Thread by @AfricaAstronomy

Beautiful pics of comet #NEOWISE are everywhere this week, taken from the northern hemisphere. Why is this so, and can we see it from Africa? A thread on #CometNeowise

For a timelapse from the @Space_Station see

First, for some basic info on its visibility and many pretty pictures, see skyandtelescope.org/astronomy-news… on Comet #NEOWISE

The comet #Neowise survived its closest approach to the Sun on July 3 and is now a naked eye object in the morning sky, easily visible through binoculars, and makes for some spectacular photographs. space.com/comet-neowise-…

To find out where comet #Neowise will be on your sky from any location, and on any given date and time, check out the interactive map at theskylive.com/planetarium?ob… - you can change the location and date/time there ...

The comet is now a bit N of the Sun. Its declination is ~+40 degrees today. So it shud be seen from all of Africa. But it is currently slight W of the Sun; its Right Ascension is a bit less than the Sun & that's why it's impossible to see the comet from S of the Sahara for now.

Why is that? This is due to the same reason that we have seasons, or why the Sun is low in the sky at noon in winter - the rotation axis of the Earth is tilted from the revolution axis around the Sun. See cseligman.com/text/sky/motio…
and
courses.lumenlearning.com/astronomy/chap…

Comet #Neowise currently rises before the Sun does, in the Eastern sky in the morning. However, if the comet rises an hour or more earlier than the Sun, then we can see it easily before the sky gets too bright. If the Sun rises soon after the comet then it will be lost ...

... in the glare of the Sun. The more south you are on Earth, smaller is this time difference between sunrise and the rise of comet #Neowise. This is why we can see the comet right now from Africa only if we are north of the Sahara.

The images here are taken from Stellarium and show the position of comet #Neowise (in the centre of the red cross-hairs) on the morning of 10 July from Algiers, Nairobi and Pretoria. The grid lines meet at the north pole.

These pics show clearly how the time between comet rise and sunrise becomes less and less, the more south you go. This is why we can't see comet #NEOWISE if we are living south of the Sahara.

But worry not - after mid July, when the comet shifts to the evening sky and moves farther from the Sun in the sky, all of us in Africa can get to enjoy it from where we are!
(image credit: @jperez1690)

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