Page from Ilan Ramon's diary. Credit: Israel Museum
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Pages from an astronaut’s diary survived the explosion of the space shuttle Columbia in 2003, and on Sunday, selected pages went on display at a museum in Jerusalem. Israeli astronaut Ilan Ramon kept a personal diary during his time in orbit, and portions of it were found about two months after Columbia broke apart on February 1, 2003 while returning to Earth following the STS-107 mission. “Today was the first day that I felt that I am truly living in space. I have become a man who lives and works in space,” Ramon wrote in an entry on his sixth day in orbit. Astronaut Ilan Ramon departs for his flight aboard Columbia. Credit: Chris O’Meara/Associated Press
37 pages survived the extreme heat of the explosion, as well as the 60 km (37-mile) fall to earth and several days of wet weather before they were found. “It’s almost a miracle that it survived — it’s incredible,” Israel Museum curator Yigal Zalmona said. “There is no rational explanation for how it was recovered when most of the shuttle was not.”
Diary pages as they were found. Credit: Israel Ministry of Public Security
The pages were found in a field just outside of Palestine, Texas. On some pages, the writing was washed out, other pages were tattered and torn, pocked with irregular holes as if debris had ripped through them. Pieces were twisted into tightly crumpled wads smaller than a fingernail. Some pages were stuck tightly together and had to be delicately pried apart.
Once it had been verified that the pages were relevant to the Columbia debris, the papers were collected and given to Colonel Ramon’s family. Ramon’s wife, Rona, decided to bring the papers to Israel for deciphering the damaged writing and, ultimately, conservation of the torn and tattered pages.
Most of the pages contain personal information which Mrs. Ramon did not wish to make public. “We agreed to do the restoration completely respecting the family’s privacy and the sensitivity about how intimate the document is,” museum director James Snyder said.
The diary took about a year to restore, Zalmona said, and it took police scientists about four more years to decipher the pages. About 80 percent of the text has been deciphered, and the rest remains unreadable, he said. Page of Ramon's diary that was restored using Photoshop™ and Image-Pro Plus™
Two pages will be displayed at the museum. One contains notes written by Ramon, and the other is a copy of the Kiddush prayer, a blessing over wine that Jews recite on the Sabbath. Zalmona said Ramon copied the prayer into his diary so he could recite it on the space shuttle and have the blessing broadcast to Earth.
There is no information available as to where the pages of the diary were situated during reentry, for example if they were in a pocket of Ramon’s spacesuit or in a padded, heat resistant container or simply held under his leg, as one astronaut suggested.
The diary provides no indication Ramon knew anything about potential problems on the shuttle. Columbia’s wing was gashed by a chunk of fuel tank foam insulation at liftoff and broke up just 16 minutes before it was scheduled to land at the Kennedy Space Center in Florida. All seven astronauts on board were killed.
The diary is being displayed as part of a larger exhibit of famous documents from Israel’s history, held to mark the country’s 60th anniversary this year.
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Another week, another roundup of your questions. This week listeners asked: if forces are communicated through particles, can we run out? If you were traveling at light speed, when would you know to stop? And there’s even more. If you’ve got a question for the Astronomy Cast team, please email it in to [email protected] and we’ll try to tackle it for a future show.
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We’ve talked about the Sun before, but this time we’re going to look at the entire life cycle of the Sun, and all the stages it’s going to go through: solar nebula, protostar, main sequence, red giant, white dwarf, and more. Want to know what the future holds for the Sun, get ready for the grim details.
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Curious and curiouser things began happening when telescopes opened up to the skies. Richard Baum’s book entitled “The Haunted Observatory – Curiosities from the Astronomer’s Cabinet” has the reader thinking like Alice might have in her wonderland. Bright lights, aspiring dots, gleaming trails of a forgotten impression can all fool a mind into perceiving reality where none may exist. Thus, when it comes to making reason out of the unexpected, some astronomer’s lives get so entertaining and worthwhile and ends up making this book so entertaining.
