Comet ISON is making its way through the inner solar system. Visualize its unusual orbit and track its journey
around the sun with this paper model. The background image shows comet C/2001 Q4 (NEAT). Credit: NASA and T. A. Rector (Univ. of Alaska Anchorage), Z. Levay and L. Frattare (STScI) and WIYN/NOAO/AURA/NSF
Planet orbits are so easy to picture – eight nearly concentric hula hoops centered on the sun. Comets are weirder. Their orbits vary from tapered ellipses shaped like cigars to completely open-ended parabolas and even hyperbolas. Comet ISON’s highly-elongated (stretched out) orbit is best described as hyperbolic, although that’s subject to change if Jupiter gets into the act and gives the comet a gravitational nudge during its outbound journey. As the largest planet, it has a special knack for this kind of trick, having tamed many a wayward comet’s orbit into a neat ellipse.
Comets can travel in a variety of orbits from elliptical to open-ended parabolic and hyperbolic. Credit: Wikipedia
Comets in hyperbolic and parabolic orbits are typically making their first trip to the sun from the bitterly cold and distant Oort Cloud, a roughly spherical volume of space beginning about 3,000 times Earth’s distance from the sun and extending outward to 50,000 times that distance or nearly one-quarter of the way to Alpha Centauri. The Cloud is believed to hold trillions of icy comets. Think of it as the sun’s ultimate beer cave.
To help visualize Comet ISON’s travels across the solar system we can always go the Internet and search for images and video, but sometimes it’s fun to use your own hands. Building a model using a simple cardboard template can make the knowledge “stick”. Not to mention it’s an excellent classroom activity for teachers preparing students for the comet’s post-perihelion display. All you need is this color pdf file, a printer and a few minutes to assemble.
The familiar solar system with its 8 planets occupies a tiny space inside a large spherical shell containing trillions of comets – the Oort Cloud. Credit: Wikimedia Commons
Planets’ orbits are only slightly tilted to each other, but Oort Cloud comets drop in from any angle they choose. Gravitational interactions with passing stars and clouds of interstellar gas nudge them into the inner solar system, where they’re cooked by the sun into glowing and long tails composed of vaporizing ice and dust. Long ago, some passing star gave ISON a push. It’s been falling toward the sun ever since.
Animation of Comet ISON’s orbit created by NASA
While it may be tough to picture Comet ISON’s orbit slicing the planetary racetrack at a 62-degree angle, the paper model will give you an intuitive understanding of ISON’s path and comet orbits in general.
P.S. In case you’re a klutz with a scissors just click on the Youtube video above.
The streaked and stained surface of Phobos. (Image: NASA)
After the tragic failure of the first Phobos-Grunt mission to even make it out of low-Earth orbit, the Russian space agency (Roscosmos) is hoping to give it another go at Mars’ largest moon with the Phobos-Grunt 2 mission in 2020. This new-and-improved version of the spacecraft will also feature a lander and return stage, and, if successful, may not only end up sending back pieces of Phobos but of Mars as well.
The origins of Phobos have long been a topic of planetary science debate. Did it form with Mars as a planet? Is it a wayward asteroid that ventured too closely to Mars? Or is it a chunk of the Red Planet blasted up into orbit from an ancient impact event? Only in-depth examination of its surface material will allow scientists to determine which scenario is most likely (or if the correct answer is really “none of the above”) and Russia’s ambitious Phobos-Grunt mission attempted to become the first ever to not only land on the 16-mile-wide moon but also send samples back to Earth.
Unfortunately it wasn’t in the cards. After launching on Nov. 9, 2011, Phobos-Grunt’s upper stage failed to ignite, stranding it in low-Earth orbit. After all attempts to re-establish communication and control of the ill-fated spacecraft failed, Phobos-Grunt crashed back to Earth on Jan. 15, impacting in the southern Pacific off the coast of Chile.
But with a decade of development already invested in the mission, Roscosmos is willing to try again. “Ad astra per aspera,” as it’s said, and Phobos-Grunt 2 will attempt to overcome all hardships in 2020 to do what its predecessor couldn’t.
