What's Up in the Night Sky

September 2024 - Vol. 28, No. 9

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

The Summer Triangle asterism, Vega (Lyra), Deneb (Cygnus) and Altair (Aquila), is still quite prominent overhead as darkness falls. Arcturus (Bootes) is now dipping to the NW horizon. From a dark site, the myriad stars of the Milky Way (the visible "arm" of our galaxy), "flow" eastwards through the "W" asterism of Cassiopeia and to bright Capella (Auriga) glowing in the NE. "The Great Square of Pegasus" asterism burns high in the SE while lonely Fomalhaut (Piscis Austrinus) shines far below, very close to the horizon. "The Big Dipper" asterism (Ursa Major) is nearly horizontal and now sits low on the N horizon. In the E, Aldebaran(Taurus) shines, a sure sign of Autumn.

MERCURY emerges into the morning sky beginning the best morning apparition in 2024 for northern observers. VENUS in the evening sky, becomes more prominent as the month continues. MARS moves into Gemini on the 5th, shining at magnitude 0.6 by month's end. JUPITER rises before midnight for northern observers. SATURN reaches opposition on September 8th. URANUS, in Taurus will be stationary on September 1, and begins retrograde motion. NEPTUNE is in Pisces, reaches opposition on September 21.

Review how to determine Angular Measurement.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time. Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times or check with the U.S. Naval observatory. Unfortunately some of these events may occur during daylight hours in your area.

DATE	EVENT
01	The Zodiacal Light or "false dawn" is visible in the E about 2 hours before sunrise. This pyramidal glow is caused by meteoroids, dust particles spawned by passing comets, etc., that have settled into the ecliptic plane (path followed by the Sun, Moon and planets), reflecting the Sun’s light before it rises here. This phenomenon will be visible until about September 14th although the Moon may interfere. Mercury 5 deg. S. of the Moon. Uranus stationary.
05	Moon at apogee. Venus 1.2 deg. N. of Moon, occultation from extreme south locations. Mercury at greatest elongation W (18 deg.)
06	Mars at ascending node. Alpha Virginis, Spica, 0.5 deg. S. of Moon, occultation from NE North America, Bermuda, Azores, Ascension Is., parts of Africa.
08	Saturn at opposition. Mars 0.9 deg. S. of the open star cluster M35.
09	Mercury at perihelion. Mercury 0.5 deg. N. of Regulus, Alpha Leonis.
10	Alpha Scorpii, Antares, 0.1 deg. N. of Moon, occultation from S. half of Africa, Madagascar, Kerguelen Is., west and central Australia, SE Indonesia.
17	Saturn 0.3 deg. S. of the Moon, occultation from northern Australia, Melanesia, S. and E. Micronesia, NW Polynesia, (Hawaii), central and W. North America.
18	Partial Lunar eclipse. The eclipse will be visible from West Europe and Africa, Eastern N. America and South America. September's full moon is often called the "Harvest Moon" because it is the time of year that farmers in North America harvest many crops. Moon at perigee, expect large tides. Neptune 0.7 deg. S. of Moon, occultation from N. Polynesia, North America (excluding Alaska, SE USA, and Mexico), and W. Greenland.
19	Mercury at greatest heliocentric latitude N.
21	Neptune at opposition.
22	Equinox, hours of day and night are equal. Moon 0.2 deg. N. of the Pleiades star cluster (M-45).
23	Jupiter 6 deg. S. of Moon.
25	Mars 5 deg. S. of Moon.
26	Alpha Geminorum, Pollux, 1.7 deg. N. of Moon.
30	Mercury at superior conjunction.

Lunar Almanac for September 2024

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 02	Deep Space Objects
	1st. Qtr 11	Planets & Moon
	Full 17	Moon
	Last Qtr 24	Deep Space & Planets

The Blaze Star, Awaiting the Outburst of T Coronae Borealis

Astronomers call it, "Blaze Star" because of its volatile nature, it seems to produce a nova about every 80 years. Ordinarily a tiny 10th magnitude star in a small northern constellation, T Corona Borealis (aka T CrB) is a legend among variable star observers. It was discovered as a nova star in May of 1866 by three astronomers and soon after spectroscopic analysis was used to separate it into two components. This double star pair consists of a white dwarf and a red giant star that are located about 3000 light years from earth. It is believed the white dwarf pulls matter off of the aging red giant, building up an accretion disk around the white dwarf until the material compresses and ignites a runaway nuclear explosion. During nova phase, T CrB rises to 2.0 magnitude, observable by the naked eye in a dark sky. The two stars are known to have a period of 227.57 days, but it is disrupted by the nova phase.

The Blaze star is labeled T in the constellation of Corona Borealis, the northern crown. It is small semi-circle of stars, most of them around 4th magnitude, except for the alpha star that is the brightest jewel of the crown, called "Alphecca" or (my favorite) "Gemma". Alphecca is the brightest star of the constellation, shining at 2.2 but when T CrB hits its temporary magnitude of 2.0, it outshines Alphecca. This does not last long and ten hours later, the brightness begins to fade. To enjoy this special reoccurring nova, observers need to look for Corona Borealis and study its normal appearance so they can identify the nova star.

As soon as twilight ends and the sky is dark this month (~10 pm local time in mid-North America) Corona Borealis can be found directly overhead. We have provided a finder chart, showing Corona Borealis between the constellations of Boötes and Hercules.

finder chart for Corona Borealis — Corona Borealis Finder Chart

T Corona Borealis (may be called, "T-Cor-Bor") is expected to erupt sometime before the end of September 2024, but the actual date is unknown. If you haven't started looking for it yet, go out and find the northern crown constellation and study it so you can enjoy the sight of a "new star"!

The observations that have given us the information of the T Corona Borealis is largely gathered by amateurs astronomers and others that are members of the American Association of Variable Star Observers (AAVSO). If you are interested in contributing, they would be happy to help you get started.

--See You Under the Stars!
Astra for Astra's Almanac