West (late Winter) to South East(Spring)
- To see the stars in the Spring Constellations, the Earth’s orbit is in a locations such that night side points away from the Sun, towards the Constellations of Leo and Virgo.
- Because we are both orbiting the sun and rotating as we orbit,
this motion causes stars to rise almost 4 minutes earlier each night. After a
month, they rise and set about two hours earlier than the previous month. Leo will be setting in the West end of May, but it is due South in April. The cardinal direction (West, East,South) shows us the constellations that are prominant in different Seasons.
- In April, the three cardinal directions represent 3 Seasons of the NightSky :
- Winter constellations setting in the West.
- Spring constellations culminating on our Southern meridian
- Summer constellations rising in the East
- Note: Northern constellations, are circumpolar, and continue to appear in the Night Sky all year round
Looking West – Observe the Winter Milky Way
Behold: the brilliance of the bright stars and the Winter Milky Way band in the South West. The collection of stars that we see in the Winter Sky are particularly bright for one of two reasons:
- Proximity (e.g. Sirius (9 light years or Procyon (11 light years))
- Instrinsic Luminousity Betelguese (red supergiant), Rigel(blue-white hot supergiant)) Here we see the bright giant stars of Orion, and with some optical aids, many open Clusters lying in the dusty lanes of the Milky Way Galaxy. Next month around about this time, the Winter Milky Way will be setting earlier: last chance to view some of these objects.
Although naked eye, radio astronomers have gauged the distance to this cluster roughly 440 Light years. See www.astronomy.com/news/2014/08/radio-telescopes-settle-controversy-over-distance-to-pleiades
M1 – The Crab Nebula (M1) – Distance ~6500ly
M 42 – The Trapezium inside the Great Orion Nebula -image courtesy P.Browne 2014
(The Great Orion Nebula (M42) – a Stellar Nursery of young stars within a Molecular Cloud See Stars in the Orion Nebula
Constellation Gemini (the Twins) – distance ~2800, 10,000 ly
At the foot of one of the twins – there is a large, young Open Cluster M35, relatively nearby at 2800 light years distance. In the same line of sight, we see NGC 2158, four times more distant that M35 and much much older – almost a globular cluster … http://apod.nasa.gov/apod/ap021129.html
Open Cluster M35 and more distant compact star cluster NGC 2158 – courtesy P. Browne 2014.
To learn more about star clusters see: Stars and Star Clusters in the in the Milky Way
Taurus: Pleaides (M45), Crab Nebula (M1) Gemini: Open Cluster (M35) Distance Open Cluster (NGC 2158) Orion: Great Orion Nebula (M42) Auriga (Bonus) Open Clusters in Winter Milky way
(Finder Chart Courtesy - freestarcharts.com)
Turning South Observe Naked Eye – M44 Praesepe (the Beehive)
Turning directly to the South, we face the constellation Cancer, one of the 12 Constellations of the Zodiac which runs along the plane of the ecliptic
See Astronomy Motions in the Sky Here we can see the Great Beehive Open Cluster (M44) http://oneminuteastronomer.com/147/m44-beehive-star-cluster
Color in Stars
The Beehive contains a larger star population than most other nearby clusters. Under dark skies the Beehive Cluster looks like a nebulous object to the naked eye; thus it has been known since ancient times. We often find it, rather than the constellation it is found in (Cancer).
From Beehive Cluster in Wikipedia:
The cluster’s age and proper motion coincide with those of the Hyades open cluster, suggesting that both share a similar origin. Both clusters also contain red giants and white dwarfs, which represent later stages of stellar evolution, along with main sequence stars of spectral classes A, F, G, K, and M. Age of the cluster is estimated to 700 million years (when the cluster formed out of proto-stars). The cluster’s distance is often cited to lie between 520-610 light years.
The orange color that we see in some of the stars here may mean that they, like Arcturus, have the spectral type of a red giant of spectral type K0III— that has used up its core hydrogen and moved off the main sequence: https://en.wikipedia.org/wiki/Main_sequence
To understand the importance of observing the different colors or spectral hues – see Stars and Starlight in our Milky Way Galaxy
Cluster Distances and Composition:
We can compare the large, brilliant M44 Open Cluster to the much smaller (and older) M67 Open Cluster also located in the constellation Cancer.
Just inside the left of this ‘wishbone’ asterism of Cancer is the much more distant Open Cluster M67. You will notice the difference!
