Expert: Tom Whiting - 4/1/2010

Question
QUESTION: Hi Tom,
if I have understood this correctly, the vernal equinox is regarded as the first day of spring when days are as long as nights, but who determined or discovered that? (I'm assuming then that the autumnal equinox is also the first day of autumn?)

If we know that the vernal equinox is the first day of spring, why don't the clocks go forward on that day as well?

Thanks for your time

Gary

ANSWER: Gary,
Technically, the sun is at the Vernal Equinox is when the sun crosses the celestial equator (which is right over top the Earth's equator) on it's northbound leg on the ecliptic. That point in the sky, the Vernal Equinox, is currently located in Pisces, at 0 hours of R.A. and 0 degrees Declination on your star chart of the sky. That is all determined by celestial motion (astronomy) and humans can do nothing about it.  All the humans did was decide to call this moment the "first day of Spring" for the Northern Hemisphere and first day of autumn
for the Southern Hemisphere.  The other equinox, in fairness to our S. Hemisphere friends, should be properly called the September Equinox... because it's their first day of spring, and
the N. Hemisphere's first day of Autumn. This is located in the sky at 12 Hours of R.A.
and 0 degrees Declination on your star chart in the constellation of Virgo, near the star
Eta Virginis.  This is the point in the sky where the sun on it's southbound leg on the ecliptic,
crosses the equator southbound... opposite in our sky from the Vernal Equinox.
Who discovered all that?  I don't know, as it's been known for thousands of years.  Probably
the Greeks, Egyptians, Arabs, or Babylonians several millenia ago. Certainly Julius Caesar was
aware of it and so was Pope Gregory with his Gregorian Calendar reform of the 1500's.

Time always moves forward, never backward.
Clocks, a fairly modern day invention since the 1700's, always move forward too, trying to keep track of the correct time, at least most of the time.  Or, if you're referring to our very
modern day Daylight Savings Time, in effect since World War I in, I believe 1917-1918, that is
all man-made and government made too.  Different countries change at different times... in the USA we already changed on March 14, but I believe the UK and Europe does it the following week.
Some parts of the USA don't do it at all... the "sane" states of Arizona and Hawaii do not
advance their clocks at all for the so-called summer months. The Daylight Saving Time clock change was never based on the March 20 sky event called the equinox, but rather just by human
convention in an attempt to give an extra hour of daylight to the evening sky rather than
the morning sky... at what humans determined to be an "appropriate" time for their society.
(For a short time, the USA was doing it in FEBRUARY, until that became very unpopular with the people)!

Realize that no extra daylight time is REALLY gained, you're just moving your clocks one hour ahead, thus "transferring" an hour of morning daylight to evening daylight, that's all. The sun still rises and sets at the same "time" of the day, it's just YOUR CLOCK reads differently.  The sun and night sky do not "add one hour" to "their" clocks. (They run on GMT time, or Universal
Coordinated Time -- whatever you want to call it, which never advances one hour).   It's only us 'insane' humans that "change our local clocks".

Theoretically it was supposed to "save energy" but new studies show that the gain or loss is
so minor... why bother in the first place?  But unfortunately, our societies have gotten "used to it"... so the insane event still occurs. This is very unfortunate for all us astronomers because in the deep summer months of late May, all of June, and part of July, it's not totally
dark until 11 pm clock time at 40 degrees N. Latitude (instead of 10 pm)... so we have to wait an extra clock hour for total darkness. On week nights, this makes it awful tough to get ANY observing in, as most people have to get up early for work, so astronomical observing on week-nights become very difficult during the summertime, when it's warm and comfortable... A real turn-off to the hobby, for new-comers.
Hope this helps,
Clear Skies,
Tom Whiting
Erie, PA USA
PS: R.A. stands for Right Ascension and the other coordinate is called Declination.
(They are the "longitude and latitude" coordinates of our celestial sky, repectively).




