Posted on by Matt Williams

How Many Earths Can Fit in Jupiter?

Jupiter compared to Earth. Image credit: NASA

Jupiter is known as the “King of the Planets”, and for good reason. For one, it is the largest planet in the Solar System, and is actually more massive than all the other planets combined. Fittingly, it is named after the king of the Roman pantheon, the latinized version of Zeus (the king of the Olympian gods).

Compare that to Earth, which is the largest of the terrestrial planets, but a tiny marble when compared to the Jovian giant. Because their disparity in size, people often wonder many times over Earth could be squeezed in Jupiter’s massive frame. As it turns out, you could it do many, many times over!

Size and Mass Comparison:

To break the whole size discrepancy down, Jupiter has a mean radius of 69,911 ± 6 km (60217.7 ± 3.7 mi). As already noted, this is roughly 2.5 times the mass of all the planets in the Solar System combined. Compared this to Earth’s mean radius of 6,371.0 km (3,958.8 mi), and you could say that Earth fits into Jupiter almost 11 times over (10.97 to be exact).

Rough visual comparison of Jupiter, Earth, and the Great Red Spot. Approximate scale is 44 km/px. Credit: NASA/Brian0918/ Wikipedia Commons
Rough visual comparison of Jupiter, Earth, and the Great Red Spot. Approximate scale is 44 km/px. Credit: NASA/Brian0918/ Wikipedia Commons

And as already noted, Jupiter is more massive than all the other planets in our Solar System – 2.5 times as massive, that is. In fact, Jupiter weighs in at a hefty 1.8986 × 1027 kg (~4.1857 x 1027 lbs), or 1898.6 billion trillion metric tons (2.092 billion trillion US tons).

Compare that to Earth, which has a mass of 5.97 × 1024 kg (13.1668 × 1024 lb) – 5.97 billion trillion metric tons, or  6.5834 billion trillion US tons. Doing the math, we then come to the conclusion that Jupiter is approximately 317.8 times as massive as Earth.

Volume Comparison:

However, figuring for radius is only useful is you are planning on stacking the Earths end to end across the middle of the gas giant. And comparing their masses doesn’t give you a sense of size, seeing as how the planets are widely different in terms of their density.

Jupiter/Earth comparison. Credit: NASA/SDO/Goddard/Tdadamemd
Jupiter/Earth comparison. Credit: NASA/SDO/Goddard/Tdadamemd

To know how many Earth’s could truly fit inside in three-dimensions, you have to consider total volume, which you can calculate using the simple formula of 4/3 x Pi x radius2.

Doing the math, we find that Jupiter has a volume of 1.43 x 1015 km³ (1,430 trillion cubic km; 343 trillion cubic mi) while Earth has a volume of 1.08 trillion km3 (259 million mi). Divide the one by the other, and you get a value of 1299, meaning you could fit almost 1300 Earth’s inside Jupiter.

In short, the king of the planets is much, much, MUCH bigger than the planet we call home. Someday, if we ever hope to live around Jupiter (i.e. colonize its moons), we will be able to appreciate just how big it is up close. Until then, these impressive figures will have to suffice!

We’ve written many articles about Jupiter for Universe Today. Here’s Ten Interesting Facts About Jupiter, Jupiter Compared to Earth, What is the Diameter of Jupiter?, and How Much Bigger is Jupiter than Earth?

If you’d like more information on Jupiter, check out Hubblesite’s News Releases about Jupiter, and here’s a link to NASA’s Solar System Exploration Guide to Jupiter.

We’ve also recorded an episode of Astronomy Cast just about Jupiter. Listen here, Episode 56: Jupiter.

Sources:

Posted on by Fraser Cain

Which of the Planets is Closest to the Sun?

Mercury as Never Seen Before
Mercury as Never Seen Before

[/caption]
Were you wondering which of the planets is closest to the Sun? The answer is planet Mercury. At an average distance of only 57.9 million km, Mercury orbits closer to the Sun than any other planet.

Just to give you a comparison, Venus orbits the Sun at an average distance of 108.2 million km. And Earth orbits the Sun at an average distance of 149.6 million km. So you can see that Mercury is much closer, taking only 88 days to complete an orbit around the Sun.

So, Mercury is the closest planet to the Sun. And then Venus is the second closest planet to the Sun, and Earth is the third closest planet to the Sun.

The distance of Mercury to the Sun is actually an average. Mercury follows an elliptical orbit around the Sun. Sometimes it’s much closer, and other times it’s much further. At its closest point, called perihelion, Mercury is only 46 million km from the Sun. And then at its most distant point in orbit, called aphelion, Mercury gets out to 69.8 million km from the Sun.