M67 – Open Cluster – Distance ~ 2700 light years (5x the distance and billions of years old (1000 times older than the young star cluster M44)
Turning our gaze a few degrees East, the Spring Sky announces distant Globular Clusters (10s of 1000s of light years) and nearby Star Clouds in the direction of the North Galactic Pole
Although Coma Berenices is a small constellation it does contains one of the densest concentrations of external galaxies in the sky. However its most outstanding feature is not a galaxy but an extremely large and loose naked eye open cluster called Melotte 111 or the Coma Star Cluster. – Distance ~ 280 light years
Although conspicuous and easily visible to the naked eye the cluster was not included in both the Messier or NGC catalogues due to its loose nature, large apparent size and unproven status as a genuine open cluster. It was only in 1938 that a study of 40 stellar members showed that these stars had a common proper motion through space.M3 lies in the southern part of Canes Venatici, practically on the border with Boötes. It’s located 12 degrees northwest of orange giant star Arcturus (α Boo – mag. -0.05) and about halfway along an imaginary line connecting Arcturus with Cor Caroli (α CVn – mag. +2.9). The area of sky surrounding M3 is rather barren, but when observed through binoculars a number of 6th and 7th magnitude stars are visible along with the cluster itself. One such 6th magnitude star is located just 0.5 degrees southwest of M3.-description courtesy freestarcharts.com
Map of the full sky, showing those stars in nearby open clusters and associations – courtesy Hipparcos measurements of nearby star clusters and associations
Messier Object M3 – Globular Cluster in Canes Venatici. 1/2 million stars in a sphere 200 light years in diameter: Distance ~ 33000 light Years
Globular cluster distribution about the galaxy. – courtesy http://relativity.livingreviews.org/Articles/lrr-2013-4/articlese2.html
M53 – Globular Cluster in Coma Berenices – Distance ~ 66000 light years
Note: Globular clusters are distributed in a halo around our galaxy: Globular clusters are normally associated with a host galaxy and most galaxies, including the Milky Way, are surrounded and penetrated by a globular cluster system
|Galactic Pole||right ascension||declination||constellation|
|north pole (+90° latitude)||12h 49m(12h 51.4m)||+27°.4(+27°.13)||Coma Berenices|
Now our outward gaze is pointing upwards out of the disk of our galaxy towards the North Galactic Pole. This allows us to see further in deep space; first towards the Globular Clusters, like M3 and M53 – massive collections of very old stars that form a halo around the disk of the Milky Way.
Galaxies – Isolated Island Universes and beyond that Galaxy Clusters: The Leo Triplet, the Virgo Cluster in the Local Group
Beyond that, we can now see the area known as the Realm of the Galaxies – Constellation Virgo . With the aid of a small telescope, we can view Galaxies and Clusters of Galaxies, as we are looking out of the plane of our own Milky Way Galaxy
M104 – Galaxy – Distance ~31 Million light years
M104 more commonly known as the Sombrero Galaxy is an almost edge-on, spiral galaxy located in Virgo. At magnitude +8.4, the Sombrero appears in binoculars as a small patch of nebulosity. One feature that can be observed with a medium sized telescope is the bulge of the galaxy and a hint of a dust lane encapsulating the bulge.M104 was one of the first galaxies to have its spectra and velocity measured by Vesto Slipher in 1912. He noted that the object was redshifted and therefore receding from us, the current accepted rate being 900 km/s. Slipher’s redshift calculation of M104 along with similar observations from other galaxies pointed towards an expanding Universe- confirming Hubble’s formulation. The Sombrero Galaxy is located very close to the constellation boundary between Virgo and Corvus. – text courtesy freestarcharts.com
Galaxies beyond our Galaxy in Leo – Distance 35 Million light years
M65 part of the Leo Triplet of Galaxies – courtesy P. Browne 2014
Star Hop to the Leo Triplet
Leo Triplet is 1/2 way between the star Chertan (theta) and iota Leonis.
The Virgo Cluster of Galaxies: A Glimmer of Galaxies
If the sky is sufficiently clear, we can attempt to look into the heart of the Virgo cluster of galaxies. Beware, these glints of light are faint composed of photons travelling the distance of 60 Million light years to hit the telescope mirror and register on your retina!
