What’s up in the sky – June

By Fred Barrett

There’s a special treat this month for those of you willing to put in a little extra effort. About an hour before the first glimmer of dawn in the East, you will be able to see Comet McNaught (Comet C/2009 R1).

Robert McNaught of Australia’s Siding Spring Observatory discovered it as part of a NASA sponsored survey looking for potentially dangerous near Earth objects (NEOs). It will get brighter as the month progresses but the best time for seeing it is mid June. The new moon is on the 12th so the sky will be free of moonlight. Also, the balance between its brightness and its placement low above the horizon as dawn arrives makes it easier to find and view. Since this is a first-time comet making its first trip in from the Oort Cloud, it’s difficult to say how bright it might get but it will certainly be viewable in a small telescope and maybe even binoculars (or as a friend’s daughter calls them; ‘biboculars’).

The Oort cloud is a halo of lumps of ice and rock around the Sun (see figure). It extends from beyond Pluto’s orbit at 39 AU to as far as 300,000 AU from the Sun. An AU or Astronomical Unit is the distance from the Earth to the Sun. That distance is 93 million miles. So, 39 AU is 39 times 93,000,000 miles and 300,000 AU is 300,000 times 93,000,000 miles = 27,900,000,000,000 miles. Enough zeros for you? The gravitational balance out there is so sensitive that passing stars or giant molecular clouds can cause these objects to leave the Solar system, never to return, or start a long journey towards the inner planets as a comet. There is estimated to be about 6 Trillion Oort cloud objects. Have a look at the accompanying finder chart to see where the comet is during the month. Remember, the constellations in the chart are above the horizon in the East about an hour or so before dawn.

Venus can be viewed at its highest just after sunset this month. On the 19th and 20th it is within 2 degrees of the Beehive Cluster near the centre of the constellation Cancer. The Beehive is a beautiful sight in binoculars and a telescope with a low magnification eyepiece. The cluster is too large to fit in the field of view if there is more than a little magnification.

Mars is getting smaller and you can find it close to the star Regulus in the constellation Leo. Saturn is also dimming because its rings are tilted almost edgewise and not contributing to its brightness. Saturn is getting smaller too as Earth moves away from it. Jupiter rises after midnight and by mid June will be high enough to provide a steady detailed surface view in a telescope. The binocular view of Jupiter and its moons is very pleasing too! Uranus is within 2 degrees of Jupiter this month and its green blue tint is very refreshing in a good telescope. Take the time to search it out!

The days are still getting longer but that will end at 7:29 AM EDT (Eastern Daylight Time) on June 21, Summer Solstice. It marks the beginning of summer in the Northern Hemisphere and Winter in the Southern Hemisphere. A solstice happens twice a year. The Earth’s axis tilts towards or away from the Sun and the Sun’s position in the sky reaches its most Northern or Southern extreme. The word solstice is from the Latin for standing still and the Sun’s movement comes to a stop and it begins moving in the opposite direction. Did you know that the Earth is actually farther from the Sun in summer than it is in winter? It’s the axial tilt and longer days that provide the energy for summer’s heat, not its nearness to the Sun.

Full Moon is on the 26th. The Algonquin named it the “Strawberry Moon”. It signals strawberry harvest time! Similarly, Europeans named it the “Rose Moon” for the colour of strawberries.

If you have questions or suggestions, Fred Barrett may be contacted at cygnushill@hotmail.com

The Beginner’s Observer’s Guide by Leo Enright is available at the Sharbot Lake Pharmacy or by contacting the Royal Astronomical Society of Canada www.rasc.ca/publications, subscriptions for our very own excellent Canadian astronomy magazine, Sky News, are also available from RASC..