And, according to participating researchers James Head and Kenneth Ramsley from Brown University in Providence, Rhode Island, the sample mission could end up being a “twofer.”
Phobos floats in front of Mars’ horizon in a Mars Express image from January 2007 (ESA)
Orbiting at an altitude of only 5,840 miles (9,400 km) Phobos has been passing through plumes material periodically blown off of Mars by impact events. Its surface soil very likely contains a good amount of Mars itself, scooped up over the millennia.
“When an impactor hits Mars, only a certain of proportion of ejecta will have enough velocity to reach the altitude of Phobos, and Phobos’ orbital path intersects only a certain proportion of that,” said Ramsley, a visiting researcher in Brown’s planetary geosciences group. “So we can crunch those numbers and find out what proportion of material on the surface of Phobos comes from Mars.”
Determining that ratio would then help figure out where Phobos was in Mars orbit millions of years ago, which in turn could point at its origins.
“Only recently — in the last several 100 million years or so — has Phobos orbited so close to Mars,” Ramsley said. “In the distant past it orbited much higher up. So that’s why you’re going to see probably 10 to 100 times higher concentration in the upper regolith as opposed to deeper down.”
In addition, having an actual sample of Phobos (along with stowaway bits of Mars) in hand on Earth, as well as all the data acquired during the mission itself, would give scientists invaluable insight to the moon’s as-yet-unknown internal composition.
“Phobos has really low density,” said Head, professor of geological sciences at Brown and an author on the study. “Is that low density due to ice in its interior or is it due to Phobos being completely fragmented, like a loose rubble pile? We don’t know.”
The study was published in Volume 87 of Space and Planetary Science (Mars impact ejecta in the regolith of Phobos: Bulk concentration and distribution.)
Sometimes the Sun is quiet, and other times the Sun gets downright unruly. During the peak of its 11-year cycle, the surface of the Sun is littered with darker sunspots. And its from these sunspots that the Sun generates massive solar flares, which can spew radiation and material in our direction. What causes these flares, and how worried should we be about them in our modern age of fragile technology? Continue reading “Astronomy Cast 321: Solar Flares”
“MOM is in normal health,” at this time according to the Indian Space Research Organization (ISRO) – which has now scheduled a supplementary main engine firing for early Tuesday (Nov. 12) to boost the crafts orbit the missing 20,000 km required.
Monday’s engine firing only raised MOM’s apogee (farthest point to Earth) from 71,623 km to 78,276 km compared to the originally planned apogee of about 100,000 [1 lakh] km), said ISRO in a press release.
This is the first serious problem to strike MOM in space. And it seemed clear to me something might be amiss when ISRO failed to quickly announce a successful completion of the 4th firing as had been the pattern for the initial three burns.
Trajectory graphic showing new supplemental 5th Midnight Maneuver thruster firing of ISRO’s Mars Orbiter Mission Spacecraft planned for Nov. 12 (IST) following the premature main engine shutdown during 4th orbit raising engine burn on Nov. 11. Credit: ISRO
The premature shutdown of the liquid fueled 440 Newton main engine “imparted an incremental velocity of 35 metres/second as against 130 metres/second originally planned,” ISRO stated.
That’s barely a quarter of what was hoped for.
“A supplementary orbit-raising operation is planned tomorrow (November 12, 2013) at 0500 hrs IST to raise the apogee to nearly 1 lakh [100,000] km.”
A series of six absolutely essential firings of the 440 Newton main engine – dubbed “midnight maneuvers” – had been originally scheduled by Indian space engineers.
The purpose of the “midnight maneuvers” is to achieve Earth escape velocity by gradually raising MOM’s apogee over several weeks, and set her on a trans Mars trajectory to the Red Planet, following the spectacular blastoff on Nov. 5 from India’s spaceport.
Graphic showing trajectory that had been planned for the Fourth Midnight Maneuver of ISRO’s Mars Orbiter Mission Spacecraft on Nov. 11 until early shutdown of the 440N liquid fueled main engine. Credit: ISRO
MOM was due to depart Earth’s orbit on Dec. 1 after accomplishing the 6th of the originally scheduled thruster firings – and begin a 10 month long interplanetary cruise to Mars.
