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ECLIPSE

NEWSLETTER

The Eclipse Newsletter is dedicated to increasing the knowledge of Astronomy, Astrophysics, Cosmology and related subjects.

VOLUMN 2 NUMBER 1

JANUARY – FEBRUARY 2018

PLEASE SEND ALL PHOTOS, QUESTIONS AND REQUST FOR ARTICLES TO pestrattonmcag@gmail.com

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MCAO PUBLIC NIGHTS AND FAMILY NIGHTS. The general public and MCAO members are invited to visit the Observatory on select

Monday evenings at 8PM for Public Night programs. These programs include discussions and illustrated talks on astronomy, planetarium programs and offer the

opportunity to view the planets, moon and other objects through the telescope, weather permitting. Due to limited parking and seating at the observatory, admission is by

reservation only. Public Night attendance is limited to adults and students 5th grade and above. If you are

interested in making reservations for a public night, you can contact us by calling 302-654-6407 between the hours of 9 am and 1 pm Monday through Friday. Or you can email us any time at KimGreenmcao@gmail.com or mtcuba@physics.udel.edu. The public nights will be presented even if the weather does not permit observation through the telescope. The admission fees are $3 for adults and $2 for children. There is no admission cost for MCAO members, but reservations are still required. If you are interested in becoming a MCAO member, please see the link for membership. We also offer family memberships.

Family Nights are scheduled from late spring to early fall on Friday nights at 8:30PM. These programs are opportunities for families with younger children to see and learn about astronomy by looking at and enjoying the sky and its wonders. It is meant to teach young

children from ages 6-12 about astronomy in simple terms they can really understand. Reservations are required and admission fees are $3 for adults and $2 for children.

MCAO WEB SITE IS mountcuba.org

CONTENTS:

HAVE YOU EVER ASKED?

ASTRONOMICAL TERMS:

UPCOMING DAS STAR PARTIES

METEOR SHOWERS

SUN HALOS

HOW MANY GALAZIES IN THE UNIVERSE?

OUR MILKY WAY GALAXY

HOW TO FIND CONSTELLATIONS. THIS EDITIONS CONSTALLATION. WHAT ARE THE MESSIER OBJECTS?

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HAVE YOU EVER ASKED?

What is a lightyear?

A light-year is how astronomers measure distance in space. It’s defined by how far a beam of light travels in one year – a distance of six trillion miles. Think of it as the bigger, bolder cousin of the inch, the mile, the kilometer, and the furlong. If you like to keep up with what’s going on in astronomy, it’s worth spending a little bit of time understanding what the deal is with this funny unit of measurement.

Take a minute and have some fun. Google each object above and learn more.

How to change lightyears to miles.

https://www.calculateme.com/Astronomy/LightYears/ToMiles.htm

What is Fusion in Science?

Fusion is the process that powers the sun and the stars. It is the reaction in which two atoms of hydrogen combine together, or fuse, to form an atom of helium. In the process some of the mass of the hydrogen is converted into energy.

What is a Qurak?

A quark is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. The name "quark" was taken by Murray Gell-Mann from the book "Finnegan's Wake" by James Joyce. The line "Three quarks for Muster Mark..." appears in the fanciful book. Gell-Mann received the 1969 Nobel Prize for his work in classifying elementary particles.

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ASTRONOMICAL TERMS

celestial equator - The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth's equator. In other words, it is a projection of the terrestrial equator out into space. As a result of the Earth's axial tilt, the celestial equator is inclined by 23.4° with respect to the ecliptic plane.

UPCOMING DAS STAR PARTIES

For more information on DAS STAR PARTIES, visit the mountcuba.org web site. Select Delaware Astronomical Society DAS.

Select Events at top and then STAR PARTIES.

METEOR SHOWERS

All meteor shower listed below are the easiest to observe and provide the most activity. Particular attention should be noted to the time and moonlight conditions. All these showers are best seen after midnight. Some are not even visible until after midnight. Showers that peak with the moon’s phase greater than one half illuminated (first quarter to last quarter) will be affected

by moonlight and difficult to observe. While the time each shower is best seen remains much the same year after year, the moonlight conditions change considerably from one year to the next. As we approach the date of each shower's maximum, be sure to consult the latest AMS article about Meteor Showers, which will provide in depth information on each shower and how to best view

it. Quadrantids Active from January 1st to January 10th The Quadrantids have the potential to be the strongest shower of the year but usually fall short due to the short length of maximum activity (6 hours) and the poor weather experienced during early January. The average hourly rates one can expect under dark skies is 25. These meteors

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usually lack persistent trains but often produce bright fireballs. Due to the high northerly declination (celestial latitude) these meteors are not well seen from the southern hemisphere.

