A monthly look at astronomical events in the sky and on Earth
Well, it’s arrived: the astronomy season for real. Suddenly, shockingly for some, now the clocks have gone back it’s getting dark by just after 5 p.m. and that’ll be 4:30 p.m. at the end of the month. No longer do we have to wait until after bedtime to see anything. The whole evening is at our disposal. So what’s up there?
Transit of Mercury Monday 11th November
This is the big event this month, and though not as dramatic as a transit of Venus, still worth observing. It starts at 12:34 GMT and continues until sunset at 16:10, by which time Mercury will have completed about 2/3rds of its travel across the solar disc. Note that Mercury’s black dot is about 190 times smaller than the diameter of the sun’s disc so you’ll need a decent projection system to spot it.
In-the-sky.org has a very comprehensive article on this transit. If you’re new to this type of observation, I recommend you read the entire article, with particular reference on how to observe the transit safely.
Best seen as a waxing crescent low in the south after sunset from the 1st through to first quarter on the 4th and on through its gibbous phase through the week commencing the 4th. It’s quite high in the sky and conveniently placed for early evening observations – with the children perhaps.
Venus and Mars
Are both too near to the sun and unobservable this month.
At the beginning of the month, Jupiter is very low in the SW at sunset and by the end of civil twilight (about 1700 hrs) has sunk to only 7° above the horizon. Unless you’re desperate, I’d give up on Jupiter until next year if I were you.
Saturn is not much better I’m afraid. It too is low and in the SSW at twilight. The moon is 5° to its left on the 2nd.
Uranus reached opposition on the 28th October and will be conveniently placed for observation in November and December. The best times are in the first three days of the month before the moon gets too bright or from the 17th onwards, when the moon won’t rise until after 8 p.m. Here is a finder chart for Uranus for mid-month at around 8 p.m. Look to the SE; note the square of Pegasus and Taurus to help you get your bearings. Any pair of binoculars will do to spot it.
Uranus is at magnitude 5.7, which is just bright enough to see with the naked eye on a crystal clear night from a dark site. It’s angular diameter is 3.7 arc seconds so should appear as a tiny blue-green disk in a good quality telescope. It does have satellites of course but you’ll need an 8 inch telescope and a magnification of 300x or more to see even the brightest (Titania at mag. 13.7).
Neptune reached opposition in September, but this month presents a good opportunity to find it at a sociable hour. It’s due south at 8:30 p.m. at the beginning of the month, and at 6:30 p.m. on the 30th. At magnitude 7.8 you’ll need a finder chart to locate its 2.32 arc seconds diameter blue disc, and to see it as a disc rather than a star, you’ll need a fair-to-decent telescope, say 6-inch or larger. Its apparent diameter is about the same as the diameter of the four main satellites of Jupiter.
Have a go on the 1st or 2nd of the month or wait until the 17th or later when the moon’s not around.
The finder chart below is for the 17th at 7:30 p.m., looking south. If you can find the 3.7 to 4.4 magnitude triangle of stars round it, the planet is 1¼° to the right of the top one.
The following finder chart homes in on Neptune and shows that triangle of stars. This is quite a challenge so good luck. Please use the “Reply” facility at the end of this article to let us know if you find the planet.
Non-Solar System Objects
The star of the show for November and December must surely be M31, the Andromeda galaxy. In case you don’t know how to find it, the chart below should help. It shows a 100 degree circle centred on the zenith. Use the top two corner stars of the square of Pegasus, go left one star, then left one more, then up two stars, and M31 is to the right of that last star.
Many people don’t realise how big (in angular measure) M31 is. Believe it or not it is over 3° wide. That’s six times the apparent diameter of the moon. It is also much fainter than its magnitude of 3.5 would suggest because that magnitude is spread over an area of at least 2.5 square degrees. Understand then, that you should not just point any old telescope and eyepiece combination at it at any old time and expect to see it at its best.
Firstly, don’t even think about it if the moon is around. To give it your best shot, wait until the second half of this or next month, and before the moon rises.
Secondly, again, don’t even think about it unless the sky is really dark and the clarity is high. It doesn’t have to be cloudless if the gaps between the clouds are very dark but if there’s even a hint of mistiness or high cirrus cloud, forget it.
Thirdly, you must use a low power wide field eyepiece to get all that 3° width into the field. If you don’t, you’ll only see the central area of the galaxy. In many cases, a good pair of binoculars held really steadily (perhaps on a stand) is the best way to see this exceptional object.
Fourthly, use averted vision. Don’t look straight at it; look to one side or above or below. If you do, whilst remaining aware of the centre of the field, it will look brighter. That’s because you’re using rods (which detect dim light), which are not present in the central axis of the eye. If you’ve never used averted vision, now is the time to try it. There’s an excellent Wikipedia entry on averted vision, which I recommend you read.
And finally, you won’t believe me when I tell you that in fact, in terms of surface brightness of an extended object like M31, the highest surface brightness is achieved by using the unaided eye. In other words, M31 looks brighter with the naked eye than through any telescope. There, I knew you wouldn’t believe me! Through binoculars or a telescope, what makes you think it’s brighter and easier to see is that it’s bigger, and you’re actually seeing the brighter condensed central area.
If you think about it, visibility of the Andromeda galaxy is about the same as the visibility of our own Milky Way. They are both spiral galaxies seen edge on or nearly edge on. The only difference is the distance. So if you can’t see the Milky Way arching overhead from east to west, you won’t see M31.
There’s a similar galaxy to M31 not far from it. It’s the M33 Triangulum galaxy. It’s there on the chart above. M33 is smaller and much fainter than M31 and we’re seeing it square on, so its surface brightness is even less than M31’s. It’s quite a challenge to detect it.
Passes of the International Space Station (ISS)
The ISS is visible for the first eleven days of November and also from the 23rd. See the Heavens-Above web site for more details. Go to this page with all fields relevant to York selected.
For up-to-date news on space missions, rocket launches etc., see Space Launch Calendar 2019: Sky Events, Missions & More.
Clear skies and good viewing.
John Rowland 28/10/2019