TSTW 4/3/08
Thursday, April 3
ATV 1, the Jules Verne, is scheduled to dock with the International Space Station at 9:41 a.m.
Douglas Douglas-Hamilton ("Lord Clydesdale"), Stewart Blacker, David McIntyre, and S.R. Bonnett in two British aeroplanes made the first flights over Mt. Everest, 75 years ago (1933).
Friday, April 4
The Moon crosses the celestial equator heading north.
Apollo 6, the last unmanned Apollo test flight, was launched, orbited three times around the Earth, and achieved splashdown in the Pacific with little press coverage, 40 years ago (1968).
Joseph Ashbrook (1918-1980), American astronomer, was born 90 years ago.
Saturday, April 5
New Moon; rises 6:03 a.m.; transits 12:36 p.m.; sets 7:23 p.m.; declination = +9°; 3.3° from the Sun (center-to-center) at 12:04 a.m. Sunday
The International Space Station will move from NW to N from about 9:30 to 9:32 p.m. It reaches its highest point in the sky (23° altitude) around 9:32 p.m., in Cepheus where it disappears into the shadow of the Earth.
Sunday, April 6
Albert Arnulf in Paris observed the first lunar occultation (Regulus) with fine-enough time resolution to see the diffraction pattern, 75 years ago (1933).
Monday, April 7
The Iridium 10 satellite will flare to -6 magnitude around 8:21 p.m. at azimuth 125° (SE) and altitude 65°, in Leo, during nautical twilight.
The International Space Station will move from NW to ENE from about 8:39 to 8:43 p.m. It reaches its highest point in the sky (24° altitude) around 8:41 p.m., in Draco during astronomical twilight.
The Moon is closest to the Earth this month this evening.
Algol ( Persei) is at minimum brightness, 10:10 p.m.
April Virginid meteors may be seen around this date.
Tuesday, April 8
Soyuz TMA-12 is scheduled to launch at 6:16 a.m. to deliver the Expedition 17 crew to the International Space Station.
The beautiful crescent Moon passes in front of the Pleiades this evening!
8:55 p.m. - Taygeta (19 Tau; 4.3) disappears9:06 p.m. - 18 Tauri (5.7) disappears
9:09 p.m. - Celaeno (16 Tau; 5.5) just misses
9:10 p.m. - Asterope (21 Tau; 5.8) disappears
9:13 p.m. - 22 Tauri (6.4) disappears
9:22 p.m. - Maia (20 Tau; 3.9) disappears
The International Space Station with Soyuz TMA-12 en route will move from NW to ENE from about 9:00 to 9:04 p.m. It reaches its highest point in the sky (48° altitude) around 9:03 p.m., between the Bowls of the Dippers during astronomical twilight.
Wednesday, April 9
The International Space Station with Soyuz TMA-12 en route will move from NW to ENE from about 7:47 to 7:52 p.m. It reaches its highest point in the sky (23° altitude) around 7:49 p.m., during civil twilight.
The International Space Station with Soyuz TMA-12 nearby will move from WNW to WSW from about 9:22 to 9:24 p.m. It reaches its highest point in the sky (54° altitude) around 9:24 p.m., near Mars, where it disappears into the shadow of the Earth. P = 95 minutes
Thursday, April 10
Jupiter is 90° west of the Sun (western quadrature) and therefore at its most gibbous phase (99.1% of full) as morning twilight begins.
Soyuz TMA-12 is scheduled to dock with the International Space Station around 9:00 a.m.
Here in southern Wisconsin, we can theoretically see 86.6% of the celestial sphere. I say "theoretically" because atmospheric extinction, light pollution, local topography, obstructions, and the fact that far southern objects (down to = -47° at = 43° N) spend very little time above our horizon each day, limits the amount of the celestial sphere that we can see well. So, practically speaking, we see only about 75% to 80% of all that there is to see from spaceship Earth.
What are the most prominent objects we are missing, and what objects that we can see are they closest to?
Alpha Centauri
Never visible north of latitude 27° N, the nearest star system beyond our solar system is Alpha Centauri. Alpha Centauri A & B are bright stars, having a visual magnitude of -0.1 and +1.3, respectively, and in 2008 they are separated by just 8 arcseconds, about 1/4 of the angular separation between Albireo A & B. While Alpha Centauri A & B--which orbit each other once every 79.24 years--lie just 4.36 ly away, a faint red dwarf companion, Proxima Centauri (shining at magnitude +11.1) is even closer at 4.22 light years. It is not yet known whether Proxima Centauri, discovered in 1915, is gravitationally bound to Alpha Centauri A & B, or just presently passing through the neighborhood. Proxima is a full 2.2° away (over four moon-widths) from Alpha Centauri A & B.
When Arcturus and Zubenelgenubi ( Lib) are crossing our meridian, so are Alpha & Proxima Centauri below the southern horizon.
Omega Centauri
Another showpiece southern object in the constellation Centaurus is not a star but a globular cluster named Omega Centauri, the brightest and largest of all globulars as seen from Earth. Even though it is 27% closer than M13 in Hercules, when I had a chance to observe both globulars from southern New Mexico a few years ago, I got the distinct impression that Omega was "fine grained" and richer, while M13 was "coarse grained" with fewer but brighter stars. There is some evidence that Omega Centauri is actually the core remnant of a dwarf galaxy that has merged with our Milky Way galaxy rather than a true globular.
Omega Centauri is directly below Spica when it is crossing our meridian.
Canopus
Canopus, in the southern constellation Carina, is the 2nd brightest star in the night sky, but never visible from Wisconsin. It shines at an impressive apparent visual magnitude of -0.7, exceeded only by Sirius at -1.5.
Canopus has been used to help orient many a spacecraft, owing to its position near the south ecliptic pole. When the leading edge of Canis Major, Murzim ( CMa), is crossing the meridian and Sirius preparing to do so, Canopus lies hidden beneath the south point on our horizon.
Large Magellanic Cloud
The Large Magellanic Cloud (LMC), the largest satellite galaxy of our Milky Way galaxy and easily visible to the unaided eye, lies directly below our southern horizon when Rigel has crossed the meridian and Bellatrix is preparing to do so.
Small Magellanic Cloud
The Small Magellanic Cloud (SMC), the second-largest satellite galaxy of the mighty Milky Way lies underneath our southern horizon when M31, the Great Andromeda Galaxy, is at the zenith.
47 Tucanae
The 2nd brightest globular cluster in the sky (after Omega Centauri) is impressive 47 Tucanae. It is just 2.3° west and a little north of the Small Magellanic Cloud, so crosses the meridian below our horizon just as M31 is nearing our zenith.
Eta Carinae Nebula
Four times larger and brighter than the Orion Nebula, the Eta Carinae Nebula is a spectacular star-forming region containing a supermassive (100 - 150 solar masses) binary star that may go supernova at any time. When Leo the Lion is straddling the meridian, the Eta Carinae Nebula sneaks across as well.
