Sunday, December 13, 2015

10 Interesting Facts About Neptune

10 Interesting Facts About Neptune:



Reconstruction of Voyager 2 images showing the Great Black spot (top left), Scooter (middle), and the Small Black Spot (lower right). Credit: NASA/JPL


Neptune is a truly fascinating world. But as it is, there is much that people don't know about it. Perhaps it is because Neptune is the most distant planet from our Sun, or because so few exploratory missions have ventured that far out into our Solar System. But regardless of the reason, Neptune is a gas (and ice) giant that is full of wonder!

Below, we have compiled a list of 10 interesting facts about this planet. Some of them, you might already know. But others are sure to surprise and maybe even astound you. Enjoy!

1. Neptune is the most distant planet:
This may sound like a pretty simple statement, but it's actually rather complicated. When it was first discovered by in 1846, Neptune became the most distant planet in the Solar System. But then in 1930, Pluto was discovered, and Neptune became the second-most distant planet. But Pluto's orbit is very elliptical; and so there are periods when Pluto actually orbits closer to the Sun than Neptune. The last time this happened was in 1979, which lasted until 1999. During that period, Neptune was again the most distant planet.

Then, at the XXVIth General Assembly of the International Astronomical Union - which took place between Aug 14th and 25th, 2006, in Prague - the issue of which was the most distant planet was visited once again. Confronted with the discovery of many Pluto-sized bodies in the Kuiper Belt - i.e. Eris, Haumea, Sedna and Makemake - and the ongoing case of Ceres, the IAU decided it was time to work out a clear definition of what a planet was.

https://youtu.be/BKoRt-6pjAE

In what would prove to be a very controversial decision, the IAU's passed a resolution which defined a planet as “a celestial body orbiting a star that is massive enough to be rounded by its own gravity but has not cleared its neighboring region of planetesimals and is not a satellite. More explicitly, it has to have sufficient mass to overcome its compressive strength and achieve hydrostatic equilibrium.”

As a result of this, Pluto was "demoted" from the status of planet and thereafter defined as a "dwarf planet" instead. And so, Neptune has once again become the most distant planet. At least for now...

2. Neptune is the smallest of the gas giants:
With an equatorial radius of only 24,764 km, Neptune is smaller than all the other gas giants in the Solar System: Jupiter, Saturn and Uranus. But here's the funny thing: Neptune is actually more massive than Uranus by about 18%. Since it's smaller but more massive, Neptune has  a much higher  density than Uranus. In fact, at 1.638 g/cm3, Neptune is the densest gas giant in the Solar System.

3. Neptune's surface gravity is almost Earth-like:
Neptune is a ball of gas and ice, probably with a rocky core. There's no way you could actually stand on the surface of Neptune without just sinking in. However, if you could stand on the surface of Neptune, you would notice something amazing. The force of gravity pulling you down is almost exactly the same as the force of gravity you feel walking here on Earth.

https://youtu.be/htr9lH1PEUU

The gravity of Neptune is only 17% stronger than Earth gravity. That's actually the closest to Earth gravity (one g) in the Solar System. Neptune has 17 times the mass of Earth, but also has almost 4 times larger. This means its greater mass is spread out over a larger volume, and down at the surface, the pull of gravity would be almost identical. Except for the part where you wouldn't stop sinking!

4. The discovery of Neptune is still a controversy:
The first person to have seen Neptune was likely Galileo, who marked it as a star in one of his drawings. However, since he did not identify it as a planet, he is not credited with the discovery. That credit goes to French mathematician Urbain Le Verrier and the English mathematician John Couch Adams, both of whom predicted that a new planet - known as Planet X - would be discovered in a specific region of the sky.

When astronomer Johann Gottfried Galle actually found the planet in 1846, both mathematicians took credit for the discovery. English and French astronomers battled over who made the discovery first, and there are still defenders of each claim to this day. Today, the consensus among astronomers is that Le Verrier and Adams deserve equal credit for the discovery.

5. Neptune has the strongest winds in the Solar System:
Think a hurricane is scary? Imagine a hurricane with winds that go up to 2,100 km/hour. As you can probably imagine, scientists are puzzled how an icy cold planet like Neptune can get its cloud tops t0 move so fast. One idea is that the cold temperatures and the flow of fluid gasses in the planet's atmosphere might reduce friction to the point that it's easy to generate winds that move so quickly.

https://youtu.be/43-xLP-1a7M

6. Neptune is the coldest planet in the Solar System:
At the top of its clouds, temperatures on Neptune can dip down to 51.7 Kelvin, or -221.45 degrees Celsius (-366.6 °F). That's over twice the freezing point of water, which means that an unprotected human being would flash freeze in a second! Pluto gets colder, experiencing temperatures as low as 33 K (?240 °C/-400 °F). But then again, Pluto isn't a planet any more (remember?)

7. Neptune has rings:
When people think of ring systems, Saturn is usually the planet that comes to mind. But would it surprise you to know that Neptune has a ring system as well? Unfortunately, it is rather difficult to observe compared to Saturn's bright, bold ring; which is why it is not so well-recognized. In total, Neptune has five rings, all of which are named after astronomers who made important discoveries about Neptune - Galle, Le Verrier, Lassell, Arago, and Adams.

These rings are composed of at least 20% dust (with some containing as much as 70%) which are micrometer-sized, similar to the particles that make up the rings of Jupiter. The rest of the ring materials consists of small rocks. The planet’s rings are difficult to see because they are dark, which is likely due to the presence of organic compounds that have been altered due to exposition to cosmic radiation. This is similar to the rings of Uranus, but very different than the icy rings around Saturn.

It’s believed that the rings of Neptune are relatively young – much younger than the age of the Solar System, and much younger than the age of Uranus’ rings. Consistent with the theory that Triton was a Kuiper Belt Object (KBO) that was seized by Neptune’s gravity (see below), they are believed to be the result of a collision between some of the planet’s original moons.

https://youtu.be/4R4usDbSLzk

 

8. Neptune probably captured its largest moon, Triton:
Neptune's largest Moon, Triton, circles Neptune in a retrograde orbit. That's means that it orbits the planet backwards relative to Neptune's other moons. This is seen as an indication that Neptune probably captured Triton - i.e. the moon didn't form in place like the rest of Neptune's moons. Triton is locked into a synchronous rotation with Neptune, and is slowly spiraling inward towards the planet.

At some point, billions of years from now, Triton will likely will be torn apart by Neptune's gravitational forces and become a magnificent ring around the planet. This ring will be pulled inward and crash into the planet. It is too bad that such an event will be happening so very long from now, because it would be amazing to watch!

