The Solar System in April

NZDT ends on the morning of Sunday 5 April, clocks being set back an hour at 3am.

Dates and times are NZDT (UT +13 hours) up to April 4 and NZST (UT + 12 hours) from April 5 unless otherwise specified. Rise and set times are for Wellington. They will vary by a few minutes elsewhere in NZ.

Sunrise, sunset and twilight times in april

                     April  1  NZDT                 April 30  NZST    
                    morning  evening               morning  evening   
           rise:   7.33am,  set: 7.15pm     rise: 7.03am,  set: 5.31pm
Twilights                                                             
 Civil:    starts: 7.08am, ends: 7.41pm   starts: 6.38am, ends: 5.58pm
 Nautical: starts: 6.36am, ends: 8.13pm   starts: 6.05am, ends: 6.31pm
 Astro:    starts: 6.04am, ends: 8.45pm   starts: 5.33am, ends: 7.03pm

April PHASES OF THE MOON (times as shown by GUIDE)

  Full moon:     April  5 at  1.06 am (Apr  4, 12:06 UT)
  Last quarter:  April 12 at  3.44 pm (        03:44 UT)
  New moon:      April 19 at  6.57 am (Apr 18, 18:57 UT)
  First quarter: April 26 at 11.55 am (Apr 25, 23:55 UT)

Total eclipse of moon.

The moon will be totally eclipsed on the night of April 4 to 5. The entire event is visible from New Zealand and from eastern and central Australia. From Perth in Western Australia the moon rises about 15 minutes before the start of the initial umbral phase. The total phase of the eclipse is very short, lasting 7 minutes 21 seconds from 12:56:55 am to 1:04:16 am NZDT (11:56:55 to 12:04:16 UT). The northern limb of the moon is only just inside the umbra at totality, so is likely to remain quite brightly lit.

The moon enters the umbra at 11:15:30 pm and leaves it again at 2:46:16 NZDT. The penumbral phases, during which little change in the moon will be noticed, starts at 10:01:07 pm and ends 3:59:29 am NZDT. Note that strictly NZDT reverts to NZST at 3:00 am, before the end of the eclipse.

The planets

Mercury, Mars and Uranus are all too close to the Sun to observe. Venus gets a little higher in the evening sky, Jupiter is prominent in the first part of the evening but gets low by late evening setting just before midnight by the 30th. Saturn is best viewed late evening and through the morning before sunrise.

Mercury is at superior conjunction with the Sun on April 10 at about 3 pm. Following conjunction Mercury will become an evening object. By the end of April it will set some 45 minutes after the Sun, so is not likely to be visible.

At conjunction Mercury will be 200 million km from the Earth, 50 million km beyond the Sun. At its closest it would appear to be just over half a degrees from the southern limb of the Sun, an angle about equal to the Sun's apparent diameter.

Venus gets a little higher in the western sky following sunset during April. On the 1st it sets some 90 minutes after the Sun, increasing to just over 2 hours later on the 30th. Even so Venus will be fairly low to the northwest soon after sunset.

The planet starts the month in Aries, moving into Taurus on the 7th. On the 11th and 12th it will be about 2.5° above the Pleiades. By the end of April Venus will be 3° from the star beta Tau, magnitude 1.7

The crescent moon will be a few degrees from Venus on the evenings of the 21st and 22nd of April. The moon will be to the left of the planet on first evening and above it the following evening.

Mars sets 45 minutes after the Sun on April 1; only half an hour after later on the 30th. With a magnitude 1.4 it is not likely to be visible. Following sunset, Mars will be in a direction about half way round from west to northwest.

Jupiter will be easily visible during the earlier part of the evening but will get low by late evening early in the month and by mid evening at the end of April. By then it will set just before midnight.

During April the planet is in Cancer. It is stationary on the 9th so shows very little change in position relative to the stars all month. On the 26th the moon, just past first quarter, will be some 6° to the left of Jupiter, the moon getting slightly closer to the planet as the evening progresses.

