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DECEMBER 2014
SOCIETY JOURNAL
December Monthly Meeting
Monday 8 December at 8.00pm
The 2014 Debate: Should Pluto be a Planet?
Host: Oana Jones
The Monthly Meeting normally features a talk by a guest speaker, but Decembers meeting will host the AAS
Great 2014 Debate:
The 2014 Debate: Should Pluto be a Planet?
In 2006 the International Astronomical Union (IAU) stripped Pluto of its planet-hood, demoting it to dwarf
planet status. Ever since, the Pluto is a Planet argument has seen ranging debate on both sides of the fence.
Should it be reinstated to its former glory? What about the other Dwarf Planets in our Solar System?
Harry Williams Trophy Astrophotography Awards
2014 Results and Judges comments
A
few comments on the overall judging: The quality of images entered into this years competition was of a high standard making
it challenging to judge. In the Artistic/Misc and Newcomers categories, I was mainly looking for well composed natural looking
images that stood out from the rest and unique in their own way, as well as being technically sound.
There were a few cases where I came across an image that I was considering as a highly commended image due to good composition, but
were down scored due to the image either not being sharp or over/poorly processed.
In the Solar System and Deep Space categories, it was mostly composition and technical/processing quality of the image that I took into
account.
Artistic / Miscellaneous
Winner and Overall Harry Williams Trophy Winner
Wanaka Tree Mikey Mackinven
A beautifully composed image of the MIlky Way above Wanaka. The flow tree line and Milky Way arch flows in harmony ending with the
silhouette and reflection of the famous Wanaka Tree. A well planned and executed shot, with perhaps a little discomfort having to wade
out in the freezing cold waters of Lake Wanaka to get the shot. Technically very difficult to pull off as this is a 36 image pano stitched
together. There is no stretching or disproportions in the image, and the overall image is natural looking and perfectly balanced between
the light pollution of Wanaka and the night sky.
Highly Commended
Lizards Eye Rob Dickinson
A 360 degree panorama of the night sky presented in a creative way. As the name suggests, the image resembles that of a lizards eye,
with the Milky Way stretching right across the top of the dome of the night sky. Other features of this image include the Large and Small
Magellanic Clouds, air glow and gravity waves in the left of frame. Technically a difficult image to get right with the stitching of many
images that make up the complete sky dome.
Highly Commended
Falling To Earth Andrew Caldwell
There were lots of images which featured the Milky Way in this competition, but this one was a little different. It was a well planned and
executed shot taken during the blue hour just after sunset. It’s a lovely well balanced and natural looking image, which features the ISS
seemingly falling to earth with it’s trajectory along the Milky Way. The soft light and dreamy water in the foreground sits nicely in this well
composed shot.
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society journal, DECEMBER 2014
Solar System
Winner
Moon And Saturn - Paul Stewart
An impressive image of the occultation
of Saturn and by the Moon. Technically
sound and great detail in the image with
good colour balance. The composition of
diagonally splitting the frame in half with
the dark sky against the Moon and Saturn
works really well.
Highly Commended
Plato And Alpine Valley James Tse
A great image of the 95 kilometer wide
crater Plato and surrounding sunlit peaks
of the lunar alps, with the Alpine Valley
cutting through them towards the bottom
right of frame. The detail in this image is
stunning and sharp with no real visible
noise. Technically this image was very well
executed.
Deep Sky
Winner
Antennae Extreme Deep Field Rolf
Wahl Olsen
A spectacular image of a pair of colliding
galaxies known as The Antennae, that
is approimately 45 million light years
away from Earth. Technically this image
is amazing 75 hours of data to produce
this image over 38 nights, and the detail
in the image is something you’d almost
expect from the Space Hubble Telescope.
A worthy winner of the Deep Sky category.
Highly Commended
Tarantula Paul Stewart
A lovely image of the Tarantula Nebula
which is 160,000 light years from Earth.
The image data is well processed and
sharp. and also has great color balance
which helps to exhibit the star clusters, glowing gas, and thick dark dust within the region.
Highly Commended
M83 Southern Pinwheel Galaxy Raymond Collecutt
A stunning image of the Pinwheel Galaxy which is located 21 million light years away from earth. This image was superior in it’s processing
with really nice sharp detail in the image itself.
www.astroNoMy.org.nz
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Newcomers Contest
Winner
Te Arai Tim Dobson
An amazing, well composed image with
the Milky Way sitting perfectly parallel just
above the horizon. The lighter tone of the
wind blown sand leads you into the picture,
and the car parked on the beach silhouetted
by the waves and ocean really gives this
photo a sense of scale. Nice natural looking
processing and colours really gels this image
together.
Highly Commended
Kaikoura Magic David Hardy
When people think of astrophotography,
they usually think of impressive photos of
the Milky Way or Deep Space. This image
captures neither of those, but what it does
capture is the true sense of a New Zealand starry sky as seen from many of the towns throughout the country. It’s a beautifully composed
and natural looking image overlooking the South Island coastal village of Kaikoura. It was shot early morning during astronomical twilight
before sunrise, and the snow covered mountains and low cloud compliments the starry sky above.
Highly Commended
On My Way Terry Urban
Great composition in this image with the Milky Way sitting horizontally across the night sky in contrast with the strikingly vertical aspect of
the cross. To me this image is symbolic of life and death stars have a life cycle, just like life on earth. The image is well balanced, processed
and technically sound, and the nearby lights reflecting off the front face of the cross helps to bring out detail that would normally be lost
during a night time exposure like this.
