Download The Night Sky May 2016 - Bridgend Astronomical Society

BRIDGEND ASTRONOMICAL SOCIETY NEWSLETTER
FUTURE TALKS
MAY 13 The Gaia Satellite by Dr Sarah Roberts of the University of South Wales
The Great Quasar Debate 1963-(1969)-1985 by Professor Mike Edmunds of
Cardiff University.
SEPT 9
OCT 14 “Telescopes through the Ages” by Dr Chris North of Cardiff University
NOV 11 "Overthrowing Newton -Proving Einstein right" by Dr Rhodri Evans of Cardiff
University.
DEC 9 “Star Men” Full length movie starring four “retired” British astronomers
JAN 13th “The Moons of the Solar System” by Marc Delaney of Cardiff AS
FEB "Neutron Stars and other extreme matter" by Professor Chris Allton of Swansea
University
MAR 10 “What has astronomy ever done for us?” by Dr Fraser Lewis of Cardiff
University
APR 14th TBA
MAY 12th AGM
The Night Sky May 2016
Compiled by Ian Morison
Two great highlights this month: the transit of Mercury on
the 9th and the opposition and closest approach of Mars on
the 22nd and 29th of May.
Image of the Month
Hubble Image of the Bubble nebula NGC 7635
Image:AURA/STScI, ESA, NASA, Hubble Heritage Team
The seven light-year diameter Bubble Nebula is the result of a fierce solar wind ejected from the
O-type star above and to the left of its centre. The star is several hundred thousand times more
luminous that our Sun and 45 times more massive.
The nebula lies some 7,100 light years
distant in the Constellation Cassiopeia.
This image was taken to commemorate the 26th
anniversary of Hubble's launch in 1990.
Highlights of the Month
May 9th - the Transit of Mercury across the face of the Sun
The transit of Mercury
Image:Eclipsophile: Jay Anderson and Jennifer West.
On May the 9th, we will, if clear in the UK, be able to witness the complete passage of
Mercury's disc across the face of the Sun. The transit begins soon after 11 hours UT,
the midpoint of the transit is at 14:58 UT and Mercury leaves the Sun's disk at 18:42 UT
- a total time of 7 and a half hours. This is Mercury' first transit since 2006 and the
next will occur on November 11th 2019 but will not be so easily visible from the
UK. These are three of the 13 or 14 Mercury transits that occur each century.
Mercury's black disk will appear only 10 arc seconds across so binoculars or a telescope
will be needed to observe the transit. If direct viewing is to be made a suitable solar
filter must be placed in front of the objective(s). Filters made using Baader Solar
Film are probably best. Alternatively, an image of the Sun can be projected onto white
card using a small telescope or half binocular. An all metal eyepiece is needed to
prevent heat damage and its probably best to limit the aperture to ~1 inch across using
a cardboard mask. Always take very great care when viewing the Sun - it is the
only astronomical object that can harm us!
At first glance Mercury's disk might, at just 1/200th of the Sun’s width, appear as a
sunspot, but it will be precisely round, be even darker, will lack a grey penumbra and of course - it will be moving across the Sun' disk. It will be interesting to watch the
ingress and exit of Mercury's disk taking 3 minutes and 12 seconds to do so. Let's hope
for clear skies!
May 22nd to June 8th: Mars at its best for 11 years.
Mars at opposition and closest approach
Image: Stellarium/IM
Mars reaches opposition - that is when the Earth lies between the Sun and Mars and
when it will be approximately due south at midnight (UT) or 1 am (BST) - on the 22nd of
May, so it will be visible for most of the hours of darkness. However, it will actually be
closest to the Earth and so have its greatest angular size of 18.6 arc seconds some 8
days later on the 30th of May. The angular size at closet approach varies due to the
ellipticity of the orbit of Mars (and to a far lesser extent to that of the Earth) and will
reach 26 arc seconds during 25,695 AD. At closest approach in 2003, Mars reached an
angular size of 25.1 arc seconds, its largest angular diameter for 60,000 years. In July
2018 it will reach 24.2 arc seconds across but for both this opposition and that in 2018,
Mars will be very low in the ecliptic and hence at low elevation so that the atmosphere
will limit our views of the red (actually salmon pink) planet. Happily, it will be higher in
the sky at the opposition of 2020.
