Mercury and Regulus low in east

Event Date: August 31st
Time: 6:15 AM


Brief

   Yesterday I talked about Regulus being close to Mercury, while this morning, they are slightly closer.  Regulus is much dimmer than Mercury, with the planet brightening gradually.  Since Mercury emerged from the Sun early this month, it has brightened in apparent magnitude by about 100 times, now at -1.3.  As for Regulus, it is about 1.6º from Mercury this morning, as image two shows in a 2º field.  Preceding that, is a showing of both rising in the east.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

Since Mercury has started moving slightly further from the Sun each day for the last week post-perihelion, that means that it has also moved away from us slightly faster, and not brightening as fast as it was during the first 3+ weeks of the month.  Today and tomorrow, we will see it at nearly the same separation from Regulus, being very binocular friendly.  After Mercury separates from the star, Regulus becomes easier to see, rising four minutes earlier each day.  As it does, the Sun quickly starts to move towards the celestial equator over the next few weeks, meaning that we have more dark sky time to see Regulus each week.  The Sun rises about a minute and a half later on average each morning during September.  Mercury however, stabilizes in magnitude as it reaches superior conjunction, and will not be easily visible again for about two weeks following that.  Once it finally is, it will be victimized by the poor evening geometry of the western sky at this time of year.  By the time the geometry starts to improve slightly in mid-late October, Mercury will already be too dim and low to see easily.  Therefore, enjoy it bright now, while still just high enough in the east.  It rises a little less than 50 minutes before the Sun, with Regulus to follow about 7 minutes later.