08/25/2022 – Ephemeris – Looking to the heart of the Milky Way

This is Bob Moler with Ephemeris for Thursday, August 25th. Today the Sun will be up for 13 hours and 34 minutes, setting at 8:31, and it will rise tomorrow at 6:58. The Moon, 2 days before new, will rise at 5:52 tomorrow morning.

Behind a dark cloud in the Milky Way, just above the spout of the teapot asterism or informal constellation that we see of the zodiacal constellation of Sagittarius, lies the very center of our Milky Way Galaxy. It cannot be seen in visible light, but can be detected with radio waves and infrared light that can penetrate the clouds of dust between. In 1932 Bell Laboratory physicist and radio engineer, Karl Jansky, discovered a source of radio static that came from that region of sky. It was subsequently given the designation Sagittarius A. It turns out that within that source there is an object called Sagittarius A* (Pronounced Sagittarius A Star), invisible in the near infrared, but with the mass of four million suns. It was recently imaged as the black hole at the center of our galaxy.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Our place in the Milky Way. Note that we appear to be in a barred spiral galaxy. The arms are numbered and named. 3kpc is the 3 kiloparsec arm. 3kpc = 9,780 light years. The Sun is about 27,000 light years from the center. Credit NASA and Wikimedia Commons, via EarthSky.org

Location of the center of the Milky Way and the Teapot of Sagittarius. It’s behind that dark cloud.

An image from the Chandra X-ray Telescope of the center of the Milky Way. SGR A or Sagittarius A is a radio source. SGR A*, pronounced Sagittarius A Star, is the 4 million solar mass black hole in the center of the Milky Way Galaxy. Credit NASA.

M87* size compared to Sagittarius A*. The size of a black hole is directly related to its mass. The asterisk * is pronounced “Star”. Credit: Event Horizon Telescope Collaboration.

The black hole images were reconstructed from data from 8 sub millimeter radio telescopes and arrays of the Event Horizon Telescope Collaboration. The telescopes were located from Greenland to the South Pole and From Hawai’i to Europe. The data from the telescopes, observing the black holes simultaneously, were combined to act like a single telescope with the diameter of the Earth in order to resolve the black holes.

08/18/2022 – Ephemeris – The Great Rift

This is Ephemeris for Thursday, August 18th. Today the Sun will be up for 13 hours and 54 minutes, setting at 8:43, and it will rise tomorrow at 6:49. The Moon, 1 day before last quarter, will rise at 12:02 tomorrow morning.

High overhead, the Milky Way is seen passing through the Summer Triangle of three bright stars. Here we find the Milky Way splits into two sections. The split starts in the constellation of Cygnus the Swan or Northern Cross very high in the east. The western part of the Milky Way ends southwest of Aquila the eagle. This dark dividing feature is called the Great Rift. Despite the lack of stars seen there, it doesn’t mean that there are fewer stars there than in the brighter patches of the Milky Way. The rift is a great dark cloud that obscures the light of the stars behind it. Sometimes binoculars can be used to find the edges of the clouds of the rift, as star numbers drop off suddenly. This is especially easily seen in Aquila.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

The Great Rift finder animation as seen in the Summer Triangle, also showing the constellations of Cygnus the swan and the northern part of Aquila the Eagle. This image a stack of 5 30 second exposures taken the morning of the Perseid meteor shower the is year in a vain attempt to capture some meteors.

08/16/2022 – Ephemeris – Scanning Sagittarius with binoculars

This is Bob Moler with Ephemeris for Tuesday, August 16th. Today the Sun will be up for 14 hours to the minute, setting at 8:46, and it will rise tomorrow at 6:47. The Moon, 3 days before last quarter, will rise at 11:15 this evening.

The Moon has left the evening sky, so let’s take another look at the constellation of Sagittarius. Its bright stars make a follow the dots image of a stout little teapot. In, around and above the teapot is a wealth of nebulae, which are clouds of gas and dust and clusters of stars. Stars are born in bunches from a cloud of gas. When enough stars are born, their stellar winds blow away the nebulosity leaving a star cluster. Use a pair of binoculars or a very low power telescope and just wander around and above the teapot, including and especially the spout on the right side. In binoculars, star clusters appear fuzzy like nebulae, however a small telescope with magnification of 20 times should resolve most of them.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Sagittarius in a short time exposure with added annotations. The “M” designations are objects in Charles Messier’s catalog created in the latter half of the 18th century. LSSC is the Large Sagittarius Star Cloud, SSSC is the Small Sagittarius Star Cloud. Labels are to the right of the objects they name. Credit Bob Moler.

