Galaxies

May 30, 2021

Springtime for Galaxies — Lookout Observatory

Dear Lookout Observers,

Our landscape varies with the season. So we get sayings like, “April showers bring May flowers.” But when the whole western United States is in a serious multiyear drought, we may have limited flowers. Our “skyscape” also varies with the season, but it is not affected by droughts. The night sky reliably brings us galaxies every spring. This occurs because from mid-northern latitudes in the springtime the North Galactic Pole is high in the sky to the south most of the night. When you are looking in that direction, you are looking perpendicular to the plane of the Milky Way galaxy. This means you will not see the Milky Way with all it’s stars and glowing gasses in the spring sky, but you also will not be looking through all the obscuring dust that lies throughout much of our galaxy, so you will have a clear view out to distant other galaxies.

Imagine our galaxy is like a dinner plate sitting on a dining room table with a steaming meal spread all across the plate. If you were a small creature in the middle of that steaming meal, and you tried to look at a spider on the wall at table height, you would have a hard time seeing it because of all the steam rising from the meal that you would be trying to look through. But if you looked straight up at a spider on the ceiling overhead, you would have a clear view with little steam to block your view. That’s like looking up toward the North Galactic Pole. That spot is in the constellation Coma Berenices, and the constellation Virgo is just south of there. Some of the largest clusters of galaxies in the universe lie in the direction of Coma Berenices and Virgo, and these and other groups of galaxies are well placed for viewing on spring nights. We can see them without all the dust in our own galaxy getting in the way.

About 16 degrees south of the North Galactic Pole lie two spiral galaxies in Virgo that are just beginning to collide, centered in the first picture. The upper, bluer one (NGC4567) is just bout face on, while the lower, pinker one (NGC4568) is turned at an angle. We can tell they have not fully collided yet because both spirals are still quite symmetrical and undisturbed. Once galaxies interact, they usually become quite distorted. Near the top center of the picture is an elliptical galaxy (NGC4564), and near the bottom center is a dwarf lenticular galaxy (IC3578), and if you look closely you will find many other galaxies (looking like tiny fuzzy spots slightly larger than stars of the same brightness) scattered across the image. Most of these galaxies belong to the Virgo Cluster of galaxies, about 50 to 70 million light years away and containing 1000 to 2000 members.

The second picture is of a galaxy about 24 degrees southwest of the North Galactic Pole in the neighboring constellation of Leo. NGC3628 is a spiral galaxy seen edge on with much obscuring dust and gas along its center line, much like our own Milky Way. It is about 35 million light years distant, or roughly half the distance of the galaxies in the first photo and about twice as large as the largest galaxy in the first photo. It is about the same size of our own Milky Way galaxy. It is a member of a small group of galaxies, including M65 and M66, which lie outside this picture. It shows evidence of past (almost a billion years ago) interaction with another group member because of the disrupted right portion of the central dust lane being split into multiple branches and the extended envelope of brightness around the main parts of the galaxy, suggesting tidal disruption. A very faint dwarf companion galaxy (HKK2009 dJ1120+1332, discovered in 2009) can be seen as a vertical smudge just a bit below the center of this galaxy.

The last picture is of another spring galaxy, M108, that is about 33 degrees northwest of the North Galactic Pole, just below the bowl of the Big Dipper. It is a nearly on edge spiral galaxy with loosely wound spiral arms – in fact, so loose that it is hard to make out the spiral structure in the arms. But it has pretty colors and an interesting structure of dust lanes, so it seemed a good one to end on. Each of these pictures shows galaxies that belong to a different grouping, and our own Milky Way belongs to yet a fourth group called the Local Group. But just as human groups all have larger groups they belong to, all four of these galaxy groups are part of the Virgo Supercluster, a huge gathering of dozens of galaxy groups and clusters about 100 million light years across, all traveling through space together. Wouldn’t it be lovely if all our human groups could also learn to travel together?

Keep looking up,

Carter, (sometime) Resident Astronomer,

Lookout Observatory

Click on any image to get a closer look

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Four galaxies – NGC4567 NGC4568 NGC4564 & IC3578

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Spiral galaxy NGC3628 & dwarf companion galaxy HKK2009 dJ1120+1332

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Spiral galaxy M108

March 30, 2021

Galaxies 0

Galaxies under the Big Dipper’s Handle

Dear Friend,

Due to the coronavirus restrictions, I have not been able to do much astrophotography, so I have not sent out a Lookout Observatory email for over 5 months. I have been entertaining myself at home by practicing my processing skills on old pictures, and I realized I could share some older photos that didn’t seem good enough to send out before, but look better reprocessed with newly acquired skills. So here are pictures of two galaxies that I took between 2 and 9 years ago.

Image 1: So you can know where these galaxies are located in the sky, the first picture is of a 25° x 35° rectangular area of the sky around the Big Dipper, with green lines to help you see the star pattern. The small blue rectangle below the end of the Dipper’s handle is the area of sky in the next picture. And 5° below that, at the location of the blue X,is the location of the very last picture.

