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AAS Journal 32 April 2007

Southern Sentinel Crossword April 2007 Edition

The solutions to the March crossword are on page 31.

Across 3 Space Shuttle research laboratory (8) 5 A Meade 90mm Maksutov Cassegrian

is called a what (3) 6 A method of mounting a telescope that

follows the Earth's axis of rotation (10) 8 Proper name for NGC4755 in Crux

(5,3) 10 The aligning of an equatorial mount is

called a what alignment (5) 12 The constellation 'The Lion' (3) 13 A term used to describe anything with

mass (6) 14 The space station of the former Soviet

Union (3)

Down 1 Keeper of the Brisbane observatory at

Parramatta in the early 1800's (5,6) 2 How many Apollo Landings were

there? (3) 4 Large planetary nebula in Aquarius

(5,6) 7 A loose collection of hundreds of stars

that are gravitationally bound to each other (4,7)

9 State in the US renown for its clear still night skies (7)

10 The distance at which a star would have a parallax of one arcsecond (6)

11 Seventh letter of the Greek alphabet (3)

1 2

3 4

5

6 7

8

9

10

11

12

13

14

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SOCIETY JOURNAL

April 2007

The Society meeting this month is a video evening with a documentary that explores the perplexing problem of missing mass: what has the Universe done with all the matter that all the indicators say is there?

Where Has It All Gone?


President: Steve Calveley 412-9770

Vice President: John White 486-2398

Treasurer: Desmond Heath 575-7750

Secretary: Tim Natusch 838-8938

Curator of Instruments: Dave Moorhouse 0274 819089

Librarian: Helen McRae 021 494418

Editor: Phil Foster 378-9312

Councillor: Mark Cannell 520-1123

Councillor: Martin Thomas 482-2917

Councillor: Nick Moore 537-1500

THE SOCIETY COUNCIL

JOURNAL OF THE AUCKLAND ASTRONOMICAL SOCIETY

The aim of this publication is to promote and foster the science of astronomy, and to encourage the association of astronomical observers and other persons interested in astronomy.

11 issues per year.

Auckland Astronomical Society, Inc., P O Box 24-187 Royal Oak, Auckland 1345, New Zealand

Email : [email protected] Internet : www.astronomy.org.nz

Contact Us :

April 2007 31 AAS Journal

TRADING POST

If you would like to advertise any astronomical equipment in the Journal, please email [email protected].

SOLUTION TO THE MARCH CROSSWORD Across: 1 Phobos, 5 Catadioptric, 8 Airy Disc, 10 Troposphere, 11 Betelgeuse, 12 Selenography.

Down: 1 Polar, 2 Sea of Rains, 3 Leo, 4 Keck, 5 Celestron, 6 Trifid Nebula, 7 Multiply, 9 Cell.

• Newtonian Telescopes• Eyepieces & Accessories• Performance and Value

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Southern Sentinel Observing List JOG observers astronomical objects

to observe in April

Medium Objects requiring more aperture. A 6 - 8 Inch telescope recommended

Hard Objects difficult to see or find. A 10 Inch + telescope recommended

Easy Objects easy to see or find in small telescopes or binoculars

PN - Planetary Nebula G - Galaxy OC - Open Cluster GC - Globular Cluster BN - Bright Nebula DN - Dark Nebula SN - Supernova Remnant Gal G - Galaxy Group

Copeland's Gal G Leo NGC 3158 Gal G Leo Minor NGC 3227 G Leo Fleming 1 PN Centaurus NGC 3190 Gal G Leo NGC 3193 G Leo NGC 3195 PN Chamaeleon NGC 3245 G Leo Minor NGC 3489 G Leo NGC 3511 G Crater NGC 3585 G Hydra

NGC 3606 G Hydra NGC 3607 Gal G Leo NGC 3783 G Centaurus NGC 3887 G Crater NGC 4038 G Corvus NGC 4039 G Corvus NGC 4105 G Hydra NGC 4112 G Centaurus NGC 4361 PN Corvus NGC 4782 G Corvus

NGC 3254 G Leo Minor NGC 3309 Gal G Hydra NGC 3311 G Hydra NGC 3344 G Leo Minor NGC 3347 G Antlia NGC 3395 G Leo Minor NGC 3430 G Leo Minor NGC 3432 G Leo Minor NGC 3581 BN Carina

NGC 3666 G Leo NGC 3672 G Crater NGC 3705 G Leo NGC 3717 G Hydra NGC 3810 G Leo NGC 3822 Gal G Virgo NGC 3966 G Ursa Major NGC 3995 G Ursa Major

M 65 G Leo M 66 G Leo M 68 GC Hydra M 95 G Leo M 96 G Leo M 104 G Virgo M 105 G Leo IC 2602 OC Carina NGC 3228 OC Vela

NGC 3372 BN Carina NGC 3521 G Leo NGC 3532 OC Carina NGC 3766 OC Centaurus eta Carinae Star Carina NGC 3918 PN Centaurus NGC 3621 G Hydra NGC 3628 G Leo


MONDAY 9th APRIL 2007 8.00 PM AT THE STARDOME OBSERVATORY

MONTHLY MEETING

Friends and visitors are welcome. The Library will be open from 7:30pm and after the meeting a light supper will be provided.

