Thursday, October 27
The Moon crosses the celestial equator heading south at 2:13 p.m.
The 14.3-magnitude asteroid 696 Leonora may pass in front of the 13.4-magnitude star 4U 433-117563 in Aquarius (δ=-3.4°; spectral type and distance unknown) for up to 11.3 seconds around 8:12:34 p.m. ± 10s. Probability of seeing the event along the predicted centerline is 42.7%.
Friday, October 28
Jupiter is near the Moon this morning before dawn. Both Jupiter and the Moon rise at 5:20 a.m.
The Iridium 66 satellite (Dysprosium?) will sunglint to -6.8 magnitude around 7:51:34 p.m. at azimuth 20° (NNE) and altitude 37° (748 miles), in Camelopardalis, between Polaris and Capella.
Saturday, October 29
Mars reaches perihelion at 8:12 a.m. (128.4 million miles from the Sun).
951 Gaspra became the first asteroid to be visited by a spacecraft when Galileo passed within 994 miles, 25 years ago (1991).
Lunar Orbiter 1, the first U.S. spacecraft to orbit the Moon, was intentionally crashed on the farside of the Moon at the end of a successful mission, 50 years ago (1966).
Carl Witt (1866-1946), German astronomer, was born 150 years ago.
Saturn is nearest Venus today during evening twilight. Binoculars may enhance the view.
Sunday, October 30
Sensibly, Europeans fall back to standard time a week before we do.
New Moon, 11:38 a.m.; rises 7:15 a.m.; transits 12:50 p.m.; sets 6:18 p.m.; δ = -11° in Libra; 3.6° from the Sun (center-to-center) at 1:00 p.m.
The 19.6-magnitude unnamed asteroid 80041 (1999 JK38) may pass in front of the 9.2-magnitude star HD 171220 in Scutum (δ=-4.8°; F3V; 445-474 ly) for up to 0.4 seconds around 7:11:13 p.m. ± 15s, during astronomical twilight. Probability of seeing the event along the predicted centerline is 0.9%.
Monday, October 31
The CORONAS-F rocket body will cross the sky from 6:30:44 to 6:35:50 p.m. (N to S). Peak magnitude: +1.0; Highest altitude: 85°. Closest distance: 193 miles. Nautical twilight. 6:32:39 p.m. crosses the handle of the Little Dipper; 6:33:16 very near Deneb; 6:34:25 Capricornus.
Tuesday, November 1
Ansel Adams (1902-1984) took his iconic photo, "Moonrise, Hernandez, New Mexico" 75 years ago (1941).
Nikolaus von Schönberg (1472-1537), a German Archbishop of Capua, wrote a letter to Nicolaus Copernicus (1473-1543) urging him to publish his heliocentric theory of the solar system, 480 years ago (1536).
Wednesday, November 2
The 16.1-magnitude asteroid 1477 Bonsdorffia may pass in front of the 11.5-magnitude star Tycho 2486-00926-1 in Cancer (δ=+32.8°; spectral type unknown; 330-353 ly) for up to 2.3 seconds around 3:38:21 a.m. ± 9s. Probability of seeing the event along the predicted centerline is 14.2%. For more information, visit http://asteroidoccultation.com/asteroid.htm.
Bengt Edlén (1906-1993), Swedish astrophysicist, was born, 110 years ago.
Saturn is near the Moon during evening twilight. Venus adds to the delight.
Thursday, November 3
Taurid meteors may be seen around this date.
"Astrophysics Flagships, Present & Future" by Ken Sembach, Director, Space Telescope Science Institute, 4421 Sterling Hall, UW-Madison, 3:30 - 5:00 p.m.
One of my favorite features of Sky & Telescope every month used to be the "Hobby Q & A" page. Sadly, this column ran for just five years, beginning in May 2004 and ending in May 2009. One of the many interesting questions addressed was in the August 2004 issue: Will Mercury and Venus ever transit the Sun simultaneously? Roger Sinnott answered the question using results from computational work by Jean Meeus and Aldo Vitagliano. Around July 26, 69163 (the exact date depends on small but accumulated changes in Earth's rotation rate and whatever additional changes to the calendar our descendants make), Mercury and Venus will be simultaneously transiting the Sun. What a sight that will be! Nearly 54,000 years before that, around April 5, 15232, a transit of Venus will be interrupted by a solar eclipse!
