Really, Mars will NOT be the size of the Moon in the sky!
Published on May 2, 2009 at 3:58 pm.
15 Comments.
Filed under Mars, observing, public science, sky lore, skywatching.
Already, the annual urban myth about Mars being the size of the Moon in the sky is circulating the internet. Come on. Stop it people! Before you forward this thing on to other people, check it out! Actually, before you forward any “news” item that you get in email, text message, etc, verify its accuracy first. There are a number of good web sites for checking on common urban myths, such as Snopes or UrbanLegends. You could also ask somebody who is an expert in the field.
Byrd just got an email from a good friend about the August 27 Mars thing. I have written about this several times over the years, such as this posting a couple years ago and this posting the year before. Go back and look at my previous post for more info. I don’t want to keep writing the same thing over and over again. I’ll quickly summarize, though.
Earth passes Mars every two years, or so (about every 780 days). At that time, Mars appears larger in the sky than normal because we are closer than normal. Both Earth and Mars have elliptical orbits, and the two orbits are not integer multiples of one another. Thus, both Mars and Earth are in different parts of their orbits when the orbits are closest to one another. In August, 2003, the orbits did indeed line up in such a way that Earth and Mars were much closer to one another than normal. Actually, every 15 to 17 years, Earth and Mars have a particularly close opposition. In 2003, though, Mars was a tiny percentage closer than it had been in many thousands of years. That resulted in Mars appearing a tiny percentage larger through the telescope than normal. At the time, Mars appeared about 25 arcseconds across. That made Mars appear to be a little over 1% the apparent diameter of the Moon in the sky. That means that the Moon was still nearly 100 times larger diameter in the sky! But, some reporter asked an astronomer what the significance of such a close opposition was. The astronomer replied that it meant that Mars would be so close and so big in the telescope that a modest amateur-sized telescope, using suitable magnification (about 100 power) could make Mars appear about as large when seen through the eyepiece of the telescope as the Moon looks when you look at it with your naked eye. That got morphed into an erroneous report that Mars would appear as large as the Moon in the sky. Well, the internet, though a wonderful wealth of knowledge, can also be a wealth of errors. The mistaken comment was forwarded and passed along as emails. Eventually, the next year, someone embellished the story, and it became an internet rumor. Mars was not even visible the following August! Remember, oppositions of Mars happen every 780 days. So, the next opposition didn’t even happen until November, 2005. The year after than, a really cute Powerpoint email started circulating the internet, showing Mars and the Moon side-by-side the same size. That NEVER happened, and never will happen! That year, one of the local television newscasts even promoted this urban legend! They retracted it later, once they got flooded with informed callers that had caught them in their error. Still, the damage had been done. We got floods of calls at the college wanting to know if we were doing a Mars watch to see this great event like we’d done for the time in 2003 when Mars was about 1% the size of the Moon. Uh, no. It appears that the urban legend is back, though, for 2009. Someone has updated the Powerpoint presentation, removing the old year and inserting 2009. No, no, no, no! For one thing, Mars will NOT be in opposition this August. The next opposition will not occur until January 29, 2010. At that time, we will be 0.664 AU from Mars, and it will appear magnitude -1.28 in the sky. That’s not as bright as the brightest star in the sky, but it will be brighter than almost all the stars. It should be pretty, because both Mars and Sirius will be up, competing for your attention. Mars will be 14.1 arcminutes across, less than 0.8% of the size of the Moon, and a bit over half the diameter that Mars appeared to be in 2003. It will look something like the picture below:
Remember, this is going to be January 29, 2010. Interestingly, Mars and the Moon will actually be quite close to one another in the sky on that night, but nowhere NEAR similar in size.
