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Transcript
Bristol Astronomical Society Information Leaflet
November 2015
BAS Visit to the Norman Lockyer Observatory, October 2015
1
Observing Calendar November 2015
Observing Calendar November 2015
2
3
The Sun
The Moon
Sun’s Position at Midday 15th November 2015
Nov 25th - Full Moon
close to Hyades Cluster
This evening, the full
moon will be seen just to
the right of the Hyades
Cluster in Taurus. Lying
half way towards the cluster is the red-giant star
Aldebaran.
Solar Events for 2015
4
5
www.stardate.org
The Moon
The Planets
November 1st at 00:00
November 15th at 00:00
November 30th at 00:00
Why not use this map of the full Moon to learn the locations of the Moon's Mare.
The major eleven Mare are shown above - you can see
some of them with your unaided eye and binoculars will
enable you to spot them all.
6
www.jb.man.ac.uk
7
www.heavens-above.com
The Planets
The Planets
Mercury
Jupiter
Mercury reaches superior conjunction (that is, on the far side of the Sun) on
November 17th and will therefore not be seen for much of the month.
Jupiter is now a wonderful morning object, rising soon after midnight by the
last week of November. Jupiter starts the month shining at magnitude -1.8
with an angular diameter of 33 arc seconds. During the month, these increase to -2.0 and 35.5 respectively.
It might just be picked up using binoculars low in the east about 20 minutes
before sunrise in the first few days of the month.
Venus
Venus, rising at ~03:30, starts the month dominating the eastern sky before
dawn in a close grouping with both Jupiter and Mars. Its magnitude drops
only slightly from -4.4 to -4.2 during the month whilst its angular diameter
drops from 22.7 to 17.6 arc seconds.
It lies in Leo, 8 degrees over to the right of Denebola and is gradually moving down towards Virgo before it starts its retrograde motion in January. With a small telescope, early risers should be able to see the equatorial bands in the atmosphere and the four Gallilean moons as they weave
their way around it - see image below Jupiter’s major atmospheric features.
As the illuminated disk increases from 54 to 63% at the same time, the observed magnitude stays almost constant. Venus is rapidly moving closer to
the Sun and will have dropped by around 30 degrees towards the horizon
so will have become less prominent by the end of the month.
Moving from Leo into Virgo, it passes 0.4 degrees from magnitude 3.6 Beta
Virginis on the 13th and less than 0.2 degrees from Eta Virginis on the 21st.
Mars
Mars rises about 03:30 as the month begins shining at magnitude
+1.7. This increases to magnitude +1.5 as the month progresses with its
angular diameter increasing from 4.2 to 4.7 arc seconds. This is still too
small for any details to be seen on its salmon-pink surface.
At November’s start it will lie close to both Jupiter and Venus making a
wonderful grouping in the sky. By month's end, Mars will be about 20 degrees to the lower left of Jupiter and 14 degrees to the upper right of Venus. It starts the month in Leo moving down into Virgo later and makes a
close approach to Eta Virginis on the 21st.
8
Saturn
Saturn passes behind the Sun on the 29th of November. It might just be
seen using binoculars at the very beginning of the month just a few degrees above the southwestern horizon 45 minutes after sunset but, really,
we will have to wait for a while yet to see it in the pre-dawn sky.
9
The Planets
The Sky This Month
Nov 3rd - before sunrise: Venus and Mars under a degree apart
Before dawn on the 3rd, brilliant Venus shining at magnitude -4.5 will be
very close to Mars at magnitude +1.7. Jupiter will lie ~7 degrees to their
upper right.
Nov 7th - before sunrise : a thin crescent Moon joins the morning planets
An excellent imaging opportunity arises before dawn on the 7th as a thin
crescent Moon lies close to Venus and Mars with Jupiter some 9 degrees to
their upper right.
Nov 25th to 30th - 1 hour before sunrise: Jupiter rises higher in the sky.
In the last week of November, Jupiter, rising 40 minutes after midnight, has
reached an elevation of 20 degrees or more for 2 hours of astronomically
dark sky. Then will be the time to start seriously observing and imaging the
planet.
This image of Jupiter was taken by the Hubble Space Telescope in January
2015. It shows that the Great Red Spot is shrinking, though it is still bigger
than the Earth. Down to its lower right is Oval BA, otherwise known as Red
Spot Junior.
