Bringing the Universe to Your Classroom!

Showing posts with label Big Dipper. Show all posts
Showing posts with label Big Dipper. Show all posts

Saturday, June 1, 2019

What's In The Sky - June 2019

Get ready for summer stargazing! With the weather warming up, June is a great time of year to enjoy relaxing evenings under starry skies with your telescope or astronomy binoculars. Here are a few of Orion Telescopes and Binoculars top picks for June 2019 stargazing:

Jupiter at Opposition

Jupiter shines brightly in the constellation Ophiuchus during June and will be at opposition to the Sun on June 10. Around the same time is also its closest approach to Earth, making it an ideal time for observation. Use a SkyQuest XT6 PLUS Dobsonian along with the 10mm Plossl eyepiece and Shorty 2x Barlow lens that come with it to get views of the largest planet in our solar system at 240x magnification! Or, pair it with the Orion StarShoot 1.3mp Solar System V Imaging Camera for an affordable planetary imaging system!

M13 - Great Globular Cluster in Hercules imaged on ATEO-1 by Insight Observatory.
M13 - Great Globular Cluster in Hercules imaged on ATEO-1 by Insight Observatory.

Summer is Globular Season!

Globular star clusters are densely packed balls of stars that are concentrated towards the center of the Milky Way. June skies offer some of the finest globular cluster viewing opportunities. While you can detect most globular clusters in 50mm or larger binoculars, a moderate to high-power eyepiece in a 6" or larger telescope offers the best chance to resolve individual stars. In the constellation Hercules, look for M92 and the “Great Cluster” M13. In Scorpius, look for M4 and M80. The constellation Ophiuchus is home to six globulars – M10, M12, M14, M107, M9, and M19. Can you spot them all?

The Virgo Cluster

A treasure trove of galaxies can be explored if you point your 6” or larger telescope toward the Virgo Galaxy Cluster. The Event Horizon radio telescope array released the first image of a black hole in April, of the supermassive black hole in M87. While the black hole might need an Earth-sized radio telescope array to resolve it, the galaxy itself can be viewed with more affordable equipment. Aim your telescope at M87 in the constellation Virgo and start scanning the surrounding night sky. How many galaxies can you see?

Summertime Star Party

Take advantage of the New Moon on June 3rd and the galaxies and globular clusters visible to put on a star party! Not only will the dark skies of the moonless night provide great opportunities to see fainter objects more clearly, but the warm June weather will make it easy to enjoy starry sights all night long with friends and family.

Swirling Spirals

Around 10pm in mid-June, two glorious, face-on spiral galaxies M51 and M101 will both be in a great position for viewing and imaging. Look for M51, the Whirlpool Galaxy, to the southwest of the star Alkaid at the end of the Big Dipper's "handle". Scan the sky to the northeast of Alkaid to find M101, the Pinwheel Galaxy. Under very dark skies, these distant galaxies can barely be detected in smaller telescopes, but a 10" or larger reflector will reveal much more impressive views. If you're viewing from an especially dark location, try to resolve the delicate spiral arms of M51 in a 10" or larger telescope.

M101, M27, and M51 imaged on ATEO-1 by Mr Daniels 8th-Grade Students from the Plymouth Community Intermediate School, Plymouth, MA.
M101, M27, and M51 imaged on ATEO-1 by Mr Daniels 8th-Grade Students from the Plymouth Community Intermediate School, Plymouth, MA.

Gems of the Summer Triangle By 10pm in mid-northern latitudes, the Summer Triangle, comprising beacon stars Vega (in Lyra), Deneb (in Cygnus), and Altair (in Aquila), will be fully visible above the horizon. Several celestial gems lie within its confines, including the Ring Nebula (M57), the Dumbbell Nebula (M27), open star cluster M29, and the visually challenging Crescent Nebula (NGC 6888). To catch a glimpse of the elusive Crescent, you'll almost certainly need an Orion Oxygen-III Filter in a larger telescope.

Summer Sky Challenge Discovered in 1825 by the German astronomer Friedrich Georg Wilhelm von Struve, NGC 6572 is bright enough to be seen in a humble 60mm refractor telescope from a dark sky site; but it is very, very small! At only 8 arc-seconds in size, it takes a lot of magnification to distinguish this from a star. The easiest way to find it is to look in the target area for a green star. NGC 6572 is one of the most intensely colored objects in the night sky. Some say this is green, some say it is blue; what do you think?

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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Wednesday, August 1, 2018

Home Is Where the Converged Galactic Core Is

Arcturus is the bright, reddish star which can be seen during the summer months, currently, at an altitude of about 40° (or, about 4 fist-widths) from the western horizon at sunset, and from about sunset until around 2:00am, when it sets below the western horizon.

Arcturus is the brightest star in the constellation, Bootes - the 'herdsman'; the brightest star in the northern celestial hemisphere, and the fourth brightest star in the skies of Earth. Its name comes from the ancient Greek, meaning, "Guardian of the Bear"; Arcturus appears to be trailing the constellations, Ursa Major and Ursa Minor (the 'Great Bear', and the 'Little Bear', respectively). It can easily be located by following the arc of the handle of the Big Dipper, just out into the nearby, celestial blackness - just remember: "Arc, to Arcturus"; and, there Arcturus sits, alone.

Two Small Galaxies Collide to Form Our Milky Way Galaxy

This 'red-giant' star, is about the same mass as our Sun, but it is nearly 200 times more luminous. This is because of its enormous size, with a diameter of 22,000,000 miles. Our Sun, "Sol", currently, has an average diameter of 864,000 miles, making Arcturus nearly 26 times the size of the sun, but - it is also 217,000,000,000,000 (217 trillion) miles from Earth, or about 37 light-years distant, accounting for its apparent, relative diminution to our sun. Arcturus is near twice as old as our Sol, at around 7.1 billion years.

