The four largest moons of Jupiter remain are a delight to watch as they change position constantly in their continuous Newtonian dance with the big planet. The moons of Jupiter make for ideal viewing for all stargazers, especially kids or near-beginners with binoculars or a small telescope.
Why is the universe the way it is?
Philosophers have debated the question for centuries. Clerics claim nature is the work of a divine hand. And modern scientists use a mix of logic, mathematics, and experiment seek the fundamental physical principles to explain why the universe behaves as it does.
But what if there’s a simple explanation for it all?
Like dazzling jewels set against the black velvet of deep space, open (or galactic) star clusters showcase glittering new stars as they emerge from their dusky birth in giant molecular clouds.
Many close-up images of globular star clusters reveal pin-prick blue stars in places where no blue stars have a right to be. These interlopers are called “blue stragglers”, and they’ve fascinated astronomers for decades. That’s because every theory of how stars evolve shows that blue stars in old globular clusters should have disappeared billions of years ago. So where did these blue stars come from? And does their existence prove that astronomers are wrong about how stars work?
Last time we looked at a nifty scaling trick to help understand the immense size of the Milky Way. If the Earth-Sun distance shrinks to one inch, the nearest star lies 4.3 miles away and the diameter of our galaxy is 100,000 miles.
Such distances within our galaxy are still a little staggering. Now let’s scale up to understand the size of the universe in terms of a big galaxy. On these terms, the size of the universe becomes much easier to understand…
The nearest star, Proxima Centauri, is some 25 trillion miles away. The Orion Nebula lies about 8,000 trillion miles away. And we are some 162,000 trillion miles from the centre of our own galaxy, the Milky Way. These are mind-numbing distances, completely foreign to the everyday experience of even the most hardened stargazers, and they make it hard to grasp the distance scale of our immense galaxy.
But there’s a happy numerical coincidence that makes it much easier to contemplate such distances.
Here’s how it works…
The planet Uranus is the largest of the two “ice giants” of our solar system and the seventh planet from the Sun. At an average distance of 3 billion kilometres, Uranus lies twice as far as from the sun as Saturn and takes a leisurely 84.3 years to make a single revolution. Uranus was the first planet discovered with a telescope. And it remains a featureless but satisfying target for backyard stargazers.
Now the second part of the story of the accidental birth of radio astronomy, wherein four years after Karl Jansky’s discovery of radio waves from the Milky Way, a young radio engineer named Grote Reber built the world’s first radio telescope… by himself… in his backyard!
In the early 1930′s, Bell Labs, the research division of AT&T, wished to use radio “short waves” for transatlantic radio telephone links. A young engineer, Karl Jansky, was assigned the job of finding sources of radio static that might interfere with radio transmissions. During his work, he made an accidental discovery that revolutionized astronomy.
Here’s a little mental health break… a stupendous view of the cannibal galaxy NGC 5128. This odd-shaped garbled galaxy is actually two galaxies: an giant elliptical galaxy merging with a flat dusty spiral. This interaction has stimulated frenzied star forming activity in the dust lanes of the spiral.
The 62 moons of Saturn are a fascinating mix of objects, ranging from tiny bodies discovered by close-in spacecraft to the enormous moon Titan, which you can see in a pair of binoculars from your backyard. Fifty-three of Saturn’s moons are named, and thirteen have a diameter larger than 50 km. Just seven of Saturn’s moons are large enough to pull themselves into a spherical shape.
Of this large collection of moons, nine were discovered with telescopes before the age of spaceflight. They are, in increasing distance from Saturn: Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion, Iapetus, and Phoebe. The moons were named after the Titans of ancient Greek legend.
This news is hot off the presses tonight, and you’re among the first in the world to hear: an international team of astronomers have deduced the details of a planet around a nearby star, and revealed a “super-exotic” rocky world that would make the planet Pandora in the movie Avatar pale in comparison.
You can see the home star of this small, hot, and dense planet with your unaided eye or with a modest pair of binoculars.
No one’s ever seen a supermassive black hole. But today you’ll come close as you examine so-called Seyfert galaxies, a special class of spiral galaxy with immensely bright cores set aglow by hot gas spiraling into central black holes the size of a solar system.
