Ancient Suns website
Stars in the NeighborHood software:
This video will focus on the constellation Cancer the Crab. Cancer is one of the twelve constellations of the zodiac — patterns of stars through which the sun passes during its yearly transit. This Zodiac sign covers the period from June 21–July22, so if your birthday is included in this range, then “happy birthday!”
Cancer is the dimmest constellation of the 12 zodiac members. There are no bright stars in this section of our night skies. At least they’re not bright as seen from Earth. Naturally, the closer you get to a star, the brighter it seems. But there are some very interesting treasures in Cancer.
First, let’s look at the constellation. Here is a screenshot of the software with a constellation outline overlaying the Sky Map closeup.
Constellation Distance View
Here is the same Sky Map view, but in Distance View mode. This shows which stars are closer by their size.
The closest stars in Cancer are dim red dwarfs.
First, we load the Cancer tag file. Start with the software centered at our home Solar system — zero, zero, zero. Then, change the viewing cube size to 104.4 light years (32 parsecs). Next, change the moving speed to 52.2 light years (16 parsecs). Finally, move once in the minus direction along the X-axis, and once in the positive direction for both the Y and Z axes. This puts our home star system in the corner, giving us the largest possible view of Cancer stars.
Second, we go into Star List mode, selecting the Cancer tag and Location within a distance of User-Supplied Coordinates. Here, we’re using light years and type in 20 with the search centered on (0, 0, 0).
The closest star is Gliese 1111 at 11.8 light years distance. Next, is a star which doesn’t appear in many star catalogs, MSDB 1512 at 14.5 light years. And finally, the binary system of Gliese 1116 at 17.1 light years.
The brightest star in the constellation is Beta Cancri, a K4 giant star at 185 light years. Its visual magnitude is 3.52, which is considered moderately weak. Much brighter stars in the field of view are the first magnitude beacons of Castor and Pollux in Gemini, plus Procyon in Canis Minor. Beta Cancri is a binary star with a close companion, thought to be a red dwarf. Next brightest is Delta Cancri in the center of the constellation with a visual magnitude of 3.94, and a distance of 130 light years. The star is a single, K0 giant. This is followed by Iota Cancri, with a magnitude of 4.02, and a distance of 192 light years. This is a double star system with a G7.5 giant primary, and a brilliant blue, A3 dwarf. Finally, we get to Alpha Cancri, with a magnitude 4.25, and a distance of 165 light years. This star is transitioning from sub-giant to giant phase as a brilliant blue, A5 star. The star has a companion estimated to be a K7 dwarf. Gamma Cancri is the last of the 5 brightest stars, with a magnitude 4.72 and a distance of 264 light years. Gamma Cancri is a triple star with an A1 sub-giant (A1IV) primary, a close secondary estimated to be an F4 dwarf, and a wide secondary of an F9 dwarf.
Perhaps the most interesting star is 55 Rho 1 Cancri. So far, scientists have discovered 5 planets in orbit about that distant sun. 55 Cancri is a G8 dwarf at about 42.7 light years distance. Scientists have estimated its age at 10.2 billion years, so it should be leaving the main sequence about now, becoming a sub-giant on its way to becoming a giant star. If any planet in this system developed life on a timetable comparable to Earth’s, it could have a civilization that’s 5.7 billion years old.
There are two noteworthy star clusters in Cancer. M67 (NGC 2682) is an open or galactic cluster. The cluster stands about 10 minutes of Right Ascension west of Alpha Cancri and about 2,770 light years away. The entire cluster has a combined magnitude of 6.1 — barely visible to the naked eye. It wasn’t discovered until 1779. The cluster has about 100 stars similar to our own sun, and the age of the cluster has been estimated at between 3.2 and 5 billion years, making it one of the oldest open clusters known. Even at the minimum estimate, most every star in this cluster is old enough for any planets they may have to have evolved life and possibly an oxygen atmosphere....
Jupiter One, Riot
Open Sea Morning, Puddle of Infinity
Malmo Sunrise, The 126ers
Rust (background): Laitr Keiows (CC BY-SA 3.0)
Cancer chart: IAU and Sky & Tel mag (CC BY 3.0) neg.
Ecliptic path: Tau'olunga (CC BY-SA 3.0)
Cellarius Ptolemaic system (PD)
M67: Palomar STScl WikiSky
M44: NOAO AURA NSF, contr.
NGC 2775: Hubble ST
NGC 2535: NASA (PD)