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Transcript
Bristol Astronomical Society Information Leaflet
In Memory of Dr Rodney Hillier
Vice-President of the Bristol Astronomical
Society
th
Solar Eclipse, Castle Park, Bristol, 20 March 2015
1
June 2015
Observing Calendar June 2015
Sunday
Monday
Tuesday
1
2
Sunrise: 5:00
Sunrise: 4:59
Sunset: 21:17
Sunset: 21:18
Moonrise: 19:53
Moonrise: 20:56
Moonset: 4:36
Moonset: 5:14
Conjunction for Moon
Full Moon
& Saturn
Mercury at aphelion
M13 is well placed
Observing Calendar June 2015
Wednesday
Thursday
Friday
Saturday
Saturday Observing
3
Sunrise: 4:58
Sunset: 21:19
Moonrise: 21:53
Moonset: 6:00
The Moon at aphelion
M12 is well placed
4
Sunrise: 4:57
Sunset: 21:20
Moonrise: 22:45
Moonset: 6:54
5
Sunrise: 4:57
Sunset: 21:21
Moonrise: 23:30
Moonset: 7:56
6
Sunrise: 4:56
Sunset: 21:22
Moonrise: none
Moonset: 9:04
Venus at greatest elongation east
M10 is well placed
No public observing
7
Sunrise: 4:56
Sunset: 21:23
Moonrise: 0:09
Moonset: 10:17
8
Sunrise: 4:55
Sunset: 21:23
Moonrise: 0:43
Moonset: 11:32
9
Sunrise: 4:55
Sunset: 21:24
Moonrise: 1:13
Moonset: 12:47
Moon at Last Quarter
10
Sunrise: 4:54
Sunset: 21:25
Moonrise: 1:42
Moonset: 14:03
Ophiuchid meteor
shower
The Moon at perigee
14
Sunrise: 4:53
Sunset: 21:28
Moonrise: 3:46
Moonset: 19:00
Mars at solar conjunction
15
Sunrise: 4:53
Sunset: 21:28
Moonrise: 4:27
Moonset: 20:05
16
Sunrise: 4:53
Sunset: 21:29
Moonrise: 5:14
Moonset: 21:04
Moon at perihelion
New Moon
17
Sunrise: 4:53
Sunset: 21:29
Moonrise: 6:07
Moonset: 21:54
18
Sunrise: 4:53
Sunset: 21:30
Moonrise: 7:06
Moonset: 22:36
IC4665 is well placed
19
Sunrise: 4:53
Sunset: 21:30
Moonrise: 8:07
Moonset: 23:11
20
Sunrise: 4:53
Sunset: 21:31
Moonrise: 9:10
Moonset: 23:41
Ophiuchid met shower
C/2012 F3 (PANSTARRS)
brightest
21
Sunrise: 4:53
Sunset: 21:31
Moonrise: 10:14
Moonset: none
June solstice
22
Sunrise: 4:53
Sunset: 21:31
Moonrise: 11:17
Moonset: 0:07
23
Sunrise: 4:54
Sunset: 21:31
Moonrise: 12:19
Moonset: 0:31
The Moon at apogee
24
Sunrise: 4:54
Sunset: 21:31
Moonrise: 13:21
Moonset: 0:53
Moon at First Quarter
25
Sunrise: 4:54
Sunset: 21:31
Moonrise: 14:24
Moonset: 1:16
Mercury at greatest
elongation west
26
Sunrise: 4:55
Sunset: 21:31
Moonrise: 15:28
Moonset: 1:40
27
Sunrise: 4:55
Sunset: 21:31
Moonrise: 16:32
Moonset: 2:06
28
Sunrise: 4:56
Sunset: 21:31
Moonrise: 17:37
Moonset: 2:35
29
Sunrise: 4:56
Sunset: 21:31
Moonrise: 18:40
Moonset: 3:10
Conjunction for Moon
& Saturn
NGC6633 well placed
30
Sunrise: 4:57
Sunset: 21:31
Moonrise: 19:41
Moonset: 3:51
2
11
12
Sunrise: 4:54
Sunrise: 4:54
Sunset: 21:26
Sunset: 21:27
Moonrise: 2:10
Moonrise: 2:39
Moonset: 15:19
Moonset: 16:34
Conjunction for Moon Asteroid 2 Pallas at
& Uranus
opposition
M92 is well placed
13
Sunrise: 4:53
Sunset: 21:27
Moonrise: 3:10
Moonset: 17:49
Conjunction for Venus
and M44
3
No public observing
(Festival of Nature)
No public observing
John Willis
Jane Clark
Nigel Kirkland
The Sun
Sun’s Position at Midday 15th June 2015
The Moon
June 25th and 26th: The Alpine Valley
An interesting valley on the Moon: The Alpine Valley
These are two good nights to observe an interesting feature on the Moon