Most of our Universe is Missing BBC Horizon Documentary (2006)

The truth is, we can only account for a tiny percentage of our universe – around 4%. So what is the remaining 96% made of? The current favoured thinking relies on the exis-tence of dark matter: a substance you can't see, made of particles that so far exist only on paper, shaped and formed by a theoretical force that has never been measured. Yet bil-lions of dollars is being spent in trying to find it. And the stakes are high; whoever finds the elusive dark stuff is virtually guaranteed a Nobel Prize, and could well have paved the way for the biggest prize of all – the elusive 'theory of everything'. But not everyone agrees. Horizon meets the warring factions, from Princeton Professors to a 'punk cos-mologist', and gets the story first-hand

Video Evening

We are delighted to warmly welcome the following new

members to the Society.

We would like to extend a welcome to these people who have recently joined the society. Hope to see you at our regular meetings.

Michael Rovers, Dale Russell, Roger Qiu, Peter Hosking, Andiea Tihore, Peter Koloszar, Abhishek Chawla.


Calendar of Society Events

April 2 Monday 8:00 PM Beginner's Guide to the Sky at Night Martin Thomas 5 Thursday 7:30 PM A.A.S. Council Meeting 6 Friday Good Friday 8 Sunday Easter Sunday 9 Monday Easter Monday 8:00 PM Society Monthly Meeting Video Evening: Most of our Universe is Missing 13 Friday 7:30 PM Young Astronomers Group Margaret Arthur 20 Friday 7:30 PM Night Eyes It’s Cloudy Every Night David Britten 23 Monday 8:00 PM AGM 30 Monday 8:00 PM Introduction to Astronomy Cosmic Horizons Roger Feasey

May 4 Friday 7:30 PM Young Astronomers Group Margaret Arthur 7 Monday 8:00 PM Beginner's Guide to the Sky at Night Martin Thomas 10 Thursday 7:30 PM A.A.S. Council Meeting 14 Monday 8:00 PM Society Monthly Meeting TBA 18 Friday 7:30 PM Night Eyes David Britten 28 Monday 8:00 PM Introduction to Astronomy TBA


References http://vizier.cfa.harvard.edu/viz-bin/VizieR-3 Washington Visual Double Star Cata-logue 1996.0 http://www.seds.org/ Students For The Exploration and Development of Space. http://aladin.u-strasbg.fr/java/ Aladin Sky Atlas (image HD 87743) Star Names, Their Lore And Meaning Richard H. Allen

Double/Multiple Stars

Deep Sky

NAME RA (2000)

DEC (2000)

YR SEP. PA° MAGS

εAB 08h 46.8m +06° 25’ 1995 0.0” - 3.8;5.3 ε AB-C 1994 3.0” 292 7.8 ε AB-D 1978 18.7” 199 12.5 ε AB-E 1984 *338.0” 001 10.1 ε AB-F 1984 412.1” *265 10.2 HD87743 10h 06.6m -19° 18’ 1959 9.5” 146 8.8;10.0 β320 12h 37.7m -27° 08’ 1968 1.3” 179 5.4;11.3 R Hydrae 13h 29.7m -23° 17’ 1961 21.2” 324 Var;12.0

NAME RA (2000)

DEC (2000)

vMAG SB* SIZE

NGC 2548 (M48) 08h 13.8m -05° 48’ 5.8 54.0’ NGC 2610 08h 33.4m -16° 09’ 12.7 50”x47” NGC 2835 09h 17.9m -22° 21’ 10.6 14.1 6.6’x4.4’ NGC 3109 10h 03.1m -26° 09’ 9.9 14.3 19.1’x3.7’ NGC 3124 10h 06.7m -19° 13’ 12.0 14.1 3.0’x2.5’ NGC 3145 10h 10.2m -12° 26’ 11.7 13.3 3.1’x1.6’ NGC 3242 10h 24.8m -18° 38’ 7.7 45”x36” NGC 4590 (M68) 12h 39.5m -26° 45’ 8.2 12.0’ NGC 5236 (M83) 13h 37.0m -29° 52’ 7.8 13.0 15.4’x13.1’ NGC 5694 14h 39.6m -26° 32’ 10.2 3.6’

A more literal translation (http://www.ianridpath.com/startales/felis.htm) from Ger-man may be

“I love cats very much. I will have this picture engraved on the star map. The starry sky has made me tired enough all my life to allow me to have a little fun now.”

Clear skies and good hunting.


It was first found by Sir William Herschel on Feb. 7th, 1785. Employing his newly con-structed 18.7” f/12 telescope, he described it as

“a beautiful, very brilliant globe of light; a little hazy on the edges, but the haziness goes off very suddenly, so as not to exceed the 20th part of the di-ameter, which I suppose to be from 30 to 40 arcseconds. It is round, or per-haps a very little elliptical, and all over of an uniform brightness: I suppose the intensity of its light to be equal to that of a star of the 9th magnitude.”

Small telescopes will show a pale greeny-blue football shaped glow, located about 1.8° south of mu Hydrae. Larger apertures give a stunning view, with an intense green-blue colour rarely seen elsewhere and internal structure within the nebula when high power is employed. The edges are distinctly fuzzy and not well defined. The 11.4 magnitude blue central dwarf star can also be seen.