Over the next weeks, we’ll peer up and out of the plane of our Milky Way at fields of distant galaxies in Leo, Virgo, and Coma Berenices. Every galaxy you see, and nearly every one of the billions of galaxies in the universe conforms to one of four basic shapes first outlined by Edwin Hubble in the 1930′s. This will help you understand a little more about each galaxy you see…
Something different today… a chance for you to make a real contribution to astronomy by helping search for Earth-like planets around nearby stars. You don’t need a telescope, or technical training, or dark sky. Just a little free time, a computer, and a desire to take part in groundbreaking science.
Here’s what it’s all about…
I was going to suggest you inspect a lovely double star in Andromeda this weekend, but November weather is clouding out many stargazers.
So let’s do something completely different. Here’s a video featuring an old colleague of your humble publisher from many years ago, Dr. Jaymie Matthews of the University of British Columbia. In this video, based on the 2008 movie Stargate:Continuum, Jaymie explains the possibilities of time travel.
(Warning: there are a couple of spoilers for the Stargate:Continuum movie in this video, so beware if you plan to see it…)
The whole video is fascinating. But even the first couple of minutes will change your perspective on time travel, and maybe leave you a little wistful…
We come to #6 on our “Bucket List for Backyard Stargazers”… the passage of Venus across the solar disk as seen from the Earth, also called the transit of Venus.
While not as striking as a solar eclipse, a transit of Venus is far more rare. It’s happened just seven times since the invention of the telescope more than 400 years ago. The next transit in June 2012 will be our last chance to see this remarkable event. There won’t be another until December 2117.
Here’s what you need to know to cross the transit of Venus off your celestial bucket list…
Follow the arc of the Milky Way on a dark night away from city lights, and you’ll see knots and ribbons of darkness weaving among the bright star clouds. Many new stargazers think such dark regions are simply absences of stars. But their true nature is far more interesting. These dark regions are immense clouds of gas and cold interstellar dust, much of it made from the dregs of dead stars that exploded long ago. In time, some of these so-called dark nebulae will contract, heat up, and recycle themselves by collapsing into clusters of hot, new stars.
If you own a good star atlas and look carefully at the objects represented on each star map, you’ll see hundreds of objects from the Messier catalog (M) and New General Catalog (NGC). But sometimes, you may come across objects with the obscure designations like Cr142 or Cr399 or Cr285. These “Cr” objects are open star clusters from the little-known Collinder catalog, a list of almost 500 open star clusters spread all over the northern and southern sky.
Something a little different today… a video of a talk by professional astronomer Garik Israelian about how the science of spectroscopy might soon answer the question, “Is anyone out there?” This sort of science is near and dear to us, because once upon a time we were involved in this sort of work… measuring and calculating how light of different wavelengths interacts with matter. It’s a powerful and subtle technique, and Dr. Israelian makes a good case for how alien life might be detected this way.
Take a look at your index finger held out arm’s length. Now watch your finger as you alternately close one eye, then the other. See how it appears to move back and forth against the more distant backdrop? This effect is called parallax, and it’s the same effect astronomers use to directly measure the distance to nearby stars.
Sometimes, though not often, nature points the way to knowledge even the wisest philosophers believe to be beyond our comprehension.
The composition of stars is one example. In 1835, the French scientist Auguste Comte declared the composition of stars was an example of knowledge forever beyond human understanding. Just a few years after Comte’s death, 19th century astronomers carefully measured starlight with prisms and spectroscopes and discovered that stars are made of the same material found on Earth… hydrogen and carbon and oxygen, among other elements.
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I miss Arthur C. Clarke. He died more than 18 months ago at age 90, but the great science-fiction writer left more than 30 novels and dozens of short stories that described a mostly optimistic vision of mankind’s exploration of space and his responsible use of technology. His most famous work, 2001: A Space Odyssey, was made into what many consider the best science fiction movie of all time.
Our article last week about the zodiacal light resulted in quite a few emails. Seems that many of our readers can see this light, although some didn’t know what it was.
