Crystal Ball Nebula (NGC 1514) in Taurus

Transcription

1 Bristol Astronomical Society Information Leaflet January 2016 Crystal Ball Nebula (NGC 1514) in Taurus Combined Image of the Crab Nebula (M1) in Taurus BLUE: X-rays (Chandra); Orion Constellation, RED & YELLOW: HST Visible Image, (HST); ESA PURPLE: IR (Spitzer) Source: Joseph DePasquale, Chandra X-Ray Observatory 1

2 Observing Calendar January 2016 Observing Calendar January

3 The Sun The Moon Sun s Position at Midday 15 th January 2016 Jan. 18 th : Two Great Lunar Craters - Tycho & Copernicus Solar Events for January 18 th is a great night to observe two of the greatest craters on the Moon, Tycho and Copernicus, as the terminator is nearby. Tycho is towards the bottom of Moon in a densely cratered area called the Southern Lunar Highlands. It is a relatively young crater which is about 108 million years old. It is interesting in that it is thought to have been formed by the impact of one of the remnants of an asteroid that gave rise to the asteroid Baptistina. 5

4 Another asteroid originating from the same breakup may well have caused the Chicxulub crater 65 million years ago. Tycho has a diameter of 85 km and is nearly 5 km deep. At full Moon the rays of material that were ejected when it was formed can be see arcing across the surface. Copernicus is about 800 million years old and lies in the eastern Oceanus Procellarum beyond the end of the Apennine Mountains. It is 93 km wide and nearly 4 km deep and is a classic "terraced" crater. Both can be seen with binoculars. The Moon Lunar Highlights During January The Planets January 1 st at 00:00 January 15 th at 00:00 January 3rd and 4th: Mars and the Moon Around 6 am on the mornings of the 3rd and 4th, Mars will be seen close to a waning crescent Moon - to its right on the 3rd and to its left on the 4th. January 19th - A gibbous Moon crosses the Hyades Cluster After sunset on the 19th of January, a waxing Gibbous Moon will be seen just to the right of the Hyades Cluster in Taurus. During the following evening and night, it will be seen to move across the cluster and by 4 am next morning will lie very close to Aldebaran. January 30 th at 00:00 January 27th - A gibbous Moon passes below Jupiter After sunset on the 27th of January, a waning gibbous Moon will be seen to pass below Jupiter as it lies in the southern part of Leo. At their closest, about midnight, they will lie 4 moon diameters apart

5 The Planets Mercury On New Years Day Mercury shines at magnitude -0.4 about 7 degrees above the south-western horizon 30 minutes after sunset. Binoculars will be probably needed to spot it but do not use them until after the Sun has set. Over the next week it falls back towards the horizon with a much reducing magnitude (down to +1.8) and will be increasingly difficult to spot. It passes through inferior conjunction with the Sun on January 14th and might be just possible to spot in the east before dawn at the end of the month shining at magnitude 0.0. At its next inferior conjunction on May 9th it will be seen to transit across the face of the Sun, its first transit for 10 years. Venus Venus rises around 3 hours before the Sun as January begins but only 2 hours at month's end. Starting January at ~ 1 degree from Beta Scorpii, it moves quickly into Sagittarius, passing close to the Trifid Nebulae (M20) on the 24th and reaches the handle of the 'teapot' by February. Its angular size reduces from 14.3 to 12.4 arc seconds during the month but, as it does so, the percentage of the disk which is illuminated increases from 77 to 85% and the brightness hardly changes, staying at magnitude -4 for much of the month and falling by just 0.1 of a magnitude by month's end. The Planets Jupiter This is a really good month to observe Jupiter. It now lies in Leo and so is still reasonably high in the ecliptic and hence, when due south, at an elevation of ~45 degrees. It is looking somewhat different than in the last few years as the north equatorial belt has become quite broad. The Great Red Spot is currently a pale shade of pink but can be easily seen as a large feature (though possibly shrinking in size) in the South Equatorial Belt. Jupiter shining at magnitude -2.2, rises at around 20:30 UT at the beginning of the month lying low in south-eastern Leo. It begins its retrograde motion, moving westwards across the heavens, on January 8th. By the end of the month it rises at around 19:30 UT with a slight increase in magnitude to It will then be due south and so highest in the sky at an elevation of 45 degrees around 01:30 UT. As the Earth moves towards Jupiter, the size of Jupiter's disk increases slightly from 39 to 42.4 arc seconds so one should be easily able to see up to four of the Galilean moons. Mars Mars starts the month in Virgo, 6 degrees from Spica, but moves eastwards into Libra mid-month. Its brightness increases slightly from magnitude +1.3 to +0.8 during the month as the angular size of its disk increases from 5.6 to 6.8 arc seconds. Mars rises about 01:30 on New Years Day and around 30 mins. earlier by month's end when it will lie just 1.3 degrees north of the double star Alpha Librae. Some details on the surface such as Syrtis Major and the polar caps may be visible with a telescope, but will be far better seen at opposition in May when it will appear around 3 times wider. 8 9

