Posted on by Fraser Cain

Does Earth Have Rings?

If you’re talking about majestic ice rings, like we see around Saturn, Uranus or Jupiter, then no, Earth doesn’t have rings, and probably never did. If there was any ring of dust orbiting the planet, we’d see it.

It’s possible that there were rings orbiting Earth in the past. Some scientists think that Earth’s gravity could have broken up a comet or asteroid that got too close to the planet, but didn’t actually collide. This is similar to what happened to Comet Shoemaker/Levy 9 that eventually crashed into Jupiter. First the giant planet tore the comet up, and then the pieces crashed into the planet on a later orbit.

In the case of Earth, it might have held onto a few ice particles that would have then orbited the planet, and eventually crashed through our atmosphere and burned up. Even the smallest particles of ice or dust create spectacular meteors in the sky, so there was a ring right now, we’d see these impacts all the time.

Other scientists think that a giant asteroid impact with Earth, such as the one the killed the dinosaurs 65 million years ago, might have kicked up a huge ring of debris around the planet. This ring would cast a shadow down on the surface of the Earth, changing the planet’s climate, and could last for a few million years at most.

Finally, humans have put up an artificial ring in the past. The US Military launched 480 million copper needles into orbit around Earth in a project called Project West Ford. Scientists could bounce radio signals off the needles and communicate between two locations on Earth. This worked for a few months after launch, until the needles were too far dispersed to allow for communication. In theory, if needles were continuously launched, it would be a functioning communications system, but it’s not necessary with modern communications satellites.

So Earth probably did have temporary rings in the past after asteroid impacts or cometary flybys, but Earth doesn’t have rings today.

Posted on by Fraser Cain

Mass of the Earth

The Earth has a mass of 5.97×1024 kg.

You can also check out these books about the planet Earth from Amazon.com for more detailed information.

If you could actually break up the planet into its various parts, you’d get 32% iron, 30% oxygen, 15% silicon, 14% magnesium, and then all the other elements, with sulfur, nickel, calcium and aluminum being the most common.

The density of Earth is 5.5 g/cm3. This is actually the densest planet in the Solar System; however, this is partly because of the size of Earth. The next most dense planet is Mercury, and it would actually be more dense than Earth if it wasn’t so small. Earth pulls at itself with so much gravity, that it compacts down tighter than Mercury.

How did scientists find out the mass of Earth? By studying how things fall towards it. Gravity is created from mass. The more mass an object has, the more gravity it will pull with. If you can calculate how an object is being accelerated by the gravity of an object, like Earth, you can determine its mass.

In fact, astronomers didn’t accurately know the mass of Mercury or Venus until they finally put spacecraft into orbit around them. They had rough estimates, but once there were orbiting spacecraft, they could make the final mass calculations. We know the mass of Pluto because we can calculate the orbit of its moon Charon.

Posted on by Jerry Coffey

What is Jupiter Made Of?

Damian Peach reprocessed one of the latest images taken by Juno's JunoCam during its 3rd close flyby of the planet on Dec. 11. The photo highlights two large 'pearls' or storms in Jupiter's atmosphere. Credit: NASA/JPL-Caltech/SwRI/MSSS

Of all the Jovian related questions that we get here at Universe Today, what is Jupiter made of is one of the most common. Jupiter is mainly composed of hydrogen and helium just like a star. Answering that question seems to open a flood of other questions about the gas giant, so here are some facts about Jupiter that should answer quite a few of them.

Jupiter does not have enough mass to ignite fusion and become a star like our Sun. Without that mass, Jupiter is also too cold for fusion. If Jupiter were to become 80 times more massive it would be able to generate enough heat for fusion through gravitational compression. Given that there isn’t that much mass in our Solar System, outside of the Sun, it is impossible for Jupiter to become a star. Can you imagine how scorched and barren all of the planets would be if ours was a binary star system?

