The Mannheim Planetarium is now part of the Milky Way Trail

Scaled extension of the Milky Way trail at the Effelsberg radio telescope to the neighboring galaxy NGC 205

December 20, 2021

Since mid-December 2021, a new plaque can be seen on the outside wall of the Mannheim Planetarium, identifying the building as an outpost of the Milky Way Trail at the Effelsberg radio telescope, namely the galaxy NGC 205.

The Milky Way Trail is one of three differently scaled astronomical trails at the Effelsberg radio telescope, covering the complete distance scale from the planets of our solar system to distant galaxies billions of light years away.

Fig. 1: Dr. Christian Theis, director of the Planetarium Mannheim, next to the new plaque "NGC 205" not far from the main entrance to the planetarium.
 

The Milky Way Trail is an installation of the Max Planck Institute for Radio Astronomy and the Effelsberg Radio Observatory. With a diameter of 100 meters, the radio telescope in Effelsberg is the second largest fully steerable radio telescope in the world. The Milky Way Trailshows the distances of various celestial sources on a scale of 1: 1017 (1 : 100 quadrillion) – corresponding to 10,000 light years per kilometer. At this scale, the Milky Way has a diameter of 10 kilometers (or 100,000 light-years) and the distance between Earth and the center of the Milky Way of 25,000 light-years scales to 2.5 kilometers.

In addition to the 18 stations set up along a 4 km stretch near the radio telescope in the Eifel region, there are now two outposts of the Milky Way Trail. Already in 2014, the House of Astronomy (HdA) on the Königstuhl in Heidelberg - at a distance of 250 km from Effelsberg - was identified with the famous Andromeda Galaxy (M31) at the right distance in the scale of the Milky Way Trail. The Planetarium Mannheim became a new outpost, too, identified with the galaxy NGC 205.

NGC 205 is a dwarf galaxy in the Andromeda system and, like the Andromeda galaxy itself,  about 2.5 million light-years away from Earth. The companion is at a distance of 190. 000 light-years (corresponding to 19 km on the scale of the Milky Way Trail) from the Andromeda galaxy itself.

The Andromeda Galaxy is slightly larger than our Milky Way, with a diameter of about 200,000 km corresponding to 20 km on the scale of the Milky Way. It would thus extend from the House of Astronomy in Heidelberg marking for the center of M31 almost to the Mannheim Planetarium in one direction and to Sinsheim in the other. That's quite a large structure at this scale.

Our Milky Way, in comparison, has a diameter of about 170,000 light years or 17 km. With the position of the center directly at the radio observatory Effelsberg (station "Galactic Center" at the viewing plateau directly in front of the 100-m telescope), this corresponds almost exactly to the linear distance of the two cities Bad Münstereifel and Altenahr, which are located northwest and southeast of the radio telescope, respectively, and are just under 17 km apart. Two companions of the Milky Way, the Large and Small Magellanic Clouds, would be 16 and 20 km away from their parent galaxy. Seen from Effelsberg, the two cities Rheinbach and Meckenheim in the vicinity of Bonn could be nicely used as locations for the Magellanic Clouds.

The two stations NGC 205 (Planetarium Mannheim) and M31 (Haus der Astronomie, Heidelberg) also mark the transition to another astronomical trail at the Effelsberg radio telescope. The Galaxy Trail has a scale of 1 : 5 x 1022 (1 : 50 trillions).  In this scale, the Andromeda system with NGC 205 and M31 is located in the immediate vicinity of the Milky Way - at a distance of only 50 cm. The two plaques "Milky Way" and "Andromeda Galaxy" at a distance of only 50 cm mark the beginning of the Effelsberg Galaxy Trail, which leads over a total distance of almost 3 km to distant galaxies several billion light years away.

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Additional Information

The Max Planck Institute for Radio Astronomy has set up a total of four astronomical theme trails at the site of the 100-m radio telescope near Bad Münstereifel-Effelsberg. Three of them, named Planetary Trail, Milky Way Trail and Galaxy Trail, cover the complete astronomical distance scale from the planets of our solar system to distant galaxies several billion light years away.

The Planetary Trail on a scale of 1 : 7.7 billion runs over a total length of 766 m from the visitor parking lot at the radio observatory (station “Pluto”) to the courtyard of the visitor pavilion with the station "Sun". With the neighboring star Sirius, the brightest star in the night sky, the planetary path has an outpost at a distance of 11,000 km (corresponding to 8.6 light years) at MPIfR’s APEX telescope in the Atacama Desert in Chile. 

The Milky Way Trail on a scale of 1 : 1017 (1 : 100 quadrillion) runs over a total length of 4 km (corresponding to 40,000 light years through our home galaxy) from the outer regions of the Milky Way along the Sun to the Galactic Center. The course of the Milky Way Trail leads from Burgsahr (part of the municipality Kirchsahr in the Sahrbach valley) to a viewing plateau directly in front of the 100-m radio telescope. The Milky Way Trail has two outposts, the Andromeda galaxy M31 (at the Haus der Astronomie/Heidelberg) and the galaxy NGC 205 (at the Mannheim Planetarium), each at a distance of 2.5 million light years or about 250 km.

The Galaxy Trail on a scale of 1 : 5 x 1022 (1 : 50 quadrillion) runs over a total length of 2.7 km (corresponding to almost 14 billion light years) from our Milky Way to distant galaxies and leads finally back to the Big Bang or the beginning of all time. It starts on a forest path behind the radio telescope and finishes at the Martinshütte of Kirchsahr, the "barbecue hut at the end of the universe".

For the 50th anniversary of the 100-m radio telescope, a fourth hiking trail has been added in 2021. The "Time Travel Trail" depicts the 50-year history of the Effelsberg radio telescope on a total of 20 stations. It leads around the telescope on a length of 5 km, with the starting point directly at the visitor pavilion.

 

Fig. 2: The 100-m radio telescope near Bad Münstereifel-Effelsberg. A short zigzag path leads from the visitor pavilion to a viewing plateau directly in front of the telescope. The plateau is the position of the plaque "Galactic Center", marking the terminal station of the Milky Way Trail.

 
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