And some of you asked if it’s possible to photograph zodiacal light. In fact, this sight is not too hard to photograph with a simple camera and lens, although taking good astrophotos is a little different than daytime shots. If you’re interested in basic astrophotography with a digital camera, here’s a resource to help you get up to speed quickly…
Now, to today’s business… this one is a little longer than usual, but I think you’ll find it interesting…
Over the spring and summer, we finished our series on the lives of stars by describing the most violent event in the universe: a massive dying star exploding as a Type II supernovae.
But there is another type of supernova with a completely different physical cause. This is the Type Ia supernovae, which also turns out to be indispensable to astronomers for measuring the size of the universe.
Supernovae, the explosive deaths of massive stars, are fairly rare events. They occur just once every 50 years or so in the Milky Way. But we owe our very existence to some long forgotten supernova billions of years ago which created most of the heavy elements in our solar system, including the elements that make life… and you… possible.
So it might be worth knowing a little more about these spectacular explosions…
We’ve been told we’re crazy to try to explain the evolution of larger stars in a minute or two, which is the unofficial time limit of most articles in One-Minute Astronomer. But hey, we like a challenge. So here’s the story on how large stars, say at least 3-5x the mass of our Sun, will end their lives.
Some new subscribers are terrified by the coordinate system for the celestial sphere. But if you understand the concept of latitude and longitude on the Earth, you can understand their celestial equivalents. Here’s what you need to know to find things on a star map.
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After a mid-sized star ejects its outer layers as a planetary nebula and runs out of fuel, what remains is a blazing-hot mass of carbon and densely-packed electrons called a “white dwarf”. Some 97% of all stars, including the Sun, will end their lives as a white dwarf. These are dim objects, but a few are bright enough for you to see with a backyard telescope.
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After forming out of a cloud of gas and dust, a mid-sized star like our Sun sits nicely on the main sequence and burns hydrogen in its core for some 5 billion years. Then, the end begins. (This one’s a bit longer, but stay with it… you’ll know much more about how stars work in just a couple of minutes…)
We get many questions each week at One-Minute Astronomer from some of our nearly 10,000 subscribers. Here’s an attempt to answer some of the more frequently-asked questions. And remember, never be afraid to ask questions. Like my old chemistry professor once told me, “There are no dumb questions. Only dumb mistakes.”
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Those of you on Facebook may have heard of the “25 Random Things About Me” phenomenon, where you are invited to write, well, 25 random things about yourself for all your friends to read, then invite your friends to do the same. It’s an intriguing literary exercise for sure.
But don’t worry, we’re not going to write 25 random things about ourselves… we’re not that interesting. In the spirit of this recent cultural novelty, we present “25 Random Things About… The Milky Way Galaxy”.
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In the prime of their lives, when stars burn hydrogen in their core, there’s a clear and simple relationship between a star’s color and brightness. Nearly a century ago, astronomers developed a way to illustrate this relationship with what’s now called the H-R Diagram, a critical tool for understanding how stars evolve. Here’s how it works.
Here’s a short explanation of star colors to help you better appreciate what you see when you look at the stars in the night sky. In just a couple of minutes, you’ll understand more about stars than 99% of people who’ve ever lived.
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Most globular clusters are spherical collections of ancient stars born not long after the universe began. At first, you might think globular clusters all look the same: just fuzzy balls in the eyepiece of your telescope. But look closer. Each differs in shape and structure, as distinct as a human face. And globulars clusters contain some of the oldest stars in the universe.
The ancient Greek philosopher Aristotle declared the heavens were perfect and unchanging, and his view went unchallenged for nearly 2,000 years. But keen-eyed renaissance astronomers like Tycho Brahe discovered stars that varied in brightness. The science of variable stars was born.
Continuing from the last issue, here are five more fine books for any serious amateur astronomer.
“Can you suggest a good astronomy book?” We get that question at least once a week at One-Minute Astronomer. So by popular demand, we present mini-reviews of five superb books for beginning and intermediate backyard astronomers. If you’re a casual observer, these may be all the books you’ll ever need.