To find what should be visible at any time, one can use the Sky & Telescope application:
http://is.gd/marsprofiler.
May: Look for the Great Red Spot on Jupiter
Observe the Great Red Spot
Image: NASA
This list gives some of the best late evening times (in UT) during May to observe the
Great Red Spot (which is unusually vivid this year) which should then lie on the central
meridian of the planet.
3rd
00:22
29th 21:45
5th
21:52
31st 23:24
10th 21:01
12th 22:39
17th 21:48
19th 23:27
24th 22:36
May 5th and 6th before dawn: The Eta Aquarid Meteor
Shower
The Eta Aquarid Meteor Shower
Image: Stellarium/IM
The Eta Aquarids are one of the finest meteor showers that can be seen from the
southern hemisphere, but, in the northern hemisphere, may be glimpsed in the predawn sky in the south-east around 90 minutes before dawn. Pleasingly, this year the
peak corresponds to new Moon so there will be no moonlight to hinder our view.
May 7th - one hour before sunrise: Saturn, Mars and
Antares
Saturn and Mars close to Antares
Image: Stellarium/IM
Looking to the South-Southwest in the hours before sunrise, Saturn, above, and Mars, to
the upper right, can be seen close to Antares in Scorpius.
May 7th - after sunset: a very thin waxing crescent Moon
A 1% illuminated crescent Moon
Image: Ian Morison
If clear at sunset, and given a low horizon in the West-Northwest, you may be able to
spot a very thin waxing crescent Moon just 1% illuminated. Binoculars may be needed,
but please do not use them until after the Sun has set. You may be able to observe the
major part of the Moon's surface illuminated by light reflected from Earth - called
Earthshine - as seen in the accompanying image taken by the author at the Isle of White
Star Party.
May 14th and 27th, evening: The Hyginus Rille
Hyginus Rille location: IM.
These evenings, should it be clear, are a superb time to view the Hyginus Rill as it will lie
close to the terminator. For some time a debate raged as to whether the craters on the
Moon were caused by impacts or volcanic activity. We now know that virtually all were
caused by impact, but it is thought that the Hyginus crater that lies at the centre of the
Hyginus Rille may well be volcanic in origin. It is an 11 km wide rimless pit - in contast
to impact craters which have raised rims - and its close association with the rille of the
same name associates it with internal lunar events. It can quite easily be seen to be
surrounded by dark material. It is thought that an explosive release of dust and gas
created a vacant space below so that the overlying surface collapsed into it so forming
the crater.
Hyginus Crater and Rille
M109 imaged with the Faulkes Telescope
Messier
Image:
Faulkes Telescope North.
Daniel
109
Duggan
The
Barred
Spiral
galaxy
M109,
imaged
by
Daniel
Duggan.
This image was taken using the Faulkes Telescope North by Daniel Duggan - for some
time a member of the Faulkes telescope team. It shows the barred spiral galaxy M109
that lies at a distance of 83 million light years in the constellation of Ursa Major. It is
the brightest galaxy in the Ursa Major group of some 50 galaxies. Our own Milky Way
galaxy is now thought to be a barred spiral like M109.
Learn more about the Faulkes Telescopes and how schools can use them: Faulkes
Telescope"
Observe the International Space Station
The International Space Station and Jules Verne passing behind the Lovell Telescope on April 1st
2008.
Image by Andrew Greenwood
Use the link below to find when the space station will be visible in the next few days. In
general, the space station can be seen either in the hour or so before dawn or the hour
or so after sunset - this is because it is dark and yet the Sun is not too far below the
horizon so that it can light up the space station. As the orbit only just gets up the the
latitude of the UK it will usually be seen to the south, and is only visible for a minute or
so at each sighting. Note that as it is in low-earth orbit the sighting details vary quite
considerably across the UK. The NASA website linked to below gives details for several
cities in the UK. (Across the world too for foreign visitors to this web page.)