All entries and winners may be viewed in video via the Auckland Astronomical Society website at http://
www.astronomy.org.nz
Beaumont Prize 2014
Results and Judges Comments by J.C.B. White
Acknowledgements
The Editorial Team
Without the continuing efforts of the Journal’s editorial team: Clive Bolt, Shaun Fletcher and Milina Ristic, there would be no Beaumont
prize, and their selection of articles from members and from other media helps to keep members informed of new and interesting developments across many aspects of modern astronomy.
Gavin Logan
Gavin presents the monthly film nights, which always draw an appreciative audience, and writes short summaries of them to inform those
who didn’t attend about the treat they missed; he also contributes brief reports on many of the dark sky and other Society events.
Alan Gilmore
For a long time now, Alan has prepared monthly sky charts and commentaries on interesting objects for amateur viewers; they are always
helpful for those who want suggestions of what to look for. He is about to retire from his position at Mt John Observatory, and his considerable contribution to amateur astronomy needs to be recognized and acknowledged
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society journal, DECEMBER 2014
Summaries of articles considered for the Beaumont Prize
The Beaumont Prize requires authors to show a high standard of writing, and the call for entries states that articles about observing, personal experiences and the use and maintenance of equipment meet the judging criteria perfectly. The articles considered this year were
all of a high standard, and covered a wide range of topics.
Dec 2013 - Keith Smith “Processing FITS images”
A concise step-by-step guide to what processing is needed in order to get the best final images from a raw data set.
Jun 2014 - Keith Smith “Basics of photography”
An easily-understood summary of the various camera settings which have to be set correctly to obtain a satisfactory exposure.
Dec 2013 - Stan Walker “Colour photometry of variable stars”
A careful explanation of the terms used in analyzing colour photometric data, and some illustrative examples of data sequences and what
physical characteristics of the stars can be deduced from them.
Jun 2014 - Stan Walker “Pulsating stars
Follows on with descriptions of the physical processes which can be deduced from observations of stars in which the variation in brightness is due to pulsations, and some examples of several types of these.
Jun 2014 - Nalayini Brito “Matariki”
Takes a well-known star cluster, the Pleiades, and outlines the variety of star types which can be seen in it, and describes the stellar life
cycle which this variety illustrates.
Oct 2014 - Nalayini Brito “Imaging the lunar eclipse”
Brief article with a number of illustrations, and suggestions for how to obtain images of the lunar eclipse of 8 Oct 2014.
Oct 2014 - Elena Bloksberg “Dark Matter”
Critically examines the data used to deduce the amount of dark matter in an example galaxy UGC711, and poses the question, “are we
really detecting dark matter, or are our measurements (optical and radio astronomy) actually about different physical quantities.
Assessments
The assessments accord with the criteria for awards: a good standard of writing and some preference for articles on observing and practical amateur astronomy.
First Prize
Stan Walker:“Colour photometry of variable stars”
Clear expositions of both the observation and the interpretation of astronomical measurements which an increasing number of our members are now equipped to participate in making.
Second Prize
Nalayini Brito: “Matariki”
A scholarly summary of the different aspects of the life cycles of stars as illustrated in the diversity of objects to be seen in the Pleiades
cluster.
Special mention
Elena Bloksberg: “Dark Matter”
Every scientific theory must be under constant and critical appraisal and re-appraisal. This article is a brave, preliminary approach to such
a re-appraisal of the theory of dark matter.
www.astroNoMy.org.nz
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Calendar and Events
FEBRUARY PROGRAMME
DECEMBER PROGRAMME
Mon 1
7:00pm
Young Astronomers with
Margaret Arthur
Mon 2
8:00pm
Intro to Astronomy with
Bernie Brenner
Mon 1
7:00pm
Astrophotography Group
Fri 6
8:00pm
Practical Astronomy with Bill
Thomas
7:00 pm
8:00pm
Young Astronomers with
Margaret Arthur
Mon 09
8:00pm
Monthly meeting
Subject TBA
Mon 16
7:00pm
Astrophotography Group
8:00pm
Practical Astronomy with Bill
Thomas
8:00pm
Film Night February
Mon 8
8:00pm
Monthly Meeting Dec - The
2014 Debate: Should Pluto
be a Planet?
Mon 15
8:00pm
Intro to Astronomy with
Bernie Brenner
Mon 22
8:00pm
Film Night December - How
to Explore the Universe
Mon 23
TBA
JANUARY 2015
Film Night DECEMBER
Monday 22nd December at 8:00pm
With Gavin Logan
Young astronomers
TImes and format
How to Explore the Universe
With Margaret Arthur
A film from the Sci Fi Science series that looks at how future
space travel might work and whether it could be possible to
travel faster than the speed of light. This is a very futuristic view
of space travel taking concepts from science fiction and looking
at whether they could ever become reality.
Young Astronomers is the session for our younger members,
aged 6yrs upwards.
Monthly Meeting December
Monday 08 December, 2014 at 8:00pm
The 2014 Debate: Should Pluto be a Planet?
In 2006 the International Astronomical Union (IAU) stripped Pluto
of its planet-hood, demoting it to dwarf planet status. Ever since,
the Pluto is a Planet argument has seen ranging debate on both
sides of the fence. Should it be reinstated to its former glory?
What about the other Dwarf Planets in our Solar System?
The debate will be held on Monday 08 Dec, 2014 at 20:00Hrs,
and the winning team will be decided by audience vote, so come
along to what will be a fantastic evenings entertainment.
To register as a debater or for more info, email Oana on events@
astronomy.org.nz or call her on 0212 362 962.
Astrophotography Group DecEMBER
Monday 1st December at 7:00pm
Keith Smith
The Astrophotography Group discusses the practical aspects of
astrophotography.
