Universe Today

July 8, 2008December 24, 2015 by Fraser Cain

What is the Second Smallest Planet in the Solar System?

Pluto used to be the smallest planet, but it’s not a planet any more. That makes Mercury the smallest planet in the Solar System. The second smallest planet in the Solar System is Mars, measuring 6792 km across.

With all the focus and exploration of Mars, you’d think it’s a really big planet, but actually it’s pretty small. Mars has only 53% the diameter of Earth, and about 1/10th the mass. It only has 15% the volume of Earth. In other words, you could fit 6 planets the size of Mars into Earth, and still have room to spare.

Since Mars is relatively small compared to Earth, and it has a fraction of our planet’s mass, the force of gravity on Mars is very low. If you could walk on the surface of Mars, you would experience only 38% the force of gravity you feel pulling you down on Earth. In other words, if you weighed 100 kg on Earth, you’d feel like you only weighed 38 kg on Mars.

Mars is so small that its core cooled down billions of years ago, and so it doesn’t have a magnetic field any more. Earth’s magnetic field helps push away the Sun’s solar wind, which is trying to carry away our atmosphere. When you match this with its very low amount of gravity, and Mars has lost almost all its atmosphere. The pressure of the atmosphere on Mars is 1% what we experience on Earth.

Here’s an article that explains why Pluto isn’t a planet any more. And here’s the smallest planet in the Solar System.

Want more information? Here’s another article about the biggest planet in the Solar System, and the smallest planet in the Solar System.

We have recorded a whole series of podcasts about the Solar System at Astronomy Cast. Check them out here.

July 8, 2008December 24, 2015 by Nancy Atkinson

The Yin and Yang of the NeXT Spacecraft

Hard and soft. Dark and bright. High and low. Wide and thin. JAXA and NASA. And that’s just one spacecraft. Japan’s space agency, JAXA and NASA are teaming up to create a new spacecraft to study the extreme environments of the universe. NeXT, which stands for New exploration X-Ray Telescope is a next generation x-ray astronomy satellite currently under development, with launch scheduled in 2013. While Japan will provide the main spacecraft and several instruments, NASA, and in particular the Goddard Space Flight Center just announced they will be adding a new instrument to the spacecraft, the High-Resolution Soft X-Ray Spectrometer (SXS). While the spacecraft’s main instrument will be its Hard X-ray Telescope (HXTs) the addition of SXS is just one of several complementary instruments that provide a “yin and yang” aspect to NeXT’s explorations, which hope to reveal new facets of the universe.

The concept of yin and yang involves two opposing, but at the same time, complementary aspects of any one phenomenon, or comparison of any two phenomena. NeXT will employ both those aspects. With the addition of NASA’s SXS, NeXT will be observing both so-called “hard” and “soft” x-rays. Hard x-rays are the highest energy x-rays, typically having energies greater than 10,000 electron volts (or 10 keV) while the lower energy x-rays are referred to as soft x-rays, which have less energy and longer wavelengths. Different types of instruments are needed to detect each kind.

Conventional X-ray mirrors usually can just concentrate on only soft X-rays up to 10 keV. NeXT’s HXTs will use a “super mirror” which has a multi-layer coating on the reflecting surface in order to observe hard X-rays. The mission designers plan to utilize this technique to extend the energy band of the X-ray mirrors by nearly an order of magnitude. Observation of hard X-rays will enable the study of the various acceleration phenomena in the universe, such as dark energy, cosmic rays and supernova remnants, which astronomers say can never be completely understood through the observations of the thermal phenomena below 10 keV.

We have known for some time that cosmic X-rays are accelerated by supernova remnants. But some cosmic X-rays have energy levels so high that they cannot possibly come from a supernova remnant. These high-energy or hard cosmic X-rays may have been created when galaxy clusters evolved. According to this theory, when the galaxy clusters, which were small at first, were colliding and merging into large ones, shock waves were created, which greatly accelerated the particles. NeXT, may confirm or refute this theory.

NeXT will have both a soft x-ray telescope and soft x-ray spectrometer. With these instruments, the spacecraft can investigate the nature of dark matter on large scales in the universe, and can also explore how bright galaxies and clusters of galaxies form and evolve.

“We are thrilled to have the opportunity to create a powerful new x-ray spectrometer that will open up a whole new realm in high energy astrophysics in collaboration with our partners in Japan,” said Richard L. Kelley, the Principal Investigator for the SXS mission at Goddard. We have a great team in place that is anxiously waiting to start work.”

