Jun 05, 2019
This month, we will talk about nothing again, but we will take a circuitous route to reach our empty destination. Be patient! First, we have to talk about one technique that astronomers use to measure the distance to a distant point in space. I have talked of this before, but it is worth a review. The Universe was once thought to be comprised of a relatively small amount of stuff and a great deal of empty space, and all of it in equilibrium. But it’s not that simple. Astronomers discovered that the universe is expanding and that that expansion is accelerating. There are basically 5 ways to estimate how far stars are, but each method has their advantages and disadvantages. With limited space, I’m going to concentrate on one method that also measures the acceleration of the expansion of our Universe. To measure the distance and the expansion rate of the Universe, astronomers use type IIA supernovas. The physics behind a stellar explosion like this and the brightness and energy it generates is completely predictable. Most star systems aren’t like our own Sun. There are usually 2 or more stars, orbiting each other in what is called a binary or multiple stellar system. Over many, many years, the stars orbit closer and closer until they eventually collide. Using physics and mathematics, the ‘luminosity’ or amount of energy that the resulting supernova emits can be theoretically calculated very accurately. Allowing for transparency in the atmosphere and dust clouds that are between our telescopes and the supernova, its luminosity or energy emission can also be physically measured. Their brightness can be compared against a standard and an estimate of distance calculated. A few years ago, it was discovered that their luminosity was less than it should have been when compared with the theoretical theory calculation of what the distance should be! To state it another way, it meant that the type IIa supernovae were farther than was expected because they were dimmer! To explain this difference, newer theories have suggested that empty space is actually generating more empty space and causing the volume of our universe to expand! Who would have guessed? The Universe will eventually, in a number of years that is too large for us to really appreciate (several Gazillion years), expand so far that the stars and the galaxies in the sky will be too distant to see! The sky will be completely BLACK and empty – nothing!
This month, in the evening hours, you will find Mercury and Mars in the northwest. Glorious Jupiter is in the southwest. By the time midnight arrives, Jupiter is high in the south and Saturn in the southeast. By morning, you can’t miss bright Venus in the northeast. Jupiter is still up in the southwest with Saturn keeping her company. You absolutely must follow the dance of Jupiter’s 4 most prominent moons as the month progresses. They are easily observable in binoculars. On June 10, Jupiter is in opposition and at its closest and brightest.
June 7th: The Moon is at perigee – 366,365 Km.
June 10th: First quarter Moon. Jupiter is in opposition.
June 16th: At 3pm, the Moon is 2 degrees north of Jupiter. Even though it is daylight, Jupiter is so bright that you may be able to make it out.
June 17th: Full Moon. This is the month of the Full Strawberry Moon. All hail everything strawberry, especially strawberry shortcake!
June18th: Mercury passes a fraction of a degree north of Mars at evening twilight and then the Moon passes a half degree south of Saturn around midnight. You can’t miss it.
June 21st: The shortest night of the year – summer solstice. Sadly, this reminds me of winter, which is now where we’re headed.
June 23rd: The Moon is at apogee – 402,200 Km.
June 25th: Last quarter Moon.
That’s a wrap. Keep looking up! And don’t forget Jupiter and her dancing moons – Callisto, Io, Europa and Ganymede!
“The Beginner’s Observing Guide by Leo Enright is an invaluable companion for adventures in the sky. It also contains useful star charts. It can be ordered from the Royal Astronomical Society of Canada at www.rasc.ca/publications. A subscription to our very own excellent Canadian astronomy magazine “SkyNews” can be arranged at the RASC website, as well.
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