And just for comparison, the planet furthest from the Sun is Neptune, with an average distance of 4.5 billion km from the Sun.

We’ve written many articles about distances in the Solar System. Here’s an article about the distance to the Sun, and here’s an article about how far all the planets are from the Sun.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We’ve also recorded an entire episode of Astronomy Cast all about Mercury. Listen here, Episode 49: Mercury.

Posted on by Fraser Cain

How Many Earths Can Fit in the Sun?

Earth Compared to the Sun. Image credit: NASA
Earth Compared to the Sun. Image credit: NASA

[/caption]
So, how many Earths can fit in the Sun? The answer is that it would take 1.3 million Earths to fill up the Sun. That’s a lot of Earths.

The Sun makes up 99.86% of the mass of the Solar System. And it’s the giant planets like Jupiter and Saturn which make the most of that remaining .14% of the Solar System.

If you’d like to do the calculation yourself, here are your numbers. The volume of the Sun is 1.412 x 1018 km3. And the volume of the Earth is 1.083 x 1012 km3. So if you divide the volume of the Sun by the volume of the Earth, you get 1,300,000.

Of course, the Sun is a fairly average sized stars. There are some enormous stars out there. For example, the red giant Betelgeuse has a radius of 936 times the radius of the Sun. That gives it hundreds of millions of times more volume than the Sun.

And the largest known star is VY Canis Majoris, thought to be between 1800 and 2100 times the radius of the Sun.

We’ve written many articles about size comparisons for Universe Today. Here’s an article about the Moon compared to Earth, and here’s an article about Saturn compared to Earth.

If you’d like more info on the Sun, check out NASA’s Solar System Exploration Guide on the Sun, and here’s a link to the SOHO mission homepage, which has the latest images from the Sun.

We’ve also recorded several episodes of Astronomy Cast about the Sun. Listen here, Episode 30: The Sun, Spots and All.

Posted on by Fraser Cain

What Galaxy is the Earth In?

What galaxy is Earth in? We're in the Milky Way

[/caption]
Were you wondering what galaxy is the Earth in? You’ll probably recognize the answer: it’s the Milky Way Galaxy.

If you go to a dark spot, away from the bright city lights, and look up, you should be able to see the Milky Way as a cloudy band stretching across the sky. It really does look like spilt milk spread across the sky. But if you take a telescope and examine it more closely, you’ll see that the clouds are actually the collective light from thousands of stars.

Since we’re embedded inside the Milky Way, we’re seeing our home galaxy edge-on, from the inside. To get a better idea, grab a dinner plate and take a look at it edge on, so you can’t see the circular shape of the galaxy. You can only see the edge of the plate.

The Milky Way is an example of a barred spiral galaxy. It measures approximately 100,000 light years across and it’s only 1,000 light years thick; although, it’s more thick at the core where the galaxy bulges out. If you could fly out of the Milky Way in a rocket and then look back, you’d see a huge spiral shaped galaxy with a bar at the center. At the ends of this bar, there are two spiral arms which twist out forming the structure of the Milky Way.

The Earth is located in the Solar System, and the Solar System is located about 25,000 light-years away from the core of the galaxy. This also means that we’re about 25,000 light-years away from the outer edge of the Milky Way. We’re located in the Orion Spur, which is a minor arm located in between the two major galactic arms.

If you’d like more information on the Milky Way, check out NASA’s Starchild info on the Milky Way, and here’s more info from the WMAP mission.

We’ve written many articles about the Milky Way for Universe Today. Here’s an article with facts about the Milky Way, and here is a map of the Milky Way.

We’ve also recorded several episodes of Astronomy Cast about the Milky Way. Listen here, Episode 99: The Milky Way.

Posted on by Fraser Cain

How Many Miles to the Center of the Earth?

Earth's core.
Earth's core.

[/caption]
Were you wondering how many miles to the center of the Earth? The simple quick answer is 3,958.8 miles – the mean radius of the Earth in miles. In other words, if you dug a tunnel straight down, you’d reach the center of the Earth after going 3,958.8 miles, and then you’d need to go another 3,958.8 miles to reach the opposite side of the planet.

But wait, if you need to be really precise, the answer depends on where you’re standing on Earth. That’s because the Earth isn’t a perfect sphere. It’s rotating in space, and so it bulges around the middle, while it’s more flattened at the poles. And so, if you’re standing at the poles, you’re only 3,949.9 miles from the center of the Earth. And if you’re standing on the equator, the distance is 3,963.2 miles.

