Astronomy Archives

January 29, 2015January 3, 2016 by Tim Reyes

Elon Musk and the SpaceX Odyssey: the Path from Falcon 9 to Mars Colonization Transporter

ILLUSTRATION IS RESERVED - DO NOT USE. Are we seeing the convergence of a century of space science and science fiction before our eyes? Will Musk and SpaceX make 2001 Space Odyssey a reality? (Photo Credit: NASA, Apple, SpaceX, Tesla Motors, MGM, Paramount Pictures, Illustration – Judy Schmidt)

In Kubrick’s and Clark’s 2001 Space Odyssey, there was no question of “Boots or Bots”[ref]. The monolith had been left for humanity as a mileage and direction marker on Route 66 to the stars. So we went to Jupiter and Dave Bowman overcame a sentient machine, shut it down cold and went forth to discover the greatest story yet to be told.

Now Elon Musk, born three years after the great science fiction movie and one year before the last Apollo mission to the Moon has set his goals, is achieving milestones to lift humans beyond low-Earth orbit, beyond the bonds of Earth’s gravity and take us to the first stop in the final frontier – Mars – the destination of the SpaceX odyssey.

Marvel claims Musk as the inspiration for Tony Stark in Ironman but for countless space advocates around the World he is the embodiment of Dave Bowman, the astronaut in 2001 Space Odyssey destined to travel to the edge of the Universe and retire an old man on Mars. (Photo Credit: NASA, MGM, Paramount Pictures, Illustration – Judy Schmidt)

Ask him what’s next and nowhere on his bucket list does he have Disneyland or Disney World. You will find Falcon 9R, Falcon Heavy, Dragon Crew, Raptor Engine and Mars Colonization Transporter (MCT).

At the top of his working list is the continued clean launch record of the Falcon 9 and beside that must-have is the milestone of a soft landing of a Falcon 9 core. To reach this milestone, Elon Musk has an impressive array of successes and also failures – necessary, to-be-expected and effectively of equal value. His plans for tomorrow are keeping us on the edge of our seats.

The Dragn Crew capsule is more than a modernized Apollo capsule. It will land softly and at least on Earth will be reusable while Musk and SpaceX dream of landing Falcon Crew on Mars. (Photo Credits: SpaceX) — The Dragon Crew capsule is more than a modernized Apollo capsule. It will land softly and at least on Earth will be reusable while Musk and SpaceX dream of landing Falcon Crew on Mars. (Photo Credits: SpaceX)

CRS-5, the Cargo Resupply mission number 5, was an unadulterated success and to make it even better, Elon’s crew took another step towards the first soft landing of a Falcon core, even though it wasn’t entirely successful. Elon explained that they ran out of hydaulic fluid. Additionally, there is a slew of telemetry that his engineers are analyzing to optimize the control software. Could it have been just a shortage of fluid? Yes, it’s possible they could extrapolate the performance that was cut short and recognize the landing Musk and crew dreamed of.

A successful failure of a soft landing had no baring on the successful launch of the CRS-5, the cargo resupply mission to ISS. (Image Credits: SpaceX)

The addition of the new grid fins to improve control both assured the observed level of success and also assured failure. Anytime one adds something unproven to a test vehicle, the risk of failure is raised. This was a fantastic failure that provided a treasure trove of new telemetry and the possibilities to optimize software. More hydraulic fluid is a must but improvements to SpaceX software is what will bring a repeatable string of Falcon core soft landings.

“Failure is not an option,” are the famous words spoken by Eugene Kranz as he’s depicted in the movie Apollo 13. Failure to Elon Musk and to all of us is an essential part of living. However, from Newton to Einstein to Hawking, the equations to describe and define how the Universe functions cannot show failure otherwise they are imperfect and must be replaced. Every moment of a human life is an intertwined array of success and failure. Referring only to the final frontier, in the worse cases, teams fall out of balance and ships fall out of the sky. Just one individual can make a difference between his or a team’s success. Failure, trial and error is a part of Elon’s and SpaceX’s success.

Only the ULA Delta IV Heavy image is real. TBC - to be completed - is the status of Delta Heavy. To be launch on its maiden flight in 2015, Falcon Heavy will become the most powerful American-made launch vehicle since Von Braun's Saturn rocket of the d1960s. (Credits: SpaceX, ULA) — Only the ULA Delta IV Heavy image is real. TBC – *to be completed* – is the status of Falcon Heavy. To be launch on its maiden flight in 2015, Falcon Heavy will become the most powerful American-made launch vehicle since Von Braun’s Saturn rocket of the d1960s. (Credits: SpaceX, ULA)

He doesn’t quote or refer to Steve Jobs but Elon Musk is his American successor. From Hyperloops, to the next generation of Tesla electric vehicles, Musk is wasting no time unloading ideas and making his dreams reality. Achieving his goals, making milestones depends also on bottom line – price and performance into profits. The Falcon rockets are under-cutting ULA EELVs (Atlas & Delta) by more than half in price per pound of payload and even more with future reuse. With Falcon Heavy he will also stake claim to the most powerful American-made rocket.

In both cost and performance the Falcon 9 and Heavy outperform the Delta IV. The Falcon vehicle is disruptive technology. (Illustration: T.Reyes)

Musk’s success will depend on demand for his product. News in the last week of his investments in worldwide space-based internet service also shows his intent to promote products that will utilize his low-cost launch solutions. The next generation of space industry could falter without investors and from the likes of Musk, re-investing to build demand for launch and sustaining young companies through their start-up phases. Build it and they will come but take for granted, not recognize the fragility of the industry, is at your own peril.

So what is next in the SpaceX Odyssey? Elon’s sights remain firmly on the Falcon 9R (Reuse) and the Falcon Heavy. Nothing revolutionary on first appearance, the Falcon Heavy will look like a Delta IV Heavy on steroids. Price and performance will determine its success – there is no comparison. It is unclear what will become of the Delta IV Heavy once the Falcon Heavy is ready for service. There may be configurations of the Delta IV with an upper stage that SpaceX cannot match for a time but either way, the US government is likely to effectively provide welfare for the Delta and even Atlas vehicles until ULA (Lockheed Martin and Boeing’s developed corporation) can develop a competitive solution. The only advantage remaining for ULA is that Falcon Heavy hasn’t launched yet. Falcon Heavy, based on Falcon 9, does carry a likelihood of success based on Falcon 9’s 13 of 13 successful launches over the last 5 years. Delta IV Heavy has had 7 of 8 successful launches over a span of 11 years.

The legacy that Elon and SpaceX stand upon is a century old. William Gerstenmaier, a native of the state of Ohio - First in Flight, associate administrator for NASA Human Spaceflight and past program manager of ISS has been a prime executor of NASA human spaceflight for two decades. Elon Musk shares in common a long-time enthusiasm for space exploration with Gerstenmaier. From top left, clockwise, Eugene Kranz, Michael Collins, Neil Armstron, Edwin (Buzz) Aldrin, W. Gerstenmaier, Michael Griffin, NASA Administrator Charles Bolden shaking hands with Elon Musk. (Photo Credits: NASA, SpaceX, Illustration, J.Schmidt/T.Reyes) — The legacy that Elon and SpaceX stand upon is a century old. The Ohio native, William Gerstenmaier, associate administrator for NASA Human Spaceflight and past program manager of ISS, like Musk and so many others, dreamed of space exploration from an early age. From top left, clockwise, Eugene Kranz, Michael Collins, Neil Armstrong, Edwin (Buzz) Aldrin, W. Gerstenmaier, Michael Griffin, NASA Administrator Charles Bolden shaking hands with Elon Musk, the Apollo 11 crew embarking on their famous voyage(center). (Photo Credits: NASA, SpaceX, Illustration, J.Schmidt/T.Reyes)

The convergence of space science and technology and science fiction in the form of Musk’s visions for SpaceX is linked to the NASA legacy beginning with NASA in 1958, accelerated by JFK in 1962 and landing upon the Moon in 1969. The legacy spans backward in time to Konstantin Tsiolkovsky, Robert Goddard, Werner Von Braun and countless engineers and forward through the Space Shuttle and Space Station era.

