March 17
The Triple Corner
Sun Position
The Sun is in Pisces, declination near +15.5°; the vernal equinox is approaching within days for the Northern Hemisphere, and the autumnal equinox is correspondingly close for the Southern Hemisphere.
Sky Highlight
Virgo is climbing higher in the eastern evening sky through mid-March. Zaniah marks one of the constellation's less-observed corners but sits within the broader Virgo-Leo galaxy field that makes this constellation so rewarding in spring for telescope users targeting the Virgo Cluster.
Deep Sky Object
M49 (NGC 4472), the brightest galaxy in the Virgo Cluster and one of the most luminous elliptical galaxies known, about 55 million light-years away; it was the first Virgo Cluster member discovered by Messier and contains an estimated 200 billion stars. Visible from both hemispheres in spring, better from the north.
Featured Star
Zaniah (η Vir) is a white main-sequence triple system 265 light-years away, two nearly identical A2V stars orbit each other every 72 hours, while a third A8V companion orbits further out. Spectral class A2V + A2V + A8V: a system where three white stars are locked in a hierarchy that is slowly evolving as the inner pair gradually spirals.
Around This Date
- March 17, 1958Vanguard 1 launched, becoming the first solar-powered satellite and, as of today, the oldest artificial object still in Earth orbit.
- March 17, 2014The BICEP2 team announced detection of primordial gravitational waves in the cosmic microwave background polarization, a finding later found to be contaminated by galactic dust, illustrating the difficulty of this class of measurement.
Three white stars in a hierarchy: the inner pair orbits in three days while the third watches from a distance, as if thinking it over.