MOM’s picture perfect Nov. 5 liftoff atop India’s highly reliable four stage Polar Satellite Launch Vehicle (PSLV) C25 from the ISRO’s Satish Dhawan Space Centre SHAR, Sriharikota, precisely injected the spacecraft into an initial elliptical Earth parking orbit of 247 x 23556 kilometers with an inclination of 19.2 degrees.
The 1st, 2nd and 3rd thruster firings were spot on and incrementally raised MOM’s apogee from 23556 km to 28814 km, 40186 km and 71,623 km respectively.
The next firing had been slated for Nov. 16.
Here’s how ISRO described the source of the main engine shutdown:
“During the fourth orbit-raising operations held today (November 11, 2013), the redundancies built-in for the propulsion system were exercised, namely, (a) energising the primary and redundant coils of the solenoid flow control valve of 440 Newton Liquid Engine and (b) logic for thrust augmentation by the attitude control thrusters, when needed.
However, when both primary and redundant coils were energised together, as one of the planned modes, the flow to the Liquid Engine stopped. The thrust level augmentation logic, as expected, came in and the operation continued using the attitude control thrusters. This sequence resulted in reduction of the incremental velocity.”
Artists concept shows Midnight Maneuver thruster firing of the liquid engine of ISRO’s Mars Orbiter Mission Spacecraft. Credit: ISRO
It is not known at this time how or whether the requirement for a supplemental “midnight maneuver” engine firing will affect the mission’s timing at Earth and its operations and longevity at Mars.
Why are the firings called midnight maneuvers?
“Firing has to happen near the perigee and in the visibility from ISTRAC ground stations. All these orbits have argument of perigee of ~285 deg. When all these constraints are put together, firings time will almost always fall in to midnights of Indian sub continent,” said ISRO in response to a readers inquiry.
In the latest update, ISRO reports: “After achieving an apogee of around 78,000 km in last night’s Maneuver, ISRO’s Mars Orbiter Mission Spacecraft is all set to reach the apogee of One lakh km in a supplementary maneuver scheduled for 5 AM tomorrow. [Nov 12].”
MOM was to arrive in the vicinity of Mars on September 24, 2014 when the absolutely essential Mars orbital insertion firing by the 440 Newton liquid fueled main engine will slow the probe and place it into a 366 km x 80,000 km elliptical orbit.
Clouds on the ground ! The sky seems inverted for a moment ! Blastoff of India’s Mars Orbiter Mission (MOM) on Nov. 5, 2013 from the Indian Space Research Organization’s (ISRO) Satish Dhawan Space Centre SHAR, Sriharikota. Credit: ISRO
If all goes well, India will join an elite club of only four who have launched probes that successfully investigated the Red Planet from orbit or the surface – following the Soviet Union, the United States and the European Space Agency (ESA).
The low cost $69 Million MOM mission is the first of two new Mars orbiter science probes from Earth blasting off for the Red Planet this November.
Half a world away, NASA’s $671 Million MAVEN orbiter remains on target to launch in less than one week on Nov. 18 – from Cape Canaveral, Florida.
Both MAVEN and MOM’s goal is to study the Martian atmosphere, unlock the mysteries of its current atmosphere and determine how, why and when the atmosphere and liquid water was lost – and how this transformed Mars climate into its cold, desiccated state of today.
The MAVEN and MOM science teams will “work together” to unlock the secrets of Mars atmosphere and climate history, MAVEN’s top scientist Prof. Bruce Jakosky told Universe Today.
Stay tuned here for continuing MOM and MAVEN news and Ken’s MAVEN launch reports from on site at the Kennedy Space Center press center
Learn more about MAVEN, MOM, Mars rovers, Orion and more at Ken’s upcoming presentations
Nov 14-19: “MAVEN Mars Launch and Curiosity Explores Mars, Orion and NASA’s Future”, Kennedy Space Center Quality Inn, Titusville, FL, 8 PM
Dec 11: “Curiosity, MAVEN and the Search for Life on Mars”, “LADEE & Antares ISS Launches from Virginia”, Rittenhouse Astronomical Society, Franklin Institute, Phila, PA, 8 PM
Comet R1 Lovejoy passes the Beehive Cluster: (Credit Damian Peach).