A snapshot from the SpaceX webpage describing their successful first flight of the Dragon Cargo vessel on Falcon 9. Musk's SpaceX could not have achieved so much so quickly without the knowledge and support of NASA. (Credit: SpaceX) — A snapshot from the SpaceX webpage describing their successful first flight of the Dragon Cargo vessel on Falcon 9. Musk’s SpaceX could not have achieved so much so quickly without the knowledge and support of NASA. (Credit: SpaceX)

The legacy of Shuttle is that NASA remained Earth-bound for 30-plus years during a time that Elon Musk grew up in South Africa and Canada and finally brought his visions to the United States. With a more daring path by NASA, the story to tell today would have been Moon bases or Mars missions completed in the 1990s and commercial space development that might have outpaced or pale in comparison to today’s. Whether Musk would be present in commercial space under this alternate reality is very uncertain. But Shuttle retirement, under-funding its successor, the Ares I & V and Orion, cancelling the whole Constellation program, then creating Commercial Crew program, led to SpaceX winning a contract and accelerated development of Falcon 9 and the Dragon capsule.

Mars as it might look to the human eye of colonists on final approach to the red planet. To Elon Musk, this is the big prize and a place to retire and relish his accomplishments if only for a brief moment. (Credit: NASA)

SpaceX is not meant to just make widgets and profit. Mars is the objective and whether by SpaceX or otherwise, it is the first stop in humankind’s journey into the final frontier. Mars is why Musk developed SpaceX. To that end, the first focal point for SpaceX has been the development of the Merlin engine.

Now, SpaceX’s plans for Mars are focusing on a new engine – Raptor and not a Merlin 2 – which will operate on liquified methane and liquid oxygen. The advantage of methane is its cleaner combustion leaving less exhaust deposits within the reusable engines. Furthermore, the Raptor will spearhead development of an engine that will land on Mar and be refueled with Methane produced from Martian natural resources.

The Raptor remains a few years off and the design is changing. A test stand has been developed for testing Raptor engine components at NASA’s Stennis Space Center. In a January Reddit chat session[ref] with enthusiasts, Elon replied that rather than being a Saturn F-1 class engine, that is, thrust of about 1.5 million lbf (foot-lbs force), his engineers are dialing down the size to optimize performance and reliability. Musk stated that plans call for Raptor engines to produce 500,000 lbf (2.2 million newtons) of thrust. While smaller, this represents a future engine that is 3 times as powerful as the present Merlin engine (700k newtons/157 klbf). It is 1/3rd the power of an F-1. Musk and company will continue to cluster engines to make big rockets.

The future line-up of Falcon rockets is compared to the famous NASA Saturn V. The first Falcon Heavy launch is planned for 2015. Raptor engines may replace and upgrade Heavy then lead to Falcon X, Falcon X Heavy and Falcon XX. The Falcon X 1st stage would have half the thrust of a Saturn V, Falcon X Heavy and XX would exceed a Saturn V's thrust by nearly 50%. (Illustration Credit: SpaceX, 2010) — The future line-up of Falcon rockets is compared to the famous NASA Saturn V. The first Falcon Heavy launch is planned for 2015. Raptor engines may replace and upgrade Heavy then lead to Falcon X, Falcon X Heavy and Falcon XX. The Falcon X 1st stage would have half the thrust of a Saturn V, Falcon X Heavy and XX would exceed a Saturn V’s thrust by nearly 50%. (Illustration Credit: SpaceX, 2010)

To achieve their ultimate goal – Mars colonization, SpaceX will require a big rocket. Elon Musk has repeatedly stated that a delivery of 100 colonists per trip is the present vision. The vision calls for the Mars Colonization Transporter (MCT). This spaceship has no publicly shared SpaceX concept illustrations as yet but more information is planned soon. A few enthusiasts on the web have shared their visions of MCT. What we can imagine is that MCT will become a interplanetary ferry.

The large vehicle is likely to be constructed in low-Earth orbit and remain in space, ferrying colonists between Earth orbit and Mars orbit. Raptor methane/LOX engines will drive it to Mars and back. Possibly, aerobraking will be employed at both ends to reduce costs. Raptor engines will be used to lift a score of passengers at a time and fill the living quarters of the waiting MCT vehicle. Once orbiting Mars, how does one deliver 100 colonists to the surface? With atmospheric pressure at its surface equivalent to Earth’s at 100,000 feet, Mars does not provide an Earth-like aerodynamics to land a large vehicle.

In between launching V-2s in New Mexico and developing rockets at Redstone Arsenal, Von Braun had time to write Mars Projekt (1952) in which he outlined a mission to Mars delivering 70 explorers. Much has changed since that early vision but some of his concepts may still become a reality and solve the problem of sending SpaceX colonists to Mars. (Credit: Mars Project, Von Braun)

In 1952, Werner Von Braun in his book “Mars Projekt” envisioned an armada of ships, each depending on launch vehicles much larger than the Saturn V he designed a decade later. Like the invading Martians of War of the Worlds, the armada would rather converge on Mars and deploy dozens of winged landing vehicles that would use selected flat Martian plain to skid with passengers to a safe landing. For now, Elon and SpaceX illustrate the landing of Dragon capsules on Mars but it will clearly require a much larger lander. Perhaps, it will use future Raptors to land softly or possibly employ winged landers such as Von Braun’s after robotic Earth-movers on Mars have constructed ten or twenty mile long runways.

We wait and see what is next for Elon Musk’s SpaceX vision, his SpaceX Odyssey. For Elon Musk and his crew, there are no “wives” – Penelope and families awaiting their arrival on Mars. Their mission is more than a five year journey such as Star Trek. The trip to Mars will take the common 7 months of a Hohmann transfer orbit but the mission is really measured in decades. In the short-term, Falcon 9 is poised to launch again in early February and will again attempt a soft landing on a barge at sea. And later, hopefully, in 2015, the Falcon Heavy will make its maiden flight from Cape Canaveral’s rebuilt launch pad 39A where the Saturn V lifted Apollo 11 to the Moon and the first, last and many Space Shuttles were launched.

References:

National Aeronatics and Space Administration

Space Exploration Web Pages

Happy Birthday to my sister Sylvia who brought home posters, literature and interest from North American-Rockwell in Downey during the Apollo era and sparked my interest.

January 28, 2015April 26, 2016 by David Dickinson

iPhone Astrophotography: How to Take Amazing Images of the Sky with Your Smartphone Tonight!

All photos credit and copyright: Andrew Symes.

Got a smartphone and a telescope?

It’s a sight now common at many star parties. Frequently, you see folks roaming through the darkness, illuminated smartphone aimed skyward. Certainly, the wealth of free planetarium apps has done lots to kindle a renewed interest in the night sky.

Inevitably, after peering through the eyepiece of a telescope, the question then arises:

“Can I get a picture of that with my phone?”