But, with the email going around about August 27, you might wonder what Mars would look like then. Well, you’d have to get up early in the morning. Mars won’t be rising in August of 2009 until after midnight. In fact, it won’t rise on August 27 until about 2am around here (a bit different for people in different locations, but still after midnight). It will be north of Orion. It will appear as a reddish object about magnitude 1.6 to 1.7, very slightly dimmer than the reddish stars Betelgeuse and Aldebaran nearby. The image below shows where Mars will be located in the sky on that date at about 4am:
So, to repeat, Mars will not appear to be nearly the size of the Moon in the sky on August 27, 2009, nor on any other date. I am not sure why this rumor persists and gets resurrected and emailed around every year, but it apparently is already making the rounds again this year.
-Astroprof
Mars images, courtesy NASA. Sky views created using Stellarium.
Sili on May 3, 2009 at 6:32 am: 1
Thank you. I didn’t realise there was a rational explanation (telescope). I thought it was just a complete hoax.
Sleepwalker on May 5, 2009 at 7:20 am: 2
Amazingly, It is making rounds this year. I had to explain people the same thing in my office before I stumbled on to this page. Didn’t know that this is a persistent urban legend thoughThanks!
space geek : ) on May 7, 2009 at 12:41 pm: 3
What always amazes me is that there is always some poor gullible soul who believes this email and then gets angry when the expected doesn’t happen… there are soooo many reasons why having Mars be that close would be a VERY BAD THING though… now that’s the kind of email I’d like to see going around!
Eric on May 7, 2009 at 5:31 pm: 4
oh. well, that’s dissappointing to hear. I was getting excited cause i just heard about this like 2 days ago.
Jan on May 7, 2009 at 7:02 pm: 5
Thanks for clearing this up. I guess no matter how hard we try, most people will believe these stories and pass it on without checking first.
Zorkon on May 24, 2009 at 10:40 am: 6
Go ahead and listen to the debunkers! By the time you realize Mars is continuing to approach Earth it will be too late! AH HAHAHAHAHAHAHAHA
Shepps on June 2, 2009 at 12:31 am: 7
Just when I thought the time will be right for me and Brain and Pinky to take over the world you have to tell me this. Well Brain, Pinky . . . it is back to the drawing board and revise a new plan to take over the world. Ha Ha Ha Ha Ha Ha HA HA HA !
susan on July 4, 2009 at 11:02 am: 8
yes i was just at my mates house and they saay that mars is going to be as big as the moon visible for all to see august 27 so for us her in pannawonica wa we will have a fab veiw
i thought i would check this out for the facts my self yeR!!!!! CANT WAIT TO SEE THIS BRING IT ON GET THE FACTS PEOPLE/////////????????????? bestr wishes susan
First line viewer on July 8, 2009 at 2:11 pm: 9
Would someone tell me if Mars will be closest to the Earth as it was when First World War and Second World War begins? It will be in August of this year or January 2010? Many thanks
Book on July 29, 2009 at 1:31 pm: 10
Everyone’s always believing incorrect information - even those of you who seem to be so disturbed by people believing the thing about Mars. What difference does it make? Why in the world would we all go searching on the internet for the “truth” of everything wehear about? Get a life and enjoy what you know and keep your mouth shut so others can enjoy the innocent information they have. Who’s it gonna kill anyway?
tere on August 4, 2009 at 2:00 am: 11
so then what is all the jive about the sun’s gravity changing, drawing all the planets closer??? then sending them out again??? I was told it only happens every 5 million years or so, and we are greatly privleged to have it happen this year. It was said to be on August 12, 2009.
Astroprof on August 4, 2009 at 3:51 pm: 12
Sorry, Tere, there’s nothing to that either. The Sun’s gravity won’t be doing anything unusual.
Ray on August 5, 2009 at 12:30 pm: 13
Zorcon……. you fool, that was funny mate
barbara in asheville on August 8, 2009 at 11:39 pm: 14
wow- i really thought it was going to happen and really bummed that it’s just a myth.
Tamatha on August 26, 2009 at 4:45 pm: 15
OMG.. why do i listen to other people, i wished i had cked this out before telling everyone they could come over, for a moon/mars party.
well i guess.. the party must go on !! i will print this out and get everyone ready for next yrs get together.