Solar System

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Written by: Seanie Morris

Parent Category: Astronomy

Published: 04 November 2013

Created: 04 November 2013

Last Updated: 04 January 2014

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Comet ISON is now viewable on SOHO's LASCO C3 camera as it heads towards the Sun. Read more here. Passing within 1.3million kilometers of the Sun's surface, it's top speed will be around 1.3million kph (the numbers are coincidence)! With luck, the SOHO (and other) cameras zoned in on it will show a reappearance early Friday. If not, then we know that ISON has met a fiery end!

ISON, discovered in September 2012, was showing signs of petering out since November 23rd despite a series of outbursts from November 18th brining it up to naked eye visibility. Now we wait to see if it will survive the trip round the Sun (and not into it) and reappear in our skies.

 

Don't forget Comet 2013 R1 "Lovejoy" is one of the most recent comets currently on view since October. IFAS members share their own observations here.

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Written by: Seanie Morris

Parent Category: Astronomy

Published: 18 September 2008

Created: 18 September 2008

Last Updated: 04 January 2014

Hits: 1857

(Printed in 2006)

It was not long ago that the world was treated to Hollywood style asteroid impacts on Earth. Then, even more recently was the discovery that Earth could be hit for real on April 13th 2029 by asteroid 99942 Apophis. It was soon discovered however that Earth may be spared one of the ultimate means of destruction (just look at the dinosaurs). It now means that we will see just how close an asteroid can get – and what effect Earth will have on it.

On that day in 2029, much of Asia and Africa will get a glimpse of the brightest asteroid pass in history. While the 1,000feet in diameter asteroid is by far NOT the largest known, its close proximity will stir both fear and awe in equal amounts as scientists watch closely how Earth’s gravity will affect it, and what it may look like up close. Will Earth change the asteroids course? Will it cause it to break up? Will pieces fall off and hit us? Such questions get a very rare opportunity for such close inspection. Such occurrences happen on average once every 1,500 years. Scientists could not ask for a better opportunity than Apophis.

As Earth’s gravitational field will churn the insides of Apophis, scientists plan to use radar to track its movements inside, and telescopes to observe changes on the outside and monitor its rotation. But even the most sophisticated ground-based observations won't be sufficient for gathering detailed information about the interior of Apophis. That kind of detail would require closer inspection, such as space probes capable of measuring acceleration and seismic activity, probably embedded in the asteroid's surface. Another possibility would be to place a probe in orbit around the asteroid in order to keep tabs on it and to map its surface. There is plenty of time for all this to be planned – or so it seems.

The object in question

Apophis was discovered in the summer of 2004. It is appropriately named after the snakelike Egyptian god of darkness and chaos. For a brief period of time after Christmas, scientists had given Apophis, then known as 2004 MN4, a 1-in-40 chance of colliding with Earth in 2029.
Additional observations ruled out the 2029 impact after more accurate readings of its orbit were observed, and scientists now predict there is about a 1-in-10,000 chance that the asteroid will hit Earth in 2036, on yet another of its trips around the Sun on a course that crosses the orbit of Earth.
A large part of the uncertainty surrounding Apophis' movements is due to something called the Yarkovsky Effect. When rotating bodies (like an asteroid) pass through the Solar System, they absorb solar radiation from the Sun that they then re-radiate, mostly in the form of heat and light. This tiny but persistent pressure from this re-radiation can cause the body to speed up or slow down, and thus change its flight path.

After the recent success of missions like Stardust and Deep Impact, some scientists think it prudent to launch a space mission to determine whether Apophis poses a significant threat. With all the attention this asteroid is bound to receive, perhaps it is a good idea to start this sooner rather than later.

Interest has been so keen, that even former Apollo astronaut Rusty Schweickart sent a letter to NASA administrator Mike Griffin urging the agency to investigate whether Apophis might be affected negatively by Earth’s gravity in a manner that could put it on a more certain collision course at a future date.