Mutual events of jovian satellites

There are about 10 mutual events of Jupiter's Galilean satellites observable from NZ during April. Now Jupiter is visible in the evening sky, some of these take place at a more convenient time. They include:

April 2, Callisto occults Ganymede mid event ca 10.48pm NZDT (9:48 UT). The two merge ~10 minutes earlier and separate ~10 minutes later. The two moons will be well out from Jupiter with Europa between them and the planet. Io will not be visible, being in eclipse in Jupiter's shadow. April 3, Io eclipses Europa. Maximum eclipse at 11.09pm (10:09 UT) The eclipse lasts in all 5 minutes, the magnitude change is 0.7. Europa will be close to Jupiter's limb, Io a little further out. April 8, Ganymede occults Callisto, mid event 8.08 pm NZST (08:08 UT) The occultation lasts some 6.5 minutes in all. The two moons will be some distance from Jupiter with Io and Europa on the other side of the planet. April 23, Europa occults Io, mid event ~8.18 pm. The occultation lasts some 3.3 minutes in all. Io and Europa will be about 1.5 Jupiter diameters from the planet, Ganymede and Callisto will be further out on the same side of Jupiter. April 27, Ganymede occults Callisto, mid event ~10.13 pm. This is a fairly long occultation lasting some 25 minutes in all. The two moons will be several diameters from Jupiter with Io between them and the planet. Europa will be on the opposite side of Jupiter

Useful observations and timings of these events can be made by those set up for the video observation of minor planet occultations.

Users of Dave Herald's Occult program can generate their own predictions of these and other events. Hristo Pavlov's Occult Watcher programme will also list them and has diagrams showing the satellites relative to Jupiter. Details can also be found on the IMCCE web site, http://www.imcce.fr/phemu/ where predictions and requirements for observing and reporting information are available.

Saturn rises at 9.39 pm on April 1, 6.41 pm, 70 minutes after sunset, on April 30. The planet is in Scorpius moving slowly to the west. By the end of April it will be just over a degree from beta1 Scorpii (mag 2.6) and a little under 10° from Antares.

On the 8th the 86% lit moon will be less than 3° from Saturn, the two being closest about 1am on the 9th.

At present Saturn's north pole is tilted 25° towards the Earth. This brings the northern surface of the rings well into view. They should be visible in binoculars, although a small telescope is likely to give a better view.

Outer planets

Uranus is at conjunction with the Sun on April 7. Consequently it is close to the Sun all month and not likely to be observable. After conjunction Uranus becomes a morning object. By the end of April it will rise nearly 2 hours before the Sun.

Neptune is a morning object during April. It rises about two and three quarter hours before the Sun on the 1st and just over 5 hours earlier than the Sun on the 30th. It is in Aquarius at magnitude 7.9

During April Neptune is overtaken by the faster moving asteroid Vesta. The two are closest on the morning of April 17 when Vesta, magnitude 8.0, will be 2.6° to the upper right of Neptune.

Pluto is in Sagittarius rising near 12.30 am on the 1st and nearly 2 hours earlier on the 30th. Its magnitude is 14.4.

Brighter asteroids:

(1) Ceres is a morning object in Capricornus with magnitude 9.1. During the month it moves to the east across Capricornus. On the 1st it rises about 1.20 am. By the 30th it will be rising late evening just before 11 pm.

(4) Vesta is also a morning object, at 8.0 it is a magnitude brighter than Ceres. Vesta will be in Aquarius rising just after 4 am on the 1st and a little before 2.30 am on the 30th. It passes Neptune mid April.


 


The fololwing table lists various solar system object events during April. A list of astronomical terms used in may be found after the table.

April 1 Moon at apogee
April 4 Moon full Eclipse
April 5 Spica 3.3 degrees south of the Moon
April 6 Uranus at conjunction
April 8 Mercury 0.5 degrees south of Uranus
Saturn 2.1 degrees south of the Moon
Jupiter stationary
April 10 Mercury superior conjunction
Moon southern most declination (-18.3 degrees)
April 11 Pluto 3.2 degrees south of the Moon
April 12 Moon last quarter
April 15 Neptune 3.4 degrees south of the Moon
April 17 Moon at perigee
Pluto stationary
April 18 Uranus 0.1 degrees north of the Moon Occn
Moon new
April 19 Mercury 3.4 degrees north of the Moon
Mars 3.0 degrees north of the Moon
April 21 Aldebaran 0.9 degrees south of the Moon Occn
April 22 Mercury 1.3 degrees north of Mars
Moon northern most declination (18.3 degrees)
April 25 Moon first quarter
April 26 Jupiter 5.3 degrees north of the Moon
April 28 Regulus 3.8 degrees north of the Moon
April 29 Moon at apogee
  • apogee: Furtherest point in the orbit of a body orbiting the Earth
  • conjunction: Two astronomical objects are 'lined up' (have the same right ascension) when viewed from Earth. If only one object is mentioned the Sun is generally the other object.
  • declination: 'Latitude' for celestial objects. The distance in degress above (north) or below (south) the celestial equator.
  • perigee: Nearest point in the orbit of a body orbiting the Earth
  • superior conjunction: Conjunction where the Sun is between the Earth another solar system object

January Moon & Planet data for 2015


All dates and times are NZDT (UT +13 hours) unless otherwise specified. Rise and set times are for Wellington. They will vary by a few minutes elsewhere in NZ.

