"Let your soul stand cool and composed before a million universes" Walt Whitman
The Moon's current phase, courtesy of USNO.
Sierra NightSky for the period starting March 7, 2014 by Jim Kaler
Remember that Daylight Savings Time starts on Sunday, March 9. All times below are Daylight.
The night of Friday, March 7, sees the Moon as a fat waxing crescent as it approaches first quarter, which will be passed the morning of Saturday the 8th well after Moonset.
The remainder of the week is spent with the Moon in its waxing gibbous phase as it heads towards full on Sunday the 16th.
The evening of Friday the 7th, the Moon will make a fine sight to the left of the Hyades cluster just up and to the left of Aldebaran (which does not belong to the cluster). The following night, the waxing crescent will appear over Orion, then on the evening of Sunday the 9th look for it down and to the right of Jupiter.
By the night of Monday the 10th, the Moon will have flipped to the other side, appearing down and to the left of the giant planet. The afternoon of Tuesday the 11th, the Moon passes apogee, where it is farthest from the Earth, just over five percent more distant than average.
The planets are nicely arrayed all over the sky. As evening twilight draws to a close, Jupiter crosses the meridian high to the south and begins its slow slide into the northwest still within the confines of Gemini to the southwest of Castor and Pollux. It finally sets around 4 AM.
An hour later, brilliant Venus rises to dominate the sky until the Sun comes up and Venus appears as a tiny naked eye blip in the clear blue celestial sea.
In between, Mars rises around 10 PM to the northeast of Virgo's Spica, then transits the meridian about 3:30 AM as it enters the western celestial hemisphere just before Jupiter sets. As Mars approaches its early-April opposition to the Sun, it's brightened to magnitude minus one, behind only Venus, Jupiter, and the sky's brightest star, Sirius in Canis Major.
Mars is followed by the midnight rising of Saturn, which lies in the heart of Libra to the northwest of Antares in Scorpius. Don't confuse reddish Antares with Mars, which lies to the west of Saturn. The ringed planet then transits the meridian about as Venus rises.
Finally, we are left with little Mercury, which passes its greatest western elongation of 28 degrees to the west of the Sun on Friday the 14th. Rising only in twilight, however, it's still a difficult catch.
Not so of the bright stars. As evening draws to a close, the Winter Six still ride high.
The most prominent of them, Orion (with bright Betelgeuse and Rigel), is accompanied by Taurus (and Aldebaran) to the northwest, Auriga (with Capella) to the north, Gemini (with Castor and Pollux) to the northeast, Canis Minor (with Procyon) to the east, and finally the Big Dog, Canis Major (with Sirius) to the southeast. Below Orion look for box-like Lepus, the Hare, and to the northwest the star streams of Perseus, the most easterly of the constellations of the Andromeda myth.
STAR OF THE WEEK: TAU TAU (Tau Tauri)
How can you resist a star with a name like Tau Tau? It's certainly unique. (Don't confuse it with T Tauri, a faint protostar that is still developing, or with TT Tau, a variable carbon star.) Just to the east of the Hyades (but not a part of the cluster) in Taurus, at a distance of 398 light years (give or take 43), Tau Tauri is a multiple mess, certainly triple, possibly quadruple.
The dominating star is a fourth magnitude (4.3) class B (B3) dwarf with a temperature of 18,700 Kelvin. It's joined by an obvious seventh magnitude (7.0) A1 dwarf companion, Tau Tauri B. In the 19th century, Smythe and Chambers called the pretty pair "bluish white and lilac." For more than two centuries Tau B has held its separation from Tau A at 63 seconds of arc, the two obviously trekking through space together, joined by a fragile gravitational bond.
But now things get tricky. At a separation of about 0.1 seconds of arc is another seventh magnitude companion (Tau Ab, rendering the bright star Aa), and possibly at much less separation (0.0005 seconds) another (call it Ac), both detected by lunar occultation.
The inner of the close pair may be related to spectroscopic observation of a companion with a 2.96 day period, but neither has been confirmed.
The outer, however, Tau Ab, has been well enough followed for an orbit to have been constructed. At an average separation of 35 Astronomical Units, Tau Ab takes 57.9 years to go around Tau Aa, an eccentricity of 0.36 taking them between 22 and 47 AU apart. They were last closest together in February of 1980. Kepler's laws give a combined mass (which may include Ac) of 12.4 times that of the Sun.
The stars are dimmed 0.3 magnitudes by interstellar dust. Assuming the inner companion (Tau Ac) is insignificant, the primary star, Tau Aa, shines with the light (including invisible ultraviolet) of 1420 Suns, which gives it a radius of 3.6 times solar.
That and a typically fast rotation speed of more than 187 kilometers per second show the star to be rotating in under a day. With luminosity and temperature, theory gives a mass of 6.1 Suns. From its absolute magnitude, Ab is an A2 dwarf.
A supposed temperature of 9100 Kelvin leads to a luminosity of 29 Suns, a radius of 2.1 solar, and a mass of 2.2 Suns, which adds to a total of 8.3 times that of the Sun, notably less than that derived from the orbit.
A small adjustment of the mean orbital radius to 30 AU could take care of that, but so could some mass from the spectroscopic companion, Ac. With its short period, Ac would orbit at only a few hundredths of an Astronomical Unit from Aa, terribly and almost unrealistically close to its surface.
But wait, there's more! Distant Tau B, the A1 dwarf companion, is closely similar to Tau Ab, with a luminosity of 29 Suns, a mass of 2.2 Suns, and a radius of 1.9 times solar. With an equatorial rotation speed of at least 100 kilometers per second, it too takes under a day to spin. With a physical separation of at least 7800 AU, it must take over 200,000 years to orbit the inner triple.
We could continue by assuming the unconfirmed magnitude of Tau Ac, which reduces Tau A to a luminosity of 850 Suns and a mass of 5.9, but increases the system mass (as noted) to give better agreement with the orbital sum.
However, one could go on forever with adjustments and speculations; the basic structure of fascinating Tau Tau is clear, and perhaps it's best to quit and wait for additional observations.
Do you have a favorite star or one you would like to see highlighted on the Star of the Week? Send a suggestion to Jim Kaler.
Sierra NightSky thanks to Jim Kaler.
Check out his site for more