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Kiss the Sky Tonight -- Month of September 2019

Posted by Guy Pirro   09/03/2019 02:33AM

Kiss the Sky Tonight -- Month of September 2019

M2 (NGC 7089), the first globular cluster to be added to the Messier catalog, is located roughly 37,000 light-years from Earth in the constellation Aquarius. A globular cluster is a spherical group of stars that are bound together by their mutual gravitational attraction. M2 has a diameter of over 150 light-years and is one of the largest clusters of its kind. It was discovered in 1746 by the French astronomer Jean-Dominique Maraldi while he was observing a comet. This Hubble image of M2’s core was created using observations taken at visible and infrared wavelengths. M2 contains over 150,000 stars. Most of the cluster’s mass is concentrated at its center, with shimmering streams of stars extending outward into space. It has an apparent magnitude of 6.3 and can be seen with the naked eye in ideal viewing conditions. The best time to observe M2 is during the months of September and October. Large telescopes will resolve the cluster’s individual stars. (Credits: NASA, JPL – Caltech, and the Office of Public Outreach – STScI) (Image Credit: NASA, ESA, STScI and A. Sarajedini - University of Florida)



Kiss the Sky Tonight -- Month of September 2019

Welcome to the night sky report for September 2019 -- Your guide to the constellations, deep sky objects, planets, and celestial events that are observable during the month. In September, Pegasus becomes increasingly prominent in the southeastern sky, allowing stargazers to locate globular star clusters and a double star, Alpha Capricorni. Look for lovely crescent Moons at the start and end of the month. The September equinox brings the beginning of fall in the Northern Hemisphere. And Mars is at solar conjunction, meaning it has disappeared from night skies. The night sky is truly a celestial showcase. Get outside and explore its wonders from your own backyard.


As September brings transition from summer to fall, the sky transitions to the stars of autumn. Increasingly prominent in the southeastern sky is Pegasus, the winged horse. The Great Square of stars that outlines the body is a useful guide to the fall patterns around it.


Near the Great Square lies the sprawling pattern of Aquarius, the water-bearer. Located within the western part of the constellation is M2, one of the oldest and largest globular star clusters associated with the Milky Way galaxy. It appears as a circular, grainy glow in backyard telescopes.


NASA’s Hubble Space Telescope has imaged the cluster, a compact globe of some 150,000 stars that are more than 37,000 light-years away. At approximately 13 billion years old, this cluster formed early in the history of the universe, and offers scientists an opportunity to see how stars of different masses live and die. Results from ESA’s Gaia satellite suggest that this cluster, along with several others, may have once belonged to a dwarf galaxy that merged with the Milky Way.


West of Aquarius is the constellation of Capricornus, the sea goat, a figure dating back to the Sumerians and Babylonians. The star at the western end of Capricornus is Alpha Capricorni. Alpha Capricorni is an optical double but not a binary pair.


The brighter star, Algedi, is about 100 light-years away. The fainter star lies along the same line of sight but is roughly eight times farther away. The pattern hosts another globular star cluster, M30. It appears as a hazy glow in small telescopes.


Stars are packed so closely in globular clusters that they can interact with each other. Binary stars can exchange partners in their tight gravitational square dance. More massive objects like black holes and neutron stars move toward the center. M30 likely started life with another galaxy that merged with our own, since the globular cluster is orbiting the Milky Way in the opposite direction of most stars.


Look west to find the constellation Sagittarius, the centaur archer in the sky. Past the centaur’s arm, you will find another globular star cluster, Terzan 5. Terzan 5 sits near the dark dust lanes of the Milky Way. Bright blue young stars are visible in the foreground of the ancient cluster. The core of Terzan 5 shines brightly with the X-ray light from white dwarfs and neutron stars.








Take advantage of mild, late summer nights to enjoy the constellations and ancient globular star clusters of the September sky, as well as the Moon and planets.

We're in a several-month period right now when the new moon falls right around the end of each month. This means we get to enjoy lovely waning crescent moons at dusk for the first few days of each month, and delightful waxing crescents in the predawn sky near the end of each month.