Note: I observed the ISS three times recently and was amazed as to how bright it has
become.
Find details of sighting possibilities from your location from: Location Index
See where the space station is now: Current Position
The Moon
new moon
first quarter
full moon
May 6th
May 13th
May 21st
The Planets
Jupiter
Jupiter is now a little past its best, but still stands out high in the South at
nightfall. Its brightness falls slightly from magnitude -2.3 to -2.1 whilst its angular size
drops from 41 to 37 arc seconds during the month. Jupiter spends the month below the
hindquarters of Leo, halting its retrograde motion westwards across the sky on May
9th. Jupiter sets around 4 am as May begins but by 2 am by month's end. With a
small telescope one should be easily able to see the equatorial bands in the atmosphere,
sometimes the Great Red Spot and up to four of the Gallilean moons as they weave their
way around it.
Saturn
Saturn rises in the late evening about 30 minutes after Mars as May begins.
Its
brightness increases slightly from +0.2 to 0.0 magnitudes during the month whilst its
angular size grows to 18.4 arc seconds. Saturn's rings are tilted by 26 degrees from
the line of sight - almost as open as they ever get - and span 42 arc seconds. It is
moving towards opposition on the night of June 2nd. Saturn forms a triangle with Mars
and Antares throughout the month, separated from Mars by 8 degrees as May begins
and by 15 degrees at month's end. As Saturn moves slowly across the heavens, it
stays at a near constant distance from Antares.
Mercury
Mercury. The top highlight this month is Mercury's transit across the face of the Sun on
May the 9th, but otherwise it will be too dim and low above the horizon to be seen.
Mars
Mars reaches its closest point to the Earth on May 29th for 11 years with an angular size
then of 18.6 arc seconds. It starts the month with an angular size of 16 arc seconds
and a magnitude of -1.5, brightening until it reaches its peak of -2.1 magnitudes so
equalling the magnitude of Jupiter for a few days.
Mars, in retrograde motion
westwards across the sky, lies low in Scorpius beginning the month 5 degrees north of
Antares and passing between Beta and Delta Scorpii on the 19th as it moves towards
Libra.
Venus
Venus is heading towards superior conjunction with the Sun (on the far side) on June
2nd and is not visible during May.
The Stars
The evening May Sky
The May Sky in the south - after sunset.
This map shows the constellations seen in the south after sunset.
The constellation Gemini is now setting towards the south-west and Leo holds pride
(sic) of place in the south with its bright star Regulus. Between Gemini and Leo
lies Cancer - which is well worth observing with binoculars to see the Beehive Cluster at
its heart. Below Gemini is the tiny constellation Canis Minor whose only bright star is
Procyon. Rising in the south-east is the constellation Virgo whose brightest star is
Spica. Though Virgo has few bright stars it is in the direction of a great cluster of
galaxies - the Virgo Cluster - which lies at the centre of the supercluster of which our
local group of galaxies is an outlying member.
High overhead in the north is the
constellation Ursa Major which also contains many interesting objects.
The constellation Gemini
Gemini
Gemini - The Twins - lies up and to the left of Orion and is in the south-west during early
evenings this month. It contains two bright stars Castor and Pollux of 1.9 and 1.1
magnitudes respectively. Castor is a close double having a separation of ~ 3.6 arc
seconds making it a fine test of the quality of a small telescope - providing the
atmospheric seeing is good! In fact the Castor system has 6 stars - each of the two seen
in the telescope is a double star, and there is a third, 9th magnitude, companion star 73
arc seconds away which is also a double star! Pollux is a red giant star of spectral class
K0. The planet Pluto was discovered close to delta Geminorum by Clyde Tombaugh in
1930. The variable star shown to the lower right of delta Geminorum is a Cepheid
variable, changing its brightness from 3.6 to 4.2 magnitudes with a period of 10.15 days
M35 and NGC 2158
This wonderful image was taken by Fritz Benedict and David Chappell using a 30" telescope at
McDonald Observatory. Randy Whited combined the three colour CCD images to make the picture
M35 is an open star cluster comprising several hundred stars around a hundred of which
are brighter than magnitude 13 and so will be seen under dark skies with a relativly
small telescope. It is easily spotted with binoculars close to the "foot" of the upper right
twin. A small telescope at low power using a wide field eyepiece will show it at its best.