if you have a small telescope. Close to the limb (on the 26th) is the Appenine mountain chain that marks the edge of Mare Imbrium. Towards
the upper end you should see the cleft across them called the Alpine valley. It is about 7 miles wide and 79 miles long. As shown in the image a
thin rill runs along its length which is quite a challenge to observe. Over
the next two nights the dark crater Plato and the young crater Copernicus
will come into view. This is a very interesting region of the Moon!
Solar Events for 2015
4
5
www.jb.man.ac.uk
The Moon
The Planets (June 1st, 15th & 30th at 00:00)
The Alpine valley
and the crater
Plato
6
www.stardate.org
7
www.heavens-above.com
The Planets
The Planets
Mercury
Mars
Mercury is at inferior conjunction (that is between us and the Sun) on the
30th May and then climbs slowly into the pre-dawn sky. It reaches greatest elongation west on the 24th June and will then be at magnitude +0.5
and have a phase of 35%. It should then be visible with binoculars low
above the east-northeast horizon as dawn breaks. Aldebaran, which lies
in front of the Hyades cluster, will then lie ~2 degrees down to its lower
right. By the end of June, Mercury is a little brighter (magnitude -0.1)
and will be ~6 degrees above the horizon around 45 minutes before sun
rise. To be honest, this is not a good month to observe Mercury.
Mars passes behind the Sun (superior conjunction) on June 14th, so is not
visible this month
Venus
Venus, shining brightly at magnitude -4.4 (increasing to -4.6 during the
month) dominates the western sky after sunset all month. It starts the
month in eastern Gemini and crosses into Cancer on the 2nd/3rd where it
will reach greatest elongation from the Sun on June 6th and will then lie
45.5 degrees away from the Sun. At the start of June it will be visible
abut half an hour after sunset and be ~29 degrees above the western
horizon. Its angular size increases from 22 to 32 arc seconds during the
month. Following greatest elongation, it becomes an increasingly narrow
crescent with its phase decreasing from 53 to 35%. By the end of June,
its elevation above the horizon at sunset will have dropped to 19 degrees
and it will set at around 11:35 BST. Venus has close encounters with the
open Cluster M44 (Beehive Cluster) in Cancer and, having passed into Leo
on the 25th/26th of the month, has a close encounter with Jupiter on the
30th.
June 12-13th after sunset: Venus close to the Beehive Cluster, M44, in
Cancer: After sunset on the nights of the 12—13 June, Venus passes close
to the Beehive Cluster, M44, in Cancer. M44 is also called 'Praesepe'.
8
Jupiter
Jupiter is now well past its best, but still stands out in the South to Southwest at nightfall Its brightness falls slightly from magnitude -1.9 to -1.8
whilst its angular size drops from 35 to 32.5 arc seconds. Jupiter starts the
month in Cancer but moves into Leo on the 9th of June in its eastwards progress towards the star Regulus. Our best views of the planet are now past
but, with a small telescope one may be able to see the equatorial bands in
the atmosphere and up to four of the Gallilean moons as they weave their
way around it.