The difference between those two amounts is 13.3 miles. In other words, you would have to dig 13.3 miles further if you were standing on the equator to reach the center of the planet.

This might not sound like much, but it’s actually a pretty big deal. The furthest point from the center of the Earth isn’t Mount Everest. In fact, it’s Mount Chimborazo in Ecuador. Even though it’s shorter than Mount Everest, it’s actually 8,969.8 feet further from the center of the Earth because it’s located near the equator.

We’ve written several articles about the center of the Earth for Universe Today. Here are some interesting facts about the Earth, and here’s an article about the radius of the Earth.

Want to learn more about the interior of the Earth? Check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We have also recorded an episode of Astronomy Cast all about the Earth. Listen here, Episode 51: Earth.

Posted on by Fraser Cain

Tsunami Photos

Tsunami damage along Sumatra northern coasts, Indonesia
Image Credit: Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC

Here are some amazing tsunami photos – at least, the after effects from tsunami impacts on coastlines. You can make any of these images into your computer desktop background. Just click on an image to enlarge it, and then right-click and choose “Set as Desktop Background”.

[/caption]

This is an image of the island of Sumatra after the 2004 tsunami struck, destroying huge portions of the coastline. If you look closely at the photo, you can see how most of the island is green, except for a patch of brown along the western coast.

Deep Ocean Tsunami Waves off the Sri Lankan Coast
Image Credit: NASA/GSFC/LaRC/JPL, MISR Team

This is an image of the southern coast of Sri Lanka, another part of the world ravaged by the 2004 tsunami. This image was taken by NASA’s Terra satellite, showing huge waves just a few kilometers off the coast of the island nation.

Breaking Tsunami Waves along India's Eastern Coast
Image credit:NASA/GSFC/LaRC/JPL, MISR Team

Here’s an image taken by NASA’s Terra satellite showing huge waves breaking off the coast of India. These were generated by the 2004 earthquake off the coast of Indonesia, which traveled across the ocean to strike the coast of India and other countries.

Earthquake off Samoa Generates Tsunami
Image Credit: NASA Earth Observatory image by Robert Simmon, using data from the NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team

This is an image of the island of Samoa, showing the damage caused by a 2009 tsunami. The damaged areas are highlighted in brown.

Camaná, Peru, and Tsunami Vulnerability
Image Credit: Earth Sciences and Image Analysis Laboratory at Johnson Space Center

This is an image of Camaná, in southern Peru, which was struck by a tsunami in 2001. The dotted line shows the part of the town which was inundated by water – waves rose to 8 meters high in some spots.

If you’d like more information about tsunami, check out the NOAA Tsunami website, which has alerts when there are tsunami dangers. And here’s a link to the Pacific Tsunami Warning Center.

We’ve written many articles about tsunami for Universe Today. Here’s a story about a recent earthquake in Chile that generated a tsunami, and here’s an article about the biggest tsunami ever recorded.

We’ve recorded an entire episode of Astronomy Cast all about our home planet. Listen here, Episode 51: Earth.

Posted on by Nicholos Wethington

Newly-Discovered Stellar Nurseries in the Milky Way

The Orion Nebula, one of the most brilliant star-forming regions in our galaxy. Other, newly-discovered regions like the Orion Nebula could help astronomers determing the chemical composition of our galaxy. Image Credit: APOD/Hubble Space Telescope

[/caption]

Our Milky Way churns out about seven new stars per year on average. More massive stars are formed in what’s called H II regions, so-named because the gas present in these stellar nurseries is ionized by the radiation of the young, massive stars forming there. Recently-discovered regions in the Milky Way that are nurseries for massive stars may hold important clues as to the chemical composition and structural makeup of our galaxy.

Thomas Bania, of Boston University, said in an NRAO press release, “We can clearly relate the locations of these star-forming sites to the overall structure of the Galaxy. Further studies will allow us to better understand the process of star formation and to compare the chemical composition of such sites at widely different distances from the Galaxy’s center.”

The announcement of these newly discovered regions was made in a presentation today at the American Astronomical Society meeting in Miami, Florida. The team of astronomers that collaborated on the search includes Thomas Bania of Boston University, Loren Anderson of the Astrophysical Laboratory of Marseille in France, Dana Balser of the National Radio Astronomy Observatory (NRAO), and Robert Rood of the University of Virginia.

H II regions that you may be familiar with include the Orion Nebula (M42), visible just South of Orion’s Belt with the naked eye, and the Horsehead Nebula, so famously imaged by the Hubble Space Telescope. For more information on other known regions (and lots of pictures), visit the 2Micron All-Sky Survey at IPAC.