The short answer is yes, with a little skill and patience.

Now simply aiming a camera at the eyepiece of a telescope — known as afocal astrophotography — and shooting without removing the camera lens and physically coupling it to the telescope is a tricky balancing act. Back in the olden days, the Moon and perhaps the brighter planets were the only bright target within bounds of afocal film photographers, and only then after a lengthy set of estimations to hit the correct focal length. The advent of digital cameras and ‘live preview’ means that you can now simply aim, shoot, and throw away or delete anything off center or out of focus. Digital ‘film’ is cheap, and most folks simply use trial and error to get the ‘keepers’. The Moon is an especially bright and easy target for beginners to practice on.

Of course, your typical smartphone, like a webcam, has an imaging chip much smaller than a DSLR. This is why astrophotographers are often tempted to take out a second mortgage (“we don’t really need that second car, do we?” is a common spousal refrain) in pursuit of excellence. Another drawback is that through a smartphone, a planet may look like an overexposed blob. A simple but effective way to get around this is to affix a light reducing filter to the eyepiece. In fact, I’ve used a variable polarizer during live broadcasts of the Virtual Star Party to great effect. And as with webcam imaging, smartphone astrophotographers now often use automated stacking programs to clean up images and tease out detail. Being an old timer, my faves are still K3CCD Tools and Registax, though many young guns out there now use DeepSkyStacker as well.

Telescope — Andrew Symes’ imaging setup.

Now, I’ll admit, I’m an ‘Android guy,’ and I have put most of my efforts over the years into planetary imaging with a homemade webcam. We therefore sought out in-the-field expertise from someone on the forefront of iPhone astrophotography. Andrew Symes has been taking images of the solar system and beyond with his iPhone coupled to his Celestron NexStar 8” SE telescope for years. He also has one of the few handles on Twitter that we’re envious of, @FailedProtostar. He also ventures out into the chilly nights frequent to his native of Ottawa, Canada to practice his craft, as he observes in temperatures that would drop a Tauntaun.

We caught up with Andrew recently to ask him about some tips of the trade.

An ‘iPhone Sun’ shot in hydrogen alpha through a Coronado PST.

Universe Today: I know from doing webcam photography that acquiring, centering and focusing are often more than half the battle. Any tips for accomplishing these?

Andrew: Acquiring, centering, and focusing the objects I’m photographing is definitely the big challenge! To speed and simplify the process, I have a dedicated eyepiece that I use in association with my phone and adapter. Before even heading outside, I attach the adapter to this eyepiece, insert my phone, and hold the unit up to a light source to see if the camera lens is properly aligned with the eyepiece. It usually takes a bit of fiddling to get things set properly because if the adapter and eyepiece are not perfectly aligned, nothing will show up on the camera screen. It’s better to get that process out of the way in a lit environment than outside in the dark. I then set that unit aside, and use a separate “adapter-less” zoom eyepiece to locate and center the object in the telescope. Once I’ve acquired the object and am successfully tracking it, I remove my zoom eyepiece and drop in the eyepiece/adapter/phone combo. At that point, the object is usually visible on screen but out of focus since the focus required for the iPhone is different from what works for my eyes! To ensure proper focus, I display the object on my phone’s screen using a live video app called FiLMiC Pro and adjust the focus until it is sharp. I use that app because it has a digital zoom function that lets me get a closer look at the object than the standard iPhone video camera view. Only once I’m confident that I’ve achieved good focus and am tracking the object properly, will I start to record video or shoot individual frames.

A comparison of the first image of the Orion Nebula (M42) shot in 1880 (left) with a modern iPhone image.

Universe Today: A question I always like to ask everyone… what was your biggest mistake? Are there any pitfalls to avoid?

Andrew: There are a few pitfalls to avoid when doing iPhone astrophotography. In the past, I would attach the adapter outside while the eyepiece was in the telescope but this caused a number of problems. Often, I would accidentally bump the object out of view while attaching and adjusting the adapter and have to align everything all over again. The weather is also often cold here, and it’s VERY difficult to attach the adapter properly with gloves on, so I would either get really cold hands or spend a lot of unnecessary time fumbling with the adapter with gloved hands. For those reasons, I now prepare the eyepiece/adapter/phone unit indoors in advance as described above. I also now make sure that my iPhone is fully charged before heading outdoors as I’ve found that the iPhone battery drains very quickly when the camera is running constantly — especially in cold weather. Even with an almost-full battery, there are times here in winter when the phone will simply shut down due to the low temperature so I make sure to only start capturing photos/videos once I’m completely confident in my setup.

Yes, that’s Comet C/2014 Q2 Lovejoy shot with an iPhone!

Universe Today: You’re really pushing the envelope by doing deep sky astro-pics with an iPhone … anything else that you’re experimenting with or working on?

Andrew: My main focus is definitely still on iPhone astrophotography because I like the quick and “light” setup. I don’t need to bring a laptop outside and don’t need equipment that I wouldn’t normally have on me anyway (other than the adapter itself.) So, I want to keep pushing the envelope with what I can capture using the phone and my goal is now is to see how far I can go with deep-sky objects. I’d really like to add the Ring and Dumbbell Nebulae to my portfolio, for example, and see if it’s possible to grab even fainter ones. There are also some non-deep sky targets I’d like to try. I haven’t been successful at capturing a telescopic photo of the ISS, and would love to see if I can catch it transiting the Sun or Moon with my phone. I also still need to capture Uranus and Neptune to round out a solar system collage I put together in 2014!

Lastly, I’m continually experimenting with photo apps to see which are best at capturing and/or processing telescopic images, and have just started using both an iPhone 4S and iPhone 6 to take photos and video. Surprisingly, I still prefer the 4S for planetary imaging as I haven’t been able to properly capture the true colors of planets with the iPhone 6 yet. The 6 has better camera resolution but seems to be adjusting the exposure of small, faint objects like planets differently than the 4S, so I need to change my routine and techniques to compensate. The methods I’ve become accustomed to using with the 4S don’t seem to translate directly to the 6 so I have some learning yet to do!

Amazing stuff, for sure. And to think, we were all gas-hypering film and using absurdly long focal lengths to get blurry planetary images just a few decades ago!

-Check out more of Andrew’s images, as well as read more about how he does it.

-Got a pic, shot with a smartphone or otherwise? Send ‘em in to Universe Today!

January 28, 2015December 23, 2015 by Vanessa Janek

Astronomers See a Massive Black Hole Tear a Star Apart

When a star encounters a black hole, tidal forces stretch the star into an elongated blob before tearing it apart, as seen in these images from a computer simulation by James Guillochon of Harvard University.

A telescope peers into the blackness of deep space. Suddenly – a brilliant flash of light appears that wasn’t there before. What could it be? A supernova? Two massively dense stars fusing together? Perhaps a gamma ray burst?

Five years ago, researchers using the ROTSE IIIb telescope at McDonald Observatory noticed just such an event. But far from being your run-of-the-mill stellar explosion or neutron star merger, the astronomers believe that this tiny flare was, in fact, evidence of a supermassive black hole at the center of a distant galaxy, tearing a star to shreds.

Astronomers at McDonald had been using the telescope to scan the skies for such nascent flashes for years, as part of the ROTSE Supernova Verification Project (SNVP). And at first blush, the event seen in early 2009, which the researches nicknamed “Dougie,” looked just like many of the other supernovae they had discovered over the course of the project. With a blazing – 22.5-magnitude absolute brightness, the event fit squarely within the class of superluminous supernovae that the researchers were already familiar with.