In order to more accurately track its movements, Schweickart also proposed launching a space mission to place a radio transponder on Apophis by 2014, and that an intervention mission, should it prove necessary, be launched prior to 2029. It is not yet known what NASA’s response to Schweickart’s letter is.
As was seen in July’s cometry collision by the Deep Impact mission, it is possible to strike a fast moving body in space using current technologies. Already, subtle changes in the orbit of the comet that was hit, Temple 1, have been observed, but only on a miniscule scale. Over time, the actual change would be more noticeable. In order to affect Apophis’ orbit so as to make sure it doesn’t pose a threat, action must be taken much sooner than later.
Scientists urge caution, however, and say that we shouldn't rush into action. We don't want to nudge it until it is known what the nudge is going to do. The worst thing that could happen, of course, would be to nudge the asteroid in the wrong direction, based on the incomplete data now in hand, and actually cause a future collision.

And if there was a collision?

So what would happen if there was a collision? In 1998 at Sandia National Laboratories in New Mexico, scientists using virtual reality techniques, decades of experience in shock physics, advanced computer programs, and the world's fastest computer at the time, completed one of the largest hypervelocity impact physics calculations ever performed.
In the latest computing scenario, an asteroid 1 kilometres in diameter strikes the Atlantic Ocean 25 miles south of Brooklyn, New York. To model the event, the scientists broke up a 120-square-mile space that roughly approximates the New York City metropolitan area, the air above, and the water and earth below, into 100 million separate cubes, or grids. Sandia's teraflops supercomputer then calculated what happened inside each cube as the asteroid splashed down. The cubes were reassembled to produce a three-dimensional moving picture of the collision. The teraflops, the world's fastest computer at the time, performs more than one trillion mathematical operations per second.
The simulation is no video game; the calculations take into account the real world laws of physics governing time, temperature, pressure, gravity, the densities of water and earth, and hundreds of other considerations to create an accurate prediction. What's more, the resulting computer simulation can be explored using interactive virtual reality techniques. For instance, scientists can "fly through" the 3-D movie to get a better idea of what's happening on Coney Island if they want.
The computer-generated images by Sandia National Laboratories' scientists showed the impact of the 1km test asteroid hitting in the open ocean. The asteroid and 300 to 500 cubic kilometres of ocean water would be vaporized nearly instantaneously by the tremendous energy of the impact. The impact energy of about 300 gigatons of TNT would be equivalent to about 10 times the explosive power of all the nuclear weapons in existence in the 1960s at the height of the Cold War. What happens in the following tens of seconds after impact is, needless to say, frightening.
For an object the size of Apophis, it would pose a local threat with an aftermath affecting most of the world, but not on a catastrophic scale. If it landed in the ocean, tsunamis would rage across the waters, devastating low lying lands somewhat worse than what was seen in the Sumatran earthquake on December 26th last. If it struck land, local devastation would ensue, as an explosion at worst of about 250,000 tonnes of TNT would flatten any large city, immerse the surrounding area in a choking cloud of dust and smoke, and level anything in its path for miles around. Daylight would darken and become hazy for weeks afterwards around the world, the stars would be hard to see at night, plants and animals would be erratic in behaviour. Thus, using Apophis to study what could be in store in the future, is something not to be taken lightly.

What next?

Prior to Apophis’ climatic pass, it will veer within an observable distance of Earth twice in the meantime - once in 2013 and again in 2021. Based on data collected from those two flybys, scientists and NASA should be able to conclude with 99.8% accuracy whether a future impact scenario should be ruled out or not. Even though such a mission may be held back as it would cost hundreds of millions of dollars, it might be too late to find out if it was necessary, and the clean-up bill in the aftermath will be far higher.

 

Postscript – hot off the press from Australian Antarctica Division (www.aad.gov.au) on August 26th 2005:
Cosmic hole-in-one captured over Antarctica