6 The Planets & Comet Catalina The Sky This Month Saturn Saturn is now a morning object, rising at 06:15 UT as the month begins but by about 04:30 UT at its end. It lies in the southern part of Ophiuchus some 7 degrees up and to the left of Antares and close to the stars that mark the head of Scorpius. Its diameter increases from 15.3 to 15.8 arc seconds during the month with its ring system spanning some 35 arc seconds. It will be shining at magnitude +0.5 and be high enough in the southeast before dawn to make out the beautiful ring system which has now opened out to ~25 degrees. Uranus (15 th January) All around the world, Uranus is an early evening object, now receding into evening twilight. From Bristol, it will become visible at around 17:53 (GMT) as the dusk sky fades, 44 above your southern horizon. It will then sink towards the horizon, setting 7 hours and 47 minutes after the Sun at 00:11. Neptune (15 th January) Neptune will soon pass behind the Sun at solar conjunction. From Bristol, it is not observable it will reach its highest point in the sky during daytime and is no higher than 19 above the horizon at dusk. Comet Catalina Comet Catalina moves into our northern skies this month perhaps just reaching unaided eye visibility as it does so but the use of binoculars or a small telescope will be better. It starts the month just above the bright stars Arcturus in Bootes and tracks northwards until, at mid-month, it passes by the handle of the Plough in Ursa Major. The chart on page 11 shows its path during January Planetary info source: & 10 The Path of Comet Catalina In January The map below shows the constellations seen in the south around midnight. The constellation of Orion is easily located and moving up and to the right - following the line of the three stars of Orion's belt - brings one to Taurus; the head of the bull being outlined by the V-shaped cluster called the Hyades with its eye delineated by the orange red star Aldebaran. Further up to the right lies the Pleaides Cluster. Towards the zenith from Taurus lies the constellation Auriga, whose brightest star Capella will be nearly overhead. To the upper left of Orion lie the heavenly twins, or Gemini, their heads indicated by the two bright stars Castor and Pollux. Down to the lower left of Orion lies the brightest star in the northern sky, Sirius, in the constellation Canis Major. Finally, up and to the left of Sirius is Procyon in Canis Minor. 11 Sky This Month :

