BAS - Monthly Sky Guide

Transcription

1 BAS - Monthly Sky Guide June 2018 June brings the dense central bulge of our Milky Way Galaxy into view in the eastern sky. This is a great time for hunting nebulae and globular clusters as Scorpius and Sagittarius come into view. 1

2 Dark Sky Best Observing Dates - June From June 7 th the Moon rises after midnight, providing plenty of evening dark sky hours After June 15 th the Moon sets a little later after sunset each evening and so eats into early evening observing time Best nights for plenty of observing hours are from about June 7 th, when the Moon rises after midnight, to around June 15 th when the slim waxing Moon sets a little after sunset. 2

3 Useful Telescope Alignment Stars Scorpius Alignment Stars: Antares Arcturus Two prominent and widely spaced stars that make good alignment stars are Arcturus in the constellation Bootes and Antares in the constellation Scorpius, the Scorpion. We ve pointed out Arcturus in previous months so it should be relatively easy to find by now. Scorpius is an easy constellation to find as it will be high overhead and its curly tail is very suggestive of the arachnid beast. Antares is a great alignment star as its distinctive bright orange colour is impossible to mistake for any other star in this part of the sky. So align with confidence on Antares. 3

4 Constellation of the month - Centaurus Observing targets: NGC 5128 galaxy NGC 5139 globular cluster Centaurus is one of the largest constellations in the sky. It represents the centaur, the half man, half horse creature in Greek mythology. Sources tend to differ on which centaur the constellation represents, but usually it is taken to be Chiron. Chiron was a well-known and respected teacher of medicine, music and hunting. He lived in a cave on Mount Pelion and taught many young princes and future heroes. He died a tragic death in the end, accidentally struck by one of Heracles arrows, which the hero had dipped in Hydra s blood, a poison for which there was no cure. Being the son of the immortal Cronus, Chiron was himself immortal. When the arrow struck him, he suffered terrible pains, but could not die. Zeus eventually released the centaur from immortality and suffering, allowing him to die, and later he placed him among the stars. Centaurus contains two of the top ten brightest stars in the sky: Alpha Centauri and Beta Centauri. It is also home to Centaurus A (NGC 5128), one of the brightest galaxies in the night sky, and to the globular cluster Omega Centauri (NGC 5139). 4

5 The Moon Vesta Moon Find the minor planet, Vesta, very close to the Moon from sunset, June 27 th. From around sunset on June 27 th the minor planet Vesta will be very close to the Moon and slowly rising higher along the ecliptic above the Moon in subsequent hours. With the Moon as a location indicator this will be a great opportunity to accurately identify and observe the minor planet Vesta. Vesta, is one of the largest objects in the asteroid belt, with a mean diameter of 525 kilometers. 5

6 New Moon - 9 PM meridian constellations Triangulum Australe Corona Borealis A couple of constellations in the sky along the meridian at about 9 PM during the new Moon period are the southern constellation Triangulum Australe and the northern constellation Corona Borealis their Latin names even indicate they are of the south and the north. Triangulum Australe is something of an astro-desert with just a few catalogued deep sky objects within reach of amateur telescopes a quick look at a few globular clusters can tick this constellation off an observer s list. However Corona Borealis, the Northern Crown, is a little more interesting with a scattering of distance faint galaxies. 6

7 Constellation of the month - virgo Observing targets: Messier 49 - galaxy Messier 87 - galaxy The constellation Virgo, The Maiden, is another ancient Greek constellation defined in AD 100 by Ptolemy. Greek myths say she longed so much for a more just and righteous world and despaired so much at the moral decay on Earth that she cast herself into the heavens to escape the chaos. Virgo is best known to astronomers as home to one of the great concentrations of distant galaxies it is home to the Virgo Galaxy Cluster comprising about 1,300 galaxies. The largest galaxy is the elliptical monster Messier 87 located about 60 million light years away. The galaxy Messier 49 is another very bright member of the cluster. 7

8 The Planets Jupiter Saturn Mars Mid-month in the early evening we will have Jupiter and Saturn high in the sky and well placed for observing, with Mars low in the eastern sky. June will be an excellent month for observing Jupiter and Saturn. 8

9 Meridian Constellations Virgo Bootes Virgo is one of the 12 zodiac constellations, first catalogued by the Greek astronomer Ptolemy in the 2nd century. In Greek mythology Virgo is usually depicted with angellike wings, with an ear of wheat in her left hand, marked by the bright star Spica. Virgo is usually associated with the Greek goddess of justice, Dike. Dike was born a mortal and lived on Earth to rule over human justice. However, as humans became more warlike in the bronze and iron ages she turned her back on humanity and flew to the heavens. The constellation s Bootes name comes from a Greek word which means ox driver, plowman, or herdsman. The constellation was first catalogued by the Greek astronomer Ptolemy in the 2nd century. Bootes is traditionally depicted as a herdsman with two hunting dogs on a leash and a club in his other hand. Bootes follows Ursa Major around the pole. In one story, the constellation represents a ploughman driving the oxen in the Ursa Major constellation, followed by his two dogs. The ploughman s oxen are tied to the polar axis and their movement keeps the skies in constant rotation. 9

10 Virgo The biggest and brightest galaxy in Virgo is Messier 87. It is a supergiant elliptical galaxy and one of the most massive galaxies in the local Universe. While our Milky Way has only about 150 globular clusters, M87 has over 12,000 globular clusters orbiting through its massive star cloud. M87 is a huge elliptical galaxy in the heart of the Virgo galaxy cluster and part of the beautiful string of galaxies called the Markarian Chain that stretch across the sky like links in a chain. 10

11 Virgo Galaxy Cluster But there are approaching 2000 galaxies in this wider Virgo Cluster that will take a life time of observing to hunt down. Find some dark sky, a large telescope and plenty of patience, and start hunting. 11

12 Bootes Bootes lacks the galaxies and wow-factor of Virgo. But one object worth seeking out is the globular cluster NGC 5466, or the Snowglobe Cluster. Perhaps most globular clusters resemble a well shaken snowglobe, but this one gets the title. It is 51,800 light years away from Earth and so makes a good deep-sky catch for a small telescope. 12

13 Build your own observing list Click Find Objects Select object types Select constellation Search Make sure you take a look at the great observing planning tool DSO-Browser before the New Moon period. This is a fantastic tool to help you build a list of objects you can try and find each month. Just a few clicks on can generate a fantastic observing list of object types you are interested in. 13

14 Avoiding clouds More info: And the find the best cloud-free evenings for observing make sure you check CloudFreeNight and Skippysky as you plan your next observing evening. 14