Expert: Tom Whiting - 4/27/2004

Question
I found your answer to someone who asked a question about a star just west of Orion's belt. (3/6/04) I also noticed an extremely bright spot in the sky just beneath Orion's belt and was wondering whether it's also Venus. I thought it was unusual to see it flicker blue. But perhaps it's just what I thought I saw. The time now is 10:20pm in Vancouver, BC, Canada.

Answer
Christina,
Well, that was 6 weeks ago...things have changed...planets
have moved, and do move....but the stars do not move,
relative to each other.

Venus is the unmistakeable brightest object (at -4th magnitude) in the western sky now  (actually, it's always the brightest, with Jupiter in second place, high in the south now).  Notice it (Venus)is approaching a 2nd magnitude star, Beta Tauri, to its upper left, which it will pass just south of, on the evening of May 3rd.

The bright star (spot, as it is very low) you observed, is the blue-white star Rigel (Beta Orionis) directly below and straight down to the horizon from the Belt stars...but my
star chart program shows Rigel setting at 9:30 pm from
Vancouver, B.C. while Venus sets at 12:25 am now, along
with much fainter Mars to its left.  (So you must have made
this observation about an hour before reporting it at
10:20 Vancouver time.)

Yes, Rigel, being a blue-white supergiant star, at zero magnitude,  would twinkle with a bluish tinge.  Of course, all that flickering and twinkling....proper word scintillation....and rapid color changes, is all caused by our atmosphere, and the lower the body in question, the more atmosphere you are looking through, so the more twinkling.  If we did not have an atmosphere, there would be no twinkling, no color changes, and no horizon atmospheric extinction (things getting dimmer as they approach the horizon)....so we can blame strictly our atmosphere for all of these happenings.

For instance, from the moon, Rigel, (or any other body for that matter), would set over the distant hills the same pure blue-white color, same constant intensity, and exhibit no horizon loss of brightness....the star would simply "wink-out" as it passes over your horizon.

We don't have too many more nights with Orion in our night
sky, as that is a winter area of sky, and this is nearly
the end of April...but guaranteed, it will return to our
night sky next October, if you stay up late enough to see
it rise in the east.

Hope all this helps,
Clear Skies,
Tom Whiting
Erie, PA

FOLLOW UP:
BTW, no planet passes through the region (constellation-area of sky) we call Orion...
as it is not on the Zodiac or ecliptic...planets in that
region of the sky move from Taurus to Gemini to Cancer,
always passing NW and North of Orion....as Orion is not
one of the 13 Zodiac constellations.   Yes, 13...as
the area (constellation) called Ophiuchus, the Snake Holder, is also on the ecliptic...but you've probably never heard of it as....Ugh....astrologers (dirty word to us astronomers)...naturally do not recognize it, but
us astronomers have to recognize and count it.  Because
the sun, moon, and planets all move through Ophiuchus at times. (Its located in our summer sky, midway betweeen Scorpius and Sagittarius).