We live in a universe with (at least) three macroscopic spatial dimensions. But when we look at the night sky, it seems that we are looking at a two-dimensional surface. When two celestial objects lie along the same line of sight, the result can be...interesting.
One such cosmic chimera is the galaxy pair NGC 3314 in Hydra. A nearly face-on spiral galaxy is seen directly in front of a more oblique spiral galaxy. NGC 3314a (the foreground galaxy) is at a distance of 117 Mly, and NGC 3314b (the background galaxy) is at a distance of 140 Mly. NGC 3314's duplicity wasn't confirmed until Bill Keel and Ray White at the University of Alabama in Tuscaloosa imaged the object using the Hubble Space Telescope in 1999 and 2000.
Here is a description of NGC 3314, written just prior to Keel & White's discovery, in The Night Sky Observer's Guide: Volume 2, Spring and Summer by George Kepple and Glen Sanner (1998).
16/18" Scopes - 150x: NGC 3314, a dim object, is the southernmost member of the Hydra I Galaxy Cluster. It is located 7' ESE of a 6th magnitude star and 7.5' south of galaxy NGC 3312. NGC 3314 has a faint 1' x 0.5' NW-SE halo of even surface brightness. A 13th magnitude star touches the galaxy's NW tip.
Nine years earlier, in 1989, Chris Luginbuhl and Brian Skiff wrote a brief comment about NGC 3314 in their book Observing Handbook and Catalogue of Deep-Sky Objects. "3314AB - interacting pair?; in Hydra cluster; chart XI."
Today, it appears these two galaxies are not interacting, but simply a chance superposition of two galaxies 23 million light years apart.
Another example of celestial superposition is the overlapping star clusters NGC 1750 and NGC 1758 in Taurus. These two clusters are actually portions of NGC 1746, which is probably not a real cluster at all but just NGC 1750 + NGC 1758 + some foreground stars.
Three other examples of overlapping galaxy pairs are Messier 60 & NGC 4647 in Virgo, AM 1316-241 in Hydra, and 2MASX J00482185-2507365 in Sculptor.
Aside from Iridium flares, the International Space Station (ISS) is the brightest artificial satellite to traverse our skies. How high does it orbit? Right now, at an altitude of 252 miles above the surface of the Earth. Over the past year, the ISS has orbited as low as 249 miles to as high as 252 miles (it's current position) above the surface of the Earth. Atmospheric drag causes the ISS (and all satellites) to drop closer to the Earth, which in turn leads to more drag, thus eventually causing the satellite to burn up in the Earth's atmosphere unless it is periodically boosted into a higher orbit. Every so often, then, the station's onboard thrusters are fired for 90 minutes to 3 hours (1 to 2 orbits) to raise the ISS to a higher orbit.
This week, I got to wondering whether or not stellar occultations by near-Earth objects (NEOs) could be used to refine the orbits of these objects. NEOs are of great interest because of their potential to eventually collide with the Earth with catastrophic consequences. A quick search on the internet yielded a 2010 paper published in Cosmic Research by Koschny, Drolshagen, and Bobrinsky, "Relevance of Asteroid Occultation Measurements to Determination of Characteristics of Near-Earth Objects." They write:
"Observation of asteroid occultations (to be exact, of star occultations by asteroids) is currently the only easily accessible direct method of observations of asteroid dimensions. The position of an asteroid can be also determined with much higher accuracy as compared to the normal astrometric observations."
"Assuming the relative velocity equal to a typical value of 5 to 10 km/s, we obtain that the observation of the event related to an object with a dimension of 1 km would require a time resolution of 0.1 s. This value lies within the limits of characteristics of available video cameras...however, the occultation last usually only 2 frames and is difficult to be detected."
"Though observations of NEO objects by the occultation method definitely present a problem, they are not impracticable. Nevertheless, in the present situation, we do not consider it adequate to make special efforts for observation of NEO objects by the occultation method. In the several years to come we expect substantial improvement in the position accuracies of the star catalogs, which immediately will improve prediction of occultation paths, thus reducing the needed number of observational stations. Thus, any organization or group forming a program of monitoring of the near-Earth objects should follow the development of this method, but its regular use for determination of characteristics of these small objects would require large investments into the development of systems of cameras and education of personnel for working with these systems."