9. Neptune has only been visited once up close:
The only spacecraft that has ever visited Neptune was NASA's Voyager 2 spacecraft, which visited the planet during its Grand Tour of the Solar System. Voyager 2 made its Neptune flyby on August 25, 1989, passing within 3,000 km of the planet's north pole. This was the closest approach to any object that Voyager 2 made since it was launched from Earth.

During its flyby, Voyager 2 studied Neptune's atmosphere, its rings, magnetosphere, and also conduct a close flyby of Triton. Voyager 2 also viewed Neptune's "Great Dark Spot", the rotating storm system which has since disappeared, according to observations by the Hubble Space Telescope. Originally thought to be a large cloud itself, the information gathered by Voyager helped to shed light on the true nature of this phenomenon.

https://youtu.be/COI5LBpvDyU

10. There are no plans to visit Neptune again:
Voyager 2's amazing photographs of Neptune might be all we get for decades, as there are no firm plans to return to the Neptune system.  However, a possible Flagship Mission has been envisioned by NASA to take place sometime during the late 2020s or early 2030s. For example, in 2003, NASA announced tentative plans to send a new Cassini-Huygens-style mission to Neptune, called the Neptune Orbiter.

Also described as a "Neptune Orbiter with Probes", this spacecraft had a proposed launch date of 2016, and would arriving around Neptune by 2030. The proposed mission would go into orbit around the planet and study its weather, magnetosphere, ring system and moons. However, no information on this project has been forthcoming in recent years and it appears to have been scrapped.

Another, more recent proposal by NASA was for Argo - a flyby spacecraft that would be launched in 2019, which would visit Jupiter, Saturn, Neptune, and a Kuiper belt object. The focus would be on Neptune and its largest moon Triton, which would be investigated around 2029.

And these are just of the things that make Neptune such a fascinating planet, and one that is worthy of study. One can only hope that future missions will be launched to the outer Solar System that will be able to dig deeper into its many mysteries.

We have many interesting articles about Neptune here at Universe Today. Here is one about the Rings of Neptune, the Moons of Neptune, Who Discovered Neptune?, and Are There Oceans on Neptune?

If you'd like more information on Neptune, take a look at Hubblesite's News Releases about Neptune, and here's a link to NASA's Solar System Exploration Guide to Neptune.

Astronomy Cast has some interesting episodes about Neptune. You can listen here, Episode 63: Neptune and Episode 199: The Voyager Program.


Posted by Nelio Inacio at 12:51 PM 0 comments

Friday, December 11, 2015

Cygnus: Bubble and Crescent

Cygnus: Bubble and Crescent: APOD: 2015 December 4 - Cygnus: Bubble and Crescent



Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.


2015 December 4


See Explanation. Clicking on the picture will download the highest resolution version available.



Cygnus: Bubble and Crescent
Image Credit & Copyright: Ivan Eder
Explanation: These clouds of gas and dust drift through rich star fields along the plane of our Milky Way Galaxy toward the high flying constellation Cygnus. Caught within the telescopic field of view are the Soap Bubble (lower left) and the Crescent Nebula (upper right). Both were formed at a final phase in the life of a star. Also known as NGC 6888, the Crescent was shaped as its bright, central massive Wolf-Rayet star, WR 136, shed its outer envelope in a strong stellar wind. Burning through fuel at a prodigious rate, WR 136 is near the end of a short life that should finish in a spectacular supernova explosion. recently discovered Soap Bubble Nebula is likely a planetary nebula, the final shroud of a lower mass, long-lived, sun-like star destined to become a slowly cooling white dwarf. While both are some 5,000 light-years or so distant, the larger Crescent Nebula is around 25 light-years across.

Tomorrow's picture: exo-orrery
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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.


Posted by Nelio Inacio at 7:11 AM 0 comments

Comet Catalina Emerges

Comet Catalina Emerges:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2015 December 7


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Comet Catalina is ready for its close-up. The giant snowball from the outer Solar System, known formally as C/2013 US10 (Catalina), rounded the Sun last month and is now headed for its closest approach to Earth in January. With the glow of the Moon now also out of the way, morning observers in Earth's northern hemisphere are getting their best ever view of the new comet. And Comet Catalina is not disappointing. Although not as bright as early predictions, the comet is sporting both dust (lower left) and ion (upper right) tails, making it an impressive object for binoculars and long-exposure cameras. The featured image was taken last week from the Canary Islands, off the northwest coast of Africa. Sky enthusiasts around the world will surely be tracking the comet over the next few months to see how it evolves.

Posted by Nelio Inacio at 7:10 AM 0 comments

Arp 87: Merging Galaxies from Hubble

Arp 87: Merging Galaxies from Hubble: APOD: 2015 December 9 - Arp 87: Merging Galaxies from Hubble



Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.


2015 December 9


See Explanation. Clicking on the picture will download the highest resolution version available.



Arp 87: Merging Galaxies from Hubble
Image Credit: NASA, ESA, Hubble Space Telescope; Processing: Douglas Gardner
Explanation: This dance is to the death. Along the way, as these two large galaxies duel, a cosmic bridge of stars, gas, and dust currently stretches over 75,000 light-years and joins them. The bridge itself is strong evidence that these two immense star systems have passed close to each other and experienced violent tides induced by mutual gravity. As further evidence, the face-on spiral galaxy on the right, also known as NGC 3808A, exhibits many young blue star clusters produced in a burst of star formation. The twisted edge-on spiral on the left (NGC 3808B) seems to be wrapped in the material bridging the galaxies and surrounded by a curious polar ring. Together, the system is known as Arp 87 and morphologically classified, technically, as peculiar. While such interactions are drawn out over billions of years, repeated close passages should ultimately result in the death of one galaxy in the sense that only one galaxy will eventually result. Although this scenario does look peculiar, galactic mergers are thought to be common, with Arp 87 representing a stage in this inevitable process. The Arp 87 pair are about 300 million light-years distant toward the constellation Leo. The prominent edge-on spiral at the far left appears to be a more distant background galaxy and not involved in the on-going merger.

Tomorrow's picture: series cytherean
< | Archive | Submissions | Index | Search | Calendar | RSS | Education | About APOD | Discuss | >
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.


Posted by Nelio Inacio at 7:09 AM 0 comments

Viewing Guide to the 2015 Geminid Meteor Shower

Viewing Guide to the 2015 Geminid Meteor Shower:



A brilliant Geminid meteor shower photographed from Mt. Balang, China. Credit: NASA/Kevin Wu


A brilliant Geminid flashes below Sirius and Orion over Mount Balang in China. Credit: NASA/Alvin Wu
2015 looks like a fantastic year for the Geminids. With the Moon just 3 days past new and setting at the end of evening twilight, conditions couldn’t be more ideal. Provided the weather cooperates! But even there we get a break. With a maximum of 120 meteors per hour, the shower is expected to peak around 18:00 UT (1 p.m. EST, 10 a.m. PST) December 14th, making for two nights of approximately equal activity: Sunday night Dec. 13-14 and Monday night Dec. 14-15.



