Today, July 4, 2014 the Earth reaches its farthest point away from the sun. This is called aphelion or in U.S. we call it Independence Day. Aphelion occurs when the Northern Hemisphere is experiencing summer. The point in orbit where a planet is nearest to the sun is called the perihelion. The word aphelion derives from the Greek words, apo meaning away or off and Helios (the Greek god of the sun). Earth’s aphelion usually occurs sometime around July 4. At aphelion our planet is around 152 million kilometers (94 million miles) away from the Sun. This is in contrast to perihelion when it is 147 million kilometers away from the Sun, and it currently occurs around January 3.
Tag Archives: Earth
Vernal, Spring or March Equinox
A little over two months ago I wrote about the Winter Solstice. Now that the Vernal, Spring or March Equinox is approaching there’s no better time to discuss the equinoxes, when they occur and why they are important.
There are two per year. They occur in March around the 20th day of that month and in September around the 22nd day. The March equinox or Vernal equinox will occur here in the DFW area on Thursday, March 20, 2014 at 11:57 a.m. CDT or Thursday, March 20, 2014 at 16:57 UTC.
The word origin for equinox come from the Latin words aequus (equal) and nox (night). So it stands to reason equinox literally means the time when the amount of day light hours and night time hours in one day are almost equal.
If you imagine the Earth’s equator projected out into space this is referred to as the Celestial equator. The two points where the Sun crosses this Celestial equator (see numbers 2 and 4 in the graphic above) are the equinoxes. Again, one happens in Spring and the other in Fall for both the Northern and Southern hemispheres of the planet. As we mark the Spring equinox in the Northern hemisphere the Southern hemisphere is observing it’s Fall equinox. But again, the key here is that the amount of day light hours and night time hours on this day are almost equal at about 12 hours each. This is true no matter what hemisphere you are in.
The Northern hemisphere marks the beginning of Spring which is seen as a time of rebirth and thus many or the world’s religions have celebrations at this time. Christian’s celebrate Passover and Easter around this time.
Spotting Earth Orbiting Satellites
Interest in watching for satellites has really increased over the past decade mainly due to the International Space Station being assembled in orbit, growing in size and brightness, etc. The amount of hardware orbiting over head has also increased. With all this stuff circling around above, your chances of seeing one of these spacecraft glide across the pre-dawn or evening sky only increases. Perhaps you’ve seen a “moving star” yourself and wondered what it might be? An airplane perhaps? But wait, there were no navigation lights blinking to give it away. Maybe it was a UFO? Chances are what you saw was a satellite silently sweeping across the sky, and possibly looking down at you.
Winter Solstice
So what is the Winter Solstice? Well, put simply, its that point in time when the Sun reaches it southern most point in the sky when measured from the north pole. Saturday, December 21, 2013 the Northern Hemisphere will experience the fewest hours of sunlight of the year. Specifically, the Winter Solstice takes place at 11:11 p.m. CST. Here in the Dallas-Fort Worth area we’ll have just 9 hours, 58 minutes and 28 seconds of daylight, and that will most likely be degraded due to the rainy weather meteorologists currently have forecast.
It’s important to note here that the length of the day (24 hours) is not changing but the hours of daylight during the days are fluctuating over the period from the Winter Solstice on to the Summer Solstice. The Summer Solstice, which will occur on June 21, 2014, in contrast, will enjoy almost 14 and a half hours of daylight.
"The word solstice is derived from the Latin sol (sun) and sistere (to stand still), because at the solstices, the Sun stands still in declination; that is, the seasonal movement of the Sun's path (as seen from Earth) comes to a stop before reversing direction."
So at the moment occupants of the Northern Hemisphere have the Winter Solstice the Southern Hemisphere has their Summer Solstice. The opposite is true with regard to the length of sunlight hours in the Southern Hemisphere at this time. Put another way, while we’re making snowmen and enjoying hot chocolate the good folks in the Southern Hemisphere are slippin’ another prawn on the barbie and pulling a tinny out of the cooler.
You can picture the north pole being tipped 23° away from the Sun while the south pole is aimed 23° toward the Sun. However, don’t make the mistake of assuming that since the hours of sunlight are less and the Sun is at it’s lowest point in the sky of any time during the year that the temperatures in the Northern Hemisphere will also be at their lowest. Typically the coldest days of the winter occur later in the season and not on the solstice.
So embrace the darkness or celebrate the promise of illumination. You decide. But above all relish the fact that you are a living being on a dynamic celestial body hurtling through the cosmos.
ISS Over DFW This Evening
The International Space Station will be making a very nice pass over the Dallas/Fort Worth area beginning at about 9:30 PM tonight. If you can see through the pop up thunderstorms and pull yourself away from either the Ranger’s game OR preseason Cowboy game the ISS will be bright at – 3.5 magnitude. Go out and look up.
Asteroid 1998 QE2 will pass close to Earth on Friday, May 31st
Another asteroid is set to buzz Earth. Is it just me or are these events happening more frequently? The asteroid designated 1998 QE2 will be making it’s close approach to Earth tomorrow (Friday) May 31, 2013.
1998 QE2 is considered a potentially hazardous object because it makes a regular close approach to Earth’s orbit, and it’s a whopper! QE2 is over 1.5 miles across. To help give you a visual reference that’s the equivalent of nine QE2 (Queen Elizabeth 2) cruise ships lined up end to end.
This Friday marks the QE2’s closest approach to Earth for at least a couple a hundred years and even at it’s closest it’ll still be about 15 times farther away than the Moon, but that’s close astronomically speaking.
1998 QE2 will be closest to Earth at 3:59 p.m. CDT. Once it gets dark you can try to located QE2 as it will be visible in small telescopes but you’ll need a dark sky.
NASA has already started imaging the asteroid with massive radar telescopes and they found that 1998 QE2 has a small moon. The preliminary estimate for the size of the asteroid’s satellite, or moon, is approximately 2,000 feet (600 meters) wide.
Asteroid 1998 QE2 was discovered on Aug. 19, 1998, by the Massachusetts Institute of Technology Lincoln Near Earth Asteroid Research (LINEAR) program near Socorro, N.M.