This month the 2015 Harry Williams Astrophotography
Competition winner Mike Mackinven is the guest speaker
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As usual, club meetings and events are suspended during the
month of january.
society journal, DECEMBER 2014
At 7pm Margaret Arthur leads an interactive session covering
various current topics with plenty of question and answers.
At 8pm David Wardle will work with the older members of the
group who are working on a range of research projects.
Members are welcome come to either or both session
Welcome new members
Patrick Gailer (ordinary)
Alastair Emerson (ordinary)
Tamar Wolf (ordinary)
November Society Meeting - Monuments Tied to the Sky:
The Controversial Heritage of Ancient Astronomy
by AAS
Speaker/Host: Prof. Clive Ruggles
Professor Ruggles presented a packed
audience of society members with a
fascinating, informative and sometimes
amusing look into the world of Archeoastronomy and his work with the IAU and
UNESCO.
A video of this lecture is available on
request from the Society library.
Society Council and Officers
Society Contacts
PresidentBill Thomas
09 478 4874
Vice-President
Grant Christie
021 024 04992
Treasurer &Andrew Buckingham
09 473 5877
Membership
Secretary
Gavin Logan
022 691 2055
Curator of
Graham Beazley
09 537 1313
Instruments
Librarian
Jerina Grewar
09 444-5086
Telescope Hire
Steve Hennerley
027 245 644
Journal EditorsClive Bolt
09 534 2946
Shaun Fletcher
09 480 5648
Milina Ristić
029 912 4748
CouncilBernie Brenner
09 534 4103
Jonathan Green09 415-7284
David Britten
09 846 3657
Special EventsOana Jones
021 236 2962
Auckland Astronomical Society Inc,
PO Box 24187, Royal Oak,
Auckland 1345, New Zealand
Email
[email protected]
Journal
[email protected]
Website
www.astronomy.org.nz
Facebookfacebook.com/AuckAstroSoc
Twitter @AuckAstroSoc
Membership enquiries:
contact Andrew Buckingham at [email protected]
or by phone on 09 473 5877 or 027 246 2446
Training Sessions
We will be conducting telescope training sessions at 7pm on the 1st and 3rd Mondays before the ‘Intro to
Astronomy’ and ‘Practical Astronomy’ sessions. This will enable members to:
• Learn to use the Society rental equipment. Note there are a number of new items being added to the
rental range.
• Bring along your own telescope for lesson on how to best use it.
• Learn to use the large EWB Telescope at Stardome.
For more information, please contact Andrew Buckingham or Steve Hennerley.
www.astroNoMy.org.nz
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Film Night November - Comet Catcher - The
Rosetta Landing.
By Gavin Logan
A very well attended November film night featured a double feature on
the Rosetta Mission to orbit the comet 67P/Churyumov-Gerasimenko
and then land a probe (Philae) on it. The first film covered the
development of the project, difficulties with the mission and discoveries
made by the spacecraft so far. Initial difficulties with the project and
delays mean a change of target. This meant putting the probe into
hibernation for several years and then bring all the equipment back to
life. Gravity of just 1000 of Earths required making a lander that could
be anchored on to the surface of the comet.
The second film, which was a sky at night special showed the landing
and the two day of information collecting until Philae’s batteries went
flat. The comets surface was harder than expected and the anchoring
equipment did not work as planned and the lander bounced off the
comet twice before settling on the surface in a position with little
sunlight. One bounce was estimated to be more than a kilometre. In
spite of these problems the lander was able to conduct virtually all of
the planned tasks and returned information that will take scientist year
to analysis. The films showed some amazing photos of the comets
A close up of comet 67P/Churyumov-Gerasimenko’s
surface.
surface.
Rosetta will orbit the comet as it goes close to the sun and keep sending back valuable data.
Next month’s film night will be on Monday 22th December at 8pm at Stardome. It features A film from the Sci Fi Science series
that looks at how future space travel might work and whether it could be possible to travel faster than the speed of light. This is
a very futuristic view of space travel taking concepts from science fiction and looking at whether they could ever become reality..
A large attendance at November’s Film Night for the Rosetta double feature
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society journal, DECEMBER 2014
10th December - Special Lecture at University of Auckland
Public Lecture: The Dark Side of Astronomy
10 December 2014 6pm
Venue: Fisher and Paykel Appliances Auditorium, Owen G Glenn Building
University of Auckland
Cost: Free. All welcome
Come and hear Nobel Prize winner Professor Brian Schmidt tell the story of the discovery of dark
energy and cosmologist Associate Professor Tamara Davis explain its implications for fundamental
physics. You’ll hear them chat about event horizons, wonder about the future of the universe, banter
about the energy of the vacuum, and question the fundamental nature of reality.
Please register at http://www.eventbrite.co.nz/e/the-dark-side-of-astronomy-tickets-14402110099
Society Telescopes for Hire
The Society has a wide range of telescopes for hire to members.
If you are looking to purchase or upgrade a telescope and are not sure what to buy, this is a very good
way to evaluate some of the available equipment. See also the advertisement on the back page.
The Society does, of course, have more telescopes and other equipment, and you will start to see this
equipment being made available to members as rental gear; including some equipment more suited for
experienced members as well as beginners. Three items that are now newly available for rental include:
•
Celestron C5 5” SCT on iOptron Minitower Computerised GoTo mount
•
Celestron Nexstar5 5” SCT on a computerised GoTo Alt/Az mount with tripod
•
Meade 90mm Achromatic Refractor on a manual Equatorial Mount.
If you have a project idea where this telescope or other Society equipment may help, particularly if you
are happy to write a short article for the journal, please see Steve or Graham.