Planetary info source: www.jb.man.ac.uk & www.freestarcharts.com
10
This map shows the constellations seen towards the south in early evening.
Moving over to the west as the night progresses 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". East of Cygnus is the great square of Pegasus - adjacent to Andromeda in which lies M31. To the north lies "w" shaped Cassiopeia and Perseus. The constellation Taurus, with its two lovely clusters, the
Hyades and Pleiades is rising in the east during the late evening.
11
‘Sky This Month’ : www.jb.man.ac.uk
The Sky This Month - Cetus
The Sky This Month - Cetus
Messier 77 (NGC 1068)
The constellation was named after Cetus, the sea monster from the Greek
myth about Andromeda, the princess sacrificed to the monster as punishment for her mother Cassiopeia’s vanity and boastfulness.
The constellation Cetus lies in the region of the sky called the Water, along
with several other constellations with names evocative of water: Eridanus
(the river), Aquarius (water bearer) and Pisces (the fish). Due to its shape,
Cetus is sometimes referred to as the ‘Whale’.
Cetus is home to the barred spiral galaxy Messier 77 and several well-known
stars: Deneb Kaitos (Beta Ceti), Menkar (Alpha Ceti), Tau Ceti and the famous variable star Mira (Omicron Ceti) - see page 25. 14 stars within the
constellation of Cetus are known to have planetary systems.
Deneb Kaitos (Diphda) – β Ceti (Beta Ceti)
Beta Ceti is the brightest star in the constellation. It has an apparent visual
magnitude of 2.04 and is approximately 96.3 LY distant. An orange giant
belonging to the spectral type K0 III, Beta Ceti has left the main sequence
stage of evolution and is on its way to becoming a red giant.
With a surface temperature of 4,800 K, the star is slightly cooler than the
Sun. Beta Ceti is sometimes known by its traditional names, Deneb Kaitos
and Diphda.Alrescha.
Menkar (Menkab) – α Ceti (Alpha Ceti)
Alpha Ceti is a very old red giant star, approximately 249 LY distant. The star
will eventually eject its outer layers to form a planetary nebula, leaving a
large white dwarf remnant. It has an apparent visual magnitude of 2.54.
Alpha Ceti is often used in works of science fiction, most notably in Star
Trek: The Original Series. Alpha Ceti V was the planet on which Khan and his
crew were exiled.
12
www.constellation-guide.com
τ Ceti (Tau Ceti)
Tau Ceti is a cool class G (G8.5) dwarf with an apparent magnitude of 3.5. It
is one of the nearest stars to our solar system, lying only 11.9 LY away. It has
a mass only about 78% that of the Sun and is one of the very few stars less
massive than the Sun that are visible to the naked eye. It is a metal-deficient
star with a luminosity equal to only 55% of the Sun’s luminosity.
Messier 77 (M77, NGC 1068)
M31 77 is a barred spiral galaxy in Cetus, approximately 47 million LY
Messier
distant and 170,000 LY in diameter. It has an apparent visual magnitude of
9.6. It is one of the largest galaxies listed in Messier’s catalogue. The galaxy
can be easily found 0.7 degrees east-southeast from Delta Ceti, a fourth
magnitude star. The galaxy has an Active Galactic Nucleus (AGN) which is
blocked from view by intergalactic dust.
13
Observing Notes
Planetary
Positions
15 November
1 November 23:00
15 November 22:00
30 November 21:00
14
15
The Sky This Month - Aries
The Sky This Month - Aries
Mesarthim – γ Arietis (Gamma Arietis)
Mesarthim, Gamma Arietis, is a triple star system which includes a binary
star system composed of two white A-type main sequence stars with apparent magnitudes of 4.75 and 4.83, lying 7.7 arc-seconds apart, and a third
component, a magnitude 9.6 K-type star that lies 221 arc-seconds away. The
system is approximately 160 LY distant.
1156
772
The brightest component is classified as an Alpha-2 Canum Venaticorum
type variable star, a chemically peculiar main sequence star with strong
magnetic fields and strong strontium, chromium, or silicon spectral lines.
The star’s brightness varies by 0.04 magnitudes with a period of 2.61 days.
NGC 772
The constellation Aries has five stars with known planets, contains no
Messier objects but does contains several notable deep sky objects, among
them the unbarred spiral galaxy NGC 772 and the dwarf irregular galaxy
NGC 1156. The brightest star in Aries is Hamal, Alpha Arietis.