June 30th after sunset: A close conjunction of Venus and Jupiter.
As Jupiter moves slowly towards Regulus in Leo throughout the month of
June, Venus is moving more quickly across the heavens from Cancer into
Leo and, on the 30th of the month, catches up with Jupiter when they come
just 21 arc minutes from each other. Interestingly, both planets will then
have the same angular diameter of 32 arc seconds, but whilst Jupiter sports
an almost fully illuminated disk, that of Venus will be a thin crescent just
34% illuminated. Low above the horizon, they will dominate the sky in the
west-northwest from around 22:30 BST until they set around an hour later.
Saturn
Saturn will be visible in the southeast at nightfall and will not set until the
early hours of the following morning. It is moving slowly in retrograde
motion in the eastern part of Libra, but close to the fan of three stars that
makes up the head of Scorpius and is only 3 degrees away from the fine
double star Beta Scorpii.
9
The Planets
The Sky This Month
Saturn Continued...
This is a good time to observe Saturn whose globe is ~18 arcs seconds
across and whose rings span some 41 arc seconds across. They make a
beautiful sight as are tilted 24 degrees from the line of sight - almost as
open as they can be.
To find it in the sky, follow the arc of the Plough's handle downwards to
first find the orange star Arcturus and continue down to find the white,
first magnitude star, Spica, in Virgo. Saturn, a little brighter than Spica,
lies in Libra down to its lower left and will appear slightly yellow in colour.
Held steady, binoculars should enable you to see Saturn's brightest moon,
Titan, at magnitude 8.2. A small telescope will show the rings with magnifications of x25 or more and one of 6-8 inches aperture with a magnification of ~x200 coupled with a night of good "seeing" (when the atmosphere is calm) will show Saturn and its beautiful ring system in its full glory.
As Saturn rotates quickly with a day of just 10 and a half hours, its equator bulges slightly and so it appears a little "squashed". Like Jupiter, it
does show belts but their colours are muted in comparison.
The thing that makes Saturn stand out is, of course, its ring system. The
two outermost rings, A and B, are separated by a gap called Cassini's Division which should be visible in a telescope of 4 or more inches aperture if
seeing conditions are good. Lying within the B ring, but far less bright
and difficult to spot is the C or Crepe Ring.
Planetary info source: www.jb.man.ac.uk & www.freestarcharts.com
10
This map shows the constellations seen towards the south at about 11pm
BST in mid June. High over head towards the north (not shown on the chart)
lies Ursa Major. As one moves southwards one first crosses the constellation
Hercules with its magnificent globular cluster, M13, and then across the
large but not prominent constellation Ophiucus until, low above the southern horizon lie Sagittarius and Scorpio. To the right of Hercules lie the arc of
stars making up Corona Borealis and then Bootes with its bright star Arcturus. Rising in the east is the beautiful region of the Milky Way containing
both Cygnus and Lyra. Below is Aquilla. The three bright stars Deneb (in Cygnus), Vega (in Lyra) and Altair (in Aquila) make up the "Summer Triangle".
11
‘Sky This Month’ : www.jb.man.ac.uk
The Sky This Month
The Sky This Month
Hercules
Between the constellation Bootes and the bright star Vega in Lyra lies the
constellation Hercules. The Red Giant star Alpha Herculis or Ras Algethi, its
arabic name, is one of the largest stars known, with a diameter of around
500 times that of our Sun. In common with most giant stars it varies its size,
changing in brightness as it does so from 3rd to 4th magnitude (see p 25).