Radiant: 15:18 +49.5° - ZHR: 120 - Velocity: 26 miles/sec (medium - 42.2km/sec) - Parent Object:

2003 EH (Asteroid) Radiant = Point of origin. ZHR = In astronomy, the Zenithal Hourly Rate (ZHR) of a meteor shower is the number of meteors a single observer would see in an hour of peak activity. Velocity = Average speed of an Asteroid is 25 km/sec. Average speed of these is much faster.

SUN HALOS

Halo is the name for a family of optical phenomena produced by light interacting with ice crystals suspended in the atmosphere. Halos can have many forms, ranging from colored or white rings to arcs and spots in the sky. Many of these are near the Sun or Moon, but others occur elsewhere or even in the opposite part of the sky. Among the best known halo types are the circular halo (properly called the 22° halo), light pillars and sun dogs, but there are many more; some of them fairly common, others (extremely) rare.

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The ice crystals responsible for halos are typically suspended in cirrus or cirrostratus clouds high (5–10 km, or 3–6 miles) in the upper troposphere, but in cold weather they can also float near the ground, in which case they are referred to as diamond dust. The particular shape and orientation of the crystals are responsible for the type of halo observed. Light is reflected and refracted by the ice crystals and may split up into colors because of dispersion. The crystals behave like prisms and mirrors, refracting and reflecting light between their faces, sending shafts of light in particular directions.

Atmospheric phenomena such as halos were used as part of weather lore as an empirical means of weather forecasting before meteorology was developed. They often do mean that rain is going to fall within the next 24 hours as the cirrostratus clouds that cause them can signify an approaching frontal system.

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HOW MANY GALAXIES IN THE UNIVERSE? According to the best estimates of astronomers there are at least TWO hundred billion galaxies in the observable universe. They've counted the galaxies in a particular region, and multiplied this up to estimate the number for the whole universe.

How do we know how many galaxies are in our universe?

According to the best estimates of astronomers there are at least one hundred billion galaxies in the observable universe. They’ve counted the galaxies in a particular region, and multiplied this up to estimate the number for the whole universe.

Astronomers get to travel to some of the most remote places on Earth to use huge optical telescopes far away from light pollution in order to make observations. Optical telescopes have been used for astronomical observation since the time of Galileo, but the technology has moved on significantly since then.

Twinkle Twinkle Little Star

Twinkling stars may be pretty and romantic, but this distortion of the starlight by changes in temperature and wind speed as it travels through the atmosphere has been the bane of astronomers’ lives. Fortunately, adaptive optics can now compensate for the twinkles. By shining a laser in to the night sky, the path the star light takes to reach the telescope can be found more accurately. And a rapidly tilting mirror to adjust the light coming into the telescope makes the image much clearer.

Telescopes in space

A simpler way to overcome the atmospheric distortions is to put your telescope above the atmosphere. The Hubble Space Telescope orbits 600 km above the Earth and has been sending back the most amazing images of our universe since 1993.

In 2013, NASA, the European Space Agency and the Canadian Space Agency are due to launch the James Webb Space Telescope (JWST) to replace Hubble. The JWST will look at how the universe began and how galaxies are formed, but in order to do this it won’t use visible light to produce images. Unlike Hubble it will use infrared light.

By being sensitive to infrared light, the JWST will be able to detect objects hidden behind dust clouds and galaxies that are moving away from us at such speeds that their light has been red-shifted out of the visible region of the electromagnetic spectrum.

OUR MILKY WAY GALAXY

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Basic plan of the Milky Way

Submitted by Kevin Jardine For Kevin’s Blog

http://galaxymap.org/drupal/?q=blog/1

This artist's concept depicts the most up-to-date information about the shape of our own Milky Way galaxy. We live around a star, our sun, located about two-thirds of the way out from the center. This concept shows two arms and not four causing quite a bit of discussion and controversy.