Hamal – α Arietis (Alpha Arietis)
Hamal is the brightest star in the constellation Aries and is a K-type orange
giant about twice as massive as the Sun, with an apparent visual magnitude
varying
M31 between 1.98 and 2.04. The star is 66 LY distant.
Sheratan – β Arietis (Beta Arietis)
Sheratan, Beta Arietis, is a white main sequence star and a spectroscopic
binary, 59.6 LY distant. The companion is suspected to be a G class star.
Sheratan has a visual magnitude of 2.64.
16
NGC 772, or Arp 78, is an unbarred spiral
galaxy in Aries. It is located about 130 LY
from Earth and has an apparent magnitude
of 11.3. The galaxy lies southeast of Beta
Arietis.
Two supernovae were discovered in the galaxy, SN 2003 hl and SN 2993 iq. NGC 772 has
a satellite galaxy, NGC 770. NGC 770 is an
elliptical galaxy with an apparent magnitude
of 14.2.
M311156
NGC
NGC 1156 is a dwarf irregular galaxy with an
apparent magnitude of 12.3 It is classified as
a Magellanic type irregular galaxy. The galaxy’s core is larger than average and there
are regions of contra-rotating gas inside it,
17
www.constellation-guide.com
18
19
The Sky Looking North at 22:00 mid-November 2015
The Sky Looking Overhead at 22:00 mid-November 2015
20
21
The Sky Looking West at 22:00 mid-November 2015
The Sky Looking East at 22:00 mid-November 2015
The Sky Looking South at 22:00 mid-November 2015
Messier of the Month - M45 - Pleiades
Sterope
Taygeta
Maia
Celaeno
Pleione
Alcyone
Electra
Atlas
Merope
M45, also known as the Pleiades or Seven Sisters, is a bright open star cluster located in the constellation Taurus, the Bull. M45 has an apparent magnitude of 1.6 and lies at an average distance of 444 LY from Earth.
The Pleiades cluster contains a number of hot, blue, extremely luminous Btype stars and is one our nearest star clusters. It is the easiest object of its
kind to see with the naked eye. M45 has a core radius of 8 LY and its total
radius extends to about 43 LY. The cluster contains more than 1,000 members, but only a handful of these stars are visible to the naked eye.
Up to 14 stars are visible without binoculars in good conditions, with clear
skies and no light pollution. The best way to see M45 is through binoculars
and small or wide field telescopes. Higher magnification is only recommended for studying individual stars. When the cluster is high in the sky, it can
easily be located by following the line formed by the three bright stars that
form Orion’s Belt - M45 lies to the northwest of Orion.
22
23
www.messier-objects.com
Messier of the Month - M45 (Continued)
Messier of the Month - M45 (Continued)
The stars in the Pleiades cluster have formed in the last 100 million years
and they will stay gravitationally bound to each other for another ~250 million years before the cluster disperses as a result of interactions with other
objects in the neighbourhood. By that point, the cluster will have moved
from Taurus to Orion.
4) Maia - 20 Tauri - Mag 3.86: Maia, the 4th brightest star in the cluster, is a
blue giant and a Hg-Mn star, a chemically peculiar star with a strong spectral
absorption line resulting from ionized Hg. The star is 850 times more luminous than the Sun, 6 times as large and over 5 times as massive. Maia is the
central star of the Maia Nebula, a bright reflection nebula in the cluster.
M45 has a faint reflection nebula surrounding it, named Maia Nebula, after
one of the cluster’s brightest stars. The nebula is not related to the cluster’s
formation, but is merely a dust cloud through which the stars are passing.
5) Merope - 23 Tauri - Mag 4.17: Merope is also associated with a reflection nebula - the Merope Nebula, a
diffuse reflection nebula the M45 cluster is currently
passing through. The star is 630 times more luminous
than the Sun and has a mass about 4.5 times solar. Merope’s radius is more
than 4 times greater than the Sun’s.
The 9 brightest stars are all luminous, hot, blue B-type stars:
1) Alcyone - Eta Tauri (25 Tauri) - Mag 2.86: Alcyone is an eclipsing binary
system. The primary component is a a blue-white
giant 8.2 times larger than the Sun, 6 times more
massive, and 2,400 times more luminous. The star
has a very high rotational velocity, 215 km/s, and as
a result it has a circumstellar disk of gas around the
equator. The second component is separated from
the primary by 0.031 arc-seconds.