In the seventeenth century, Galileo built his own telescope, viewed moons and rebuilt our perception of the universe. Jumping off from this, telescopes came into ever more common usage so that by the eighteenth and nineteenth centuries, it seemed like everyone and their brother’s uncle had one and was getting excited about what they saw. With the increasing number of observers, some odd things were seen or at least imagined. Perhaps the sights were real events or perhaps they were dust on a lens. In any case, sometimes different people provided different interpretations, thus leading to vibrant discord. Such discord is the resonance of this book as it looks at how some disagreements were solved and how some remain to be solved.
As spiritual hauntings are resolved from much investigation, so to are the oddities in Baum’s book. As if to prove the point, the book has a quarter of its pages dedicated to references and bibliographies. Yet this content is pertinent, as Baum’s writing style interposes many large passages and quotes from external sources and intermixes them with his connecting sentences. With seven of the eleven essays previously published in 1973 and since updated, the result is a smooth flowing discourse. However, Baum likes his verbiage, as seen with phrases like ‘a chaotic vade mecum of the incongruous, the variegated and the exotic’. Given that this isn’t most people’s dictum of the day, the average reader may get bogged down. But, as Baum’s curiosities are mostly set in old European times, his words add to the book’s flavour, thus setting the tone of his investigative reporting.
And, in effect, his book reads like a collection of investigative reports. Within it, Baum usually identifies observers, equipment, date, atmospheric conditions and stellar location for each. For example, ‘he [Schroter] with the seven-foot again fit for use, picked up Venus before sunset and at six o’clock proceeded to examine it with a magnifying power of x95’. Such exact detail allows the reader to work alongside the investigation and resolve for themselves possible factors and events that might have given rise to an unexpected observation. But, the reader will quickly discover that these cases are extremely ‘cold’. That is, either the issue has been resolved (e.g. Venus doesn’t have polar ice caps) or there’s never been a repetition (e.g. strange bright light source beside Venus just as the light set on one day). Thus, the reader will enjoy this book if they like a sense of mystery and intrigue but not if they expect to resolve the investigation on their own.
An historian would also get great pleasure from reading this book. In particular, the book shows the rise of transition of technical ability, as with astronomy, into a mature, understood science. Personalities come to the fore, then they influence observations for all the right and wrong reasons and eventually shuffle quickly off this mortal coyle. Conjecture rises, flourishes and gets dashed, with no thought for social niceties. With this, the book provokes a harsh but real glimpse into scientific investigation and human frailties.
In consequence, though no spiritual ghosts permeate through the pages, Richard Baum’s book “The Haunted Observatory – Curiosities from the Astronomer’s Cabinet” is hauntingly nice. Perhaps the reader will see themselves in the pages as the young, fresh observer or the seasoned, opinionated veteran. In either case, there’s some rewarding reading when opening up this book’s pages.
Direct hit - could a huge impact on Mars have snuffed the chances of life? (Karen Carr)
[/caption]We keep sending missions to Mars with the key objective to search for past or present life. But what if a huge impact early in the Red Planet’s history hindered any future possibility for life to thrive? Recent studies into the Martian “crustal dichotomy” indicate the planet was struck by a very large object, possibly a massive asteroid. Now researchers believe that this same impact may have scrubbed any chance for life on Mars, effectively making the planet sterile. This asteroid may have penetrated the Martian crust so deep that it damaged the internal structure irreparably, preventing a strong magnetic field from enveloping the planet. The lack of a Mars magnetosphere thereby ended any chance for a nurturing atmosphere…
Mars looks odd. Early astronomers noticed it, and today’s observatories see it every time they look at the red globe. Mars has two faces. One face (the northern hemisphere) is composed of barren plains and smooth sand dunes; the other face (the southern hemisphere) is a chaotic, jagged terrain of mountains and valleys. It would appear the crustal dichotomy formed after a massive impact early in the development of Mars, leaving the planet geologically scarred for eternity. But say if this impact went beyond pure aesthetics? What if this planet-wide impact zone represents something a lot deeper?
To understand what might have happened to Mars, we have to first look at the Earth. Our planet has a powerful magnetic field that is generated near the core. Molten iron convects, dragging free electrons with it, setting up a huge dynamo outputting the strong dipolar magnetic field. As the magnetic field threads through the planet, it projects from the surface and reaches thousands of miles into space, forming a vast bubble. This bubble is known as the magnetosphere, protecting us from the damaging solar wind and prevents our atmosphere from eroding into space. Life thrives on this blue planet because Earth has a powerful magnetic solar wind defence.
