Comet 2020 F3 (NEOWISE) – Followup

   Here are two pictures of the comet after some processing and reduction in size.
   And the first of several pictures of Venus in transit across the Hyades open star cluster.

   
   
   

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Venus, the Bull, and a Comet (yes!)

   The next several days offer some exciting opportunities for viewing: a few of the visible planets; the waning phases of our Moon and a few conjunctions with stars and planets; Venus crossing the stars of the Hyades open star cluster; and Comet 2020 F3 (NEOWISE).
   Comet 2020 F3 (NEOWISE) is one of the many comets discovered by the NASA NEOWISE mission.
   NEOWISE is a space-based telescope used to find and track ‘Near Earth Objects’, comets and asteroids, that may pose a threat to our planet.
   Click on this link to go to the SkyLive web site for viewing information about Comet C/2020 F3 (NEOWISE).

   
   
   

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A Lunar Eclipse and 2 Planet Conjunction

   Our Moon reaches full phase on July 5th and will be rising around sunset local time. Two of the giant outer planets, Jupiter and Saturn will be passed by the Moon over a two day period. On the 5th the full Moon will be about 6-7o to the west from Jupiter. The next day, July 6th, the waning gibbous Moon will have passed the two planets and the Moon will about 1-2o from Saturn. Both days should prove to be ‘binocular-worthy’ with the morning of the 6th having the Moon the closest to the planets.
   There will also be a partial penumbral lunar eclipse however this type of eclipse has the Moon passing through the faint outer shadow cast by the Earth. Even a total penumbral lunar eclipse is barely noticeable so as a partial do not expect to see much change in the Moon’s brightness.

   
   
   

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Earth at aphelion – 2020

   Saturday July 4th, as the Earth continues its annual trek around the Sun, the Earth reaches a point in its orbit that is called aphelion. Aphelion is the greatest distance that separates the Earth from the Sun, and we are the furthest from the Sun for the year at this point in the orbit. So, at 12 UT (7 am CDT) on Saturday July 4th the Earth is 1.0167 AU (94,507,635 miles, 152,095,295 km) from the Sun.
   Approximately one-half year or one-half revolution earlier, on January 5th 2020, the Earth was at perihelion, its minimum distance from the Sun for this year at 0.9832 AU (91,398,199 miles : 147,091,144 km). This difference, about 3%, in distances is due to the shape of the Earth’s orbit being elliptical rather than circular. However the Earth has a mildly elliptically shaped orbit that is closer to being slightly out-of-round than the incorrect, very elliptical orbit that is often shown – like the illustration used here.
sun2014-ani   In Astronomy the shape of a planet’s orbit is called eccentricity, with 0 being a circle and 1 a straight line. Any value between 0 and 1 represents an ellipse. The shape of the Earth’s orbit is so close to being circular that the apparent size of the Sun does not appear to change as this animated graphic shows. The difference between perihelion and aphelion is about 3%.

   
   
   
   Eccentricity for each planet is listed below for comparison.

Planet	   Eccentricity	
Mercury	   0.2056
Venus	   0.0068
Earth	   0.0167
Mars	   0.0934
Jupiter	   0.0484
Saturn	   0.0542
Uranus	   0.0472
Neptune	   0.0086
Pluto	   0.2488

   To read more about the Earth’s orbit and get some teaching ideas click here to download a PDF copy of my January 2011 Scope on the Skies column Solar Explorations.
   

   
   
   

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July Moon at Descending Node

   Friday July 3rd the 11-day old waxing gibbous Moon crosses 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.

   On the date of the descending node the waxing gibbous Moon will be over the southern horizon around local time for sunset. Look for the Moon to be about 9-10o from the heart of Scorpius the Scorpion, the reddish star Antares.

   
   
   
   
   

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Mercury at Inferior Conjunction

   Wednesday July 1st the innermost planet Mercury reaches inferior conjunction. At inferior conjunction Mercury will move between the Earth and the Sun – much like the position of the Moon at new phase. The graphic to the right shows the planet positions relative to the Earth and Sun for both inner planets and outer planets.

   At this inferior conjunction Mercury will not be directly in line with the Earth and the Sun – on the ecliptic. Mercury has an orbital inclination of 7o with respect to the ecliptic. So like our Moon, Mercury during each complete orbit, will cross the plane of the ecliptic moving north (ascending node) and also moving south (descending node). For this inferior conjunction Mercury will be south of the ecliptic, by about 5.47o.

   
   
   

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June Moon at Perigee

   Our Moon reaches perigee, (closest to Earth), for this orbit, on Tuesday June 30th. At that time the Moon will be at a distance of 28.92 Earth diameters, 229,259 miles (368,958 km) from the Earth.

   On the day of the perigee Moon the 10-day old waxing gibbous Moon will be over the southeastern horizon around mid-evening.

   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)

   
   
   
   
   
   

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Virgo Spikes the Moon

   Our Moon, after traversing the boundaries of the constellation Leo the Lion, will then do a similiar crossing of the constellation Virgo the Harvest Maiden. Roughly midway across Virgo is the bright blue-white star Spica. From mythologies the star Spica represents a harvested bundle of grasses, maybe wheat or oats.
   On the evening of June 28th the Moon will be about 7o to the west from Spica, and the next evening, June 29th the Moon will about 9-10o to the east from Spica.

   
   
   

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Leo and the Moon

   The next several evenings, as our Moon waxes through its phases, the Moon will pass by some familiar celestial objects – stars, star clusters, and planets. They all have something in common, that being that these objects are near the ecliptic. Our Moon follows the ecliptic in a more or less parallel path assuming that parallel paths may be bent! The Moon’s orbit is inclined or tilted about 6o from the ecliptic meaning that the Moon will at times be above, below, or on the ecliptic.
   So with the above in mind on the evenings of June 24th and 25th the 3 to 5-day old waxing crescent Moon will be passing by the heart of Leo the Lion, the bright star Regulus. As you can see from the graphic above Regulus lies nearly on the ecliptic.

   
   
   

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Thin Moon on the Move

   Sunday June 21st, on the other side of the Earth from the U.S.A., the new Moon will be passing between the Earth and the Sun giving that side of the world an annular solar eclipse.
   About 1/2-day later the just past new Moon, an 0.80-day young thin waxing crescent Moon may be seen just above the western horizon at sunset local time. If you see the Moon look closely for a star-like object just to the left from the Moon. This is the inner planet Mercury.
   If you miss the Moon and Mercury on Sunday evening wait until Monday evening June 22nd to see the still thin 1.85-days old waxing crescent Moon near one of the Gemini ‘Twin’ stars, Pollux.
   Not had enough? On Tuesday June 23rd the 2.80-days young waxing crescent Moon will be near M44, the Beehive Cluster.
   Any of these conjunctions will look great in binoculars.

   
   
   

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