To compliment the x-ray telescopes there will also be Wide-band X-ray Imagers (WXI) to cover a wide energy range. Because it is difficult to cover such a wide energy range with a single detector, NeXT will use a hybrid detector, which consists of an upper-stage, soft X-ray detector and a lower-stage, hard X-ray detector. It will use thinned X-ray CCDs (charged coupled devices) for the upper stage, which stop only the soft X-rays and and a CdTe (cadmium telluride) pixel detector for the lower stage.

Also in the suite of instruments is a Soft Gamma-ray detector (SGD), which is still under development. It will include an ultra-low background, high-sensitivity detector in soft gamma-ray band by combining an active shield and an pixel detector.

Charles Gay, deputy associate administrator for NASA’s Science Mission Directorate in Washington said missions like SXS and NeXT “expand NASA’s science through partnerships with international and commercial organizations,” – just another complimentary aspect of a mission full of yin and yang.

Original News Source: NASA,

July 8, 2008December 24, 2015 by Fraser Cain

What is the Second Biggest Planet in the Solar System?

Saturn captured by Voyager. Image credit: NASA/JPL

The biggest planet in the Solar System is Jupiter. But the title for the second biggest planet in our Solar System goes to Saturn.

Just for a comparison, Jupiter measures 142,984 km across its equator. Saturn for comparison is only 120,536. So Jupiter is only 1.18 times as big of Saturn. Saturn is big, but it has a much lower mass. Once again, Jupiter is 3.34 times as massive as Saturn.

Since Saturn is so big, but has so little mass, it has a very low density. In fact, if you had a pool big enough, Saturn would float. The density of Saturn is less than water. And this means that you wouldn’t experience a lot of gravity if you tried to walk on the “surface of Saturn”. If you were standing on the surface of Saturn (I know, that’s impossible), you would experience only 91% the force of Earth’s gravity.

If you wanted to compare Saturn to Earth, it’s 9.4 times as big as the Earth, and 95 times as massive. It it was just a hollow shell, you could pack 763 Earths inside Saturn, with a little room to spare.

Wanna see Jupiter? Here are amazing telescopes from Amazon.com which you can buy at reasonable prices:

Here’s the article about how Jupiter is the biggest planet. And here’s another article about just how big planets can get.

If you’d like more info on Saturn, check out Hubblesite’s News Releases about Saturn, and another page on Saturn from NASA’s Solar System Exploration Guide.

We have recorded a whole series of podcasts about the Solar System at Astronomy Cast. Check them out here.

July 8, 2008December 24, 2015 by Astronomy Cast

Podcast: Humans to Mars, Part 3 – Terraforming Mars

Artist impression of terraformed Mars. Image credit: NASA

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And now we reach the third part of our trilogy on the human exploration and colonization of Mars. Humans will inevitably tire of living underground, and will want to stretch their legs, and fill their lungs with fresh air. One day, we’ll contemplate the possibility of reshaping Mars to suit human life. Is it even possible? What technologies would be used, and what’s the best we can hope for?

Click here to download the episode

Humans to Mars, Part 3 – Terraforming Mars – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

July 8, 2008December 24, 2015 by Tammy Plotner

Planetary Alignment Dazzles Weekend SkyWatchers

July 6: Saturn, Mars, Regulus and Moon - Richard McCoy

We warned you it was about to happen! Even though you may have been clouded out of viewing this weekend’s awesome alignment of Regulus, Mars and Saturn dancing with the Da Vinci Moon, our friendly photographers around the world were happy to share the view with us. Unlike the many erroneous myths that often surround such occurrences, planetary alignments are nothing more than the visible clockwork mechanism of our natural skies.

While Saturn and Mars descend through the “Sacred Hoop”, we have to remember that such alignments are not rare – just natural. Rumors and myths of calamities and catastrophe have abounded since the beginning or oral history when they occur, and it is amazing just how quickly these stories dissipate once the alignment has passed and nothing happened! Without rehashing doomsday prophecies, we need to take a closer look at alignments for just what they are…

An awesome display of celestial mechanics.

Each and every planetary alignment holds an opportunity to expand awareness about astronomy. It is a proven fact that the human eye follows the Gestalt Laws of Organization – the study of how people perceive visual components as organized patterns or wholes, instead of many different parts. We develop a fixation on such patterns when we see them. Ask yourself if your own eye is not drawn to this image of the alignment! The parallax is so far and so slow, that we simply cannot attach anything more than a mystical sense of wonder at the visualization. And that is not a bad thing… It draws people to require an explanation for what they see.

