Celebrating the night skies of 1865 and 2015.
Eltanin, the Birthday Star
South Bend, Indiana, was incorporated 150 years ago. Around that time*, photons of light left Eltanin (el-TAY-nin), the brightest star in the constellation Draco. The dragon encircles the north star, Polaris, while straddling the Big and Little Dippers. Eltanin, which is Arabic for serpent, is an eye of the dragon.
The photons of light that left Eltanin in the city's early years--traveling at 186,000 miles per second--are just now arriving in South Bend.
Dr. Jim Kaler of University of Illinois, describes some features of Eltanin:
Eltanin's high northerly position also takes it nearly through the zenith, the point overhead, as seen from London, causing it to acquire the now obscure name "zenith star." As a result the star was heavily studied. In 1728 James Bradley discovered an "aberration of starlight," which is caused by the velocity of the moving Earth relative to the speed of the light coming from the star. The discovery once and for all proved that Copernicus was right and that the Earth truly does move around the central Sun.
Eltanin is also moving toward us, and will make a close pass at a distance of 28 light years 1.5 million years from now, when it will be the brightest star in the sky and will rival our current Sirius. Physically, Eltanin is a cool (4000 Kelvin) orange giant with a luminosity 600 times that of the Sun.
The star is 50 times the solar diameter, a bit over half the size of Mercury's orbit.
Bruce McClure of EarthSky shares how Eltanin will be both a North Star and a South Star--over time:
Mathematical wizard Jean Meeus (page 363 of Mathematical Astronomy Morsels V) calls Eltanin the “Queen of the Poles” because this star will be the north pole star in the year 92020 and then the south pole star in the year 2083470!
*Distance to Eltanin is approximate. Over the years, star catalogs have listed varying distances. Eltanin is the star nearest the 150 light-year mark.
The City of South Bend celebrates its 150th anniversary in 2015. Michiana Astronomical Society Inc. (MAS) commemorates the event with First Midnight, a star chart for midnight of May 22, 1865, painted on the crosswalk at Washington and Michigan Streets in downtown South Bend.
The elongated chart has an altitude-azimuth projection. The blue lines denote hours of right ascension (the celestial equivalent to longitude) and degrees of declination (the celestial equivalent to latitude). The blue lines converging at the north celestial pole, the location of the north star Polaris, represent hours of right ascension.
From the celestial equator (thick straight line), to the left are the curving 30 degrees north and the circular 60 degrees north of declination. Right of the celestial equator is 30 degrees south declination.
The ecliptic, the line along which the sun, moon, and planets appear, is drawn in dark green. Jupiter and Saturn are drawn where they were on April 22, 1865. Though enlarged to show rings and surface features, the planets look like bright stars in the real night sky, only the planets do not twinkle like stars.
Constellation outlines are in yellow. Stars are in white.
In 2015, the stars appear as they did 150 years ago, while the planets are visible in different locations. Look for opportunities to observe with the Michiana Astronomical Society Inc., including the annual Michiana Star Party, May 15-17, at Dr. TK Lawless Park in Vandalia, MI.
Kids, can you find...?
More images, star charts, and details about the crosswalk are at two blog posts: First Midnight, and Walk Across Time.
A birthday gift! On May 22, 2015, around 9:30 p.m. (civil twilight), start looking for Jupiter, the Beehive Star Cluster, the crescent moon, and Venus in a row, low in the west. Saturn rises in the southeast later that night. Quick, find a telescope for magnified views!