Although Mars is smaller than Earth, scientists have often been at a loss to explain why there is no Martian magnetosphere. But according to the growing armada of orbiting satellites, measurements suggest that Mars did have a global magnetic field in the past. It has been the general consensus for some time that Mars’ magnetic field disappeared when the smaller planet’s interior cooled quickly and lost its ability to keep its inner iron in a convective state. With no convection comes a loss of the dynamo effect and therefore the magnetic field (and any magnetosphere) is lost. This is often cited as the reason why Mars does not have a thick atmosphere; any atmospheric gases have been eroded into space by the solar wind.
However, there may be a better explanation as to why Mars lost its magnetism. “The evidence suggests that a giant impact early in the planet’s history could have disrupted the molten core, changing the circulation and affecting the magnetic field,” said Sabine Stanley, assistant professor of physics at the University of Toronto, one of the scientists involved in this research. “We know Mars had a magnetic field which disappeared about 4 billion years ago and that this happened around the same time that the crustal dichotomy appeared, which is a possible link to an asteroid impact.”
During Mars’ evolution before 4 billion years ago, things may have looked a lot more promising. With a strong magnetic field, Mars had a thick atmosphere, protected from the ravages of the solar wind within its own magnetosphere. But, in an instant, a huge asteroid impact could have changed the course of Martian history forever.
“Mars once had a much thicker atmosphere along with standing water and a magnetic field, so it would have been a very different place to the dry barren planet we see today.” – Monica Grady, professor of planetary and space sciences at the Open University.
Losing its magnetic field after the deep asteroid impact catastrophically damaged the internal workings of the planet, Mars quickly shed its atmosphere, thereby blocking its ability to sustain life in the 4 billion years since. What a sad story…
Foton M3 after landing in Kazakhstan after the experiment. Samples, including Orkney sample, are screwed onto
[/caption]In an effort to understand how organic chemicals might survive after a period in the vacuum of space and then violent re-entry through the atmosphere, scientists have uncovered some interesting results. Last year, the ESA/Russian Foton-M3 mission was launched to test the effects of microgravity on various biological samples. However, a sample of Orkney rock had a harder journey than most. Attached to the outside of the craft, this sample underwent extreme heating during the descent toward the plains of Kazakhstan. Although most of the sample was vaporized, scientists have unveiled results that the sample still contains very obvious signs that it once harboured life. These exciting results set new limits on how organic chemicals may survive unaltered for long periods in space before plunging through a planetary atmosphere, plus it raises some interesting questions into how future searches for extraterrestrial life may be performed…
The principal mission objective for many planetary missions is the search for extraterrestrial life. Although many of our robotic explorers cannot detect life directly, they are able to carry out a host of mini lab experiments on samples taken from the planets surface. NASA’s Phoenix Mars Mission for example has been tirelessly slaving over its hot oven (a.k.a. the Thermal and Evolved-Gas Analyzer, or TEGA for short), dropping samples of Mars soil into its single-use kilns for the last few months. This effort is to vent any prebiotic chemicals into a gas form so instrumentation can then “sniff” the vapour. Should organic chemicals be found, there will be an improved chance that life may have evolved on the Red Planet’s surface.
But say if there is an easier (and cheaper) way to look for ET? Rather than sending hundreds of millions of dollars-worth of hardware to Mars to look for organic chemicals, why can’t we analyse all the rocky samples littered across the globe that originated from space? After all, we now know that some meteorites originate from Mars itself, surely we can perform a far more detailed analysis on these samples instead of depending on a robot millions of miles away?
The big stumbling block comes if we consider the extreme temperatures meteorites are put under during re-entry into the terrestrial atmosphere. Generally one would expect any evidence for past life (whether that be organic chemicals or fossilized remains) to be blow-torched out of existence by reentry temperatures up to 3,000°F (1,650°C). So, researchers from the University of Aberdeen, Scotland, decided to test a chunk of rock from a Scottish island by subjecting it to several days in space and then seeing if any evidence of life in the rock sample remained intact after the descent.
the Kazakhstan landing site of Foton-M3 in September 2007 (R. Demets/F. Brandstatter)
“The specially prepared piece of Orkney rock took part in the unmanned Foton M3 mission which aimed to examine the rock’s behaviour when it was exposed to the extreme temperatures involved in it’s re-entry through the Earth’s atmosphere,” Professor John Parnell, lead scientist in the study, said.