Tired of comets yet? Right now, northern hemisphere observers have four (!) comets within range of binoculars in the dawn sky. Comet C/2012 S1 ISON, is, of course, expected to dazzle towards month’s end. Comet 2P/Encke is an “old standby,” with the shortest orbital period of any comet known at 3.3 years, and is making a favorable appearance this Fall. And comet C/2012 X1 LINEAR added to the morning display recently, reaching about +8th magnitude in an unexpected outburst…
But the brightest and best placed comet for morning viewing is currently Comet C/2013 R1 Lovejoy. Shining at +6th magnitude, R1 Lovejoy just passed into the constellation Leo after a photogenic pass near the Beehive Cluster (M44) in Cancer last week. We caught sight of R1 Lovejoy a few mornings ago, and it’s an easy binocular object, looking like a fuzzy unresolved globular cluster with barely the hint of a tail.
If the name sounds familiar, that’s because the comet was discovered by Australian observer Terry Lovejoy, the prolific discoverer of four comets, including the brilliant sungrazing Comet C/2011 W3 Lovejoy that survived its 140,000 kilometre perihelion passage above the surface of the Sun on December 16th and went on to dazzle southern hemisphere observers in late 2011 and early 2012.
Comet R1 Lovejoy as imaged by Rob Sparks (@HalfAstro) from Tucson, Arizona passing near the Beehive cluster. (Credit: Rob Sparks).
Terry discovered R1 Lovejoy on September 7th, 2013 while it was still at magnitude +14.4. The comet is expected to top out at +4th magnitude in late November as it passes 61.4 million kilometres from Earth on November 19th and heads for perihelion at 0.877 AUs from the Sun on December 25nd, 2013. Comet R1 Lovejoy is on a 64 degree orbit highly inclined to the ecliptic, and has a period roughly 7,000 years long. The last time R1 Lovejoy graced Earthly skies, our early ancestors still thought copper smelting was a pretty hip idea!
The orbital path of Comet R1 Lovejoy through the inner solar system. (Credit: NASA/JPL Solar System Dynamics explorer).
And unlike comets Encke and ISON that are plunging near the Sun, Comet R1 Lovejoy never gets closer than 19 degrees elongation from our nearest star in late December. It also reaches a maximum northern declination of 43 degrees on November 28th, the same day that ISON reaches perihelion. For mid-latitude northern hemisphere observers, R1 Lovejoy will remain well placed at 35 to 45 degrees above the northeastern horizon about an hour before sunrise through late November.
Here are some key dates to aid you in your quest to spy Comet R1 Lovejoy in late November:
November 11th: Passes near +4.5 Kappa Leonis.
November 14th: Passes from Leo into the constellation Leo Minor & passes near the +5.3 star 20 Leonis Minoris.
November 16th: Passes near the +5th magnitude stars 28, 30, and 34 Leonis Minoris.
November 18th: Passes into the constellation Ursa Major.
November 19th: Passes near the +4.8 magnitude star 55 Ursae Majoris & +5.3 magnitude star 57 Ursae Majoris.
November 19th: Closest to Earth, at 0.4 AUs distant.
The celestial path of Comet R1 Lovejoy spanning November 11th to the 30th. (Created using Starry Night Education software).
November 21st: Passes into the constellation Canes Venatici.
November 22nd: Passes near the +6th magnitude star 4 Canum Venaticorum & the +4.2 magnitude star Chara (Beta Canum Venaticorum).
November 24th: Passes near the Sunflower Galaxy (M63).
November 27th: Passes into the constellation Boötes.
December 1st: Passes near +3.5 magnitude star Nekkar (Beta Boötis).
December 4th: crosses into Corona Borealis.
Note that passes on the list above denote passages closer than one degree of Comet R1 Lovejoy near bright objects.