Image 2: This small (about 1½° x 2°) area of the sky has at its very center one of the most famous galaxies in the sky – the Whirlpool galaxy, or M51. This object was first observed by Charles Messier (hence the “M” in M51) in 1773. He called it a nebula because in his telescope it just looked like a small fuzzy spot. It was about another 70 years until telescopes improved enough that the spiral structure could be observed. And it was almost another 70 years until it became known that spiral structures like this were not gaseous nebulae in our galaxy, but entire galaxies themselves millions of light years outside of our Milky Way galaxy. This one is relatively close at about 25 million light years. But part of what makes M51 so interesting is what looks like a bright lump at the end of one of the spiral arms. It has its own designation as NGC 5195, and it is actually a separate galaxy.

Image 3: The third picture is a much closer view of M51 and NGC 5195, an irregular galaxy. Sometimes two galaxies that appear close are really very far apart, but by chance lie along the same line of sight. In other cases they are actually very close, and they interact. That is the case here, and the smaller galaxy is clearly distorting a spiral arm from M51. In fact, it is believed that tidal forces from the smaller galaxy have strongly enhanced the spiral structure of M51. Because dust from M51’s distorted arm looks to be covering the left half of NGC 5195, it is believed that the smaller galaxy is slightly behind M51. Interactions between these two galaxies are partly responsible for the many areas of active star formation in hydrogen gas and dust exhibited in the reddish areas. The blue areas are where young hot stars have already formed, and the yellowish areas (near the centers of each galaxy) contain older stars.

Image 4: This is the spiral galaxy M63, believed to be gravitationally connected to M51, even though they are several million light years apart. Because M63 doesn’t have large-scale continuous spirals, but rather many more loosely wound, discontinuous arms, it is called a flocculent spiral galaxy. It is nicknamed the Sunflower galaxy. This image is at the same scale as the previous one, so you can see that M63 is about the same apparent size as M51 and NGC 5195 taken together. Since they are approximately the same distance from our Milky Way, they are roughly the same actual size. But their appearance is quite different, just three of the many varieties of galaxies scattered across our universe.

However difficult the times may be, keep looking up,

Carter, (sometime) Resident Astronomer,

Lookout Observatory

Click on any image to get a closer look

Sky around the Big Dipper

The Whirlpool Galaxy aka M51

M51 and NGC 5195

Spiral galaxy M63 nicknamed the Sunflower galaxy

April 17, 2020

Galaxies, Nebulae 0

More Animals from Lookout Observatory

Dear Lookout Observer,

With much of the world staying at home and keeping a distance from others due to the coronavirus pandemic, it seems we can all use a diversion from our immediate stressors. So to get away from worldly cares, please let me take you up to 30 million light years away. In our last report we looked at 3 animals in the sky. This time it’s a challenge: can you match 6 more animal pictures with each object’s description?

Some of these might be easy because you may have seen them before, especially if you are a long time recipient of these reports. But some might be difficult because astronomers, both ancient and modern, have always had to stretch their imaginations to find meaningful shapes in random sprinkles of stars (called constellations) or fuzzy patches of light in a telescope (nebulae and galaxies). So you might be hard pressed to see the named animal in some of these pictures. But if you can’t figure it out, just ask a friendly 4 to 8 year old. They are usually much better at seeing animals in clouds – or celestial wonders – than adults are.

Happy matching, Carter, Your Lookout Astronomer

A. Eagle First up is the Eagle Nebula located in the constellation of Serpens Cauda (the serpent’s tail). It is a huge emission nebula (dozens of light years across) of glowing gas and dust with an embedded cluster of thousands of stars. A small part of the nebula which is a region of active star formation was made famous as a Hubble telescope image. The full extent of this nebula covers an area of sky about the size of the full moon. It is a typical emission nebula consisting mostly of hydrogen gas energized to glow red from the energy of embedded stars, and containing dark areas where dust obscures the glowing gas.

B.Swan The Swan Nebula is another huge (15 light years across) emission nebula in the constellation Serpens Cauda. It also has a large cluster of embedded stars, with many more in the process of forming. It occupies an area of the sky about ½ the diameter of the full moon

C. Owl The Owl Nebula is a so-called planetary nebula. This kind of nebula got the name ‘planetary’ because in early telescopes they resembled the appearance of planets, being circular, appearing larger than stars, and being fairly evenly illuminated. Like many planetary nebulae, the Owl is a couple of light years across, and it is caused to glow by a central star. A planetary nebula is typically created when a star no more than 8 times the mass of the sun reaches a later stage of its life when its outer layers are driven away from the core to form an expanding sphere of gas, and the remaining star is condensed into an extremely dense white dwarf star. The Owl Nebula is located in the constellation Ursa Major, the brightest stars of which form the Big Dipper. Most planetary nebulae appear quite small. The Owl, even though it is one of the largest appearing ones, looks only about 1/9 the diameter of the full moon. It got its name because it looks like the head of an owl, not the whole bird.

