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Algol eclipse dates and times for November 2021
Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star", most of the time it shines at mag. +2.1 but every two days, 20 hours and 49 minutes it suddenly dips in brightness to mag. +3.4, remaining dim for about 10 hours before returning to its original state.
Why the brightness change. The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary, resulting in a very small dip in brightness that can be detected with photo-electrical equipment.
Algol eclipse dates and times for October 2021
Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star", most of the time it shines at mag. +2.1 but every two days, 20 hours and 49 minutes it suddenly dips in brightness to mag. +3.4, remaining dim for about 10 hours before returning to its original state.
Why the brightness change. The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary, resulting in a very small dip in brightness that can be detected with photo-electrical equipment.
Messier 35 - M35 - Open Cluster
M35 is a fantastic open cluster located in the constellation of Gemini. At magnitude +5.2, it's visible to the naked eye under good conditions. Curiously, despite being a naked eye object, it wasn't discovered until 1745-46 by Philippe Loys de Chéseaux and then independently "re-discovered" by John Bevis sometime before 1750. Since the cluster is reasonable close at 2,800 light-years it presents a large apparent diameter of some 28 arc minutes - almost exactly the same as that of the full Moon. Without a doubt, M35 is a magnificent sight in all types of optical instruments.
The constellation Gemini covers a reasonable 514 sq. degrees and is partially located in the rich star fields of the Milky Way. During the winter months, it's positioned high in the sky for Northern Hemisphere observers although less well placed for those located further south. Surprisingly, despite such a prime Milky Way location, M35 is the only Messier object in Gemini. It's located at the western edge of the constellation in a corner of the sky close to the Taurus, Orion and Auriga borders. Finding M35 is quite easy as it's 3.5 degrees northwest of mag. +2.9 star, Mu (μ) Gem.
Algol eclipse dates and times for September 2021
Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star", most of the time it shines at mag. +2.1 but every two days, 20 hours and 49 minutes it suddenly dips in brightness to mag. +3.4, remaining dim for about 10 hours before returning to its original state.
Why the brightness change. The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary, resulting in a very small dip in brightness that can be detected with photo-electrical equipment.
NGC 2477 - Open Cluster
NGC 2477 is a stunning open cluster located in the Milky Way rich constellation of Puppis. It's arguably the constellation's finest cluster, which also contains other superb examples such as M46, M47 and M93. At magnitude +5.8, NGC 2477 is faintly visible to the naked eye, but easily seen with binoculars and a fantastic telescope object especially in medium to large scopes. It's listed as number 71 in the Caldwell catalogue.
The cluster was discovered by French astronomer Nicolas Louis de Lacaille during his tour of South Africa in 1751-52. In total it contains about 300 stars packed into an area 27 arc minutes in diameter with the brightest member star shining at magnitude +9.8. The four-magnitude difference between the combined cluster magnitude and the brightest component is an indication of how rich the cluster is.
NGC 2477 is too far south to have been included in Charles Messier's catalogue, but if he had observed from a more southerly latitude than Paris he almost certainly would have noticed this striking object. Twentieth century America astronomer Robert Burnham described NGC 2477 as "probably the finest of the galactic clusters in Puppis".
The cluster is easily found 2 degrees northwest of zeta Pup (ζ Pup - mag. +2.2) and just northwest of magnitude +4.5 star, b Pup. Located 1.5 degrees west of NGC 2477, and in the same binocular field of view, lies large loose open cluster NGC 2451. Another binocular open cluster, NGC 2546, is positioned 4 degrees east of NGC 2477. They are best seen from southern latitudes during the months of December, January and February.
Messier 85 - M85 - Lenticular Galaxy (or Elliptical Galaxy)
M85 is a lenticular or elliptical galaxy located in Coma Berenices that's a member of the Virgo cluster of galaxies. At magnitude +9.5 and covering 7.1 x 5.5 arc minutes, it's similar in brightness and size to another Virgo cluster galaxy, M84. Spotting M85 with 7x50 or 10x50 binoculars is challenging and dark skies and good seeing conditions are a must. Small 80mm (3.1-inch) refractors, reveal a featureless ball of fuzz with a slightly brighter core. The view through amateur scopes in no way reflects the true nature of this distant object. It's a large galaxy that's located 60 million light-years away, making it one of the most remote objects in the Messier catalogue. Its actual diameter is 125,000 light-years and it's estimated to contain 400 billion stars. Long classified as a lenticular galaxy of type S0, recent observations have suggested M85 could be an elliptical galaxy of type E1.
