April 20, 2014

Astro-Event: A Spectacular Dawn Appulse.

Venus versus Regulus: the view on October 3rd.

(All simulations created by the Author in Starry Night).

It’s a question we have posed before, worthy of a sequel to Arthur Upgreen’s alternate astronomy book Many Skies; what would Venus look like if it had a moon? As a kid, I remember a science book on the solar system looking back at the Earth-Moon system from Venus, assuming that you could get above the cloud tops. At greatest elongation, Earth’s Moon would be 9’ arc minutes from the planet’s -3.6 magnitude disk this month and would itself shine at +0.5 magnitude… what a view that would be!

Earth & the Moon as seen from the environs of Venus!

This first week of October offers us a similar “mock view” as the planet Venus passes very near the bright star Alpha Leonis (Regulus) in the constellation Leo the Lion. This is the closest conjunction of a planet with a +1st magnitude or brighter star in 2012, and should not be missed! Regulus is one of a handful of stars that lie close enough to the ecliptic that the Moon & planets can pass near or even occult. Others in this prestigious club include Aldebaran, Spica, and Antares. In fact, stick around long enough, and the planet Venus will actually occult Regulus on October 1st, 2044! Let’s see, by then we’ll be…

The passage of Venus by Regulus for the 1st week of October.

But onward to the exciting geometry of the situation. Venus passes less than 7’ arc minutes from the star +1.3 Regulus on October 3rd at 1:00 AM EDT/5:00 UTC. Venus shines at magnitude -4, about 100 times brighter than Regulus. Regulus is 77 light years distant, while Venus is a paltry 9 light minutes distant. The pair will seem to merge as viewed with the naked eye, but will be an easy capture at moderate power in the eyepiece. Note that we’ve talked about spurious reports by observers in antiquity of a mythical moon of Venus named Neith, and there has been conjecture over the years that such reports where due to a passage of Venus near a bright star. While we doubt that such a familiar star as Regulus could have been the source of said sightings, this week offers a great chance to look upon our sister world and wonder about spurious sightings as well the appearance of our own “binary planet” from afar!

A daytime Jupiter on September 8th, 2012 as seen from Astroguyz HQ!

(Photo by Author).

Another interesting pairing occurs on the night of October 5th going into the morning of the 6th, as the waning gibbous Moon is very near the planet Jupiter. In fact, the 71% illuminated Moon will actually occult the planet for viewers in southern Australia around 22:00 UTC. The rest of us will get a very photogenic less than 1 degree pass, and it should be possible to track the pair into the daytime skies on Saturday, October 6th. Jupiter currently rises just past 11PM local for mid-northern latitude viewers. The Moon will also occult the much fainter (+8.6 magnitude) asteroid 1 Ceres on October 7th at 3:00 UTC for South Africa.

Finally, it’s worth noting the Draconids (or do you say Giacobinids?) peak this weekend headed towards the morning of October 8th. While it’s true that this is generally a weak meteor shower with a Zenithal Hourly Rate of less than 10, 2011 was witness to a great meteor storm of activity. This is always a shower worth watching out for!


  1. [...] to the ecliptic to encounter the Moon & classical planets. (The other three being Aldebaran, Regulus and Spica. In fact, we caught the nearly Full Moon in the act of occulting Antares here from [...]

  2. [...] 3rd: Venus has a close (0.5° degrees) conjunction with the bright star [...]

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