D.Pelican By Now you may be thinking this game is for the birds, but I promise soon we will branch out to other animals. The Pelican Nebula is yet another vast emission nebula glowing with the characteristic red of excited hydrogen atoms. It is located in the constellation Cygnus the swan, and new stars are forming out of eddies of this hydrogen gas. Because it is about three times closer than the other emission nebulae in this group, it appears larger in the sky, covering an area about 2 times the diameter of the full moon.

E. Jellyfish The Jellyfish Nebula is a supernova remnant located in the constellation of Gemini, the twins. A supernova results from the later stages of evolution of a star many times more massive than the sun. When a massive star runs out of thermonuclear fuel, it implodes, forming a dense stellar core called a neutron star. The outer layers of the star collapse toward the neutron star, then bounce outward in a supernova explosion. If a neutron star is spinning rapidly, it produces a beam of radiation, and it is called a pulsar. The radiation sweeps by like a beacon of light from a lighthouse and can be detected as pulses of radio waves and other types of radiation. This particular supernova, which blew up thousands of years ago, is driven by an embedded pulsar, and lies within a giant molecular cloud with varying densities, so its interaction with the cloud material has caused much distortion from the typical more spherical shape of early supernova ejected material. Currently this nebula is about 70 light years across, and the shock wave is expanding at about 20 to 60 miles per second, depending on the density of the material it is passing through. At its distance of about 5000 light years, it occupies an area of sky about 3 times the area of the full moon.

E. Whale Up until now all the objects discussed are within our Milky Way galaxy, from about 2 to 7 thousand light years distant. But for this object we go 30 million light years out in the direction of the constellation Canes Venatici, the hunting dogs. The Whale Galaxy is a spiral galaxy seen edge-on, which appears in the sky to have a length about ½ the diameter of the full moon It is actually about the size of our own galaxy, and looks a lot like our galaxy would look if seen edge-on from that distance. The center of this galaxy is full of star formation and multi-element-rich gases from many previous supernova explosions. There is a small ‘dwarf’ galaxy next to it, which some see as a pup swimming next to its mother whale in the vast astronomical sea.

Click on any image to get a closer look

The Eagle Nebula

The Swan Nebula

The Owl nebula

The Pelican Nebula

The Jellyfish Nebula

The Whale Galaxy

June 30, 2019

Galaxies, Supernovas 0

Lookout Observatory: Another Supernova Photographed

Dear Lookout Observers,

One interesting compact cluster of 5 galaxies, known as Hickson 68, is about 110 million light years distant, and it is shown in the first image attached. Each galaxy is labeled with its number in the New General Catalog (NGC). Other more distant galaxies can be seen as tiny ovals or smudges, but they are not part of this gravitationally connected cluster This image was taken on June 12, 2018.

On May 1, 2019, a supernova explosion in the galaxy NGC 5353 was first discovered by professional astronomers with a telescope in Hawaii. On May 15 my childhood friend and fellow amateur astrophotographer Fritz Kleinhans told me about this new supernova, but because of cloudy weather and other commitments, I wasn’t free to obtain an image of this supernova until June 7. In the second image attached this new star is indicated by the green arrow. A supernova is what occurs when a star destructively blows up much like trillions of hydrogen bombs going off all at once. This is an evolutionary stage that some stars go through, ending their life as a normal star. In a matter of a few days this single star became one fifteenth as bright as all the billions of stars in the NGC 5353 galaxy put together! It seems to have reached its peak brightness of about 14^th magnitude around May 15, and by the time I got my image it had faded to about 15^th magnitude. It will continue fading over the next year or so until it disappears again.

(“Magnitude” is a measure of the apparent total brightness of a celestial object, and the larger the number, the fainter the object. So, for example, the brightest stars in the night sky are about 1^st magnitude and the faintest stars most people can see in a reasonably dark sky are about 6^th mag. The faintest stars that can be seen in an amateur’s 10-inch diameter telescope are about 14^th mag., but using photography with my 11-inch, I can image stars fainter than 20^th mag. Each unit change in magnitude represents a factor of about 2.5, so a 15^th mag. star is about 2 and ½ times fainter than a 14^th mag. star.)

The third image is a slightly larger field around the Hickson 68 group of galaxies. At the far left is another spiral galaxy, NGC 5371, which appears larger than any in the Hickson 68 group. It is approximately the same distance as the Hickson group, so it may be gravitationally connected to the group of 5, and it actually is larger than any of the galaxies in that group. It is slightly smaller than our own Milky Way Galaxy.