But as time went on and more data on Dougie rolled in, the astronomers began to change their minds. X-ray observations made by the orbiting Swift satellite and optical spectra taken by McDonald’s Hobby-Eberly Telescope revealed an evolving light curve and chemical makeup that didn’t fit with computer simulations of superluminous supernovae. Likewise, Dougie didn’t appear to be a neutron star merger, which would have reached peak luminosity far more quickly than was observed, or a gamma ray burst, which, even at an angle, would have appeared far brighter in x-ray light.

That left only one option: a so-called “tidal disruption event,” or the carnage and spaghettification that occurs when a star wanders too close to a black hole’s horizon. J. Craig Wheeler, head of the supernova group at The University of Texas at Austin and a member of the team that discovered Dougie, explained that at short distances, a black hole’s gravity exerts a much stronger pull on the side of the star nearest to it than it does on the star’s opposite side. He explained, “These especially large tides can be strong enough that you pull the star out into a noodle.”

The team refined their models of the event and came to a surprising conclusion: having drawn in Dougie’s stellar material a bit faster than it could handle, the black hole was now “choking” on its latest meal. This is due to an astrophysical principle called the Eddington Limit, which states that a black hole of a given size can only handle so much infalling material. After this limit has been reached, any additional intake of matter exerts more outward pressure than the black hole’s gravity can compensate for. This pressure increase has a kind of rebound effect, throwing off material from the black hole’s accretion disk along with heat and light. Such a burst of energy accounts for at least part of Dougie’s brightness, but also indicates that the original dying star – a star not unlike our own Sun – wasn’t going down without a fight.

Combining these observations with the mathematics of the Eddington Limit, the researchers estimated the black hole’s size to be about 1 million solar masses – a rather small black hole, at the center of a rather small galaxy, three billion light years away. Discoveries like these not only allow astronomers to better understand the physics of black holes, but also properties of their often unassuming home galaxies. After all, mused Wheeler, “Who knew this little guy had a black hole?”

To get a simulated glimpse of Dougie for yourself, check out the amazing animation below, courtesy of team member James Guillochon:

The research is published in this month’s issue of The Astrophysical Journal. A pre-print of the paper is available here.

January 27, 2015December 23, 2015 by David Dickinson

Luna vs. the Hyades! The 1st of 13 Occultations of Aldebaran Set For January 29th

The cosmos is continually in motion.

Be it atoms, stars or snowflakes from the latest nor’easter pounding the New England seaboard, anything worth studying involves movement. And as skies and snowbound roads clear, this Wednesday and Thursday evening will give us a reason to brave the January cold, as the waxing gibbous Moon pierces the Hyades star cluster to graze past the bright star Aldebaran.

During Thursday night’s passage, the Moon will be 78% illuminated. In a sort ‘cosmos mimics controversy’ irony, the gibbous Moon is doing its best to mimic a sky bound ‘deflategate’ football just in time for Superbowl XLIX this weekend.

The motion of the Moon this week across the Hyades. Credit: Stellarium.

But the January 29^th event also marks the first occultation of Aldebaran for 2015.

Fun fact: At magnitude +0.8, Aldebaran is the only star brighter than +1^st magnitude north of the celestial equator that the Moon can currently occult. Regulus, the runner up, shines at magnitude +1.4. Two other second magnitude stars — Antares and Spica — lie along the Moon’s path on occasion, and up until the 2^nd century BC, it was possible for the Moon to occult Pollux in the constellation Gemini as well.

There are 13 occultations of Aldebaran in 2015, and the Moon occults the star 49 times overall until the last event in the current cycle on September 3^rd, 2018. Aldebaran is also occulted by the Moon more often in the current 2010-2020 decade than any other bright star. You can even spy Aldebaran near the daytime Moon with binoculars, as we did back in 1996 from North Pole, Alaska.

Maps for the 13 occultations of Aldebaran by the Moon in 2015, click to enlarge. solid lines denote regions were the occultation occurs under dark skies. Credit: Occult 4.0.

Of course, the January 29^th event is an occultation only for the high Arctic, with only a scattering of villages and distant early warning stations along the northern Nunavut coast welcoming the sequence of 2015 occultations of the bright star.

The rest of us will see a close photogenic pass, as the Moon makes an end run through the Hyades star cluster every 27.3 day sidereal lunar month in 2015. The Moon will thus occult several members of the Hyades on each pass. Our best bet for North America is the occultation of Aldebaran on November 26^th, though the Moon will be just 13 hours past Full.

68 Tauri. Credit: Occult 4.0 — The occultation of 68 Tauri (a member of the Hyades) for January 29th. Credit: Occult 4.0.

Why doesn’t the path of the Moon just stay put with respect to the sky? Because the orbit of our Moon is fixed at an inclination of 5.1 degrees not with respect to our equator, but to the plane of the ecliptic. This means that the Moon’s orbit is in motion as well, and can wander anywhere from declination 28.6 degrees north to south as it cycles from a shallow to steep path every 18.6 years. We’re actually in a shallow year in 2015 (known as a minor lunar standstill) after which the apparent path of the Moon through the sky begins to widen again until April 2025.

An occultation is celestial motion that you can see in real time as a star or planet is photobomb’d by the onrushing Moon like a January snowplow… but those background stars are in motion as well.

The Hyades themselves — along with our own solar system — are moving around the galactic center. The nearest open cluster to us at 153 light years distant, the Hyades provided a unique object of study for 19^th century astronomers. Astronomer Lewis Boss of the Dudley observatory spent several decades studying the proper motion — the apparent motion that a star seems to be moving across the sky from our solar system-bound perspective, measured in arc seconds — of the Hyades, and found the entire group was converging on a point in the constellation Orion near 6 hours 7’ right ascension and +7 degrees declination.

The imaginary convergent point of the Hyades in the night sky. Credit: Starry Night Education software.

Of course, this motion is relative and demonstrates a changing perspective, as the Hyades recedes from our solar system like a defensive line rushing to sack a quarterback.

OK, enough with the sports similes. The Hyades are so close that the actual Hyades Stream — often referred to as the Hyades Moving Group — is actually strewn across the constellations Orion, Taurus and Aries and more.

Some stars, such as 20 Arietis in the adjacent constellation Aries and Iota Horologii in the southern hemisphere may actually members as well. There’s always a bit of ongoing controversy when it comes to actual moving group membership, which is usually pegged by determining proper motion, coupled with the age and metallicity of prospective stars. Growing up in the Milky Way galaxy, our Sun was once a member of some unnamed ancient open cluster that has since long dispersed, like the Hyades are in the process of doing now.

The asterism of the Hyades and the ‘eye of the Bull.’ Photo by author.

The Hyades contains hundreds of stars and ironically, Aldebaran is not a member of the cluster, but is merely 65 light years away from us in the foreground. The V-shaped asterism of the Hyades gives the Head of Taurus the Bull its distinctive shape. The Hyades are named after the rain nymph daughters of Atlas from Greek mythology, whose half daughters the Pleiades also adorn the nearby sky.

And as an added bonus, don’t miss comet C/2014 Q2 Lovejoy crossing the constellation Triangulum, also nearby. Q2 Lovejoy reaches perihelion this week on January 30th, and although it’s completing with the evening Moon, it’s still holding out at a respectable magnitude +4.5.

All reasons to get out these chilly January evenings and ponder a hurried universe continually in motion, both fast and slow.

-Check out Q2 Lovejoy on January 30th courtesy of the Virtual Telescope project.