What at first looked like an electronic glitch turned out to be a significant event in space, in fact, a cosmic hole-in-one. What a powerful telescope had picked up as it stretched towards the night sky over Antarctica was the trail of dust left in the wake of the death of an asteroid. The remarkable story features in the latest edition of the prestigious international science journal, Nature.
Lead author, Dr Andrew Klekociuk, from the Australian Antarctic Division said that early last September 2004, a physicist at Australia's Davis station in Antarctica had prepared his monitoring instrument, known as LIDAR, for keeping watch on atmospheric activity during the long night ahead.
"Just as observation of the stratosphere began a strange signal was recorded from 30 km overhead. Our physicist thought his preparation of the optics may have been amiss so fitted a filter but the signal persisted for another 30 minutes. What he didn't know at the time was that seven hours earlier an asteroid had crashed to Earth in another part of Antarctica, about 1500 km west of Davis. The closest it got to human habitation was around 900 km west of Japan's Syowa station," Dr Klekociuk said.
Shortly after the LIDAR observations it was revealed that the event had also been picked up by the global network of satellites and a range of other instruments. But the most detailed evidence of the trail of dust, carried by strong winds around Antarctica, has been captured by the LIDAR at Davis station.
Dr Klekociuk said that it was thought that the asteroid had come from what is known as the Aten group somewhere between Venus and Earth, ranging anywhere up to 46 million km from the sun. Measuring roughly 10 metres it is the biggest body to enter Earth's atmosphere in the past decade. Its travel time from entering Earth's atmosphere 75 km up until it landed was just five seconds.
Scientists believe that the asteroid's original size was close to that of a small house weighing a thousand tonnes and that if it had not broken up on entry into the atmosphere its effect on impact would have been that of the bomb dropped on Hiroshima. The size of the dust cloud in the stratosphere was 200 km by 75 km. Had a cloud that size passed over the sun the light would have dimmed by around 20 per cent. Inevitably particles contained in the dust cloud have fallen to Earth and samples from all three Australian Antarctic continental stations - Davis, Casey and Mawson -- have been retrieved for analysis at the Australian
Antarctic Division."
Dr Klekociuk said that these analyses will enable scientists to validate models of atmospheric circulation. The timing and location of the event will also allow for testing theories relating to the impact of large meteorites on ozone and climate. While there were no obvious short-term associated changes in regional
climate or ozone levels, the longer term implications are still being evaluated.
The LIDAR, developed by the Australian Antarctic Division in collaboration with the Adelaide University, was installed during the summer of 2000.

If you thought being hit by bird poop was lucky…

On 30th November 1953 in Sylocuga, Alabama, Mrs. Hewlett Hodges was struck on the hip by a meteorite that had crashed through her ceiling. It is reported that after penetrating the roof and ceiling of her home, it first bounced off the radio, and then hit her when she was lying on the couch. She suffered only minor bruising and had to rest for a few days.
Another near miss occurred in 1991 at around 11:30am on 5th May. Mr Arthur Pettifor was busy gardening at his Glatton village home in Cambridgeshire, England, about 70 miles North of London. Suddenly, he heard a loud whining noise and saw something crash through his conifer hedge, just a few feet away from where he stood. Below the conifers, he found a black rock sitting in a shallow depression and assumed that local "hooligans had thrown the stone" into his garden. Within a few seconds of it's fall, he picked it up, noticing that the stone felt warm to the touch, and then quickly guessed that this black crusted rock was something much more extraordinary. Sure enough, the stone was soon confirmed as a meteorite by visiting meteoriticists.
Despite a thorough search of the surrounding area, no more meteorites were recovered - and if Mr Pettifor hadn't been out in his garden at the time, the Glatton meteorite would not have been recognised at all!
Mr Pettifor kept the meteorite for a few months (carefully wrapped in plastic Cling Film on the advice of the Natural History Museum) and displayed it at his local Summer fete, charging a small fee (donated to the church fund) to view the meteorite. Later, the little space rock was sold to the museum, where it still remains today.

Details

Written by: Seanie Morris

Parent Category: Astronomy

Published: 18 September 2008

Created: 18 September 2008

Last Updated: 04 January 2014

Hits: 2465

(Originally printed in c.2000)

MERCURY FACTS:
Fact One:
Before the first space-crafts flew to Mercury to take pictures of its surface, some astronomers believed that the planet would have a smooth surface. When Mariner 10 took pictures of Mercury during its flyby of Venus and Mercury in November 1973, scientists discovered that Mercury is the most cratered planet in the Solar System with a surface similar to Earth's Moon.

Fact Two:
Mercury has no atmosphere at all. Sunlight reflects off its surface, similar to how light is reflected directly off the Moon's surface. The lack of atmosphere means that sunlight cannot be spread through the atmosphere. The planet's sky is dark, just like the Moon's and, if you were able to stand on the side of the planet not facing the Sun, you would be able to see billions of stars in the sky.

Fact Three:
A year on Mercury is only 88 days long, but a full day (from sunset to sunrise) takes 176 days, even though the planet takes 59 days to rotate on its axis. This causes the Sun to rise above the horizon at the beginning of a Mercurian day in the East (as on Earth), then move higher into the sky, move back down towards the horizon at the East, and then quickly move over to the Western horizon to set, after about 60 days!