You can start watching for Geminids early in the evening December 13th. The radiant of the shower lies near the bright pair of stars, Castor and Pollux. Source: Stellarium


You can start watching for Geminids early in the evening both Sunday and Monday nights (Dec. 13-14). The shower radiant lies right next door to the bright stellar duo Castor and Pollux in the constellation Gemini above Orion. Source: Stellarium
That 120 meteor tally would be what you’d see from a dark, moonless sky with the radiant at the zenith. Your count will vary depending on whether you observe from the suburbs or the countryside and what time of night you go out. Closer to 50 per hour from locations near moderate-sized cities might be more realistic. Many meteor showers require getting up in the wee hours of the morning when the radiant has climbed high enough for a good view. Happily, the Geminids are different. The shower radiant already stands some 30° high in the eastern sky at 10 o’clock local time, making for a good hour of meteor-watching before you hit the hay Sunday night.



Two needle-like Geminids flash through the view in this photo taken during the 2012 maximum. Credit: Bob King


Two needle-like Geminids flash through the view in this photo taken during the 2012 maximum. Geminid meteors are markedly slower than the summer Perseids (about half as fast) but have their share of fireballs. Credit: Bob King
Gemini crosses the meridian high in the southern sky for skywatchers at mid-northern latitudes around 2 a.m. this weekend — the time you’d expect to see the most meteors per hour. But hey, who’s counting? Find a location with a wide-open view of the sky and tuck yourself under a sleeping bag in a comfy reclining chair. Creature comforts like coffee or a radio playing softly in the background will make you feel like you never had it so good. Then stare off into space and let come what may.,

Because all shower meteors arrive on parallel paths traveling at the same speed, they appear to radiate from a single point in the sky. The radiant is nothing more than a perspective effect, the very same as railroad tracks appearing to converge in the distance. Meteors near the radiant leave very short trails; the farther away you look, the longer the trail.

It’s not necessary to directly face the radiant because shower meteors appear all over the sky. During the evening, I typically turn my chair to face east-southeast with the radiant off to one side. In the wee hours, with the radiant nearly overhead, I face south instead.

According to the International Meteor Organization (IMO), mass-sorting of debris within the Geminid stream will lead to an abundance of fainter, telescopic meteors about a day prior to visual maximum. If you happen to be out on Dec. 12-13 looking at deep sky objects through your telescope, you might notice a surfeit of faint meteors zipping through the field of view.



Graph of Geminids activity in December 2014 showing a maximum zenithal hourly rate of 253 meteors/hour. Credit: IMO


Graph of Geminids activity in December 2014 showing a maximum zenithal hourly (ZHR) rate of 253 meteors an hour. Observers in the southern hemisphere can also watch the shower, but hourly meteor counts will be much lower (20-30 per hour) because Gemini hunkers low in the northern sky. Credit: IMO
Be sure to watch the IMO Geminid activity website during peak shower activity. Click the live ZHR link and then 2015 Geminids to watch the data flow in from observers around the planet. The IMO invites you to share your observations of the shower by doing a scientific meteor count. Click here for instructions.

Unlike the August Perseids, the Geminid shower is a relative newcomer. It apparently debuted in 1862 when English observer R. P. Greg noticed a new meteor radiant in Gemini active between Dec. 10-12. By the 1870s, more and more astronomers began observing the shower and making counts. Although they “tiptoed in” at first with maxima of 20 meteors per hour in the late 1890s, the shower ramped up to 50 per hour by the 1930s and 80 per hour in the 1970s. Now it’s over a 100.



Time lapse-photo showing geminids over Pendleton, OR. Credit: Thomas W. Earle


Composite image showing Geminids over Pendleton, Oregon. Credit: Thomas W. Earle
Most showers are spawned by bits and pieces of dust and debris that drift away from an active comet to create a stream of orbiting debris. When Earth’s path intersects the stream, dust strikes the atmosphere, heats up and creates a glowing tube of ionized air overhead we call a meteor. The parent of the Geminids was finally tracked down in the 1980s. Surprise! It turned out to be an asteroid — 3200 Phaethon. Debris released by the asteroid, perhaps during its routine close approaches to the Sun, make the Geminids one of only two major showers (the other is the January Quadrantids) to originate from an asteroid.

Consistent and reliable, the Geminid shower is not to miss this year. Clear skies!





About 

I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. Every day the universe offers up something both beautiful and thought-provoking. I also write a daily astronomy blog called Astro Bob.

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Posted by Nelio Inacio at 7:09 AM 0 comments

What Are The Different Parts Of A Volcano?

What Are The Different Parts Of A Volcano?:



Tungurahua volcano. Credit: Patrick Taschler


Tungurahua (“throat of fire”), an active stratovolcano in Ecuador. Credit: Patrick Taschler
Without a doubt, volcanoes are one of the most powerful forces of nature a person can bear witness to. Put simply, they are what results when a massive rupture takes place in the Earth’s crust (or any planetary-mass object), spewing hot lava, volcanic ash, and toxic fumes onto the surface and air. Originating from deep within the Earth’s crust, volcanoes leave a lasting mark on the landscape.

But what are the specific parts of a volcano? Aside from the “volcanic cone” (i.e. the cone-shaped mountain), a volcano has many different parts and layers, most of which are located within the mountainous region or deep within the Earth. As such, any true understanding of their makeup requires that we do a little digging (so to speak!)

While volcanoes come in a number of shapes and sizes, certain common elements can be discerned. The following gives you a general breakdown of a volcanoes specific parts, and what goes into making them such a titanic and awesome natural force.

Magma Chamber: A magma chamber is a large underground pool of molten rock sitting underneath the Earth’s crust. The molten rock in such a chamber is under extreme pressure, which in time can lead to the surrounding rock fracturing, creating outlets for the magma. This, combined with the fact that the magma is less dense than the surrounding mantle, allows it to seep up to the surface through the mantle’s cracks.



Lava cooling after an eruption, Credit: kalapanaculturaltours.com


Lava cooling after an eruption from Kilauea, a shield volcano near Kalapana, Hawaii Credit: kalapanaculturaltours.com
When it reaches the surface, it results in a volcanic eruption. Hence why many volcanoes are located above a magma chamber. Most known magma chambers are located close to the Earth’s surface, usually between 1 km and 10 km deep. In geological terms, this makes them part of the Earth’s crust – which ranges from 5–70 km (~3–44 miles) deep.

