May 31, 2016

The Night Sky:  Early June is good for planet viewing

By GERRY LEBING


The triangle formed by Mars, Saturn, and Antares will continue to parade across the southern sky.  It will be visible near the southeast horizon shortly after nautical dusk on June 1.   Mars is the bright red lead star and Saturn is the trailing star.  Antares, which is also red, is not as bright as the two planets and can be found between them, but a little closer to the southern horizon.

On June 3, Saturn will be at opposition.  That means it will be the brightest it gets.  This is your best chance to get a look at the ringed planet and its moons.  Saturn will be visible all night and, as usual, can be viewed with binoculars. Sometimes, you can make out the biggest moon, Titan, through binoculars, but it's difficult.

On the morning of June 5, Mercury will be at its highest point above the eastern horizon.  This makes it a great time to get up early and view the planet.  Mercury will rise at 4:38 a.m. and probably stay visible until about 5:30 a.m.

Jupiter will start June a little to the south of the zenith.  It will be visible until it sets in the west at about 1:50 a.m.  It will follow this same pattern throughout the month, appearing a little bit more to the west at dusk and setting about two minutes earlier each night. 

The Summer Solstice (for the northern hemisphere) will be on June 20.  That means the days will start getting shorter, but, on the plus side, the nights will get longer and give us more time to look at the stars.

MAY HIGHLIGHTS


May did not offer a lot of clear nights, so I tried to make the most of the clear nights that came along. Surprisingly, the southern skies offered the best views because of the prevailing winds.

This is Messier 83, also known as the Southern Pinwheel Galaxy:



M 83 is about 15 million light-years away.  You can see it through binoculars but its proximity to the southern horizon can make it difficult to spot and identify, even using a telescope.  Its visual magnitude is 7.5.

Here is NGC 5128, also known as Centaurus A.




Centaurus A was discovered in 1824.  It is the fifth brightest galaxy in the night skies.  At a distance of 11 million light years, it is also the closest active galaxy.  Its visual magnitude is +6.8.  Centaurus A is very close to the southern horizon.  I considered myself extremely lucky to get this shot, but May 24 was a lucky night for me.

This is NGC 5139, also called Omega Centauri.



Like I said, the 24th was a lucky night. This globular cluster is closer to the southern horizon than Centaurus A.  It is the brightest globular cluster in the night skies.  In the southern hemisphere, you can see it with the naked eye, but it’s difficult to spot at our northern latitude.  At any rate, I got lucky. 

Centaurus A has a visual magnitude of 3.9.  It’s the largest known globular cluster and is believed to contain more than 10 million stars.  It’s about 18,000 light years away.

MOON PHASES
New moon: June 4
First Quarter: June 12
Full moon: June 20
Last Quarter: June 27

ASTRONOMY TALK

Civil dusk is when the  center of the sun is 6 degrees below the horizon in the evening.  There are a few stars and planets visible at this point, but the sky in the background is still  bright through a telescope.

Nautical dusk is when the center of the sun goes 12 degrees below the horizon in the evening. There is still a bit of sky glow from the sun, but it's usually dark enough to start doing some observing particularly in the eastern side of the sky.  

Astronomical dusk is  when the  center of the sun is at 18 degrees below the horizon. That's the time when the sun doesn't add any sky glow.

Currently, civil dusk is about 40 minutes before nautical dusk.  Astronomical dusk follows about 40 minutes later.  In the winter, there is about 30 minutes between civil dusk and nautical dusk. Similarly, there is about 30 minutes between nautical dusk and astronomical dusk at that time of year.

A planet is said to be in opposition when it is on the opposite side of the Earth from the sun.

Active galaxies are galaxies that have a small core of emission embedded in an otherwise typical galaxy. Models of active galaxies concentrate on the possibility of a supermassive black hole, which lies at the center of the galaxy.


(Gerry Lebing is a retired computer scientist with the U.S. Geological Survey in Washington, D.C.  He has visited Hatteras Island since the mid-1970s. He and his wife, Karen, have owned property here for several years and moved to their home in Waves full-time in 2013.  Astronomy is a subject that Gerry says he has always been interested in and one that he pursues seriously -- he's built an small observatory next to his house. You can send him questions about the night sky through e-mail, [email protected].)

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