The Society is also keen to hear what members would like to have available for rental (the availability of the C5 scopes is in response
to a member request for a more portable rental option). Any submissions and ideas, or any questions or queries regarding rental
equipment should go to Rental Coordinator, Steve Hennerley at [email protected] or on 027 245 6441
For advice on telescope maintenance, repairs or any other questions about Astronomical Society instruments, Curator of Instruments,
Graham Beazley can be contacted on 09 5371313/021 537610
www.astroNoMy.org.nz
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Processing FITS with MaxIm DL
by Keith Smith
M
axIm DL is a program that is, not
only used for processing images,
but can be also used to control
the entire observatory and telescope, able
to do tasks such as dome rotation, focusing,
and tracking. It is a rather expensive
package but it is possible to get the subset
for image processing. Still a bit expensive
compared to other alternatives – some of
which are free – but once mastered, it is
very powerful. Experts that combine MaxIM
with Photoshop can produce some really
stunning images. I’m still trying to get the
hang of what all the various functions and
filters do, but I’m getting reasonable results
– still working on impressive though.
Here’s a brief resume of what I’ve figured
out so far. If readers have any useful hints
and tips they can add, please send them to
me, via the Society, and I’ll combine them
into a future column.
All the FITS I work with have already been
calibrated. This means darks, flats, and
biases have already been applied so, what
is left should be noise free and ready for
stacking.
Upon starting MaxIM, the main window
appears as well as several other smaller
ones. The only one that you really need is
the Screen Stretch window which tells you
the distribution of pixels between black
and white. If it’s not there, you can get it
by selecting View->Screen Stretch from
the top menu or pressing CTRL/H (holding
down the Ctrl key and pressing H).
Select Process>Stack or click on the ‘+’
button. This brings up the stacking window
with the tabs: Select/Quality/Align/Color/
Combine. Clicking on the Select tab
allows you to select the FITS you want for
the object, usually a combination of light
frames taken through the clear/red/green/
blue filters, if you’re going for true colour
images. There’s usually no need to change
the default settings for anything, unless you
know what they do, so I skip past Quality
and Align (which defaults to Auto – Star
Matching), and click on Color (sorry –
USA spelling) to enter the parameters for
the filters. Different filters have different
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society journal, DECEMBER 2014
weightings and I presume they are provided
by the manufacturer but it is here where
you enter those numbers down the top left
to bottom right of the 3x3 colour matrix.
I presume the other cells are for special
effects. Again, leave the luminance weight
at 100%. The theory is, that most of the
data is in the luminance, which is usually
shot in high resolution and the colour
frames just carry the colour data and are
shot in a lower resolution. This is usually
known as ‘binning’ and a 1x1 bin uses all
the pixels in a CCD to produce the image
whereas a 2x2 bin, combines 4 pixels on the
CCD to produce one on the image and a
3x3 bin combines 9 CCD pixels to produce
1 image pixel.
Once those are entered, click on the
Combine tab. Select your combination
method then don’t forget to click on ‘Go’ –
otherwise nothing happens. The input FITS
will then be combined and produces one or
more output FITS, usually a combined LRGB
image or an L image and an RGB image.
Now you’ve got those, the next thing to do
is to tease the data out. It’s all in there but it’s
all squashed into a thin area between black
and white. You can use careful applications
of ‘Curves’ to stretch it out, followed by
adjustments of the black and white points
under ‘Levels’, but to save time, you can
use ‘Digital Development Processing’ (DDP)
to get it out. This is under Filter>Digital
Development. You can then use iterations
of curves, followed by more black/white
point adjustments to tweak the data.
I’ve been trolling the ‘net looking for helpful
hints and tips on DDP and Deconvolution
(a system for sharpening and cleaning up
images. There are several settings that can
be tweaked and it is recommended that the
user experiment to see what works best.
This is what I found.
Upon opening DDP, you will see it’s dialog
box. Set the filter type to None, then
click on Auto under background to see
what number comes up. Some people
recommend reducing that number by 200
as DDP can be a bit aggressive at times. To
do this, click on Mouse then click on Auto
again to turn it off, and reduce the number
by 200 (minimum zero). Leave the mid-level
setting at Auto then click OK.
Next thing to do is to run a Deconvolution,
under Filter>Deconvolve. Deconvolution
does sharpening as well as trying to make
stars smaller by reducing the PSF (Point
Spread Function). The first tab is Noise
Model and, under that, click Auto Extract
to get the background noise value. If you
know the Gain of your CCD camera then
enter that under e-/ADU, otherwise go with
the default. Just make sure that the Poisson
Distribution click box is ticked. Under the PSF
model tab, select ‘Gaussian’, click on ‘Select
from Image’ then click on the centre of a
star that is round and hasn’t been clipped
to get it’s maximum value. It should be less
than 65000. If it’s higher, find another star.
The PSU value returned may be too high so
it is recommended that it be halved then
the process ran. If you’re not sure about the
results, undo the deconvolution, adjust the
PSU upwards a bit and do it again. Under
the Deconvolve tab, select Lucy-Richardson
and ten iterations to start. Again, you can
undo, change the number of iterations and
redo.
Don’t forget to check your levels between
each step to ensure your black and white
points are at each end of the histogram
otherwise you may be either clipping data
or including stuff you don’t want. You can
also adjust the gamma (grey point) as well
to get a more pleasing image.
Other things you can do are:
Colour>White Balance: - if you know that
star should be white and it’s not, click on it.
Colour>Adjust Saturation: to make colours
bolder.