7 The Sky Looking Overhead at 22:00 mid-january 2016 The Sky Looking North at 22:00 mid-january

8 Observing Notes NGC 2403 is well placed - 15 th January Planetary Positions 15 January NGC 2403, a spiral galaxy in Camelopardalis, will be well placed for observation (Dec '). It will reach its highest point in the sky at around midnight local time. From Bristol it will be very well placed it will be close enough to the north celestial pole that it will be high above the horizon all night. At magnitude 8.4, NGC2403 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or small telescope. M44 is well placed - 31 st January The Beehive open star cluster (M44, NGC 2632, also known as Praesepe) will be well placed for observation (Dec ').. It will reach its highest point in the sky at around midnight local time. From Bristol it will be visible in the evening sky, becoming visible at around 18:16 (GMT) as the dusk sky fades, 16 above your eastern horizon. It will then reach its highest point in the sky at 00:11, 58 above your southern horizon. It will continue to be observable until around 06:07, when it sinks to 16 above your western horizon. At magnitude 3.1, M44 is tricky to make out with the naked eye except from a dark site, but is visible through a pair of binoculars or small telescope. Capella Pathways from Orion 1 January 23:00 15 January 22:00 31 January 21:

9 The Sky Looking East at 22:00 mid-january 2016 The Sky Looking West at 22:00 mid-january

10 The Sky Looking South at 22:00 mid-january 2016 ISS - Visible Passes from Bristol The tables below show the visible passes of the International Space Station (ISS) from Bristol during the month

11 The Sky This Month - Taurus Taurus is known for its bright stars Aldebaran, El Nath and Alcyone (within M45), as well as for the variable star T Tauri. The constellation is probably best known for the Pleiades (M45) and the Hyades, which are the two nearest open star clusters to Earth. Taurus also has a number of famous DSOs, among them the supernova remnant M1 (the Crab Nebula), Hind s Variable Nebula (NGC 1555), the colliding galaxies NGC 1410 and NGC 1409, the Crystal Ball Nebula (NGC 1514), and the Merope Nebula (NGC 1435). [See BASIL Nov-15 for M45 info]. The Sky This Month - Taurus NGC 1514 Messier 77 (NGC 1068) Aldebaran α Tauri (Alpha Tauri) [# 33] Aldebaran is an orange giant with a visual magnitude varying between It is the brightest star in the constellation Taurus, the 13 th brightest star in the sky (about 425 times more luminous than the sun) and has the stellar classification K5III. The star lies approximately 65 LY from Earth and is classified as a slow irregular variable, type LB. The star is cooler than the Sun, with a surface temperature ~ 4,000 K, compared to the Sun s 5,800 K. It is a very slow rotator, rotating every 643 days. Crystal Ball Nebula (NGC 1514) Aldebaran has evolved off the main sequence stage of its Planetary Nebula, Mag. 9.4 life cycle and exhausted the supply of H fuel in its core. It T Tauri is now fusing H in a shell around the He core. As a result, T Tauri is a variable star (mag & 600 LY distant) that serves as a prototype for a class of stars known as the T Tauri variables. It can be found near the star has brightened and expanded to a radius 44.2 solar. If Aldebaran were to replace the Sun in the centre Epsilon Tauri (SAO 93954), a member of the Hyades cluster, but is located of the solar system, the star s surface would extend halfway to the orbit of Mercury and would extend across 20 degrees in our sky. some 420 LY behind it. T Tauri variables are pre-main sequence stars with less than 2 solar masses and belong to the spectral classes F, G, K and M. Elnath β Tauri (Beta Tauri) [# 45] They M31 are much more luminous than main sequence stars that have the Elnath (sometimes spelt Alnath) is the second brightest star in Taurus. It has same mass because T Tauri stars have larger radii. They are usually located a visual magnitude of 1.68 and is approximately 131 LY distant. Elnath is a near molecular clouds and exhibit optical variability as well as strong chromospheric giant star with the stellar classification B7III. It is 700 times more luminous lines. T Tauri itself is a star system consisting of at least 3 stars. than the Sun. Elnath lies on the border with the constellation Auriga and has Only one of them can be seen at optical wavelengths, while the other 2 are the Bayer designation Gamma Aurigae. visible in Rigel the infrared. One of the stars is a source of radio waves. 20 [# - Meade LX200 Object Catalogue No.] 21