Those using larger telescopes - say 8 to 10 inches - will spot a smaller compact cluster
NGC 2158 close by. NGC 2158 is four times more distant that M35 and ten times older,
so the hotter blue stars will have reached the end of their lives leaving only the longerlived yellow stars like our Sun to dominate its light.
The Eskimo Nebula, NGC2392, Hubble Space Telescope
To the lower right of the constellation lies the Planetary Nebula NGC2392. As the Hubble
Space Telescope image shows, it resembles a head surrounded by the fur collar of a
parka hood - hence its other name The Eskimo Nebula. The white dwarf remnant is
seen at the centre of the "head". The Nebula was discovered by William Herschel in
1787. It lies about 5000 light years away from us.
The constellation Leo
Leo
The constellation Leo is now in the south-eastern sky in the evening. One of the few
constellations that genuinely resembles its name, it looks likes one of the Lions in
Trafalgar Square, with its mane and head forming an arc (called the Sickle) to the upper
right, with Regulus in the position of its right knee. Regulus is a blue-white star, five
times bigger than the sun at a distance of 90 light years. It shines at magnitude 1.4.
Algieba, which forms the base of the neck, is the second brightest star in Leo at
magnitude 1.9. With a telescope it resolves into one of the most magnificent double
stars in the sky - a pair of golden yellow stars! They orbit their common centre of gravity
every 600 years. This lovely pair of orange giants are 170 light years away.
Leo also hosts two pairs of Messier galaxies which lie beneath its belly. The first pair lie
about 9 degrees to the west of Regulus and comprise M95 (to the east) and M96. They
are almost exactly at the same declination as Regulus so, using an equatorial mount,
centre on Regulus, lock the declination axis and sweep towards the west 9 degrees. They
are both close to 9th magnitude and may be seen together with a telescope at low power
or individually at higher powers. M65 is a type Sa spiral lying at a distance of 35 millin
klight years and M66, considerably bigger than M65, is of type Sb. Type Sa spirals have
large nuclei and very tightly wound spiral arms whilst as one moves through type Sb to
Sc, the nucleus becomes smaller and the arms more open.
The galaxies M65 and M66
M65 - Type Sa spiral, 9.3 magnitude M66 - Type Sb spiral, 8.9 magnitude
The second pair of galaxies, M95 and M96, lie a further 7 degrees to the west between
the stars Upsilon and Iota Leonis. M95 is a barred spiral of type SBb. It lies at a distance
of 38 million light years and is magnitude 9.7. M96, a type Sa galaxy, is slightly further
away at 41 million light years, but a little brighter with a magnitude of 9.2. Both are
members of the Leo I group of galaxies and are visible together with a telescope at low
power.
The galaxies M95 and M96
M95 - Type SBb spiral, 9.7 magnitude M96 - Type Sa spiral, 9.2 magnitude
There is a further ~9th magnitude galaxy in Leo which, surprisingly, is in neither the
Messier or Caldwell catalogues. It lies a little below lambda Leonis and was discovered by
William Herschel. No 2903 in the New General Catalogue, it is a beautiful type Sb galaxy
which is seen at somewhat of an oblique angle. It lies at a distance of 20.5 million light
years.
