Category: Astronomy

Exploring the cosmos

Mercury at Maximum Elongation

Today Mercury reaches maximum elongation, the furthest point it will reach from the Sun in the sky and the highest it will be above the sunrise for this morning apparition. The planet is easily visible as a bright, starlike object about 21° above the rising Sun as the twilight begins. Over the next couple weeks Mercury will slide back into the sunrise, heading for superior conjunction on August 8th.

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Mercury and Venus

As Mercury approaches maximum elongation on July 12th it is also approaching Venus in the sky. The little planet will reach elongation and turn to dive back into the dawn before properly rendezvousing with Venus. The minimum separation will be about 6° on the morning of July 16th.

While the pair will remain well separated, it will still be a pretty pairing in the dawn that will last for over a week. Simply look below the brilliant Venus for Mercury shining near 0 magnitude, it will be quite easy to spot in the glow of dawn.

Apehelion

Today the Earth is furthest from the Sun, a point called apehelion. We will be about 152,096,000km (94,508,000miles) from the Sun. Compare this to the 147,099,000km (91,403,000miles) we were be at perihelion on January 3rd, a difference of about 4,996,000km (3,104,000miles) occurring throughout one orbit.

It may seem odd that we are actually at the furthest for the middle of northern summer, you just have to remember that proximity to the Sun is not the cause of the seasons. The seasons are caused by the axial tilt of the Earth, creating short and long days throughout the year, with a resulting change in the angle and intensity of the sunlight.

2014 Solstices and Equinoxes
  UT HST
Perihelion Jan 4 05:59UT Jan 3 19:59HST
Vernal Equinox Mar 20 16:57UT Mar 20 06:57HST
Summer Solstice Jun 21 10:52UT Jun 21 00:52HST
Apehelion Jul 3 22:59UT Jul 3 12:59HST
Autumnal Equinox Sep 23 02:30UT Sep 22 16:30HST
Winter Solstice Dec 21 23:03UT Dec 21 13:03HST
 
Source: NASA Sky Calendar

 

Jupiter Exits the Evening Sky

Jove
Jupiter and the moons Europa, Ganymede and Callisto (left-right)
Jupiter is quickly sliding into the sunset heading for superior conjunction on July 24th. This evening the planet will be 15° above the setting Sun, in the next couple of weeks it will disappear into the glare. Look for Jupiter to reappear in the dawn during the first week of August.

The Moon and Jupiter

This evening a very thin crescent Moon will meet Jupiter low in the sunset glow. Only 3.4% illuminated the Moon will be 6° west of a bright Jupiter. About 16° above the horizon at sunset, the Moon will set at 20:14HST with Jupiter setting a few minutes later at 20:20HST. The two should create a striking pair in the rosy glow of dusk.