Mars as Big as the Full Moon – But Only on Internet

   Tuesday July 31st the outer planet Mars will be at its closest to the Earth – this time around. Coincidentally this is 4 days after Mars was at opposition, and about 3 weeks after Earth was at aphelion. However this is not the closest Mars has been from the Earth. The closest, so far, was during August 2003.

A Martian Urban Legend
   “This year, during August, Mars will be at its closest to the Earth; so close, in fact, that it will appear as large as the full Moon.”
   Have you heard this urban legend before? Since 2003, emails describing this myth have circulated the internet usually during July or August. It all started during the opposition of August 2003 when Mars was about as close as it can ever be to the Earth (55,755,723 km – 34,645,000 miles) in a 20-year cycle of varying distances at opposition. Since then, usually around August, misinformation about the appearance of Mars circulates around the internet.

   In the time that it takes the Earth to catch up with and move into an opposition position, the outer planets have also been moving eastward relative to the stars in the background. Over time, the constellation where the outer planet is located during opposition and its retrograde loop gradually shift to the east. An opposition is also near the time when the distance between the Earth and an outer planet is around the minimum distance. Keep in mind that because the shape of the orbit is elliptical, this minimum distance will be different each time.

   However, there is an even more conclusive way to show that Mars could never be so close that it would appear as large as the Moon. To see how requires and some basic arithmetic. You will see that Mars could not appear to be as large as our Moon unless some force somehow caused Mars to change its orbital position and literally move closer to Earth.

   On July 31st, Mars will be 57,595,180 km (35,787,986 miles) from Earth. Mars is 6,792 km (4,220 mi.) in diameter. The Moon is 3,475 km (2,159 mi.) in diameter and is an average 384,400 km (238,900 mi.) from Earth. In terms of apparent size our Moon has an angular diameter of 0.5o (30 arc minutes or 1800 arc seconds), while on July 31st Mars has an apparent diameter of 24 arc seconds.
    So with the following calculation using those values (24 / 1800) x 100% = 1.3%) Mars is only 1.3% the apparent size of our Moon.

   Another method to calculate how large Mars will appear as compared to the Moon:
   (Mars’s diameter ÷ Mars’s distance) ÷ (Moon’s diameter ÷ Moon’s distance)

         (4220 / 35787986) / (2159 / 238900) = 0.013 = 1.3%
    In other words, Mars on 31 July will be only 1.3% of the apparent size of the Moon.

   
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Mars at Opposition – 2018

Mars at Opposition   Friday July 27th Mars will reach a point in its orbit around the Sun where it is at opposition relative to the Earth. at opposition The Earth is between the Sun and Mars, or any of the outer planets. At opposition both the Earth and the planet at opposition will have near identical heliocentric longitude. The opposition of Mars sometimes happens around the time that Mars is at its respective perihelion, closest to the Sun. If opposition happens during or near when the Earth is at its respective aphelion, furthest from the Sun, (first few days of July) then Mars will appear larger relative to when these dates are further apart.

What is opposition?
orbital-positions   The outer planets reach opposition when the Earth has moved into a position with the Sun on one side and the outer planet on the other side. Because all planets orbit in the same direction (toward the east), and all follow orbits that are slightly more elliptical than circular, oppositions occur at regular intervals of about 12 months (except for Mars). Mars is considerably closer to Earth and is moving faster than the other outer planets, so it takes approximately 26 months for Earth to catch up with Mars for an opposition.

   
   
   

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July Full Moon at Apogee, Descending Node, A Lunar Eclipse, and Conjunction with Mars

Apogee Moon
   Our Moon reaches apogee, (greatest distance from Earth), on Friday July 27nd. At that time the Moon will more or less be at a distance of 31.84 Earth diameters (406,223 km or 252,415. miles) from the Earth.
   Does our Moon actually go around the Earth as this graphic shows? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*
*Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)
Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”

Descending Node
   Friday July 27th the full Moon will be crossing the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic.

Total Lunar Eclipse
   When the Moon crosses the ecliptic, a node crossing, and the Moon is either at full or new phase there will be an eclipse. The length of the eclipse and whether or not it will be partial or total depends upon the timing. The closer the two events are to each other the greater the eclipse. This total lunar eclipse will be a long one at nearly 2 hours for totality. However the eclipse will not be visible from North America.
   Get eclipse information from the Hermit Eclipse web site.
   Watch the Lunar Eclipse live. Webcast hosted by the Bareket Observatory in Israel. Webcast starts at 18:30 UTC (1:30 pm CDT).

Conjunction
   On the day of the apogee and descending node the full Moon will be over the southern horizon and within about 6-7o from the planet Mars.

   
   
   

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Moon-Saturn Conjunction

   Tuesday evening July 24th the 12-day old waxing gibbous Moon will be within about 2o from the planet Saturn. To west from Saturn is the planet Jupiter and further west over the southwestern horizon is the inner planet Venus. To the east from Saturn is Dwarf Planet Pluto and just rising in the east is the planet Mars.

