April 7
The Grain Returns
Sun Position
The Sun is in Aries near +10° declination. Daytime is now clearly longer than night across the northern hemisphere; southern mid-latitudes are approaching the tipping point toward longer nights.
Sky Highlight
The annual Virginid meteor shower complex is active through much of April, producing sporadic rates of 5 to 10 meteors per hour from the general direction of Virgo. It is not a sharp-peaked shower and produces no single standout night, but it makes April evenings more active than average and rewards patient watching.
Deep Sky Object
M104, the Sombrero Galaxy (NGC 4594), spiral galaxy in Virgo, about 28 million light-years. M104 is one of the most photographed galaxies in the sky: its bright central bulge bisected by a prominent dark dust lane gives it the hat-brim silhouette that inspired the name. Best from northern mid-latitudes; visible with effort from the southern hemisphere.
Featured Star
Spica (α Vir) appears again tonight, 250 light-years away, its paired B1 giant and B2 companion circling each other in just under four days. The system is one of the few stars close enough and bright enough that ground-based interferometry has actually resolved the separation between its two components, confirming the orbital geometry predicted from Doppler measurements.
Around This Date
- April 7, 1991The Compton Gamma Ray Observatory was deployed from Space Shuttle Atlantis on mission STS-37, beginning nine years of observations that mapped the gamma-ray sky and discovered a new class of gamma-ray bursts of extragalactic origin.
- April 9, 1959NASA publicly introduced the Mercury Seven astronauts at a press conference in Washington, presenting the first Americans selected for spaceflight.
Spica's two stars are close enough that gravity has pulled them out of round; what looks like a steady point of light is actually two distorted suns in a perpetual embrace.