The 8.9th magnitude, type Sb, Galaxy NGC2903
The constellation Virgo
Virgo
Virgo, rising in the east in late evening this month, is not one of the most prominent
constellations, containing only one bright star, Spica, but is one of the largest and is very
rewarding for those with "rich field" telescopes capable of seeing the many galaxies that
lie within its boundaries. Spica is, in fact, an exceedingly close double star with the two B
type stars orbiting each other every 4 days. Their total luminosity is 2000 times that of
our Sun. In the upper right hand quadrant of Virgo lies the centre of the Virgo Cluster of
galaxies. There are 13 galaxies in the Messier catalogue in this region, all of which can
be seen with a small telescope. The brightest is the giant elliptical galaxy, M87, with a
jet extending from its centre where there is almost certainly a massive black hole into
which dust and gas are falling. This releases great amounts of energy which powers
particles to reach speeds close to the speed of light forming the jet we see. M87 is also
called VIRGO A as it is a very strong radio source.
The Giant Elliptical Galaxy M87 HST image showing the jet
Below Porrima and to the right of Spica lies M104, an 8th magnitude spiral galaxy about
30 million light years away from us. Its spiral arms are edge on to us so in a small
telescope it appears as an elliptical galaxy. It is also known as the Sombrero Galaxy as it
looks like a wide brimmed hat in long exposure photographs.
M104 - The Sombrero Galaxy
The constellation Ursa Major
Ursa Major
The stars of the Plough, shown linked by the thicker lines in the chart above, form one
of the most recognised star patterns in the sky. Also called the Big Dipper, after the
soup ladles used by farmer's wives in America to serve soup to the farm workers at
lunchtime, it forms part of the Great Bear constellation - not quite so easy to make out!
The stars Merak and Dubhe form the pointers which will lead you to the Pole Star, and
hence find North. The stars Alcor and Mizar form a naked eye double which repays
observation in a small telescope as Mizar is then shown to be an easily resolved double
star. A fainter reddish star forms a triangle with Alcor and Mizar.
Ursa Major contains many interesting "deep sky" objects. The brightest, listed in
Messier's Catalogue, are shown on the chart, but there are many fainter galaxies in the
region too. In the upper right of the constellation are a pair of interacting
galaxies M81 and M82 shown in the image below. M82 is undergoing a major burst of
star formation and hence called a "starburst galaxy". They can be seen together using a
low power eyepiece on a small telescope.
M81 and M82
Another, and very beautiful, galaxy is M101 which looks rather like a pinwheel firework,
hence its other name the Pinwheel Galaxy. It was discovered in1781 and was a late
entry to Messier's catalogue of nebulous objects. It is a type Sc spiral galaxy seen face
on which is at a distance of about 24 million light years. Type Sc galaxies have a
relatively small nucleus and open spiral arms. With an overall diameter of 170,000 light
it is one of the largest spirals known (the Milky Way has a diameter of ~ 130,000 light
years).
M101 - The Ursa Major Pinwheel Galaxy
Though just outside the constellation boundary, M51 lies close to Alkaid, the leftmost
star of the Plough. Also called the Whirlpool Galaxy it is being deformed by the
passage of the smaller galaxy on the left. This is now gravitationally captured by M51
and the two will eventually merge. M51 lies at a distance of about 37 million light years
and was the first galaxy in which spiral arms were seen. It was discovered by Charles
Messier in 1773 and the spiral structure was observed by Lord Rosse in 1845 using the
72" reflector at Birr Castle in Ireland - for many years the largest telescope in the world.
M51 - The Whirlpool Galaxy
Lying close to Merak is the planetary nebula M97 which is usually called the Owl Nebula
due to its resemblance to an owl's face with two large eyes. It was first called this by
Lord Rosse who drew it in 1848 - as shown in the image below right. Planetary nebulae
ar the remnants of stars similar in size to our Sun. When all possible nuclear fusion
processes are complete, the central core collapses down into a "white dwarf" star and
the outer parts of the star are blown off to form the surrounding nebula.
M97 - The Owl Planetary Nebula Lord Rosse's 1848 drawing of the Owl Nebula