Perihelion for the comet is December 25th at 0.877 AU, and its closest approach to Earth is November 19th. On this date, it will also be moving at its maximum apparent speed as seen from Earth, covering about 3 degrees of the sky every 24 hours, or the angular span of the Full Moon every 4 hours.
United Kingdom observer Pete Lawrence imaged Comet R1 Lovejoy this past weekend from his backyard garden using a 4-inch apochromatic refractor and a Canon 40D DSLR:
Comet R1 Lovejoy as imaged by Pete Lawrence on November 9th. (Credit: Pete Lawrence).
He also made his first confirmed binocular sighting of Comet ISON using a pair of 15×70 binocs, noting to Universe Today that “ISON’s head appears to be small and stellar compared to Lovejoy’s extended coma, which is obvious in binoculars, and also brighter!”
It’s worth noting that all four of these morning comets are on separate orbital paths, and only seem to be in the same general region of the sky as seen from our Earthly vantage point… and none of them are passing near the Earth!
This week is also a good time to hunt for comets in the pre-dawn sky for another reason: the Moon reaches Full this coming weekend on Sunday, November 17th. After this week, it will start to creep into the morning sky and interfere with deep sky observations for the next two weeks.
Comet R1 Lovejoy imaged on November 10th by astrophtographer Justin Ng. (Credit: Justin Ng).
It’s also interesting to note that amateur observers discovered two more faint comets this past weekend. Though comets C/2013 V3 Nevski and C/2013 V2 Borisov aren’t slated to be anything spectacular, that brings the number of amateur discoveries to 13 for 2013. Are amateur comet hunters mounting a comeback?
In this age of automated surveys, the question is often raised as to whether amateurs can still discover comets. Keep in mind, Terry Lovejoy found Comet R1 Lovejoy with a medium-sized 8-inch Schmidt Cassegrain reflecting telescope… the age of amateur comet hunters seemes far from over in 2013!
And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, sign up to be a host. Send an email to the above address.
Artist's conception of NASA's Mars Reconnaissance Orbiter. Credit: NASA/JPL
Imagine being able to watch three months’ worth of high-definition space video sequentially — maybe real-time coverage on the International Space Station, or getting to watch the Mars Reconnaissance Orbiter zoom across the Red Planet over and over again. Well, that’s how much science data MRO itself has sent back in 10 years of operations, NASA said.
“The sheer volume is impressive, but of course what’s most important is what we are learning about our neighboring planet,” stated the Jet Propulsion Laboratory’s Rich Zurek, the project scientist for the Mars Reconnaissance Orbiter.
MRO has sent back 200 terabits, all told. It’s a wealth of science data on its own merits as it examined evidence of water, ancient volcanoes and other parts of the Red Planet’s history from above. The spacecraft, however, also serves as a relay for the NASA Curiosity and Opportunity rovers on the surface.
A crater imaged by the Mars Reconnaissance Orbiter’s HiRISE (High Resolution Imaging Science Experiment). Credit: NASA/JPL/University of Arizona
“Data gathered by the orbiter’s instruments and relayed from rovers are recorded onto the orbiter’s central memory. Each orbit around Mars takes the spacecraft about two hours. For part of each orbit, Mars itself usually blocks the communication path to Earth,” NASA stated.
“When Earth is in view, a Deep Space Network antenna on whichever part of Earth is turned toward Mars at that hour can be listening. Complex preparations coordinate scheduling the use of the network’s antennas by all deep-space missions — 32 of them this month. Mars Reconnaissance Orbiter typically gets several sessions every day.”
Once the Deep Space Network antennas in Spain, California and Australia pick up the data, JPL organizes them into their separate “products”, ranging from radar measurements from above to data picked up by a rover below. The information is then sent to various organizations around the world that have interests in the work.
MRO arrived at Mars in 2006 and its mission has been extended three times, with the latest one taking place in 2012. NASA also relays information from the planet using Mars Odyssey, which has been there since 2002.
Expedition 37's Fyodor Yurchikhin (Roscosmos), Karen Nyberg (NASA) and Luca Parmitano (European Space Agency) as their Soyuz TMA-09M spacecraft safely descends to Earth on Nov. 10, 2013. Credit: NASA/Carla Cioffi
“It’s only in the moment that you’re in your spacesuit, and that the hatches are closing, that you know that four hours later, you will be back on Earth.”
