​IMAGE GALLERY


These are two open star clusters whose only connection is that they are in the same photographic field of Mount Sangre Observatory's telescope and imaging system. The foreground cluster which consists of primarily white and blueish tinted stars in a roughly triangular pattern is called M 35. The background cluster looks smaller and consists of more yellow and reddish stars. It is cataloged as NGC 2158.

This is a lesson in depth of field. Normally, all deep space images look 2D, but these two clusters help give us a sense of the deep structure of the blackness of interstellar space. M 35 is 3,870 light years away and 11 light years average diameter. NGC 2158 is 11,000 light years away and 8 light years average diameter. Both of these clusters are in our Milky Way galaxy, so there is no discoloration from red shift as you would find emitted by galaxies that are hundreds of millions of light years from us. The true colors of these stars belie the fact that NGC 2158 is much older than M 35. M 35 is "only" 175 million years old making its stars just "tweens" on a stellar age scale. So M 35's younger stars shine toward the hotter bluer end of the spectrum. On the other hand, NGC 2158 is approximately 2 billion years old which are young adults compared to our middle age star, the Sun at 4.5 billion years old. Some of NGC 2158's stars are becoming unstable and are leaving the main sequence of stellar evolution. A significant number are in their red giant stage, so they dominate the overall luminosity of the cluster.

The colors help us to determine each star's surface temperature. Like a flame on a gas stove, blue is the hottest followed by white, yellow, and red which is the coolest. If you scan the entire image looking closely at the dimmer stars, you'll find that most of them are red. Many of these stars are red dwarfs which are the most common of all stars. They also live the longest because they fuse their nuclear fuel at a slower rate.

You can easily see M 35 using binoculars, but you'll need a telescope equipped with a high power eyepiece to see both open clusters. You'll neither see as many stars as shown in this image nor the colors because human eyesight is limited to how long exposures can be before they are sent to your brain. This image was taken from the Mount Sangre Observatory telescope on 8 February 2019 stacking fifteen 5 minute exposures through 3 colored filters for a total of 1 hour and 15 minutes total exposure time. These clusters are found near the feet of the constellation Gemini The Twins.

Food for thought: If you only use mathematical odds, what are the chances that there is life on a planet orbiting at least one of the stars in this image? Of course, there's the famous Drake equation. But now, since at least 4,000 exoplanets have been discovered, do we need to tweak that equation?