By studying such regions in other galaxies, and our own, the chemical composition and distribution of a galaxy can be determined. H II regions form out of giant molecular clouds of hydrogen, and remain stable until a collision happens between two clouds, creating a shockwave, or the resulting shockwave from a nearby supernova collapses some of the gas to form stars. As these stars form and start to shine, their radiation strips the molecular hydrogen of its electrons.

The astronomers used both infrared and radio telescopes to see through the thick dust and gas that pervades the Milky Way. By combing surveys taken by the Spitzer Space Telescope’s infrared camera, and the Very Large Array (VLA) radio telescope, they identified “hot spots” that would be good candidates for H II regions. To further verify their findings, they used the Robert C. Byrd Green Bank Telescope (GBT), a sensitive radio telescope that allowed them to detect radio frequencies emitted by electrons as they rejoined protons to form hydrogen. This process of recombination to form hydrogen is a telltale sign of regions that contain ionized hydrogen, or H II.

The location of the regions is concentrated near the ends of the central bar of the Milky Way, and in its spiral arms. Over 25 of the regions discovered were further from the center of the galaxy than our own Sun – a more detailed study of these outlying regions could give astronomers a better understanding of the evolution and composition of our Milky Way.

“There is evidence that the abundance of heavy elements changes with increasing distance from the Galactic center,” Bania said. “We now have many more objects to study and improve our understanding of this effect.”

Source: NRAO Press Release

Posted on by Steve Nerlich

Astronomy Without A Telescope – Stellar Quakes and Glitches

The upper crust of a neutron star is thought to be composed of crystallized iron, may have centimeter high mountains and experiences occasional ‘star quakes’ which may precede what is technically known as a glitch. These glitches and the subsequent post-glitch recovery period may offer some insight into the nature and behavior of the superfluid core of neutron stars.

The events leading up to a neutron star quake go something like this. All neutron stars tend to ‘spin down’ during their life cycle, as their magnetic field applies the brakes to the star’s spin. Magnetars, having particularly powerful magnetic fields, experience more powerful braking.

During this dynamic process, two conflicting forces operate on the geometry of the star. The very rapid spin tends to push out the star’s equator, making it an oblate spheroid. However, the star’s powerful gravity is also working to make the star conform to hydrostatic equilibrium (i.e. a sphere).

Thus, as the star spins down, its crust – which is reportedly 10 billion times the strength of steel – tends to buckle but not break. There may be a process like a tectonic shifting of crustal plates – which create ‘mountains’ only centimeters high, although from a base extending for several kilometres over the star’s surface. This buckling may relieve some of stresses the crust is experiencing – but, as the process continues, the tension builds up and up until it ‘gives’ suddenly.

The sudden collapse of a 10 centimeter high mountain on the surface of a neutron star is considered to be a possible candidate event for the generation of detectable  gravitational waves – although this is yet to be detected. But, even more dramatically, the quake event may be either coupled with – or perhaps even triggered by – a readjustment in the neutron’s stars magnetic field.

It may be that the tectonic shifting of crustal segments works to ‘wind ‘up’ the magnetic lines of force sticking out past the neutron star’s surface. Then, in a star quake event, there is a sudden and powerful energy release – which may be a result of the star’s magnetic field dropping to a lower energy level, as the star’s geometry readjusts itself. This energy release involves a huge flash of x and gamma rays.

In the case of a magnetar-type neutron star, this flash can outshine most other x-ray sources in the universe. Magnetar flashes also pump out substantial gamma rays – although these are referred to as soft gamma ray (SGR) emissions to distinguish them from more energetic gamma ray bursts (GRB) resulting from a range of other phenomena in the universe.

However, ‘soft’ is a bit of a misnomer as either burst type will kill you just as effectively if you are close enough. The magnetar SGR 1806-20 had one of largest (SGR) events on record in December 2004.

Along with the quake and the radiation burst, neutron stars may also experience a glitch – which is a sudden and temporary increase in the neutron star’s spin. This is partly a result of conservation of angular momentum as the star’s equator sucks itself in a bit (the old ‘skater pulls arms in’ analogy), but mathematical modeling suggests that this may not be sufficient to fully account for the temporary ‘spin up’ associated with a neutron star glitch.

Theoretical model of a neutron star's interior. An iron crystal core overlies a region of neutron-enriched atoms, below which is the degenerate matter of the core - where sub-atomic particles are stretched and twisted by magnetic and gravitational forces. Credit: Université Libre de Bruxelles (ULB).

González-Romero and Blázquez-Salcedo have proposed that an internal readjustment in the thermodynamics of the superfluid core may also play a role here, where the initial glitch heats the core and the post-glitch period involves the core and the crust achieving a new thermal equilibrium – at least until the next glitch.

