Looking Up: 220 Million Years Old... Eh, You're Just A Kid

Sep 4, 2017

Credit Dieter Willasch (Astro-Cabinet) / nasa.gov

This week on Looking Up Hal directs our attention to an open cluster of stars located in the tail of the Scorpion.

We’ve talked before about the constellation Scorpio, and how, unlike so many other constellations, it actually looks like its name – a scorpion. High in the southern Colorado sky right now, the scorpion has a beautiful straggler following behind the stars that make up the stinger – the gorgeous bunch of stars known as Ptolemy’s Cluster.

This open cluster is easily visible to the naked eye, if you are away from city lights. In town, you may need binoculars or a small telescope to find this gem. You won’t be the first! The cluster has been known for many years. Can you guess who first recorded seeing Ptolemy’s Cluster in the night sky? If you guessed Ptolemy, you are right, in 130 AD. Charles Messier named it as his 7th object in his famous catalogue, and others, such as Edmund Halley, charted it as well.

About 80 stars show up in a telescope, from a distance of just under 1000 light years. The cluster itself is about 22 light years across, and is filled with fairly young stars, averaging about 220 million years – babies!

When you gaze at these exquisite stars, ponder all the folks over the last 1900 years or so who also stared up in wonder and awe. You’re part of a cool group.

If you’d like to take a closer look at Ptolemy’s Cluster or any of the wonderful and amazing things in the sky, please visit csastro.org for a link to information on our monthly meetings and our free public star parties.