Mercury, our sun’s innermost planet, reaches what astronomers call its greatest western elongation from the sun on Thursday, August 16. That just means that, on Thursday, Mercury will be farthest from the sun on the sky’s dome for this predawn apparition. Because Mercury is farthest west of the sun at present, this world now rises into the eastern sky before sunrise. How long before sunrise it rises depends on where you live on the globe, but, for all of us, there are two very bright planets up before dawn now – just waiting to point you to elusive Mercury.
To catch Mercury, get up at least an hour before sunrise. Look eastward for the two brightest star-like objects in the sky. That’s the planets Venus and Jupiter. Draw an imaginary line, going downward from the right side of Jupiter and past the left side of Venus to locate Mercury near the horizon. Mercury shines as brilliantly as our sky’s brightest stars. But its luster may be tarnished by the murky glow of morning dawn. If you can’t spot Mercury with the eyes alone, try your luck with binoculars.
The farther north you live, the longer Mercury rises before the sun. The farther south you live, the closer that Mercury rises to sunrise. For instance, at mid-northern latitudes Mercury comes up about 90 minutes before sunrise. Meanwhile, at temperate latitudes in the Southern Hemisphere – as in southern Australia – Mercury rises about one hour before the sun.
Bottom line: Before sunrise on Thursday, August 16, use the super-brilliant planets Jupiter and Venus to find fainter Mercury, our sun’s innermost planet. Mercury reaches its greatest morning elongation on August 16. That means it’s now farthest from the sun for this predawn apparition and will soon begin descending in the predawn sky again, becoming lost in the sunrise glare. So look, next chance you get.