Credits: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

It is easy to drown in the details of any map, so it is useful to start with a basic plan of the Milky Way. Those who want a more detailed (although less complete) map can visit the Face-on map overview.

The following is one of the best as well as prettiest basic plans. It includes the Sagittarius arm and the Perseus arm but adds five additional arms two of which not being considered major arms. It does includes the Orion Spur where our Sun is located.

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Hurt's illustration was created to highlight scientific conclusions on the inner galaxy from a team of astronomers led by Robert Benjamin and associated with the Spitzer infrared space telescope. However, there are so few well done images of the Milky Way available that the illustration has been widely used in scientific papers, even by researchers who vehemently disagree with some of the Spitzer team's basic conclusions.

I've blogged about some problems with the Hurt illustration, including details in the Orion spur and outer galaxy. Fortunately, there are other illustrations available that correct these problems and I'll mention one below.

Orientation

One other problem with the original Hurt illustration is that it is upside down. The standard orientation for Milky Way face-on maps in scientific publications (and this site) has 0° galactic longitude (the direction to the galactic nucleus) facing downwards. Hurt's illustration has it

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facing upwards. There is nothing scientifically invalid about this orientation (it is completely arbitrary) but it is still rather confusing. It's a bit like a map of the world with Antarctica at the top. This has some novelty value but is probably not the best orientation to use for general education. So the version I'm using is rotated into the standard view.

Spiral arms

Hurt's illustration shows a barred spiral galaxy with two major arms. Even this basic design is controversial because many astronomers argue that the Milky Way has four major arms. Hurt has put the other arms into his illustration as well but deemphasized them.

Unfortunately, astronomers agree on the name of only one of these arms. This is called the Perseus arm and was discovered in the 1950s. It is the spiral arm that one sees first when looking into the outer galaxy (180°). As one might expect, it is most obvious at visual frequencies from the Earth in the direction of the constellations Perseus and Cassiopeia.

The other arms have been treated a bit like those roads in European cities that change their names every few blocks. The other major arm in Hurt's illustration runs through the southern constellations Scutum, Crux and Centaurus (among others) as viewed from Earth so in the scientific literature it can be called the Scutum-Crux arm, the Scutum-Centaurus arm, the Crux-Centaurus arm, the Crux-Scutum arm, the Scutum arm, the Crux arm, the Centaurus arm, and even the Scutum-Crux-Centaurus arm. As Centaurus is by far the largest of the three constellations, I strongly favor the use of the term "Centaurus arm" and try to use that name as much as possible in this website.

Many astronomers believe that the Milky Way has four major spiral arms and this is certainly what appears in the atomic hydrogen data as I describe in the chapter on kinematic distance

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estimates. Others argue that the third and fourth "arms" consist of a few discontinuous active segments and are not full spiral arms in the same sense as the Perseus and Centaurus arms. Some argue that the number of arms depends upon the frequency of light and the type of objects. For example, the Spitzer infrared astronomers favor a two-major arm model because red giant stars (which emit a lot of infrared) are largely confined to the Perseus and Centaurus arms, whereas radio astronomers tend to favor a four-major arm model because radio telescopes can detect atomic hydrogen in all four arms. Some references for this debate are supplied in my Four arms vs. two blog entry.

In any case, it is still possible to give the third and fourth arms names and describe their positions. More data is required to determine if they are as fully developed as the Perseus and Centaurus arms.

The third arm can be seen in the direction of the constellations Sagittarius and Carina (and so is sometimes called the Sagittarius arm, the Carina arm, the Sagittarius-Carina arm or the Carina-Sagittarius arm).

The fourth arm can be seen in the direction of the constellations Norma and Cygnus and so is sometimes called the Norma-Cygnus arm, the Cygnus-Norma arm, the Norma arm, or the Cygnus arm. The term "Outer arm" is used more often than any of the other names for this arm. This makes sense most of the time, but confusingly, the section of this arm visible in Norma is actually in the inner galaxy close to the galactic bar.

Hurt's illustration shows the Centaurus and Norma/Outer arms starting at the nearest end of the central bar to our solar system. The Perseus and Sagittarius arms start at the far end of the bar. When examining other barred spiral galaxies, we can see that major spiral arms often (but not always) begin at the ends of the bars.

In addition to these major arms, there are several other arms described in the section on the galactic bar below.