January 26, 2015December 23, 2015 by Morgan Rehnberg

Are Asteroids the Future of Planetary Science?

The asteroid Vesta as seen by the Dawn spacecraft. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

I don’t think I ever learned one of those little rhymes – My Very Educated Mother Just Served Us Nine Pizzas – to memorize the order of the planets, but if I had, it would’ve painted for me a minimalist picture of the solar system. (Side question: what is my Very Educated Mother serving now that we only have Dwarf Pizzas?) After all, much of the most exciting work in planetary science today happens not at the planets, but around them.

Ask an astronomer where in the solar system she’d like to visit next and you’re just as likely to hear Europa, Enceladus, Titan, or Triton as you are Venus, Mars, or Neptune. Our solar system hosts eight planets but nearly 200 known moons. And moons, it turns out, are just the start. We’ve detected more than a million asteroids; surely that’s just a fraction of what’s lurking beyond our limits of observation. Let’s not even think about the billions, perhaps even trillions, of Kuiper belt and Oort cloud objects – we could be here all day! So, while the planets may dominate the solar system gravitationally, they are pitiful numerically.

If there is one thing that the study of exoplanets has taught us in the last twenty years, it’s that the Universe thrives on chance. Given enough planets (and there appear to be gazillions out there!), practically anything can happen. Want a planet with a double sunset? We’ve got that, but perhaps you’d prefer one with three! How about a planet whose temperature is nearly half that of the surface of the Sun? No problem there. I can even offer you a planet ten times more massive than Jupiter, but nearly 20 times closer to its star than Mercury (probably not the best place for your first off-world vacation home…). The point is, with only a few thousand planets discovered, what we’ve seen already is astonishing. Imagine what those million asteroids could be hiding.

In fact, asteroids might be the next great frontier in planetary science. Let’s find out why.

An artist's impression of the rings around Chariklo. Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org) — An artist’s impression of the rings around Chariklo. Credit:
ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)

Suppose I ask you to think about the planet Saturn. What’s the first thing that jumps to mind? Probably its rings. And, if you were paying attention around the time you learned one of those nifty rhymes, you might recall that Jupiter, Uranus, and Neptune also have rings. But, did you know that at least one asteroid is also home to a ring system? Called Chariklo, it’s the largest known of a family of asteroids trapped between the orbits of the outer planets. Early last year, astronomers reported the detection of a ring system about this 250-kilometer sized object. I say a ring system because there appear to be at least two distinct rings encircling Chariklo. Discovering this new system is more than just an additional data point. Perhaps the paramount question facing the field of planetary rings today is how they formed and how long they can last; the existence of rings around a tiny asteroid tells a very different story than that implied by the giant planets.

Of course, rings haven’t been the biggest planetary science story of the last decade (much to my chagrin as a rings researcher!). That honor might instead lie with geysers. The 2005 discovery of an enormous water plume emanating from the surface of Saturn’s moon Enceladus changed the way we looked at the icy moons of the solar system. Eight years later, astronomers using Hubble claimed to have found a similar phenomenon at Jupiter’s moon Europa (now they’re not so sure). But geysers, too, might not be the sole province of planetary moons. Just last year, researchers with the Herschel Space Telescope found the first evidence for water vapor emanating from the surface of the enormous asteroid Ceres! There’s more good news: unlike Europa, with its off-in-the-future mission, the Dawn spacecraft is on its way to Ceres right now. It will arrive in just under two months and provide a close-up look at the second confirmed off-world geyser.

Speaking of moons, it probably won’t surprise you to learn that asteroids have those, too! In fact, the number of asteroids with known satellites is far too long to enumerate here. But, they are not merely numerous; the variety of asteroid moons seems to be nearly as large as the variety of asteroids themselves. Like with the planets, many asteroids dwarf their moons. Others, though, are more like binary systems in which both bodies are approximately the same size. And, although we generally know little about their shape, the variety in this realm also appears tremendous.

An artist's conception of how an unmanned spacecraft might redirect an asteroid into lunar orbit. Credit: NASA — An artist’s conception of how an unmanned spacecraft might redirect an asteroid into lunar orbit. Credit: NASA

Ultimately, though, it’s not their number or their variety that might make asteroids the future of planetary science; the laws of physics are on their side. It’s no accident that NASA intends to send astronauts to land on an asteroid long before they attempt to touch down on Mars. Neither is it a coincidence that at least three missions (Hayabusa, Hayabusa 2, and OSIRIS-REx) will have returned, or at least attempted to, samples from an asteroid to the Earth before NASA’s ambitious plan to do the same at Mars. The gravitational tug on the surface of the Red Planet is more than thirteen times more powerful than that of even the largest asteroid.

We’re seeing this accessibility in action already. Hayabusa returned a sample of asteroid Itokawa back in 2010 and its successor is already on its way. And, remember Dawn on its way to Ceres? It turns out that wasn’t its first stop. Before setting out for the solar system’s largest asteroid, the mission spent fourteen months in orbit about the asteroid Vesta. When it arrives at Ceres in March, Dawn will become the first spacecraft in history to orbit two extraterrestrial bodies.

Dawn is, I think, a signal of things to come. Asteroids, in general, and the main asteroid belt, in particular, offer the tantalizing opportunity to visit a variety of different worlds in one fell swoop. These are places that are closer to us, easier to approach, and just as scientifically interesting as the classical celestial worlds. Does this mean that the world’s science agencies will or even should abandon the study of the planets? Of course not. No asteroid looks like the cloud tops of Jupiter or the methane lakes of Titan or the intense heat of Venus. I’m not at all trying to limit the worlds which we visit. Quite the opposite, in fact: we’ve suddenly found a million new places to go!

January 26, 2015December 23, 2015 by Vanessa Janek

Astronomers Catch A Quasar Shutting Off

This artist's rending shows "before" and "after" images of a changing look quasar. Credit: Yale University.

Last week, astronomers at Yale University reported seeing something unusual: a seemingly stedfast beacon from the far reaches of the Universe went quiet. This relic light source, a quasar located in the region of our sky known as the celestial equator, unexpectedly became 6-7 times dimmer over the first decade of the 21st century. Thanks to this dramatic change in luminosity, astronomers now have an unprecedented opportunity to study both the life cycle of quasars and the galaxies that they once called home.

A quasar arises from a distant (and therefore, very old) galaxy that once contained a central, rotating supermassive black hole – what astronomers call an active galactic nucleus. This spinning beast ravenously swallowed up large amounts of ambient gas and dust, kicking up surrounding material and sending it streaming out of the galaxy at blistering speeds. Quasars shine because these ancient jets achieved tremendous energies, thereby giving rise to a torrent of light so powerful that astronomers are still able to detect it here on Earth, billions of years later.

In their hey-day, some active galactic nuclei were also energetic enough to excite electrons farther away from the central black hole. But even in the very early Universe, electrons couldn’t withstand that kind of excitement forever; the laws of physics don’t allow it. Eventually, each electron would drop back down to its rest state, releasing a photon of corresponding energy. This cycle of excitation happened over and over and over again, in regular and predictable patterns. Modern astronomers can visualize those transitions – and the energies that caused them – by examining a quasar’s optical spectrum for characteristic emission lines at certain wavelengths.