12 The Sky This Month - Taurus The Sky This Month - Taurus The Hyades Cluster (Caldwell 41, Melotte 25, Collinder 50) (SAO 93897) (SAO 93868) The Hyades is an open cluster that contains hundreds of stars that share the same motion through space, origin, age, and chemical content. It is the nearest open star cluster to the Sun, and consequently the most studied one, too. Its estimated age ~ 625 million years. The brightest stars in the Hyades cluster and Aldebaran, the brightest star in the Taurus constellation, form a V shape or bull s head asterism (see above). Aldebaran is not a member of the cluster, but lies along the same line of sight. The 4 brightest stars in the cluster Gamma, Delta, Epsilon and Theta Tauri are red giants and they all lie within a few LY of each other. The Hyades cluster has an apparent magnitude of 0.5 and is about 153 LY distant. The core of the cluster, densely populated with stars, has a diameter of 17.6 LY. 22 [# - Meade LX200 Object Catalogue No.] The Crab Nebula (M1) is a supernova remnant in Taurus. It is also a pulsar wind nebula, or plerion, which is a nebula that is powered by the pulsar wind of a pulsar, usually found within shells of supernova remnants. A pulsar, or pulsating star, is an extremely magnetized rotating neutron star that emits a beam of electromagnetic radiation. The nebula is believed to be the remnant of a supernova documented by Chinese, Japanese and Arab astronomers in M1 was the first DSO that was linked to a historical supernova. M1 has an apparent magnitude of 8.4 and is approximately 6,500 LY distant. It is about 11 LY in diameter and expanding at the rate of 1,500 km per second. The neutron star at the centre of the nebula is known as the Crab Pulsar and is a young neutron star, a remnant of the supernova SN 1054, first identified in It emits pulses of radiation ranging from gamma rays to radio waves that rotate 30.2 times each second. 23

13 The Sky This Month - Auriga The Sky This Month - Auriga Auriga means the charioteer in Latin - the constellation got this name because its major stars form a shape similar to that of the pointed helmet of a charioteer. The brightest star in the constellation is Capella, Alpha Aurigae. Auriga contains three Messier objects M36, M37, and M38. Capella α Aurigae (Alpha Aurigae) [# 42] M36 Capella IC 405 Capella is the brightest star in Auriga and the sixth brightest star in the sky. It is only 42.2 LY distant and is a known source of X-rays. Capella consists of a pair of large, bright G-type giants in close orbit and a pair of small, cool red dwarfs, located about 10,000 AU from the first pair. The Capella system belongs to the Hyades moving group, a large group of stars that share a similar trajectory with the Hyades cluster. See p14-15 for easy location on sky map. M37 Menkalinan β Aurigae (Beta Aurigae) [# 57] Menkalinan is a triple star system, 85 LY distant. The brightest two components are white A-type subgiant stars and the third star is a red dwarf. The two brighter stars in the system constitute an eclipsing spectroscopic binary with a magnitude varying between 1.85 and AE Aurigae & The Flaming Star Nebula AE Aurigae is a runaway star (moving through space at extremely high velocity compared to neighbouring stars), ~ 1,460 LY distant. AE Aurigae lights the Flaming Star Nebula (IC 405), an emission/reflection nebula with a magnitude of 6.0. The Flaming Star Nebula is located near Iota Aurigae [# 35]. Messier 36 (M36, NGC 1960) M36 is a bright open cluster, contains > 60 stars and has an apparent mag. of 6.3. The brightest members of the cluster are B2 type stars with an apparent mag. of 9. M36 is ~ 4,100 LY distant and about 14 LY in diameter. It resembles M45 (the Pleiades) in Taurus, but is too distant to appear as conspicuous in the night sky. The estimated age of M36 is 25 million years. 24 [# - Meade LX200 Object Catalogue No.] M38 Messier 37 (M37, NGC 2099) M37 is a bright open star cluster in Auriga. The cluster is ~ 4,000 LY distant and contains ~ 500 stars, of which ~ 150 are > mag M37 contains M31 Melotte 31 or the Minnow Asterism about a dozen red giants and its estimated age is 300 million years. The cluster has an apparent magnitude of 5.6 and is 24 LY in diameter. Messier 38 (M38, NGC 1912) M36 is an open cluster, ~ 4,200 LY distant. The brightest stars in M38 form an oblique cross, or the letter Pi. The brightest member is a G0 class yellow giant with an apparent magnitude of 7.9. The cluster is about 25 LY (20 ) in diameter. Its estimated age is 220 million years. 25