Red giant stars are stars that are in the later stages of stellar evolution: briefly, they have exhausted their supply of the fuel that sustains them at their cores - Hydrogen. They are still consuming the remaining H in their outermost, gaseous shells by thermonuclear fusion, but have lost so much of their original mass that their surface temperature drops, significantly, and they become so, "swollen", that their remaining 'bulk' is gradually extended into the surrounding space. One day, about 4.5 billion years from now, our own Sun, currently a yellow-dwarf star on the Main Sequence Diagram of Stellar Evolution (also called the Hertzprung-Russell Diagram), will begin its final journey through the red giant phase, as its own nuclear furnace starts to cool down, to begin the journey to its final state - a tiny, hot star, known as a white dwarf.

Though Arcturus is 37 light-years away from our Solar system, its relatively feeble light output was used as a switch, to turn on the lights at the Chicago World's Fair, in 1933, by converting that radiation, using a photoelectric-effect process, combined with a telescope, into electrical signals and, thereby, 'tripping the switch' that turned on the lights at that fair! Though this trick could have been accomplished using almost any other sufficiently bright star, Arcturus was chosen, for the fact that its light takes almost 40 years to travel the distance to Earth, through space, and, the last time that the World's Fair was held in Chicago, was 40 years prior.

One of the more interesting things to me about Arcturus is that, though it is one of the many, more familiar stars of our Milky Way galaxy - it is not, originally, from 'here'; it is, literally, an 'alien' star -- from another galaxy! Now - hold on, let's not let our imaginations get the best of us here...

But, how do we know, that, our old pal, Arcturus is actually a 'rogue visitor', from some other, far-off galaxy?

It's because Arcturus orbits our Milky Way galaxy at an oblique angle, almost exactly perpendicular to the plane of rotation of most of the other stars of the galaxy. This means that it doesn't carry the same angular momentum or velocity (speed and direction) of the majority of stars, native to the Milky Way. And, there's more. Lots more.

Our galaxy - a fairly typical, the barred-spiral galaxy is, actually, an aggregate of a small "collection" of once, separate, individual galaxies!

You see, galaxies move through the universe in clusters, which are gravitationally bound to a common center of gravity, created by an original mass - say, a hypothetical, binary galactic pair.

Since all matter in the universe is gravitationally attracted to all other matter, the original, revolving pair, would soon have given in to the increasing 'force' of gravity generated by the pairs' decaying orbits, and, eventually collapsed together to form what we currently know as the Milky Way galaxy. (There may be other ways for stars to wind up as 'intergalactic rogues', such as, by gravitational sling-shot-ing, but it doesn't seem to be the case, here). But each galaxy of the original, binary pair would have possessed its own, specific inertia, as well as, specific mass, and a specific plane of rotation, bisected by a specific axis of rotation.

During the merger, most of the stars from both member galaxies would, over time, have assumed a common motion about the now-merged, galactic cores. But some stars, being farther away into the outer periphery of either galaxy, would have strayed, slightly, due to the effects of the differences of the combined angular momentums of the pair, and assumed their own orbits about the galactic core - as did Arcturus - along with 50 other known, stray stellar masses! These 51 stars are known as the "Arcturus Stream".  Other such streams are thought to exist, but these are so distant, relative to the Arcturus Stream, that they remain undetected.

Nevertheless, our Milky Way galaxy - our 'home' galaxy - has adopted these intergalactic wanderers as its own, which, is just as it should be, in my opinion, and I'm O.K. with Arcturus (much like, myself, in a way), as one of good ol' Sol's, 'intra'-galactic, adopted brothers!
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Sunday, September 25, 2016

Cool Nights and Clear Skies

Some of the clearest nights of the year arrive in late summer and early fall. In much of North America, September and October bring clearer weather than any other month. If that's not enough incentive for you to get out and do lots of stargazing, consider what comes next.

Last evening was one of those crisp nights with sparkling skies that urge me to take out the telescope and/or binoculars and do some observing. November tends to have increased cloud cover, which largely persists until mid to late spring. October is known to be the clearest of the 12 months throughout a wide span from New England through the South and lower Midwest to Texas and the Great Plains.

The Pegasus-Andromeda area spans a huge area of sky Screenshot from Stellarium
The Pegasus-Andromeda area spans a huge area of sky Screenshot from Stellarium.

Much of the country is more than 70 percent cloudy in various months. In September and October, only bits of Maine and the Northwest are so obscured. However, from November through April as much as a quarter to one-third of the country is on the unfavorable side of the 70 percent "isoneph" (line connecting points of equal cloudiness).

A mere absence of clouds is one thing, a beautifully clear and transparent sky is another. In much of North America strong cold fronts in September and October often clean the air to superb transparency. At such times we get deep blue skies by day and some of the best observing nights of the year.

What stellar sights can we behold on these nights? In the early evening, there are fewer bright stars than usual. Arcturus is setting in the west-northwest, and the Big Dipper is getting low in the southwest. The only high and bright stars are those of the Summer Triangle: Vega, Deneb, and Altair.

Capella is peaking up in the northeast. Above it, the forked branch of Perseus is ascending. Much higher is the "W" of Cassiopeia, the queen.

Face east and look high and you will see the 2nd magnitude stars of Andromeda and Pegasus forming a very long, nearly horizontal line. It starts with Gamma Andromedae on the left, fastens to the Great Square of Pegasus, and ends with Epsilon Pegasi way over in the south.
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