That’s European Space Agency astronaut Frank De Winne talking about the emotions an astronaut or cosmonaut feels as they leave the International Space Station in a Soyuz spacecraft. The new ESA video, posted above, shows just how hard the astronauts and ground teams have to work to make sure the spacecraft gets to the right spot.
From training, to calculating orbital trajectories, to making sure the landing site in Kazakhstan is free of debris, it’s easy to see how easily those landing teams get up to dozens and dozens of people.
The undocking itself can be complex; depending on which port the Soyuz is attached to, the International Space Station itself may have to change its position to make sure the spacecraft is in the right orientation to head back to Earth.
After navigating the hazards of space, sometimes the landing site can be treacherous as well. In Kazakhstan, the mounds of snow can build up in the area in the winter time; crews need to be prepared to retrieve the spacefarers in just about any weather condition.
With an annual cost of $30.8 million, the Keck Observatory costs $53.7 thousand for a single night’s worth of operation. It will cost the James Webb Space Telescope approximately $8.8 billion to reach orbit. And the Space Launch System that will carry the Orion capsule is expected to cost $38 billion.
Why should we be spending such a vast amount of money on astronomy? How is it useful and beneficial to society?
Astronomers face this question on a daily basis. Recently a ream of European astronomers have provided tangible answers relating advancements in astronomy to advancements in industry, aerospace, energy, medicine, international collaboration, everyday life and humankind.
“I get this question quite often,” Dr. Marissa Rosenberg, lead author on the paper, told Universe Today. “One very personal reason for writing this article is that I wanted to share with my parents (both business people) why what I am doing is important and a necessary facet of society.”
Today, millions of people across the world are affected by advances in astronomy.
Industry
— Your iPhone’s camera is a charge-coupled device (CCD) — an instrument, which converts the movement of electrical charge into a digital value. Originally developed for astronomy, CCD’s are now used in most cameras, webcams and cell phones.
Every iPhone with has a built-in CCD
— The computer language Forth, originally developed for the 36-foot telescope on Kitt Peak is now used by FedEx to track packages.
— AT&T uses IRAF — software written by the National Optical Astronomy Observatory — to analyze computer systems.
— Kodak film, originally created by astronomers studying the sun, is used extensively by the medical and industrial industries, photographers and artists.
Aerospace
— Space-based telescopes have advanced defense satellites, which require identical technology and hardware.
— Global Positioning System satellites rely on astronomical objects — quasars and distant galaxies — to determine accurate positions.
Energy
— Technology gained from imaging X-rays is now used to monitor fusion — where two atomic nuclei combine to form a heavier nucleus — that may prove to be our answer for clean energy.
Medicine
Magnetic resonance imaging utilizes aperture synthesis – first an astronomical technique and now a medical technique.
Astronomy struggles to see increasingly faint objects; Medicine struggles to see things obscured within the human body.
— Aperture synthesis — the process of combining data from multiple telescopes to produce a single image seemingly created from a telescope the size of the entire collection — first developed by a radio astronomer has been used for multiple medical imaging tools, including CAT scanners and MRIs.
— Building space-based telescopes requires an extremely clean environment in order to avoid dust particles from obscuring the mirrors or instruments. Similar methods and instruments are now used in hospitals and pharmaceutical labs.
International Collaboration
— Collaboration also inspires competition. The Space Race — a competition between the Soviet Union and the United States for supremacy in space exploration — landed Neil Armstrong, Michael Collins and Buzz Aldrin on the moon.
— Astronomy is a collaborative effort. In 1887 astronomers from around the world pooled their telescope images in order to create the first map of the entire sky. Today, astronomers travel around the globe to attend conferences, learn from one another, and utilize telescopes elsewhere.
Everyday Life
— Airports utilize advances in technology designed for astronomy. X-ray observatory technology is used in X-ray luggage belts. A gas chromatograph — an instrument designed for a Mars mission — is used to analyze luggage for explosives.
