I know that the sun is lower in the sky these days in the northern hemisphere, because we’re more or less tilted away from the sun - ergo, shorter days, less overhead heating, etc. However, we still do see the sun, so I don’t understand why a comet that has rounded the backside and is now on the way out to the solar system again would not be visible to us. We saw it as it went behind the sun. What’s up with this? I’m not getting something fundamental, I guess. Here’s a quote from a website that follows these things: *“Comet McNaught is emerging from the glare of the sun and, as expected, solar heating has turned it into a spectacular naked-eye comet. McNaught is visible from all parts of the Southern Hemisphere, sporting a curved tail and a head almost as bright as the planet Venus. Northerners can watch the comet’s progress by browsing daily photo galleries at http://SpaceWeather.com” * Why can’t we just look in the morning and see it emerging from behind the sun before the sun rises? What am I not getting?
I don’t know, but I though I read that Monday the 15th was supposed to be a good day (if you’d missed the previous week or so like we did due to weather). So I went out to the country with a small spotting scope just before sunset and looked and looked. I could see Venus but I never saw even a hint of a comet.
I believe it’s because it didn’t so much go “around the side” of the sun, as “over the top and back under”.
So, from a Northern hemisphere viewpoint, imagine looking South. The sun rises somewhere in the South-East, does its arc, and sets in the South-West. From this point of view the comet is under the sun, so you can’t see it until the sun is high enough, but then it’s too bright.
From the Southern hemisphere viewpoint, imagine looking North. The sun rises somewhere in the North-East, does its arc, and sets in the North-West. From this point of view the comet is above the sun, so you see it before it just before the sun rises and just after it sets.
I think this is right, from what I’ve seen of the orbit pictures.
I looked at a website New Comet is Brightest in 30 Years | Space
I don’t understand how the comet could have been visible both in the morning AND at night. I mean, its on the morning side of the sun or the evening…not both?
Can someone explain it to me in small words and hand gestures.
We in the continental US never get to see cool stuff like comets, eclipses and other gee-look-at-that stuff. It seems like every time I hear about something like that, it’s followed by “…can only be seen by people in Outer Bumfuckia at 3am on Tuesday”.
I know, I know…it’s a big world, statistically we see the same number of events as other locales, all our damn streetlights and strip malls drown them out, blah, blah, ho hum, etc.
Phaemon is exactly right. The comet is at declination -33, so it rises well above the horizon at northern mid-latitudes. (To the OP: for questions like this, joke locations are not helpful.) However, any time that it’s above the horizon, the Sun is also.
Sigene: Think of the early sunrises and late sunsets in summer. Imagine an object even further north than the Sun at the solstice. It would have an “object-rise” even earlier than sunrise and an “object-set” even later than sunset . . . and be visible at both ends of the day.
According to today’s APOD, “Comet McNaught is now reportedly so bright that it is visible even in broad daylight by blocking out the Sun with your hand.”
It’s cloudy here, but perhaps another doper could verify this?
From where? We tried looking at the area around the sun with welding hoods, blocking out the sun with my thumb/fist and still never saw a comet. Looked out maybe 10 sun diameters from the sun in all directions. From Texas, FWIW.
Some northern hemisphere sightings are discussed in this thread.
It was almost directly north of the sun. Which meant from the northern hemisphere, it was above the horizon longer than the sun - it rose before the sun did, and set later than the sun. If it were all the way north, near Polaris, it would have been visible all night (and all day, if bright enough).
I think the situation is now reversed - it’s moved south of the sun, so for northern-hemisphere viewers, it rises later than the sun (if at all) and sets earlier.
It shouldn’t matter. The comet is near the sun from any earthly viewpoint, so if you can see the sun you should be able to see the comet.
From Space.com:
Good answers. I think McNaught’s position is hard to comprehend because we are used to think of our solar system objects in terms of the planetary plane, which is pretty much flat. So the inner planets Mercury and Venus are always either to the east or to the west of the Sun (whenever they’re not too close to it to be seen), never are they straight to the north or to the south of it. That means Venus is either a morning or an evening star, not both at the same day, and if it can be seen from mid-latitudes of either hemisphere, then it can be seen from the another too. So for many people it is a little hard to understand why this comet could be seen before 12 January both morning and evening in northern hemisphere, but can not be seen there at all after that date.
The reason, as explained in the above posts, is that McNaught does not move in the planetary plane, but over 75 degrees inclined towards that. It came from the side of the plane that corresponds with the southern hemisphere, but already at the time of its finding last summer, it had moved to another side, that corresponds with the northern hemisphere, and so was approaching the Sun from north. During the last week (about 8.1. to 12.1.) when the comet was truly a great show in northern hemisphere it was almost exactly north to the Sun. But then it moved again back to the southern side of the planetary plane and disappeared from our northerners’ view, except for those who see it in broad daylight, though I was unable to see it this Monday even though it was a very bright day. Right now McNaught is almost exactly to the south of the Sun.
But I’m not very good at explaining comet orbits. Look at this Java applet from NASA instead, it does a nice job in visualizing the whole thing. For example you can see that McNaught’s orbit did not at any point take it behind the Sun, from an earthly viewpoint the comet passed our star from east.