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Lupus, the Wolf

An old constellation leads to supernova observation

In the desert southwest, wolves can be a very controversial topic. But there is one wolf that does not bother anyone. It is just above our southern horizon as it gets dark. The constellation Lupus, the Wolf, is standing straight up on his tail and looking like he about to fall over on his back. This is an old constellation, being on Ptolemy’s list of 48 constellations from the second century A.D.


This constellation was once part of Centaurus, possibly a wine-skin he was holding. Hipparchus of Bithynia carved it out from Centaurus in the 200s B.C., naming it as some kind of wild beast. It went through a number of transformations until the name was translated into Greek as wolf. Lupus is not associated with any specific story from Greek mythology.

Near the Centaurus-Lupus border, just east of the line connecting Beta Lupi and Kappa Centauri, astronomers found a faint circular nebula about half a degree across. When they observed it in X-ray in the early 1960s, they found that it was similar to the Crab Nebula, which had just been identified with the well-known supernova of 1054 A.D. Astronomer Alister Cameron speculated that all of the supernova remnants would emit x-rays. He knew of a historical observation of a very bright object in 1006 A.D. that might well be a supernova, but at the time (1965) was thought to be a comet.

Cameron suggested to his young friend, Bernhard Goldstein, that this might actually be a supernova.

Goldstein, then a young historian at Yale, began a painstaking search through Arabic and other records. His final conclusion was that the 1006 A.D. object had been confused with another in 837 A.D., causing both to be thought to be a comet, but they were both actually supernovae.

The supernova of 1006 was observed all over the world. The Chinese records showed it appeared on April 30 or May 1, 1006. The object was so bright it was visible in the daytime. It was estimated the supernova of 1006 brightened to magnitude -7.5, some ten time brighter than Venus. This is the brightest supernova ever observed and was the third brightest object in the sky after the sun and moon.

The location of this supernova is very far south, but even so, it was recorded by the monks of the Abbey of St. Gall, in Switzerland, where this supernova would have been just about five degrees above the horizon in 1006. They described it as “dazzling to the eyes”. This was the northernmost observation of this supernova, complementing those in China, Japan, Iraq, Egypt, Europe and America.

The supernova was reported to have been visible for three years. It was brilliant for about three months. SN 1006 then faded somewhat and then it brightened up again for about eighteen months. This is emblematic of a Type Ia supernova. These supernova occur in a binary (or more) star system. The larger star ages more quickly and sheds its atmosphere. The remaining core of the star becomes a white dwarf star.

The white dwarf draws material from is aging companion star that has ballooned up as it becomes a giant star. The material the white dwarf acquires builds up on the surface of the white dwarf, compressing the white dwarf and heating it up. At some point, the carbon and oxygen in the dwarf’s core start to fuse into heavier elements releasing even more heat. At some point, a substantial fraction of the carbon and oxygen fuse in just a few seconds, creating a huge pulse of energy that blows the star apart.

Most Type Ia supernovae release about the same amount of energy. What made SN 1006 so bright is that it was only 7,200 light-years away. This is far enough away that the Earth was not affected by the blast, but close enough to make it amazingly bright.

The unusual brightness of this supernova caught the attention of the Native Americans in what is now the Phoenix area who were called the Hohokam. There, in the White Tanks Regional Park, is a rock carving, or petroglyph, that appears to show a bright star near Scorpius. It very closely matches the location of SN 1006 in the sky at that time. If it is does represent the supernova, it is the earliest known depiction of a supernova in North America.

The Planets for July 2015.

Mars is now west of the Sun but still too close to it to be seen in July. Venus and Jupiter, however, are in our western sky as it gets dark. Both are now heading toward the Sun marking their last month in our evening sky. The two were only a third of a degree apart at the end of the last month, but Venus is now moving southward away from Jupiter. At midmonth, the pair is about fourteen degree up in the west as it gets dark and they set around 10 p.m. Venus’s disc is 41.6 seconds-of-arc across and is a 20% illuminated crescent at midmonth. The Goddess of Love shines at magnitude -4.7 and stays in southwest Leo all month. Its temporary companion, Jupiter, shines at magnitude -1.8, as it moves slowly eastward in western Leo. Its disc is 31.3 seconds-of-arc.

Watch the Skies

Calendar of Events – July 2015 (MDT)


July 1 — 8 am Venus 0.4° south of Jupiter
July 1, 8:20 p.m. — Full Moon
July 8, 2:24 p.m. — Last Quarter Moon
July 15, 7:24 p.m. — New Moon
July 18, 8 p.m. — Venus 0.8° north of Moon
July 23, 10:04 p.m. — First Quarter Moon
July 31, 4:43 a.m. — Full Moon
July 31, 2 p.m. — Venus 6° south of Jupiter

The Ringed Planet is moving slowly westward in eastern Libra, slowing down toward the end of the month. Saturn is forty degrees up in the south, shining at magnitude +0.4 as it gets dark and sets around 2:40 a.m. At midmonth, its rings are 40.7 seconds-of-arc across, and they are tilted down 24.0 degrees with the northern face showing. The disc is 17.7 seconds-of-arc across.

Mercury’s brief appearance in the morning sky that started at the end of last month concludes at the beginning of this month. It is only visible for the first week of July before it gets lost in the Sun’s glare. On July 1, the Messenger of the Gods’ disc will be 6.9 seconds-of-arc across and will be 53% illuminated. It will be eight degrees above the east-northeastern horizon as it starts to get light, having risen at 4:45 a.m. Mercury starts the month travelling eastward in eastern Taurus, skimming through very northern Orion, through all of Gemini and ending the month in eastern Cancer. So say goodbye to Mercury in the morning and keep watching the sky!

Astronomical society needs people with interest in the sky

Kathy Anderson, founding director of the Silver City Astronomical Society, has announced that unless someone with an interest in the stars steps up, the current board of directors will have to dissolve the organization.

The SCAS is a bona fide 501(c)(3), has money in the bank, owns equipment, and has much by way of educational materials.

Anderson resigned from the board last summer because she and her husband were leaving the area. Other members of the board have not been able to fully assume the responsibilities and are no longer able to do so.

“It doesn’t take a rocket scientist to run a small astronomy club,” Anderson said. “Have meetings every now and then, invite the public, go gaze at the stars if you’d like.”

Anyone interested in becoming a board member or otherwise helping out with the club can contact Anderson at QHOearth@gmail.com.

An amateur astronomer for more than 40 years, Bert Stevens is co-director
of Desert Moon Observatory in Las Cruces.

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