Posted on by Tammy Plotner

Weekend SkyWatcher’s Forecast – May 21-23, 2010

Greetings, fellow SkyWatchers… Are you enjoying the typical “change of seasons” weather in your area? If skies should clear for you this weekend, we have some very nice lunar challenges along with some very interesting stars! Why not spend a little time contemplating lunacy and gathering a few photons? When ever you are ready, I’ll see you in the back yard…

May 21, 2010 – Today we’d like to wish a happy birthday to Nils Christofer Duner. Born in 1839, this classical astronomer studied the rotational period of the Sun. Duner was an outstanding observer and made 2,679 measurements of 445 double and multiple stars. He also specialized in observing the spectra of red stars, and later made a series of measurements of the Doppler shift caused by solar rotation. As you know, one of our own Sun’s main ingredients is helium. If you would like to see a helium-rich star, look no further tonight than Alpha Virginis See Spica— Spica . As the 16th brightest star in the sky, this brilliant blue-white ‘‘youngster’’ appears to be about 275 light-years away and is about 2,300 times brighter than our own Sun. Although we cannot see it visually, Spica is a double star. Its spectroscopic companion is roughly half its size and is also helium rich.

Now, let’s have a look at the Moon! Tonight’s challenges are craters Cassini and Cassini A, which come into view just south of the black slash of the Alpine Valley.


The major crater spans 57 kilometers and reaches a floor depth of 1,240 meters. Your assignment, should you decide to accept it, is to spot the central crater A. It only spans 17 kilometers, yet drops down another 2,830 meters below the primary crater’s floor!

May 22, 2010 – Let’s begin the day by honoring the 1920 birth on this date of Thomas Gold, an astronomer known for
proposing the ‘‘steady-state’’ theory of the universe; for explaining pulsars; and for giving the magnetosphere its name. Gold was also an auditory research genius. In his interview with D.T. Kemp he stated: ‘‘I’m a compulsive thinker, I never turn my brain off, I’ve never in my life complained of being bored because I’m constantly thinking about some problem, mostly physics I suppose. A problem is always on my mind—evidently even in my sleep because I often wake up with a solution clearly spread out.’’

Tonight let’s take a long Moonwalk together and do some major crater exploration. Try using mid-range magnification in your telescope and see how many of the features you can identify:


(1) Sinus Asperitatis, (2) Theophilus, (3) Cyrillus, (4) Catharina, (5) Rupes Altai, (6) Piccolomini, (7) Sacrobosco, (8) Abulfeda, (9) Almanon, (10) Taylor, (11) Abenezra, (12) Apianus, (13) Playfair, (14) Aliacensis, (15) Werner, (16) Blanchinus, (17) Lacaille, (18) Walter, (19) Regiomontanus, (20) Purbach, (21) Thebit, (22) Arzachel, (23) Alphonsus, (24) Ptolemaeus, and (25) Albategnius.

May 23, 2010 – If you like to venture to the lunar surface tonight, we can enjoy a strange, thin feature that’s a nice challenge! Look toward the lunar south, where you will note the prominent rings of craters Ptolemaeus, Alphonsus, Arzachel, Purbach, and Walter descending from north to south. Just west of them, you’ll see the emerging Mare Nubium.


Between Purbach and Walter, you will see the small, bright ring of Thebit, with a crater caught on its edge. Look further west to spot a long, thin, dark feature cutting across the mare. Its name? Rupes Recta , better known as the ‘‘Straight Wall,’’ or sometimes Rima Birt. The Straight Wall is one of the steepest known lunar slopes, rising around 366 meters from the surface at a 41 degree angle. Be sure to mark your lunar challenge notes and visit this feature again!

If you’d like to take a look at a ‘‘habitable zone,’’ look no further than AX Microscopii (RA21 17 15 Dec – 38 52 02). AX is a dwarf red flare star, which resides only 12.9 light-years from us. Although it might not seem that important, it is the target of interferometric studies searching for planets that may have formed in habitable zones around stars similar to our own. Even though AX is slightly smaller than Sol, this cool main sequence star might in fact be inhospitable, due to its daily flare activity.

Until next week? Ask for the Moon… But keep on reaching for the stars!

This week’s awesome images (in order of appearance) are: Cassini – courtesy of Wes Higgins, Thomas Gold (archival image), Lunar Photo courtesy of Greg Konkel – Annotations by Tammy Plotner, Rupes Recta courtesy of Damien Peach and AX Microscopi was done by Palomar Observatory, courtesy of Caltech. We thank you so much!