Luna and the Sisters

Click on the graphic to see it full size.

Click on the graphic to see it full size.

   Around sunset on Wednesday evening, 30 April, look toward the western horizon for a thin, nearly 2-day old, waxing crescent Moon to be positioned between two open star clusters in Taurus the Bull. Slightly up and to the right are the small dipper-shaped stars of the 7 Sisters – the Pleiades. A little up and to the left from the Moon are the V-shaped stars forming the face of Taurus the Bull – the Hyades.

   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

New Moon at Descending Node=Solar Eclipse

annular-eclipse-img   Monday morning, 28 April, at 6:37 am CDT (11:37 UT) the waning but nearly new 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 has with the plane of the ecliptic. The plane of the ecliptic, or just ‘the ecliptic’ in reality is the Earth’s orbital path around the Sun.
29april-annular_eclipse-ani   Coincidentally the time for new Moon is 1:17 am CDT (6:17 UT) 29 April, and when the time for these two events, node crossing and new Moon or full Moon, is this close we have a solar eclipse. This time around we have an annular eclipse that unfortunately is best viewed (if possible) from a rather remote area of the world – Antarctica.
   An annular solar eclipse at new Moon phase occurs with the same arrangement for a total solar eclipse at new Moon phase with the difference being that with an annular eclipse the Moon is further from the Earth. This results in the Moon having a smaller apparent diameter then the Sun, and so at mid-eclipse the disk of the Moon does not completely cover the sun’s disk. This leaves a ‘ring of fire’, the annulus, around the Moon.
   How does the Moon get further from the Sun is explained by knowing the Moon’s orbital path is elliptical rather than circular so its distance from the Earth at various phases varies. See a recent post about the Moon at perigee for more about this.

Click here to see eclipse information from NASA. (PDF)

   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Venus Gets the Hebe (Jeebees)!

Click on graphic to see it full size.

Click on graphic to see it full size.

   Yeah, I know that title is a bit of a stretch but what the heck! How often will a bright planet like Venus come close to an asteroid? Especially one named Hebe (pronounced ‘heebee’). So, tomorrow morning, Sunday the 27th, Venus will be within two degrees from asteroid 6 Hebe as this graphic shows. The contrast in apparent brightness between these two is considerable however. Venus has an apparent brightness (magnitude) of -4.1 compared with Hebe’s +9.4.
   Asteroid 6 Hebe is the 5th brightest asteroid and was the 6th asteroid to be discovered (1847). It is an elongated or potato shaped asteroid with an average diameter of approximately 115 miles (185 km). From mythology Hebe is the Goddess of Youth, young folks, rather than a goddess with powers to make someone younger.

   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

The Sides Point the Way

moon-venus-ani   Before sunrise this Friday and Saturday morning look for a thin waning crescent Moon to be near the planet Venus. The corner stars for the asterism “the Great Square” of Pegasus have been labeled to show how the Moon and Venus are sort of lined up with the right side of the square on Saturday and then with left side on Saturday.
    As these two graphics show the Moon will be to the west (right) from Venus on Friday and then to the east (left) of Venus on Saturday morning.

   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

April’s Perigee Moon

22apr-perigee_moon    Our Moon orbits around the Sun with the Earth and 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*.
   The 22.86 day old waning Crescent Moon reaches perigee this month, Tuesday 23 April at 00:22 UT (7:22 pm CDT 22 April). At that time the Moon will more or less be at a distance of 29.98 Earth diameters (369,349 km or 229,503 miles) from the Earth.

   *Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

Click on graphic to see it full size.

Click on graphic to see it full size.

   Tuesday morning, 23 April, the waning crescent Moon will be close to Comet C/2012 Linear X1, however at 11th magnitude the comet is too dim for viewing and especially so close to the much, much brighter crescent Moon.
   
   
   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Sun Not In TaurusToday

The View from Earth 19 April

The View from Earth 19 April

  According to the pseudoscience of astrology the Sun enters the constellation of Taurus the Bull today, 19 April at 11 pm CDT (20 April 4 UT). When in fact the actual position of the Sun today is within the boundary of the constellation of Aries the Ram, as this graphic shows. Actually the Sun had just entered Aries 2 days ago.

   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.
   
   
   
   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Sun Enters Aries Today

view-from-earth-19april   Today Friday 18 April at 11 pm CDT, (Saturday 19 April 4 UT), the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation Pisces the Fishes and into the constellation of Aries the Ram. 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. Coincidentally this happens tomorrow when according to astrology the Sun enters Taurus the Bull.

   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.
   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Moon Near Saturn

moon-saturn-ani   Wednesday evening, 16 April, the waning gibbous Moon rises about 1 degree from Saturn, at least as viewed from my location in Missouri. For some parts of the viewing world this will be an occultation, where the Moon passes between Saturn and your view from Earth. Regardless of how close the two will be from your location the two will traverse your horizons during the night hours and be over the western horizon at your local time for sunrise. What is interesting is how the two shift positions during the hours they are above the horizon. This animated graphic is set to 0.5 second per hour.

   Click here to see a graphic showing the setting Moon and Saturn Thursday morning.

   
   
   
   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Earth Eclipses Mars Tonight!

lunar-mars-eclipse1
lunar-mars-eclipse
    Hard to believe that a major news organization can get something this incorrect! The two pictures are screen grabs from the video clip. The use of Mars starts right around the 50 second mark.
Click here to watch the video clip on the Today Show web site.

   
   
   
   
   
   
   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Mars Closest to Earth-This Time Around

   Monday 14 April not only includes the start of a Lunar Eclipse (depending on the time zone), two asteroids at or near opposition, Mars just past its opposition, Comet PanSTAARS 2012 K1 at opposition, Dwarf Planet Pluto begins retrograde motion, and at 8 am CDT (13 UT) Mars will at its closest to the Earth for this particular orbit. At that time the separation between Earth and Mars is 0.618 AU (57,446,689 miles – 92,451,484 km).
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.
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.

Mars at the April 2014 and May 2016 Oppositions.

Mars at the April 2014 and May 2016 Oppositions.

   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. Since opposition for Mars is during April this year rather than in August as it was for the 2003 opposition, this should dispel the urban myth that appears every July or August since the August 2003 opposition.
   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 use this year’s closest approach on 14 April 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 14 April 2014, Mars will be 92,385,661 km (57,405,788 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. To calculate other dates, use the distance (km) values from the table below and the following formulas:

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

   To calculate how close Mars would have to be to appear as large as the full Moon:
   (Mars’s diameter × Moon’s diameter) × Moon’s distance

Seven oppositions of Mars showing the distance when closest to Earth 
Date of opposition         Date closest to Earth       Distance (AU)  Distance (km)  
August 28, 2003            August 27, 2003                0.37272      55,758,118  
November 7, 2005           October 30, 2005               0.46406      69,422,387  
December 24, 2007          December 28, 2007              0.58935      88,165,505  
January 29, 2010           January 27, 2010               0.66398      99,329,994  
March 3, 2012              March 5, 2012                  0.67368     100,781,093  
April 8, 2014              April 14, 2014                 0.61756      92,385,661  
May 22, 2016               May 30, 2016                   0.50321      75,279,144  

   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.