The Globular Cluster M13 is easily found on the western side of the Hercules
"Keystone" asterism, 2.5 degrees south of Eta Herculis (η Her) along a line
connecting Eta Herculis (η Her) with Zeta Herculis (ζ Her). When viewed
through 10x50 binoculars, it appears as bright fuzzy ball with a well-defined
centre that is obviously non-stellar but without resolution. It forms a right
angled triangle with two nearby 7th magnitude stars. An 80 mm (3.1-inch)
telescope shows M13 as a uniform extended hazy disk about 8 arc minutes
across. At magnifications of about 100x the cluster appears like a zoomed in
version of that of the binocular view. A 100mm (4-inch) telescope will resolve some of the outer stars with many more visible in 150mm (6-inch) and
200mm (8-inch) instruments. The brightest star in M13 is variable star V11
(apparent magnitude +11.95).
In large amateur telescopes, M13 is truly sensational sight with the complete field awash with stars. When viewed through a 250mm (10-inch) telescope or larger, there are hundreds of stars visible against the dark background sky. The cluster appears 3-dimensional and breath-taking. In total, it
has an apparent size of about 20 arc minutes, though visually it appears
smaller, perhaps 12-13 arc minutes across. Also visible at medium/high
magnifications in telescopes of the order of 300mm (12-inch) or greater, are
three dark dust lanes that form a Y shape towards the southeast of the core.
This is known as the "propeller", first noticed by Bindon Stoney in the 1850s
from Birr Castle in Ireland using the 72-inch reflector, the largest telescope
in the world at the time.
12
Globular Cluster M13
13
Observing Notes
Planetary
Positions
15 June
1 June 23:00
15 June 22:00
30 June 21:00
14
15
The Sky This Month
The Sky This Month
Lyra
Lyra is dominated by its brightest star Vega, the fifth brightest star in the
sky. It is a blue-white star having a magnitude of 0.03, and lies 26 light years
away. It weighs three times more than the Sun and is about 50 times brighter. It is thus burning up its nuclear fuel at a greater rate than the Sun and so
will shine for a correspondingly shorter time. Vega is much younger than
the Sun, perhaps only a few hundred million years old, and is surrounded by
a cold, dark disc of dust in which an embryonic solar system is being
formed.
Globular Cluster M56
Ring Nebula M57
There is a lovely double star called Epsilon Lyrae up and to the left of Vega.
A pair of binoculars will show them up easily - you might even see them
both with your unaided eye. In fact a telescope, provided the atmosphere is
calm, shows that each of the two stars that you can see is a double star as
well so it is called the double double (see ‘Double Star of the Month’).
Between Beta and Gamma Lyra lies the beautiful Ring Nebula. It is the 57th
object in the Messier Catalogue and so is also called M57. Such objects are
called planetary nebulae as in a telescope they show a disc, rather like a
planet. But in fact they are the remnants of stars, similar to our Sun, that
have come to the end of their life and have blown off a shell of dust and gas
around them. The Ring Nebula looks like a greenish smoke ring in a small
telescope, but is not as impressive as it is shown in photographs in which
you can also see the faint central "white dwarf" star which is the core of the
original star which has collapsed down to about the size of the Earth. Still
very hot this shines with a blue-white colour, but is cooling down and will
eventually become dark and invisible .
M56 is an 8th magnitude Globular Cluster visible in binoculars roughly half
way between Alberio (the head of the Swan) and Gamma Lyrae. It is 33,000
light years away and has a diameter of about 60 light years. It was first seen
by Charles Messier in 1779 and became the 56th entry into his catalogue.
16
17
18
19
The Sky Looking North at Midnight mid-June 2015
The Sky Looking Overhead at Midnight mid-June 2015
20
21
The Sky Looking West at Midnight mid-June 2015
The Sky Looking East at Midnight mid-June 2015
Messier of the Month—M87
The Sky Looking South at Midnight mid-June 2015
Messier 87 - M87 - Elliptical Galaxy in Virgo
M87 is a supergiant elliptical galaxy that's a prominent member of the Virgo
cluster of galaxies. It's one of the largest and most luminous galaxies known
and a strong source of radiation, particularly radio and X-ray emissions. At
the centre of M87 is a supermassive black hole with a jet of extremely energetic plasma extending outwards for at least 5000 light-years. The galaxy is
therefore an interesting object for both professional and amateur astronomers alike.