Filter>Flatten Background: click on four or
more background points to smooth out the
background
Once you are satisfied, then save it as a
16bit TIFF for further processing in GIMP or
Photoshop.
Well, that’s all I’ve learnt about MaxIm so
far. Once I collect more tips to share, there
may be a sequel article.
Sunspots in November 2014
Images By Danut Ionescu
The Sun Auckland 2014-11-23 at 13:15 NZ Time: Sunspots 2216 and 2217
Lunt100mm Solar telescope Ha with B1200 blocking filter on Zeiss and camera Flea2 all property of Stardome Observatory-Auckland,
New Zealand. Processed with AS2, Fitswork4 and Photoshop.
Sunspot 2209 and around-Detail with 2x Barlow (1’25 from Meade). Auckland 2014-11-23 at 14:36 NZ Time Lunt100mm Solar
telescope Ha with B1200 blocking filter on Zeiss and camera Flea2 all property of Stardome Observatory-Auckland, New Zealand.
Processed with AS2, Fitswork4 and Photoshop.
www.astroNoMy.org.nz
11
Astronomers solve puzzle about bizarre object
at center of our galaxy: Enormous black hole
drove two binary stars to merge
from University of California - Los Angeles
Telescopes from Hawaii’s W.M. Keck Observatory use a powerful technology called adaptive optics, which enabled UCLA astronomers to
discover that G2 is a pair of binary stars that merged together, cloaked in gas and dust. Credit: Ethan Tweedie
The mystery about a thin, bizarre
object in the center of the Milky
Way that some astronomers
believe to be a hydrogen gas
cloud headed toward our galaxy’s
enormous black hole has been
solved by astronomers.
F
or years, astronomers have been puzzled by a bizarre object in the center of
the Milky Way that was believed to be
a hydrogen gas cloud headed toward our
galaxy’s enormous black hole.
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society journal, DECEMBER 2014
Having studied it during its closest approach
to the black hole this summer, UCLA astronomers believe that they have solved the riddle of the object widely known as G2.
torn apart by the black hole, and that the
resulting celestial fireworks would have
dramatically changed the state of the black
hole.
A team led by Andrea Ghez, professor of
physics and astronomy in the UCLA College,
determined that G2 is most likely a pair
of binary stars that had been orbiting the
black hole in tandem and merged together
into an extremely large star, cloaked in gas
and dust -- its movements choreographed
by the black hole’s powerful gravitational
field. The research is published today in the
journal Astrophysical Journal Letters.
“G2 survived and continued happily on its
orbit; a simple gas cloud would not have
done that,” said Ghez, who holds the Lauren B. Leichtman and Arthur E. Levine Chair
in Astrophysics. “G2 was basically unaffected by the black hole. There were no fireworks.”
Astronomers had figured that if G2 had
been a hydrogen cloud, it could have been
Black holes, which form out of the collapse
of matter, have such high density that nothing can escape their gravitational pull -- not
even light. They cannot be seen directly,
but their influence on nearby stars is visible
and provides a signature, said Ghez, a 2008
MacArthur Fellow.
Ghez, who studies thousands of stars in the
neighborhood of the supermassive black
hole, said G2 appears to be just one of
an emerging class of stars near the black
hole that are created because the black
hole’s powerful gravity drives binary stars to
merge into one. She also noted that, in our
galaxy, massive stars primarily come in pairs.
She says the star suffered an abrasion to its
outer layer but otherwise will be fine.
Ghez and her colleagues -- who include
lead author Gunther Witzel, a UCLA postdoctoral scholar, and Mark Morris and Eric
Becklin, both UCLA professors of physics
and astronomy -- conducted the research
at Hawaii’s W.M. Keck Observatory, which
houses the world’s two largest optical and
infrared telescopes.
When two stars near the black hole merge
into one, the star expands for more than 1
million years before it settles back down,
said Ghez, who directs the UCLA Galactic
Center Group. “This may be happening
more than we thought. The stars at the
center of the galaxy are massive and mostly
binaries. It’s possible that many of the stars
we’ve been watching and not understanding may be the end product of mergers that
are calm now.”
Ghez and her colleagues also determined
that G2 appears to be in that inflated
stage now. The body has fascinated many
astronomers in recent years, particularly
during the year leading up to its approach
to the black hole. “It was one of the most
watched events in astronomy in my career,”
Ghez said.
Ghez said G2 now is undergoing what she
calls a “spaghetti-fication” -- a common
phenomenon near black holes in which
large objects become elongated. At the
same time, the gas at G2’s surface is being heated by stars around it, creating an
enormous cloud of gas and dust that has
shrouded most of the massive star.
Witzel said the researchers wouldn’t have
been able to arrive at their conclusions without the Keck’s advanced technology. “It is a
result that in its precision was possible only
with these incredible tools, the Keck Observatory’s 10-meter telescopes,” Witzel said.
The telescopes use adaptive optics, a powerful technology pioneered in part by Ghez
that corrects the distorting effects of the
Earth’s atmosphere in real time to more
clearly reveal the space around the supermassive black hole. The technique has
helped Ghez and her colleagues elucidate
many previously unexplained facets of the
environments surrounding supermassive
black holes.
“We are seeing phenomena about black
holes that you can’t watch anywhere else
in the universe,” Ghez added. “We are
starting to understand the physics of black
holes in a way that has never been possible
before.”.