---------- FOLLOW-UP ----------

QUESTION: Hi Tom, I just wanted to write back and say thank you very much for taking the time to answer my question, which was very helpful and informative. I hope you don't mind but could you help me with one other thing please. At night, here in the UK, I can see a very bright object - larger than a 'typical' star. Could it be Venus? Is venus the only planet that can be seen with the naked eye from earth and how long roughly is it likely to 'stay' in the northern hemisphere?
Thanks again for your time. Regards Gary

ANSWER: Hi Gary,
If it's due west and low, yes, it's Venus just slowly climbing up into our evening western sky,
from around the back side of the sun.  But if it's a bright bluish star due south as darkness
falls, then it's the Dog Star, Sirius (or Alpha Canis Majoris)... the brightest real star (at -1.5 magnitude) in the sky.  But if it's a bright reddish "star" high in the south, almost overhead, then it's the planet Mars (at 1st magnitude) near the two prominent stars, the Gemini twins, Pollux and Castor. And if it's just rising in the east around 9 pm local time, it's the planet Saturn (at 0 magnitude) in Virgo.
Actually, 7 of the 8 planets of the Solar System can be seen naked-eye.  Watch for Mercury at first magnitude, to climb up beside Venus starting around March 31, first to Venus's lower right, then almost even with Venus (3 degrees apart) around April 3-6, then Mercury takes a dive back to the western horizon after that... it's not real bright like Venus, but easily visible to the naked-eye IF you know where to look.  Bright, easy naked-eye (-2nd magnitude) Jupiter is passing behind the sun now, but will start rising just ahead of the sun in the east, rising at first light by the end of April.
Let's see, that covers naked eye Mercury, Venus, Mars, Jupiter, and Saturn... all easy naked-eye
planets. That leave Uranus, which is just barely visible to the naked-eye at 5.8 magnitude in a very dark, moonless, non-light polluted sky IF you know exactly where to look for a very dim "star".  Neptune at 8th magnitude requires binoculars too see.
So 7 of the 8 planets can be seen by naked-eye under ideal conditions.

Venus, and all the planets, since they also follow the ecliptic (path of the sun in the sky),
can be seen by both hemispheres all the time, unless they are in the vicinity of the sun, and
except for far-polar regions where it's light for 6 months out of the year.
And with Venus, it's not large...it's bright.  We cannot see size with the planets and stars...
they are all pin-points to the naked eye.  We cannot judge distance either with a pinpoint of
light. We only see some color, and brightness. So we can say Venus is very bright (-4.5 magnitude) but we can't judge its size or its distance with our naked-eye.  Same for meteors too,
we only see brightness and color and have no way to determine their size or distance, but we
know from other studies that they burn from 100-60 miles high. And if we see them disappear over the horizon, that's exactly what most of them are doing; not crashing into the earth, but simply
going over your horizon out of view.
Oh, Venus will continue to slowly climb higher in the west for everyone until around mid-June, then begin a slow decent into the western sky until late September, passing between the Earth
and sun around mid-October (invisble to us).  Then the planet will "leap" up into the early morning eastern sky around mid-November and rapidly climb to it's maximum altitude in the eastern sky 3 hours ahead of the sun, rising at 4 am local time, by mid-December.
(A bright "Christmas star" in the East, 2 hours before first light, this year.) Since Venus takes
225 days to circle the sun, (to our 365 days), naturally it's in a different location and position every Christmas.
Hope this helps,
Clear Skies,
Tom Whiting
Erie, PA USA
Oh, remember that stellar magnitude (brightness) is a reverse scale... the lower the number,
the brighter the object, and by a factor of 2.5 times per whole number magnitude. And it's an exponential scale, not linear.  It does NOT go...2.5, 5, 7.5, 10, etc. but rather 2.5 to the first power, 2.5 squared, 2.5 cubed, 2.5 to the 4th power, and so on.  5 whole number magnitude changes equals about 100 times change in brightness, or 2.5 multiplied by itself five times!  Just thought you'd like to know.
Tom

