Mars – Saturn at Heliocentric Opposition


   Monday May 1st the planets Mars and Saturn will have reached a point in their respective orbits where they are on opposite sides of the Sun and are approximately 180o apart, or at what is called heliocentric opposition. Using the system of heliocentric longitude Mars has a heliocentric longitude of 83o while Saturn has a heliocentric longitude of 263o

   Mars is visible above the western horizon at around sunset local time near the two open star clusters of Taurus the Bull – the Pleiades and the Hyades. On the other side of the sky, over the eastern horizon is Saturn, rising around midnight local time.

   
   
   

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 Shines Brightly

   What is that really bright star over the eastern horizon in the hours before sunrise? That is the inner planet planet Venus, and on Sunday April 30th Venus will reach a point in its orbit around the Sun where it appears at its greatest illumination. Shining at an apparent magnitude of around -4.53 Venus is bright enough to drown out most of the stars in the constellation of Pisces the Fishes that surround Venus.
   How Venus gets this bright is a result of its orbit around the Sun and its position relative to the light from the Sun and us on Earth. Venus is currently about as close to the Earth as it can come and because it is between us and the Sun Venus goes through phase changes like our Moon. Except we cannot see a full Venus because that is when Venus is at superior conjunction, on the opposite side of the Sun.
   Venus was recently at inferior conjunction and is now moving along its orbit toward the west away from the Sun. From inferior conjunction, for a while, Venus will appear as a large crescent shape but as days pass it moves further away, grows smaller in apparent size, and increases, waxing, toward a small gibbous phase before it moves behind the Sun and superior conjunction.

   
   
   

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.

April Moon at Perigee

   The Moon reaches perigee, (minimum distance from Earth), this month on Friday March 3rd. At that time the Moon will more or less be at a distance of 28.17 Earth diameters (359,327 km or 223,275 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 1.5-day young thin waxing crescent Moon is above the western horizon at sunset local time and is near Dwarf Planet Ceres and the Pleiades open star cluster.

   *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.

Crescent Moon Near Venus

   Sunday morning April 23rd the thin 26-day old waning crescent Moon will rise to right, west, from the inner planet Venus. The two will be about 6o apart and will easily fit within the field of view of 7×50 binoculars.

   
   
   

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.

April Moon at Descending Node

2jan-descending-node   Friday April 21st the 24-day old waning crescent 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 24-day old waning crescent Moon will be over the southeast horizon at sunrise local time. The graphic includes the ecliptic and other planets so you can see the relationship between planets, the Moon, and the ecliptic. At times like this, with several planets arranged across the sky it is easy to visualize the ecliptic.   
   
   

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 Inferior Conjunction

orbital-positions   Thursday April 20th 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.

mercury at inferior conjunction   While 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). In this situation Mercury is north of the ecliptic and 6 days away from its descending node on April 26th.

   
   
   

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.

Sun Not in Taurus

April 19th  According to the pseudoscience of astrology the Sun enters the constellation of Taurus the Bull on Wednday April 19th. When in fact the actual position of the Sun on the 19th is still within the boundary of the constellation of Aries the Ram, as this graphic shows. Actually the Sun had just entered Aries the day before on April 18th.

   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.
   
   
   
   
   
   

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.

Sun Enters Aries

April 19th   Tuesday April 18th 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.
   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.
   
   
   


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.

Moon Near Saturn


   Sunday morning, April 16th the 19-day old waning gibbous Moon will rise near the planet Saturn. The two will be within the 7o field of view of 10×50 binoculars and will be easily seen over the eastern to southeastern horizon in the hours before the sun rises.
   
   
   

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.

April Moon at Apogee

 Our Moon reaches apogee, (greatest distance from Earth), on Saturday April 15th. At that time the Moon will more or less be at a distance of 31.78 Earth diameters (405,475 km or 251,950 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?”

click on graphic to see it larger   On the morning of the apogee Moon the 18-day old waning gibbous Moon rises a couple of hours before the Sun and is visible over the southern horizon.

   
   
   

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.