July is here and that means it is officially the summer holidays. School is out and we are all planning our holidays either abroad or at home. Whether you leave the country or stay in it, there will be many things in the night sky to observe.
Here we see a close up look at the Tycho crater (Image credit NASA/GFSC/Arizona State University)
We start off the month with a Full Moon. On 2 July, the night sky will be filled with the light of the Moon, so get out your telescopes and binoculars and have a look at our wonderful, natural satellite. The Native American peoples, particularly the Algonquian Tribe, called this phase the òÀÜFull Buck Moon,òÀÝ as this would have been the time of the year that the bucks would have started to grow their new antlers. It was also known as the Thunder Moon, simply because thunderstorms occurred frequently at this time of year. Other Native American tribes used the name Hay Moon too. Take this time to fully appreciate one of the MoonòÀÙs most iconic features. Tycho Crater is the most prominent impact crater on the MoonòÀÙs surface thank its extensive and bright rays. It was named after Tycho Brahe (1546-1601), a Danish nobleman known for his colourful lifestyle and accurate and very comprehensive astronomical and planetary observations. The crater is relatively young and is located in the southern region of the Moon.
Pluto Approaching Charon: An artistòÀÙs impression of New Horizons flying by Charon, the largest moon of Pluto. (Image credit: NASA)
A very special event is occurring on 14 July. The New Horizons Probe will make its historic passing of the dwarf planet Pluto. Since its launch in January 2006, the New Horizons Probe has already had an eventful journey through our solar system. Its ultimate aim is to reach the worlds at the edge of our solar system, and area of much mystery. It will also venture on to the Kuiper Belt, an asteroid belt that is very much a relic of the formation of our solar system. In 2007, New Horizons flew past Jupiter and as it did it conducted some scientific studies and gain a gravity boost. The probe will conduct a five month long investigation of Pluto as it reaches the dwarf planet and ultimately flies past it. The information gained by the probe of Pluto and its surrounding moons will be of great scientific benefit for the astronomical world and will help us to understand more about the little icy mini world. The closest the probe will come to Pluto will be on 14 July.
On 16 July will see all the stars on display in our sky, as there will be a New Moon. With no moon light in the sky to hinder our stargazing, this is the perfect time to gather your family and friends around, stay up into the small hours of the morning, and gaze at some celestial wonders. Here are a few of our recommendations.
Looking south on 16 July 2015 at midnight we can see Ophiucus and Serpens. (Image credit: Heather Taylor/Armagh Planetarium/Stellarium)
Ophiuchus and Serpens are twoˆà brilliantly visible constellations at this time of the year in the southern part of the sky, and the story behind them is rather fascinating. In Greek mythology Ophiuchus was a notable Healer. Known as Aesclepius, he was the demi-god son of Apollo and Princess Coronis. After Coronis had a sordid love affair with another man, Apollo had his sister Artemis kill the princess, but he saved his unborn son from the funeral pyre. Apollo gave his son the gift of healing and handing him over to the centaur Chiron, who taught him the ways of medicine. Here the mythology varies a bit. It was claimed that Aesclepius became fluent in the ways of avoiding death. Some say it was after he learned this healing trick from a snake, and others claim it was when he observed a snake healing another snake. Either way this angered the gods. In Greek mythology Hades, the God of the Underworld was angry with this outcome and had his brother Zeus kill Aesclepius with a bolt of lightning. In Roman mythology, Jupiter (king of the gods) did not want to see the human race become immortal and so killed Aesclepius with a bolt of lightning. All of the mythology ends up with an image of Aesclepius being placed into the heavens to represent his good works.
One of the most notable patterns in the sky is now very visible in the month of July, the Summer Triangle. Made up of three bright stars, this pattern is not a real constellation, but is an asterism made up of stars from three other constellations. The three bright stars are called Vega (from the constellation of Lyra), Deneb (from the constellation of Cygnus) and Altair (from the constellation of Aquila).LetòÀÙs have a closer look at these three stars.
The Summer Triangle: Looking SE on the 16/07/2015 we can see clearly, the points of the summer triangle with the stars Vega, Deneb and Altair highlighted. (Image credit: Heather Taylor/Armagh Planetarium/Stellarium)
Vega, or Alpha Lyrae, is the brightest star in the constellation of Lyra. It is the fifth brightest star in the night sky, and is the second brightest star in the Northern Hemisphere (with Arcturus taking the top spot). It is a star that is surprisingly close to us here on Earth. When we say close, we mean that itòÀÙs only 25 light years away. It has a magnitude of about 0.03 and is a blue-white star. An interesting fact about Vega is that it was at one stage the Pole Star, and in many years to come, it will once again be the Pole Star thanks to the Earth’s axial precession. One of the most beautiful pieces of mythology surrounding the star Vega comes from Japan. In Japanese mythology Vega, known as Tanabata or Orihime, was a celestial Princess. She fell in love with a mortal called Kengyu (or Hikoboshi, represented by the star Altair). Naturally her father was outraged at this and forbid Tanabata from seeing Kengyu. The two lovers were thrust into the sky and were separated by the Celestial river, known to us as the Milky Way. Each year however, on the 7th night of the 7th moon, a bridge of magpies made a bridge across the celestial river for Kengyu to reunite with Tanabata.