Another planetary nebula worth looking for, though needing darker skies is NGC 2610. Visually, it appears as a faint, slightly elongated pale grey disk ap-proximately 40" in diameter surrounded by a delightful field. A 13th magnitude star is superimposed on the northeastern edge and an orange mag-nitude 6.6 star (SAO 154395) hovers 3.5' away further to the northeast. A 15cm telescope should show this nebula and a 20cm at high power may show mottling.

Finally, for those lovers of the feline variety, the 18th century French astronomer Joseph de Lalande included a now lost constellation in his third edition of Astronomie. Named Felis, it nestled between the stars mu, lambda and upsilon in Hydra and alpha and theta in Antlia. Star Names, Their Lore And Meaning (Richard H. Allen) credits Lalande with the following quotation,

"I am very fond of cats. I will let this figure scratch on the chart. The starry sky has worried me quite enough in my life, so that now I can have my joke with it."

Lost constellation, Felis


VERY IMPORTANT The 2007 AGM

Monday, April 23rd, 2007, 8.00pm at the Stardome Observatory

The 81st Annual General Meeting of the Auckland Astronomical Society, Incorporated will be held at the Stardome Observatory, One Tree Hill Domain on Monday, April 23rd, 2007 at 8.00pm. Nomination are called for the positions of President, Vice President, Treasurer, Secre-tary, Curator of Instruments, Librarian, Editor and three members of Council. The Presi-dent and Treasurer are also ex-officio members of the Auckland Observatory and Plane-tarium Trust Board. Nominations close on April 9th. Nominations for any positions not filled by this date can be made from the floor of the meeting. In addition, the Society elects an Honorary Auditor and Honorary Solicitor and may elect a Patron. Only current financial members of the Society are eligible for election or may vote at the meeting.

Society News

Beaumont Prize Winners The Beaumont writing prize was awarded at the Burbidge Dinner. This prize is given to the best article written for the journal last year, 2006.

Beaumont Prize A Very Egyptian Eclipse, Jude Foster, published in the May 2006 journal.

The story of frustration and rumours while travelling to a remote part of Egypt to see a Solar Eclipse.

Runner up Birds of the Mist, Richard Moss, published in the August 2006 journal.

Richard described the Eagle and Swan nebuli in his regular series on the constellations.

Congratulations to both of you and thank you to all those who wrote articles last year.

Articles written now are eligible this year’s Beaumont prize which comes with a certifi-cate and $300. To be considered an article must be original, 1000 words or more in length and be written by a current, paid-up society member.


Introduction to Astronomy

The ‘Introduction to Astronomy’ is a new event looking at general topics of interest to those with a new interest in astronomy. These meetings cover all aspects of astronomy in a low key informative way.

‘Introduction to Astronomy’ also provides a good opportunity to meet other members and feel free to ask any questions you may have. See you there !!

Coordinator: Steve Calveley (ph: 412-9770)

Cosmic Horizons Roger Feasey

Monday 30th April 2007 8:00pm at the Stardome Observatory

If we lived forever, would we be able to see to the ends of the Universe? Roger Feasey will discuss the expanding universe, and how that expansion effects what we can see of the Universe now, and how that view of the Universe will change in the future. He will also discuss common misconceptions about the expansion of the Universe and how these arise.

Did you know that members of the Auckland Astronomical Society can get 25% off the subscription rate for Sky & Telescope Magazine? That could save you about $30 per year.

Contact The Treasurer for further details


The first supernova discovered was in 1923 when it shone as a 14th magni-tude glow. The next two were seen in 1950 (14.5 mag.) and 1957 (15.0 mag.). The brightest to date was seen in 1968 by J.C. Bennett, a South Afri-can amateur astronomer. It shone at 11th mag., nearly central in the nucleus. The latest burst forth July 3, 1983 and attained a magnitude of 12.5. In 1990, photographic plates showed another supernova had occurred in 1945, reach-ing mag 14.5.

There are four other galaxies worth looking at, though none as impressive as M83. NGC 2835 is a face-on spiral of low surface brightness of 14.0 and a size of 6.6’x4.4’. Two 10th magnitude stars lie to the west and southeast.

NGC 3109 is an irregular elongated galaxy with a low surface brightness of 14.4 and will need a 20cm or greater telescope while NGC 3124 is a face-on barred spiral with a bright nucleus though once again the surface brightness is low at 14.2. The double star HD 87743 lies 4’ to the south. The components are magnitude 8.8 and 10.0 with a separation of 9.5”.

NGC 3145 appears as a hazy glow with an oval nu-cleus visible in a 15cm or larger telescope though magnitude 3.6 lambda Hy-drae 8’ to the northeast overwhelms it somewhat. Keep the star out of the field of view for maximum benefit.

The highlight of this area is NGC 3242, an exceptional planetary nebula with an extremely high surface brightness. With a diameter similar to Jupiter, it is com-monly called the ‘Ghost of Jupiter’ after a description by Admiral Smythe.

NGC 3242, the “Ghost of Jupiter”, planetary nebula as seen by the Hubble Space Telescope.

Double star HD 87743


brightening towards the centre with a strong central condensation. With a distance esti-mate of 33,000 light years (W.E. Harris – Galactic Globular Clusters Database), the di-ameter must be around 106 light years.