An example of an atomic spectrum, showing emission lines at particular wavelengths. — A simple example of an atomic spectrum, showing emission lines at particular wavelengths. Broad humps correspond to brighter emission lines, while lines that arise from narrow, lower-intensity emissions appear dimmer. Credit: NASA

Not all quasars are created equal, however. While the spectra of some quasars reveal many bright, broad emission lines at different energies, other quasars’ spectra consist of only the dim, narrow variety. Until now, some astronomers thought that these variations in emission lines among quasars were simply due to differences in their orientation as seen from Earth; that is, the more face-on a quasar was relative to us, the broader the emission lines astronomers would be able to see.

But all of that has now been thrown into question, thanks to our friend J015957.64+003310.5, the quasar revealed by the team of astronomers at Yale. Indeed, it is now plausible that a quasar’s pattern of emission lines simply changes over its lifetime. After gathering ten years of spectral observations from the quasar, the researchers observed its original change in brightness in 2010. In July 2014, they confirmed that it was still just as dim, disproving hypotheses that suggested the effect was simply due to intervening gas or dust. “We’ve looked at hundreds of thousands of quasars at this point, and now we’ve found one that has switched off,” explained C. Megan Urry, the study’s co-author.

How would that happen, you ask? After observing the comparable dearth of broad emission lines in its spectrum, Urry and her colleagues believe that long ago, the black hole at the heart of the quasar simply went on a diet. After all, an active galactic nucleus that consumed less material would generate less energy, giving rise to fainter particle jets and fewer excited atoms. “The power source just went dim,” said Stephanie LaMassa, the study’s principal investigator.

LaMassa continued, “Because the life cycle of a quasar is one of the big unknowns, catching one as it changes, within a human lifetime, is amazing.” And since the life cycle of quasars is dependent on the life cycle of supermassive black holes, this discovery may help astronomers to explain how those that lie at the center of most galaxies evolve over time – including Sagittarius A*, the supermassive black hole at the center of our own Milky Way.

“Even though astronomers have been studying quasars for more than 50 years, it’s exciting that someone like me, who has studied black holes for almost a decade, can find something completely new,” added LaMassa.

The team’s research will be published in an upcoming issue of The Astrophysical Journal. A pre-print of the paper is available here.

January 26, 2015December 23, 2015 by Elizabeth Howell

What Are The Benefits Of Space Exploration?

Eugene Cernan on the lunar surface, December 13, 1972. Credit: NASA.

Why explore space? It’s an expensive arena to play in, between the fuel costs and the technological challenge of operating in a hostile environment. For humans, a small mistake can quickly become fatal — something that we have seen several times in space history. And for NASA’s budget, there are projects that come in late and over budget, drawing the ire of Congress and the public.

These are some of the drawbacks. But for the rest of this article, we will focus on some of the benefits of going where few humans have gone before.

Spinoffs

Perhaps the most direct benefit comes from technologies used on Earth that were first pioneered in space exploration. This is something that all agencies talk about, but we’ll focus on the NASA Spinoff program as an example. (NASA will be used as the prime example for most of this article, but many of these cited benefits are also quoted by other space agencies.)

The program arose from NASA’s desire to showcase spinoffs at congressional budget hearings, according to its website. This began with a “Technology Utilization Program Report” in 1973, which began as a black-and-white circular and progressed to color in 1976 following public interest. Since that year, NASA has published more than 1,800 reports on spinoffs.

The agency has several goals in doing this. “Dispelling the myth of wasted taxpayer dollars” is one NASA cites, along with encouraging the public to follow space exploration and showing how American ingenuity can work in space.

There are many commercialized advances the program says it contributed to, including “memory foam” (first used for airline crash protection), magnetic resonance imaging and smoke detection. In many cases, NASA did not invent the technology itself, but just pushed it along, the agency says.

An MRI image of the lower back. Credit: NASA

But as counterpoint to NASA’s arguments, some critics argue the technology would have been developed anyway without space exploration, or that the money spent on exploration itself does not justify the spinoff.

Job creation

Another popularly cited benefit of space exploration is “job creation”, or the fact that a space agency and its network of contractors, universities and other entities help people stay employed. From time to time, NASA puts out figures concerning how many associated jobs a particular project generates, or the economic impact.

Here’s an example: in 2012, NASA administrator Charles Bolden published a blog post about the Curiosity Mars rover landing, which was picked up by the White House website. “It’s also important to remember that the $2.5 billion investment made in this project was not spent on Mars, but right here on Earth, supporting more than 7,000 jobs in at least 31 states,” he wrote.

Hazcam fisheye camera image shows Curiosity drilling into “Windjana” rock target on April 29, 2014 (Sol 615). Flattened and colorized image shows Mount Remarkable butte backdrop. Credit: NASA/JPL/Marco Di Lorenzo/Ken Kremer - kenkremer.com — Hazcam fisheye camera image shows Curiosity drilling into “Windjana” rock target on April 29, 2014 (Sol 615). Flattened and colorized image shows Mount Remarkable butte backdrop. Credit: NASA/JPL/Marco Di Lorenzo/Ken Kremer – kenkremer.com

But the benefit can cut in a negative way, too. NASA’s budget is allocated by Congress, which means that the amount of money it has available for employment fluctuates. There are also some programs that are highly dependent on grants, which can make stable jobs challenging in those fields. Finally, as the priorities of Congress/NASA change, jobs can evaporate with it. One example was the space shuttle’s retirement, which prompted a job loss so massive that NASA had a “transition strategy” for its employees and contractors.

It’s also unclear what constitutes a “job” under NASA parlance. Some universities have researchers working on multiple projects — NASA-related or not. Employment can also be full-time, part-time or occasional. So while “job creation” is cited as a benefit, more details about those jobs are needed to make an informed decision about how much good it does.

Education

Teaching has a high priority for NASA, so much so that it has flown astronaut educators in space. (The first one, Christa McAuliffe, died aboard the space shuttle Challenger during launch in 1986. Her backup, Barbara Morgan, was selected as an educator/mission specialist in 1998 and flew aboard STS-118 in 2007.) And to this day, astronauts regularly do in-flight conferences with students from space, ostensibly to inspire them to pursue careers in the field.

Christa McAuliffe and Barbara Morgan practice teaching from space. Credit: "The Lost Lessons" — Christa McAuliffe and Barbara Morgan practice teaching from space. Credit: “The Lost Lessons”

NASA’s education office has three goals: making the workforce stronger, encouraging students to pursue STEM careers (science, technology, engineering and mathematics), and “engaging Americans in NASA’s mission.” Other space agencies also have education components to assist with requirements in their own countries. It’s also fair to say the public affairs office for NASA and other agencies play roles in education, although they also talk about topics such as missions in progress.

But it’s hard to figure out how well the education efforts translate into inspiring students, according to a National Research Council report on NASA’s primary and secondary education program in 2008. Among other criticisms, the program was cited as unstable (as it needs to change with political priorities) and there was little “rigorous evaluation” of its effectiveness. But NASA’s emphasis on science and discovery was also praised.

Anecdotally, however, many astronauts and people within NASA have spoken about being inspired by watching missions such as Apollo take place. And the same is true of people who are peripherally involved in the field, too. (A personal example: this author first became interested in space in the mid-1990s through the movie Apollo 13, which led to her watching the space shuttle program more closely.)