SUNRISE, SUNSET and TWILIGHT TIMES in JANUARY                         
January  1                  January 31         
morning      evening         morning        evening    
Sun         rise: 5.48am,  set: 8.59pm      rise: 6.22am,  set: 8.45pm
Twilights                                                             
Civil:    starts: 5.17am, ends: 9.31pm    starts: 5.54am, ends: 9.14pm
Nautical: starts: 4.34am, ends:10.14pm    starts: 5.15am, ends: 9.52pm
Astro:    starts: 3.43am, ends:11.04pm    starts: 4.33am, ends:10.34pm

The Earth is at perihelion, its closest to the Sun for the year, on January 4 when it will be 0.983 Astronomical Units, 147 million km, from the Sun.

January Phases of the Moon (times as shown by guide)    
Full Moon:     January  5 At  5.52 Pm (        04:52 Ut)
Last Quarter:  January 13 At 10.47 Pm (        09:47 Ut)
New Moon:      January 21 At  2.14 Am (Jan 20, 13:14 Ut)
First Quarter: January 27 At  5.48 Pm (        04:48 Ut)

The Planets in January

Venus and Mars are visible for a short time after sunset. Mercury will also be close to Venus in the first part of the month, but will be lost to view by about the 20th. Jupiter rises in the opposite side of the sky a little later in the evening at first. It rises at sunset at the end of January. Saturn remains a morning object although rising earlier as the month progresses.

MERCURY will be briefly visible in the evening sky, near Venus, during the first half of January. It will set just over an hour after the Sun up to mid January. During the first part of January, Mercury will gradually move closer to Venus as they both move to the east through the stars. They are less than 1° apart from the 8th to the 13th. But Mercury will never quite catch up to Venus as its motion slows. With a magnitude of -0.7 Mercury will be easy to see, especially in binoculars, to the lower left of the much brighter Venus.

After mid January Mercury will fall behind Venus again as the innermost planet's motion drops away. Mercury is stationary on the 14th when it stops moving to the east. It will then be 19° east of the Sun. Over the next few days the planet will move increasingly rapidly to the west and towards the Sun, until it is at inferior conjunction between the Earth and Sun on the 30th. At conjunction it will be nearly 3.5° north of the Sun; the planet will be 98.6 million km, 0.659 AU, from the Earth and half this distance from the Sun.

Obviously Mercury will be lost to view several evenings before conjunction.

VENUS is also an early evening object, setting just over an hour after the Sun all month. It starts January in Sagittarius but moves into Capricornus on the 3rd and on into Aquarius on the 25th. On the 22nd the brightest star in Capricornus, delta Cap mag 2.85, will be 1° above Venus.

By the end of the month Venus will be 10° to the lower left of Mars. As noted above, Venus and Mercury will be close during the first half of the month, less than 3° apart up to the 18th. Mercury will always be to the lower left of Venus and visible before any star.

On the evening of the 22nd the 5% lit crescent moon will be 7° to the lower right of Venus. The moon will set about 50 minutes after the Sun, so will be very low.

MARS is the third early evening planet of the month. It sets about two and a quarter hours after the Sun on the 1st, but only 90 minutes later on the 31st. Thus it will gradually get a little lower during the month. Mars starts January in Capricornus but moves on into Aquarius on the 9th.

In Aquarius Mars will catch up with and pass Neptune which moves much more slowly. The two will be closest on the 20th when Neptune will be only 20 arc-minutes (two-thirds the diameter of the full moon) below and a little left of Mars. Neptune's magnitude will be 8.0. Thus it should be readily visible in binoculars once the sky is sufficiently dark. There are no stars between the planets likely to be mistaken for Neptune. But the two planets will be low with an altitude of only 6° one hour after sunset. On the 19th Mars will be 40 arc-minutes left of Neptune, on the 21st, 1° to its upper right.

On the 23rd the moon, the crescent now 11% lit, will be just over 5.5° to the lower right of Mars.

JUPITER rises 2 hours after sunset on the 1st and at the time of sunset on the 31st. Thus it is the fourth planet visible in the evening sky, albeit later than the other three. It will spend the month moving slowly to the west through Leo, situated 8 to 12° to the left of Regulus, magnitude 1.4.

The 90% lit waning moon passes Jupiter on the 8th when the moon will be 5° to the upper right of the planet as seen late evening shortly after they rise.