Lava: Lava is the silicate rock that is hot enough to be in liquid form, and which is expelled from a volcano during an eruption. The source of the heat that melts the rock is known as geothermal energy – i.e. heat generated within the Earth that is leftover from its formation and the decay of radioactive elements. When lava first erupted from a volcanic vent (see below), it comes out with a temperature of anywhere between 700 to 1,200 °C (1,292 to 2,192 °F). As it makes contact with air and flows downhill, it eventually cools and hardens.

Main Vent: A volcano’s main vent is the weak point in the Earth’s crust where hot magma has been able to rise from the magma chamber and reach the surface. The familiar cone-shape of many volcanoes are an indication of this, the point at which ash, rock and lava ejected during an eruption fall back to Earth around the vent to form a protrusion.

Throat: The uppermost section of the main vent is known as the volcano’s throat. As the entrance to the volcano, it is from here that lava and volcanic ash are ejected.




Thurston lava tube is located on Kilauea in Hawaii. Credit: P. Mouginis-Mark, LPI


Thurston lava tube is located on Kilauea in Hawaii. Credit: P. Mouginis-Mark, LPI
Crater: In addition to cone structures, volcanic activity can also lead to circular depressions (aka. craters) forming in the Earth. A volcanic crater is typically a basin, circular in form, which can be large in radius and sometimes great in depth. In these cases, the lava vent is located at the bottom of the crater. They are formed during certain types of climactic eruptions, where the volcano’s magma chamber empties enough for the area above it to collapse, forming what is known as a caldera.

Pyroclastic Flow: Otherwise known as a pyroclastic density current, a pyroclastic flow refers to a fast-moving current of hot gas and rock that is moving away from a volcano. Such flows can reach speeds of up to 700 km/h (450 mph), with the gas reaching temperatures of about 1,000 °C (1,830 °F). Pyroclastic flows normally hug the ground and travel downhill from their eruption site.

Their speeds depend upon the density of the current, the volcanic output rate, and the gradient of the slope. Given their speed, temperature, and the way they flow downhill, they are one of the greatest dangers associated with volcanic eruptions and are one of the primary causes of damage to structures and the local environment around an eruption site.

Ash Cloud: Volcanic ash consists of small pieces of pulverized rock, minerals and volcanic glass created during a volcanic eruption. These fragments are generally very small, measuring less than 2 mm (0.079 inches) in diameter. This sort of ash forms as a result of volcanic explosions, where dissolved gases in magma expand to the point where the magma shatters and is propelled into the atmosphere. The bits of magma then cool, solidifying into fragments of volcanic rock and glass.



Volcanoes


View of volcanic ash spewing from the Eyjafjallajokull volcano in Iceland. Credit: ©Snaevarr Gudmundsson.
Because of their size and the explosive force with which they are generated, volcanic ash is picked up by winds and dispersed up to several kilometers away from the eruption site. Due to this dispersal, ash an also have a damaging effect on the local environment, which includes negatively affecting human and animal health, disrupting aviation, disrupting infrastructure, and damaging agriculture and water systems. Ash is also produced when magma comes into contact with water, which causes the water to explosively evaporate into steam and for the magma to shatter.

Volcanic Bombs: In addition to ash, volcanic eruptions have also been known to send larger projectiles flying through the air. Known as volcanic bombs, these ejecta are defined as those that measure more than 64mm (2.5 inches) in diameter, and which are formed when a volcano ejects viscous fragments of lava during an eruption. These cool before they hit the ground, are thrown many kilometers from the eruption site, and often acquire aerodynamic shapes (i.e. streamlined in form).

While the term applies to any ejecta larger than a few centimeters, volcanic bombs can sometimes be very large. There have been recorded instances where objects measuring several meters were retrieved hundreds of meters from an eruptions. Small or large, volcanic bombs are a significant volcanic hazard and can often cause serious damage and multiple fatalities, depending on where they land. Luckily, such explosions are rare.

Secondary Vent: On large volcanoes, magma can reach the surface through several different vents. Where they reach the surface of the volcano, they form what is referred to as a secondary vent. Where they are interrupted by accumulated ash and solidified lava, they become what is known as a Dike. And where these intrude between cracks, pool and then crystallize, they form what is called a Sill.



Cross-section through a stratovolcano (vertical scale is exaggerated): 1. Large magma chamber 2. Bedrock 3. Conduit (pipe) 4. Base 5. Sill 6. Dike 7. Layers of ash emitted by the volcano 8. Flank 9. Layers of lava emitted by the volcano 10. Throat 11. Parasitic cone 12. Lava flow 13. Vent 14. Crater 15. Ash cloud MesserWoland


Cross-section of a stratovolcano: 1. Magma chamber 2. Bedrock 3. Vent 4. Base 5. Sill 6. Dike 7. Layers of ash 8. Flank 9. Layers of lava 10. Throat 11. Parasitic cone 12. Lava flow 13. Vent 14. Crater 15. Ash cloud. Credit: MesserWoland
Secondary Cone: Also known as a Parasitic Cone, secondary cones build up around secondary vents that reach the surface on larger volcanoes. As they deposit lava and ash on the exterior, they form a smaller cone, one that resembles a horn on the main cone.

Yes indeed, volcanoes are as powerful as they are dangerous. And yet, without these geological phenomena occasionally breaking through the surface and reigning down fire, smoke, and clouds of ash, the world as we know it would be a very different place. More than likely, it would be a geologically dead one, with no change or evolution in its crust. I think we can all agree that while such a world would be much safer, it would also be painfully boring!

We have written many interesting articles about volcanoes here at Universe Today. Here’s is one about the different types of volcanoes, one about composite volcanoes, and here’s one on the famous volcanic belt, the Pacific “Ring of Fire”.

Astronomy Cast also has a lovely episodes about volcanoes and geology, titled Episode 307: Pacific Ring of Fire and Episode 51: Earth

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.





About 

Matt Williams is the Curator of the Guide to Space for Universe Today, a a regular contributor to HeroX, a science fiction author, and a Taekwon-Do instructor. He lives with his family on Vancouver Island in beautiful BC.

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Posted by Nelio Inacio at 7:08 AM 0 comments

Tuesday, December 8, 2015

MESSENGER Spies a Meteor Shower… on Mercury

MESSENGER Spies a Meteor Shower… on Mercury:



Image credit:


A meteor stream from 2P Encke vs the orbit of Mercury. Image credit: NASA/Goddard, Artist’s concept
Leonid meteor storms. Taurid meteor swarms. Earth is no stranger to meteor showers, that’s for sure. Now, it turns out that the planet Mercury may experience periodic meteor showers as well.