— Stephen Hawking’s “A Brief History of Time” has sold over 10 million copies. Carl Sagan’s television series “Cosmos: A Personal Voyage” has been watched in over 60 countries.
Humankind
“Perhaps the most important reason to study astronomy is that astronomy seeks to satisfy our fundamental curiosity about the world we live in, and answer the ‘big’ questions,” Dr. Rosenberg told Universe Today. “How was the universe created? Where did we come from? Are there other intelligent life forms?”
Every advance in astronomy moves society closer to being able to answer these questions. With advanced technology — increasingly complex CCDs and larger ground- and space-based telescopes — we have peered into the distant, early universe, we have searched for habitable worlds, and we have come to the conclusion that we, ourselves, are stardust.
“Astronomy constantly reminds people of two seemingly contradictory things. First that the universe is infinite and we are of but the tiniest fraction of importance. And Second that life is rare and precious. A home as beautiful and unique as earth does not come often. We must protect it.”
An upcoming version of this paper will not only cover the tangible aspects of astronomy discussed here, but also the intangible aspects of astronomy.
The paper has been accepted has been published on the International Astronomical Union website and is available for download here.
This article was originally written in 2010, but we’ve now updated it and added this spiffy new video.
As you probably know, the Earth is rotating on its axis. This gives us day and night. Of course it’s impossible, but what would happen if the Earth stopped spinning? Remember, this isn’t possible, it can’t happen, so don’t worry.
Everything would be launched in a ballistic trajectory sideways
The first thing to think about is the momentum of everything on the surface of the Earth. You’re held down by gravity and you’re whizzing through space at a rotational velocity of 1,674.4 km/h (at the equator). You can’t feel it because of momentum. Just like how you can’t feel that you’re moving in a car going down the highway. But you feel the effects when you stop, or get into an accident. And so, if the Earth suddenly stopped spinning, everything on the surface of the Earth at the equator would suddenly be moving at more than 1,600 km/hour sideways. The escape velocity of Earth is about 40,000 km/hour, so that isn’t enough to fly off into space; but it would cause some horrible damage as everything flew in a ballistic trajectory sideways. Imagine the oceans sloshing sideways at 1,600 km/hour.
The rotational velocity of the Earth decreases as you head away from the equator, towards the poles. So as you got further away from the equator, your speed would decrease. If you were standing right on the north or south pole, you’d barely even feel it.
A day would last 365 days
The next problem is that day and night wouldn’t work the same any more. Right now the Earth is rotating on its axis, returning the Sun to the same position every 24 hours. But if the Earth stopped spinning, it would then take 365 days for the Sun to move through the sky and return to the same position. Half of the Earth would be baked for half a year, while the other hemisphere was in darkness. It would get very hot on the sunny side, and very cold in the shadowed side. You can imagine how that would be devastating to plants and animals. We get a hint of this at the poles, where you can experience weeks of permanent night and then weeks of permanent day. But imagine 6 months of night, followed by 6 months of day.
The Earth would become a perfect sphere
This might seem minor compared to the other catastrophes, but the Earth would become an almost perfect sphere. The Earth is currently rotating on its axis, completing one turn approximately every 24 hours. This rotational velocity causes the Earth to bulge out around its equator, turning our planet into an oblate spheroid (a flattened ball). Without this spin, gravity would be able to pull the Earth into a nice perfect sphere. This sounds interesting and probably harmless, but it’s actually a *big* problem. Because of the Earth’s bulge in the middle, the oceans are held out at the equator by 8 km. On perfect sphere Earth, the world’s oceans would redistribute, flooding many regions of the planet with an immense volume of water. We’d end up with a single continent around the middle of the planet, with oceans surrounding the north and south poles.
The Earth would no longer be tilted
The Earth’s tilt is defined by how the planet is rotating compared to the Sun. This axis of rotation defines the Earth’s seasons. But without any rotation, the concept doesn’t make sense any more. There’s still a north pole of the planet, where the radiation from the Sun is at its lowest angle, and an equator, where the light hits most directly. But there would no longer be seasons.
