CN FORUMS ARCHIVE Telescope Reviews: A little handheld fun in M45

Burnham 536

Just before arriving home, at 21:30, I thought this would be a nice opportunity to try
out my new 8.5x42 binocular under the night sky. The sky was quite bright,
approximately 5.2 mag. I panned around and had also a look at the Pleiades. I
remembered Ed's "Fun in M 45", but I had no sky map and no books with me. All the
same I tried to find out what Ed could have meant. I leaned my elbows on the car's
roof, and quite soon I found: "Here it is, a double star!" I tried to see it again, but now
it was at maximum elongated, and how hard I tried, it became nothing more. That felt
strange.

I drove the last hundred meters home, fed the cats, and checked with my astronomy
software, and yes, there seems to be a double star, but according to Starry Nights it
is only an *apparent* one, not a real one.

Today I have been out observing birds for many hours, and so I felt too lazy to go out again, so
I tried observing out of my kitchen window, but my eyes were not dark adapted at all,
and the lights of our little village were disturbing, NELM was probably less than 5 mag. I
leaned my left elbow at the window frame. I could not lean the right elbow.
Using my 10x32 the double star was difficult to be seen at all.
With the 8.5x42 after a certain time, Burnham 536 was sometimes to be seen as elongated.
I went for the 10x56 and with a little patience, and some trying out I was able to see
the double star *twice* blinking up as two distinct separated stars. Both times the
blinking was short, less than one second.

So this was:
Burnham 536 at around 21:30, altitude around 24°, NELM around 5.2 mag:
Seen once shortly as separated with a 8.5x42 binocular (braced). Several times as elongated.

At around 22:30, altitude around 15°, approx. NELM 5 mag or less, left elbow leaned
at the window frame:
Not easy to be seen as a star with 10x32.
Sometimes elongated with 8.5x42.
Twice blinking as a clearly separated double with 10x56.

Now I had to check if this was really Burnham 536.
Burnham's Celestial Handbook answered this question: Yes, I had it right.

But new questions came up right now:

Burnham describes his Beta 536 as a triple system, with the following brightnesses:
8.5 - 9.5 / - 8 / - 12. Distances: 0.6, 39.1 and 18.1".

This seems somewhat confusing, as three distances would indicate four stars.
So Burnham 536 could be a quadruple system. I tried to check this:

Astronomy application program Starry Nights shows a 8.1 (TYC1800-1961-1) and
a 9.3 mag star (TYC1800-1961-2) in a distance of 0.84".
A 7.55 mag star (TYC1800-1974-1) is distant 38" from the 8.1 star. I guess this (= the
8.1 star and the 7.6 mag star) is what gets called Beta 536 or Burnham 536.
There is no 12 mag star in a 18" radius.

TheSky shows a 8.3 mag star (SAO 76169, GSC 1800:1961, PPM 92858, HD 23479)
and a 40" distant 8.4 mag star (SAO 76167, GSC 1800:1974, PPM 92857, HD 23463).
There is no mentioning of these two stars being a double star. TheSky shows also a
double star called WDS 2755, separation 4", brightness 8.6 mag, distance from
SAO 76167 is 14".

I consulted many internet pages, and this did not really help. Except for Mr. Burnham's
idea, there seems to be no more data indicating that these stars could be a real gravitationally
bound system.

Well, here I gave up... Maybe this is not really that important, after all.

The practical part was more fun, even if it seems that the two easy-to-split stars of
Burnham 536 are not real double stars, but so called "optical double stars" (= two stars
that are only close on the sky, but in fact are separated by a great distance in space.
They are not gravitationally bound to each other). Of course, being members of the
M 45 open cluster, they still travel together.

Amalia

Edited by Amalia (04/07/07 10:39 AM)