The news of extraterrestrial meteor showers on Mercury came out of the annual Meeting of the Division of Planetary Sciences of the American Astronomical Society currently underway this week in National Harbor, Maryland. The study was carried out by Rosemary Killen of NASA’s Goddard Spaceflight Center, working with Matthew Burger of Morgan State University in Baltimore, Maryland and Apostolos Christou from the Armagh Observatory in Northern Ireland.  The study looked at data from the MErcury Surface Space Environment Geochemistry and Ranging (MESSENGER) spacecraft, which orbited Mercury until late April of this year. Astronomers published the results in the September 28th issue of Geophysical Research Letters.

Micrometeoroid debris litters the ecliptic plane, the result of millions of years of passages of comets through the inner solar system. You can see evidence of this in the band of the zodiacal light visible at dawn or dusk from a dark sky site, and the elusive counter-glow of the gegenschein.



The orbit of comet 2P Encke. Image credit: NASA/JPL


The orbit of comet 2P Encke. Image credit: NASA/JPL
Researchers have tagged meteoroid impacts as a previous source of the tenuous exosphere tails exhibited by otherwise airless worlds such as Mercury. The impacts kick up a detectable wind of calcium particles as Mercury plows through the zodiacal cloud of debris.

“We already knew that impacts were important in producing exospheres,” says Killen in a recent NASA Goddard press release. “What we did not know was the relative importance of comet streams over zodiacal dust.”

This calcium peak, however, posed a mystery to researchers. Namely, the peak was occurring just after perihelion—Mercury orbits the Sun once every 88 Earth days, and travels from 0.31 AU from the Sun at perihelion to 0.47 AU at aphelion—versus an expected calcium peak predicted by researchers just before perihelion.



Image credit:


STEREO A catches sight of comet 2P Encke. Image credit: NASA/STEREO
A key suspect in the calcium meteor spike dilemma came in the way of periodic Comet 2P Encke. Orbiting the Sun every 3.3 years—the shortest orbit of any known periodic comet—2P Encke has made many passages through the inner solar system, more than enough to lay down a dense and stable meteoroid debris stream over the millennia.

With an orbit ranging from a perihelion at 0.3 AU interior to Mercury’s to 4 AU, debris from Encke visits Earth as well in the form of the November Taurid Fireballs currently gracing the night skies of the Earth.

The Encke connection still presented a problem: the cometary stream is closest to the orbit of Mercury about a week later than the observed calcium peak. It was as if the stream had drifted over time…



Image credit:


Comet 2P Encke, captured by NASA’s MESSENGER spacecraft. Image credit: NASA/Johns Hopkins/APL/SW Research Institute
Enter the Poynting-Robertson effect. This is a drag created by solar radiation pressure over time. The push on cometary dust grains thanks to the Poynting-Robertson effect is tiny, but it does add up over time, modifying and moving meteor streams. We see this happening in our own local meteor stream environment, as once great showers such as the late 19th century Andromedids fade into obscurity. The gravitational influence of the planets also plays a role in the evolution of meteor shower streams as well.

Researchers in the study re-ran the model, using MESSENGER data and accounting for the Poynting-Robertson effect. They found the peak of the calcium emissions seen today are consistent with millimeter-sized grains ejected from Comet Encke about 10,000 to 20,000 years ago. That grain size and distribution is important, as bigger, more massive grains result in a smaller drag force.



Image credit: Kevin Palmer


A 2015 Taurid meteor. Image credit: Kevin Palmer
This finding shows the role and mechanism that cometary debris plays in exosphere production on worlds like Mercury.

“Finding that we can move the location of stream to match MESSENGER’s observations is gratifying, but the fact that the shift agrees with what we know about Encke and its stream from independent source makes us confident that the cause-and-effect relationship is real, says Christou in this week’s NASA Goddard press release.



Launched in 2004, MESSENGER arrived at Mercury in March 2011 and orbited the world for over four years, the first spacecraft to do so. MESSENGER mapped the entire surface of Mercury for the first time, and became the first human-made artifact to impact Mercury on April 30th, 2015.

The joint JAXA/ESA mission BepiColombo is the next Mercury mission in the pipeline, set to leave Earth on 2017 for insertion into orbit around Mercury on 2024.

An interesting find on the innermost world, and a fascinating connection between Earth and Mercury via comet 2P Encke and the Taurid Fireballs.





About 

David Dickinson is an Earth science teacher, freelance science writer, retired USAF veteran & backyard astronomer. He currently writes and ponders the universe from Tampa Bay, Florida.

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Posted by Nelio Inacio at 7:15 AM 0 comments

Cosmologist Thinks a Strange Signal May Be Evidence of a Parallel Universe

Cosmologist Thinks a Strange Signal May Be Evidence of a Parallel Universe:



Image Credit: M. Alvarez, R. Kaehler, and T. Abel


A simulation of the early Universe. Credit: M. Alvarez, R. Kaehler, and T. Abel
In the beginning, there was chaos.

Hot, dense, and packed with energetic particles, the early Universe was a turbulent, bustling place. It wasn’t until about 300,000 years after the Big Bang that the nascent cosmic soup had cooled enough for atoms to form and light to travel freely. This landmark event, known as recombination, gave rise to the famous cosmic microwave background (CMB), a signature glow that pervades the entire sky.

Now, a new analysis of this glow suggests the presence of a pronounced bruise in the background — evidence that, sometime around recombination, a parallel universe may have bumped into our own.

Although they are often the stuff of science fiction, parallel universes play a large part in our understanding of the cosmos. According to the theory of eternal inflation, bubble universes apart from our own are theorized to be constantly forming, driven by the energy inherent to space itself.

Like soap bubbles, bubble universes that grow too close to one another can and do stick together, if only for a moment. Such temporary mergers could make it possible for one universe to deposit some of its material into the other, leaving a kind of fingerprint at the point of collision.

Ranga-Ram Chary, a cosmologist at the California Institute of Technology, believes that the CMB is the perfect place to look for such a fingerprint.



This image, the best map ever of the Universe, shows the oldest light in the universe. This glow, left over from the beginning of the cosmos called the cosmic microwave background, shows tiny changes in temperature represented by color. Credit: ESA and the Planck Collaboration.


The cosmic microwave background (CMB), a pervasive glow made of light from the Universe’s infancy, as seen by the Planck satellite in 2013. Tiny deviations in average temperature are represented by color. Credit: ESA and the Planck Collaboration.
After careful analysis of the spectrum of the CMB, Chary found a signal that was about 4500x brighter than it should have been, based on the number of protons and electrons scientists believe existed in the very early Universe. Indeed, this particular signal — an emission line that arose from the formation of atoms during the era of recombination — is more consistent with a Universe whose ratio of matter particles to photons is about 65x greater than our own.

