Urban Astronomy – Comet Leonard 12/20/21

Posted December 20, 2021

The night sky is pretty much a mystery to most City Dwellers.  The glare of city light drowns out all but the brightest stars – and planets don’t do much better.  If you are interested, I can tell you where to look to see these far-off worlds.  If you were not interested, you would have stopped reading after the first sentence. 

So, at this point, I know my audience. 

Comet 2021 A1 – Leonard Dec 20, 2021

Leonard is even brighter – in fact much brighter – tonight. The current magnitude of Leonard is +2.3 (the smaller the number, the brighter – the comet was +4.6 yesterday and Saturn is +0.23 – VERY bright by comparison) so in the city, the Comet is visible and would be still better seen with binoculars. 

You may have heard the expression “by an order of magnitude”  – well this is over two orders of magnitude – OK?

Once again, do not use telescopes or binoculars to view the Sun – blindness will result!  I said “after sunset” so you should be OK if you listen to me. 😉

As is usual in these cases, the comet gets brighter not only because it gets close to the Earth.  It also gets brighter because it gets closer to the Sun.  The third brightening influence is the material that the closer sun vaporizes.  That stuff makes a cloud around the comet and is it also partially blown away by what is called the Solar Wind – in a comet’s tail.

Figure 1, above shows the location to view, which is conveniently close to Venus, which is the brightest thing in the sky.  If you can see the Planet, you should be able to see the comet – although you may need those binoculars to do so. 

The sky is currently “mostly clear” (look-out-window method) in Houston at 3:22 PM.   Sunset is at 5:26 PM.  These next few days are literally the last chance to see Leonard, as it is on a hyperbolic orbit – which is a nerdy way to say that it will never return to the Solar System.  (Please see figure 2 below)

For readers not in the Houston area, just look for Venus (and Jupiter for orientation) and use the chart in Figure one above to find the comet.  We are lucky to be able to have the two brightest objects in the sky (now that the moon is not around in the early evening) as our reference points.

Hasta Luego,

Steve

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