The Constellation Gemini, Photographed with an iPhone (2018)

Here are some photos of the constellation Gemini, and neighboring stars, taken with an iPhone, in the spring of 2018 from Edmonton Alberta (latitude 54). The pictures have been enhanced via the Gimp colour filter for brightness and contrast, increasing both brightness and contrast to bring out the less bright stars. The accompanying picture is an inverted version of the first, swapping bright pixels for dark, as it can be easier to see some of the more subtle stars that way.

From a bright city sky, you can’t necessarily make out many stars. Castor and Pollux, the twins, are easy to see, however. In the above pictures, the star Beta Geminorum is also known as Pollux, while Alpha Geminorum is known as Castor. These twins of ancient mythology are easy to make out, as they are both magnitude 1 stars (e.g. Castor about 1.6, Pollux about 1.1, both very bright). Their brightness is a combination of their inherent large size and their relative nearness to Earth.

Castor is a triple star system (actually 6 stars, but only 3 are visible, with each of them being a spectroscopic binary). Two of the stars can be split in a small to moderate size amateur telescope. The brightest of the group is about magnitude 1.9, but the contribution of light from the other stars in the group bring the overall magnitude to about 1.6. The largest components are bigger than our sun, and the distance to the system is about 51 light years or about 16 parsecs.

Pollux has a slightly orange tint to it. It is probably variable (varies in brightness). It is actually quite close to the Earth, at about 34 light years, or about 10 parsecs. In fact, it is the closest giant star to the Earth. It has at least one planet, a hot Jupiter of about 2 to 3 Jupiter masses, that orbits at about 1.6 Astronomical Units (about 150 million miles).

In the second picture, I used the Gimp sparkle filter to punch up the view a bit. This filter enhances bright spots in the picture, and can add spikes to really bright points. This is a bit reminiscent of what star maps look like, with brighter stars shown as bigger. You can easily see how Pollux and Castor outshine the other stars in Gemini.

Here’s a close-up map of the same stars, from Sky and Telescope, with the iPhone photo placed side by side.

Here’s the same image, but with the constellation lines for Gemini drawn into the iPhone picture. You can see how the iPhone did a pretty good job of capturing the main stars of the constellation, though not all of them.

Some other highlights of Gemini:

Gamma Geminorum is also bright, at magnitude 1.9, and is bout 109 light years away. It’s about 3 times the size of our sun.
Delta Geminorum is about magnitude 3.5, about 60 light years away.
Epsilon Geminorum is a double star, about magnitude 3.5 and is about 60 light years distant. It can be split in a moderate amateur telescope.
Epsilon is another double, about 900 light years distant, that can be split in by binoculars or small scopes.
Zeta is also a double star, which can be split in binoculars or small scopes. It is about 1200 light years distant, and is a Cepheid variable, a “standard candle” used by astronomers to estimate distances to other stars
Kappa is another binary, but hard to split because the stars are not well separated.
Eta is another double that can be split.
The M35 open cluster is in Gemini. That’s a bunch of stars that are gravitationally bound and close together, as seen from the Earth.
The Eskimo nebula is a nice planetary nebula, the last stages in a star’s evolution. It somewhat resembles a person’s head, wearing a fringed parka.
The Medusa nebula looks rather like its namesake. It’s a planetary nebula, but hard to see in an amateur telescope
There are a number of other deep-sky objects, mainly open clusters of the NC category.
The Geminids meteor shower is a big show in December.
A recent finding is that a wandering red dwarf star probably came near our solar system about 70,000 years ago. It would have been seen in the region of Gemini, by ancient humans, but only if it flared, as red dwarfs tend to do. It may have perturbed some comets in the far reaches of the solar system, though there were no major impacts known at that time, so probably nothing hit the Earth.

In Greek mythology, Pollux was the son of Zeus. To get the full story, read the Wiki article.

https://en.wikipedia.org/wiki/Castor_and_Pollux

“Leda and the Swan” is a famous poem by Yeats, related to Pollux. Warning: Zeus was a pretty crazy God.

https://www.poets.org/poetsorg/poem/leda-and-swan

In modern mythology, Pollux is notable for being the setting of one of the original Star Trek episodes, “Who Mourns for Adonis”.

Sources:

Wiki

Google Images

Stargazing (Collins)

Space.com

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