There is a 30% chance that this mysterious signal is just noise, and not really a signal at all; however, it is also possible that it is real, and exists because a parallel universe dumped some of its matter particles into our own Universe.

After all, if additional protons and electrons had been added to our Universe during recombination, more atoms would have formed. More photons would have been emitted during their formation. And the signature line that arose from all of these emissions would be greatly enhanced.

Chary himself is wisely skeptical.

“Unusual claims like evidence for alternate Universes require a very high burden of proof,” he writes.

Indeed, the signature that Chary has isolated may instead be a consequence of incoming light from distant galaxies, or even from clouds of dust surrounding our own galaxy.

SO is this just another case of BICEP2? Only time and further analysis will tell.

Chary has submitted his paper to the Astrophysical Journal. A preprint of the work is available here.





About 

Vanessa earned her bachelor's degree in Astronomy and Physics in 2009 from Wheaton College in Massachusetts. Her credits in astronomy include observing and analyzing eclipsing binary star systems and taking a walk on the theory side as a NSF intern, investigating the expansion of the Universe by analyzing its traces in observations of type 1a supernovae. In her spare time she enjoys writing about astrophysics, cosmology, environmental science, biology, and medicine, making delicious vegetarian meals, taking adventures with her husband and/or Nikon D50, and saving the world. Vanessa is currently a science writer at Brown University.

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MUST READ : Order Of the Planets From The Sun

Order Of the Planets From The Sun:

Planets and other objects in our Solar System. Credit: NASA.


Planets and other objects in our Solar System. Credit: NASA.
Remembering the order of the planets can be a tricky task. With eight celestial bodies, and all the names taken from classical nomenclature, getting them mixed up is a common mistake. First the quick facts: Our Solar System has eight “official” planets which orbit the Sun. Here are the planets listed in order of their distance from the Sun:

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. An easy mnemonic for remembering the order is “My Very Educated Mother Just Served Us Noodles.”

If you add in the dwarf planets, Ceres is located in the asteroid belt between Mars and Jupiter, while the remaining dwarf planets are in the outer Solar System and in order from the Sun are Pluto, Haumea, Makemake, and Eris. There is, as yet, a bit of indecision about the Trans-Neptunian Objects known as Orcus, Quaoar, 2007 O10, and Sedna and their inclusion in the dwarf planet category.

A mnemonic for this list would be “My Very Educated Mother Could Just Serve Us Noodles, Pie, Ham, Muffins, and Eggs” (and Steak, if Sedna is included.) Now, let’s look at a few details including the definition of a planet and a dwarf planet, as well as details about each of the planets in our Solar System.



The Solar System. Image Credit: NASA


Artistic impression of the Solar System, with all known terrestrial planets, as giants, and dwarf planets. Credit: NASA
What is a planet?
In 2006, the International Astronomical Union (IAU) decided on the definition of a planet. The definition states that in our Solar System, a planet is a celestial body which:

  • is in orbit around the Sun,
  • has sufficient mass to assume hydrostatic equilibrium (a nearly round shape),
  • has “cleared the neighborhood” around its orbit.
  • is not a moon.
This means that Pluto, which was considered to be the farthest planet since its discovery in 1930, now is classified as a dwarf planet. The change in the definition came after the discovery three bodies that were all similar to Pluto in terms of size and orbit, (Quaoar in 2002, Sedna in 2003, and Eris in 2005).

With advances in equipment and techniques, astronomers knew that more objects like Pluto would very likely be discovered, and so the number of planets in our Solar System would start growing quickly. It soon became clear that either they all had to be called planets or Pluto and bodies like it would have to be reclassified.



With much controversy then and since, Pluto was reclassified as a dwarf planet in 2006. This also reclassified the asteroid Ceres as a dwarf planet, too, and so the first five recognized dwarf planets are Ceres, Pluto, Eris, Makemake and Haumea. Scientists believe there may be dozens more dwarf planets awaiting discovery.

Later, in 2008, the IAU announced the subcategory of dwarf planets with trans-Neptunian orbits would be known as “plutoids.” Said the IAU, “Plutoids are celestial bodies in orbit around the Sun at a distance greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighborhood around their orbit.”

This subcategory includes Ceres, Pluto, Haumea, Makemake, and Eris.

The Planets in our Solar System:
Having covered the basics of definition and classification, let’s get talking about those celestial bodies in our Solar System that are still classified as planets (sorry Pluto!). Here is a brief look at the eight planets in our Solar System. Included are quick facts and links so you can find out more about each planet.

Mercury:Mercury is the closest planet to our Sun, at just 58 million km (36 million miles) or 0.39 Astronomical Unit (AU) out. But despite its reputation for being sun-baked and molten, it is not the hottest planet in our Solar System (scroll down to find out who that dubious honor goes go!)



Mercury, as imaged by the MESSENGER spacecraft, revealing parts of the never seen by human eyes. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington


Mercury, as imaged by the MESSENGER spacecraft, revealing parts of the never seen by human eyes. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Mercury is also the smallest planet in our Solar System, and is also smaller than its largest moon (Ganymede, which orbits Jupiter). And being equivalent in size to 0.38 Earths, it is just slightly larger than the Earth’s own Moon. But this may have something to do with its incredible density, being composed primarily of rock and iron ore. Here are the planetary facts:

  • Diameter: 4,879 km (3,032 miles)
  • Mass: 3.3011 x 1023 kg (0.055 Earths)
  • Length of Year (Orbit): 87.97 Earth days
  • Length of Day: 59 Earth days.
  • Mercury is a rocky planet, one of the four “terrestrial planets” in our Solar System. Mercury has a solid, cratered surface, and looks much like Earth’s moon.
  • If you weigh 45 kg (100 pounds) on Earth, you would weigh 17 kg (38 pounds) on Mercury.
  • Mercury does not have any moons.
  • Temperatures on Mercury range between -173 to 427 degrees Celcius (-279 to 801 degrees Fahrenheit)
  • Just two spacecraft have visited Mercury: Mariner 10 in 1974-75 and MESSENGER, which flew past Mercury three times before going into orbit around Mercury in 2011 and ended its mission by impacting the surface of Mercury on April 30, 2015. MESSENGER has changed our understanding of this planet, and scientists are still studying the data.
  • Find more details about Mercury at this article on Universe Today, and this page from NASA.
Venus:
Venus is the second closest planet to our Sun, orbiting at an average distance of 108 million km (67 million miles) or 0.72 AU. Venus is often called Earth’s “sister planet,” as it is just a little smaller than Earth. Venus is 81.5% as massive as Earth, and has 90% of its surface area and 86.6% of its volume. The surface gravity, which is 8.87 m/s², is equivalent to 0.904 g – roughly 90% of the Earth standard.



