{"id":59764,"date":"2024-06-05T09:34:04","date_gmt":"2024-06-05T09:34:04","guid":{"rendered":"http:\/\/ac5408a3-6876-447c-9380-c28b0f308bff"},"modified":"2024-06-05T09:39:42","modified_gmt":"2024-06-05T09:39:42","slug":"want-to-locate-a-black-hole-for-yourself-in-the-night-sky-find-out-how-in-our-guide-to-locating-cygnus-x-1","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/want-to-locate-a-black-hole-for-yourself-in-the-night-sky-find-out-how-in-our-guide-to-locating-cygnus-x-1\/","title":{"rendered":"Want to locate a black hole for yourself in the night sky? Find out how in our guide to locating Cygnus X-1"},"content":{"rendered":"

Can you locate the presence of a black hole at Cygnus X-1? <\/p>

By Pete Lawrence\n <\/p>

Published: Wednesday, 05 June 2024 at 09:34 AM<\/p>

\n\n

Cygnus X-1 is a source of X-rays in our Galaxy and the first such source to be attributed to the presence of a black hole.<\/p>

The Cygnus X-1 system was identified as a black hole by Paul Murdin and Louise Webster<\/a> in 1971.<\/p>

A black hole<\/a> is an object so massive that its escape velocity has exceeded the speed of light<\/a>.<\/p>

As a consequence, no light can escape the object, leading to many strange space and time related phenomena.<\/p>

See if you can find HDE 226868, a star in a mutual orbit with a black hole. Click to expand chart. Credit: Pete Lawrence.<\/figcaption><\/figure>

Cygnus X-1 explained<\/strong><\/h2>

From an observational standpoint, Cygnus X-1 is essentially invisible to the naked eye.<\/p>

This isn\u2019t the end of the challenge though, for Cygnus X-1 is one component in a high mass X-ray binary system.<\/p>

The other component is a supergiant variable star<\/a> HDE 226868 (HIP 98298), which shines at mag. +9.0 and can be seen through a small telescope.<\/p>

The objects orbit one another, separated by just 0.2 AU.<\/p>

HDE 226868\u2019s stellar wind removes material from the star, which ends up spiralling around the black hole.<\/p>

The resulting accretion disk<\/a> around the black hole is energetic and hot.<\/p>

This is the source of X-rays that gave away the existence of the HDE 226868\u2019s companion black hole.<\/p>

\"An
An image of the X-ray sources emitted by Cygnus X-1, as seen by the Chandra X-ray Observatory. Credit: NASA\/CXC<\/figcaption><\/figure>

Locating Cygnus X-1<\/strong><\/h2>

If you want to locate black hole Cygnus X-1, the real challenge is to locate HDE 226868.<\/p>

The black hole can\u2019t be seen and this object\u2019s existence and nature will need to be provided by your imagination.<\/p>

The black hole is believed to have a mass equivalent to 21.2 solar masses contained within an effective radius of 44km.<\/p>

Locating a ninth magnitude star isn\u2019t in itself a complex task. However, it\u2019s located in Cygnus<\/a>, against the background of the Milky Way<\/a> and this will make it trickier.<\/p>

The key is to locate the mag. +3.9, naked-eye star Eta (\u03b7) Cygni, which is located in the neck of the Swan between Sadr<\/a> (Gamma (\u03b3) Cygni) and Albireo<\/a> (Beta (\u03b2) Cygni).<\/p>

\"The
The Cygnus and Lyra constellations. Credit: Bernhard Hubl \/ CCDGuide.com<\/figcaption><\/figure>

Look at the mid-point between these two easy naked-eye stars and offset slightly towards Sadr to identify Eta.<\/p>

HDE 226868 is located 25 arcminutes east and 6 arcminutes north of Eta Cygni. To star hop<\/a> to the target, centre up on Eta Cygni.<\/p>

Look 11 arcminutes to the east to find mag. +7.3 HIP 98193. Now head 18 arcminutes east of HIP 98193 to get to mag. +8.9 TYC2678-2291-1, a star of similar brightness to HDE 226868.<\/p>

Drift 8 arcminutes to the north of TYC2678-2291-1 and a fraction west to locate HDE 226868 with a mag. +10 star an arcminute to its north.<\/p>

It may not look that special, but by observing HDE 226858 you\u2019re also looking at a black hole!<\/p>

Have you managed to locate Cygnus X-1 by observing HDE 226858? Let us know by emailing us at contactus@skyatnightmagazine.com<\/a>.<\/strong><\/em><\/p>

This guide originally appeared in the October 2021 issue of <\/strong><\/em>BBC Sky at Night Magazine<\/strong>.<\/strong><\/em><\/p> <\/body><\/html>\n

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