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Saturday, April 19, 2014

The Winter Milky Way Project at Blake Planetarium

The Blake Planetarium at Plymouth Community Intermediate School was recently awarded a grant from the Plymouth Cultural Council to complete the Milky Way project. Last September, students in Ms. Shaw's class used six remote robotic telescopes for astronomy education located in Australia and New Mexico to image objects in the visible arm of the summer Milky Way. Last week, students in Mrs. Burns' sixth-grade class partnered with the planetarium, Insight Observatory, and iTelescope.net to image objects in the winter Milky Way. The objects that were imaged included nebulae from star nurseries and dying stars, as well as star clusters.

Image of Plymouth Cultural Council Logo

Students who participated in this project learned that during the winter months, we face away from the center of the Milky Way at night, making the visible arm of our galaxy appear fainter than it does in summer. Our eyes can only see the pale streak it makes across the sky, but a high-powered telescope can see the brilliant and colorful objects that lie within. Studying these images help us understand the different stages of a star's life cycle, from how stars are born to how nature recycles the leftover gas from a dying star to form new star nurseries. Our galaxy is forever changing and these images allow us to understand some of the mystery that still remains about our Milky Way.

Image of Winter Deep-Sky objects that are visible from the Southern Hemisphere.
Winter Deep-Sky objects that are visible from the Southern Hemisphere

Image of Winter Deep-Sky objects that are visible from the Northern Hemisphere.
Winter Deep-Sky objects that are visible from the Northern Hemisphere

Click here to see all of the students’ images, reminding us that nature is not only awe-inspiring but the perfect intersection of art and science.
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Monday, April 7, 2014

Mars Opposition

If you have never seen the red planet Mars through a telescope and would like to do so, then there is no better time than when the planet reaches opposition. Why is this so important? Simply because Mars will be closer to the Earth, and this means that Mars will appear larger when viewed or imaged through telescopes. A larger planet presents better opportunities for viewing small features that are usually hard to see: polar caps become easily visible, and larger features like Syrtis Major have more clarity and structure is easier to discern.

 Mars Imaged by Michael Petrasko on 10-02-2005 with a C11 SCT and Celestron NexImage Planetary Camera
Mars Imaged by Michael Petrasko on 10-02-2005 with a C11 SCT
 and Celestron NexImage  Planetary Camera

Luckily this spring Mars will reach opposition on April 8, 2014. So now's your chance to take advantage of this opportune moment. Keep in mind, however, that Mars still appears fairly small in scopes (when compared to the likes of Jupiter or Saturn, that is). We have had the opportunity to observe and image Mars ourselves many times in the past from our backyard remote robotic telescopes and it has always been a fascinating object... Viewing the surface of another planet does wonder in stirring up the imagination! Find out for yourself what Percival Lowell and Carl Sagan found so alluring about our red neighbor. 
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Sunday, April 6, 2014

April 2014 Lunar Eclipse

A total lunar eclipse will take place on April 15, 2014. It will be the first of two total lunar eclipses in 2014, and the first of four total lunar eclipses this year. the lunar eclipse will be visible in the Pacific Ocean region, including Australia, as well as North and South America. The moon will pass south of the center of the Earth's shadow. As a result, the northern part of the moon will be darker than the southern part.

Simulation of the moon passing through Earth's shadow.
Simulation of the moon passing through Earth's shadow.

A lunar eclipse occurs when the Moon passes within Earth's umbra (shadow). As the eclipse begins, the Earth's shadow first darkens the moon slightly. Then, the shadow begins to "cover" part of the moon, turning it a dark red-brown color. The moon appears to be reddish due to the refraction of light through the Earth's atmosphere. This is the same effect that causes sunsets to appear red.

Oftentimes, the full moon appears coppery red during a total lunar eclipse because the dispersed light from all the Earth’s sunrises and sunsets fall on the face of the moon. Thus the term Blood Moon can be and is applied to any and all total lunar eclipses.

The simulation above displays the approximate appearance of the moon passing through the earth's shadow. The moon's brightness is exaggerated within the umbral shadow. The northern portion of the moon will be closest to the center of the shadow, making is darkest and most red in appearance.

On April 15, 2014, the moon will pass through the southern part of the Earth's umbral shadow. It will be visible over most of the Western Hemisphere including east Australia, New Zealand, the Pacific ocean, and North and South America. In the western Pacific, the first half of the eclipse will occur before moonrise. In Europe and Africa, the eclipse will begin just before moonset. In North America, Mars will arguably be the most prominent object in the sky other than the moon, appearing 9.5° northwest of the moon. The bright star Spica will be 2° to the west, while Arcturus will be 32° north. Saturn will be 26° east and Antares 44° southeast.

Oftentimes, the full moon appears coppery red during   a total lunar eclipse because of the dispersed light from all the Earth’s sunrises and sunsets fall on the face of the moon. Thus the term Blood Moon can be and is applied to any< and all total lunar eclipses.
Oftentimes, the full moon appears coppery red during
 a total lunar eclipse because of the dispersed light from all
the Earth’s sunrises and sunsets fall on the face of the moon.
Thus the term Blood Moon can be and is applied to any<
and all total lunar eclipses. 

The moon will enter Earth's penumbral shadow at 4:54 UTC and the umbral shadow at 5:58. Totality will last for 1 hour 18 minutes, from 7:07 to 8:25. The moment of greatest eclipse will occur at 7:47. At that point, the Moon's zenith will be approximately 1,900 miles southwest of the Galapagos Islands. The moon will leave the umbral shadow at 9:33 and the penumbral shadow at 10:38.

