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Sunday, November 3, 2019

Primary Sources

How do we know that the sun is a star? -- and, that we live in a galaxy full of stars?

How do we know what the distances between those stars are?

How did we conclude that the moon and planets are illuminated by reflected sunlight, and, not through their own, intrinsic illumination?

How do we know how big the universe is, and, of what materials it is composed?

By guesswork? By simple reasoning? By concluding what we want to conclude?!

No -- never...

Vintage Engraving, Early Spectroscope Using Prisms -  Drawing by Luisa Vallon Fumi
Vintage Engraving, Early Spectroscope Using Prisms -  Drawing by Luisa Vallon Fumi

The answers to some of those questions come by way of Newton, Galileo, Herschel, the telescope, and the spectroscope - (and, yes - true, genuine, unadulterated genius, at least, in the case of Newton).

To understand these things, one has got to have some grasp, of the long hours of hard work, done by many people - sometimes, extended out, over several generations.

But, all of it was done, methodically, one step at a time. Those steps are preserved in records - written at the time, by the very people who took those steps - and exist in the various university libraries, public archives, etc. These documents, and others like them, are known as, "Primary Sources", or, "Original Sources". One notable example of an original source document, is Galileo Galilei's letter to the Duchess of Tuscany, on what he had observed through his telescope, which, has been, ever since, preserved by the Royal Archives, in Great Britain, and is available for public view. Most any college or university has a Primary Source repository, or access, to one.

One, major distinction, in perusing any primary source, is its wonderful lack of hype, sensationalism, opinions, fake news and, perhaps, best of all (in my opinion) -- no "pseudo scientists"!

Insight Observatory's network of remote robotic telescopes - ATEO-1, ATEO-2A and ATEO-3.
Insight Observatory's network of remote robotic telescopes - ATEO-1, ATEO-2A and ATEO-3.

Astronomers - professional, amateur, and citizen, alike - are, still, today needed to make observations, visually, or photographically of the night sky. One way to do this is by the use of remote, robotic telescopes and astrographs, like those, here at Insight Observatory.

Dale Alan Bryant
Senior Contributing Science Writer
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Saturday, November 2, 2019

The Telescope, and the Center Of The Universe

In the beginning, there was "us" - and, just us. (So we liked to think)

(fast-forward a few hundred thousand years...)

Around the Middle Ages, it was discovered that we inhabited a "world" - a round, spherical one. And so now, we and our world were all that there was.

But, a little later, in 1610, a physicist named Galileo Galilei, using a new and revolutionary optical instrument called a "telescope", discovered that the moon, Saturn, and Jupiter - were not just dots of light in the sky, but rather, they were, actual, "other" worlds. Not only were Jupiter and Saturn planets, in their own right, but they possessed satellites, as well. Galileo, and then others, noticed that these satellites were orbiting around their host planets - resembling miniature Solar Systems.

None of this new and revolutionary information would have been revealed, had it not been for a new and revolutionary instrument - Galileo's hand-made, tiny, 2-inch diameter instrument - the refracting telescope. (This new revelation caused a lot of problems - both, for Galileo, and for society, in general - because, just maybe - there were "others" on these "other worlds")

While Galilei did not invent the telescope, he very successfully built one and used it for astronomical observations. This image shows two telescopes in his possession. Image Credit - DPA-Picture Alliance.
While Galilei did not invent the telescope, he very successfully built one and used it for astronomical observations. This image shows two telescopes in his possession. Image Credit - DPA-Picture Alliance.

In 1783, amateur astronomer, William Herschel, made the discovery that all of these "other worlds", were, actually, a conglomeration of worlds - an "island universe", which we, today, call the "Milky Way" galaxy. Using one of his - very large, for the day (40") - reflector telescopes, Herschel was able to, roughly, determine the general shape of the "Milky Way" (something like a double-convex lens, or, the way I like to imagine it: two, inverted Frisbees!). It was apparent then that, we reside in some, isolated structure of stars, and we named our isolated home galaxy after the dim band of cloud-like light that splits the sky into two "hemispheres". (This band of diffuse light, or the "Milky Way", can still be seen from some places in the world, so I understand).

William Herschel's sketch of the Milky Way Galaxy.
William Herschel's sketch of the Milky Way Galaxy.

Sometime later, comet-hunter, Charles Messier, using his own, small, hand-made reflecting telescopes had found that the sky contained, seemingly, hundreds of small, cloud-like patches of light, similar to the milky band that circled the sky - ranging in size, up to, just larger, than the full moon. It was thought that these tiny "fogs", were just that - some type of cloudy matter, nearly, randomly distributed about the sky. All that Messier knew, was, that they were not the "comets" he was searching for. And so, they stayed, just fogs.

Then, in the 1920s, a debate took place, now known historically as the "Great Debate", on the nature of these luminous patches of fog. The debate focused on whether these structures were portions of our own galaxy, or, whether they were external structures. Around that time, a slightly pompous - but, generally brilliant astronomer, Edwin Hubble, had made another revolutionary discovery that ended the debate, altogether - these luminosities in the sky were not cloudy in nature. Hubble was able to resolve these hazy patches into individual stars, using the Hooker telescope. It turned out that they were actually, distant "island universes" (galaxies) in their own right!