Far more than planets can be seen with naked-eye under very dark, non-light polluted skies.
Nearly 1/3 of Charles Messier's list of the 110 Messier objects are also visible... true, most
are just faint fuzzy spots in the sky, but you can start with the open star cluster of the Pleiades (M-45)in the western sky in Taurus, Great Nebula in Orion (M-42), open star clusters M-35 in Gemini, and M-37 in Auriga, The beehive cluster (M-44 in Cancer), M-41 in Canis Major, the Andromeda Galaxy (M-31) is an easy naked-eye when it starts rising in NE in mid-summer around midnight; M-34 in Perseus, even NGC 752 open cluster in Andromeda is just barely naked-eye under a very dark sky. In the summer Milky Way you can easily see the Lagoon Nebula (M-8), the Wild Duck Cluster (M-11), M-6 in Scorpius, Globular Clusters M-13 in Hercules and M-5 in Serpens...
Double open cluster in Perseus, and I can go on and on...Also naked eye double stars Epsilon Lyrae, Alpha Capricorni, Theta 1 and 2 Tauri...if you have 20/20 vision or better.  
And IF you know exactly where they are at, in the sky.  Even just putting a pair of binoculars on those naked eye objects will reveal a stunning sight to the observer!
Hope this helps,
Clear Skies,
Tom



---------- FOLLOW-UP ----------

QUESTION: Hi Tom,
sorry to trouble you again but I was wondering if you may be able to give me some advice please with regards to my previous question where I asked about what planets could be seen with the naked eye. You kindly pointed out that many phenomena including planets could be seen with the naked eye or binoculars if 'you know where to look'. I am keen to know more and find out 'where to look' and whilst doing a websearch found out that there is an item called a planisphere which can be purchased to show the position of constellations with each year. Would this planisphere also show the position of the planets in relation to the stars? If not, is there a handy book or website you can recommend where I can find out 'where to look' for planets and other phenomena? I currently am not in a position to buy a telescope (just yet!) but do have a decent pair of binoculars and am very keen to learn more but, don't really know where I should be looking. I know it is pretty much a case of trial and error but I just wondered if there is a book or website or, if the planisphere may help get me started as to where to look. Thanks for your time. Best Regards Gary

Answer
Hi Gary from UK,
No trouble, we're just volunteers that like to help the people with their astronomy questions.
Yes, most beginners start with a simple planisphere to learn their night sky, and then later move
up to a better star atlas or star chart, like Cambridge 2000.0 or Norton's Star Atlas and Reference Handbook.  (There may be other equivalents available in the UK)... but typically they
cost about $20-40 USD, but they are good for the next 40 years, until another edition comes out in 2050... they are updated every 50 years. So if you cost-average it out, it's only about $1.00
USD per year!

The planets are not listed on any star chart or planisphere because, obviously, they move and are not fixed points of light. So what would be good for say March 2010 would not be good by
May 2010... so until you memorize their positions in the sky, you look up their positions on websites like http://www.skyandtelescope.com or an equivalent.
The positions of the planets are pretty easy right now, we've got Venus and Mercury very close
together in the west right after sunset, Mars is the bright zero magnitude reddish object very high in the south (60 degrees high from the UK) as darkness falls, Saturn is well up in the East
(in Virgo) as darkness falls, and bright Jupiter is just rising in the east at about 1/2 hour after dawn's first light.  
It's good that you have binoculars because right now a telescope is almost useless to you... if you can't point your finger to Albireo, the Andromeda Galaxy, the Lagoon Nebula, M-42 in Orion,
etc... all naked eye objects, how are you going to point a small field of view telescope? You can't!  Your first job is knowledge and learning the night sky, then once you know where those objects are at, then you can point a scope to them.  PLUS, what do you want to specialize in?
Lunar/Planetary? Deep sky objects? Comet Hunting? variable stars? (and you will specialize because there is just too much out there not to).  Then you get a scope that maximizes that activity that you prefer. Scopes are like airplanes, all airplanes fly, but you don't send a bomber to do a fighter's job.  Telescopes are exactly the same way. So you eventually get a scope that maximizes your favorite type of object.  That's why many of us amateur astronomers actually have several high quality telescopes.  Depends on what we want to look at during the night.
Hope this helps,
Clear Skies,
Tom Whiting
Erie, PA USA