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Looking Deep...Very Deep!

by Geoff Chester, USNO Public Affairs | 16 May 2023

by Geoff Chester, USNO Public Affairs | 16 May 2023

NGC 4565, the "Needle Galaxy" in Coma Berenices, imaged 2022 May 29 from Mollusk, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor and a ZWO ASI183MC CMOS color imager.
This galaxy is one of the brighter members of the Virgo cluster and lies about 50 million light-years away.

The Moon returns to the evening sky by the end of the week.  New Moon occurs on the 19th at 11:53 am Eastern Daylight Time.  You should be able to see Luna’s slender crescent low in the northwestern sky on the evening of the20th.  On the 22nd she may be found below the dazzling glow of Venus, and on the following evening she lies near the star Pollux in Gemini, squarely between Venus and ruddy Mars.

The May campaign for the Globe at Night citizen science program continues through the evening of the 21st.  By 10:00 pm the sky is dark enough to locate the target constellation of Leo, the Lion, just west of the meridian.  Most city dwellers should be able to spot the constellation’s brightest star, Regulus, high in the west at this time.  It is rather isolated from other bright stars; the closest are the second-magnitude star Algieba, just under 10 degrees north of Regulus, and the star Denebola, located some 24 degrees to the east.  These three stars are Leo’s brightest members.  Under darker sky conditions the constellation is recognized by two distinctive asterisms.  The first, featuring Regulus and Algieba, looks somewhat like a backwards question mark and is popularly called The Sickle.  Denebola marks the Lion’s tail and forms a right triangle with two other stars, Zosma and Chertan. 

The spring sky has a few constellations that are fairly easy to identify, such as Leo and the “Big Dipper” asterism of Ursa Major, the Great Bear.  However, one of the more unusual star patterns that are front and center in the spring occupies the space between Denebola, the “tail” of Leo, and Arcturus, the brightest star in the northern sky.  You need to find a dark location to spot the group, known as Coma Berenices, or Berenice’s Hair.  With no stars brighter than fourth magnitude, it is nonetheless one of the oldest constellations in the sky, first described by astronomer Conan of Samos in the Third Century BCE.  Conan was the court astronomer to the Egyptian Pharaoh Ptolemy III to honor the latter’s queen, Berenice II.  According to legend, Berenice had a head of exquisitely long hair, which she cut off and sacrificed to Aphrodite to ensure her husband’s safe return from battle.  The tresses mysteriously disappeared from the altar in the temple, but the quick-thinking Conon showed the queen the scattered stars of the constellation and convinced her that the sacrifice had been accepted and placed in the heavens by Aphrodite.  Ptolemy returned, and Berenice’s sacrifice remains to remind the world of her devotion.

From a dark site, Coma Berenices is a scattering of some two dozen faint stars sprinkled between a right angle made of three fourth magnitude stars.  It is actually a nearby star cluster consisting of about 50 stars located some 280 light-years away.  For owners of small telescopes, there are a number of attractive double stars, while larger instruments will begin to show the faint smudges of distant external galaxies.  Coma is also the location of the north pole of our Milky Way galaxy, so when we look in this direction we are looking past relatively few Milky Way members.  Indeed, it’s almost as if we are looking through a portal into the deepest reaches of space.  Behind the scattering of Milky Way stars lie two distinct clusters of external galaxies.  The first is the northern section of the Virgo Cluster, of which our Milky Way is an outlying member, some 50 million light-years from the cluster’s center.  Many of these galaxies are visible in modest aperture amateur telescopes. 200 million light-years beyond the Virgo cluster is the realm of the Coma Supercluster, a massive grouping of some 10,000 galaxies.  The faint wisps of light from these distant objects began traveling toward Earth before the dinosaurs roamed our planet.

Venus is still dominant in the western twilight sky as she crosses the constellation of Gemini, the Twins.  She continues to move steadily eastward under the Twin Stars, Castor and Pollux.  She has passed her most northerly declination and is gradually beginning to drop toward the advancing Sun.  She gets a visit from the crescent Moon on the evenings of the 22nd and 23rd.  On the latter evening Venus, the Moon, and Mars will present a nice alignment in front of the Twin Stars.

Mars pulls away from Castor and Pollux and enters the dim constellation of Cancer, the Crab.  By the end of the week he will lie just over five degrees west of the “Beehive” star cluster, which can be easily located with binoculars.  He will pass through the cluster on June 1st and 2nd.

Golden Saturn greets early risers from a perch in the southeastern sky as morning twilight begins to gather.  By 5:00 am the ringed planet will be high enough for a look through the telescope.  If you enjoyed the wide-open aspect of the rings last fall, you will find that they have closed up by about five degrees compared to last year.


Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529

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