The reason why Orkney rock was used is because of the material’s robustness when exposed to extreme heat. After all, meteorites need to be made of tough stuff to make it to the ground. “Three quarters of the rock, which was about the size of a small pork pie, was burnt off in the experiment. However, the quarter which returned to Earth has shown us that if intelligent life were to have come into contact with the rock, it would have provided them with evidence that life exists on another planet.”
Now this is where the implications behind these results become abundantly clear. If this piece of rock was sent out into space, only for it to eventually encounter an alien world with intelligent life on its surface, it is conceivable that the rock would survive reentry, preserving the organic chemicals for further study by extraterrestrials. Of course, the reverse is true. If life existed (or exists) on Mars, perhaps we should take a closer look at those Martian meteorite samples…
In the case of the Orkney sample, it contains the remains of 400 million year-old algae, providing a rich chemical signature that Parnell and his team could detect. “We would be extremely excited if we found similar remains in a meteorite arriving from another world,” he added.
Although this experiment only scratches the surface of how organic chemicals may last, unaltered, in space (after all, should a meteoroid sample float in space for millions of years, could organic chemicals be altered by cosmic rays?), it does help us understand that for lower energy reentries, organic chemicals can indeed survive the burn…
Could the magnetic field of the Earth really reverse in 2012? I wouldn't bet on it...
[/caption]Apparently, on December 21st 2012, our planet will experience a powerful event. This time we’re not talking about Planet X, Nibiru or a “killer” solar flare, this event will originate deep within the core of our planet, forcing a catastrophic change in our protective magnetic field. Not only will we notice a rapid reduction in magnetic field strength, we’ll also see the magnetic poles rapidly reverse polarity (i.e. the north magnetic pole will be located over the South Pole and vice versa). So what does this mean to us? If we are to believe the doomsayers, we’ll be exposed to the vast quantities of radiation blasting from the Sun; with a reversing magnetic field comes a weakening in the Earth’s ability to deflect cosmic rays. Our armada of communication and military satellites will drop from orbit, adding to the chaos on the ground. There will be social unrest, warfare, famine and economic collapse. Without GPS, our airliners will also plough into the ground…
Using the Mayan Prophecy as an excuse to create new and explosive ways in which our planet may be destroyed, 20 12 2012 doomsayers use the geomagnetic shift theory as if it is set in stone. Simply because scientists have said that it might happen within the next millennium appears to be proof enough that it will happen in four years time. Alas, although this theory has some scientific backing, there is no way that anyone can predict when geomagnetic reversal might happen to the nearest day or to the nearest million years…
Firstly, let’s differentiate between geomagnetic reversal and polar shift. Geomagnetic reversal is the change in the magnetic field of the Earth, where the magnetic north pole shifts to the South Polar Region and the south magnetic pole shifts to the North Polar Region. Once this process is complete, our compasses would point toward Antarctica, rather than northern Canada. Polar shift is considered to be a less likely event that occurs a few times in the evolutionary timescale of the Solar System. There are a couple of examples of planets that have suffered a catastrophic polar shift, including Venus (which rotates in an opposite direction to all the other planets, therefore it was flipped upside down by some huge event, such as a planetary collision) and Uranus (which rotates on its side, having been knocked off-axis by an impact, or some gravitational effect caused by Jupiter and Saturn). Many authors (including the doomsayers themselves) often cite both geomagnetic reversal and polar shift as being one of the same thing. This isn’t the case.
So, on with geomagnetic reversal…
How often does it happen? The Earths interior (University of Chicago)The reasons behind the reversal of the magnetic poles is poorly understood, but it is all down to the internal dynamics of Planet Earth. As our planet spins, the molten iron in the core flows freely, forcing free electrons to flow with it. This convective motion of charged particles sets up a magnetic field which bases its poles in the North and South Polar Regions (a dipole). This is known as the dynamo effect. The resulting magnetic field approximates a bar magnet, allowing the field to envelop our planet.