Spectral analysis of Jupiter has revealed that in addition to hydrogen and helium, the planet is made of water, methane and ammonia. Those elements are in trace amounts. The core of the planet is thought to contain some rock and metallic hydrogen. Scientists estimate that the core is heated to 36,000 K. The planet is not just a ball of gas that you would be able to drop straight through. In addition to the rocky/molten metallic hydrogen core, there is a layer of liquid hydrogen and helium and areas where the hydrogen is in a supercritical state, meaning that it does not have distinct gas and liquid phases.

Another frequent question about Jupiter is about the ”stripes” that can be seen. Those stripes are actually an effect of the fast rotation of the planet. To be more specific, they are due to the combination of the planet’s rotation and that its gases are more intensely heated at the equator than the poles. This is similar to why the Earth has trade winds near the equator and jet streams near the poles…rising air interacts with the coriolis effect of the rotation and causes sideways deflections. Jupiter rotates much faster and has a thicker atmosphere, so its coriolis effect is much stronger, thus the stripes. Try this link for a more in depth explanation of the striations(stripes).

Just asking what is Jupiter made of only brings up a whole other set of questions. Be sure to keep looking and you will find plenty to stump your friends and teachers with.

We have written many articles about Jupiter for Universe Today. Here’s an article about the color of Jupiter, and here’s an article about the missions to Jupiter.

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 Jerry Coffey

How Did Jupiter Get its Name?

Jupiter and moon Io (NASA)

Jupiter has been known since very ancient times, so how did Jupiter get its name? While it had many names throughout history, the Roman empire had the greatest influence over a wide portion of modern society, so the names accorded to planets by the Romans still hold sway over astronomy. The Romans named the planet after their king of gods, Jupiter, who was also the god of the sky and of thunder. Why choose to name the planet Jupiter? It was the largest object in the sky; therefore the most powerful; therefore Jupiter.

In the Roman pantheon, Jupiter began as the sky god, concerned mainly with wine festivals and associated with the sacred oak of the Capitol. Eventually, he was attributed the spoils of war and became a god of war. It was believed that he caused the armies to stand strong and be victorious. He was the main witness in all oaths. Jupiter was the central god in the Capitoline Triad along with Juno and Minerva. He remained Rome’s chief official deity throughout the Republican and Imperial eras, until the pagan system was replaced by Christianity. Jupiter granted Rome supremacy because he was ”the fount of the auspices upon which the relationship of the city with the gods rested”. He personified the divine authority of Rome’s highest offices, internal organization, and external relations: his image in the Republican and Imperial Capitol bore regalia associated with Rome’s ancient kings and the highest consular and Imperial honors. Roman consuls swore their oath of office in Jupiter’s name. To thank him for his help, and to secure his continued support, they offered him a white, castrated ox with gilded horns.

It is common practice for a planet, moon, and many other celestial bodies to get their names from Greek or Roman mythology as well as derive their astronomical symbol from that particular personality. Some examples are Neptune the God of the Sea, Mars the God of War, Mercury the Messenger, Saturn the God of Time and father of Jupiter, Uranus the father of Saturn, Venus the Goddess of Love, and Earth, well, Earth is the only planet to buck the Greco-Roman tradition.

The answer to how did Jupiter get its name is very simple. If you delve into the planet much deeper, you will find that the planet itself is a mystery that scientists are still trying to unravel.

We have written many articles about Jupiter for Universe Today. Here’s an article about how long it takes to get to Jupiter, and here’s an article about the temperature of Jupiter.

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:
NASA Solar System Exploration Guide
NASA StarChild

Posted on by Fraser Cain

The Difference Between Reflectors and Refractors

When you choose a telescope, there are two main kinds you can pick from, reflectors and refractors. Both can be wonderful for viewing the night sky. They use basically different methods to boost light from dim objects in the sky. Here’s how they work, and how they’re different.

Refractor Telescopes
Here’s what’s inside a basic refractor telescope. The job of the objective lens, opposite the eyepiece end, is to gather the light coming from a distant object, such as a star, and bend it into a single point of focus. A second lens’ (the eyepiece) job is to enlarge that focused image for our retina; it acts as a magnifying glass. Think of the focused light coming in from the first lens as a bug, and think of the eyepiece magnifier as a basic magnifying glass that we look at the bug with. That’s it in a nutshell.