Fact Four:
Mercury (4,878km wide) is slightly bigger than Earth's Moon (3475.6km wide) and is smaller than Ganymede (5,270km) and Callisto (4,890km), two of Jupiter's moons, and Titan (5,150km wide), a moon of Saturn.

Fact Five:
Mercury can only be seen just after the Sun has risen and just before the sun sets.

Fact Six:
If you were to stand on Mercury, the Sun would appear two and a half times bigger than it appears on Earth.

Fact Seven:
Mercury is about 100 times closer to the Sun than Pluto, the most distant planet in the Solar System.

Fact Eight:
Mercury's speed is caused by the Sun's strong gravitational pull. Hold a short piece of string with something tied to the end of it and spin it around. Try it again with a longer piece of string. Notice how much longer it takes for the object tied to the end of it to spin round. Your finger acts like the Sun, and the object acts like a planet orbiting the Sun.

Fact Nine:
Despite being the closest planet to the Sun, Mercury is not the warmest. Venus is warmer. In fact, Mercury can be one of the coldest planets in the Solar System

Fact Ten:
By the time one year has passed on Pluto (after 248 years), 1028 years have happened on Mercury!



 
VENUS FACTS:
Fact One:
Venus and Mercury are the only two planets in the Solar System not to have moons orbiting them.

Fact Two:
If we were able to stand on the surface of Venus, it would feel like being 1 kilometre under the sea on Earth, a depth deep enough to sink a submarine. A person or a creature would immediately be crushed by Venus' amazingly strong pressure.

Fact Three:
Venus may have such a thick atmosphere because it spins so slowly. In fact, a year on Venus is shorter than its day. It takes the planet longer to turn on its axis than it takes it to orbit the Sun. The slow rotation means that atmosphere does not have a force to spin off into space.

Fact Four:
Venus is the only planet in the Solar System to turn clockwise. All other planets turn anti-clockwise. It rotates clockwise on its axis extremely slowly, suggesting that something might have once collided with it to disrupt its regular rotation.

Fact Five:
People once believed Venus to be two different stars known as the Morning Star and the Evening Star, because it can be seen in the morning and the evening.

Fact Six:
After the Sun and the Moon, Venus is the brightest object in the night-sky from Earth

Fact Seven:
The Americans have only ever landed one probe on Venus. This was Pioneer Venus 2, launched on 8th August 1978 which was to probe the planet's atmosphere, not examine its surface. All other landings on Venus were made by the Russians. There are no plans for missions to return to Venus in the near future.

Fact Eight:
Venus' axis hardly has any tilt at all, unlike Mars and Earth. This means that, if it had a thin atmosphere, the planet would not have seasons.

Fact Nine:
There are more volcanoes on Venus than on any other planet in the Solar System, although it is not yet known whether any of these volcanoes are still active.

Fact Ten:
Venus may now resemble what Earth will become in millions of years time, when the Sun expands, heats the Earth, turning all of its surface water into a vapour which will trap sunlight and heat in its atmosphere, causing suffocating conditions like those on Venus.




MARS FACTS:
Fact One:
Of all the planets in the Solar System, Mars is the one people believe is most likely to contain or to have contained life. In 1900, a prize was offered to the first person to be contact an extra-terrestrial being. However, this extra-terrestrial being was not allowed to come from Mars because that would make the competition too easy! In 1938, a radio broadcast of The War of the Worlds by H.G. Wells (a story about an invasion of Earth by Martians) caused a near panic in America because so many people believed it to be true.

Fact Two:
The largest volcano in the Solar System is on Mars. It is called Olympus Mons.

Fact Three:
Mars has polar caps like Earth, containing frozen carbon dioxide (and small amount of water).

Fact Four:
Mars is believed to have had water flowing around it like Earth once. It may have had a blue sky too. However, it is unlikely that it had grass, trees and plants like Earth has now.

Fact Five:
The Valles Marineris, the greatest gorge on any planet in the Solar System, was caused when volcanoes erupting around it tore up the land, leaving a huge valley.

Fact Six:
We can see how long Mars has been a 'dead' planet by the number of meteorite impacts on its surface. In comparison, Earth and Venus have fewer impact craters because they have newer surfaces formed by recent geological activity.

Fact Seven:
Mars has seasons like Earth. This is caused by the tilt of the planet's axis, at a similar angle to the tilt of Earth's axis.