This is the short radio program version of the August 8, 2022, Ephemeris Extra post Wandering through Sagittarius

Ephemeris Extra – Wandering through Sagittarius

Sagittarius in a short time exposure with added annotations. The “M” designations are objects in Charles Messier’s catalog created in the latter half of the 18th century. LSSC is the Large Sagittarius Star Cloud, SSSC is the Small Sagittarius Star Cloud. Credit Bob Moler.

Sagittarius is seen low in the south in August. It’s between Scorpius to the west, and Capricornus, rising in the southeast. The name Sagittarius simply means archer. It doesn’t describe the fact that the archer isn’t just any old bloke with a bow and arrow, but is, indeed, a centaur, one of the two in the list of constellations. The other, Centaurus, is too far south to be seen from Michigan. And whose brightest star, Alpha Centauri, is in the closest star system to our solar system.
Centaurs, as a rule, were a rowdy bunch, the ancient Greek equivalent to a modern motorcycle gang. However, the centaur depicted by Sagittarius can be thought to be Chiron, though it can also be ascribed to Centaurus. Chiron was learned, a teacher and physician. I’ve noticed that in some artist’s depictions of Chiron, he is teaching Achilles how to use the bow and arrow. He also taught medicine to Asclepius, the great physician, who is seen in the heavens as the constellation Ophiuchus, above and right of Sagittarius.
What most of us see in the stars here is maybe a bow drawn to shoot at the heart of Scorpius, or a stout little teapot as in the children’s song. It even has the Milky Way seeming to rise from the spout like steam. The teapot rises in the southeast as if standing upright, and as the night wears on, it rises and move westward, slowly tilting to pour out its tea on the southwestern horizon.
The area of Sagittarius and the Milky Way is a fantastic part of the sky to explore with binoculars or a low power telescope on moonless nights. At the head of this post is a photograph of Sagittarius and the Milky Way taken from my home, with lines and labels. It’s somewhat spoiled by the sky glow from Chum’s Corner, a small commercial center 3.6 miles away, from the lower left. Most binoculars will show open or galactic star clusters as fuzzy spots like nebulae, which are fuzzy because they are clouds. The older globular star clusters require larger amateur telescopes to resolve.
I’ve only pointed out one in the image, that’s M22, whose designation, we have fun with at star parties at the Sleeping Bear Dunes National Lakeshore, since the road M22 runs through the park. Which came first? That’s easy, Charles Messier cataloged his 22nd object before Michigan was a state or even had roads. Well, maybe there were a few, around Detroit and Sault Ste. Marie, back when the major “roads” were the Great Lakes, and the rest Indian trails.
A telescope, even a small one, will resolve open clusters, showing individual stars. Telescopes will show the shapes of nebulae if they are bright enough.
One nebula with a distinctive shape is M17. The descriptive name I first knew it as was the Omega Nebula, and also the Horseshoe Nebula. To me, it never looked like either. It looked like a check mark, or a somewhat short necked swan. And it also goes by those names too. The planetarium program I use a lot, Stellarium, also calls it the Lobster nebula. I’m not much for seafood, but it doesn’t look like a lobster, or maybe I’m not hungry enough.
M16, is the Eagle Nebula. It has an associated star cluster. My eyes are drawn to the star cluster. The nebulosity is very faint, and I usually can’t see it. Part of the nebula was famously photographed by the Hubble Space Telescope and called the Pillars of Creation. In actuality, they are the Pillars of Destruction as they are being blown away by the stellar winds of the star cluster.
M8 is the Lagoon Nebula, it also has an associated star cluster. In telescopes, it is crossed by a narrow dust cloud suggestive of a lagoon. Nearby M20 is the Trifid nebula, which has a low surface brightness and can easily be missed. It is crossed by three narrow dust clouds dividing it into three, or on closer inspection, four wedges.
These just scratch the surface. So with or without optical aid wander through the celestial wonders and star clouds of Sagittarius. You have August and September to do it in the evening before they set for another year.

Based on an article I wrote for the August 2022 issue of the Stellar Sentinel, the Newsletter of the Grand Traverse Astronomical Society.

10/05/2021 – Ephemeris – Can you spot the North American Nebula?