14 Classification of Stellar Spectra BASIL often refers to the spectral classification of featured stars and this article provides a summary of the classification system for stellar spectra. The Harvard scheme is based on lines which are mainly sensitive to stellar surface temperatures rather than actual compositional differences, gravity, or luminosity. Important lines are the H Balmer lines, lines of neutral and singly ionized He, Fe lines, the H and K doublet of ionized Ca at and nm, the G band due to the CH molecule, the nm neutral Ca line, several metal lines around 431 nm, and the lines of Titanium Oxide. Classification of Stellar Spectra Luminosity Classes The Harvard scheme specifies only surface temp. and spectral features. A more precise classification includes the luminosity of the star. The standard scheme is called the Yerkes or MMK classification. It measures the shape and nature of certain spectral lines to measure surface gravities of stars and has 6 luminosity classes. Thus the Sun would be more fully specified as a G2V type star, using this scheme. Additional categorization nomenclature Lowercase letters added to the end of a spectral type indicate peculiarities. Ia Ib II III IV V Most luminous supergiants Less luminous supergiants Luminous giants Normal giants Subgiants Main sequence stars (dwarfs) Standard Stellar Types (O, B, A, F, G, K, and M) Ordered from highest temperature to lowest, the 7 main stellar types are O, B, A, F, G, K, & M. O, B, and A type stars are often referred to as early spectral types, while cool stars (G, K, and M) are known as late type stars. The nomenclature is rooted in long-obsolete ideas about stellar evolution, but the terminology remains. Subtypes Within each of these seven broad categories, there are assigned subclasses numbered 0 to 9. A star midway through the range between F0 and G0 would be an F5 type star. The Sun is a G2 type star. 26 Symbols are added for elements showing abnormally strong lines - e.g. Epsilon Ursae Majoris is type A0p IV:(CrEu), indicating strong chromium and europium lines. The colon means uncertainty in the IV luminosity class. Asymptotic Giant Branch Stars (R, N, and S) - double-shell burning phase star; name based on how stellar evolution proceeds when charted on a Hertzprung-Russell diagram. Wolf-Rayet Stars (WR) - similar to O type stars, but have broad emission lines of H and ionized He, C, N, and O with very few absorption lines T Tauri Stars (T) - very young stars, typically in interstellar clouds (see p21) 27 UCL Astrophysics Group

15 Society News Programme of Events (At Bristol Photographic Society, Station Road, Montpelier, Bristol. BS6 5EE ) 15 Jan Was Einstein 100% Right? (Prof Malcolm MacCallum) 22 jan Members Talk Night 29 Jan Roseland Observatory (Brian sheen) BAS Programme for 2016 Our meeting programme for 2016 starts on 15th January, with weekly meetings until 17th June. The AGM is scheduled for 19th February. Full details can be found on the BAS website. Dr Mark Kidger (ESA) Dr Robert Massey (RAS) Prof Mark Birkinshaw BAS Saturday Observing & Star Parties Saturday Observing: December s weather was poor, so unfortunately none of the scheduled observing sessions could go ahead. Two sessions are scheduled for January - see page 3 for details. Star Parties: a successful star party was held at Tyntesfield on 8th December, with 35 visitors attending and 8 telescopes in operation. See the BAS website and group s for details of star parties in January. Bristol Astronomical Society (Registered Charity No ) 28