Fact Eight:
The Sun appears about half the size on Mars as it does from Earth.

Fact Nine:
The first space probe to take pictures of Mars' surface (Mariner 4 in 1964) is still in space, orbiting the Sun. Still orbiting Mars itself are Mariner 9 (launched in 1971), Viking 1 and 2 (launched in 1975), the Mars Global Surveyor (launched in 1996, which is currently looking for the Mars Polar Lander, launched in 1998) and the Mars Climate Orbitor (launched in 1998 to orbit Mars in 1999). These are American space probes. Russian probes orbiting Mars are Mars 2 and Mars 3 (launched in 1971), Mars 5 (launched in 1973) and Phobos 1 (launched in 1988). Japan has Nozomi orbiting Mars (launched in 1998).

Fact Ten:
Rocks from Mars have landed on Earth from meteorite impacts blasting debris through space.


JUPITER FACTS:
Fact One:
Jupiter has a liquid metal ocean (metallic hydrogen) at its centre, surrounding by thousands of kilometres of hydrogen and helium gas.

Fact Two:
Jupiter's famous Red Spot is in fact a great storm that has raged for at least four hundred years.

Fact Three:
Jupiter has a thin set of rings, hardly visible from Earth.

Fact Four:
Jupiter is the vacuum cleaner of the Solar System. It sucks in comets, asteroids and meteorites which could be on a collision course for Earth. For example, Shoemaker-Levy 9 in 1994.

Fact Five:
Jupiter takes only 9 hours and 55 minutes to spin on its axis. This means a day on Jupiter is less than 10 hours long. Its fast rotation causes the planet to be squashed, being wider at the equator than from North to South.

Fact Six:
Jupiter is the planet with the strongest pull of gravity in the Solar System. If we were able to stand on the surface of Jupiter, we would weigh three times as much as we would way on Earth. The only other object in the Solar System with a stronger pull of gravity is the Sun.

Fact Seven:
The mass of Jupiter is 318 greater than the mass of Earth.

Fact Eight:
Jupiter's moon, Ganymede, is the biggest moon in the Solar System.

Fact Nine:
If we were able to see Jupiter's radiation belt from Earth, Jupiter would appear as big as the Sun.

Fact Ten:
Jupiter's gravity is used to catapult space-craft on deep space missions further away. This is how the Voyager missions of 1975 managed to succeed.


SATURN FACTS:
Fact One:
Saturn has the most moons in the Solar System, including Titan, a moon with an atmosphere possibly similar to Earth's billions of years ago.

Fact Two:
Saturn is a slightly smaller version of Jupiter, with similar, but less distinctive, surface patterns. Its only main difference is its amazing rings.

Fact Three:
Saturn's rings are believed to be the particles of a old moon orbiting the planet, smashed apart in a collision about 50 million years ago.

Fact Four:
Saturn's rings orbit the planet at different tilts. Sometimes, they can appear like 'ears' sticking out of the planet. At other times, they are flat on when seen from Earth and are hardly visible. This shows how thin they can be.

Fact Five:
It is believed that Saturn's rings will one day disappear. They will either disperse (spread out) into space or get sucked into the planet by its pull of gravity. This will happen in about 50 million years.

Fact Six:
Despite its similarities to Jupiter, there is no great spot on Saturn, although the planet does have stormy weather.

Fact Seven:
Saturn is twice as far away from the Sun as Jupiter is.

Fact Eight:
Saturn is the second largest planet in the Solar System after Jupiter. It is so big that Earth could fit into it 755 times.

Fact Nine:
Saturn has such a low density (meaning that its particles are far apart) that, if there was an ocean big enough, Saturn would float on it. In comparison, Earth and Mercury would sink to the bottom quickest.

Fact Ten:
A year on Saturn would take almost thirty Earth years.



URANUS FACTS:
Fact One:
After Saturn, a space-craft would have to travel 1,500,000,000 kilometres to reach Uranus. This means the planet is almost twice the distance from the Sun than Saturn is.

Fact Two:
Uranus orbits the Sun on its side. Its South Pole is pointed towards Earth. The angle of the tilt of the axis of Uranus is 97 degrees.

Fact Three:
When the first pictures of Uranus from Voyager 2 were received on Earth in January 1986, scientists were disappointed to see a planet with a featureless, pale blue surface.

