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Coma Berenices, Berenice's Hair

Plus the planets for June.

 

The constellation Coma Berenices, Berenice's Hair, is just south of overhead, crossing the meridian early during our June evenings. This constellation is actually named after a historical figure, Queen Berenice II of Egypt, wife of Ptolemy III Euergetes. The famous Greek astronomer Claudius Ptolemy did not include it in his list of 48 constellations in The Almagest, even though he also lived in Alexandria, Egypt, somewhat later. He considered these stars a tuft at the end of the tail of the neighboring Leo the Lion, rather than a separate constellation.

map

(Click the image for a bigger map)

Coma Berenices is high in our southern sky on June evenings. With the Virgo Cluster of Galaxies in southern Coma and the Coma Cluster of Galaxies in the north, there are many galaxies in this constellation. These include the spiral galaxy M100, the elliptical galaxy M85 and the almost edge-on spiral M98. You can also find the interacting galaxies NGC 4676, known as “The Mice” because of the trails of stars that have been pulled out of each galaxy by the other.

Northeast of the Egyptian empire lay the Seleucid Empire. After a falling out at the Selecuid court, Ptolemy III Euergetes' eldest sister, Berenice Phernophorus, was murdered along with her infant son. Because of this murder, Ptolemy III invaded Syria, starting the Third Syrian War.

In prosecuting the war, Ptolemy III undertook a particularly dangerous mission. Queen Berenice II swore to the goddess Aphrodite to sacrifice her beautiful, long blonde hair if her husband returned safely from the mission. When he did, the queen cut off her hair and placed it on the altar in Aphrodite's temple. The next morning, the hair was missing. The court astrologer told the king that Aphrodite had taken the hair and put it in sky as a small group of stars we now know as Coma Berenices.

Even though Claudius Ptolemy did not include it in his list of constellations, he did at one point mention it as a "lock of hair." Coma Berenices did not become a recognized constellation until cartographer Caspar Vopel put it on his 1536 celestial globe. Tycho Brahe, frequently credited with giving Coma its constellation status, did not list it until his 1602 star catalog.

Coma Berenices is composed of about 15 fourth-magnitude stars, scattered in no particular pattern. It also includes two galaxy clusters: One is in the southern part of Coma and extends well into Virgo, so it is called the Virgo Cluster of Galaxies. It is only 60 million light-years away with many bright and beautiful galaxies. The other cluster is much farther away, almost 300 million light-years, in northern Coma. It is called the Coma Cluster of Galaxies. The large distance makes this cluster's galaxies appear faint and small as viewed from Earth.

Coma also boasts a few galaxies that do not belong to either cluster. One is NGC 4314, a barred spiral galaxy in far northeastern Coma. This galaxy is magnitude 11.4 and 4.2 by 3.7 minutes-of-arc across. It was observed in 1976 by Fritz Benedict, who was using a 2.7-meter telescope at McDonald Observatory in western Texas. He was assigned to track Earth satellites for the Air Force, but between passes, he would use the telescope to observe other objects.

When Benedict looked at NGC 4314, it was very smooth with little star formation, probably due to most of the gas being stripped out by a collision with another galaxy. But down in the center of NGC 4314 he saw what looked like a separate little spiral galaxy. This fascinated him and NGC 4314 became his favorite galaxy.

Benedict would work on NGC 4314 on and off. In 1993 he observed it with the Hubble Space Telescope and was able to resolve its very center, finding a ring of active star formation regions. The young stars in this nuclear ring are incredibly young, only 1 million to 15 million years old, while the whole galaxy is around 10 billion years old.

The star-forming ring is only about 1,000 light-years across — tiny compared to the rest of the galaxy. The tiny spiral Benedict saw in the center of NGC 4314 was dust that had been stripped out of the galaxy in the original collision, but was being pulled back and falling all the way to the nuclear ring to form these young stars. While these (and other) observations have explained the overall mystery of NGC 4314, there is still much more to learn about the interactions between the inner nuclear ring and the rest of the galaxy.

 

The Planets for June

 

Mars and Jupiter are too close to the Sun to be seen this month, but Venus, Mercury and Saturn are all in our evening sky. Last month, Venus, Jupiter and Mercury were close together, but this month we will have Mercury traveling downward, passing Venus, as it leaves the evening sky.

Watch the Skies
(times MDT)

 

June 8, 9:56 a.m. — New Moon
June 12, 11 a.m. — Mercury 24° east of Sun
June 16, 11:24 a.m. — First Quarter Moon
June 20, 11 a.m. — Mercury 1.9° south of Venus                  11:04 p.m. — June Solstice
June 23 — 5:32 a.m. — Full Moon
June 29 — 10:53 p.m. — Last Quarter Moon

 

Mercury will start the month about four degrees above and slightly to the right of Venus, about 13 degrees above the west-northwestern horizon as it gets dark. Mercury will continue to move upward faster than Venus, until it approaches its farthest point from the Sun on June 12. Venus will then catch up with Mercury and pass two degrees north of it on June 20. Mercury then turns westward and heads back toward the Sun, disappearing into the twilight by the end of the month. At midmonth, Mercury will be magnitude +0.9 and its disc will be 8.8 seconds-of-arc across. The disc will be 31% illuminated, becoming more of a crescent each day. The Messenger of the Gods spends the entire month in Gemini, first traveling east and then turning around and heading west. It sets around 9:55 p.m.

Venus starts the month in far eastern Taurus, travels eastward across all of Gemini and ends the month in Cancer. At midmonth it sets around 9:45 p.m. and shines at magnitude -3.9. The Goddess of Love's disc is 93% illuminated and 10.6 seconds-of-arc across, becoming less full as the month goes on.

Saturn is 44 degrees up in the south-southeast as it starts to get dark. It is spending the month in Virgo, very near the 4.2-magnitude star 98-Kappa Virginis. Now well after opposition, the Ringed Planet shines at magnitude +0.4, with a disc 18.1 seconds-of-arc across at midmonth. The Rings are 41.0 seconds-of-arc across and tilted down 17.2 degrees with the northern face showing. Saturn sets around 3:20 a.m.

The Sun reaches its northernmost point in our sky on June 20 for the June Solstice. This marks the beginning of astronomical summer in the northern hemisphere. This will be the longest day of the year, with the corresponding shortest night, so make the most of our few hours of darkness and "keep watching the sky"!

 

 

 

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

 

 



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