   The two, Moon and Saturn, should make a fine sight through binoculars or a low power wide-field telescope eyepiece. They are located in an area of the Milky Way rich with deep-sky objects like M-8, the Lagoon Nebula. Unfortunately the reflected light from the Moon drowns out the dimmer deep-sky objects. However a few days from now the Moon will be rising later and will not interfere with seeing some of these objects.

   
   
   

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Sun is Not in Leo the Lion

   According to the pseudoscience of astrology, Sunday July 22nd the sun will be entering the constellation of Leo the Lion. In fact the Sun is still within the boundaries of the constellation Cancer the Crab, having just entered that region one day ago.
   The difference between the two locations of the Sun, the correct astronomical vs. the incorrect astrological, is due to the effects of precession, or more specifically, the precession of the Earth’s axis. The Earth wobbles on its axis like a spinning top does as the top slows down. So, in approximately 26,000 years the Earth will have spun, or wobbled one time. This is a repetitive cycle and over the course of one precession cycle the poles of the Earth trace out a circle against the background stars over their respective pole. any star on or nearest to this precession circle is the pole star. Currently the north pole of the Earth points toward Polaris and within this century, due to precession, will point the closest it will be, and then over time the Earth’s north pole will shift away.
   Another effect of precession has been to cause the celestial grid system to shift moving the original signs of the zodiac by at least one constellation to the west. In other words the Sun is more to the east which in effect means that whatever your zodiacal sign may be according to astrology, you are really the constellation to the west, or before it according to Astronomy.
   Click here to read a little more about precession from a previous blog.
   The Science of Astronomy has its roots in astrology with the origins of astrology beginning several millennia ago possibly by the Babylonians. Regardless of its origins the basis for at least Sun astrology, the popularized version printed in newspapers, is the position of the Sun relative to stars in the background. However we now know that due to the effects of precession the Sun’s position is no longer as it was during the beginnings of astrology.
    The slideshow below shows the sun’s position within Cancer on July 22nd 2016 AD, and then shifts to show the sun in Leo 4,000 years ago on 22 July 2016 BC. Precession has shifted the sun’s position one constellation to the west.

   
   
   

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Sun Does Enter Cancer the Crab

19july-view-from-earth   Saturday day July 21st the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation Gemini the Twins and into the constellation of Cancer the Crab. This is the true or actual position of the Sun as opposed to the pseudoscience of astrology which usually has the astrological Sun one constellation ahead or east from the Astronomical Sun’s position.

   Read a little more about how astrology has the Sun incorrectly placed in a previous blog, and in another blog discussing the effects of precession.
   
   
   

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Moon – Jupiter Conjunction

   Friday evening July 20th the 8-day old waxing gibbous Moon will be 3-4o from the ringed planet Jupiter. Joining Jupiter to the west is Venus, and east from Jupiter are the planets Saturn and Mars.
   Close to Jupiter is 3rd magnitude star Zubenelgenubi in Libra the Scales.

   
   
   

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Planet-A-Palooza plus the Moon

   This is one of those ‘best of times’ with regard to planet viewing. All of the visible planets are above the horizon although Mercury sets just before Mars rises. Times like this make it easy to visualize the ecliptic and its relationship with the planets. And our Moon, as it waxes toward full phase over the next several days, will pass by several planets and dwarf planets.

Click on a graphic to start a slide show.

   
   
   

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Moon in Conjunction with Venus


   Sunday evening July 15th the 3-day young waxing crescent Moon will be 2o from Venus, and 5o from the star Regulus in Leo the Lion. Further to the east are the planets Jupiter, Saturn, and Mars.


   The three, Moon, Venus, and Regulus, all fit comfortably within a binocular field of view.

   
   
   
   
   
   
   
   
   

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Circumstances for a Solar Eclipse


   Friday July 13th and Saturday the 14th circumstances are such that there will be a partial solar eclipse that will be best viewed from along the northern coast of Antarctica. (hey! every Antarctic coast is a northern coast!!
Specifically the partial solar eclipse will be visible at around 129o E near the Claire Coast.

   Circumstances for a solar eclipse, like for a lunar eclipse, require the Moon to be at either its ascending node or its descending node and be at or close to either new or full Moon phase. A node crossing occurs when the Moon with an orbit tilted 6o from the ecliptic (the Earth’s orbit) intersects the ecliptic.


   The Moon has an elliptically shaped orbit so if the timing for lunar apogee (furthest from Earth) or perigee (closest to the Earth) happens around a new Moon at a node crossing then the apparent size of the Moon will be anywhere from smaller to larger than the Sun’s apparent size. Smaller means a longer eclipse including the length of totality.


   
   
   However the bottom line is the timing between the node crossing and new Moon. This time the Moon crosses the ecliptic moving north, ascending node, approximately 24 hours after new Moon phase setting up a partial solar eclipse.

So what are the circumstances?
Times are in Universal Time (CDT = UT-5)
   July 13th
   1:48 UT – Partial Solar Eclipse Begins
   2:48 UT – New Moon — Partial Solar Eclipse
   3:01 UT – Mid-Eclipse (maximum Sun covered)
   4:13 UT – Partial Solar Eclipse Ends
   8:27 UT – Moon at Perigee – 357, 432 km (222,098 miles)
   July 14th
   2:52 UT – Moon at Ascending Node

   
   
   

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