Venus and Jupiter this evening

[rainyjim]

I'm gonna go out on a limb and give a complete guess that the larger brighter one to the left was Venus and the smaller dimmer one to the right was Jupiter. Looking forward to a Yay or Nay from Tom about this though.

[ericlp]

Yes, venus is always the "Brighter one" It's not only closer to the sun but closer to us...Despite Jupiter being 500 times bigger than us. Jupiter will always be dimmer because it's further away from us and further from the sun, but has a massive gravitational pull.

This isn't a star, it's a planet. Well, both are planets. The nearest star is our sun. These planets may appear close to each other but they still millions of miles apart. They just appear from our orbital perspective that they are getting closer.

Enjoy the dance of the cosmos!

[PaulW]

I noticed it too! I thought: whoah, are they going to collide? Good to hear it's a near miss.

[rainyjim]

Eric, can you explain how jupiter having a massive gravitational pull affects how bright or dim it appears?

Paul, I don't think there was a near miss, maybe I missed your sarcasm? I'm pretty sure they were several hundred million miles away from eachother.

Maybe Tom will be able to clarify some of this for us when he checks in.

[TomK]

Rainyjim,

I think ericlp was just pointing out Jupiter has a massive gravitational pull, which it does, rather than claiming that it has an effect on how bright it appears. In fact, Jupiter is massive enough that due to gravitational contraction it actually emits more energy than it receives. However, that energy is emitted as infrared light so makes no difference to how bright it appears to our eyes.

On the other hand, that mass has had a big impact on our solar system. For decades many felt that Jupiter helped protect us from incoming asteroids and comets by deflecting their orbits. It turns out that when it comes to asteroids and short-period comets, it actually increases the danger by sending these objects into the inner solar system. However, for the most dangerous objects, long period comets coming from the Oort cloud, it does add some protection by deflecting some of those objects out of the solar system entirely.

Venus is currently much brighter (it isn't always brighter than Jupiter although generally it is). It's much closer than Jupiter but its atmosphere contains highly reflective sulfuric acid clouds which reflect most of the light it receives back into space. In fact, if you have a pair of binoculars and can keep them steady enough, you might be able to see Venus currently appears crescent-shaped, from our perspective more than half its planetary disk is in shadow yet it still appears very bright.

And yes, the two planets are about half a billion miles apart.

[PunaMauka2]

i had a good view last night just after sunset in the Kurtistown area as i was driving down to Hilo. the two planets were close enough in the sky to get me wondering if Venus ever actually eclipses Jupiter. and if so, how often.

according to a Wikipedia quick check, Venus did transit (not eclipse) Jupiter most recently on 3 Jan 1818. the next time Venus will transit Jupiter will be 22 Nov 2065, but won't be visible to the unaided/unprotected eye due to the visual proximity in the sky to the Sun.

also came across a term that either i didn't learn or had forgotten from Astronomy 101, ... "occultation" as opposed to "eclipse".

[TomK]

Yep, occultations are actually quite useful for astronomers, they can be used to test various stuff. Although not technical, occultations occur when something passes in front of something else, eclipses involve shadows (but is a type of occultation).

[rainyjim]

Thanks Tom!

Really interesting that its massive gravity actually makes it emit energy, sparks the imagination and curiosity as well!

[TomK]

Renewable energy at its best, the Jovians clearly know how to do it. Clearly, we need to make the Earth much more massive. That should solve over-population as well.

[PaulW]

"For decades many felt that Jupiter helped protect us from incoming asteroids.."
I've learnt something today, thanks TomK. I thought it was still the case, especially after seeing Jupiter suck up that comet a few decades ago.