Deneb, or Alpha Cygni, is the brightest star in the constellation of Cygnus. It is the nineteenth brightest star in the night sky. It is a blue-white super giant star and its exact distance from the Earth is still unclear. The current estimation is 2600 light years. It has a luminosity that is nearly 200 000 times that of our own Sun. The name Deneb is derived from the the Arabic word dhaneb, meaning tail. It was originally part of the Arabic phrase òÀÜAl Dhanab al Daj€Ájah,òÀÝ meaning òÀÜthe henòÀÙs tailòÀÝ and Deneb is known as the òÀÜTail of the Swan.òÀÝ
Altair, or Alpha Aquilae, is the brightest star in the constellation of Aquila. It is the twelfth brightest star in the night sky and is currently located in the G-Cloud, an interstellar cloud located next to the Local Interstellar Cloud. It has a visual magnitude of about 0.77 and is roughly 16.7 light-years from the Earth. This star is also rotating very rapidly, in fact its equator is rotating at roughly 185mph. One rotation for this star takes only about 9-10 hours.
Looking towards the East on 29/07/2015 we can just see the star Skat in the constellation of Aquarius. This is where the Delta Aquarids will radiate from. (Image credit: Heather Taylor/Armagh Planetarium/Stellarium)
On 28-29 July we will be privy to the Delta Aquarids Meteor shower, however be wary as there will be an almost full waxing gibbous moon in the sky, so a lot of light will be coming from the moon. This will be a brilliant meteor shower to see if youòÀÙre going on holidays to the southern hemisphere or the tropical latitudes of the northern hemisphere. This meteor shower appears to radiate from the star Skat, or Delta Aquarii. This is the third most prominent star in the constellation of Aquarius. The best time to view this meteor shower is after midnight and through until dawn. You can find the star Skat just below the great square of Pegasus.
Finally on 31 July we will have another full moon in the sky. This moon will be known as a Blue Moon, so yes, Blue Moons do exist! The proper definition of a Blue moon is when a full Moon appears in the sky twice in one month. Naturally these are few and far between and the last Blue Moon was in August 2012. The next Blue Moon we will see after this one in July will be in January 2018. This rare occurrence is what coined the phrase òÀÜOnce in a Blue Moon,òÀÝ which literally means òÀÜvery rarely.òÀÝ
So in conclusion, July 2015 is going to be a very fascinating month for stargazers and astronomy geeks alike. With so many things to see in the sky, the rare Blue Moon and the historic flyby of New Horizons at Pluto we will be talking about this month for months to come. Hopefully August will be as epic as July!
(Article by Heather Taylor, Education Support Officer)
Hi Colin,
Please allow me to differ strongly on the ‘Blue Moon’ in Heather’s otherwise good article about the July sky.
The designation of the second Full Moon in a month being a ‘Blue Moon’ arose from a mistake made in a Sky & Telescope article in the 1990s. When their mistake was pointed out, S&T issued a correction, but unfortunately the correction was missed by some, and so the erroneous definition continued to be spread, particularly by the media.
The expression “Once in a Blue Moon” arose from the VERY rare occasions when the Moon did literally appear blueish, following major volcanic eruptions which put fine dust and aerosols high in the atmosphere, turning the moon a bit blue.
That useage goes back LONG before the S&T article in the 1990s!
1. You, if not Heather, will know that Leif J Robinson is one of the foremost authorities in astronomy education, having been editor of S&T for very many years, and then appointed as Editor Emeritus. His opinion should be enough to settle the matter!
In the Foreword to the Twentieth Edition of Norton’s Star Atlas (aka the astronomer’s ‘Bible’) published in 2004, Leif J Robinson wrote: “Once in a blue moon a book appears that dramatically and forever changes its subject. Equally rare is a book that remains in print for a century…”
That’s hardly the term that one would apply to a phenomenon as common as two Full Moons occurring in the same month, which happens every few years or so. So he obviously was using the term as referring to a very rare and unusual event, such as the Moon literally appearing blue. As Robinson is one of the most respected astronomy writers of the modern era, that should settle the matter!
2. Two Full Moons in the same month is not even a rare event – it happens 5 or 6 times every decade. For example, it happened on 2015 Jan 2 & 31; and it will occur again on 2018 Jan 2 & 31; 2018 Mar 2 & 31; and 2020 Oct 1 & 31. It c an even occur in two successive months! The reason is very simple: the average interval between Full Moons is about 29.5 days, and 11 of the 12 months have either 30 or 31 days.
3. Further, why should the second FM in a month be called a ‘Blue’ moon? – why not Green? or Purple? or Magenta? – Calling it ‘blue’ just does not make sense!
So please – no more promulgation of this erroneous definition!
Terry
Dear Terry, thank you for your comments and detailed account of how the current usage of the term òÀÜblue moonòÀÝ came to be. I am sorry that you did not appreciate HeatheròÀÙs discussion of òÀÜblue moonsòÀÝ, but I am very happy to have published it.
Unlike facts, terminology changes over the years. YouòÀÙre right that the common modern definition of blue moon is based on a misunderstanding, and perhaps if this article had been published several decades ago we would not have approached it this way. ItòÀÙs too late now.
Today in contrast, we are not doing anything to promote modern superstition by referring to total lunar eclipses as òÀÜblood moonsòÀÝ, thatòÀÙs one neologism weòÀÙre trying to nip in the bud before it becomes established!
However the òÀÜsecond full moon in a monthòÀÝ definition of a blue moon is a different matter, being firmly and prominently embedded in popular culture now. If we receive òÀØphone or email queries about blue moons, this is what the enquirer is asking about. Heather pointed out when the previous blue moons occurred so it is clear to the reader that they are infrequent events.
Once again, IòÀÙm sorry this content of this article was not to your taste, but IòÀÙm sure that it has inspired readers to go outside and admire the Moon themselves. That, you must agree, is the most important thing.