Tag Archives: science

June Moon at Perigee

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Our Moon reaches perigee, (closest distance from Earth), for this orbit on Friday June 23rd. At that time the Moon will be at a distance of 28.06 Earth diameters (357,937 km or 222,412 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*


   On the day of the perigee Moon the 28-day old very thin waning crescent Moon is above the eastern horizon about 30 minutes to an hour before the Sun rises. This perigee Moon is less than 16 hours before it reaches new Moon phase. The Dwarf Planet Ceres will not be visible but it is where the graphic indicates it to be.

   *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?”

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.

Mercury at Superior Conjunction

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mercury at superior conjunction
   Wednesday June 21st the innermost planet Mercury reaches superior conjunction – on the opposite side of the Sun from the Earth. For those that are curious, Mercury at superior conjunction is approximately 1.324 AU (123,073,489 miles; 198,067,580 km) from the Earth – the combined distance of the Earth to Sun distance plus the radius of Mercury’s orbit.
   Mercury is not visible while in conjunction with the Sun but within the next week or so Mercury will reappear on the east side of the Sun and start becoming visible over the western horizon at sunset.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

2017 June Solstice

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21june-ecliptic   Northern hemisphere spring comes to an end and its summer begins on Wednesday day June 21st at 4:24 UT (11:24 pm CDT Tuesday June 20th) when the Sun ‘reaches’ the celestial coordinates of 23.5o north declination and 6 hours right ascension. With respect to the Earth’s surface the Sun is described as over the Tropic of Cancer, 23.5o, north latitude of the Earth’s equator. At this same time the Sun is just entering the boundaries of the astrological constellation Cancer the Crab. Interestingly about 11 hours later, June 21st at 15 UT (10 am CDT) the Sun will actually be entering the region of the Gemini Twins as it crosses the boundary between Gemini and Taurus.
Just had to include this!!
   According to the pseudoscience of astrology the Sun, at this date, would be entering the astrological sign of Cancer the Crab.

   We know that it is the Earth’s orbital motion around the Sun that causes the sun’s apparent eastward motion among the stars in the background. This is how the Sun ‘reaches’ a celestial coordinate, how it ‘crosses’ the boundaries between constellations, or how it is ‘in’ a constellation.

   With respect to the southern hemisphere this is the end of their summer and start of their fall season. So thinking globally my preference has been to use the name of the month to designate the season change. Hence the use of the term June Solstice rather than summer solstice.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

Venus – Crescent Moon Conjunction

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   Tuesday morning June 20th the 25-day old waning crescent Moon will be about 6o from the inner planet Venus. At -4.6 apparent magnitude Venus contrasts well with the Moon’s -11 apparent magnitude.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

Neptune Backs Up

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Two days in a row! Like the song goes, “slow down you move too fast” – or proofread!!
   Friday June 16th the outermost of the 8 planets, Neptune, ends its westward retrograde motion around the Sun and will resume direct motion, moving eastward will come to an apparent halt in its eastward or direct motion and appear to start moving backward to the west in what is known as retrograde motion. In this graphic the location of the 21.5-day old waning gibbous Moon is shown to be about 2-3o from Neptune. Neptune has an apparent magnitude of nearly 8.0 making it all but only visible with telescopes – and certainly not on this date with -12th magnitude Moon nearby.

   Retrograde motion is an apparent motion that the outer planets, relative to the Earth, have. It is an apparent motion that looks as if the outer planet stops it normal direct motion to the east and reverses direction to the west. After a period of time the apparent westward motion ends and the planet resumes its normal orbital path to the east. Retrograde motion happens as the faster moving Earth catches up with and then passes by the outer planet. It is during this time that the backward apparent motion happens.

   The two inner planets also have retrograde motion but it is a result of their orbit around the Sun and not the Earth passing them by. For approximately one-half of their orbit they move east, from western elongation through superior conjunction to eastern elongation. Then at eastern elongation the inner planet starts moving westward through inferior conjunction to western elongation.

   Read a little more about retrograde motion in my February 2012 Scope on the Skies column, drawkcab planets, in Science Scope Magazine.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

June Moon at Descending Node – Conjunction with Neptune

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My Bad! This should have been about Friday the 16th.
2jan-descending-node
   Thursday June 15th the 21.5-day old last waning gibbous 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.
   


   On the day of the node crossing the waning gibbous Moon will be over the southeast horizon at around 2 am CDT. The Moon will be in conjunction, and within about 2o from the outermost, (8th), planet Neptune.
   
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.

ISS Followed the Arc

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   Last evening, Sunday June 11th the ISS, International Space Station orbited over my part of the world. The ISS appeared about 45o above the west-northwest horizon and followed a path that went below the bowl of the Big Dipper and in a straight line ‘followed the arc to Arcturus’ in the constellation Bootes the Herdsman. At its peak the ISS reached nearly the zenith and at its brightest had to be at least -3.0 in apparent magnitude. After a several minutes the ISS moved out of sunlight and faded from view above the southeastern horizon.
Camera settings were 18mm; ISO 800; F4.0; 2 sec.
   One dependable and accurate source of viewing information for the ISS is at NASA’s ISS Sightings web site. Here you may learn the time and direction the ISS will appear, its duration of visibility, and its time and direction it will stop being visible.

   In a similar manner the Heavens Above web site will also provide viewing information for the ISS but in addition it will display a star map showing the path across the sky. This sample graphic shows the ISS path for June 12th.

   Want to see what the Earth looks like from the ISS? Click on this link to go to the ISS HD Earth Viewing web site for a view from one of several cameras mounted on the ISS as this screen capture shows. There are two additional maps that show the current position and orbital path of the ISS.
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.