This magnetic field passes through the core to the crust and pushes into space as the Earth’s magnetosphere, a protective bubble constantly being buffeted by the solar wind. As the solar wind particles are usually charged, the Earth’s powerful magnetosphere deflects the particles, only allowing them into the polar cusp regions where the polar magnetic fieldlines become “open.” The regions at which these energetic particles are allowed to enter glow as aurorae.
Usually this situation can last for aeons (a stable magnetic field threaded through the North and South Polar Regions), but occasionally, the magnetic field is known to reverse and alter in strength. Why is this?
A chart showing Earths polarity reversals over the last 160 million years. Black = normal polarity, White = reversed polarity. From Lowrie (1997)
Again, we simply do not know. We do know that this magnetic pole flip-flop has occurred many times in the last few million years, the last occurred 780,000 years ago according to ferromagnetic sediment. A few scaremongering articles have said geomagnetic reversal occurs with “clockwork regularity” – this is simply not true. As can be seen from the diagram (left), magnetic reversal has occurred fairly chaotically in the last 160 million years. Long-term data suggests that the longest stable period between magnetic “flips” is nearly 40 million years (during the Cretaceous period over 65 million years BC) and the shortest is a few hundred years.
Some 2012 theories suggest that the Earth’s geomagnetic reversal is connected to the natural 11-year solar cycle. Again, there is absolutely no scientific evidence to support this claim. No data has ever been produced suggesting a Sun-Earth magnetic polarity change connection.
So, already this doomsday theory falters in that geomagnetic reversal does not occur with “clockwork regularity,” and it has no connection with solar dynamics. We are not due a magnetic flip as we cannot predict when the next one is going to occur, magnetic reversals occur at seemingly random points in history.
What causes geomagnetic reversal? The model Earth, can a magnetic field be modelled in the lab? (Flora Lichtman, NPR)Research is afoot to try to understand the internal dynamics of our planet. As the Earth spins, the molten iron inside churns and flows in a fairly stable manner for millennia. For some reason during geomagnetic reversal, some instability causes an interruption to the steady generation of a global magnetic field, causing it to flip-flop between the poles.
In a previous Universe Today article, we discussed the efforts of geophysicist Dan Lathrop’s attempts to create his own “model Earth,” setting a 26 tonne ball (containing a molten iron analogue, sodium) spinning to see if the internal motion of the fluid could set up a magnetic field. This huge laboratory experiment is testament to the efforts being put into understanding how our Earth even generates a magnetic field, let alone why it randomly reverses.
A minority view (which, again is used by doomsayers to link geomagnetic reversal with Planet X) is that there may be some external influence that causes the reversal. You will often see associated with the Planet X/Nibiru claims that should this mystery object encounter the inner Solar System during its highly elliptical orbit, the magnetic field disturbance could upset the internal dynamics of the Earth (and the Sun, possibly generating that “killer” solar flare I discussed back in June). This theory is a poor attempt to link several doomsday scenarios with a common harbinger of doom (i.e. Planet X). There is no reason to think the strong magnetic field of the Earth can be influenced by any external force, let alone a non-existent planet (or was that a brown dwarf?).
The magnetic field strength waxes and wanes… Variations in geomagnetic field in western US since last reversal. The vertical dashed line is the critical value of intensity below which Guyodo and Valet (1999) consider several directional excursions to have occurred.New research into the Earth’s magnetic field was published recently in the September 26th issue of Science, suggesting that the Earth’s magnetic field isn’t as simple as we once believed. In addition to the North-South dipole, there is a weaker magnetic field spread around the planet, probably generated in the outer core of the Earth.
The Earth’s magnetic field is measured to vary in field strength and it is a well known fact that the magnetic field strength is currently experiencing a downward trend. The new research paper, co-authored by geochronologist Brad Singer of the University of Wisconsin, suggests that the weaker magnetic field is critical to geomagnetic reversal. Should the stronger dipole (north-south) field reduce below the magnetic field strength of this usually weaker, distributed field, a geomagnetic reversal is possible.
