate being only 3% of its earlier rate. The decline in the observed accretion rate shows that the supersoft source is not self-sustaining, and we calculate that the accretion in T Pyx will effectively stop in upcoming decades.” say Bradley E. Schaefer (et al). “With this, T Pyx will enter a state of hibernation, lasting for an estimated 2,600,000 years, before gravitational radiation brings the system into contact again. Thus, T Pyx has an evolutionary cycle going from an ordinary CV state, to its current RN state, to a future hibernation state, and then repeating this cycle.”
But don’t you wait that long to observe it. For the next week or so, the Moon won’t interfere with your early evening chance to see this very cool cosmic customer!