The Protoplanetary Disk of HL Tauri from ALMA
Image Credit: ALMA (ESO/NAOJ/NRAO), NSF
Explanation: Why does this giant disk have gaps? The exciting and probable answer is: planets. A mystery is how planets massive
enough to create these gaps formed so quickly, since the HL Tauri star system is only about one million years old. The picture on which
the gaps were discovered was taken with the new Atacama Large Millimeter Array (ALMA) of telescopes in Chile. ALMA imaged the
protoplanetary disk, which spans about 1,500 light-minutes across, in unprecedented detail, resolving features as small as 40 light
minutes. The low energy light used by ALMA was also able to peer through an intervening haze of gas and dust. The HL Tauri system
lies about 450 light years from Earth. Studying HL Tauri will likely give insight into how our own Solar System formed and evolved.
www.astroNoMy.org.nz
13
The Evening Sky in December 2014
By Alan Gilmore, University of Canterbury‘s Mt John Observatory, www.canterbury.ac.nz
14
society journal, DECEMBER 2014
T
he twilight sky is briefly lit by Venus
the brilliant ‘evening star’. It sets in
the southwest about an hour after the
Sun. It is catching up on Earth from the far
side of the Sun. In the first half of 2015 it
will swing outward from the Sun and set
progressively later. Though bright, Venus is
a small featureless disk in a telescope. It is
250 million km away mid month. In late
December the planet Mercury appears as a
star below and left of Venus. As Mercury
swings out from the far side of the Sun faster than Venus it will appear move close to
the brighter planet. Low in the western sky,
above and right of Venus is Mars. It looks
like a medium-bright orange star and sets
around 11 p.m. NZDT.
The brightest true stars are in the east and
south. Sirius, the brightest of all the stars,
is due east at dusk, often twinkling like a
diamond. Left of it is the bright constellation of Orion. The line of three stars makes
Orion’s belt in the classical constellation.
To southern hemisphere skywatchers they
make the bottom of ‘The Pot’. The faint
line of stars above and right of the three is
the Pot’s handle. At its centre is the Orion
Nebula, a glowing gas cloud nicely seen in
binoculars. Rigel, directly above the line of
three stars, is a hot blue-giant star. Orange
Betelgeuse, below the line of three, is a
cooler red-giant star.
Left of Orion is a triangular group making
the upside down face of Taurus the bull. Or-
ange Aldebaran is the brightest star in the
V shape. Aldebaran is Arabic for ‘the eye
of the bull’. Still further left is the Pleiades
/Matariki/Seven Sisters/Subaru cluster, impressive in binoculars. It is 440 light years*
away.
Canopus, the second brightest star, is high
in the southeast. Low in the south are the
Pointers, Beta and Alpha Centauri, and Crux
the Southern Cross. In some Maori star lore
the bright southern Milky Way makes the
canoe of Maui with Crux being the canoe’s
anchor hanging off the side. In this picture
the Scorpion’s tail can be the canoe’s prow
and the Clouds of Magellan are the sails.
The Milky Way is wrapped around the horizon. The broadest part is in Sagittarius
low in the west at dusk. It narrows toward
Crux in the south and becomes faint in the
east below Orion. The Milky Way is our
edgewise view of the galaxy, the pancake
of billions of stars of which the Sun is just
one. The thick hub of the galaxy, 30 000
light years away, is in Sagittarius now low
in the west. The nearby outer edge is the
faint part of the Milky Way below Orion. A
scan along the Milky Way with binoculars
will show many clusters of stars and a few
glowing gas clouds.
The Clouds of Magellan, LMC and SMC,
high in the southern sky, are two small
galaxies about 160 000 and 200 000 light
years away, respectively. They are easily
seen by eye on a dark moonless night. The
larger cloud is about 1/20th the mass of the
Milky Way galaxy, the smaller cloud 1/30th.
Very low in the north is the Andromeda
Galaxy seen in binoculars in a dark sky as a
spindle of light. It is a bit bigger than our
Milky Way galaxy and nearly three million
light years away.
Jupiter rises in the northeast around 1:30
a.m. at the beginning of the month, the
brightest ‘star’ in the morning sky. By
New Year it is up at 11:30. It shines with
a steady golden light, obeying the rough
rule that stars twinkle and planets don’t. It
is 710 million km away mid month. A small
telescope shows the planet’s disk with Jupiter’s four big moons like stars lined up on
each side. They change sides from night to
night as they orbit Jupiter.
The Geminid meteor shower peaks on the
morning of the 15th. The meteors appear
to come from the constellation of Gemini,
low in the northeast at midnight, moving to
the north by dawn. The meteors are clumps
of dust from a comet. Friction with the air
heats them up and makes the air around
them glow.
Saturn rises about 4:30 a.m., mid month,
a little south of due east. It is the brightest ‘star’ in that part of the sky. Saturn is
1620 million km away and worth a look
in any telescope. To its right is the orange
star Antares, the heart of the Scorpion. The
crescent Moon will be left of Saturn on the
morning of the 20th.
Diary of events in December by RASNZ
Date (NZDT)
Diary of Solar System Events in DECEMBER 2014 for New Zealand
December 1
Uranus 1.1 degrees south of the
Moon Occn
December 4
Mercury 3.9 degrees north of Antares
December 6
Aldebaran 1.4 degrees south of the
Moon
Moon full
December 20
Venus 3.2 degrees south of Pluto
December 21
Moon southern most declination
(-18.7 degrees)
Solstice
December 22
Moon northern most declination
(18.7 degrees)
Moon new
Uranus stationary
Pluto 2.8 degrees south of the Moon
December 24
Moon at perigee
December 8
Mercury superior conjunction
December 25
December 9
Jupiter stationary
Mars 5.6 degrees south of the Moon
Mercury 4.3 degrees south of Pluto
December 12
Jupiter 4.9 degrees north of the
Moon
Regulus 4.2 degrees north of the
Moon
Moon at apogee
December 26
Neptune 4.0 degrees south of the
Moon
December 28
Moon first quarter
December 29
Uranus 0.9 degrees south of the
Moon Occn
December 7
December 14
Moon last quarter
December 17
Spica 2.7 degrees south of the Moon
December 19
Saturn 1.5 degrees south of the
Moon
www.astroNoMy.org.nz
15
BINARY STARS WITH ECLIPSES
by Stan Walker
Introduction:
There are many thousands of known eclipsing binary stars with periods ranging from a few tens of minutes to several, even many, years.