NGC 5694 is the other globular, first seen by Sir William Herschel in 1784. It was first recognised and resolved as a globular cluster by C. Lampland and Clyde Tombaugh in 1932.

It is one of the more remote clusters at 113,000 light years with its brightest stars glow-ing dimly at magnitude 16.5 and its actual diameter spanning around 120 light years. To find NGC 5694, look 1.5° southwest of the asterism 54, 55, 56 and 57 Hydrae. This gath-ering of stars was shown on maps of the early 19th century as Noctua or ‘Night Owl’ but unfortunately it has been lost from current maps.

One of the best galaxies in the sky and certainly in Hydra is M83 (NGC 5236). This su-perb face-on spiral or possible barred spiral galaxy was first seen by Nicholas de la Caille in 1752. At 8th magnitude, this large round glow with a very bright nucleus and two spi-ral arms can be seen well in as little as a 15cm telescope. The spiral arms appear as a re-versed letter S and a 3rd spiral arm can be seen with larger scopes.

The remarkable thing about this galaxy is its frequency of supernovae, 6 appearing within 60 years. This record has been broken with NGC 6946 in Cepheus claiming 8.

M83, the “Southern Pinwheel” Galaxy.


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The Sky This Month

CosMos

DATE TIME RISE SET Full Moon 03 Apr. 07 0516 1812 0646 Last Quarter 11 Apr. 07 0605 - 1418 New Moon 17 Apr. 07 2338 0605 1725 First Quarter 24 Apr. 07 1837 1348 2341

DATE RISE SET Mercury 01 Apr. 07 0426 1720 Mercury 29 Apr. 07 0633 1728 Venus 01 Apr. 07 0934 1949 Venus 29 Apr. 07 1028 1949 Mars 01 Apr. 07 0253 1625 Mars 29 Apr. 07 0248 1532 Jupiter 01 Apr. 07 2144 1216 Jupiter 29 Apr. 07 1951 1022 Saturn 01 Apr. 07 1559 0224 Saturn 29 Apr. 07 1408 0033 Uranus 01 Apr. 07 0435 1716 Uranus 29 Apr. 07 0251 1529 Neptune 01 Apr. 07 0233 1607 Neptune 29 Apr. 07 0046 1419

DATE RISE SET 01 Apr. 07 0634 1816 15 Apr. 07 0646 1756 30 Apr. 07 0659 1737

All times NZST (UT +12 hrs) and are for Auckland.

Mercury lies in the early morning eastern sky as April begins, its 0.0 magnitude 6.4” disk rising at 0425 hrs. Slowly closing toward the Sun, Mercury brightens half a magnitude to –0.5 and its disk shrinks a little in size to 5.5” later in the month. Look for Mercury around 90 minutes before sunrise on the 15th, the planet moving from Pisces into Cetus. From now on, Mercury competes with the background dawn twilight. A diminishing slim crescent Moon passes on the nights of the 16th and 17th heading towards a New Moon one day later


M48 (NGC 2548) is an open cluster catalogued by Charles Messier in 1771.

“Cluster of very small stars, without nebulosity; this cluster is at a short distance from the three stars that form the beginning of the Unicorn’s tail.”

However, Messier made an error of 4° in position for this object and it was known for some years as one of Messier's missing objects. There is no doubt which object Messier meant because of his description of it. Messier’s cluster was re-identified in 1934 by Oswald Thomas. Earlier, Johann Bode had seen it around 1782 and Caroline Herschel in 1783.

“At an equal distance from 29 & 30 Monocerotis, making an equilateral triangle with those two stars is a nebulous spot. By the telescope it appears to be a cluster of scattered stars. It is not in Mess. Catalogue.”

Sir William Herschel catalogued it as H V1.22 in 1786. This large cluster spans an area the size of the Full Moon, Burnham describing it as triangular in shape dominated by a

"central chain-like grouping of 10 or so 10th and 11th magnitude stars; sev-eral dozen fainter members increase the total population to about 50 stars down to the 13th magnitude".

Three yellow G to K spectral type stars reside here, the rest being A-type main sequence stars, the brightest of which shines at magnitude 8.8 and has a luminosity 70 times that of our Sun. With a compressed central core of 30’ in diameter and a halo of outliers extend-ing to 54’, it should present itself to the naked eye under dark skies. Binoculars will show the brighter members with telescopes bringing forth many of the fainter stars, the total population around 80.

The distance to M48 given by Mallas, Kramer and Jones is 1500 light years, according M48 an actual diameter of 23 light years. M48’s age is estimated to be around 300 mil-lion years.

Two globular clusters reside amongst the faint background stars Hydra, the best being M68 (NGC 4590). Messier found this ball of over 100,000 suns in 1780,

“Nebula without stars below Corvus & Hydra; it is very faint, very difficult to see with the refractors; near it is a star of sixth magnitude.”

This 6th magnitude star recorded by Messier is in fact β320, a pair of magnitude 5.4 and 11.3 stars separated by 1.3”.

Smyth recorded M68 in 1837,

“A large round nebula on Hydra’s body, under Corvus…Sir William Herschel’s powerful 20-foot reflector resolved it into a rich cluster of small stars, so compressed that most of the components are blended together. It is about 3’ broad, and 4’ long…It is very pale, but so mottled that a patient scrutiny leads to the inference, that it has assumed a spherical figure in obe-dience to attractive forces.”