A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL


A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL
And due to its thick atmosphere and proximity to the Sun, it is the Solar Systems hottest planet, with temperatures reaching up to a scorching 735 K (462 °C). To put that in perspective, that’s over four and a half times the amount of heat needed to evaporate water, and about twice as much needed to turn tin into molten metal (231.9 °C)!

  • Diameter: 7,521 miles (12,104 km)
  • Mass: 4.867 x 1024 kg (0.815 Earth mass)
  • Length of Year (Orbit): 225 days
  • Length of day: 243 Earth days
  • Surface temperature: 462 degrees C (864 degrees F)
  • Venus’ thick and toxic atmosphere is made up mostly of carbon dioxide (CO2) and nitrogen (N2), with clouds of sulfuric acid (H2SO4) droplets.
  • Venus has no moons.
  • Venus spins backwards (retrograde rotation), compared to the other planets. This means that the sun rises in the west and sets in the east on Venus.
  • If you weigh 45 kg (100 pounds) on Earth, you would weigh 41 kg (91 pounds) on Venus.
  • Venus is also known and the “morning star” or “evening star” because it is often brighter than any other object in the sky and is usually seen either at dawn or at dusk. Since it is so bright, it has often been mistaken for a UFO!
  • More than 40 spacecraft have explored Venus. The Magellan mission in the early 1990s mapped 98 percent of the planet’s surface. Find out more about all the missions here.
  • Find out more about Venus on this article from Universe Today, and this page from NASA.
Earth:Our home, and the only planet in our Solar System (that we know of) that actively supports life. Our planet is the third from the our Sun, orbiting it at an average distance of 150 million km (93 million miles) from the Sun, or one AU. Given the fact that Earth is where we originated, and has all the necessary prerequisites for supporting life, it should come as no surprise that it is the metric on which all others planets are judged.



Full Earth from Apollo 17


Earth, pictured by the crew of the Apollo 17 mission. Credit: NASA
Whether it is gravity (g), distance (measured in AUs), diameter, mass, density or volume, the units are either expressed in terms of Earth’s own values (with Earth having a value of 1) or in terms of equivalencies – i.e. 0.89 times the size of Earth. Here’s a rundown of the kinds of

  • Diameter: 12,760 km (7,926 miles)
  • Mass: 5.97 x 1024 kg
  • Length of Year (Orbit): 365 days
  • Length of day: 24 hours (more precisely, 23 hours, 56 minutes and 4 seconds.)
  • Surface temperature: Average is about 14 C, (57 F), with ranges from -88 to 58 (min/max) C (-126 to 136 F).
  • Earth is another terrestrial planet with an ever-changing surface, and 70 percent of the Earth’s surface is covered in oceans.
  • Earth has one moon.
  • Earth’s atmosphere is 78% nitrogen, 21% oxygen, and 1% various other gases.
  • Earth is the only world known to harbor life.
  • Find out more about Earth at a series of articles found here on Universe Today, and on this webpage from NASA.
Mars:Mars is the fourth planet from the sun at a distance of about 228 million km (142 million miles) or 1.52 AU. It is also known as “the Red Planet” because of its reddish hue, which is due to the prevalence of iron oxide on its surface. In many ways, Mars is similar to Earth, which can be seen from its similar rotational period and tilt, which in turn produce seasonal cycles that are comparable to our own.



The Planet Mars. Image credit: NASA


Global image of the planet Mars. Credit: NASA
The same holds true for surface features. Like Earth, Mars has many familiar surface features, which include volcanoes, valleys, deserts, and polar ice caps. But beyond these, Mars and Earth have little in common. The Martian atmosphere is too thin and the planet too far from our Sun to sustain warm temperatures, which average 210 K (-63 ºC) and fluctuate considerably.

  • Diameter: 6,787 km, (4,217 miles)
  • Mass: 6.4171 x 1023 kg (0.107 Earths)
  • Length of Year (Orbit): 687 Earth days.
  • Length of day: 24 hours 37 minutes.
  • Surface temperature: Average is about -55 C (-67 F), with ranges of -153 to +20 °C (-225 to +70 °F)
  • Mars is the fourth terrestrial planet in our Solar System. Its rocky surface has been altered by volcanoes, impacts, and atmospheric effects such as dust storms.
  • Mars has a thin atmosphere made up mostly of carbon dioxide (CO2), nitrogen (N2) and argon (Ar).If you weigh 45 kg (100 pounds) on Earth, you would weigh 17 kg (38 pounds) on Mars.
  • Mars has two small moons, Phobos and Deimos.
  • Mars is known as the Red Planet because iron minerals in the Martian soil oxidize, or rust, causing the soil to look red.
  • More than 40 spacecraft have been launched to Mars. You can find out more about missions to Mars here.Find out more about Mars at this series of articles on Universe Today, and at this NASA webpage.
Jupiter:Jupiter is the fifth planet from the Sun, at a distance of about 778 million km (484 million miles) or 5.2 AU. Jupiter is also the most massive planet in our Solar System, being 317 times the mass of Earth, and two and half times larger than all the other planets combined. It is a gas giant, meaning that it is primarily composed of hydrogen and helium, with swirling clouds and other trace gases.



Io and Jupiter as seen by New Horizons during its 2008 flyby. (Credit: NASA/Johns Hopkins University APL/SWRI).


Io and Jupiter as seen by New Horizons during its 2008 flyby. (Credit: NASA/Johns Hopkins University APL/SWRI).
Jupiter’s atmosphere is the most intense in the Solar System. In fact, the combination of incredibly high pressure and coriolis forces produces the most violent storms ever witnessed. Wind speeds of 100 m/s (360 km/h) are common and can reach as high as 620 km/h (385 mph). In addition, Jupiter experiences auroras that are both more intense than Earth’s, and which never stop.

  • Diameter: 428,400 km (88,730 miles)
  • Mass: 1.8986 × 1027 kg (317.8 Earths)
  • Length of Year (Orbit): 11.9 Earth years
  • Length of day: 9.8 Earth hours
  • Temperature: -148 C, (-234 F)
  • Jupiter has 67 known moons, with an additional 17 moons awaiting confirmation of their discovery – for a total of 67 moons. Jupiter is almost like a mini solar system!
  • Jupiter has a faint ring system, discovered in 1979 by the Voyager 1 mission.
  • If you weigh 45 kg (100 pounds) on Earth, you would weigh 115 kg (253) pounds on Jupiter.
  • Jupiter’s Great Red Spot is a gigantic storm (bigger than Earth) that has been raging for hundreds of years. However, it appears to be shrinking in recent years.
  • Many missions have visited Jupiter and its system of moons, with the latest being the Juno mission will arrive at Jupiter in 2016. You can find out more about missions to Jupiter here.
  • Find out more about Jupiter at this series of articles on Universe Today and on this webpage from NASA.