Probably 50% or more of stars are members of binary or multiple systems. The widely separated ones lead their own lives with little interaction between them but if they’re close to each other then the evolution of these objects becomes complex and fascinating.
Eclipses can only take place if we’re close to the plane of revolution of a binary system. But even some of the non-eclipsing objects have
interesting histories. Many popular books quote Sirius as a good example of an A0 star - but spectral analysis of its envelope reveals that
when Sirius B became a white dwarf star the envelope of Sirius A became heavily polluted by the ejection of highly evolved material, rich
in heavy elements. Sirius A may also have become slightly more massive but by how much? This event must have been fascinating at the
time but what did it look like? We’ll never know.
Some Massive Binary Systems:
For these we turn to one of the richest star forming regions of our galaxy - the eta Carina nebula and the surrounding associations. Eta
itself is part of a binary system with a companion in an elongated orbit so that every 5.52 years there is a perihelion passage with as yet
not understood spectral and other changes.
In this same region is QZ Carinae, the variability of which was discovered and measured using UBV photometry at the Auckland Observatory. This system comprises two pairs of massive stars, one showing eclipses every 5.99857 days and a non-eclipsing pair with a period
measured spectroscopically of ~20.74 days, the total mass being about 95 solar masses. Even at about 7000 light years and heavily obsured by interstellar gas and dust, at V = 6.2 it’s almost naked eye.
Then in the north there is epsilon Aurigae with eclipses every 27.1 years. These last many months. The nature of the components of this
system is still not clearly understood. Some like a model with two high mass stars, others suggest highly evolved low mass objects. Probably the eccentricity of the system supports the former - young massive objects - idea better. In the south we have BL Teklescopii with a
period of 778 days or so.
Algol Eclipsing Binaries - EA:
To avoid too much confusion different types of eclipsing bodies are grouped within a class
designation. The simplest light curves are of the Algol (beta Persei) type where the components are not strongly distorted by tidal effects.
Such a system is shown in Figure 1 - the colours are arbitrary to provide good contrast. There’s also a little artistic licence - strictly speaking
the red star is completely behind the yellow star at point 4, which should be a mirror image of position 2.
Let’s analyse what we’re seeing. The orbit of the smaller, cooler star is shown with four different points marked. At points 1 and 3 the
two stars are both visible and the system is at its brightest. At point 2 the cool red star passes in front of the hotter yellow object so the
brightness of the system drops considerably. At point 4 the red star passes behind the hotter star and another, less pronounced drop in
brightness takes place. These are primary and secondary eclipses respectively.
Figure 1: This is a fairly stylised light curve with a few
inconsistencies. Unless the orbit is eccentric the red star is not visible
at point 4 being totally eclipsed (the light curve is flat bottomed
there) and the duration of the eclipses should be identical. To see it
like shown we would have to be looking directly along the long axis
of the ellipse but even then the durations of totality would differ. Still,
Wikipedia provides a helpful illustration.
Eclipses come in two types: a sharp minimum with no flat bottom is a partial eclipse with the smaller star not being completely in front or
behind the larger one, and total eclipses when the smaller star is completely over or behind the larger star show a flat curve at minimum.
There is other information in Figure 1. Using the type of radial velocity curves shown in Figure 2 the actual dimensions of the stars can
be determined. That of the larger star is not certain unless it’s a central transit but application of the L = R2 * T4 relationship will provide
16
society journal, DECEMBER 2014
a useful indicator.
Figure 2: Assuming a circular orbit the amplitude of each star in the
radial velocity curve can be determined. Thus the duration of the
ingress or egress multiplied by the combined velocities will provide a
measure of the smaller star’s diameter.
The duration of ingress/egress plus the duration of totality , the total
multiplied by the sum of the two orbital speeds provides a minimum
diameter for the larger star.
Other things come into the picture: the system is usually a little brighter each side of the secondary eclipse due to a reflection effect - the
hot star heats the inner face of the cool star -and gravitational effects dim the outer faces of both stars. There are always some tidal effects
which cause the latter. But, in general, most of the situation in non-interacting stars follows the above rules.
Close Binary and Interacting Binary Stars:
In these stars it’s often difficult to see the points when ingress begins and ends. These objects are tidally distorted or, in the case of the very
short period objects, may share a common envelope. The uneclipsed light curve is strongly convex. Periods range from about 3 hours to
hundreds of days as we see with W Crucis in Figure 3.
Figure 3: W Crucis was another star observed from Auckland at the
request of Ed Budding. Even with an orbital period of 198 days it
still shows very strong tidal effects so that it’s difficult to see from the
light curves when one star begins to obscure the other. These two
stars are very massive and rather egg-shaped (distorted ellipsoids) and
the eclipses are close to or actually total. The mean colours are about
B-V = 1.2 and U-B = 0.6 which suggests the system is interacting,
with much gas around. The spike in the U-B curve near primary
minimum reinforces that idea. These measures were made about 30
years ago - it’s time for another look, perhaps.