Reflector Telescopes
A reflector telescope uses two mirrors instead of two lenses. Isaac Newton developed this telescope to combat chromatic aberration (a rainbow seen around some objects viewed with a refractor telescope). A mirror used to gather light doesn’t suffer from this effect. Light from an object enters the telescope tube and is reflected off a curved mirror at the end of the tube. A second, small, flat mirror in the middle of the tube reflects this image to the eyepiece. There are potential problems associated with the mirrors. Firstly, some light is always lost in the reflection; good quality telescopes can usually gather 90% of the light coming in. Secondly, the mirror might not be a perfect curve, so the image being reflected will not come to a perfect point. This results in a dragging effect; a point could be seen as a line or cross. Also, the mirrors need to be cleaned and realigned from time to time.
Posted on by Fraser Cain

What are Telescopes?

This artist’s rendering shows the Extremely Large Telescope in operation on Cerro Armazones in northern Chile. The telescope is shown using lasers to create artificial stars high in the atmosphere. Image: ESO/E-ELT
This artist’s rendering shows the Extremely Large Telescope in operation on Cerro Armazones in northern Chile. The telescope is shown using lasers to create artificial stars high in the atmosphere. Image: ESO/E-ELT

Early theories of the Universe were limited by the lack of telescopes. Many of modern astronomy’s findings would never have been made if it weren’t for Galileo Galilei’s discovery. Pirates and sea captains carried some of the first telescopes: they were simple spyglasses that only magnified your vision about four times and had a very narrow field of view. Today’s telescopes are huge arrays that can view entire quadrants of space. Galileo could never have imagined what he had set into motion.

Here are a few facts about telescopes and below that is a set of links to a plethora of information about them here on Universe Today.

Galileo’s first telescopes were simple arrangements of glass lenses that only magnified to a power of eight, but in less than two years he had improved his invention to 30 power telescope that allowed him to view Jupiter. His discovery is the basis for the modern refractor telescope.

There are two basic types of optical telescopes; reflector and refractor. Both magnify distant light, but in different ways. There is a link below that describes exactly how they differ.

Modern astronomer’s have a wide array of telescopes to make use of. There are optical observation decks all around the world. In addition to those there are radio telescopes, space telescopes, and on and on. Each has a specific purpose within astronomy. Everything you need to know about telescopes is contained in the links below, including how to build your own simple telescope.

Posted on by Nancy Atkinson

Caught in the Act: Astronomers See Supernova As it Explodes

First supernova caught in the act (Alicia Soderberg, Princeton University)

The Swift satellite has made another fortuitous observation. This time, and for the first time ever, astronomers have caught a star in the act of going supernova. These stellar explosions have been observed before, but always after the fireworks were well underway. “For years we have dreamed of seeing a star just as it was exploding, but actually finding one is a once-in-a-lifetime event,” says Alicia Soderberg, from Princeton University, who is leading the international group studying this explosion. “This newly born supernova is going to be the Rosetta Stone of supernova studies for years to come.”

In January of 2008 Soderberg was expecting to study a month-old supernova that was already underway. But as she and her assistant studied the X-ray emissions conveyed from space by NASA’s Swift satellite, they saw an extremely bright light that seemed to jump out of the sky. They didn’t know it at the time, but they had just become the first astronomers to have caught a star in the act of exploding.

“In the old days — last year — people found supernovae by their optical light and then started to study them to understand which stars blow up, what the mechanism is and what they produce,” said Robert Kirshner, a professor of astronomy at Harvard University. “But this is something new — the X-rays come right at the beginning and provide a very early alert to the event.”

Soderberg regards the discovery as a case of extreme serendipity. The satellite was pointing in the right place at the right time, she said, because she had asked Neil Gehrels, Swift’s lead scientist at NASA’s Goddard Space Flight Center to turn it that way to look at another supernova. And while she was away lecturing, she had asked her colleague, Edo Berger, to keep an eye on the data for her.

“It’s a really lucky chain of events — a surprise,” said Soderberg, who is leading the group studying the explosion. “It was all over in a matter of minutes.”