Saturn's relatively thin main rings are about 250,000 km (156,000 miles) in diameter. (Image: NASA/JPL-Caltech/SSI/J. Major)


Saturn’s relatively thin main rings are about 250,000 km (156,000 miles) in diameter. (Image: NASA/JPL-Caltech/SSI/J. Major)
Saturn:Saturn is the sixth planet from the Sun at a distance of about 1.4 billion km (886 million miles) or 9.5 AU. Like Jupiter, it is a gas giant, with layers of gaseous material surrounding a solid core. Saturn is most famous and most easily recognized for its spectacular ring system, which is made of seven rings with several gaps and divisions between them.

  • Diameter: 120,500 km (74,900 miles)
  • Mass: 5.6836 x 1026 kg (95.159 Earths)
  • Length of Year (Orbit): 29.5 Earth years
  • Length of day: 10.7 Earth hours
  • Temperature: -178 C (-288 F)
  • Saturn’s atmosphere is made up mostly of hydrogen (H2) and helium (He).
  • If you weigh 45 kg (100 pounds) on Earth, you would weigh about 48 kg (107 pounds) on Saturn
  • Saturn has 53 known moons with an additional 9 moons awaiting confirmation.
  • Five missions have gone to Saturn. Since 2004, Cassini has been exploring Saturn, its moons and rings. You can out more about missions to Saturn here.
  • Find out more about Saturn at this series of articles on Universe Today and at this webpage from NASA.
Uranus:Uranus is the seventh planet from the sun at a distance of about 2.9 billion km (1.8 billion miles) or 19.19 AU. Though it is classified as a “gas giant”, it is often referred to as an “ice giant” as well, owing to the presence of ammonia, methane, water and hydrocarbons in ice form. The presence of methane ice is also what gives it its bluish appearance.



Uranus as seen by NASA's Voyager 2. Credit: NASA/JPL


Uranus as seen by NASA’s Voyager 2 space probe. Credit: NASA/JPL
Uranus is also the coldest planet in our Solar System, making the term “ice” seem very appropriate! What’s more, its system of moons experience a very odd seasonal cycle, owing to the fact that they orbit Neptune’s equator, and Neptune orbits with its north pole facing directly towards the Sun. This causes all of its moons to experience 42 year periods of day and night.

  • Diameter: 51,120 km (31,763 miles)
  • Mass:
  • Length of Year (Orbit): 84 Earth years
  • Length of day: 18 Earth hours
  • Temperature: -216 C (-357 F)
  • Most of the planet’s mass is made up of a hot dense fluid of “icy” materials – water (H2O), methane (CH4). and ammonia (NH3) – above a small rocky core.
  • Uranus has an atmosphere which is mostly made up of hydrogen (H2) and helium (He), with a small amount of methane (CH4). The methane gives Uranus a blue-green tint.
  • If you weigh 45 kg (100 pounds) on Earth, you would weigh 41 kg (91 pounds) on Uranus.
  • Uranus has 27 moons.
  • Uranus has faint rings; the inner rings are narrow and dark and the outer rings are brightly colored.
  • Voyager 2 is the only spacecraft to have visited Uranus. Find out more about this mission here.
  • You can find out more about Uranus at this series of articles on Universe Today and this webpage from NASA.
Neptune: Neptune is the eighth and farthest planet from the Sun, at a distance of about 4.5 billion km (2.8 billion miles) or 30.07 AU. Like Jupiter, Saturn and Uranus, it is technically a gas giant, though it is more properly classified as an “ice giant” with Uranus.



Neptune photographed by Voyage. Image credit: NASA/JPL


Neptune photographed by the Voyager 2 space probe. Credit: NASA/JPL
Due to its extreme distance from our Sun, Neptune cannot be seen with the naked eye, and only one mission has ever flown close enough to get detailed images of it. Nevertheless, what we know about it indicates that it is similar in many respects to Uranus, consisting of gases, ices, methane ice (which gives its color), and has a series of moons and faint rings.

  • Diameter: 49,530 km (30,775 miles)
  • Mass: 1.0243 x 1026 kg (17 Earths)
  • Length of Year (Orbit): 165 Earth years
  • Length of day: 16 Earth hours
  • Temperature: -214 C (-353 F)
  • Neptune is mostly made of a very thick, very hot combination of water (H2O), ammonia (NH3), and methane (CH4) over a possible heavier, approximately Earth-sized, solid core.
  • Neptune’s atmosphere is made up mostly of hydrogen (H2), helium (He) and methane (CH4).
  • Neptune has 13 confirmed moons and 1 more awaiting official confirmation.
  • Neptune has six rings.
  • If you weigh 45 kg (100 pounds) on Earth, you would weigh 52 kg (114 pounds) on Neptune.
    Neptune was the first planet to be predicted to exist by using math.
  • Voyager 2 is the only spacecraft to have visited Neptune. You can find out more about this mission here.
  • Find out more about Neptune at this series of articles on Universe Today and this NASA webpage. We have written many articles about the planets for Universe Today. Here are some facts about planets, and here’s an article about the names of the planets.If you’d like more info on the Solar System planets, dwarf planets, asteroids and more, check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.We’ve also recorded a series of episodes of Astronomy Cast about every planet in the Solar System. Start here, Episode 49: Mercury.Venus is the second planet from the Sun, and it is the hottest planet in the Solar System due to its thick, toxic atmosphere which has been described as having a “runaway greenhouse effect” on the planet.


Now you know! And if you find yourself unable to remember all the planets in their proper order, just repeat the words, “My Very Educated Mother Just Served Us Noodles.” Of course, the Pie, Ham, Muffins and Eggs are optional, as are any additional courses that might be added in the coming years!

We have many great articles on the Solar System and the planets here at Universe Today. Here is a rundown of the Inner Planets, the Outer Planets, a description of Terrestrial Planets, the Dwarf Planets, and Why Pluto is no Longer a Planet?.

Astronomy Cast also has some cool episodes about the Solar System. Here’s Episode 68: Pluto and the Icy Outer Planets, Episode 306: Accretion Discs, and Episode 159: Planet X.





About 

Matt Williams is the Curator of the Guide to Space for Universe Today, a a regular contributor to HeroX, a science fiction author, and a Taekwon-Do instructor. He lives with his family on Vancouver Island in beautiful BC.

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