Fact Four:
Uranus' pale blue colour is caused by the methane in its atmosphere which filters out red light.

Fact Five:
If we were able to see Uranus' moons orbiting the planet, they would go over and under the planet like lights on a ferris wheel.

Fact Six:
Uranus has rings of ice and small rock particles which are so faint they appear as black as charcoal.

Fact Seven:
Uranus has 15 moons (so far discovered) orbiting the planet. Ten of these were discovered in 1986 by the Voyager 2 mission.

Fact Eight:
A year on Uranus would last 84 years.

Fact Nine:
A day on Uranus is only slightly shorter than a day on Earth, at about 17 hours long.

Fact Ten:
Because of Uranus' unique tilt, a night at one of its poles lasts for 21 Earth years, during which it will receive no light or heat at all from the Sun.



NEPTUNE FACTS:
Fact One:
Neptune's moon, Triton, is slowly getting closer to Neptune. Eventually, it will get so close that it will get torn apart by Neptune's gravity and possibly form rings more spectacular than Saturn's.

Fact Two:
The strongest winds in the Solar System have been recorded on Neptune, at speeds of up to 2,000 kilometres per hour.

Fact Three:
Neptune has dark spots similar to the Great Red Spot on Jupiter. These are areas of high atmospheric pressure which force clouds of methane gas high up into the atmosphere, appearing like cirrus (thin, whispy) clouds on Earth. However, these spots disappear and reappear on different parts of the planet, unlike Jupiter's spot.

Fact Four:
Neptune sometimes orbits the Sun further away than Pluto making it the most distant planet in the Solar System. It returned to its usual position as the second furthest planet away from the Sun in December 1999.

Fact Five:
Triton orbits Neptune in the opposite direction to the planet's rotation. It is the only large moon in the Solar System to do this.

Fact Six:
Neptune has four faint rings. Some parts of these rings are brighter in areas than others and appear like arcs orbiting the planet. Maybe they are still forming.

Fact Seven:
Since its discovery in 1846, Neptune has not yet completed a full orbit. In fact, it takes 165 years for the planet to go around the Sun.

Fact Eight:
Neptune was discovered when scientists noticed something peculiar about Uranus' orbit, believing something to be pulling it in the opposite direction to the Sun's pull of gravity. They calculated the position of a planet and soon afterwards, discovered Neptune.

Fact Nine:
The coldest temperatures measured in the Solar System (-230°c) have been recorded on Neptune's moon, Triton.

Fact Ten:
Pluto, a planet which has an orbit which sometimes crosses Neptune's, may have been a moon of Neptune which escaped the planet's pull of gravity, but being prevented from escaping the Solar System by the gravitational pull of the Sun.



PLUTO FACTS:
Fact One:
Pluto is the smallest planet in the Solar System, smaller than Earth's Moon, and half the width of Jupiter's moon, Ganymede.

Fact Two:
Pluto orbits the Sun on a different plain than the other 8 planets, going over them and below them.

Fact Three:
Pluto's orbit is elliptical, meaning that it can come closer to the Sun than Neptune, but then go almost two billion kilometres further away from Neptune's orbit. In the picture below, you can see Pluto's orbit (in grey) and Neptune's orbit (in blue)



Fact Four:
Pluto has one moon, Charon, which is not much smaller than Pluto itself. No other moon is as close to the size of its planet as Charon is to Pluto. (Pluto is 2,280 kilometres wide, Charon is 1,212 kilometres wide).

Fact Five:
Pluto's journey around the Sun takes 248 Earth years. This means that, since its discovery in 1930, it still has 177 years to go until it has made a complete orbit around the Sun.

Fact Six:
Pluto is the only planet in the Solar System not to have been visited by a space probe.

Fact Seven:
Pluto is the planet with the lowest pull of gravity in the Solar System. This will explain why its moon, Charon, orbits the planet so closely (at a distance of 19,640 kilometres).

Fact Eight:
Pluto was the only planet to have been discovered in the Twentieth Century.

Fact Nine:
A day on Pluto lasts for 6 days and 9 hours, meaning that it has the second slowest speed of rotation in the Solar System (after Venus, which takes 243 days to turn on its axis).

Fact Ten:
Nobody knows what Pluto's atmosphere contains, or even if it has an atmosphere. Any atmosphere is most likely to contain nitrogen.