Wandering through the realms of the cosmos, pondering its huge vastness

Posts tagged “march equinox

March Equinox 2012

It’s equinox time again, and this year’s March equinox took place today at precisely 5:14 a.m. GMT, or Universal Time (13:14 in Manila). The March equinox was also known as the “spring equinox” in the northern hemisphere and “autumnal (fall) equinox” in the southern hemisphere as this event  marks the change of seasons — the beginning of spring in the northern part of the globe and autumn in the south.

During equinox, night and day are nearly exactly the same length – 12 hours – all over the world. This is the reason it’s called an “equinox”, derived from Latin, meaning “equal night”.

However, even if this is widely accepted, it isn’t entirely true. In reality equinoxes don’t have exactly 12 hours of daylight. A good website for looking at sunrise and sunset times in Manila can be found here. The best one for checking the bearing (direction) of sunrise or sunset anywhere in the world is the US Naval Observatory.

A more appropriate way to define equinox is given by astronomers. According to its astronomical definition, an equinox is the moment when the sun arrives at one of two intersection points of the ecliptic, the sun’s path across the sky, and the celestial equator, earth’s equator projected onto the sky.

Image credit: Chris de Villiers (www.skywatch.co.za)

My plans today were to head on the top of a high place and catch the sun setting due west. Sadly, the weather was not very good and the visibility was terrible.

Had I been able to see the sun it would have set due west.

Everyone always says that the sun rises in the east and sets in the west, but if we were really aware of our surroundings and more attuned to the sky we would realize that this is not true. In fact this is only true for two days out of the entire year and those are during equinoxes.

By studying the sun’s position in the sky over the course of a year from the same location, one can notice that its rising and setting positions are changing by more at a particular time of year than at any other time.

The amount of change in the location of the rising and setting of the sun  throughout the year depends upon where your viewpoint is. However, irrespective of where you are on the globe, the Sun will always rise exactly east and set exactly west during equinoxes (on March 20/21 and September 20/21)

On the other hand, near the solstices the sunrise position slows its change to close to a ‘standstill’  (the name ‘solstice’ being derived from the Latin for ‘sun standing still’).

Path of the Sun in the sky at different times of the year. Image copyright: Addison-Wesley

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Seasons Without Borders: Equinox March 2012

swb_equinox_march2012

Wherever you are on 20 March, 2012, celebrate your season in the cycle of life with Astronomers Without Borders.  Enjoy your own unique Equinox this year—and why not tell others about the experience?  Being mindfully aware of your place on this moving Earth may bring out the storyteller and poet in you.  AWB invites you to share your event reports and poems at the AWB Members’ Blog and AWB Astropoetry Blog. Send your poems to: astropoetry@astronomerswithoutborders.org.

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Happy March Equinox!

Before I forgot… Happy Equinox, everyone! 🙂

The word “equinox” derives from the Latin words meaning “equal night” and refers to the time when the sun crosses the equator. At such times, day and night are of nearly equal length everywhere in the world.

While the March equinox marks the beginning of spring in the northern hemisphere, it is the start of autumn in many parts of the southern hemisphere.

 

an illustration of the March Equinox, not to scale

During the equinox, the length of night and day across the world is nearly, but not entirely, equal. This is because the day is slightly longer in places that are further away from the equator, and because the sun takes longer to rise and set in these locations. Furthermore, the sun takes longer to rise and set farther from the equator because it does not set straight down – it moves in a horizontal direction.

Moreover, there is an atmospheric refraction that causes the sun’s disk to appear higher in the sky than it would if earth had no atmosphere.

How high the Sun gets in your sky, and how long it is above the horizon during the day, depend not only on the season, but also on your latitude.

 

Related links:


Skywatching Highlights: March 2011

March is filled with several exciting conjunctions, lunar occultations, planetary displays and other celestial events which will take place alongside with some big astronomy-related projects geared toward promoting the appreciation of the night sky to many people globally.

March Event Time Notes
5 New Moon 04:45 AM
6 Moon at apogee (farthest distance to Earth) 04:00 PM
7 Final close pairing of Jupiter and the moon for 2011
10 Moon shines near the Pleiades star cluster
11 Moon near star Aldebaran
12 Moon in between Capella and Betelgeuse
12 Juno at Opposition 6:00 PM
13 Moon shines in front of Winter Hexagon
13-18 Close pairing of Mercury and Jupiter dusk These appear low in western horizon
13 First Quarter Moon 07:45 AM
15 Gamma Normids Active from Feb 25 – Mar 22. ZHR 6
16 Minimum separation Mercury Jupiter dusk Mercury 2° to the left of Jupiter
16 Mercury 2° North of the Moon 01:00 AM
17 Lunar occultation of omicron Leonis Start: 6:20 PM End: 07:10 PM
17 Moon and Regulus are less than 10 degrees apart
19 Sun-Earth Day
20 Full Moon 02:10 AM This will also be the largest full moon of the year because it will be near perigee, its closest point to the Earth.
21 Vernal Equinox 07:20 AM
22

6th worldwide GLOBE at Night 2011 campaign

March 22 -April 4 for the Northern Hemisphere

23 Moon near red star Antares before dawn
23 Mercury greatest elongation East(19°) 09:00 AM
26 Last Quarter Moon 08:10 PM
26 Earth Hour 2011 8:30 PM
31 Venus 6° South of the Moon 09:00 PM

Note: Dates and sky displays are based on Philippine settings. Philippine Standard Time (PST) = UT + 8

 

Astronomy Terms:

Occultation – An event that occurs when one object is hidden by another object that passes between it and the observer.

Opposition – When two celestial bodies are on opposite sides of the sky when viewed from a particular place (usually the Earth).

  • it is visible almost all night, rising around sunset, culminating around midnight and setting around sunrise;
  • at this point of its orbit it is roughly[1] closest to the Earth, making it appear bigger and brighter.
  • the half of the planet visible from Earth is then completely illuminated (“full planet”)
  • the opposition effect increases the reflected light from bodies with unobscured rough surfaces
Greatest  (Eastern) Elongation When an inferior planet is visible after sunset, it is near its greatest eastern elongation. A planet’s elongation is the angle between the Sun and the planet, as viewed from Earth
Vernal Equinox The Sun will shine directly on the equator and there will be nearly equal amounts of day and night throughout the world. This is also the first day of spring (vernal equinox) in the northern hemisphere and the first day of fall (autumnal equinox) in the southern hemisphere

 

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References:

  1. EarthSky.org
  2. PAGASA Astronomical Diary — March 2011
  3. Philippine Celestial Events for 2011 (by PAS)
  4. SeaSky.org
  5. Wikipedia Encyclopedia