Be a good astronomer and stop misinformation in its tracks. When people you know ask about what they have seen in the sky, tell them! Explain how the stars and planets work just like a clock, each following their gear and routine. Alignments happen every hour… 1:05 and five seconds… 8:40 and 40 seconds.. and the sky is no different. If our eyes were sensitive enough, just think of all the deep sky alignments that occur each month as the Moon and planets traverse the ecliptic plane! How many stars hidden behind blue skies does our own Sun align with each and every second of the day?

And stay tuned for the next awe inspiring event…

The two incredible images of this weekend’s planetary alignment belong to Advanced Optical and Radio Astronomers International Associates members, Richard McCoy (panoramic image) and Shevill Mathers (closeup). We appreciate the time and energy you put into these photos and thank you for sharing with us!

July 8, 2008December 24, 2015 by Nancy Atkinson

Phoenix Brings New Sample to Wet Chemistry Lab

The Phoenix Mars Lander used its robotic arm to deliver a second sample of soil for analysis by the spacecraft’s wet chemistry laboratory. Data received from Phoenix on Sunday night confirmed the soil was in the lab’s cell number 1. This image taken by the the lander’s Surface Stereo Imager shows the Robotic Arm scoop positioned over the Wet Chemistry Lab Cell 1 delivery funnel on Sol 41, or July 6. Test results will be compared in coming days to the results from the first Martian soil analyzed by the wet chemistry laboratory two weeks ago. That laboratory is part of Phoenix’s Microscopy, Electrochemistry and Conductivity Analyzer.

On Monday, Phoenix also tested a method for scraping up a sample of icy material and getting it into the scoop at the end of the robotic arm. Photography before, during and after the process will allow evaluation of this method. If the test goes well, the science team plans to use this method for gathering the next sample to be delivered to Phoenix’s bake-and-sniff instrument, the Thermal and Evolved-Gas Analyzer (TEGA). The science team wants to be as precise and quick as possible in delivering the next sample to TEGA, as it possibly could be the last time the ovens can be used because of a short circuit that may occur the next time the oven is activated.

News Source: U of Arizona

July 7, 2008December 24, 2015 by Nancy Atkinson

Exploding Asteroid Theory Gains Evidence

About 13,000 years ago, woolly mammoths roamed the North American continent and the first known human society in that region, known as the Clovis civilization, lived there as well. But geologic and archeological evidence shows they both suddenly disappeared, and scientists have long debated the mystery of the mass extinction of both animals and humans about 12,900 years ago. At that time, climatic history suggests the Ice Age should have been drawing to a close, but instead rapid climate change initiated an additional 1,300 years of glacial conditions. But scientists couldn’t agree on the cause of the sudden change in climate. However, about two years ago geophysicist Allen West proposed that an asteroid or comet exploded just above the earthâ€™s surface at that time over modern-day Canada, sparking a massive shock wave and heat-generating event that set large parts of the northern hemisphere ablaze, setting the stage for the extinctions. Another scientist set out to prove West wrong, but ended up finding evidence to support the exploding asteroid/comet theory.

Ken Tankersley, Anthropology professor at the University of Cincinnati studied sites in Ohio and Indiana that offers the strongest support yet for the exploding comet/asteroid theory. Samples of diamonds, gold and silver found in the region have been conclusively sourced through X-ray diffractometry to have come from the diamond fields region of Canada.

Tankersley and West both believe the best scenario to explain the presence of these materials this far south is the kind of cataclysmic explosive event described by Westâ€™s theory. “We believe this is the strongest evidence yet indicating a comet impact in that time period,” says Tankersley.

Previously, geologists believed the deposits of the gems and precious metals were brought south from the Great Lakes region by glaciers. But they are found at a soil depth consistent with the time frame of the comet/asteroid event.

“My smoking gun to disprove (West) was going to be the gold, silver and diamonds,” Tankersley says. “But what I didnâ€™t know at that point was a conclusion he had reached that he had not yet made public â€“ that the likely point of impact for the comet wasnâ€™t just anywhere over Canada, but located over Canadaâ€™s diamond-bearing fields. Instead of becoming the basis for rejecting his hypothesis, these items became the very best evidence to support it.”

Additional work is being done at the sites looking for iridium, micro-meteorites and nano-diamonds that bear the markers of the diamond-field region, which also should have been blasted by the impact into this region.

As Tankersley, West and additional scientists compile more data, they’ll be looking for more clues to help explain the history of our planet and its climate.

“The kind of evidence we are finding does suggest that climate change at the end of the last Ice Age was the result of a catastrophic event,” Tankersley says. “The ultimate importance of this kind of work is showing that we canâ€™t control everything,” he says. “Our planet has been hit by asteroids many times throughout its history, and when that happens, it does produce climate change.”