The fourth image, showing the nearby galaxy M101, is exactly at the same scale as the third image. That is, it covers exactly the same amount of sky – about ½ degree high and ¾ degree across, so the full moon could just fit into this picture. M101 looks so huge because it is 5 times closer than the galaxies in the 3^rd image, but it is probably only slightly larger than NGC 5371. Although M101 is roughly the same size as our Milky Way Galaxy, it contains twice as many stars. One of its stars exploded as a supernova back in 2011, but it has faded away by now. I reported on this event in a Lookout Observatory report on July 3, 2012. In this current photo you can see some of the outer reaches of the arms extending to the left (east) and up (north). The small pinkish areas are regions of active star formation with lots of hydrogen gas. At the far left of the picture, about 1/3 of the way down, is a so-called dwarf galaxy, NGC 5477. It is a companion to M101, just as our galaxy has many dwarf galaxies gravitationally connected to us, as described in a Lookout Observatory bulletin on October 18, 2018. This image shows stars and tiny distant galaxies down to about 21^st magnitude.

May you have sunny days in your life and clear skies at night,

Carter, (sometime) resident astronomer,

Lookout Observatory

P.S. My apologies to those who responded to my last Lookout Observatory report and didn’t get a response back from me. I have recently had so many commitments that I couldn’t respond to everyone. I will try to do better.

Click on any image to get a closer look

A cluster of 5 galaxies known as Hickson 68

A supernova explosion in the galaxy NGC 5353

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Hickson 68 group of galaxies & another spiral galaxy, NGC 5371

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Galaxy M101 & dwarf galaxy, NGC 5477

October 18, 2018

Galaxies 0

A Lookout Observatory Bulletin: Our Galactic Neighbors

Dear Friends of Lookout Observatory,

First, a technical note. My trusty astrocamera, after 9 years of happy use, was beginning to get glitchy – sometimes it would stop working in the middle of a picture series, and I would have to restart the software program on the computer that runs the camera, or restart my whole computer, and then start over again. This was very frustrating, so the obvious solution was to buy a bigger, better and more expensive astrocamera. What I didn’t count on was that the old software wouldn’t run the new camera, and the old computer wouldn’t run the new software I had to buy. This meant getting a new computer and spending a lot of time learning how to use the new software in a way that worked well for the new camera. This is pretty complicated stuff for my aging brain, so it has been many months before I could start taking decent pictures again.

To complicate things further, all the forest fires raging in northern California made so much smoke that getting good photos from Lookout Observatory has been impractical this whole summer. So I accepted an invitation from my friend Dr. Fritz Kleinhans to meet him near Silver City, New Mexico, where we had dark skies at about 4800 feet elevation. I apologize for such a long delay in getting any new pictures out, but now here we go with some of the first images from my new camera!

Galaxies, like people, like to hang out in groups. We of course live in the Milky Way Galaxy, and the galaxies nearby (within about 5 million light years) are called the Local Group. The 3 largest galaxies in the group – all spiral galaxies — are the Andromeda Galaxy (also known as M31), the Milky Way, and the Triangulum Galaxy (M33). All the others in the Local Group are considerably smaller; many are spheroidal dwarf galaxies. There may be as many as 100 galaxies altogether. Nearby but very faint galaxies keep being discovered as professional telescopes get ever more powerful. These Local Group galaxies are not randomly distributed. They occur in two clumps, one surrounding our Milky Way, and one surrounding the Andromeda Galaxy. Most of these other galaxies are satellites of – gravitationally bound to – either the Milky Way or the Andromeda Galaxy.

The first picture is of the largest member of our Local Group, the Andromeda Galaxy, about 220,000 light years across and containing about one trillion stars. You can see the tightly wound spiral arms filled with young, hot blue stars surrounding the yellowish core of older stars. In addition you can see two satellite galaxies. M110 is the oval patch above and to the right of center. And M32 looks like the brightest star directly below the center, but it is actually a very compact elliptical galaxy. Because the Andromeda Galaxy is so close to us – only about 2.5 million light years away – it looks large and bright (for a galaxy). It can be seen with the naked eye from a dark location. North is up in this picture, and it covers 2 degrees by 3 degrees of the sky, so five full moons could fit across the length of the galaxy as photographed here. The 3 additional pictures that follow are enlarged to 2x this scale, so they all cover 1.2 degrees by 1.5 degrees. Please zoom in on all images to see more detail.

The Milky Way galaxy is about ¾ the diameter of the Andromeda Galaxy , about 1/2 the mass, and contains about 1/3 the number of stars. Since we live inside it, it is hard to get a picture of it. The third large galaxy in our Local Group, the Triangulum Galaxy, is about 1/4 the diameter of the Andromeda Galaxy, about 1/30 the mass, and contains about 1/20 the number of stars. So while our galaxy is just slightly smaller than the Andromeda, the Triangulum is much smaller. It is closer to the Andromeda Galaxy than it is to us, and it is probably a satellite of that galaxy. It is shown as the second image. The many pink areas in the blue spiral arms indicate lots of hydrogen gas where new star formation is taking place.

