Sextans

Sextans is a group of stars.

A man named Johannes Hevelius named it. He used a tool for looking at stars. A fire destroyed his tools once. He named this group after that tool.

This group is very faint. It looks like a square in the sky. The Moon and some planets pass through it. You can see it from most lands.

There is a big galaxy there too. It is very far away. It is a special place to study the sky.

Sextans is a faint group of stars in the sky.

A man named Johannes Hevelius named it in 1687. He used a tool called a sextant to look at stars. A fire destroyed his tools in 1679. He named the stars to remember that tool. Sextans is a medium-sized group of stars. It sits near the celestial equator. This means most people on Earth can see it. The Moon and some planets pass through it often.

There are many stars in this area. The brightest star is Alpha Sextantis. It is 280 light-years away. Another star is called Gamma Sextantis. It is actually two stars that circle each other. They take about 77 years to make one circle. Some stars in Sextans are part of groups of three stars.

Scientists also look at far objects here. There is a galaxy called NGC 3115. There is also a group of galaxies called CL J1001+0220. This group is 11.1 billion light-years away. It is one of the most distant groups known. Scientists use the Hubble Space Telescope to study this area. They look for very old stars there. These stars helped make the elements needed for life.

Sextans is a faint constellation in the night sky. It sits right on the celestial equator. This means people in most parts of the world can see it. The constellation is medium-sized in the sky. It borders the constellation Leo to the north. It also touches Hydra to the southwest and Crater to the southeast.

Because it is near the ecliptic plane, the Moon and planets often pass through it. They usually cross through its northeastern corner.

This group of stars has a very interesting history. A Polish astronomer named Johannes Hevelius introduced it in 1687. He originally called it Sextans Uraniae. The name comes from a tool called a sextant. Hevelius used this tool to watch the stars. He lost his own sextant in a fire. This fire destroyed his observatory on 26 September 1679. He named the constellation to remember that lost instrument.

Many different people have studied the stars in Sextans. John Flamsteed labeled 41 stars in this area. Later, Benjamin Apthorp Gould gave letters to the brightest stars. He used Greek letters like Alpha and Epsilon. There are 38 stars that are bright enough to see easily. The brightest one is Alpha Sextantis. It is an aging star located 280 light-years away.

Another star is Gamma Sextantis. This is actually two stars that orbit each other. They take 77.55 years to complete one circle.

Sextans also holds many deep-sky objects. One is a galaxy called NGC 3115. It is an edge-on lenticular galaxy. You can also find the dwarf galaxy Sextans B here. It is 4.3 million light-years away. One of the most amazing things is a galaxy cluster. It is named CL J1001+0220. This cluster is 11.1 billion light-years away. It is one of the most distant known clusters.

Scientists use big tools to study this part of space. The Hubble Space Telescope uses this area for the COSMOS project. They look for very old stars called population III stars. These stars lived in the very early universe. They helped make the chemical elements we need for life. These elements are needed to build planets. Without these stars, life as we know it might not exist.

Sextans is a faint, medium-sized constellation located on the celestial equator. Because it sits on this central dividing line in the sky, it is visible from most parts of the world. It shares borders with several other constellations. To the north, it meets Leo. To the southwest, it touches Hydra. To the southeast, it borders Crater. The International Astronomical Union adopted the three-letter abbreviation "Sex" for this constellation in 1922.

The official boundaries of Sextans were defined by the Belgian astronomer Eugène Delporte in 1930. He established these borders as a square shape. In the equatorial coordinate system, the right ascension coordinates of these borders fall between 10h 0m and 11h 30m. The declination coordinates range from +6.43° to −11.7°. Because Sextans is located close to the ecliptic plane, the Moon and various planets regularly cross through it. These celestial bodies often pass through the northeastern corner of the constellation.

The history of Sextans is tied to a personal loss for its creator. Polish astronomer Johannes Hevelius introduced the constellation in 1687. He originally called it Sextans Uraniae. The name refers to the astronomical sextant, which is a tool used for making observations. Hevelius used this instrument frequently in his work. He named the constellation to remember the sextant he lost during a catastrophe. On 26 September 1679, a fire destroyed his observatory. Despite this loss, Hevelius rebuilt enough equipment to observe the great comet of December 1680.

Many astronomers have worked to catalog the stars within these boundaries. John Flamsteed originally labeled 41 stars in the constellation. Later, Francis Baily intended to give Bayer designations to some stars. However, he did not give them letters because none were above magnitude 4.5. Eventually, Benjamin Apthorp Gould labeled the five brightest stars using Greek letters from Alpha (α) to Epsilon (ε). In total, there are 38 stars in Sextans with an apparent magnitude of 6.5 or brighter.

The individual stars in Sextans show many different characteristics. Alpha Sextantis is the brightest star in the group. It has an apparent magnitude of 4.49, making it the only star in the constellation above the fifth magnitude. It is an aging A-type star located 280 light-years away. At 385 million years old, it is exhausting the hydrogen in its core. This process means it is leaving the main sequence. Gamma Sextantis is the second brightest star, with a magnitude of 5.05. It is a binary star system consisting of two A-type main-sequence stars. These two stars orbit each other in an eccentric orbit every 77.55 years. They are also 280 light-years away. Their separation is only four-tenths of an arcsecond. This makes them difficult to see without a telescope with an aperture of at least 30 cm.

Sextans also contains complex multiple star systems. The system 35 Sextantis is a triple star system. It contains two evolved K-type giants that have equal mass. Both of these stars are twice as massive as our Sun. The secondary star is also a single-lined spectroscopic binary. This means it has a companion star that is difficult to see. This entire system is located approximately 700 light-years away. The outer pair of stars takes roughly 23,000 years to orbit one another. Within that, the B subsystem orbits in 1,528 days. There are also notable variable stars in this area, such as 25, 23 Sextantis, and LHS 292.

Beyond individual stars, Sextans holds deep-sky objects that connect us to the wider universe. The only noteworthy galaxy in the constellation is NGC 3115. This is an edge-on lenticular galaxy. The constellation also contains Sextans B, which is a dwarf irregular galaxy. Sextans B is 4.3 million light-years away and is part of the Local Group of galaxies.

Astronomers use Sextans to study the very distant universe through the COSMOS project. This project was undertaken by the Hubble Space Telescope. One find in this field is the galaxy cluster CL J1001+0220. As of 2016, this is the most distant known galaxy cluster. It is located 11.1 billion light-years from Earth at a redshift of z=2.506. In June 2015, scientists found evidence of population III stars in the Cosmos Redshift 7 galaxy. These stars likely existed in the very early universe. They may have started producing the heavy chemical elements needed to form planets and life.