“Exoplanet”, the latest wallpaper to be added to the gallery on the website depicts a binary planetary system around a distant star hosting a living ecosystem. This image has taken forever to produce thanks to some quirks with the Vue-Esprit software that was used to create it. Hope you enjoy it!
Exoplanet
Check out the other Orbital Maneuvers’ wallpapers in the gallery.
Till next time,
RC Davison
The cosmos holds many wondrous things to capture our attention, but to me, the site of a globular cluster is just mesmerizing. These bejeweled orbs can contain tens of thousands to millions of stars in a sphere that can be about 100 light-years (ly) across. (Compare this with our Milky Way spiral galaxy that is approximately 100,000 ly across and contains on the order of 300 billion stars.) There are close to 150 globular clusters orbiting our galaxy, which is not unique; other galaxies have thousands or more in orbit about them.
The globular cluster Omega Centauri, visible from the Southern Hemisphere
Image credit: Joaquin Polleri & Ezequiel Etcheverry (Observatorio Panameño en San Pedro de Atacama)
Globular clusters are made up of very old stars, on the order of 10-13 billion years old. Note that the current estimate for the age of the Universe is about 13.8 billion years old, so these stars are ancient, especially when you compare them to our Sun, which is around 4.5 billion years old. The stars that comprise a cluster are typically smaller, cooler dwarf stars designated as M-class that burn their fuel very slowly giving them their longer lifetime. The larger, hotter stars burned themselves out long ago in brilliant supernovae, peppering the cluster with heavier elements necessary for rocky planet formation. Because these stars are so old, planets that may form in their habitable zones have a greater chance of developing life. But, being in a globular cluster brings its own hazards, which would be a detriment to the evolution of advanced life. Check out the article by astronomers William Harris and Jeremy Webb, “Life Inside a Globular Cluster“, which discusses some of the potential hazards of living in a globular cluster. (The link will download a pdf of the article.)
The very nature of the cluster, with its large number of stars so close together presents the opportunity for neighboring stars to disrupt the formation of planets or even steal planets from each other. Planets may also be ejected from a stable system by the gravitational influence of a passing star and follow their own path through the cluster. This is not to say that there would not be planets in stable orbits around stars in the cluster, although to date, no planets have been located in a globular cluster. The cluster itself makes it very difficult for us to detect planets orbiting its stars. Take a look at a previous post “Stars in Motion” which has a video showing the somewhat chaotic motion of stars in a globular cluster. It’s not the well ordered system one might intuitively expect from a gigantic ball of stars.
To get a perspective on how dense a cluster is, consider that our nearest star, Proxima Centauri, which is 4.2 ly from us. If you were to map out a sphere at the center of a globular cluster with a radius of 4.2 ly it would contain on the order of 10,000 stars instead of two! These stars would be less than a light-year apart.
A paper was recently published, “Globular Clusters as Cradles of Live and Advanced Civilizations” by Dr. R. DiStefano et al, which discusses the possibilities of planets forming around stars in a globular cluster and surviving long enough for life to form and flourish. But, this is conditional on the planets forming around stars that are located in a “sweet spot” in the cluster; that is, far enough apart that they don’t interfere with each other. Planets that form in the habitable zones of these cooler stars would be less prone to having their orbits disrupted by a passing star because these zones are close to these less massive, cooler stars.
Ringed gas giant with habitable moon on the periphery of a globular cluster. (Click for a larger image.)
A benefit of the stars being in such close proximity is that it makes the possibility of traveling to or communicating with another civilization so much more practical and if advanced life formed, probable. Also, the high concentration of stars means that planets that have been ejected and not captured by another star may still receive enough light continue to nurture life, especially if the planets retain or generate enough heat to keep water liquid, even if under a layer of ice.
All of this makes me wonder what it would be like to view the cosmos from inside a cluster or just outside of a cluster. The image below represents a possible view of a planet inside the cluster, some distance from the center. The ambient light from all the stars would make nighttime about as bright as dusk/dawn on our planet. Consequently, the beings populating this planet might have a great understanding of the stars around them, but their view of the universe outside of the cluster would be greatly hampered by this collection of stars.
View from inside a globular cluster. (Click for a larger image.)
Check out the very interesting short story by Issac Asimov, “Nightfall”, which is about a civilization that evolved in a globular cluster on a planet with the six suns. They experience constant daylight except once every two thousand and forty-nine years when five of the stars align on one side of the planet and the sixth is eclipsed by a moon unveiling nighttime and all the wonders of the night sky, which they are very unprepared for.
Whether globular clusters are abodes for life or not will not be answered soon. It’s just one more challenge for astronomers to unravel as they sharpen their skills in exploring our amazing cosmos.
Till next time,
RC Davison
A new wallpaper is up called “Troubled Waters” is available on the wallpaper page. The planet Earth will outlast us all, it is we that swim in troubled waters. The only place in the cosmos that we know is hospitable to human life; we should be more careful in how we treat it and its inhabitants.