“The field is not always stable, the convection and the nature of the flow changes, and it can cause the dipole that’s generated to wax and wane in intensity and strength,” Singer said. “When it becomes very weak, it’s less capable of reaching to the surface of the Earth, and what you start to see emerge is this non-axial dipole, the weaker part of the field that’s left over.” Singer’s research group analysed samples of ancient lava from volcanoes in Tahiti and Germany between 500,000 and 700,000 years ago. By looking at an iron-rich mineral called magnetite in the lava, the researchers were able to deduce the direction of the magnetic field.
The spin of the electrons in the mineral is governed by the dominant magnetic field. During times of strong dipolar field, these electrons pointed toward the magnetic North Pole. During times of weak dipolar field, the electrons pointed to wherever the dominant field was, in this case the distributed magnetic field. They think that when the weakened dipolar field drops below a certain threshold, the distributed field pulls the dipolar field off-axis, causing a geomagnetic shift.
“The magnetic field is one of the most fundamental features of the Earth,” Singer said. “But it’s still one of the biggest enigmas in science. Why [the flip] happens is something people have been chasing for more than a hundred years.”
Our meandering magnetic pole The movement of Earth's north magnetic pole across the Canadian arctic, 1831--2001 (Geological Survey of Canada)Although there appears to be a current downward trend in magnetic field strength, the current magnetic field is still considered to be “above average” when compared with the variations measured in recent history. According to researchers at Scripps Institution of Oceanography, San Diego, if the magnetic field continued to decrease at the current trend, the dipolar field would effectively be zero in 500 years time. However, it is more likely that the field strength will simply rebound and increase in strength as it has done over the last several thousand years, continuing with its natural fluctuations.
The positions of the magnetic poles are also known to be wondering over Arctic and Antarctic locations. Take the magnetic north pole for example (pictured left); it has accelerated north over the Canadian plains from 10 km per year in the 20th Century to 40 km per year more recently. It is thought that if the point of magnetic north continues this trend, it will exit North America and enter Siberia in a few decades time. This is not a new phenomenon however. Ever since James Ross’ discovery of the location of the north magnetic pole for the first time in 1831, it’s location has meandered hundreds of miles (even though today’s measurements show some acceleration).
So, no doomsday then?
Geomagnetic reversal is an engrossing area of geophysical research that will continue to occupy physicists and geologists for many years to come. Although the dynamics behind this event are not fully understood, there is absolutely no scientific evidence supporting the claim that there could be a geomagnetic reversal around the time of December 21st, 2012.
Besides, the effects of such a reversal have been totally over-hyped. Should we experience geomagnetic reversal in our lifetimes (which we probably won’t), it is unlikely that we’ll be cooked alive by the Solar Wind, or be wiped out by cosmic rays. It is unlikely that we’ll suffer any mass extinction event (after all, early man, homo erectus, lived through the last geomagnetic shift, apparently with ease). We’ll most likely experience aurorae at all latitudes whilst the dipolar magnetic field settles down to its new, reversed state, and there might be a small increase in energetic particles from space (remember, just because the magnetosphere is weakened, doesn’t mean we wont have magnetic protection), but we’ll still be (largely) protected by our thick atmosphere.
Satellites may malfunction and migrating birds may become confused, but to predict world collapse is a hard pill to swallow.
In conclusion:
Geomagnetic reversal is chaotic in nature. There is no way we can predict it.
Simply because the magnetic field of the Earth is weakening does not mean it is near collapse. Geomagnetic field strength is “above average” if we compare today’s measurements with the last few million years.
The magnetic poles are not set in geographical locations, they move (at varying speeds) and have done ever since measurements began.
There is no evidence to suggest external forcing of internal geomagnetic dynamics of the Earth. Therefore there is no evidence of the solar cycle-geomagnetic shift connection. Don’t get me started on Planet X.
So, do you think there will be a geomagnetic reversal event in 2012? I thought not.
