April 20
The Sun Enters the Bull
Sun Position
The Sun crosses into Taurus around April 20, reaching a declination near +20°. Northern hemisphere days are long and bright; southern hemisphere is approaching the halfway point to the winter solstice.
Sky Highlight
With the Sun in Taurus, Taurus itself becomes invisible, too close to the Sun in the daytime sky. This is a good reminder that the zodiacal constellations are opposite their namesake solar positions: when the Sun is 'in' Taurus, Scorpius is prominent in the night sky on the other side of the Earth. Scorpius rises in the southeast well before dawn in late April.
Deep Sky Object
M68 (NGC 4590), globular cluster in Hydra, about 33,000 light-years. M68 is one of the few Messier globular clusters below the celestial equator, and while it requires a southern or low-northern vantage point to see well, it is a classic of its class with a mildly elliptical core. Best from southern hemisphere and low northern latitudes.
Featured Star
Arcturus (α Boo) returns tonight, 36.7 light-years away, the brightest K-type giant in our sky. Its orange color is visible to the naked eye under dark skies, and its high proper motion (moving about 2.3 arcseconds per year) means it has shifted noticeably against the background stars in the few thousand years of recorded astronomy.
Around This Date
- April 20, 1972Apollo 16 landed in the lunar Descartes Highlands, and John Young and Charles Duke began the first of three moonwalks to collect highland geological samples.
- April 24, 1990The Hubble Space Telescope was launched aboard Space Shuttle Discovery, beginning its mission to observe the universe from above Earth's atmosphere.
The Sun's entry into Taurus marks the moment Taurus disappears from the night sky, the constellation of the month is always the one you cannot see.