My wife Anitra is my reality check that not everyone has a deep interest in astronomical minutia. Her comment on the next two pictures was “they are just little blobs,” so if you react the same way, you are normal. If however, you have a deeper interest in astronomy, read on.

The third picture is of one of the many satellite galaxies of the Milky Way. It is just over ¼ million light years away – very close for a galaxy – but because it is a very different kind of galaxy, vastly smaller than the Andromeda Galaxy, it is also much fainter. In fact, it is so faint that it was not discovered until 1937, and it is difficult to see even in a large amateur telescope from a dark location. It is visible here because its faint light was accumulated over 1 and ½ hours. It is known as the Sculptor Dwarf galaxy, and it is that dim round patch of faint white and bluish stars in the center. It is remarkable that we can see some of the individual stars in this galaxy. All the brighter stars in this photo are foreground stars in our Milky Way, roughly1000 times closer than the Sculptor Dwarf. This galaxy came into existence before our own Milky Way, and its total mass is less than 1/1000 of 1% of the Milky Way’s. As boring as these objects might be, they are numerous. There are probably 10 to 20 times as many dwarf galaxies in the universe as there are large, beautiful galaxies like Andromeda, the Milky Way and the Triangulum Galaxy.

The fourth picture is of another small satellite galaxy of the Milky Way, the Fornax Dwarf galaxy. At least 10 times as massive as the Sculptor Dwarf, it was discovered just a year later, and it is about 1 and 1/2 times as far away and somewhat brighter. The tiny objects labeled F1 through F5 in this picture are globular clusters associated with this galaxy, and their presence makes this galaxy very interesting to astronomers.

Most large galaxies have densely packed spherical clusters of tens or hundreds of thousands of stars – known as globular clusters – surrounding them in a kind of halo. The Milky Way has at least 150 and Andromeda has as many as 500. Most dwarf galaxies have none or only a few. The Fornax Dwarf has the 5 labeled here. The individual stars in them are too dim and tightly packed to be seen in this image, so they just look like very small bright blobs. Interestingly, the one labeled NGC1049(F3) was discovered in the 19^th century, about 100 years before the galaxy itself was noticed (because it is so faint). This globular cluster was number 1049 in the New General Catalogue of Nebulae and Clusters of Stars (abbreviated as NGC), published in 1888. Professional astronomers have used these globular clusters to help determine that this galaxy (and most dwarf galaxies) contain large amounts of dark matter, far greater than the amount of matter in the stars themselves.

The little blur labeled F6 in the Fornax Dwarf image was first thought to be a sixth globular cluster (hence, its similar label), but more recently it has been determined not to be one. Exactly what it is is still not completely clear, but it has been suggested that it might be a very compact group of very distant galaxies shining through the Fornax Dwarf galaxy, which in turn is shining through the foreground stars of our own Milky Way – just another of the many wonders of outer space.

Keep looking up,

Carter, (sometime) Resident Astronomer,

Lookout Observatory

P.S. Technical information was assembled from recent Sky & Telescope Magazine articles, Wikipedia, and online articles by professional astronomers. Details change frequently as new discoveries are made.

The Andromeda Galaxy

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The Triangulum Galaxy

The Sculptor Dwarf Galaxy

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The Fornax Dwarf Galaxy

June 30, 2017

Galaxies 0

Interacting galaxies from Lookout Observatory

Dear Friend,

Spring and early summer is a good time for observing galaxies because at night we are then looking out of the plane of our own galaxy (the Milky Way), with it’s obscuring dust and gas, and deep into interstellar space. Tucked under the handle of the big dipper are many interesting galaxies and clusters of galaxies, including the Whale Galaxy and the Hockey Stick Galaxy. Today Lookout Observatory brings you images of interacting galaxies. (In each picture north is up.)

The first picture is a photo of the sky under the big dipper, whose stars are shown connected by green lines. (Ignore the extra green line at the top left. It belongs to another constellation.) The area outlined by the yellow box (about 1.3 degrees by 2 degrees), which contains our two galaxies of interest, is only about 6 degrees from the North Galactic Pole, a spot in the sky completely perpendicular to the plane of our Milky Way.

The second picture is of the area covered by the yellow box in the first picture, but magnified 45 times. The galaxies are the two streaks of light (each centered in its own pale yellow box). As their names suggest, the Whale is the upper right one, and the Hockey Stick is the lower left one. These galaxies appear close together not just because they are in the same line of sight, but because they are actually close together in space. All the individual stars in this picture are foreground stars in our own galaxy, mostly from a few dozen to a few hundred light years away. But these two galaxies are about 30 million light years away.

