February 16, 2010

A STAR HOP IN ORION




1. Betelgeuse
2. NGC 2169
3. Zeta Orionis
4. Sigma Orionis
5. NGC 1981
6. NGC 2377
7. M43
8. M42
9. Iota Orionis

Orion stands well in the sky after evening twilight. There are many favorite objects for the amateur astronomers including The Great Orion Nebula (M42).
I decided to star hop in this constellation on the night of 13th February 2010. I used my 8-inch f/6.5 Newtonian Reflecting Telescope operating at 32.5x, 76x and 162.5x magnifications.
1. Betelgeuse: Our starting point is Betelgeuse or Alpha-Orionis and is located 640 light-years away from us. Betelgeuse is a semi regular star and second brightest in the constellation Orion. Betelgeuse is a Red Supergiant and one of the largest and most luminous stars known. For comparison if the star were at the center of our Solar System then its surface might extend out to between the orbits of Mars and Jupiter. In my 8-inch reflector at 76x, the star looks brilliant orange.
2. NGC 2169: This is the 6th magnitude Open Cluster lies some 7 degrees N-NE of Betelgeuse between the stars Xi and Nu Orionis. This cluster is also known as the “37 Cluster” because its shape. Through my 8-inch at 32.5x, I can see 11 stars in the cluster which makes the shape like the number 37. At 76x, I can count 12 stars.
3. Zeta Orionis: Like other Belt Stars, Zeta is a 2nd magnitude blue-white star located about 1500 light-years away. In the 8-inch, Zeta is a blaze of cold white light. This star is also known as Alnitak.
4. Sigma Orionis:


Sigma is a dazzling quintuple star with a fainter triple in the same view. The brightest component is Sigma AB, itself a pair separated by only 0.2” and very hard to resolve in amateur telescopes. My telescope working at 76x shows me the component C. The component D was very hard to resolve at this time however I
have observed it a couple of times away from the city lights.
Struve 761 is a triple star system viewed in the same field of view along with Sigma Orionis. My telescope shows all the three components A, B and C at 32.5x.



5. NGC 1981: A very fine, big and loose Open Cluster at the top of Orion’s Sword. The cluster fits well in my scope’s field at 76x. The most eye-catching feature is the three 6.5 magnitude stars. The top most star of these three is a double but I couldn’t see it at this time. The companion is an 8.3rd magnitude star.
6. NGC 1977: NGC 1977 is an open cluster surrounded by two diffuse nebulas NGC 1973 and NGC 1975. You will need an O III filter and a dark sky to have a glimpse of these nebulae.
7. M43: A small patch surrounded of Nu Orionis star. This nebula is also known as the Comma Nebula.
8. M42, The Great Orion Nebula: This is the most famous emission nebula in the sky and the most favorite site for almost any telescope user. In my 8-inch scope at 32.5x, the nebula looks great much like photographs, showing two bright, outstretched arms, tulip-like enclosure. In the middle of the nebula is the quadruple star Theta 1 Orionis. A landmark feature here is the intrusion of a dark nebula that extends from the east almost to the Trapezium. This feature is also known as the Fish Mouth.
The Trapezium is the group of bright multiple stars seem to have blown a hollow for itself deep inside the nebula, and we are looking down into this hole as if into the much of a bright green cave. The brightest star in the Trapezium is Theta C. To its northwest and northeast are A and D. This time through my 8-inch reflector at 162.5x, I could see only four main stars of the Trapezium, A, B, C and D. No E and F were visible because of moderate sky conditions.



9. Iota Orionis: Iota Orionis is a dazzling star at the bottom of M42. The star is also known as Nair Al Saif. Through my telescope at 76x, I can see its companion which shines at magnitude 7.7. The companion is at 11” from Iota.
-Rahul Zota (Bhuj-India)