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Arcs

Spiral arms are not continuous structures but are divided into active star-forming sections surrounded by less active sections composed of diffuse gas and dust. It is often useful to refer to specific active parts of spiral arms. In this website, I use the term "arc" to refer to these active sections. This includes the Cassiopeia arc (Perseus arm), Monoceros arc (Outer arm), the Carina arc (Sagittarius arm) and many others.

I will use the term "arm" only when referring to one of the major spiral arms as a whole.

This image shows the four galactic quadrants (centered on the Sun) and details of the Orion spur. (Based upon an illustration by Diana Marques.)

The disk

The spiral arms in many spiral galaxies (including the Milky Way) are confined within a thin disk.

The thin disk of the Milky Way makes it possible to present the spiral arms in a two-dimensional map. In reality spiral arms are 3-dimensional structures but over a large area objects within them can have their positions represented approximately on a flat map.

Astronomers have divided the disk into four quadrants, usually designated by Roman numerals. Unlike the Alpha, Beta, Gamma and Delta quadrants of the Star Trek mythos, the first, second, third and fourth galactic quadrants are centered on the Sun rather than the galactic nucleus. This is less aesthetically pleasing but more practical scientifically as almost nothing is known about objects on the far side of the galactic nucleus.

The bar

The central bar has a thicker bulge made up of mostly older stars.

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The bar of the Milky Way is tightly wrapped by two additional structures called the near and far 3kpc arms. (This is short for 3000 parsecs because these arms are located approximately 3000 parsecs from the center of the galaxy in a line drawn from the Sun.) Note that the 3kpc arms are distinct from the 4 arms I mentioned in the spiral arms section above.

The bar itself has a complex structure including an inner bar, a molecular hydrogen ring, two miniature bar spiral arms (internal to the bar and distinct from the 3kpc arms), a central molecular zone and at the heart of the galaxy, the 4 million solar mass black hole Sgr A*.

The halo

The Milky Way (like other spiral galaxies) is surrounded by a large halo region which contains globular clusters, large clouds of hydrogen gas, and a huge mass of the mysterious dark matter.

This detailed image shows the major known components of the Orion spur and the location of the Sun (yellow dot). (Based upon an illustration by Diana Marques.)

Orion spur

Our Sun is located within the Orion spur. Although not a spiral arm, the Orion spur is nevertheless a major Milky Way structure that crosses the Perseus arm, linking the Sagittarius and Outer arms.

Such spurs connecting two or more spiral arms are a common feature of spiral galaxies.

The Orion spur is sometimes confusingly called the Orion arm or the Local arm in scientific papers. I will try to avoid that confusion in this website.

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The Hurt illustration does not represent the Orion spur very accurately and so instead I am using an image created by scientific illustrator Diana Marques that better represents the region of the Milky Way close to the Sun.

The Orion spur appears to branch off from the Sagittarius arm at or near the intense radio source W51, which is a large complex of star formation regions and supernova remnants.

It continues through the Cygnus X complex of star formation regions, which includes Cyg OB2, one of the most luminous OB associations known in the local group of galaxies. It passes through the Rift dust clouds and into an expanding ring of bright star formation regions called the Gould belt. The Gould belt includes the Orion molecular cloud and our own Sun (which is much older than the Gould belt and is just passing through).

The Gum nebula supernova remnant dominates the Orion spur just past the Gould belt. Beyond the Gum nebula, the spur forks. The main branch transits the Perseus arm in the direction of the constellation Canis Major and terminates in or near the Outer arm. A smaller branch forms the complex of molecular clouds and star formation regions called the Vela Molecular Ridge.

Perhaps not surprisingly, the scientifically most controversial bits of this description of the Orion spur are in regard to its ends. The Russian astronomer Veta Avedisova tentatively suggested an origin in W51 in a 1985 paper which states: "W51 may well belong to the local arm ... One also cannot rule out that the main arm might split somewhere in the vicinity of W51". This view is also supported by a 2010 paper, which more specifically gives the origin as the infrared source W51 IRS2.

On the other hand, a 2008 paper argues for a closer origin for the Orion spur in the vicinity of the infrared source G59.7+0.1 (IRAS 19410+2336), which is associated with the star cluster NGC 6823 and the nebula Sh 2-86. (This spectacular object has been imaged by both the Spitzer and Herschel infrared space telescopes.)

