Expert: Tom Whiting - 9/25/2010

Question
QUESTION: I live in the Central Texas are and have a very good view of the night sky with very little light interference from city lights. I have been seeing a very bright object in the southwestern sky that appears just after sunset. I read another post from a person in San Marcos, Texas who described this object from 2008. I'v been watching venus all summer... this is not venus. also, it completely vanishes, then reappears. I have been trying to see if it is cloud cover or moonlight shinning on it? I can't tell. Do you have any ideas? Thank you, Jerre

ANSWER: Hi Jerre,
Sorry, but my skyglobe program shows that Venus doesn't set for 80 minutes after your Texas sunset, so there is simply nothing else it could be, although Venus is now getting close to the red star Antares,
a first magnitude star... but Venus at -4th magnitude is 5 magnitudes brighter, or 100 times brighter than Antares.  So if it's not Venus, then I have no idea what it is as there isn't anything else (except the sun and moon)that bright in the SW... but the program I have shows it exactly in the SW sky right after sunset for your location.  Check the setting times just to be certain... I show a 7:20 sunset time, and an 8:40 Venus set time for Dallas, Texas, for tomorrow evening.  If those times are slightly off for your location, then just time the difference, and see if it's 80 minutes for Thursday, Sept 23rd, or even a day or two after, if you have horizon clouds present.  If it's 80 minutes, then it
has to be Venus.

Oh, another option is get some optical aid (small scope will do) on it,
or maybe even a pair of 10 x 50 binoculars... right now Venus exhibits
a long, thin crescent phase, about 15% illuminated. So a small telescope will prove that it's the Venus crescent, or not. That would be definitive.
Clear skies,
Tom Whiting
Erie PA

FOLLOW UP:
What might be causing you some confusion is... earlier this summer,
Venus was high in the west, riding high on the ecliptic, up in the
Cancer - Leo portion of the ecliptic (more northern part of the ecliptic)... and for a while it even set in the WNW.  But now, later, moving eastward along the ecliptic down into the Virgo and Libra southern portion of the ecliptic, plus the planet dove south of the ecliptic also, so now we see it very low and flat in the Southwestern sky after sunset. That's why the difference from May to September.  Of course by mid-October, you won't have to worry about it because it will set the same time as the sun, only very far to the south of the sunset point. We're about to lose it from our evening western sky in only another 2 or 3 weeks, as it passes through inferior conjunction.
Clear skies,
Tom

---------- FOLLOW-UP ----------

QUESTION: Hello Tom, just as an after thought, could this be Jupiter with Uranus very close, and both illuminated by the moon or sun. being planets, I presume that would explain the disappearing & reappearing that takes place during the time they are visible? it seems to completely be gone by 9:15 P.M. I did a little research and found that Jupiter is at it's closest to the Earth at this time. Thank you for your time & patients, Jerre

ANSWER: But you said "southwestern" sky in the evening.  Jupiter (and coincidentally Uranus nearby, barely visible to the naked-eye on a dark moonless night) rises in the "southeastern" sky around sunset. So you said SW and only Venus... fits that description. The only other object
that bright would be the ISS, International Space Station... of course it moves, but it does attain a -3rd magnitude now. And nothing is illuminated by our moon, except the Earth itself.
(Google Earthshine Effect).

While Jupiter is at it's closest on this opposition, because perihelion
is March 17, 2011, only once every 12 years, it's only very slightly better than any other opposition.  It's magnitude -2.9 on this opposition and typically magnitude -2.8 on other oppositions. (See October 2011, November 2012, December 2013, etc. every 13 months there is a Jovian opposition.  And when you're out there some 400 million miles, a few thousand miles closer in, is really no big deal.

Plus, how many people out there (besides me) can differentiate between two objects' apparent brightness of only 0.1 magnitude?  Not very many.  So I don't know what the big deal is this particular year... must be a slow news year for the newspapers. They didn't get all "Ga Ga" back in 1998 or 1986 or 1974 at the last Jovian perihelion oppositions, did they?  At least I don't remember the newspapers saying anything back then.  This one is no different then those others.
Clear Skies,
Tom Whiting
Erie, PA USA

---------- FOLLOW-UP ----------

QUESTION: Hello, Tom, I did indeed look to the southwestern sky with high powered binoc's.... you are absolutely right, I can see it now, this is Venus. I actually also saw jupiter  beside the full moon as well quite a distance from Venus. Thank you very much. I'll be getting a telescope. too much out there to explore! Wishing you clear nite skys Jerre

Answer
Be careful there... in our great hobby of observational astronomy,
equipment comes LAST, not first. Knowledge of the naked-eye night sky
comes first. For if you can't point your finger to the Andromeda Galaxy, the Lagoon Nebula, the Pleiades, Saturn, Albireo, etc (all naked eye objects in a dark sky)..how are you going to point a small viewing telescope at them?  You can't.  Make your first scope a pair of 10 x 50 binoculars, and a very good star atlas or star chart...

PLUS, what do you want to specialize in? (And you will specialize eventually because there is just too much out there)...lunar/planetary details, deep sky objects, double/multiple stars, variable stars, comet hunting, nova hunting, etc.   There is a scope out there that maximizes each one of those activities; so until you know.... Otherwise, we'd all have the same type of scope wouldn't we? But we don't!! Because there are different scopes for different folks.  Scopes are like airplanes - all airplanes fly, but you don't send a bomber to do a fighter's job.
Suggest you at least first punch up our club website, and read "Tom Whiting's Sound Advice for the Novice Observer"  at
http://www.velocity.net/~bwhiting
for the proper way to enter this grand hobby, and avoid a lot of expensive pitfalls.
Clear Skies,
Tom