With an apparent magnitude of +8.6, M87 is the second brightest of the Virgo cluster galaxies; only M49 at mag. +8.4 is brighter. On dark moonless
nights it's visible with 7x50 or 10x50 binoculars, appearing as a faint hazy
patch of light. The galaxy was one of eight discovered by Charles Messier on
March 18, 1781. On this day he also re-discovered fine globular cluster M92.
M87 lies at the heart of the Virgo cluster. It can be found by imagining a line
connecting Denebola (β Leo - mag. +2.1) with Vindemiatrix (ε Vir - mag.
+2.8). Just over half way along this line is M87. Faint elliptical galaxy M89 is
positioned just over a degree east of M87 with galaxy pair M84/M86 located
1.5 degrees northwest of M87.
Through a 80mm (3.1-inch) scope M87 appears as a fuzzy elliptical ball of
light that's brighter towards the centre. Even with larger scopes the galaxy
remains essentially featureless although much easier to detect. It has no
distinctive dust lanes and diminishes in luminosity with distance from the
centre. The jet is far too faint to be observed with most amateur scopes,
although it has been reportedly observed with extremely large amateur
scopes under excellent conditions. It is much easier to image or photograph.
M87 spans 8.3 x 6.6 arc minutes of apparent sky. It's located 53.5 million
light-years distant, which corresponds to a spatial diameter of 130,000 light
years and is estimated to contain a trillion stars.
22
23
www.freestarcharts.com
Double Star of the Month—ε Lyr
Star of the Month - Ras Algethi
Epsilon Lyrae (ε Lyr) - The Double Double
Red Giant Star: Alpha Herculis or Ras Algethi
Of all multiple star systems consisting of at least three stars, perhaps the
finest and most celebrated of all is Epsilon (ε Lyr) Lyrae. Epsilon Lyrae is located in the constellation of Lyra close to the bright star Vega (mag. 0.0). For
northern hemisphere observers Vega dazzles brilliantly during the summer
months, appearing high in the sky during the warm nights. Positioned just
over 1.5 degrees to the northeast of Vega and shining at magnitude 3.9 is
Epsilon Lyrae. The star at first glance probably won't seem at all remarkable,
but on closer inspection and especially if you have sharp eyesight, you may
notice that Epsilon Lyrae is in fact a double star consisting of two almost
identical white stars. The stars are named Epsilon1 and Epsilon2 Lyrae and
have a separation of 208 arc seconds.
Just to the west of the bright star Vega lies the constellation Hercules, in
which Ras Algethi, the Alpha star, is the fifth brightest. The star is a magnificent red class M (M5) supergiant with a surface temperature of about 3300
degrees Kelvin and magnitude 3.48 as seen from Earth. At a distance of 380
light years, Ras Algethi is 475 times more luminous than the Sun, though in
fact it varies irregularly in its brightness by about a magnitude over periods
of months to years.
Epsilon1 and Epsilon2 are split in 7x35, 10x50 and 20x80 bins without problem. Of the two stars, the northern one is Epsilon1 and the southern one,
Epsilon2. Remarkably, this is not where the story ends as both Epsilon1 and
Epsilon2 themselves are double stars; hence the nickname "The Double Double". However, you won't be able to further split these two stars with binoculars; it requires much higher magnification. A small 70mm to 80mm telescope at about 120x magnification will do the job, if the seeing conditions
are good. In fact, this example is a good test of the seeing conditions. If you
can split Epsilon Lyrae into its four components with a small telescope, then
you're night is off to a good start as the observing conditions are superb. All
four stars appear off white in colour.
The star has varied by almost a magnitude over nearly 14 years of observation, the principal period of 128 or so days—see graph below. The time
scale on the x-axis runs from year 1986 to 2000. The left-hand scale expresses the difference between the apparent visual magnitude of Ras Algethi and
a nearby comparison star.