The umbral magnitude will peak at 1.2907. At that moment, the northern part of the moon will pass 1.7 arc-minutes south of the center of Earth's shadow, while the southern part will be 40.0 arc-minutes from the center. Thus, the northern part of the moon will be noticeably darker. The moon's appearance will change significantly throughout the eclipse as the depth of the shadow changes.
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Wednesday, April 2, 2014

Galaxies 101 - A Primer to the Types of Island Universes

Spring is the time of year where our night sky is enriched with a plethora of galaxy types. On a dark night, we can often see a "hazy" band of light that stretches across the sky. This band is the part of own Milky Way galaxy, a gigantic collection of stars, gas, and dust. Far beyond the Milky Way, there are billions of other galaxies, some similar to our own and some very different, scattered throughout space to the very limits of the observable universe.

M101 - Spiral Galaxy in Ursa Major Imaged on T11 by Michael Petrasko and Muir Evenden
M101 - Spiral Galaxy in Ursa Major Imaged on T11 by Michael Petrasko and Muir Evenden

Types of Galaxies:

Astronomers classify galaxies into three major categories. Spiral galaxies look like flat disks with bulges in their centers and beautiful spiral arms. Elliptical galaxies are redder, more rounded, and often longer in one direction than in the other, like a football. Galaxies that appear neither disk-like nor rounded are classified as irregular galaxies.

Spiral Galaxies:

Spiral galaxies usually consist of three components: a flat disk, an ellipse-shaped formed a bulge and a halo. The disk contains a lot of interstellar gas and dust, and most of the stars in the galaxy. The gas, dust, and stars in the disk rotate in the same direction around the galactic center at hundreds of kilometers per second and are often arranged in striking spiral patterns. The bulge is located at the center of the disk and consists of an older stellar population with little interstellar matter. The near-spherical halo surrounds the disk and is thought to contain copious amounts of dark matter: matter that acts gravitationally like "normal" matter but that can't be seen! Astronomers infer the presence of this dark matter by the motions of stars and gas in the disk of the galaxy, as well as older stellar populations in the halo-like globular clusters. The young stars in the disk are classified as a stellar population I, and the old bulge and halo stars as population II.

M104 - "Sombrero Galaxy" in Virgo - Image was taken on  iTelescope.com's T21 by Sam P. and Tom M. from PCIS.
M104 - "Sombrero Galaxy" in Virgo - Image was taken on  iTelescope.com's T21 by Sam P. and Tom M. from PCIS.

Astronomers classify spiral galaxies according to their appearance by using the Hubble scheme. Those with pronounced bar structures in their centers are called "barred spirals" and are classified "SB" (examples are given in brackets). Galaxies with conspicuous bulges and tightly wound spiral arms are called "Sa" (Sombrero galaxy) or "SBa" (NGC 3185). Galaxies with prominent bulges and pronounced spiral arms are classified as "Sb" (M31, M81) or "SBb" (M95, NGC 4725). Other spirals with loose spiral arms and a small bulge are classified as "Sc" (M33, M74, M100) or "SBc" (M83, M109).

There are some galaxies like M84, M85 and NGC 5866 that are disk galaxies without any spiral structure. These galaxies are called "S0" or lenticular galaxies. Though the origin of lenticular galaxies is still debated the most plausible explanation to date is that the gas and stars that would reside in the galaxy disk have been stripped by interactions with the hot gas in clusters and groups of galaxies. From their appearance and their stellar contents, they look more like ellipticals rather than spirals and have often been misclassified due to this fact. For instance, misclassification has occurred for both the Messier object examples listed above.

Elliptical Galaxies:

Elliptical galaxies are ellipsoidal agglomerations of stars, which usually do not contain much interstellar matter. Photometric studies of elliptical galaxies suggest that they are triaxial (all the three axes of the ellipsoid are of different sizes). Unlike spiral galaxies, ellipticals have little or no global angular momentum, so that different stars orbit the center in different directions and there is no pattern of orderly rotation. Normally, elliptical galaxies contain very little or no interstellar gas and dust and consist of old population II stars only. Elliptical galaxies are classified according to the Hubble scheme into classes "E0" to "E7", in increasing order of ellipticity. Thus E0 galaxies appear round like M89 while E6 galaxies like M110 and NGC 3377 are almost cigar-shaped.

The largest galaxies in the universe are giant elliptical galaxies. They contain a trillion stars or more and span as much as two million light-years - about 20 times the width of the Milky Way. These giant ellipticals are often found in the hearts of galaxy clusters. For example, the giant elliptical galaxy M87 is found in the heart of the Virgo Cluster.

Elliptical galaxies also constitute some of the smallest galaxies in the universe. These galaxies are called dwarf elliptical galaxies and dwarf spheroids. Relative to normal ellipticals they are very faint and are often found in galaxy clusters or near large spiral galaxies. For instance, there are 9 dwarf spheroids like Leo I which are satellites of our Milky Way galaxy.

Small Magellanic Cloud - Imaged with iTelescope.com's T12 by Michael Petrasko
Small Magellanic Cloud - Imaged with iTelescope.com's T12 by Michael Petrasko

Irregular Galaxies:

A small percentage of the large galaxies we see nearby fall into neither of the two major categories. This irregular class of galaxies is a miscellaneous class, comprising small galaxies with no identifiable form like the Magellanic clouds (the Large Magellanic Cloud and Small Magellanic Cloud are two satellite galaxies of the Milky Way) and "peculiar" galaxies that appear to be in disarray like NGC 1313. There is no discernable disk in these systems, although they often have copious amounts of gas as well as high rates of star formation. Irregular galaxies are often found to be gravitationally interacting with galaxies nearby, which often accounts for their ragged appearance.
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