The third image is of the area in the box around the Whale (also known as NGC 4631), but at 3 times the magnification. This is a spiral galaxy, about the same size as the Milky Way, that we are seeing edge-on. You can see its yellow-orange core where intense star formation is occurring (a so-called starburst region), its dark obscuring dust clouds, its areas with hot blue clusters of stars, and its knots of red star-forming regions filled with glowing hydrogen gas. A smaller elliptical companion galaxy, NGC 4627, sits just above the Whale. And a few other much more distant galaxies, which appear as just tiny elongated blurs, can be seen in this image.

The fourth image is of the area around the Hockey Stick (also known as NGC 4656). The area where it curves sharply has been given a separate designation, NGC 4657. This may be just a part of the larger galaxy, but some have suggested it might be a separate smaller galaxy that is merging with the larger one. There is also speculation that the very faint smear of blue visible just above and to the left of the Hockey Stick may be a separate irregular galaxy. The Whale, the small galaxy just above it, and the Hockey Stick, and possibly a few other galaxies in the vicinity all interact gravitationally with each other, causing their irregular, distorted appearances. They are known as the NGC 4631 Group. It is possible that the Whale and the Hockey Stick may eventually merge together. X-ray images reveal matter streaming between the two galaxies. Just imagine the powerful gravitational forces that allow things as large as galaxies to pull each other apart!

Keep looking up,

Carter, (sometime) Resident Astronomer,

Lookout Observatory

Sky under the Big Dipper

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Area of sky under the Big Dipper (magnified x45)

The Whale Galaxy (aka NGC4631)

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The Hockey Stick Galaxy (aka NGC 4656)

May 19, 2017

Galaxies, Supernovas 0

Massive Explosion noted by Lookout Observatory

Dear Friends,

An explosion that began just about a week ago continues to pour out energy at approximately ten thousand million million (10 to the 16^th power) times the output of our sun. Luckily for us it is not near enough to vaporize us. In fact, it is a million million times as far from us as the sun is, so it is only a perfectly safe, faint point of light. This is a newly discovered supernova – exploding star – in the Fireworks Galaxy (also known as NGC 6946), about 22 million light years away from our own Milky Way Galaxy.

This exploding star, now known as SN 2017eaw, is what is known as a Type II supernova. That is, it was probably a red giant star at least 10 times as massive as our sun that eventually lost its ability to produce nuclear fusion, leading to sudden collapse under its own massive gravitation, raising it’s core temperature to 10,000 times the sun’s core temperature, resulting in an unimaginably immense explosion where bits of the star are moving at up to 1/3 the speed of light. In destroying itself the star brightens immensely in a matter of seconds, then gradually fades over months and years. This supernova was discovered by Patrick Wiggins, a Utah amateur astronomer who dedicates many hours to searching for these “new stars.”

S197+3moreNGC6946multi224mIPDDRotateStarColBalBrConHSLSelColBal2-PWCrop-b2c

Fireworks Galaxy (pre 2017)

R34NGC6946 IP5mx37ColBalStarSmooBrConHSLSelColBal2PWbGradCrop-lines

Fireworks Galaxy + supernova SN 2017eaw

April 25, 2017

Constellations, Galaxies 0

Two Gems from the Two Bears

Dear Observers,

If you were to go outside tonight at 10 PM, face north, and look between half way and high up in the sky, and if it were clear, and if you live where the sky is really dark at night, you would see something a lot like the first image. The brightest star near the bottom of the image is Polaris, the North Star. In the real sky it is about half way up, and high above it stands the Big Dipper, upside down. In Great Britain this star grouping is know as the Plow, and it is probably the star grouping most recognized by people living in the Northern Hemisphere. In the first image it is at the top, and in case you might have trouble picking it out from all those other white specks, I have outlined it with faint green lines There are also lines coming off from the North Star showing the much fainter stars of the Little Dipper. If you live in or near a city where the skies are not dark, you can still see the North Star and the stars of the Big Dipper, but you might not see any other stars in that direction, because the rest are all pretty faint.

The Big and Little Dippers are not constellations, but only part of a larger grouping of stars that make up the constellations of Ursa Major (the Great Bear) and Ursa Minor (the Little Bear), respectively. The people who saw bears in the larger groupings of stars had really good imaginations, and I won’t even try to show you how they saw bears! But included within the boundary of the constellation of the Great Bear, somewhat toward the Little Bear, are two beautiful galaxies located within the small rectangle at the left side of the image. If you have a dark sky and a good pair of binoculars, you could see two tiny fuzzy patches within that rectangle. Otherwise you can just look at the second image, which is magnified 23 times over the first image. This second image was taken with a 5-inch diameter lens that has a focal length 46 times as long as the the lens used to take the first (wide angle) image. (I already enlarged the first image 2 times and cropped it, so that’s why the second image is only 23 times larger rather than 46 times larger.) These two very different looking galaxies – less than one degree apart – are not just in our line of sight, making them appear close together; they actually are near each other in space, and they interact gravitationally. I have drawn a rectangle around each galaxy showing the outline of the next two individual images, which are at a scale 5 times greater than image 2.