All four stars are gravitationally bound and it is estimated that the two components of Epsilon1 take 1200 years to complete one orbit compared to 585
years for the stars of Epsilon2. The Epsilon Lyrae system is located 162 lightyears from Earth. In 1985, a fifth component of the system orbiting one of
the Epsilon2 pair was detected by speckle interferometry.
The star has a physical radius of 1.9 Astronomical Units, 400 times that of
the Sun. If placed here, the star would extend well out past the orbit of Mars
and into the inner part of the asteroid belt. Ras Algethi appears to be losing
mass at a rate of about a ten-millionth of a solar mass per year, consistent
with it being a highly distended supergiant. With a birth mass of perhaps 7
or 8 times that of the Sun, the star has probably either finished core helium
fusion or will do so and may die as a relatively massive white dwarf.
24
25
www.freestarcharts.com
www.stars.astro.illinois.edu
Ophiuchid Meteor Shower (20 June)
BAS Open Observing
The Ophiuchid meteor shower will reach its maximum rate of activity on 20
June 2015. Some shooting stars associated with the shower are expected to
be visible each night from 19 May to late July.
Saturday Observing at the Failand Observatory
Members open the Society's Observatory at Failand for
the General Public on many clear Saturday Nights. We
welcome visitors including family, friends, neighbours
with or without telescopes and binoculars etc. No astronomical knowledge or skill is required except interest in
what you may be about to observe! For further information on how to attend, including details and information on where to find us please email:
[email protected] Use the status message on www.bristolastrosoc.org.uk to check if
the session is running.
The maximum rate of meteors expected to be visible from a dark location is
around 5 per hour. The Moon will be 4 days old at the time of peak activity,
and so will present minimal interference.
The radiant of the Ophiuchid meteor shower is at around right ascension
16h50m, declination -20°, as shown in the chart below. At midnight, it appears 18° above the southern horizon from Bristol. All of the meteors will
appear to be travelling directly outward from this point.
The best place to look to see as many meteors as possible is not at the radiant itself, but at any dark patch of sky which is around 90° away from it,
since it is at a distance of around 90° from the radiant that meteors will typically appear at their brightest.
Date
6 June
BAS Members
No public observing
13 June
No public observing (Festival of Nature)
20 June
No public observing
27 June
John Willis
Jane Clark
Nigel Kirkland
Observing at Tyntesfield & Other Events
The Bristol Astronomical Society provides equipment and expertise for Star
Parties and Solar Observing run by The National Trust, Tyntesfield. These
take place (weather permitting) regularly during the year.
Bristol Astronomical Society also regularly organises other star gazing events
around the City.
Check www.bristolastrosoc.org.uk for more details and how to attend.
26
www.www.in-the-sky.org
27
Society News
Programme of Events
(At Bristol Grammar School, University Road BS8 1SR)
5th June Prof David Southwood
12th June
Dr. Haley Gomez
The Cassini-Huygens Mission
New insights into the dusty universe
As normal over the summer period, from 12th June to 25th September
2015, meetings will be held once a fortnight and will be talks given by BAS
members. Please check the Google calendar before each meeting for
more details on the night.
Dr Rodney Hillier
Members of the BAS were very saddened to hear of the death of Dr Rodney
Hillier on 5th May 2015. Rodney had been a long-standing Vice-President of
the Society and for many years had given regular lectures to Society members on current research topics in astronomy. In addition to his work for
the BAS, Rodney was also active in supporting many other astronomical societies and organisations, including the Cotswold Astronomical Society and
the William Herschel Museum in Bath.
In April, some members of the BAS held a lunch in appreciation for Rodney’s
valuable work in astronomy and the Society,
which included a visit to the Failand Observatory,
shown in the photograph here.
The Society plans further events to remember
Rodney’s work and contribution, details of which
will appear on our website in the future.
Bristol Astronomical Society
Registered Charity No. 299649
www.bristolastrosoc.org.uk
28