Original Source: Science Daily

July 7, 2008December 24, 2015 by Fraser Cain

Pictures of Saturn

Cassini's image of Saturn and Earth. Image credit: NASA/JPL

Saturn is easily the most beautiful planet in the Solar System. To celebrate this natural wonder, lets look at some beautiful pics of Saturn.

But if you want to see Saturn by yourself, you can check out these cool telescopes that will help you see the beauty of planet Saturn.

Let’s start with one of the most beautiful photos of Saturn ever taken. This image of Saturn was taken by NASA’s Cassini spacecraft when it was behind Saturn. In other words, the Sun is completely obscured by Saturn, and illuminating it from behind. The tiny speck in the upper, left-hand side of Saturn’s rings is our own home planet Earth.

This is a picture of Saturn taken by the ground-based Keck telescope, located atop Mauna Kea in Hawaii. It’s one of the most powerful telescopes on Earth. The Saturn photo was taken in infrared, and shows the strange hot spot located at Saturn’s south pole.

It’s not the best picture, but you’re looking at one of the first ever images of Saturn captured up close by NASA’s Pioneer 11. During its mission, Pioneer 11 passed just 20,000 km above the cloud tops of Saturn, and captured the first close-up images of Saturn.

This is an example of a beautiful picture of Saturn taken by NASA’s Voyager 1 spacecraft in 1980. As you can see, the quality has improved significantly over the image captured by Pioneer 11. Both Voyager 1 and Voyager 2 made quick flybys of Saturn and then sped off into space. When Voyager 1 completed its flyby of Saturn, it sped off into the depths of space, while Voyager 2 went on to visit Uranus and Neptune as part of its Grand Tour of the Solar System.

Here’s another image of Saturn captured by NASA’s Cassini spacecraft. This photograph was taken in May 2004, when Cassini had almost arrived at Saturn. The spacecraft spent another 4 years orbiting Saturn as part of its primary mission, and at the time of this writing, it’s still going strong.

We have written many articles about Saturn for Universe Today. Here are some facts about Saturn.

July 7, 2008December 24, 2015 by Tammy Plotner

The 16″ Meade LightBridge – That’s What I Like About You…

Dobsonian Telescope — The Meade 16" LightBridge

At around $2000, this “light bucket” telescope isn’t for everyone, but if you are interested in big, big aperture and have a little practical knowledge of how to correct some design flaws, then step inside and check out the Meade 16″ LightBridge Truss Tube Dobsonian…

Affordable Big Aperture Telescopes

Affordable aperture – that’s the catch phrase for all dobsonian style telescopes. You trade in drive motors, GoTo systems and the slow motion controls of an equatorial mount for the ease and simplicity of the altaz dobsonian design. Once upon a time, these monsters were all solid tube construction, but new lines of thinking have introduced the truss tube over several telescope models and Meade was one of the first to make it affordable. However, $2000 is a significant amount of money… Is what you get for the buck worth it?
Other Truss Tube Dobsonian Telescopes to choose from:

Inside the Design of a Truss Tube Dobsonian…

Make no mistake. It might resemble two other very notable manufacturer’s truss tube telescopes – but it isn’t. There is a reason the Meade 16″ LightBridge costs about half the price of the competitor models. It has a few design flaws. Let’s address these issues:

According to Meade: “It’s a big telescope that goes anywhere. New LightBridge truss-dobs from Meade take down and set up quickly. So you can take one of these massive windows on the universe out to your favorite dark sky locations with ease.” Maybe YOU can, but for most of us, the near 70 lbs. of the primary mirror cell isn’t going to be easy to to wrestle in and out of a car… and even left fully assembled at home, close to 130 lbs. isn’t going to be easy to move in and out. But, let’s be fair here. Part of the beauty of this telescope design is that it can be dismantled with ease. Yes. That part is true. It can be assembled and reassembled. But even most experienced hands will find that the upper optical tube assembly is very unstable with a narrow lip and one set of hands to work with – it requires two people to feel secure. The mounting hardware isn’t the greatest and should be replaced. Once assembled, I think you’ll find yourself reluctant to take it apart again, and therefore a good telescope dolly is required.

The next thing you’re going to find is the interior non-reflective coatings can use some help. Again, for experienced telescope users, this isn’t a problem – just an inconvenience. Now that it’s together, protection becomes an issue… And another expense. Meade no longer makes their own brand shroud and cover for the 16″ LightBridge, so you’re off and looking for after market accessories. Hey. No problem. It’s little things like this that a telescope user knows and expects. Now, let’s take it out and use it!