The top one (image 3) is M81 or Bode’s Galaxy. It is the largest of a 30-some group of galaxies known as the M81 Group, They are some of the closest galaxies to our own Milky Way Galaxy outside of our Local Group of 50-some galaxies that lie within 5 million light years of us. M81, at a distance of about 12 million light years, is a beautiful example of a spiral galaxy, just a bit smaller than our own galaxy. The pinkish dots are areas of hydrogen gas where new stars are forming within the bluish spiral arms, which consist mostly of young, hot blue stars. Older stars tend to be situated in the central core region, and in the very center sits a large (invisible) black hole.

The fourth and final image is M82 or the Cigar Galaxy. At less than half the size of M81, it is physically located at a distance from M81 only about 3 times the diameter of M81. This puts it close enough to be greatly affected by M81’s tidal gravitational forces. This has caused M82 to become a so-called starburst galaxy, one where massive amounts of energy leads to new star formation. In the center portion of this galaxy with massive amounts of red-glowing hydrogen gas, star formation is occurring 10 times faster than in our entire Milky Way galaxy. M82 used to be classified as an irregular galaxy, but recent professional images in the near infrared have found a nearly edge-on spiral structure, obscured in the visual wavelengths by large amounts of dust. This image of M82 was taken not under the dark skies of Lookout, but under the light-polluted skies of Albany. Because of this it required a special filter and an accumulation of more than 8 hours of exposure. A supernova that occurred 3 years ago in M82 was described in a February 27, 2014, Lookout Observatory email.

Keep looking up,

Carter Mehl,

(Sometime) Resident Astronomer,

Lookout Observatory

Click on any image to get a closer look

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Night sky with Big Dipper & Little Dipper

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Bode’s Galaxy & the Cigar Galaxy

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Bode’s Galaxy

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Cigar Galaxy

July 12, 2016

Galaxies, Stars 0

From Lookout Observatory: Scorpius Zoom

Dear Friends,

This time of year if you look to the south just after it gets dark, and you have a clear horizon, and you are not in a big city with too much light, you can see the constellation Scorpius, the scorpion. From mid-Northern latitudes it is just above the horizon for a couple of hours before it sets. It is one of my favorite constellations because it actually looks rather like its namesake and because some of the richest parts of the Milky Way lie in Scorpius.

I have attached four photos for you to enjoy, all in Scorpius. In each photo north is to the top. First is a wide angle view of the whole constellation, and I have added green lines between the prominent stars that make the shape like a scorpion. (Ignore the yellow rectangle for now.) At the top right are three stars that represent the head. The body then curves down and to the left until it curls upward to end in two stars side-by-side that represent the stinger. Notice that this image, especially in the left half, is filled with star clouds and dark lanes of the Milky Way. These are readily visible to the naked eye if you have a really dark sky. The brightest star in Scorpius is Antares, located inside the yellow rectangle.

The second image is of the area inside the yellow rectangle. I have left off the green lines showing the scorpion shape, but I have labeled Antares so you can tell it from other bright blobs in the region. Antares is a red supergiant star. It is so large that if it replaced the sun, it would extend all the way out past the orbit of Mars, completely engulfing the earth. This image was exposed for about an hour, six times as long as the previous one, so it goes much deeper, making the faint nebulosity in the region look very bright. Although most red nebulae consist of hydrogen gas energized by nearby stars to emit red light, the yellowish-reddish nebulosity just above Antares is probably a dust cloud of solid particles that are simply reflecting the red light of brilliant Antares, which is embedded in it. The bluish nebulosity is light from blue-white stars reflected off of nearby interstellar gas and dust. The narrow green rectangle in this photo shows the area captured in the third image.

The tall thin image is actually two one-hour images, one just north of the other, stitched together to make a single image. By enlarging this image and looking at one section at a time, you can see more detail in the gas clouds and in the dark clouds of dust that obscure the stars behind them. Near the top is the bright star (actually 3 stars close together) Rho Ophiuchi. It is surrounded by the large blue reflection nebula IC 4604. This is a region of much new star formation, intensely studied by professional astronomers. Moving south from there we come to two stars close together surrounded by a bright whitish nebula with dark lanes swirling through it. This nebula is known as IC 4603. A little below it near the right edge of the frame is a rainbow looking arc of red and green light. This is an optical artifact resulting from scattered light from a bright star just outside of the picture. Continuing further down we come to a large yellowish-reddish patch. This is a small part of the large dust cloud, IC 4606, that extends all the way over to and around Antares, which is out of the picture, down and to the left. In the lower, more yellow part of this cloud is a small globular star cluster known as NGC 6144. And finally at the bottom edge and to the right is the large globular cluster known as M 4. These two objects are not part of the mass of nebulosity in this region of our galaxy. Rather they are two of the roughly 150 globular clusters — spherical, tightly packed clusters of tens to hundreds of thousands of very old stars — that surround our galaxy.