2) Atlas - 27 Tauri - Mag 3.62: Atlas is a triple star
system consisting of a spectroscopic binary star with an orbital period of
1,250 days. The two stars are a blue white giant with a visual magnitude of
4.1 and a companion with a magnitude of 5.6. The binary system has a fainter, magnitude 6.8 companion located at a separation of 0.4 arc-seconds.
7) Pleione – 28 Tauri - Mag 5.09: Pleione is 190 times more luminous than
the Sun and spins close to its breakup velocity, at 329 km/s. It is classified as
a Gamma Cassiopeiae type variable and its brightness varies from magnitude
4.8 to 5.5. With a radius 3.2 times solar and a mass 3.4 times solar, Pleione is
significantly smaller than the other bright stars in the cluster. It is a main
sequence dwarf with a surface temperature of 12,000 K.
8) Celaeno – 16 Tauri - Mag 5.44: Celaeno is 4.4 times larger than the Sun
and 9 to 10 times more massive. The star rapidly spins, with a projected rotational velocity of 185 km/s.
3) Electra - 17 Tauri - Mag 3.7: Electra is another
blue-white giant and has a projected rotational velocity of 181 km/s at the equator. As a result, Electra
is flattened at the poles and does not have a uniform
surface gravity or temperature. This is an example of
an effect known as gravity darkening. It occurs as a
result of a variation of radiation by latitude.
24
6) Taygeta - 19 Tauri - Mag 4.29: Taygeta is a triple star system which has a
blue-white subgiant for a primary component. The star is a spectroscopic
binary consisting of two stars with visual magnitudes of 4.6 and 6.1, separated by 0.012 arc seconds. The two stars complete an orbit every 1,313 days.
They have an 8th magnitude companion separated by 69 arc seconds.
9) Sterope – 21 & 22 Tauri - Mag 5.64 & 6.41: The name Sterope (or Asterope) is shared by 21 Tauri and 22 Tauri, separated by 0.047 degrees. 21
Tauri is a blue B-type main sequence star with a visual magnitude of 5.76
and 22 Tauri is a white main sequence dwarf with a magnitude of 6.43.
www.messier-objects.com
25
www.messier-objects.com
Double (& Variable) Star - Mira
Mira – ο Ceti (Omicron Ceti)
BAS Open Observing
Saturday Observing at the Failand Observatory
Omicron Ceti, better known as Mira in the constellation Cetus, is a binary
star consisting of a red giant and a companion star. The system is approximately 400 light years distant. See page 13 for star map and location.
Mira A, a red giant belonging to the spectral type M7 IIIe, is an oscillating
variable star that serves as a prototype for an entire class of variables, the
Mira variables. There are between 6,000 to 7,000 known stars belonging to
this group. They are all red giants whose surfaces oscillate in such a way as
to cause variations in brightness over periods ranging from 80 to 1,000 days.
Mira was the first non-supernova variable star discovered, and is believed to
be about six billion years old.
The companion star, Mira B, is a high temperature white dwarf that is accreting mass from the red giant. The two form a symbiotic pair, the closest
one of its kind to the Sun.
Mira is the brightest periodic variable star that cannot be seen by the naked
eye during a part of its cycle. It has a period of 332 days. Its variability was
first documented by the German astronomer David Fabricius in 1596. Fabricius believed it was a nova until he saw the star again in 1609.
The star is shedding a trail of material from its outer envelope. NASA’s Galaxy Evolution Explorer space telescope has revealed a tail 13 light years in
length, trailing after Mira.
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.
See the ‘Monthly Observing Calendar’ on page 3 for the month’s scheduled
public observing dates and volunteers.
During October 2015 two public observing sessions were held, on the 24th
and 31st, with total of about 45 members and visitors attending.
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
27
Society News
Programme of Events 2015-16
(At Bristol Photographic Society, Station Road, Montpelier, Bristol. BS6 5EE )
6 Nov
Telescope Surgery
13 Nov
Title TBC (Mike Frost)
20 Nov
Members Talk Night
27 Nov
Globular Clusters (Callum Potter)
New Location for BAS Meetings
From 30 October 2015 we will be meeting at a wonderful new venue: Bristol
Photographic Society, Unit 13, Station Road, Montpelier, Bristol, BS6 5EE
(see our website for location and directions).
Bristol Astronomical Society (Registered Charity No. 299649)
www.bristolastrosoc.org.uk
28