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November 8th, 2006 Mercury Transit

CAUTION! OBSERVING A TRANSIT IS DANGEROUS AND MAY CAUSE IRREVERSIBLE EYE DAMAGE, UP TO BLINDNESS! Observing a transit necessitates the use of the DEDICATED SAFE TECHNIQUES recommended for the observation of a solar eclipse!

On November 8th, 2006, Mercury is transiting the Sun. The show is available in its entirety for the Paficic Ocean only and only some of its rims. Areas either side have the show interrupted by sunset or en cours at sunrise. No transit again before the years 2016 and 2019, then 2032 and 2039. Don't miss this one if you have the chance of living in the good region or travelling there! A transit is a fine vista as, at the same time, transits, generally, now serve to test techniques which are useful to detect exoplanets around their stars

A Transit Process

A transit is when an inferior planet -Mercury or Venus- is seen moving against the disk of the Sun. This is a question of alignment between the Sun, the planet, and the Earth. These are rare events, depending upon the celestial mechanics. Mercury transits are relatively common compared to the ones of Venus, which occurs by row of two each 105 or 121 years. Mercury is seen transiting the Sun about 13 times a century. All Mercury transits occur either in May (about May, 8th) or in November (about November, 10th) as it is at these times that the planet is crossing the Earth's orbit plane. Such moments are called the "nodes" of Mercury's orbit. If, at the same time, Mercury is at its inferior conjunction, that is in line Sun-Earth, between the Sun and the Earth, a transit is seen. In November, Mercury is at perihelion -its nearest Sun, hence an apparent diameter of 10", as, in May, Mercury is at aphelion -its nearest Sun, hence an apparent diameter of 12". The May transits are twice less numerous than those of November. They occur each 13 or 33 years. November transits occurs each 7, 13 or 33 years

Where the November 8th, 2006 Transit Will be Observable From?

This transit of 2006 is a Pacific Ocean one. The transit is visible in its entirety from the Pacific Ocean proper and from some of its rims: southern Alaska, westernmost Canada and USA, northwestern part of Central America, southeastern Australia, and New Zealand. Areas further East have the transit interrupted by sunset, like in the other parts of Canada, USA, Central America and in South America. Areas further West have the transit already unfolding by sunrise. This is the case for Russian Far East, Japan, Corea, China, and South East Asia. Europe, most of the Federation of Russia, Africa, Middle East, Central Asia, and India do not have any transit

Data For the Transit

transit duration:	04h58m
Mercury apparent diameter:	10" (1/194th of the Sun's apparent diameter)
contact I:	19:12:04 UT
contact II:	19:13:57 UT
greatest (or "minimum separation"; instant when Mercury passes closest to Sun's center)	422.9 arcseconds
greatest time:	21:41:04.2 UT
contact III:	00:08:16 UT
contact IV:	00:10:08 UT

note: contact times are geocentric, that is they are only correct for an observer stationed at Earth's center. The contact times for any given location may differ by up to a minute due to the effect of parallax depending on the observer's location

click to a chart for the November 8th, 2006 Mercury transit -with world visibility (139 ko). ticks from 15m into 15m with hours in UT. The "position angle" is the direction of Mercury with respect to the center of the Sun's disk as measured counterclockwise from the celestial north point on the Sun. map courtesy Fred Espenak - NASA/Goddard Space Flight Center, site NASA Eclipse Home Page

Observing a Transit

First things first! Like announced at the head of this page, observing a transit is dangerous and may gravely harm your eyes, up to blindness! Hence you will have, in any case, to be aware of such dangers and to use the appropriate techniques recommended for observing a Sun eclipse
Due to the small apparent diameter of Mercury, the best way to observe this transit is the use of a telescope with a magnification of 50 to 100x. In such a case, you will have to use appropriate solar filters at the aperture of the instrument. The projection method may seem just enough due to the small apparent diameter of Mercury during its transit. On the other hand, it has to be known that, for such a transit event, Web sites are broadcasting the event

Technically, a transit is made of five moments. Two ingress contacts (contact I and II), two egress contacts (III and IV) and the central moment (the greatest transit; the planet passes at the nearest of Sun's center; this moment is also called "minimum separation"). The two ingress and egress contacts are to be seen like:
- contact I is the moment when the planet's limb comes into contact with the Sun's limb. It's the "external tangency"
- contact II is the "internal tangency". The planet has progressed on the solar disk and its limb is now leaving the solar limb -at the interior of the latter. The planet begins its journey in front of the Sun
- contact III is another "internal tangency". The planet comes back to contact to the solar disk. The planet's limb arrives to contact to the Sun's limb. - contact IV, at last, is when the planet's limb is definitively leaving the Sun's limb. It's another external tangency
The internal tangent contacts (II et III) are precisely the moments when, after or before the so-called "black drop effect", the disk of the planet is completely encircled with light. Limbs, before that moment, are still in touch as the planetary disk is not seen dissociated from the Sun's limb. During 20 to 30 seconds, the planet's dark disk is linked, drop-shaped, to the solar limb. Contacts II and III are hence measured when the planetay disk is dissociated -contact II and when it stops being dissociated -contact III. During an observation, it's usually these contacts which are measured. Contact I and IV are not easily observable as the planet is still -or again- in the glare of the Sun. Using an H-alpha filter however allows to the view of these contacts as the planet is seen silhouetting on the prominences or the Sun's chromosphere. In between the contacts, the transiting planet is seen slowly crossing slowly the solar disk. The minimum separation is the center of the course: planet is at its nearest of the center of the solar disk (and farthest from the limb)

Next Mercury Transits

Transits of Mercury in the 21st century Date Greatest in UT Minimum separation 2016 May 09 14:57 319" 2019 Nov 11 15:20 76" 2032 Nov 13 08:54 572" 2039 Nov 07 08:46 822" 2049 May 07 14:24 512" 2052 Nov 09 02:30 319" 2062 May 10 21:37 521" 2065 Nov 11 20:07 181" 2078 Nov 14 13:42 674" 2085 Nov 07 13:36 718" 2095 May 08 21:08 310" 2098 Nov 10 07:18 215"

Next Transits of Venus Date Greatest in UT Minimum separation 2012 Jun 06 01:28 553" 2117 Dec 11 02:48 724" 2125 Dec 08 16:01 733"

. for the 2003 Mercury transit and the 2005 Venus transit, see at our Archive
. for more about the November 8th, 2006 transit, see Fred Espenak's NASA Eclipse Home Page, NASA/GSFC

Observation Reports: some sites were broadcasting the event live. Most of them had an important power at their observation instruments, leading to views where Mercury was of a respectable size. Such transit events may viewed in an enhanced view too, when an H-alpha filter or telescope is used, providing a view of the transiting planet even before it reaches the Sun's limb, on the background of preeminences and the chromosphere. The broadcast by NASA was hampered with codecs compatibilities, as more conventional reports are showing how Mercury is seen like a small dot against the solar disk during a transit