This is Bob Moler with Ephemeris for Tuesday, October 5th. Today the Sun will be up for 11 hours and 29 minutes, setting at 7:15, and it will rise tomorrow at 7:47. The Moon, 1 day before new, will rise at 7:46 tomorrow morning.

Most of what we see in the Milky Way are just masses of stars, but there are bright clouds of gas, or to name them properly: emission nebulae. These bright clouds are areas of star formation. It is the ultraviolet light from young massive stars that light up the clouds they were formed from. A bright one, easily visible in binoculars, is just about overhead at 9 p.m. Called the North American Nebula, a glow, that in photographs is shaped much like our continent, is just east of the star Deneb which is practically overhead in the evening. Deneb is the northernmost star of the Summer Triangle, and brightest star in Cygnus the swan or Northern Cross. There are many other nebulae in the Milky Way, visible in binoculars and small telescopes. Many enjoyable hours can be spent sweeping the Milky Way for nebulae and star clusters.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT-4 hours). They may be different for your location.

Addendum

North American Nebula finder animation. I’ve dimmed down the stars a bit and increased the brightness of the Milky Way to aid in spotting the nebula. It requires dark skies to see it. I believe I can make it out with the naked eye too. Click on the image to enlarge it. Created using Stellarium and GIMP.

One of my old photographs of Deneb and the North American Nebula, digitized from a slide.

Better view of the North American Nebula taken by Scott Anttila.

08/13/2021 – Ephemeris – Rescheduled virtual star party tonight

This is Bob Moler with Ephemeris for Friday, August 13th. Today the Sun will be up for 14 hours and 8 minutes, setting at 8:51, and it will rise tomorrow at 6:44. The Moon, 2 days before first quarter, will set at 11:36 this evening.

The Grand Traverse Astronomical Society will try again to hold a virtual star party starting at 9:30 pm tonight via the Zoom app on the Internet. We were clouded out last Friday night. Jerry Dobek, professor of astronomy at Northwestern Michigan College, will host the event with the 16-inch telescope at the College’s Observatory and an imager, but only if it’s clear in Traverse City. It should feature a look at Venus and the crescent Moon to start. Saturn and Jupiter will be up by then, but they’re quite low in the sky. We might take another look at them later on when their images are steadier. The wonders of the Milky Way are all available. Instructions and a link can be found on the society’s website, www.gtastro.org.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

The southern Milky Way from Aquila to Sagittarius taken from my backyard with light pollution from businesses on US 31 in Chums Corners and Grawn south of me.  I live about 7 miles west of the NMC Observatory. These bright lights are to its southwest and farther away. Click on the image to enlarge it.

08/05/2021 – Ephemeris – Looking toward the center of the Milky Way in Sagittarius

This is Ephemeris for Thursday, August 5th. Today the Sun will be up for 14 hours and 29 minutes, setting at 9:02, and it will rise tomorrow at 6:35. The Moon, 3 days before new, will rise at 4:09 tomorrow morning.

Let’s look around the Teapot shape of stars that is the constellation of Sagittarius. A pair of binoculars or a telescope with a very low magnifying power is all that’s needed. The purpose here is not so much to make things bigger, but make them brighter. Right off the tip of the teapot’s spout is a large and bright patch of light. This is the farthest we can see, in visible light that is, toward the center of our galaxy, part of the central bulge. Astronomer Walter Baade discovered that fact in the mid 1940s. The center of the galaxy is 4 moon-widths or 2 degrees to the right of it, but obscured by a cloud of interstellar dust. It is called the Large Sagittarius Star Cloud or Baade’s Window. The glow there comes from 25 thousand light years away.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

Baade’s Window, aka Large Sagittarius Star Cloud. A finder animation created from my photograph taken August 23, 2016, at 11:23 pm. Click on the image to enlarge it.

06/28/2021 – Ephemeris – The summer Milky Way

This is Ephemeris for Monday, June 28th. Today the Sun will be up for 15 hours and 32 minutes, setting at 9:32, and it will rise tomorrow at 6:00. The Moon, 3 days before last quarter, will rise at 12:50 tomorrow morning.

Last night we had the latest sunset of the year. That’s great news for star gazers who like dark skies and the Sun is not among the stars they want to gaze at. But it won’t get noticeably darker earlier in the evening until late July. But when that does happen, the glory of the summer Milky Way becomes visible. On top of that, the peak night of the Perseid meteor shower, the night of August 11th and morning of the 12th. The three-day-old Moon that night won’t bother the meteor shower at all. The winter sky has the Milky Way also, but we are then looking out, away from the center of our galaxy. It’s hard to tell there’s a milky band there at all. In summer, we are looking toward the more populated parts of our galaxy. It’s a wonder to behold.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT-4). They may be different for your location.