In a spectroscopic analysis of the motions, of the millions of other galaxies that lie beyond our own island galaxy, the Milky Way - nearly the entire mass of the universe is receding into the distance - i.e. apparently, away from us. What's more, the velocity of any given galaxy's recession, is proportional to its distance - i.e., the farther away the galaxy is, the faster it is receding into the "background"! This situation is what produces, what's called, the "red-shift effect" - light's, own version, of sound's, "Doppler" effect. The result is that the spectra of those receding galaxies are shifted towards the red (longer wavelength) end of the visible light spectrum; in the same way that the tone from, say, a passing vehicle's horn, in a fluid, continuous way, drops in pitch as it passes by us and on to a direction that carries it farther away from us.

All of this is due to the general expansion of the universe, as a whole (hence, the "Big Bang", or, "Great Expansion" event, when began universal expansion). This condition was discovered by Edwin Hubble, back in 1929. It was his observations, now, using the 200" reflector at Mt. Palomar that revealed that the universe was in a general state of expansion. Only, a very few galaxies, appear not to be receding from us. This includes the 25 or so, member galaxies of what is called, the "Local Group", of relatively nearby galaxies, and the two satellite galaxies of the Milky Way galaxy, called, the Large, and the Small "Magellanic Clouds" (the LMC, and SMC, respectively), as well as the next, nearest, large spiral galaxy similar to our Milky Way galaxy, the Andromeda galaxy, or, M32. That galaxy is so nearby, cosmologically speaking, that it can just be detected in a clear, dark sky with the unaided eye. The galaxy lies in the constellation of Andromeda and it is a prime target for astrographic imaging, or, astrophotography.

But, from our own galactic island, it appears as if the Great Expansion event, itself, took place at the position of the Milky Way galaxy! And to make matters worse - this expansion is undergoing an apparent acceleration - one that increases, proportionally, as its distance from the Milky Way! Could it be that we are in some, privileged location, in relation to the rest of the universe? Can this really be so?

(I was going to have some fun with this, but I won't!)

The answer is, of course: No, it can't.

From the beginning of human civilization, man has revered himself to be the pinnacle of creation - whether he placed himself at some, centralized position, either on the Earth, or whether he placed the Earth, itself, at the center of - at first, the Solar System, and then the Milky Way galaxy - both of which were dead wrong. By small gradations, he has slowly discovered that there is no true center to the universe, nor is there any, true, up or down. Today, we know that our "island universe", is only one of the billions of other island universes - revealed to us, by the power of an inherently, very simple, optical marvel - the telescope.

Because of the telescope - we've not only revealed the nature of particular objects in the universe but also, general ideas as to the nature of the universe, on the whole.

Dale Alan Bryant
Senior Contributing Science Writer
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Friday, November 1, 2019

What's In The Sky - November 2019

Clear November night skies offer incredible celestial sights for stargazers to be thankful for, so bundle up and get outside for stargazing fun!

The May 9th, 2016 Mercury Transit at 9:15 am EDT - Image by Nolan D.

Transit of Mercury

On November 11th from 04:34 to 10:30 PST, Mercury will pass directly in front of the sun. Visible as a tiny shadow against the disk of the sun, a telescope with a properly installed solar filter is essential. This transit will next occur 13 years from now in 2032, so don't miss seeing it! Grab a solar filter for your telescope, or a convenient solar telescope to view the transit safely!

CAUTION: Never look at the Sun, either directly or through a telescope, without a professionally made protective solar filter installed that completely covers the front of the instrument, or permanent eye damage could result.

M45 - The Pleiades imaged at LRGB 600 sec, 2x2 bin on ATEO-1 by Insight Observatory.

The Pleiades

November is sometimes called "the month of the Pleiades," since the star cluster is visible all night long for observers in the Northern hemisphere. From a dark sky site, M45 is easy to see with the unaided eye and resembles a small "teaspoon" pattern in the sky. Use astronomy binoculars for immersive views of this open star cluster, or use a telescope with a lower-power eyepiece for a closer look at the Seven Sisters.

November 26th will be the best time of the month to observe the fainter deep-sky objects such as galaxies and star clusters because there is no moonlight to interfere.

Radiant of the Leonid Meteor Shower - Illustration by Universe Today.

Leonids Meteor Shower

Bundle up and get outside after midnight on November 17th to see the peak of the Leonids meteor shower as "shooting stars" appear to radiate outwards from the constellation Leo. The Moon will rise just before midnight, so the best time for meteor-gazing will be before then when the skies will be nice and dark. The estimated peak rate is about 15 meteors per hour.

Double Cluster in Perseus

Use a pair of big binoculars or a shorter focal length telescope with a wide-field eyepiece in November to seek out the sparkling Double Cluster in Perseus - two side by side open star clusters NGC 884 and NGC 869.

All objects described above can easily be seen with the suggested equipment from a dark sky site, a viewing location some distance away from city lights where light pollution and when bright moonlight does not overpower the stars.
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