In July, we went through the basic idea of how a dying star flares into a planetary nebula. But enough science. Here are some spectacular planetary nebulae you can see from your backyard with a small telescope or pair of binoculars.
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Like dazzling jewels set against the black velvet of deep space, open (or galactic) star clusters showcase glittering new stars as they emerge from their dusky birth in giant molecular clouds.
This is easy, I promise… no calculus required! Just a few simple formulae to help you get the most out of your telescope and binoculars and find your way around the sky.
As you know, the Milky Way is a spiral galaxy… a majestic pinwheel in space. But how did astronomers map out the spiral structure of the Milky Way from our position on the far edge of the galaxy? They used a special type of radio wave made by massive clouds of hydrogen atoms spread throughout the spiral arms of our galaxy.
(Note: This article is a little more technical than most, but try stay with it until the end… you’ll be able to follow along.)
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In their youth and middle age, medium-sized stars like our sun generate energy from nuclear fusion, the transmutation of light elements into heavier elements. But when the fuel runs out, stars spend their last days catapulting their outer layers into space to make a planetary nebula. Here’s how it works.
The ancient Greek philosopher Aristotle declared the heavens were perfect and unchanging, and his view went unchallenged for nearly 2,000 years. But keen-eyed renaissance astronomers like Tycho Brahe discovered stars that varied in brightness. The science of variable stars was born.
Spring is the time to peer up and out of the plane of our Milky Way at fields of distant galaxies in Leo, Virgo, and Coma Berenices. Every galaxy you see, and nearly every one of the billions of galaxies in the universe conforms to one of four basic shapes first outlined by Edwin Hubble in the 1930′s.
Astronomers use a numerical measure called “magnitude” to describe the brightness of objects in the night sky. Here’s how it works.
The Basics
• Brighter objects have a smaller numerical value of magnitude than fainter objects. So a star with magnitude 4 is brighter than a star with magnitude 5, for example.
• An object with magnitude 1.0 is 100 times brighter than an object with magnitude 6.0. So each step of 1.0 in magnitude is the fifth root of 100. That means a star of magnitude 3.0 is 2.512 times as bright as a star of magnitude 4.0, which is 2.512 times as bright as a star of magnitude 5.0, and so on. Try it yourself, if you have a calculator handy.
• With your naked eye, you can see objects down to 6th magnitude; with a pair of 7×50 binoculars you can see down to 10.5 or so; and with an 8” telescope, perhaps 13.5; using sophisticated cameras and software, the Hubble can detect objects to about 30th magnitude… about 4 billion times fainter than you can see with your eye.
• An object brighter than 0th magnitude has a negative magnitude; the brightest star, Sirius is magnitude -1.4; the full moon is magnitude -13, and the Sun is a blazing -26th magnitude.
A Deeper Look
• The “apparent” magnitude measures how bright a star appears in the sky, regardless of how bright is truly is
• “Absolute” magnitude is a measure of the true, intrinsic brightness of a star. It’s defined as the apparent magnitude of an object if it was 32.616 light-years away
• While the sun has an apparent magnitude of -26, it has a modest absolute magnitude of 4.7.
• Deneb, the brightest star in Cygnus, has an absolute magnitude of -8.73, more than 250,000 times as bright as our Sun. But its apparent magnitude is only 1.25 because it’s so far away, roughly 3,200 light-years from Earth.
A Bit of History
The ancient Greek astronomer Hipparchus developed the system of magnitude we use today back in 120 B.C. He used his system to catalog the brightness and position of 1,080 stars. In 1996, a European satellite named after Hipparchus created the most accurate catalog to date. It lists the precise positions of over 120,000 stars, and is available online to anyone who wants to use it.
Personal View
I’ve tried many times, unsuccessfully, to see the “inhumanly distant” object 3C273, a quasar in Virgo. About 1.8 billion light years from Earth, 3C273 is the brightest quasar in the sky at apparent magnitude 12.8 and absolute magnitude -26.8. I haven’t had the patience to tell it apart from the background stars. The light from 3C273 that reaches us tonight left when single-cell organisms were the highest life forms on Earth.