Once again, we find another 2012 doomsday scenario to be flawed in so many ways. There is no doubt that geomagnetic reversal will happen in the future for Earth, but we’re talking about time scales anything from an optimistic (and unlikely) 500 years to millions of years, certainly not in the coming four years…
Sources: NASA, US News, SciVee, How To Survive 2012, AGU
True-color and false-color image of Uranus. Credit: NASA/JPL
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Uranus is a ball of ice and gas, so you can’t really say that it has a surface. If you tried to land a spacecraft on Uranus, it would just sink down through the upper atmosphere of hydrogen and helium, and into the liquid icy center.
When we look at Uranus, we see the blue-green color that seems to come from the surface of Uranus. This color is light from the Sun reflected off Uranus’ surface. The atmosphere of Uranus contains hydrogen and helium, and most importantly, it has relatively large amounts of methane. This methane absorbs color in the red end of the spectrum of light, while photons at the blue end of the spectrum are able to reflect off the clouds and go back into space. So the full spectrum of the Sun’s light goes in, the red and orange end of the spectrum is absorbed, and the blue green end of the spectrum bounces back out. And this is why the surface of Uranus has its color.
But let’s imagine that the surface of Uranus was actually solid, and you could walk around. You might be surprised to know that you would only experience 89% the gravity that you feel back on Earth. Even though Uranus has 14.5 times more mass than Earth, it has 63 times the volume of Earth. Uranus is the second least dense planet in the Solar System, so it has a relatively weak gravity on its surface.
We have written several articles about Uranus for Universe Today. Here’s a story about what’s inside a gas giant, and here’s one about two new moons discovered for Uranus.
True-color and false-color image of Uranus. Credit: NASA/JPL
We understand the weather on Earth. The Sun heats the air at the equator, causing it to rise. The warm air goes to the poles, cools down and sinks, and then circulates back. Scientists call this Hadley Circulation. The weather on Uranus works very differently. This is because Uranus is tilted over onto its side, rotating at an angle of 99-degrees.
Over the course of its 84-year orbit, the north pole of Uranus is facing towards the Sun, and the south pole is in total darkness. And then the situation reverses for the rest of the planet’s journey around the Sun. Instead of heating the clouds at the equator, the Sun heats up one pole, and then the other. You would expect the pole facing the Sun to warm up, and to have air currents move towards the other pole.
But this isn’t what happens. The weather on Uranus follows an identical pattern to what we see on Jupiter and Saturn. The weather systems are broken up into bands that rotate around the planet. While Uranus has a completely different tilt from Jupiter and Saturn, it does have internal heat rising up from within. It appears that this internal heat plays a much bigger role in creating the planet’s weather system than the heat from the Sun.
Although less than Jupiter and Saturn, the wind speeds on Uranus can reach 900 km/hour, and seem to be changing as the planet approaches its equinox – when the rings are seen edge on.
We have written many articles about the weather on Uranus for Universe Today. Here’s one that talks about how stormy the planet can get. And here’s one about the discovery of a dark spot in the clouds on Uranus.
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The orbit of Uranus takes 84.3 year to complete one revolution around the Sun. In other words, 1 Uranian year is 84.3 Earth years.
Like the rest of the planets in the Solar System, Uranus doesn’t have a perfectly circular orbit. Instead, it follows an elliptical path around the Sun. Astronomers call a planet’s closest approach to the Sun perihelion. The perihelion for Uranus is 2.75 billion km, or 18.4 astronomical units (1 AU is the distance from the Earth to the Sun). The most distant point of orbit is called aphelion. The aphelion of Uranus is 3.00 billion km, or 20 astronomical units. On average, Uranus orbits at a distance of 2.88 billion km, or 19.2 AU.
Uranus is unique among the planets in the Solar System because of its axial tilt. While Earth is tilted at a mere 23.5 degrees, Uranus has rolled over completely sideways, with an axial tilt of 99-degrees. This has a significant impact on the planet’s seasons. The north pole of Uranus experiences 42 years of complete darkness, followed by 42 years of sunlight, where the Sun never dips below in the horizon. Astronomers aren’t sure why Uranus is flipped over sideways, but they think an impact from a protoplanet early in its history gave it the momentum it needed to roll over.
We’ve written many articles about Uranus for Universe Today. Here’s an article about how we got to see the planet’s rings edge on, and another about how the atmosphere of Uranus can be more violent than previously believed.