It is partially resolved in a telescope of 15cm aperture and shows as a very rich group,


“Thereby was wrought the Hydra, many-necked flick-ering its dread tongues. Of its fearful heads some severed lay on the earth, but many more were bud-ding from its necks, while Herakles and Iolaos, dauntless-hearted twain, toiled hard; the one with lightning sickle-sweeps lopped the fierce heads, his fellow seared each neck. With glowing iron; the monster so was slain.”

H ydra is the largest constellation in the sky, extending some 95° in length from the border of Cancer in the north to the more southerly Centaurus and Libra to the east. Many cultures throughout the world have honoured this constellation as

a serpent, a snake or a dragon. It is usually associated with the many-headed monster slain by Hercules, hence its popular name of the Sea Serpent. It must not be confused with Hydrus that lies more southerly between the barren star-fields of Horologium and Tucana.

The brightest star in Hydra is alpha or Alphard, ‘the Solitary One in the Serpent’ and also the ‘Backbone of the Serpent’. Tycho Brahe first named it Cor Hydrae, the ‘Hydra's Heart’. This 2nd magnitude giant, K-type orange star is similar to Antares in Scorpius, the ‘Heart of the Scorpion’.

Epsilon is an interesting multiple star of combined magnitude 3.3, the two easy compo-nents of yellow and blue hues. The primary star is itself a very close double system, first noticed by Schiaparelli in 1888. However, don't expect to see the companion as it is too close to be resolved by amateur mirrors. The blue 7.8 magnitude companion at 3.0” is a dF7 type star measured by Otto Struve in 1825. It has also been found to be a spectro-scopic binary. A 4th star lies 18.7" away, being a K-type dwarf star of magnitude 12.5. There are two wider stars of magnitude 10.1 and 10.2 lying at separations of 338" and 412.1", very likely optical companions only.

An interesting variable star is R Hydrae, an M-type giant similar to Mira in Cetus. This jewel was the 3rd long-period variable star to be identified, credited to Maraldi in 1704. Hevelius probably saw it in 1662 but never recognised it as variable. The red colour of R Hydrae needs to be observed near minimum, the colour falling away noticeably as it ap-proaches maximum. The period is 389.6 days and the brightness ranges from 3rd to 11th magnitude. R Hydrae is also a double star, first measured by G.W. Hough in 1891. The 12th magnitude dwarf companion lies 21" away.

HYDRA The Water Snake

CosMos


Mars lies low in the eastern morning sky on the 1st, rising at 0252 hrs. Shining at magnitude 1.1, its small 4.9” disk lies amongst the stars of Ca-pricornus. Keeping the same magnitude all month, Mars lies near the much fainter Uranus at the months end, having moved into neighbouring Aquarius on the 8th April. The crescent Moon glides past on the 14th, Mars lying not too far from the magnitude 4.8 bright white star sigma Aquarii.

Jupiter rises at 2146 hrs on the 1st, its –2.3 magnitude disk spanning 40.3” amongst the stars of Ophiuchus where it stays all month. By the 30th, Jupiter rises at 1948 hrs where its disk grows to 43.6” and brightens a lit-tle to –2.5. The Galilean moons Io, Europa, Ganymede and Callisto con-tinue their playful dance about Jupiter like moths around a light, continu-ing to enchant even the most casual of observers.

Venus starts out April low in the northwestern evening twilight amongst the background stars of Aries. Shining at magnitude –3.8, its 13.8” disk slowly increases in size but the brightness stays the same as the month progresses. By the 8th, Venus has moved into Taurus and passes above the beautiful ‘Seven Sisters’ or Pleiades on the 13th. A spectacular gathering of Venus and a crescent Moon occurs near the beautiful open cluster stars of the Hyades and Pleiades, low in the northwest on the 20th.


Saturn lies low in the northeast evening sky as April begins, setting at 0222 hrs. Residing amongst the stars of Leo, Saturn’s 19.5” disk shines at magnitude 0.7. A near First Quarter Moon passes on the 25th. Saturn’s bright moon Titan lies to the north on the 1st, moving in a westward direc-tion as it orbits the ringed wonder. Looping Saturn, Titan continues on an eastward march on the 9th to the south before once again completing its orbit around the 17th April. Titan is Saturn’s brightest moon at just over 8th magnitude, being slightly larger than planet Mercury and making it the second largest moon in the solar system behind Jupiter’s Ganymede.

Uranus sits amongst the stars of Aquarius, in the region of the bright or-ange giant star phi Aquarii. At magnitude 5.9, Uranus can be seen with the naked eye from a dark site. The disk of Uranus spans a puny 3.3”, ris-ing at 0334 hrs as April begins. Mercury briefly visits this region on the first two days of April but then rapidly scuttles away. Look for Uranus to the east of a magnitude 6.9 white star on the 7th.

A crescent Moon lies near Uranus on the 15th. A line drawn from orange star phi Aquarii to the Moon at 0400 hrs on the 15th will pinpoint Uranus, the planet lying around one third the line’s length from phi itself. Uranus lies closest to phi on the 21st and 22nd April. Mars joins Uranus on the 30th but like previous visitor Mercury, dashes away quickly.