New Rosetta mission findings do not exclude comets as a source of water in and on the Earth's crust but does indicate comets were a minor contribution. A four-image mosaic comprises images taken by Rosetta’s navigation camera on 7 December from a distance of 19.7 km from the centre of Comet 67P/Churyumov-Gerasimenko. (Credit: ESA/Rosetta/Navcam Imager) — New Rosetta mission findings do not exclude comets as a source of water in and on the Earth’s crust but does indicate comets were a minor contribution. A four-image mosaic comprises images taken by Rosetta’s navigation camera on 7 December from a distance of 19.7 km from the centre of Comet 67P/Churyumov-Gerasimenko. (Credit: ESA/Rosetta/Navcam Imager)

Intangible benefits

Added to this host of business-like benefits, of course, are the intangibles. What sort of value can you place on better understanding the universe? Think of finding methane on Mars, or discovering an exoplanet, or constructing the International Space Station to do long-term exploration studies. Each has a cost associated with it, but with each also comes a smidgeon of knowledge we can add to the encyclopedia of the human race.

Space can also inspire art, which is something seen heavily in 2014 following the arrival of the European Space Agency Rosetta mission at Comet 67P/Churyumov–Gerasimenko. It inspired songs, short videos and many other works of art. NASA’s missions, particularly those early space explorers of the 1950s and 1960s, inspired creations from people as famous as Norman Rockwell.

There also are benefits that maybe we cannot anticipate ahead of time. The Search for Extraterrestrial Intelligence (SETI) is a network that advocates looking for life around the universe, likely because communicating with beings outside of Earth could bring us some benefit. And perhaps there is another space-related discovery just around the corner that will change our lives drastically.

For more information, here is a Universe Today article about how we really watched television from the moon. We also collected some spin-offs from the Hubble Space Telescope. You can also listen to Astronomy Cast. Episode 144 Space Elevators.

January 24, 2015December 23, 2015 by Bob King

Latest Research Reveals a Bizarre and Vibrant Rosetta’s Comet

Dust-covered, boulder-strewn landscape on the smaller of the two lobes of Comet 67P/Churyumov-Gerasimenko taken from a distance of 5 miles (8 km). Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

We’ve subsisted for months on morsels of information coming from ESA’s mission to Comet 67P/Churyumov-Gerasimenko. Now, a series of scientific papers in journal Science offers a much more complete, if preliminary, look at Rosetta’s comet. And what a wonderful and complex world it is.

Scientists have defined 19 regions on Comet 67P/Churyumov-Gerasimenko's nucleus grouped according to terrain. Each is named for an ancient Egytptian deity. Credits: ESA/Rosetta/MPS/OSIRIS Team/UPD/LAM/IAA/SSO /INTA/UPM/DASP/IDA — Scientists have defined 19 regions on Comet 67P/Churyumov-Gerasimenko’s nucleus according to terrain and named for Egyptian deities like Imhotep, Aten and Hathor. Credits: ESA/Rosetta/MPS/OSIRIS Team/UPD/LAM/IAA/SSO /INTA/UPM/DASP/IDA

Each of the papers describes a different aspect of the comet from the size and density of dust particles jetting from the nucleus, organic materials found on its surface and the diverse geology of its bizarre landscapes. Surprises include finding no firm evidence yet of ice on the comet’s nucleus. There’s no question water and other ices compose much of 67P’s 10 billion ton mass, but much of it’s buried under a thick layer of dust.

Despite its solid appearance, 67P is highly porous with a density similar to wood or cork and orbited by a cloud of approximately 100,000 “grains” of material larger than 2 inches (5 cm) across stranded there after the comet’s previous perihelion passage. Thousands of tiny comet-lets!
Continue reading “Latest Research Reveals a Bizarre and Vibrant Rosetta’s Comet”

January 24, 2015December 23, 2015 by Tim Reyes

There’s a Crack Forming on Rosetta’s 67P. Is it Breaking Up?

A Fissure spanning over 100 meters across the neck of Rosetta's comet 67P raises the question of if or when will the comet breakup. The fissure is part of released studies by Rosetta scientists in the Journal Science (Image Credits: ESA/Rosetta, Illustration, T.Reyes)

Not all comets break up as they vent and age, but for Rosetta’s comet 67P, the Rubber Duckie comet, a crack in the neck raises concerns. Some comets may just fizzle and uniformly expel their volatiles throughout their surfaces. They may become like puffballs, shrink some but remain intact.

Comet 67P is the other extreme. The expulsion of volatile material has led to a shape and a point of no return; it is destined to break in two. Songwriter Neil Sedaka exclaimed, “Breaking Up is Hard to Do,” but for comets this may be the norm. The fissure is part of the analysis in a new set of science papers published this week.

Top left: The Hathor cliff face is to the right in this view. The aligned linear structures can be clearly seen. The smooth Hapi region is seen at the base of the Hathor cliff. Boulders are prevalent along the long axis of the Hapi region. Bottom left and right: Crack in the Hapi region. The left panel shows the crack (indicated by red arrows) extending across Hapi and beyond. The right panel shows the crack where it has left Hapi and is extending into Anuket, with Seth at the uppermost left and Hapi in the lower left. (Credit: ESA/Rosetta)

The images show a fissure spanning a few hundred meters across the neck of the two lobe comet. The fissure is just one of the many incredible features on Comet 67P and is reported in research articles released in the January 22, 2015, edition of the journal Science.

What it means is not certain, but Rosetta team scientists have stated that flexing of the comet might be causing the fissure. As the comet approaches the Sun, the solar radiation is raising the temperature of the surface material. Like all materials, the comet’s will expand and contract with temperature. And diurnal (daily) changes in the tidal forces from the Sun is a factor, too.

An image sequence from the Navcam of the Rosetta spacecraft (right) is shown beside a simulation. Further work on the interaction of comets with solar radiation will include computer models that utilize Rosetta data to reveal how comet nuclei evolve over time – over many orbits of the Sun- and break up. Peanut, rubber-duck, potatoes or just round-shaped comet nuclei likely result from combinations of rotation, changes in rotation, spin rate, composition and internal structure, as a nucleus interacts with the Sun over many orbits. (Credits: ESA/Rosetta, Illustration – J.Schmidt)

The crack, or fissure, could spell the beginning of the end for comet 67P/Churyumov–Gerasimenko. It is located in the neck area, in the region named Hapi, between the two lobes that make 67P appear so much like a Rubber Duck from a distance. The fissure could represent a focal point of many properties and forces at work, such as the rotation rate and axis – basically head over heels of the comet. The fissure lies in the most active area at present, and possibly the most active area overall. Though the Hapi region appears to receive nearly constant sunlight, at this time, Rosetta measurements (below) show otherwise – receiving 15% less sunlight than elsewhere.

Left: A map looking at the northern (right-hand rule, positive) pole of 67P showing the total energy received from the Sun per rotation on 6 August 2014. The base of the neck (Hapi) receives ~15% less energy than the most illuminated region, 3.5 × 106 J m-2 (per rotation). If self-heating were not included, the base of the neck would receive ~30% less total energy. Right: Similar to the left panel but showing total energy received over an entire orbital period in J m-2 (per orbit). (Credit:ESA/Journal Science Article, Figure 5) — Left: A map looking at the northern (right-hand rule, positive,) pole of 67P showing the total energy received from the Sun per rotation on 6 August 2014. The base of the neck (Hapi) receives ~15% less energy than the most illuminated region, 3.5 × 106 J m-2 (per rotation). If self-heating were not included, the base of the neck would receive ~30% less total energy. Right: Similar to the left panel but showing total energy received over an entire orbital period in J m-2 (per orbit). (Credit:ESA/Journal Science Article, Figure 5)

Sunlight and heating are major factors and the neck likely experiences the greatest mechanical stresses – internal torques – from heating or tidal forces from the sun as it rotates and approaches perihelion. Rosetta scientists are still not certain whether 67P is two bodies in contact – a contact binary – or a shape that formed from material expelled about the neck area leading to its narrowing.