And finally the fourth image is a more magnified image of just the globular cluster M 4. This is one of the closest globular clusters to us, being about 7000 light years away. (The smaller appearing NGC 6144 is about 4 times farther away, and the colored nebulae in the earlier images are only 400 to 600 light years away.) A single planet has been detected around one of the stars in M 4. This is very unusual because planetary orbits are unstable in the star-crowded environments of globular clusters. M 4 is a beautiful sight in a moderate-sized telescope, where one can note its distinctive north-south line of stars that run through its very center. … That’s as up close as I can get you with the photographic equipment I have, but the constellation of Scorpius is filled with many more wonders.

Keep looking up,

Carter, (sometime) Resident (amateur) Astronomer,

Lookout Observatory

Constellation Scorpius

Western Scorpius

More detail in the gas clouds – Rho Ophiuchi & more

globular cluster M4

January 11, 2016

Galaxies 0

Cosmic Distances from Lookout Observatory Photos

Dear Friends,

This time of year it is too cold to stay out all night photographing the skies, but it is a good time to reflect on the immensity of the universe. The first photo is of a fairly large region of the sky (about 35 degrees on each side) that includes stars in the constellations of Pegasus and Andromeda. The square marked with blue lines identifies the four stars known as The Great Square of Pegasus. The upper left star actually belongs to the constellation Andromeda, and the blue lines that angle up and to the left to make a narrow curved “V” connect many of the other brightest stars that make up the constellation Andromeda. The star with the red arrow pointing to it is Mirach, the second brightest star in Andromeda. To the upper right of Mirach is a corresponding star in the other leg of the “V,” and an equal distance beyond that is a bright oval patch, which is the Andromeda Galaxy known as M31.

M31 is the closest large, bright galaxy to our own Milky Way Galaxy. Galaxies tend to group in clusters, and there are approximately 50 galaxies that make up our so-called Local Group. Most of these are small, faint galaxies – so-called dwarf galaxies – and many are closer to us than M31. M33 is the name of the other relatively large, bright galaxy that is part of our local group of galaxies. It can be seen in this photo as a small fuzzy patch about the same distance from Mirach as M31, but in the opposite direction. If you enlarge the photo a lot, you can see that the outline of M33 is irregular, unlike the image of Mirach, a star, which is perfectly round. M31 and M33 are the farthest objects you can see with the naked eye. They are faintly visible in a dark sky, at the very limits of visibility. You normally can’t see them from within a city. You need dark suburban or country skies. This time of year just after it gets dark M31 is almost directly overhead in the sky.

All of the stars in this photo, whether bright like Mirach or faint like the thousands of tiny dots sprinkled in the background, are all within our Milky Way Galaxy. The star closest to our Sun is Alpha Centauri (not visible in this photo). It is about 4.3 light-years away. A light-year is the distance light travels in one year – about 5,900,000,000,000 miles. One of the brightest stars in the current photo is Mirach, and it is about 200 light years away. Just a short distance from Mirach in this photo is M31, but it only looks that way because they lie in the same general direction. Actually M31 is 10,000 times more distant than Mirach – about 2 million light years away.

The second photo was taken with a 420mm telephoto lens, and it is a close up view of M31, in the same orientation as the first photo with north up. Here M31 runs diagonally across the whole photo. If you enlarge it greatly, you can see a lot of detail in M31’s spiral arms and dust lanes, but every star in this photo is in our own Milky Way Galaxy, not part of M31. But notice the oval blob to the upper right from M31. This is M110, a satellite galaxy of M31. It is another one of our Local Group, and it is approximately the same distance from us as M31. Now look above M110 where the red arrow is pointing. If you enlarge the photo greatly, you can see that it is pointing to a very small, round blob near the limit of what can be seen in this photo. That blob is a very distant galaxy 1000 times farther away than M31! It doesn’t have a name other than the position that locates it on the celestial sphere. At its distance of about 2 thousand million light years it is one seventh of the way to the very end of the visible universe!

Another way to try to grasp these immense distances is to put them in a smaller scale. If we make the diameter of the Earth’s orbit around the sun 1/100^th of an inch (about the size of a period on the page of a book), then the closest star would be about 26 feet away. The star Mirach in Andromeda would be a mile away, and M31 would be 10,000 miles away. The distant galaxy, that tiny smudge in the second photograph, would be one ninth of the way to the sun, and the edge of the visible universe would be almost to the sun. Of course, at this scale it would take about 650 of us laid head-to-toe to stretch across the smallest atom (a hydrogen atom)! Makes you feel kind of small, doesn’t it?

Happy New Year,

Carter Mehl,
(sometime) Resident Astronomer,

Lookout Observatory

Click on any image to get a closer look

Andromeda & Pegasus marked

Andromeda Galaxy M31