Troubled Waters
Till next time,
RC Davison
Check out the latest wallpaper, Water Hole, now up on the website.
Water Hole
Stop by the gallery and browse the other wallpapers that are available.
Till next time,
RC Davison
Comet Catalina by Greg Hogan
Sometimes a picture captures just the right moment in space and time and shows us more than the obvious when we take a closer look. The great picture above, taken by Greg Hogan shows the comet Catalina visiting the morning sky with the crescent Moon and blazingly bright planet Venus. Focusing in on the wispy comet just left of center at the bottom of the image, one will notice that it looks more like a clock captured at five minutes before four. This image shows very nicely the two distinct tails that a comet can form as it dives into the inner solar system to swing around the Sun and back out again. The two tails accompanying a comet are distinctly different: one being a dust tail and the other an ion tail.
The coma or cloud around the head or nucleus of a comet, along with its tails start to form out around the orbit of Mars as the comet warms with the increasing amount of energy it’s receiving from the Sun. The comet is composed of ice (frozen gases, and water), dust, dirt and rock and is sometimes referred to as a “dirty snowball”. As it moves closer to the Sun it continues to heat up, and the ices begin to sublime or convert directly to a gas without going through a liquid phase. This release of gas carries dust particles with it, which destabilizes the comet’s surface allowing larger particles to be released, all of which contributes to the coma and tails. Intense jets of gas, can push even more material away from the comet. It is this debris trail that becomes the source for an annual meteor shower if and when the Earth crosses the path of the comet, such as the Perseids we see in the middle of August every year, which is from Comet Swift-Tuttle.
The dust tail reflects the sunlight and appears white in color similar to the coma. The dust is launched from the comet’s surface and slowly moves away from its host. These particles will begin orbiting the Sun on their own trajectory as they escape the gravitational influence of the comet. They are also pushed away from the comet by the radiation pressure from the Sun. This radiation pressure is due to the transfer of momentum from a light particle (photon) to the dust particle when they collide. This is exactly how a solar sail works. The dust tail will flow behind the comet and as the comet rounds the Sun the tail can become curved as the particles of dust are pushed by the light, as can be seen in the image below of comet McNaught.
Comet McNaught’s dust tail – Image by Robert H. McNaught
The gas particles that are released by the comet will form the ion tail It is typically bluish/greenish in color and occurs because these gas particles liberated from the comet become “ionized” or charged by the high energy ultraviolet light emitted by the Sun. Once the atoms and molecules of gas become charged they will now be influenced by the magnetic field associated with the solar wind that comes from the Sun. The solar wind is a collection of high energy particles that the Sun radiates and entrained with this stream of particles is a magnetic field pointing away from the Sun. So the ion tail will point directly away from the Sun while the dust tail indicates the path the comet has taken. The ion tail can exhibit knots and twists due to the magnetic field as can be seen below.
Comet Catalina’s twisted ion tail. Image courtesy of CometwatchUK
The amazing image below shows comet Encke being buffeted by a coronal mass ejection (CME) from the Sun. The comet’s tail detaches as the mass of solar particles sweeps by and then quickly reforms. This is believed to be caused by the magnetic field retained in the CME interacting with the ion tail’s field. The video is from NASA’s STEREO solar mission.
Comet Encke’s interaction with a CME
If you look in Greg’s picture at the Moon you will see that it is illuminated on lower right hand side by the Sun, which is out of frame in the lower right. Now look closely at comet Catalina and at the “minute hand” of the clock – the ion tail; it’s pointing directly away from the Sun, while the “hour hand” – the dust tail is pointing more towards the Sun indicating that the comet is moving away from the Sun and heading back out of the solar system. Catalina passed closest to the Sun on November 15, 2015 and will be closest to Earth on January 12, 2016.
Comet Catalina will make only a one-time appearance, as it has gained enough energy on its dive through the inner solar system that it will be jettisoned into interstellar space, never to return. On its journey it will pass through two large reservoirs of comets and other leftover debris from the early solar system that orbit our star, the Kuiper Belt and the Oort Cloud.
Comets originating in the Kuiper Belt, about 30 – 55 times the distance the Earth is from the Sun are known as short period comets, and have periods less than 200 years. Halley’s comet is a well known short period comet, having a period of about 76 years. Note that the Kuiper belt starts at the orbit of the planet Neptune. (Yes, Pluto is a Kuiper Belt object!) (The average Earth-Sun distance is 93 million miles or 150 million km and has been established as a standard unit of distance in astronomy known as an Astronomical Unit or “AU”.)
Long period comets originate from a much more distant region of the solar system, the Oort Cloud. This cloud of frozen debris extends from 5,000 AU to 100,000 AU. Way out there! These comets can have periods as long as 30 million years to complete an orbit around the Sun. Comet Catalina most likely originated from here.
Catch a glimpse of comet Catalina if you can in January, as it will be on the edge of naked-eye visibility, so under the right conditions you won’t need binoculars or a telescope, but they will make for much better viewing. Comets are relics of the early solar system and the more we can study them, the more we learn about how our place in space has formed.