This month, look low in the west about half an hour after sunset to enjoy the crescent moon on September 1st through the 4th, with the Moon appearing a bit higher in the sky each night. By the 5th, the first-quarter (that is, half-full) Moon winds up here, just a couple of degrees to the right of Jupiter.

At the end of the month, from September 23rd to the 27th, look east half an hour before dawn for an increasingly slimmer crescent that appears lower in the sky each day.

As you make your lunar observations, remember that for many thousands of years, the cycles of the Moon and Sun were the basis of human timekeeping. And many traditional cultures still rely on these cycles to mark special events.

A few months ago, it seemed like the Red Planet, Mars, was a constant companion in the evening sky. But as our two planets moved along in their orbits this summer, Mars has drifted further into the glare of the Sun, finally disappearing from our skies altogether in July.

From Earth's point of view, in late August and early September, Mars is more or less behind the Sun. The Sun expels hot, ionized gas from its corona, which extends far into space. This has implications for spacecraft at Mars, like NASA's Insight lander and Curiosity rover. During solar conjunction, this gas can interfere with radio signals when engineers try to communicate with spacecraft orbiting or on the planet surface, corrupting commands and resulting in unexpected behavior from our deep space explorers. To be safe, engineers hold off sending commands when Mars disappears far enough behind the Sun's corona that there's increased risk of radio interference. This event, called solar conjunction, happens about every two years. For those of us eager for a peek at Mars with our own eyes once again, it'll return to our pre-dawn skies in early November.






September 23rd marks the equinox, with day and night being of equal length. This marks the beginning of Fall in the Northern Hemisphere and Spring in the Southern Hemisphere. Although this means it's time to bid farewell to those long summer days, the upshot for stargazers is longer nights, meaning more time to look up!

From the start of the equinox until the winter solstice in December, nights become longer than days. This reduction in the number of hours of sunlight per day is what leads to seasonal cooling we associate with Fall and Winter. Of course, it's the opposite story in the Southern Hemisphere, where the September equinox ushers in the beginning of Spring.

The night sky is always a celestial showcase. Explore its wonders from your own backyard.

The following Deep Sky Objects are found in constellations that peak during the month. Some can be viewed with a small telescope, but the majority will require a moderate to large telescope. The following is adapted from my personal viewing list: "The Guy Pirro 777 Best and Brightest Deep Sky Objects."


Constellation: Aquarius

NGC 6981                    Globular Cluster           M72

NGC 6994                    Open Cluster               M73

NGC 7009                    Planetary Nebula          C55, Herschel 400 H1-4 Saturn Nebula

NGC 7089                    Globular Cluster           M2

NGC 7293                    Planetary Nebula        C63 Helix Nebula

NGC 7606                    Galaxy                         Herschel 400 H104-1

NGC 7723                    Galaxy                         Herschel 400 H110-1

NGC 7727                    Galaxy                         Herschel 400 H111-1

     - NGC 7724             Galaxy                              - Paired with H111-1



Constellation: Capricornus

NGC 7099                    Globular Cluster             M30                  



Constellation: Cepheus

Caldwell 9                   Diffuse Nebula               C9 Cave Nebula

IC 1396                        Open Cluster              P6 Elephant Trunk Cluster

NGC 40                        Planetary Nebula          C2 Herschel 400 H58-4 Bow Tie Nebula

NGC 188                      Open Cluster               C1

NGC 2300                    Galaxy                        P220

     - NGC 2276             Galaxy                              - Paired with P220

NGC 6939                    Open Cluster               Herschel 400 H42-6

NGC 6946                    Galaxy                        C12, Herschel 400 H76-4