Other observatories also turned their telescopes toward this stellar explosion, making detailed observations of the event, including the Hubble Space Telescope, the Chandra X-ray Observatory, Palomar’s 60- and 200-nch telescopes, the Gemini Observatory and Kitt 1 Telescope in Hawaii, and the Very Large Array and Apache Point Observatories in New Mexico. This will allow a very detailed study of this event.

A typical supernova occurs when the core of a massive star runs out of nuclear fuel and collapses under its own gravity to form an ultradense object known as a neutron star. The newborn neutron star compresses and then rebounds, triggering a shock wave that plows through the star’s gaseous outer layers and blows the star to smithereens. Until now, astronomers have only been able to observe supernovae brightening days or weeks after the event, when the expanding shell of debris is energized by the decay of radioactive elements forged in the explosion.

Original News Source: Princeton University Press release

Posted on by Nancy Atkinson

Spaceship Sighting Alert

The next few evenings will provide excellent opportunities for observing the International Space Station in the night skies above both Europe and North America. Beginning this evening, May 21 through May 23 the ISS will pass over from two to four times per night, depending on your location. Because of the station’s current orientation and flight path, it will be highlighted almost constantly by sunlight as it flies over these continents, and thus visible to Earthlings below. If you’ve never had the opportunity to see the space station fly over your backyard, this is a great chance to do so, given your specific area is free from cloud cover. And for those of you that have seen the ISS before, you know what a spectacular (and sometimes spine-tingling) sight it is. It’s unusual to get such a clear view of the ISS across such a wide spectrum of countries. And how, you ask, can you find out when the station will be flying over your house?

There are a couple of different websites that provide real-time tracking data and information about the ISS sighting opportunities. NASA has a Quick and Easy Sightings by City site, where you just search for your country and city which provides local times and the location in the sky where the station will be visible.

The European Space Agency also provides their ISS: Where Is It Now site that also allows you to select your country and city to find the station’s location.

The Heaven’s Above website (which also powers ESA’s site) is also an excellent site to find out when the ISS, as well as all sorts of other satellites and other heavenly sights will be visible. At Heaven’s Above, you can plug in your exact latitude and longitude, so if you live in a remote area, you’ll be able to have exact times and locations to look for satellites instead of relying on information for the nearest city.

So take this great chance to see our orbiting outpost. If you have a strong enough and tracking-capable telescope you might even be able to spot specific modules on the station, or the solar arrays. The Astrospider site has some images and movies available of what this looks like.

And this is a great opportunity to inspire a child about the wonders of space exploration and astronomy.

For more information about the ISS.

Posted on by Nancy Atkinson

Spare Telescope Parts Could be Used for Homeland Security

The life of NASA’s Compton Gamma Ray Observatory (CGRO) ended in 2000 when the spacecraft’s remains splashed down in the Pacific Ocean after a planned deorbit. But the space telescope’s spare parts live on, and they may have a new job. Instead of searching the universe for radioactive emissions, they could help military personnel search for dirty bombs and other radioactive materials. “If we can detect radioactive aluminum-26 on the other side of the galaxy we can find other radioactive materials like cesium-137 or cobalt-60 inside a building or on the other side of the street by the same method,” said Dr. James Ryan from the University of New Hampshire.

Ryan was a member of the research team that helped build and operate the gamma-ray imaging COMPTEL telescope onboard the CRGO, a 1991-2000 NASA mission. One of the key findings of COMPTEL was its map of radioactive aluminum from dying stars throughout the Galaxy.

Identical flight spares of all the telescope components were built, just in case any of the parts failed. While the spares were never launched, they haven’t been collecting dust on a shelf. At different times, Ryan told Universe Today, the flight spares were assembled into a working telescope, sometimes as a student exercise and once for the benefit of the US Army as a test for probing the interior of buildings based on the background gamma radiation being emitted from the contents of the building.

“It is a sensitive instrument and it required no great thought to envision this use for it,” Ryan said of his idea to use the parts to pinpoint the location of dirty bombs. He was motivated by witnessing a National Guard drill to search for and clean up radioactive material left over by “terrorists.”