Mutual Events of Jovian Satellites

There are about 26 mutual events of Jupiter's Galilean satellites observable from NZ during January. The events involve either occultations or eclipses of one satellite by another. Visually, mutual occultations are the more interesting to watch as satellites can be seen to merge and separate over a period several minutes. Eclipses are normally partial events with fairly small magnitude changes of the eclipsed satellite. Consequently they are mostly difficult to detect visually. Total eclipses are rare.

Useful observations and timings of both types of event can be made by those set up for the video observation of minor planet occultations.

For more details refer to the IMCCE web site, <http://www.imcce.fr/phemu/> where predictions and requirements for observing and reporting information are available. Users of Dave Herald's Occult program can generate their own predictions.

SATURN is a morning object throughout January. It rises some 2 hours and 20 minutes before the Sun on the 1st and nearly 5 hours earlier on the 31st. The planet starts the month in Libra, moving into Scorpius on the 18th when it will be 10° to the left of Antares. At the end of January, Saturn will be 1° from the star beta Sco. The magnitude 2.6 star has a fainter companion, magnitude 4.5, some 13.8" from it. Binoculars will show the pair.

On the morning of January 17 the waning moon, 19% lit, will be a little less than 4° below Saturn.

Outer Planets

URANUS remains in Pisces as an evening object magnitude 5.8. By the end of January it will set soon after 11pm. The 30% lit moon will be 2° below Uranus on January 25. An occultation of the planet will be visible from a large part of northeast Asia

NEPTUNE is an early evening object in Aquarius at magnitude 8.0. On January 31 it will set at the same time as Venus, a few minutes before 10 pm. It will then be a little under 2° to the right of Venus. The conjunction of Mars and Neptune on the 20th (see Mars above) will give an opportunity to easily find the fainter outer planet using binoculars.

PLUTO is in Sagittarius at conjunction with the Sun of the 3rd. It will then be 32.8 astronomical units beyond the Sun and just over 5 billion km from the Earth. Light from Pluto takes about 4hours and 40 minutes to reach the Earth.

Brighter Asteroids:

(1) Ceres rises an hour before the Sun on January 1, some three and three quarter hours before it on the 31st. The asteroid is in Sagittarius, it will dim slightly during the month from magnitude 8.9 to 9.2 during January.

(3) Juno is at opposition on January 27 with a magnitude 8.1. This makes it the brightest asteroid currently observable. The asteroid is in Hydra.

(4) Vesta is at conjunction with the Sun on January 11. At conjunction it will be 35 arc-minutes from the Sun as seen from the Earth. Its distance from the Sun will be 2.20 AU, from the Earth 3.16 AU, 473 million km.

(6) Hebe, in the evening sky, dims from magnitude 9.0 to 9.6 as the Earth's distance from the asteroid increasing during January. The asteroid will be in Eridanus at first but moves into Taurus on the 11th.


The follwing table lists various solar system object events during January. A list of astronomical terms used in may be found after the table.

January 2 Aldebaran 1.4 degrees south of the Moon
January 3 Moon northern most declination (18.7 degrees)
Pluto at conjunction
January 4 Earth at perihelion
January 5 Moon full
January 8 Jupiter 4.8 degrees north of the Moon
Regulus 3.9 degrees north of the Moon
January 9 Moon at apogee
January 13 Moon last quarter
Spica 3.0 degrees south of the Moon
January 14 Mercury greatest elong E(19)
January 16 Saturn 1.8 degrees south of the Moon
January 18 Moon southern most declination (-18.6 degrees)
January 19 Pluto 2.8 degrees south of the Moon
January 20 Mars 0.2 degrees south of Neptune
Moon new
January 21 Mercury stationary
Mercury 2.9 degrees south of the Moon
Moon at perigee
January 22 Venus 5.4 degrees south of the Moon
Neptune 3.7 degrees south of the Moon
January 23 Mars 3.8 degrees south of the Moon
January 25 Uranus 0.6 degrees south of the Moon Occn
January 27 Moon first quarter
January 29 Aldebaran 1.2 degrees south of the Moon Occn
January 30 Mercury inferior conjunction
January 31 Moon northern most declination (18.5 degrees)
  • apogee: Furtherest point in the orbit of a body orbiting the Earth
  • conjunction: Two astronomical objects are 'lined up' (have the same right ascension) when viewed from Earth. If only one object is mentioned the Sun is generally the other object.
  • declination: 'Latitude' for celestial objects. The distance in degress above (north) or below (south) the celestial equator.
  • inferior conjunction: Conjunction where a solar system object is between the Earth and the Sun
  • perigee: Nearest point in the orbit of a body orbiting the Earth
  • perihelion: Nearest point in the orbit of a body orbiting the Sun