Fragmentation of comets is common. Many sungrazers are broken up by thermal and tidal stresses during their perihelions. At top, an image of the comet Shoemaker-Levy 9 (May 1994) after a close approach with Jupiter which tore the comet into numerous fragments. An image taken by Andrew Catsaitis of components B and C of Comet 73P/Schwassmann–Wachmann 3 as seen together on 31 May 2006 (Credit: NASA/HST, Wikipedia, A.Catsaitis) — Fragmentation of comets is common. Many sungrazers are broken up by thermal and tidal stresses during their perihelions. At top, an image of the comet Shoemaker-Levy 9 (May 1994) after a close approach with Jupiter which tore the comet into numerous fragments. An image taken by Andrew Catsaitis of components B and C of Comet 73P/Schwassmann–Wachmann 3 as seen together on 31 May 2006 (Credit: NASA/HST, Wikipedia, A. Catsaitis)

The Philae lander’s MUPUS thermal sensor measured a temperature of –153°C (–243°F) at the landing site, while VIRTIS, an instrument on the primary spacecraft Rosetta, has measured -70°C (-94°F) at present. These temperatures will rise as perihelion is reached on August 13, 2015, at a distance of 1.2432 A.U. (24% further from the Sun than Earth). At present – January 23rd – 67P is 2.486 A.U. from the Sun (2 1/2 times farther from the Sun than Earth). While not a close approach to the Sun for a comet, the Solar radiation intensity will increase by 4 times between the present (January 2014) and perihelion in August.

Hubble capture a sequence of images of the comet 73P/Schwassman-Wachmann 3. The comet fragmented and like 73P, Rosetta's 67P will likely breakup some day in two majore fragments with debris spreading out as in these images. The Solar wind pressure as well as any explosive force from the breakup causes the comet fragments to slowly disperse but altogether remain effectively in the same orbit. (Image Credit: NASA/Hubble) — Hubble captured a sequence of images of the comet 73P/Schwassman-Wachmann 3. The comet fragmented, and like 73P, Rosetta’s 67P will likely break some day into two major fragments with debris spreading out as in these images. The Solar wind pressure, as well as any explosive force from the break up, will cause the comet fragments to slowly disperse but effectively remain in the same orbit. (Image Credit: NASA/Hubble)

Stresses due to temperature changes from diurnal variations, the changing Sun angle during perihelion approach, from loss of material, and finally from changes in the tidal forces on a daily basis (12.4043 hours) may lead to changes in the fissure causing it to possibly widen or increase in length. Rosetta will continue escorting the comet and delivering images of the whole surface that will give Rosetta scientists the observations and measurements to determine 67P/Churyumov–Gerasimenko’s condition now and its fate in the longer term.

The fissure is not a very recent event. Universe Today's Bob King published an earlier image in his blog in September and added a question to illustrate. Whether the crack has widen since this time is not certain. (Image Credit: ESA, Illustration, Bob King) — The fissure is not a very recent event. Universe Today’s Bob King published an earlier image in his blog in September and added a question to illustrate. Whether the crack has widened since that time is not certain. (Image Credit: ESA, Illustration, Bob King)

Stay tuned for a forthcoming article from UT’s writer Bob King about numerous Rosetta mission scientific findings published this week in the journal Science.

Reference:

The morphological diversity of comet 67P/Churyumov-Gerasimenko

On the nucleus structure and activity of comet 67P/Churyumov-Gerasimenko

January 23, 2015December 23, 2015 by Elizabeth Howell

What Is The Difference Between the Geocentric and Heliocentric Models of the Solar System?

What does our Solar System really look like? If we were to somehow fly ourselves above the plane where the Sun and the planets are, what would we see in the center of the Solar System? The answer took a while for astronomers to figure out, leading to a debate between what is known as the geocentric (Earth-centered) model and the heliocentric (Sun-centered model).

The ancients understood that there were certain bright points that would appear to move among the background stars. While who exactly discovered the “naked-eye” planets (the planets you can see without a telescope) is lost in antiquity, we do know that cultures all over the world spotted them.

The ancient Greeks, for example, considered the planets to include Mercury, Venus, Mars, Jupiter and Saturn — as well as the Moon and the Sun. The Earth was in the center of it all (geocentric), with these planets revolving around it. So important did this become in culture that the days of the week were named after the gods, represented by these seven moving points of light.

All the same, not every Greek believed that the Earth was in the middle. Aristarchus of Samos, according to NASA, was the first known person to say that the Sun was in the center of the universe. He proposed this in the third century BCE. The idea never really caught on, and lay dormant (as far as we can tell) for several centuries.

Earth is at the center of this model of the universe created by Bartolomeu Velho, a Portuguese cartographer, in 1568. Credit: NASA/Bibliothèque Nationale, Paris

Because European scholars relied on Greek sources for their education, for centuries most people followed the teachings of Aristotle and Ptolemy, according to the Galileo Project at Rice University. But there were some things that didn’t make sense. For example, Mars occasionally appeared to move backward with respect to the stars before moving forward again. Ptolemy and others explained this using a system called epicycles, which had the planets moving in little circles within their greater orbits.

But by the fifteen and sixteenth centuries, astronomers in Europe were facing other problems, the project added. Eclipse tables were becoming inaccurate, sailors needed to keep track of their position when sailing out of sight of land (which led to a new method to measure longitude, based partly on accurate timepieces), and the calendar dating from the time of Julius Caesar (44 BCE) no longer was accurate in describing the equinox — a problem for officials concerned with the timing of religious holidays, primarily Easter. (The timing problem was later solved by resetting the calendar and instituting more scientifically rigorous leap years.)

While two 15th-century astronomers (Georg Peurbach and Johannes Regiomontanus) had already consulted the Greek texts for scientific errors, the project continued, it was Nicolaus Copernicus who took that understanding and applied it to astronomy. His observations would revolutionize our thinking of the world.

Retrograde motion of Mars. Image credit: NASA

Published in 1543, Copernicus’ De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Bodies) outlined the heliocentric universe similar to what we know today. Among his ideas, according to Encyclopedia Britannica, was that the planets’ orbits should be plotted with respect to the “fixed point” Sun, that the Earth itself is a planet that turns on an axis, and that when the axis changes directions with respect to the stars, this causes the North Pole star to change over time (which is now known as the precession of the equinoxes.)

Putting the Sun at the center of our Solar System, other astronomers began to realize, simplified the orbits for the planets. And it helped explain what was so weird about Mars. The reason it backs up in the sky is the Earth has a smaller orbit than Mars. When Earth passes by Mars in its orbit, the planet appears to go backwards. Then when Earth finishes the pass, Mars appears to move forwards again.

Other supports for heliocentrism began to emerge as well. Johannes Kepler’s rules of motions of the planets (based on work from him and Tycho Brahe) are based on the heliocentric model. And in Isaac Newton’s Principia, the scientist described how the motions happen: a force called gravity, which appears to be “inversely proportional to the square of the distance between objects”, according to the University of Wisconsin-Madison.

Artist's conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech — Artist’s conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech

Newton’s gravity theory was later supplanted by that of Albert Einstein, who in the early 20th century proposed that gravity is instead a warping of space-time by massive objects. That said, heliocentric calculations guide spacecraft in their orbits today and the model is the best way to describe how the Sun, planets and other objects move.

Universe Today has articles on both the heliocentric model and the geocentric model, and Astronomy Cast has an episode on the center of the universe.