NGC 7023                    Open Cluster                C4 Iris Nebular Cluster

NGC 7142                    Open Cluster                 Herschel 400 H66-7

NGC 7160                    Open Cluster                 Herschel 400 H67-8

NGC 7226                    Open Cluster                 P140

NGC 7235                    Open Cluster                 P7

NGC 7261                    Open Cluster                 P8

NGC 7380                    Open Cluster                 Herschel 400 H77-8

NGC 7510                    Open Cluster                 Herschel 400 H44-7

NGC 7762                    Open Cluster                 P141



Constellation: Lacerta

IC 1434                        Open Cluster              P159

IC 1442                        Open Cluster              P160

IC 5217                        Planetary Nebula          P230

NGC 7209                    Open Cluster                Herschel 400 H53-7

NGC 7243                    Open Cluster                 C16, Herschel 400 H75-8

NGC 7245                    Open Cluster                 P161

NGC 7296                    Open Cluster                 Herschel 400 H41-7



Constellation: Pegasus

NGC 7078                    Globular Cluster            M15

NGC 7217                    Galaxy                         Herschel 400 H207-2

NGC 7331                    Galaxy                         C30, Herschel 400 H53-1

NGC 7448                    Galaxy                         Herschel 400 H251-2

NGC 7457                    Galaxy                         P173

NGC 7479                    Galaxy                         C44, Herschel 400 H55-1

NGC 7814                    Galaxy                         C43



Constellation: Sagittarius

IC 4684                        Diffuse Nebula           P182

IC 4725                        Open Cluster               M25

IC 4776                        Planetary Nebula           P183

NGC 6440                    Globular Cluster            Herschel 400 H150-1

NGC 6445                    Planetary Nebula          Herschel 400 H586-2 Little Gem Nebula

NGC 6469                    Open Cluster               P184

NGC 6494                    Open Cluster                M23

NGC 6507                    Open Cluster                 P185

NGC 6514                    Diffuse Nebula               M20, Herschel 400 H41-1 Trifid Nebula

NGC 6520                    Open Cluster                 Herschel 400 H7-7

NGC 6522                    Globular Cluster             Herschel 400 H49-1

NGC 6523                    Diffuse Nebula                M8 Lagoon Nebula

NGC 6528                    Globular Cluster              Herschel 400 H200-2

NGC 6530                    Open Cluster                  P49

NGC 6531                    Open Cluster                   M21

NGC 6540                    Globular Cluster               Herschel 400 H198-2

NGC 6544                    Globular Cluster                Herschel 400 H197-2

NGC 6546                    Open Cluster                     P106

NGC 6553                    Globular Cluster                 Herschel 400 H12-4

NGC 6558                    Globular Cluster                  P107

NGC 6561                    Open Cluster                      P186

NGC 6563                    Planetary Nebula                 P187

NGC 6565                    Planetary Nebula                 P248

NGC 6567                    Planetary Nebula                 P188

NGC 6568                    Open Cluster                         Herschel 400 H30-7

NGC 6569                    Globular Cluster                     Herschel 400 H201-2

NGC 6583                    Open Cluster                          Herschel 400 H31-7

NGC 6590                    Open Cluster                          P50

NGC 6603                    Open Cluster                          M24 Small Sagittarius Star Cloud

NGC 6613                    Open Cluster                          M18

NGC 6618                    Open Cluster                          M17 Omega Nebula

NGC 6624                    Globular Cluster                     Herschel 400 H50-1

NGC 6626                    Globular Cluster                     M28

NGC 6629                    Planetary Nebula                    Herschel 400 H204-2

NGC 6637                    Globular Cluster                     M69

NGC 6638                    Globular Cluster                     Herschel 400 H51-1

NGC 6642                    Globular Cluster                     Herschel 400 H205-2

NGC 6645                    Open Cluster                         Herschel 400 H23-6

NGC 6647                    Open Cluster                         P108

NGC 6652                    Globular Cluster                     P31

NGC 6656                    Globular Cluster                     M22

NGC 6681                    Globular Cluster                     M70

NGC 6715                    Globular Cluster                     M54

NGC 6716                    Open Cluster                         P109

NGC 6717                    Globular Cluster                     P110

NGC 6723                    Globular Cluster                     P52

NGC 6809                    Globular Cluster                     M55

NGC 6818                    Planetary Nebula                    Herschel 400 H51-4

NGC 6822                    Galaxy                                  C57 Barnard’s Galaxy

NGC 6864                    Globular Cluster                     M75



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