Pierre Méchain discovered M85 on March 4, 1781. He reported the discovery to his friend Charles Messier, who subsequently catalogued it on March 18, 1781. On that night, Messier was very active. He discovered another seven galaxies, all of them Virgo Cluster members and also re-discovered bright globular cluster M92.
The main crux of the Virgo cluster lies about halfway along an imaginary line connecting Denebola (β Leo - mag. +2.1) with Vindemiatrix (ε Vir - mag. +2.8). Most of the group members can be found in this region of sky. However, M85 is located at the very northern edge of the cluster, some 6 degrees northwest of the group centre and one degree northeast of star 11 Comae Berenices (mag. +4.7).
It's best seen during the months of March, April and May.
Algol eclipse dates and times for August 2021
Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star", most of the time it shines at mag. +2.1 but every two days, 20 hours and 49 minutes it suddenly dips in brightness to mag. +3.4, remaining dim for about 10 hours before returning to its original state.
Why the brightness change. The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary, resulting in a very small dip in brightness that can be detected with photo-electrical equipment.
Arcturus - Alpha Boötis - α Boo
Arcturus, mag. -0.04, is an orange giant that's usually regarded as the fourth brightest star in the night sky. However, it does have justifiable claims for third position since it's marginally brighter than both main components of the Alpha Centauri system. Arcturus is the brightest star in the northern section of the celestial hemisphere.
Arcturus is the stand out star in the large constellation of Boötes, the Herdsman or Plowman. A vague legend has it that the herdsman was placed in the heavens for successfully inventing the plough. The constellation's next brightest star, Izar (ε Boo), shines at magnitude +2.35 and is much fainter than Arcturus. As a bright night time star, Arcturus has been significant to observers since antiquity. It was mentioned in the Bible and featured on old Chinese maps with the name Dajido. In India, it was sometimes referred to as Nishtya or the Outcast, presumably because of its position in the sky far away from the zodiac and Milky Way band.
The name Arcturus derives from Arktouros, which means in ancient Greek the "Bear's Tail" or the "Keeper of the Bear". The name in Greek literature goes back to at least the time of Hesiod, who wrote about this star in his book "Works and Days." Despite being a beautiful star, Arcturus has not always been held in high regard. For example, seamen of ancient times regarded it as an unlucky omen.
More recently, Ptolemy called it "golden red" and curiously, in 1852, some well-respected astronomers observed a change in the star's colour, before it reverted back to normal a few years later. It's difficult to believe anything intrinsically had changed as Arcturus is not that type of star and it's more likely the "colour changes" were simply due to atmospheric effects.
Messier 97 - M97 - The Owl Nebula (Planetary Nebula)
M97, also known as the Owl Nebula, is a famous planetary nebula located in the constellation of Ursa Major. It was discovered by Pierre Mechain on February 16, 1781 and is one of only four planetary nebulae listed in the Messier catalogue. Although not particularly bright at magnitude +9.9, it's a superb object and regarded as one of the most complex examples of its type. The name Owl Nebula was first coined in 1848 by William Parsons the 3rd Earl of Rosse, who noticed owl-like "eyes".
Locating M97 is easy as it's positioned only 2.5 degrees southeast of bright star Merak (β UMa - mag. +2.3). This is the southwest corner star of the bowl of the famous Plough or Big Dipper asterism of Ursa Major. In the same wide field telescope field of view, 50 arc minutes northwest of M97, is barred spiral galaxy M108 (mag. +10.2).
The Owl Nebula is best seen from Northern Hemisphere latitudes during the months of March, April and May. From latitudes north of 35N, it's circumpolar and therefore never sets.
Finder Chart for M97 - pdf format (credit:- freestarcharts)