Jets on comet 67P from OSIRIS Imager on Rosetta – Image courtesy of the European Space Agency
Check out the European Space Agency’s site for amazing pictures and details on comet 67P (Churyumov-Gerasimenko) that their probe Rosetta has been flying in formation with for the last year.
Till next time,
RC Davison
References:
http://www.nasa.gov/sites/default/files/145944main_Kuiper.Belt.Lithograph.pdf
https://ase.tufts.edu/cosmos/view_chapter.asp?id=12&page=5
http://astronomy.swin.edu.au/cosmos/C/cometary+dust+tail
http://secchi.nrl.navy.mil/Publications/Vourlidas_encke_07.pdf
Most wallpapers evolve from an idea, or something I’ve seen during my daily journey through life. Starry Night actually started out as a desert scene and ended up with water and a whole lot of suns in the sky.
Starry Night
The vast majority of stars in the Universe are made up of red dwarf stars or class M stars. They are smaller and cooler than our Sun and because of the fact that they are dimmer and cooler, they consume their hydrogen fuel at a much lower rate. This means that these stars are very long lived – on the order of 10 trillion years, as compared to our Sun, which will be around for about 10 billion years.
Red dwarfs typically exist as solitary stars, but stars that are brighter than the red dwarfs tend to be found more commonly in binary configurations. A binary star system has two stars that orbit around a common center of mass. Stars can also exist in three, four or more configurations, but as you add more stars to the mix, the more unstable the system becomes. Planets can form in such multi-stellar systems and several have been uncovered by the Kepler mission.
Starry Night is a multi-stellar system. The most interesting thing that occurred to me was that the inhabitants on a planet in such a system may never have a night sky with which to peer into the depths of the Universe! Imagine how much they would never know about the Universe. And, even more interesting is to consider their response when they manage to rise above their atmosphere and glimpse the cosmos for the first time.
Enjoy Starry Night and visit the ORBITAL MANEUVERS web site for additional wallpapers and more.
Till next time,
RC Davison
A sunset Inspired by a vacation in the Thousand Islands while staying on Wellesly Island, which overlooks the Lake of the Isles. A beautiful area to appreciate some of the wonders this planet has to offer.
Sunset at Wellesly Island
Enjoy!
(Check out the other available wallpapers.)
Till next time,
RC Davison
What’s out there?
Probably not bipedal, humanoid life with wrinkled foreheads, spotted faces and knobby noses so frequently depicted in modern sci-fi today. What may be out there is probably more bizarre than we can imagine. Take a look at what swims in our seas! (And, this is just what we know about.) Just think about the fact that we — those creatures in the sea and us humans — all evolved on the same planet. What is life going to be like that evolved on a different planet with different environmental stresses from what our evolutionary history has been? It probably tops anything we can imagine!
Below are two versions of the same scene depicting life on a watery planet, which exists near a sparkling globular cluster and nebula giving birth new stars. My alien lifeforms are pretty tame, but the focus of the image was the environment and not the lifeforms. The two versions are basically the same scene but with very different atmospheres and consequentially very different lighting effects. I put both up for your viewing pleasure because I couldn’t make up my mind which version I liked better! Let me know which one you prefer.
“Life – Not as We Know It” in blue.
“Life – Not as We Know It” in red
Check out more wallpapers at the Orbital Maneuvers website.
Till next time,
RC Davison
ORBITAL MANEUVERS has been updated with a bold new cover illustration and revised information in the Author’s Notes section on the latest efforts to identify and defend against Near-Earth Asteroid threats.
Please note that the story has not changed, just the Author’s Notes section at the end of the book. This section includes links to the latest efforts to identify Near-Earth Objects (NEOs) and our efforts to defend against a pending impact. If interested, you can read this updated section of the book as it exists on the website on the Asteroids page.
The website also has an updated front page reflecting the new book cover and I’m intending on revising the site to be more compatible with the current mobile technology as time permits.
Stay tuned for more to come! Thanks for the support!
Till next time,
RC Davison
Leonard Nimoy (1931 – 2015)
A human being portraying a fictional character that touched, if not inspired, millions for almost 50 years, Leonard Nimoy and Spock will be indelibly etched into history as one entity. A human actor who secured a role in 1966 as an alien aboard a starship with over 400 humans, Nimoy would eventually meld with this alien character to create the Vulcan, Spock we all know.
Leonard Nimoy spent years trying to distance himself from the Vulcan after the original series ended, but he eventually learned that Spock was as much a part of himself as he was of the character. And, Spock, the half-human, half-Vulcan Science Officer on board the USS Enterprise was in constant turmoil with the emotions he felt and had to repress to be a Vulcan. Nimoy crafted a wonderful character whose internal conflicts could be intimately felt and shared by many of us across our planet Earth.
Leonard Nimoy, a man of many talents: actor, director, producer, photographer, narrator, poet, musician, creator of Spock, will be missed. For whatever the Cosmos holds for you, live long and prosper and thank you for your inspiration.
Till next time,
RC Davison
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