Variable Stars South has a strong eclipsing binary section and is interested in the shorter period W Ursae Majoris stars of this group. Their
periods are from about two hours to a day. Observers are looking at several aspects - checking catalogue periods to study possible changes, or finding periods if none are available - and using analysis software to endeavour to model their observations. Contact the website at
www.variablestarssouth.org and look under projects or research.
Figure 4 on the next page shows aspects of one of these stars - YY Gruis. Observations by Tom Richards, Director of Variable Stars South.
The upper part of the graph shows colours, V-I at the top, B-V below. Both show substantial colour or temperature variations. The lower
part shows the light variations through three filters, I at the top, then V and at the bottom, B. As we would expect from the colour variations, the B curve has the largest amplitude.
The curves are not symmetric - the egress from the secondary or shallower minimum is rather distorted. What this means might perhaps
be discloed in the later analysis once a little more data has been collected. The short period is a great advantage - we’re seeing two nights’
data with three eclipses plus one which was interrupted by cloud.
Other Close Binaries - Cataclysmic Variables:
Without moving into the pulsar area the shortest period interacting stars include the various types of cataclysmic variables, CVs. But that
is a very complex field so more about those stars another time. They include Dwarf Novae, Classical Novae, Recurrent Novae, Polars and
Intermediate Polars.
One of the more interesting of these objects is V803 Centauri, a pair of helium white dwarf stars with an orbital period of ~26 minutes,
dwarf nova outbursts every 23 hours and an extreme mass ratio of 50:1. The system would fit comfortably inside the diameter of our
Moon’s orbit.
www.astroNoMy.org.nz
17
Figure 4: Colour curves in the top section, actual light curves through each filter in the lower. The blank area between is, of course, the
daylight hours. This suggests that with a colleague in South America or South Africa a continuous curve could have been obtained.
Unusual Binary Stars:
Many sytems have one star which itself is an intrinsic variable, usually pulsating. The eclipsing binary star group of VSS has found a numbe
of objects which appear to contain a delta Scuti variable star - a main sequence Cepheid type pulsator. Others contain a semi-regular or
Mira star, although in the latter case this will dominate the system. Presence of a much hotter companion buried in Mira’s stellar wind is
detected spectroscopically and SY Fornacis is another such object.
QZ Carinae - a Real Challenge:
When we began looking at this star in 1970 to prove its variability we were frustrated by the almost 6 day period. All the measures fell
into 6 closely matched bins. We were fortunate that two of these included both the primary and secondary minima. From these and later
spectrographic measures Leung and his colleagues, along with others, managed to determine the four main components of the system.
They also drew up the mean light curve of Figure 5.
Figure 5:The solid line joining the points represents the fit to the
original 58 measures in Auckland. The open blue squares are all the
Auckland measures without correction for the light time effects, the
pale green points are the same measures with light time corrections.
Only the earliest of the uncorrected points fit the curve well.
18
society journal, DECEMBER 2014
The first question is why are the eclipses, which appear total, so shallow at about 0.22 and 0.20 magnitudes? This suggests another
source of light which the radial velocity measures identified as the primary pair with an eccentric orbit of ~20.74 days.
Why are the observations so noisy when fitted to the mean curve. It’s speculated that there are light variations from the elliptical orbit of
the tidally distorted primary pair superimposed on the measures. There is a campaign this summer to endeavour to resolve this possibility.
This may be the reason why, of the few eclipses observed by other groups, some are flat bottomed, others are not. But there may well
be other effects like some mass flow causing brightness variations.
The Hubble Space Telescope was used to try to detect the star pairs individually but it appears that the timing was poor - the star pairs
were in line as viewed from our solar system. Fitting of each year’s measures to a mean light curve suggest a system orbital period of 3050 years and light time effects of up to +/- 7.2 hours. And to add to the difficulties the eclipses move eastward at 30 or so degrees each
year so a full light curve requires observations widely spaced in longitude - or, failing this, 12 patient years of measures.. A more detailed
account of this fascinating star can be found on the Variable Stars South website. But the eclipsing binary field is fascinating and acessible
to anyone with a DSLR or CCD camera. For further background look under QZ Carinae on the Variable Stats South Website.
And let’s conclude with a piece of astronomy for entertainment. One of the most spectacular stars in the sky, when seen through the
Edith Winstone Blackwell telescope with its four secondary supports, is Sirius - a real Xmas card star, and brilliant! We used to look for
Sirius B when it was near elongation in the orbit by using an occulting bar in the eyepiece - in this case a narrow cardboard strip across
the centre of the eyepice to block out Sirius A. A very successful technique but I have no idea of the separation of the pair at present.
2015 NZ Astronomical Yearbook
The 2015 Yearbook is now available.
This is a must-have astronomy almanac for what’s happening in the New Zealand skies for 2015!. The 2015 edition features topical articles
iincluding
- The Rosetta Mission
- Neteroites of New Zealand
- The Goldern Anniversary at Mt John Observatory
- Outdoor and Street Lighting
- New Horizons mission to Pluto
- Hubble Space Telescope - the first 25 years
- The Hunt for Another Earth
Also features
- Monthly sky guides and star charts
- Moon and Sun information for each day
- Meteor Showers for 2015
- Latest discoveries and technological advancements
- Information for beginners as well as veterans
- Contact information for NZ Astronomical Societies
Published by Stardome Observatory, the book is fully of spectacular images from New Zealand astrophotographers
Members can purchase the yearbook at the special member’s price of $14.00 (+ $2.50 postage). To order contact Andrew Buckingham by
email at [email protected] or phone 09 473 5877. It will also be available at any AAS meeting.
www.astroNoMy.org.nz
19
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