Using the Meade 16″ LightBridge…

“Steel RA Roller Bearings make movements smooth and effortless.” Yep. They sure do. The Meade 16″ LightBridge moves just as smooth as silk. So smooth, in fact, that the included altitude and azimuth tension adjustment knobs won’t stop it from gently drifting its way down to level when aiming at anything lower than about 30 degrees. Again, we have a slight design flaw – felt roller bearings instead of teflon. Again, it is something that can be corrected, but requires a little knowledge of telescope workings. (And don’t be too shocked when you remove them to find that one is even thicker than the other!) Even with the change, the supplied Meade 26mm QX Wide Angle 2″ Eyepiece will make it slowly drop when aiming low. Correction? You got it. Add weight to the back end.

Final Thoughts on the Meade 16″ LightBridge…

And now that all of these changes have been made, just what do I think about the Meade 16″ LightBridge?

Over the years I’ve come to expect things not to be perfect when ordering a telescope that costs a little less – so I don’t fault Meade. These are all minor issues that will work themselves out with time and tender loving care. What I can tell you is Meade’s boast of “Prepare to cross the universe.” is being modest. Prepare yourself to be blown away! As always, Meade mirrors are single-handedly some of the finest optics I’ve ever had the pride and joy to own. There is no coma. There is no issue. Knife edge test?: More like a razor. The mirror on this telescope is absolutely optically perfect. What’s more, the Meade 16″ LightBridge was sweet and easy to collimate. Aluminum coated with magnesium fluoride over coat on both primary and secondary mirrors have withstood the test of time on my other large Meade dobsonian telescopes, and I expect the same performance from this one. The focuser works like a charm and is welcome upgrade from Meade’s original 2″ focusers. The finder leaves a bit to be desired, but hey… I’m an optical finder kinda’ person. You might like the illuminated bullseye.

All in all? The Meade 16″ LightBridge is a great telescope. Since first light it has collected countless open clusters and resolved double handfuls of globular clusters. It has made its way to the distant galaxies, and shown me spiral arms, dustlanes and stellar cores. It has walked across the central star in the Ring Nebula, blasted the blue right out of the Saturn Nebula, and revealed the braiding in the ring of the Helix. The Meade 16″ LightBridge has shown the Casinni Division of Saturn’s rings as wide as a highway, and Jupiter’s Red Spot and black holes of galiean transits.

What’s more, the Meade 16″ LightBridge is one helluva comet hunter… And that’s what I like about you.

July 7, 2008December 24, 2015 by Fraser Cain

Saturn for Kids

Color view of Saturn. Image credit: NASA/JPL/SSI

Want to help your kids learn more about Saturn? There are many great resources out there, which I’ll get to in a second.

But first, have you – or your kids – ever actually looked at Saturn with your own eyes? Many amateur astronomers say that seeing Saturn through a telescope was the moment that turned them onto the hobby that lasts a lifetime.

Chances are you’ve seen Saturn many times in the past, but you just didn’t realize it. When Saturn is high in the sky, it looks like a very bright star, easily visible with the unaided eye.

But to really appreciate it, you’ve got to see Saturn in a telescope. Find a friend with a telescope, or find your local astronomy club, and learn when they’re having an open telescope night. Ask to see Saturn, and then anything else they’re able to find for you.

Build a scale model of the Solar System
We’ve got a tutorial here on Universe Today that helps you build a miniature version of the Solar System. The Sun fits on a piece of paper, and then the rest of the planets fit within about 1 km from the Sun – easy walking distance for the kids. We even made little rings for our Saturn.

Learn about Saturn’s density
Saturn’s the only planet in the Solar System that would float if you could find a pool of water large enough. The density of Saturn is very close to the density of apples. So put some rings around an apple, and toss it into the tub.

Learn about their weight on Saturn
The gravity of Saturn is about 90% the gravity on Earth. Have your child stand on a bathroom scale, and then support them to the point that they’re 90% of their weight. Now let them walk around the room with you supporting a little of their weight. What does it feel like?

Draw Saturn
Take a look at some pictures of Saturn, and then try drawing your own. See the different bands on the planet, ranging in color from white to yellow to orange. And draw the rings, with different colors, and gaps in between. Try drawing completely different planets with rings.

Want more information about the Solar System for kids? Here’s some material on the Moon for kids, and Jupiter for kids.

And there are more great resources for kids on the Internet. Check out Kids Astronomy. From grown-ups, here’s Hubblesite’s News Releases about Saturn

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.