Star Spy: Ball of stars
FREIDL HALE - TEKAPO STARLIGHT
Another ball of stars
In our sky, this lovely globular cluster called 47 Tucanae, usually pronounced ‘too-con-eye’ or ‘too-can-eye’, is located near the Small Magellanic Cloud.
In space it is nearly 200,000 light-years closer to us than the SMC, a mere 17,000 light-years distant within our own galaxy, and more than a whopping 100-light years across.
At its distance from us, it occupies about the same amount of sky as the full moon.
But all we see with our naked eyes (unaided by binoculars or telescopes etc) is a small point of light.
Visible in a dark sky to the south, away from city lights and with little or no moon, it appears to be a dim or slightly fuzzy star immediately above the Small Magellanic Cloud.
The waning moon is rising later each night, so if the weather cooperates, for a couple of weeks there should be lots of opportunity to find it.
Keep in mind, when looking for it, that throughout the night and the year its position with respect to the Cloud changes as they rotate clockwise around in the southern sky.
When viewed through a telescope, the reason for its slight fuzziness is readily apparent.
47 Tucanae, or ‘47 Tuc’ for short, has a bright central core of densely packed stars, evenly surrounded by a spreading sphere of more stars.
Looking at it through a telescope I feel drawn into it, and it seems as though I should be able to count the individual stars.
But it would be a difficult task, as it is thought to contain well over half a million of them.
Because of its symmetry and clarity, 47 Tucanae is a favourite object for telescope and binocular viewing in the Southern Hemisphere.
The number 47 derives from an obscure catalogue of stars, no longer in use, in which it was the 47th object listed.
It is part of a faint constellation known as Tucana, the Toucan.
Some say the Small Magellanic Cloud is an egg on which the Toucan sits.
Jupiter near the Moon
If you are up late on Friday night, take a few moments to go outside and look to the east.
By 1am in most of the country you should see the moon and Jupiter close together just above the horizon.
The first up will be the moon, followed within 20 minutes or so by Jupiter.
The reason they can be so close together is the same reason that Mars and Saturn have been hanging around the bright star Spica in the west.
All of these objects travel across the sky along nearly the same path.
The path is called the ecliptic.
It is the path the Sun takes across our sky and around the Earth.
We saw last week how the Earth’s equator is tilted 23.4 degrees to the plane of the Sun and the planets; tilted away from the equator of the Sun.
Because the orbits of the planets align closely with the equator of the Sun, they all follow roughly the same path across our sky.
While most of the moons of the other planets orbit above their planet’s equator, our Moon is off, another slightly wonky feature.
It circles Earth between the ecliptic and the equator, a little over five degrees from the ecliptic.
This means it aligns closely, within about five degrees, to the path taken by the Sun and the planets.
You can see that with all of these celestial bodies following close to the same path in our sky, all going by at different speeds, the chances of one crossing in front of another every once in a while are pretty good.
When this happens it may be called an eclipse, an occultation, or a transit.
The word ecliptic is derived from the same Latin and Greek roots as the word eclipse.
Because the star Spica is located above the ecliptic, it was recently occulted by the Moon, on August 22.
- © Fairfax NZ News
Do you believe Bigfoot exists?Related story: (See story)
The cost of losing nature