Neptune lies above and west of Mars on the 1st, shining at magnitude 8.0, its tiny 2.4” disk amongst the stars of Capricornus. Neptune rises at 0232 hrs, a lonely planet in a neighbourhood of faint and unremarkable stars.

References Astronomy Lab 2 Cartes du Ciel – version 2.76


Topic to be advised

Beginner’s Guide to the

Sky at Night

These informal meetings are designed for people with little or no observing experience, and those who wish to learn their way around the night sky. The sessions are interactive, so feel free to ask questions and generally join in. Also, bring along any “optical aids” you may have (binoculars or telescopes) and hopefully Auckland’s weather will be kind to us, and we can go outside and observe what we’ve been discussing!

Monday 2th April 8pm at the Stardome Observatory

Coordinator: Martin Thomas

The Night Eyes junior group meeting for April starts at 7:30pm in the Observatory Sun Room on Friday 20th April. The main topic for the meeting will be: It’s Cloudy Every Night Parents, friends and other Society members are very welcome to attend.

Night Eyes April Meeting

Coordinator: David Britten Friday 20th April 7.30pm

at the Stardome Observatory

For further information please contact: David Britten at [email protected] (ph. 846-3657).


the 8 – 15 magnitude range. The full survey will reach down to magnitude limits of about 22.9 with exposures of the order of 1 – 2 minutes. What will the survey reveal? With the data being part of a Virtual Observatory, a very wide range of research interests will be pursued. Those of interest to Prof. Bessell and his colleagues include:

Trans-Neptunian Objects (TNOs) – determining the mass distribution and orbits of ob-jects out past the orbit of Neptune.

The youngest stars in the solar neighbourhood, recently ejected from molecular clouds.

Blue horizontal branch stars – these are highly evolved relatively bright stars of about +0.5 Mv (absolute magnitude). These are 8-10 times more common than RR Lyrae stars, and can be used as visible dynamical tracers to monitor the dark matter distribution in the halo of the Milky Way.

The oldest stars which formed before spiral galaxies had formed their disks. To survive until today, these would be low mass, very faint stars which would have extremely weak metal lines (remember that in astronomy, metals are any element heavier than hydrogen or helium). Very few of these stars have been found in the halo of the Milky Way so far – there should be many present, just awaiting discovery.

Giant molecular clouds are the location of new star formation. A typical cloud several hundred light years across would contain between 10,000 and 1,000,000 solar masses of material. Only about 10% of the cloud mass would be formed into stars though. Their lives are short on the astronomical time scale only 10 – 30 million years, as excess mate-rial is blown out of the cloud by the massive radiation from massive, young, very hot O type stars. Examples of such star forming regions are the OMC-1 (the Orion Molecular Cloud of which the Orion Nebula M42 is a part) and 30 Doradus in the Large Magellanic Cloud, which has a mass equal to that of that most beautiful of globular clusters, 47 Tu-canae.

OB Associations – loose clusters of bright O and B stars spread over hundreds of light years. The stars are not gravitationally bound.

Low mass stars thrown out of OB Associations.

High red-shift quasars. The SDSS has found 21 with a red-shift > 5.8 and another 3 with red-shift > 6.2. The Stromlo Southern Sky Survey is bound to find many more.

Galaxies out to the red shift desert – out to the epoch where the Universe was so young, galaxies had not yet formed.

Regular operations begin in January 2008. Since previous sky surveys have remained valuable sources of data for research decades after their completion, including research topics that had not even been invented at the time the survey was carried out, we can ex-pect the SkyMapper data to be a valuable resource for many decades. Congratulations to Professor Bessell and his team.

For further information: http://au.arxiv.org/PS_cache/astro-ph/pdf/0702/0702511.pdf Roger Feasey


Solar System

Astrophotography Competition 2006

2nd – Comet 68 – Laurie Williams. This image should be called Te Mata Peak Volcano.

The 2006 astrophotography prizes were awarded at the Burbidge Dinner in March. These prizes are for the best photographs taken by Society members last year (2006) and were in three categories: Solar System, Picturesque and Deep Sky. The first prize in these categories were then put forward to be considered for the Harry Williams Trophy. The pictures are printed below but sadly the black and white reproduction does not do full justice to the images. A special thank you to the judges – John Drummond, Director of RASNZ Astrophot-ography Section and Ian Cooper – and to those who submitted entries to the competition. The photographs are accompanied by notes from John Drummond.

Congratulations Auckland on running another astrophotography contest. The quality of the images is again very high – and choosing winners was a challenging task for Coops and I. For those who didn’t place, take heart that your photos are still very good and wor-thy of pride. Keep it up and you may place better next year… I hope that all contestants learnt and enjoyed as they got out there and imaged. Thank you for asking me to judge and enjoy these excellent photos

General comments


Young Astronomers

Coordinator: Margaret Arthur

Note: Because of Easter the Young Astronomers has been moved from the first Friday of the month. This is just for this month.

Friday 13th April 7.30pm at the Stardome Observatory

That tail is astounding! Good framing to have the comet on the left so the tail can be seen extending far to the right. Photos like this will adorn the pages of comet books for dec-ades to come of what a truly great comet’s tail should look like. The horison is nice and parallel to the bottom of the frame which can be a challenge at night…

1st – McNaught – 22Jan-Comp (and the Cowshed) – Guy Thornley -A ‘wow’ photo of a ‘wow’ comet. Impressive tail structure is evident in an exposure that permitted tail detail to be picked up without causing too much foreground movement. The cowshed sign adds a nice human touch. Not sure what happened with the stars on the left and right. Nice timing to get the bright meteor in the tail too!


