Category: Sky Events

Sky events

Perseid Meteor Shower

The Perseids are one of the most watched meteor showers. Occurring during northern hemisphere summer, the shower can be appreciated on a summer night. Quite a difference from the other reliable showers such as the Leonids and Quadrantids, that occur in November and January. Consider a warm summer evening under a dark sky full of stars, a picnic blanket, relaxing while shooting stars streak across the sky. What could be better?

The Perseid meteor shower occurs when the Earth passes through a stream of debris along the orbit of Comet Swift-Tuttle. This shower has been consistent throughout recorded history, mentioned in Chinese, Japanese and Korean records as early as the 1st century. Active from July 17th to August 24th, the shower will build slowly for weeks before the peak. A week before or after peak the shower can still be seen with around 20 meteors each hour. The shower is a northern hemisphere event, for southern observers the radiant never rises above the horizon.

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The Moon, Mars, Saturn and Spica

A nice conjunction of a crescent Moon, Mars, Saturn and the bright star Spica will grace the evening sky tonight. All four will be within 12° of each other. The two planets and the star will all be about 1st magnitude, with the Moon showing about 37% illuminated.

The same quartet will get together again next month, for an even tighter grouping.

A Very Thin Moon and Mercury

This one will be a challenge. This evening a very thin Moon may be visible just below Mercury as the Sun sets. The Moon will be a mere 1.3% illuminated and only 7° above the horizon at sunset. Mercury may provide a bit of a signpost that can be used to find the Moon. It will be located 2.5° directly above the Moon, shining at 2.8 magnitude. As Mercury is heading for inferior conjunction, it too is a thin crescent. The pair will be 10° south from the point at which the Sun slips below the horizon.

The Moon, Venus and Jupiter

The three brightest natural objects of our sky, after the Sun, will join to form a nice group tomorrow morning. The dawn of 14 July will see a thin crescent Moon and Venus only 11° apart. The bright Jupiter will be in between, only 6° from Venus. Jupiter will be shining brightly at better that -2 magnitude, Venus will be even brighter at over -4 magnitude. The pair will be a nice match for an 18% illuminated Moon.

The next morning, July 15th, will still see the trio quite close. The Moon will have moved east to a position just 4° north of Venus.

Venus and Aldebaran

Tomorrow morning, July 8th, Venus will pass less than 1° from Aldebaran. The Eye of the Bull may be one of the brightest stars in the sky at 0.9 magnitude, but it is no match for Venus at -4.4 magnitude.

On the morning of the 8th the planet will be 59′ from the star, just an iota under 1°. On the morning of the 9th the distance will be slightly closer at 55′. The pair will rise about 03:18, to be well up in the sky before sunrise.

Apehelion

Today the Earth is furthest from the Sun, a point called apehelion. We will be about 152,098,232km (94,509,459miles) from the Sun. Compare this to the 147,098,290km (91,402,639miles) we were at perihelion on Jan 4th, a difference of about 5,411,169km (3,362,344miles) occurs 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.

2012 Solstices and Equinoxes
  UT HST
Perihelion Jan 5 03:59UT Jan 4 17:59HST
Spring Equinox Mar 20 05:14UT Mar 19 19:14HST
Summer Solstice Jun 20 23:09UT Jun 20 13:09HST
Apehelion Jul 4 23:59UT Jul 4 13:59HST
Fall Equinox Sep 22 14:49UT Sep 22 04:49HST
Winter Solstice Dec 21 11:12UT Dec 21 01:12HST
 
Source: USNO Data Services Website and the NASA Sky Calendar