June 2018

Each month I will describe sights of interest in the night skies of South Carolina. These sights will be broken down into four sections; what you can see with the naked eye, with binoculars, with a small refracting telescope and with a Dobsonian reflector. The best time to view the night sky is at and around the times when the Moon is not visible, what is known as a New Moon; which will occur this month on June 13th. For June, your best viewing nights will be from June 1st to the 18th. The Star chart below is set for Florence, SC on June 15th at 10 pm. Note: A new table of contents for earlier columns is located in this January 2018 column.

Where and When Can I See the Southern Cross?

This question was asked by one of our young amateur astronomers recently. I answered where in the negative; not visible in South Carolina. Also, how about the closest star, the Alpha Centauri system; not visible in South Carolina. So where and when?

Let’s start with locations. First, the Southern Cross, known as the constellation Crux and Alpha Centauri, also called Rigel Kentaurus are nearby each other, so if you can see one, you can see both. So can they be seen anywhere in the United States? Yes, two places. First is from the Hawaiian Islands. In the contiguous United States, your best chance is Key West. In theory, you can see them from Miami, but observation requires a clear dark southern horizon which is difficult to find in the Miami area. Key West has a clear southern horizon over the Gulf of Mexico.

As you are aware, the closer to the horizon, the more difficult it is to view celestial objects due to haze and thickness of the atmosphere. So your best chance to see these objects is on a cruise ship or a vacation to a Caribbean island. Many people enjoy cruising. Any cruise you take which travels south of Cuba will offer a good view of Crux and Rigel Kentaurus. The farther south you cruise, the higher these objects will be in the sky; see “below this line” Caribbean map below.

Next we must address the time of year factor. In the Florence area you must wait until winter to see Orion, and wait until summer to see Scorpius. To see Crux and Rigel Kentaurus from the Caribbean, the best time is March through May. In March, these objects will be at peak height from 1am to 2am. In May they will peak from 9pm to 10pm. So plan your trip or cruise accordingly. If you vacation in Cancun or Cozumel Mexico they are easily visible once you move away from the hotel lights. If you vacation in Puerto Rico they are even higher in the sky. I traveled to Cozumel, Mexico every year for twenty years. Reason, scuba diving in the day and star gazing at night. Every year I traveled between March and May, and I always looked to the southern sky each night to enjoy the view of Crux; below is the view I would see.

Note: Don’t forget to carry binoculars with you on vacation; for the amateur astronomers, binoculars are a necessity.

Crux:

Crux is a southern hemisphere constellation. It was first reported by the Greeks several thousand years ago, and then as time went by, it disappeared; hold this thought. For the people of the southern hemisphere it is a well-known sight. Indeed it is so popular that it appears on five country flags in the southern hemisphere; Australia (shown below), New Zealand, Brazil, Papua New Guinea and Samoa.

As you know we have a Northern Cross in our night sky, part of the constellation Cygnus the Swan. The Northern Cross has six bright stars, resulting in a while defined cross (Christian cross). However, the Southern is much smaller, and is defined by only four stars with a misplaced smaller star. Below is a comparison of the sizes of the two crosses.

Crux also contains two interesting objects. First is a small star cluster known as the Jewel Box and second is a dark nebula known as the Coal Sack.

The Jewel Box is easily seen with a pair of binoculars, but requires a telescope to enjoy its beauty as seen below.

The Coal Sack is only noticed under very dark skies. Also notice the position of our nearest star system Alpha Centauri in relation to Crux.

Remember the Greek’s disappearing Southern Cross. The Cross disappeared because of the Earth’s precession, wobble. The Earth’s 26,000 year wobble results in apparent movement of the constellations in the sky. Over a period of a few thousand years, the Southern Cross slowly disappeared below their southern horizon.

As an interesting side note, between 7000 BC and 1000 AD, Native Americans resided in South Carolina at a time known as the Archaic Period. Below is the sky as seen by South Carolina’s Native Americans in the year 4000 BC; over 6000 years ago.

Surprise! 6000 years ago the Southern Cross was easily visible from Florence, SC. Therefore, it will be visible again in Florence in another 20,000 years; mark your calendar.

A final trivia note: In Hawaii and Key West in mid-June you can see both the Northern and Southern Crosses close to the horizon at the same time (better in Cozumel). You can do the same thing in Australia in September.

 

Naked Eye Sights: Take a vacation and/or cruise to the Caribbean to see the Southern Cross and closest star to our solar system, Rigel Kentaurus (Alpha Centauri). At home at 10pm on June 15th you can see Venus in the west, Jupiter in the south and Saturn in the southeast.

Binocular Sights (7 to 10 power): Jupiter’s moons.

Big Binocular Sights (18 to 25 power): Jupiter and Saturn’s rings (at 25 power).

Telescope Sights (60-100mm): Jupiter and Saturn.

Dobsonian telescope (6 -8 inch): Jupiter and Saturn.

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