The camera has 32 off 4k x 2k CCDs providing an effective 16,384x16,384 pixel array. With a 15 micron pixel size, with each pixel covers 0.5 seconds of arc. The CCD array is cryogenically cooled with liquid nitrogen as with most professional cameras, has a very low noise level and fast readout (15 seconds).

The design of the filters is critical to the quality of the information yielded by the survey. They are very non-standard, made of glass, with dimensions of 309x309 mm (that is not a typo – to the imperially minded 12 inches square is near enough) and are 15 mm thick. The wavelength range covers from the near ultraviolet through the visual to the near in-frared and is optimised for stellar astrophysics to deduce parameters such as effective temperature, surface gravity and metallicity. Most of the filters are similar to their SDSS counterparts, but SkyMapper will have an extra relatively narrow band filter in the blue. The filters are being made in Russia and delivery is overdue. With first light due in Octo-ber this year, the project team is more than a little anxious.

What will SkyMapper do? First it will survey the whole of the southern sky from pole to celestial equator. It will carry out photometry of stars and galaxies to 3% accuracy. It will determine stellar positions to better than 0.05 arc seconds over three years. It will ob-serve all fields at intervals of 4 hours, 1 day, 1 week, 1 month and 1 year. It will take five years to complete the survey.

The first priority will be a 5 second survey – 5 second exposures of the whole of the southern sky. This will allow the system to be calibrated to a range of standard stars in

SkyMapper filter spectral response (light) compared with their SDSS counter-parts (dark).


The SkyMapper optical configuration.

Seeing statistics at Siding Spring


2nd – Sagittarius Large – Steve Calveley - a nicely composed image within the diagonal of the frame. Not overly stretched which makes the photo have a more natural-on-the-eye look. Nicely focused.

1st – Scorpion and Palette – Kenric Ma- An aesthetically appealing image. The subtle range of gaseous colours in this wide field image are striking. The Sagittarius star cloud is not overexposed as can easily happen in this region of sky. I particularly enjoy the red

Picturesque


Deep Sky

2nd – NGC253 – Dave Moorhouse - Nicely composed within the frame’s diagonal. Very impressive galactic detail is provided. Good outer extension without burning the galaxy’s

Honourable Mention – 47 Tucana – Guy Thornley – Even though 47 Tucana looks very impressive through a telescope (not as good as Omega Centauri aye Olga!) it is a hard object to image due to the centre being burnt out after a few tens of seconds. You have captured this lovely globular in an admirable way. The focus may be a fraction soft but it actually seems to act like a soft filter in an aesthetically pleasing way.

hydrogen regions and would use this image to locate areas for further investigation with a longer focal length later. I always love seeing the Kiwi in the sky…Perhaps a slight rotation of the camera would nestle it better diagonally, but still a very pleasing photo.


be determining the characteris-tics of millions of objects per image, not dozens or hundreds.

With so many projects planned but held up due to lack of funds, SkyMapper has been funded from the insurance pay-out for the 50 inch Great Mel-bourne Telescope, destroyed in the bush fires at Mt Stromlo just west of Canberra in 2003. Without the fire and insurance payout, the project would more than likely, still be waiting in a queue like so many others.

The telescope is a modified Cassegrain, set up for wide field operation between 0.34 and 1.0 micron wavelengths. The 1.35 m diameter primary (made in Russia) is equipped with an 0.71 m diameter secon-dary (made in France), an 0.56 m aspheric corrector plate and doublet spherical corrector plates resulting in a very wide field of view and an effective focal ratio of f/4.78, very fast for a Cassegrain system. All corrector plates are made of fused silica to allow for maximum transmission of ultravio-let light. The system is being designed by Electro Optic Systems (an Australian com-pany) and is being constructed in Tuscon, Arizona.

It has an off-axis auto-guider, a filter changer and of course a huge CCD camera. The camera is optimised for the moderate seeing at Siding Springs which has useable observ-ing time for about 2,110 hours per year (64% theoretical availability) with nights of photometric quality for 1,135 hours per year (about 35% availability). Seeing is ex-pressed in seconds of arc – the size of a typical stellar image blurred by atmospheric tur-bulence. It is important in assessing a telescope and CCD camera combination, that the physical pixel size and telescope focal length ensure that a typical stellar image is spread over multiple pixels. Siding Springs has a typical seeing of 1.25 – 1.75 seconds of arc on photometric nights, which is better than Auckland’s 2.5 – 3 second seeing, but signifi-cantly worse than the seeing at high altitude observatories in the Andes or Hawaii, where 0.5 – 1.0 seconds is common.

The SkyMapper dome


Burbidge Dinner Lecture 2007

A stronomical surveys vary widely in their breadth (area of coverage), depth (magnitude limit) and research objectives. Two well publicised recent surveys are the 2dF (2 degree field) survey of the 3D structure of galaxy clustering car-

ried out in Australia and the SDSS (Sloan Digital Sky Survey) which is based in the USA and is still ongoing. Prof. Bessell introduced the audience to SkyMapper and the Stromlo Southern Sky Survey which aims to carry out a photometric survey the whole of the southern sky. Why? The reasons are many.