Addendum

The Milky Way from Cygnus to Scutum. This image, actually a stack of 5 images, was taken on August 12, 2018. I was hoping to record Perseid meteors. It was a poor showing, as none appeared in these images. We were hampered that year by smoke from the western US wildfires, which really affected the lower part of this image, which was still pretty high up in the sky, by giving it a red tinge. Featured here is the Great Rift, a series of dust clouds that split the Milky Way into two sections, subject of previous and future programs. Click on the image to enlarge. Credit: Bob Moler (me).

08/20/2020 – Ephemeris – Where are we in the Milky Way Galaxy?

This is Bob Moler with Ephemeris for Thursday, August 20th. Today the Sun will be up for 13 hours and 47 minutes, setting at 8:39, and it will rise tomorrow at 6:52. The Moon, 2 days past new, will set at 9:59 this evening.

If we are in the Milky Way galaxy, where are we, and where’s the center of this vast spiral? Astronomers have found that the Sun is located in an offshoot of a spiral arm called the Orion Spur and the naked eye stars in the sky are also in it. In the winter constellation of Orion we are looking away from the center of the galaxy. This time of year, looking to the south in the evening at the Teapot of stars that is Sagittarius we look toward the center, which we can’t see due to the gas and dust in the way. It’s there, just above the spout of the Teapot. It can be seen, but not in visible light. It was the first thing detected with a radio telescope and it can be seen in the infrared. But there, 27,000 light years away is a 4 million solar mass black hole at the center.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Sun in the Orion Spur and the nearby spiral arms of the Milky Way Galaxy. The direction to the center of the galaxy is down. Click on the image to enlarge. Public Domain, Wikimedia.

Our place in the Milky Way. Note that we appear to be in a barred spiral galaxy. The arms are numbered and named. 3kpc is the 3 kiloparsec arm. 3kpc = 9,780 light years. The Sun is about 27,000 light years from the center. Credit NASA and Wikimedia Commons, via EarthSky.org.

Location of the center of the Milky Way and the Teapot of Sagittarius. It is blocked by gas and dust in visible light.

An image from the Chandra X-ray Telescope of the center of the Milky Way. SGR A or Sagittarius A is a radio source. SGR A*, pronounced Sagittarius A Star, is the 4 million solar mass black hole in the center of the Milky Way Galaxy. Credit NASA.

08/18/2020 – Ephemeris – What is the Milky Way really like?

This is Ephemeris for Tuesday, August 18th. Today the Sun will be up for 13 hours and 53 minutes, setting at 8:42, and it will rise tomorrow at 6:50. The Moon is new today, and won’t be visible.

Last Friday and yesterday we looked at what the Milky Way looked like, but what is the Milky Way really like. It’s hard to tell, being inside it. In the 1920s astronomers gradually learned that the Milky Way was similar to the great number of spiral nebulae seen outside of the milky band. It was a flattened pinwheel of stars, gas and dust. At first they and the Milky Way were called island universes because until then it was thought that the Milky Way was the entire universe. The word for the Milky Way and those other structures is galaxy. The word galaxy is related to the Greek word for milk. Astronomers in the latter half of the 20th century using radio telescopes were able to trace out the clouds of gas that give our galaxy its spiral structure.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The shape of the universe (Milky Way) as measured by William Herschel by counting stars in the eyepiece fields of his telescope pointed in various directions. The large indent on the right is caused by the Great Rift, clouds of gas and dust that block the light of the stars behind it, not the lack of stars in that direction that he thought. The Great Rift is easily seen in the summer sky running through the Milky Way.

1950’s radio map of the Milky Way Galaxy. The original source is for the map is The galactic system as a spiral nebula Oort, J. H.; Kerr, F. J.; Westerhout, G. MNRAS 118, (1958) p. 379.

Our place in the Milky Way. Note that we appear to be in a barred spiral galaxy. The arms are numbered and named. 3kpc is the 3 kiloparsec arm. 3kpc = 9,780 light years. The Sun is about 27,000 light years from the center. Credit NASA and Wikimedia Commons, via EarthSky.org.

One of the many spiral nebulae visible, namely the Pinwheel Galaxy, M101 near the handle of the Big Dipper. Credit Scott Anttila.