The author lists of the 2008 and 2010 papers referenced in the last two paragraphs overlap, suggesting that either these authors disagree amongst themselves or that opinion has shifted back towards a W51 origin for the Orion spur in the later paper.

The Perseus transit at the other end of the Orion spur is described in a major 2008 survey paper on the structure of the Milky Way in the third quadrant.

This Chandra image shows the hot x-ray halo surrounding the massive spiral galaxy NGC 5746. It also shows an optical view of the galaxy including the central bulge and thin disk. The Milky Way has a similar basic structure if viewed edge-on.

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HOW TO FIND CONSTELLATIONS Step 1. Purchase a Star Chart as shown below. Mt. Cuba Astronomical Observatory sells

this one for $4.00.

Step 2. Get acquainted with the Star Chart. You will notice there are two sides to the chart. One side is for viewing the sky to the North while the other side is for viewing to the South. Let’s start with the side for the North. You will notice that the white part of the chart rotates. At the bottom of the white part, you will see months. Above the month is the date. On the blue part you will see times from 7 p.m. to 6 a.m. Select the month and date you are using the Chart. Rotate them to the time of day you are viewing. 3. Face North and look at the chart to pick out the object you want to find then look up at the sky. Compare the stars on the star chart and the stars you see in the night sky. 4. To view South, turn the chart over, face South and repeat above.

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THIS EDITIONS CONSTALLATION. ORION

Orion, which is located on the celestial equator, is one of the most prominent and recognizable constellations in the sky and can be seen throughout the world. Orion is the brightest and most beautiful of the winter constellations. Some of its stars, including Betelgeuse and Rigel, are among the brightest stars.

To find Orion in early January, look due south about 11:30 p.m. Locate the three stars in a straight line. Once done, you can begin to observe. You may want to first locate Betelgeuse which is also designated Alpha Orionis, is the ninth-brightest star in the night sky and second-brightest in the constellation of Orion. Betelgeuse is well-known because of its bright size and easy-to-spot location in the constellation Orion. It is of astronomical interest because it will likely go supernova in less than a million years.

Look next for Rigel. Rigel is around 800 light years from Earth and is the brightest star in the constellation of Orion. Rigel is actually a three-star system consisting of the blue supergiant Rigel A and two distant and much dimmer companions. Even though much of Rigel's energy is emitted as invisible ultraviolet light it is still around 40,000 times brighter than the sun.

Last. But not least is the Horsehead Nebula.

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If you recall, a Nebula is the birthplace od Stars. Go back to Orion’s belt and find Alintak. Just below Alintak is the Nebula.

WHAT ARE THE MESSIER OBJECTS?

The Messier objects are a set of over 100 astronomical objects first listed by French astronomer Charles Messier in 1771.[1] Messier was a comet hunter, and was frustrated by objects which resembled but were not comets, so he compiled a list of them,[2] in collaboration with his assistant Pierre Méchain, to avoid wasting time on them. The number of objects in the lists he published reached 103, but a few more thought to have been observed by Messier have been added by other astronomers over the years.

For a list of Messier objects:

https://en.wikipedia.org/wiki/List of Messier objects

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THIS ISSUES MESSIER OBJECT.

M57 THE RING NEBULA

The Ring Nebula is about 2,000 light-years from Earth and measures roughly 1 light-year across. Located in the constellation Lyra, the nebula is a popular target for amateur astronomers. Previous observations by several telescopes had detected the gaseous material in the ring's central region. But the new view by Hubble's sharp-eyed Wide Field Camera 3 shows the nebula's structure in more detail. O'Dell's team suggests the ring wraps around a blue, football-shaped structure. Each end of the structure protrudes out of opposite sides of the ring.

Discovered by Charles Messier on January 31, 1779. Observed by Antoine Darquier de Pellepoix in February 1779.

The famous ring nebula Messier 57 (M57, NGC 6720) is often regarded as the prototype of a planetary nebula, and a showpiece in the northern hemisphere summer sky.

Recent research has confirmed that it is, most probably, actually a ring (torus) of bright light-emitting material surrounding its central star, and not a spherical (or ellipsoidal) shell, thus coinciding with an early assumption by John Herschel. Viewed from this equatorial plane, it would thus more resemble the Dumbbell Nebula M27 or the Little Dumbbell Nebula M76 than its appearance we know from here: We happen to view it from near one pole.

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