First, full sky surveys are rare. There is no deep digital map of the southern sky. Past sur-veys have been photographic with the consequential shortcomings of photometric preci-sion no better than 0.2 magnitudes and positions to no better than 0.5 arc seconds. The recent 2dF survey which used the 4 m Anglo-Australian Telescope (AAT) at Siding Spring was spectroscopic and covered a few chosen “slices” across the sky. Being pri-marily a survey of deep space objects, it totally avoided the galactic plane, as have most other surveys, which have been orientated to deep sky objectives. Many future sky sur-veys are in the planning stage, but none involve deep digital all-sky observation of the southern sky.

The Stromlo Southern Sky Survey is to be based at Siding Spring Observatory, Coona-barabran, NSW, the home of the AAT. It comprises the relatively small automated 1.35 m aperture SkyMapper telescope (a modified Cassegrain) with a very high tech op-tical configuration which provides a field of view of 5.7° at the CCD camera. The tele-scope will be housed in a three level 11.5 m tall dome which is 6.25 m in diameter. The lowest level houses the electronics and control computers and is thermally isolated from the rest of the structure. Four sets of shutters in the second level allow passive ventilation of the upper telescope level because the floor of the upper telescope level is made of open web grating.

The survey will be photometric rather than spectrographic – it will use a carefully se-lected and well-calibrated set of filters to distinguish astrophysical characteristics, rather than a spectroscope which splits the light of individual objects (or in the case of 2dF, up to 400 objects simultaneously) into a spectrum. So in high density areas, SkyMapper will

SkyMapper and the Stromlo Southern Sky Survey

Prof. Michael Bessell ANU and Mt Stromlo Observatory (Canberra)


1st – Lagoon – Mark Cannell – Boy, what a shot! The subtle colours and huge extent of the nebula are nicely balanced with a non burnt out centre. The bright nebulosity is nicely nestled within the surrounding seething dark lanes. Well focused. The subtle con-trasts of the colours and light and dark areas are exceptional. The author should be very content on a job well done.

Best Overall and Winner of the Harry Williams Trophy

Lagoon – Mark Cannell (above) – The judges were both extremely impressed with this photo. The image draws you into itself as your eye slowly moves across the full extent of nebulosity enjoying a visual feast as you go. This image should find its way into a book – or a calendar at least. Congratulations on an outstanding image!

centre – I love the small orange nucleus. Nice round stars reveal good guiding. I look at this image and invariably think that someone in this galaxy may be looking back! Well done on a good image.


W e all know that birds eat worms. Every day, millions of birds eat millions of worms. It’s going on all around you! But how often have you awakened in the morning, stalked out in the dewy grass, and actually seen a bird having break-

fast? Even though we know it happens all the time, a bird gulping a worm is a rare sight.

Just like a black hole gulping a star …

Every day in the Universe, millions of stars fall into millions of black holes. And that’s bad news for the stars. Black holes exert terrible tides, and stars that come too close are literally ripped apart as they fall into the gullet of the monster. A long burp of X-rays and ultraviolet radiation signals the meal for all to see.

Yet astronomers rarely catch a black hole in the act. “It’s like the problem of the bird and the worm,” says astronomer Christopher Martin of Caltech. “You have to be in the right place at the right time, looking in the right direction and paying attention.”

A great place to look is deep in the cores of galaxies. Most galaxies have massive black holes sitting in their pinwheel centers, with dense swarms of stars all around. An occa-sional meal is inevitable.

A group of astronomers led by Suvi Gezari of Caltech recently surveyed more than 10,000 galactic cores – and they caught one! In a distant, unnamed elliptical galaxy, a star fell into a central black hole and “burped” a blast of ultraviolet radiation.

“We detected the blast using the Galaxy Evolution Explorer (GALEX), an ultraviolet space telescope,” explains Gezari. Her team reported the observation in the December 2006 issue of The Astrophysical Journal Letters. “Other telescopes have seen black holes devouring stars before,” she adds, “but this is the first time we have been able to watch the process from beginning to end.”

The meal began about two years ago. After the initial blast, radiation diminished as the black hole slowly consumed the star. GALEX has monitored the process throughout. Ad-ditional data from the Chandra X-ray Observatory, the Canada-France-Hawaii Telescope and the Keck Telescope in Hawaii helped Gezari’s team chronicle the event in multiple wavelengths

Studying the process in its entirety “helps us understand how black holes feed and grow

Early Bird Gets the Worm or “Black Hole Breakfast”

Dr. Tony Phillips


In this artist’s concept, a giant black hole is caught devouring a star that ventured too close.

in their host galaxies,” notes Martin.

One down, millions to go.

“Now that we know we can observe these events with ultraviolet light,” says Gezari, “we've got a new tool for finding more.”

For more on this and other findings of GALEX, see http://www.galex.caltech.edu. For help explaining black holes to kids, visit The Space Place at http://spaceplace.nasa.gov. This article was provided by the Jet Propulsion Laboratory, California Institute of Tech-nology, under a contract with the National Aeronautics and Space Administration.

This section is provided by NASA’s Space Place. They have a good website at http://www.spaceplace.nasa.gov with fun and interesting resource for children and teachers.

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