“It was clear that we would be able to sense the presence and approximate location of the radioactive material without entering the building with this device,” he said.

The device, known as GRETA, short for the Gamma-ray Experimental Telescope Assembly, could potentially be loaded on a truck and used for homeland security work such as scanning shipping containers or buildings for radioactive materials.

GRETA can accurately determine the direction from which a radioactive source is being emitted by creating an image, unlike current technology used by the military, such as Geiger counters or spectrometers that can only determine that radiation in is the vicinity.

“They might detect the presence of cesium-137 but they won’t know where it is unless they get right up close to it, they would have to fish around inside the building,” said Ryan, which would be a safety issue for military personnel.

Other media outlets report that some scientists doubt the applicability of this technology, saying GRETA’s “older” design has its limitations. But Ryan told Universe Today that current technology has changed very little from what COMPTEL, and GRETA, employ.

“Few, if any, scintillator detectors today will perform better than what is in GRETA,” he said. “There are newer designs for gamma-ray telescopes under development, but they are far from a deployable state. All are expensive, far more than a GRETA-type instrument. In fact, one could argue that GRETA is optimized for this application, because it provides the sensitivity necessary for the imaging and spectroscopy, while still remaining affordable and deployable on a short time scale.”

While GRETA is a prototype, the blueprints for the detectors, electronics and operation software still exist and can be used, with little modification, to build up a commercial unit for a real field test.

Ryan said there could be several potential “customers” or users for this device. “The National Guard is an obvious one, because they are charged with the clean up and disposal problem if, and when, a terrorist cell is uprooted. The US Border Patrol, various branches of the military and different port authorities could all find this useful,” Ryan said.

More information about CGRO.

Posted on by Nancy Atkinson

There’s A lot of Dust Out There in the Universe

The whole point of putting telescopes in orbit is to avoid distortions caused by our murky atmosphere. But now astronomers say they have calculated only half the light of our universe reaches telescopes, even those in orbit, because of the amount of dust that permeates the universe. In essence, they say, the universe is twice as bright as previously thought. The lead author of a new paper detailing this discovery, Dr. Simon Driver from the University of St Andrews said, “For nearly two decades we’ve argued about whether the light that we see from distant galaxies tells the whole story or not. It doesn’t; in fact only half the energy produced by stars actually reaches our telescopes directly, the rest is blocked by dust grains.”

While astronomers knew the universe contains small grains of dust, they hadn’t realized the extent to which this is restricting the amount of light that we can see. The dust absorbs starlight and re-emits it, making it glow. They knew that existing models were flawed, because the energy output from glowing dust appeared to be greater than the total energy produced by the stars.

Dr. Driver said, “You can’t get more energy out than you put in so we knew something was very wrong. Even so, the scale of the dust problem has come as a shock – it appears that galaxies generate twice as much starlight as previously thought.”

The team used a new model of the dust distribution in galaxies from a catalogue of 10,000 galaxies to precisely calculate the fraction of starlight blocked by the dust. The team says dust blocks approximately half of the light that the Universe generates.

The Universe is currently generating energy, via nuclear fusion in the cores of stars, at a whopping rate of 5 quadrillion Watts per cubic light year, about 300 times the average energy consumption of the Earth’ population.

After measuring the brightness of thousands of disc-shaped galaxies with different orientations, the astronomers matched their observations to computer models of dusty galaxies. From this they were able to calibrate the models and, for the first time, determine how much light is obscured when a galaxy has a face-on orientation. This then allowed them to determine the absolute fraction of light that escapes in each direction from a galaxy.

While modern instruments allow astronomers to see further into space, they can’t eliminate the obscuring effect from these tiny dust grains. “It is somewhat poetic that in order to discover the full glory of our Universe we first had to appreciate the very small” said Dr. Alister Graham from the Swinburne University of Technology.

The team consists of astronomers from the United Kingdom, Germany and Austrailia. Their research was published in the May 10 issue of Astrophysical Journal Letters.

Original News Source: Science and Technology Facilities Council