What's Up in the Night Sky

July 2024 - Vol. 28, No. 7

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.

Bright blue-white Vega (Lyra) shines high overhead as it "leads" the Summer Triangle across the night sky. The "Triangle" is the Summer’s most prominent asterism and is made up of three stars: Vega, the brightest, Deneb (Cygnus) and Altair (Aquila). In the southwest, Arcturus (Bootes) is dropping towards the horizon as Spica (Virgo) vanishes from sight below. Also look for Antares (Scorpius) low in the South. The stars of constellations Scorpius and Sagittarius, embedded in the Summer "Milky Way" are at their best this month. Look for another popular asterism, "The Teapot", made up of the brightest stars of Sagittarius. Also the "Great Square of Pegasus" now appears on the Eastern horizon just before the onset of morning twilight. These are the stars of autumn that will take over when the northern summer wanes!

MERCURY in the evening sky favors southern observers. VENUS, close to the Sun after last month's superior conjunction, reappears gradually favoring southern observers. MARS moves into Taurus this month rising in the morning sky, has a close conjunction with Uranus on the 15th. JUPITER in Taurus, continues to rise in the morning twilight. SATURN is now moving in retrograde motion and rises before midnight starting in the second week of the month. URANUS rises in the morning sky. NEPTUNE resides in Pisces, for those with telescopes.

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	Mars 4 deg. S. of Moon.
02	Moon 0.3 deg. S. of the Pleiades star cluster (M-45). Uranus 4 deg. S. of Moon.
03	Jupiter 5 deg. S. of Moon. Neptune stationary.
05	Earth at aphelion.
06	Asteroid Ceres at opposition.
7	Mercury in the Beehive star cluster (M-44). Mercury 3 deg. S. of the Moon.
10	Venus at perihelion.
12	Moon at apogee.
14	Alpha Virginis, Spica, 0.9 deg. S. of Moon, occultation from eastern tip of Russia, North and Central America, and Caribbean.
15	Mars 0.6 deg. S. of Uranus. This conjunction may fit into one eyepiece on a telescope with the appropriate field of view.
17	Alpha Scorpii, Antares, 0.2 deg. S. of Moon, occultation from Cape Verde is., parts of Africa, and Madagascar.
21	July's full moon is often called the "Buck Moon" because it is the time of year that young buck deer begin showing antlers in North America.
22	Mercury at greatest elongation E. (27 deg.)
23	Pluto at opposition. (Get your large telescope out!)
24	Moon at perigee. Saturn 0.4 deg. S. of the Moon, occultation from E. Africa, Madagascar, most of S. Asia, NW Indonesia, most of China and Mongolia, Japan, and SE Russia.
25	Neptune 0.6 deg. S. of Moon, occultation from most of Melanesia, Micronesia, W. Hawaii, NW North America.
27	Mercury at aphelion.
28	S. Delta Aquariid meteors peak, this shower produces up to 20 meteors at its peak. (23h UT)
29	Moon 0.1 deg. S. of the Pleiades star cluster (M-45). Uranus 4 deg. S. of Moon.
30	Mars 5 deg. S. of Moon.
30	Venus at greatest heliocentric lat. N. Jupiter 5 deg. S. of Moon.

Lunar Almanac for July 2024

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 05	Deep Space Objects
	1st. Qtr 13	Planets & Moon
	Full 21	Moon
	Last Qtr 27	Deep Space & Planets

The Blaze Star, Waiting for 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