Archive for July, 2012
If you haven’t gotten up before sunrise to look at Venus and Jupiter in the eastern sky, you really should. They make a beautiful sight. As an added bonus, if you view in full dark they appear against the V-shaped star cluster called the Hyades containing the bright red star Aldebaran and the Pleiades star cluster appears above Jupiter.
As promised, here’s a better picture of Venus taken with a variable polarizing filter to cut back the glare.
It is still a crescent but is thickening as it heads towards greatest elongation on August 15 when it should appear half-lit.
Here’s an unfiltered picture of Jupiter taken as the sky was beginning to lighten and showing the orientation of the Galilean satellites. All four are visible.
As you can see, Jupiter itself is highly reflective and the photograph reveals little detail. As viewed unfiltered through the telescope, often you can only just make out a couple darker atmospheric bands. Here again, the variable polarizing filter helps bring out some detail.
The Moon was at first quarter above the southern horizon last evening as shown in the photo below.
This picture was taken using a variable polarizing filter I just received. It is great because the amount of light that passes though varies from 1 to 40% with an easy twist adjustment. It helps cut back on the glare as the Moon can be very bright through even a small telescope. I personally think I had it a bit too dark but the clouds were rolling in so I didn’t have a long time to play.
Over the next few days the Moon will appear more and more gibbous and more to the east-southeast in the early evening. Here is a picture of the waxing gibbous Moon from last month (June 28) taken while there was still light in the sky. This one is unfiltered.
One of the nice things about viewing the Moon is that it’s often bright enough to enjoy during the day. You might catch it in the afternoon in the next few days during the waxing gibbous phase and then again in the morning hours during the waning gibbous phase. At full Moon, it rises at sunset and is out essentially all night.
It was last summer when I really decided to take up observing the night sky as a hobby. The return of the familiar star patterns brought me great comfort this spring.
Earth’s rotation can be cited for the change in the night sky over the course of an evening. For changes occurring over the course of seasons, we have to cite the revolution of the Earth about the Sun for an explanation. This seasonal change gets more dramatic in the sections of sky further away from Polaris. Watch the Big Dipper over the course of the year. From our latitude you can see it all year long – it will appear to swing around Polaris. However Orion, arguably the most recognizable constellation, only appears on the southern skies in the evening during the winter.
In July, our southern skies are dominated by another constellation nearly as spectacular as Orion – Scorpius (Latin for scorpion). He is currently right above the southern horizon just slightly west of due south after sunset. The best constellations contain bright stars and look like their namesake. Scorpius is no exception. The first star you will probably see is the very bright star Antares which will appear red. Antares often represents the heart of the scorpion. Above Antares are three stars that really appear as the head of a scorpion. His tail, complete with stinger, swings down dangerously close to the horizon and in fact may never rise above it depending on your latitude. We sit down in a bowl, so unless I make a special trip to find an unobstructed southern view, I often only see the head and heart of Scorpius.
Take a moment to enjoy Scorpius in the next few days. This is his prime viewing time as he’s highest in the south just after dark. Over the next few months he’ll transition lower and to the west eventually dipping below the horizon, perhaps seeking cover for the winter.
. . . fragments of comet Shoemaker–Levy 9 began colliding with Jupiter.
Shoemaker–Levy 9 was the first comet to be found orbiting a planet (Jupiter). It had been broken up, probably a couple years previously by close encounter. Tidal forces resulting from Jupiter’s gravity tore it apart into smaller fragments which can be seen here courtesy of NASA and the ESA:
This was also the first time astronomers had directly observed a significant collision between objects in the Solar System. As such, it was an amazing scientific opportunity. The entire event provided insight into Jupiter’s atmosphere and influence on the remainder of the Solar System. A major surprise for astronomers was the visual effect of the impacts. Here, courtesy of NASA, you can see scars across the face of the planet from the impacts which persisted for months afterwards.
You can find a lot more information on this fascinating event here:
On June 28 I noted that you could see Venus and Jupiter together again, this time in the east-northeast sky and in the morning prior to sunrise. We can delve into this repeat performance even further if we choose. If you followed Venus prior to the June 5 transit you may recall that Venus reached greatest elongation on March 27 and achieved peak brightness on April 30. During this time, through the telescope, it progressed from appearing as a half-lit Moon to a thin crescent and ultimately as a black disk against the face of the Sun on June 5. Now that entire sequence is unraveling in reverse as Venus has overtaken us and is pulling away in its orbit. Venus has progressed back to a thin crescent and achieved peak brightness yesterday. It reaches greatest elongation on August 15.
Here’s a picture through our Meade LX-90 from the morning of June 10:
You can see that Venus is a crescent but it is so bright that the thickness of the crescent is exaggerated in the camera. I really should be using a filter here to cut down on the glare. I have one coming, hopefully better photos will follow. One of these days I’ll post on my adventures in astrophotography so far.
You may want to compare this photo with the one I posted on May 23 to see the now opposite orientation of the crescent. (Of course the images are themselves inverted because they’re both through a telescope!) Hopefully I’ll have more photo opportunities as we approach greatest elongation to show the phase changes.
Happy 4th of July! Aside from celebrating the adoption of the Declaration of Independence in the US, today is also significant astronomically in that Earth arrives at aphelion, the point in its orbit when it’s farthest from the Sun. We have now completed half an orbit since our discussion of perihelion on January 4.