Across the heart of the Virgo Cluster of Galaxies lies a striking string of galaxies known as Markarian’s Chain. The chain, pictured above, is highlighted on the upper right with two large but featureless lenticular galaxies, M84 and M86. Prominent to their lower left is a pair of interacting galaxies known as The Eyes. The home Virgo Cluster is the nearest cluster of galaxies, contains over 2000 galaxies, and has a noticeable gravitational pull on the galaxies of the Local Group of Galaxies surrounding our Milky Way Galaxy. The center of the Virgo Cluster is located about 70 million light years away toward the constellation of Virgo. At least seven galaxies in the chain appear to move coherently, although others appear to be superposed by chance.The Virgo Cluster of Galaxies is the closest cluster of galaxies to our Milky Way Galaxy. It contains over 100 galaxies of many types – including spiral, elliptical, and irregular galaxies. The Virgo Cluster is so massive that it is noticeably pulling our Galaxy toward it. The cluster contains not only galaxies filled with stars but also gas so hot it glows in X-rays. Motions of galaxies in and around clusters indicate that they contain more dark matter than any visible matter we can see. The center of the Virgo cluster might appear to some as a human face, and includes bright Messier galaxies M86 at the top, M84 on the far right, NGC 4388 at the bottom, and NGC 4387 in the middle. – courtesy Astronomy Picture of the Day … in May
We need to do ‘galaxy’ hopping in constellation Virgo. We will be targeting M84 and M86 as the “eyes” of the face of Virgo. These 5 galaxies form part of the eight galaxies known as the Markarian chain which may be a group of galaxies dynamically interacting with each other causing gravitational accelerations, and causing some of its members to shoot to high velocities – in the case of M98 blue-shifting the light as they may be bouncing towards us rather than red-shifting away in the flow of recessional velocity of the expanding universe.
Galactic Pair in the Big Dipper. M81 and M82 – Distance 11 million light years
When we look North, we see the Big Dipper. This constellation (Ursa Major, “Great Bear”) rotates around as it circles around Polaris the sky over the year. But never sets – just appears in different orientations each season. Here are the Pair of galaxies M81 and M82 in Ursa Major . M81 appears as an oval patch of light with a bright core, flanked by 2 stars; while M82 appears elongated like a cigar. Because of its shape M82 is sometimes known as the Cigar Galaxy. With low magnification (more sky for your eye) you can see them both in the field of view.
M82 shows a dark rift crossing near its central point, and also shows brighter clumps of material along its length.
Summary – Spring Constellation Targets in South and East
Constellation Cancer – M44 and the more distant M67
Constellation Coma Bereneces – Naked Eye Coma Star Cloud (Open Cluster)
Leo Triplet of Galaxies
Constellation Ursa Major Galaxy Pair
Galaxy pair M81 and M82
In the same region of sky, in the asterism of the Big Dipper, there is a famous double called Alcor and Mizar . Doubles(Alcor/Mizar),doubles(MizarA,MizarB, (doubles MizarA’,MizarA”). See: Doubles of Doubles Alcor And Mizar
You can observe this any time of the year because these stars are circumpolar!
Direction North – Circumpolar Constellations
North Circumpolar Constellations never disappear behind the glare of the sun. Here’s an overview from Terrence Dickenson’s NightWatch – Chart 1 – Polestar Polaris upper right
M51 and NGC 5194 – The Whirlpool Galaxy (ies) – distance ~25 Million light years
At right angles to the Alkaid, the last star of the big dipper is actually a pair of interacting Galaxies: The Whirlpool Galaxy (M51 and NGC 5194). M51 is considered to be a ‘grand design’ spiral galaxy with ” prominent and well-defined spiral arms, as opposed to multi-arm and “flocculent” spirals which have subtler structural features. The spiral arms of a grand design galaxy extend clearly around the galaxy through and can be observed over a large fraction of the galaxy’s radius.
Density wave theory is the preferred explanation for the well-defined structure of grand design spirals. According to this theory, the spiral arms are created inside density waves that turn around the galaxy at different speeds from the stars in the galaxy’s disk. Stars are clumped in these dense regions due to gravitational attraction towards the dense material, though their location in the spiral arm may not be permanent. When they come close to the spiral arm, they are pulled towards the dense material by the force of gravity; and as they travel through the arm, they are slowed from exiting by the same gravitational pull. This causes material to clump in the dense regions. At the center of these galaxies are supermassive black holes. – courtesy wikipedia M51
To understand more about Galaxy morphology see:Millstone Night Sky – Galaxies