Iris Nebula
| Polish version is here |
In the northern sky, amidst the stars that form a quiet, twinkling canvas at night, lie numerous fascinating constellations (Photo 1). Among them, it's impossible not to notice Ursa Minor — the Little Bear, or the Little Dipper — which, although less striking in appearance than its larger counterpart, Ursa Major, plays a crucial role in celestial navigation. It is home to Polaris, or the North Star (α Ursae Minoris), a star positioned so close to the celestial pole that it appears nearly motionless in the sky. Its constancy has made it a reliable guide for sailors, travelers, and astronomers throughout the ages.
Nearby lies the constellation Draco — the Dragon. It is often identified with Ladon (Gr. Λάδων), the mythical serpent who guarded the garden of the Hesperides and the golden apple tree given to Hera as a wedding gift. This constellation was known to many ancient cultures. About 80 stars within Draco are visible to the naked eye. In Poland, Draco can be observed year-round, although it's best viewed during the spring and summer months.
Another constellation visible in this region is Camelopardalis — the Giraffe. Though it lacks particularly bright stars, it makes up for this with its vast coverage of the sky. It's considered one of the younger constellations, introduced in 1613 by the Dutch astronomer, geographer, and clergyman Petrus Plancius. He designated this area of the sky — once believed by the ancient Greeks to be nearly starless — by connecting fainter stars, none brighter than fourth magnitude. For persistent stargazers, Camelopardalis presents a delightful challenge and a good exercise in navigating the dimmer regions of the celestial sphere.
Also easily spotted is Cepheus, representing the mythological king of Ethiopia, husband of Cassiopeia and father of Andromeda — all immortalized in neighboring constellations. Though he played a minor role in the myth of Andromeda’s rescue by Perseus, Poseidon honored (or perhaps punished) him by placing him in the sky with only modest stars.
Among all these constellations, Cassiopeia — queen of the northern sky — stands out with her distinctive "W" (or "M") shape, making her one of the easiest constellations to identify. According to legend, Cassiopeia’s vanity brought divine wrath upon her family. Today, her celestial form is a delight to observe and a helpful reference point for beginner astronomers. Cassiopeia lies along the plane of the Milky Way, making it rich in open clusters and other intriguing objects to explore.
To the southeast of Cepheus and Cassiopeia lies the small constellation Lacerta — the Lizard — introduced in the 17th century by Polish astronomer Johannes Hevelius.
Near Cepheus lies our main object of interest: the Iris Nebula, also known as NGC 7023. This reflection nebula is located within the boundaries of the Cepheus constellation and was discovered on October 18, 1794, by William Herschel. It is situated about 1,400 light-years from Earth.
Observations
March 21, 2025, around 11:00 PM – Kamienica Polska (Poland)
Conditions: rural, relatively low light pollution
You never know when a great observation opportunity will present itself — which is why it’s always wise to be prepared. This time, I was on a short trip, invited to teach a class at a friendly school outside the city. I wasn’t expecting anything special — just a quick getaway. After the class, as I was unwinding at the hotel, I looked out the window and was struck by the sight of a breathtakingly clear sky — deep, vast, and studded with thousands of stars, brilliantly visible far from urban light pollution. Fortunately, in keeping with my golden rule, I had brought along my handy travel telescope. I set it up on the hotel terrace, surrounded by the quiet of the countryside, aimed it at the sky, and began collecting light — photons that had traveled across light-years of space to finally reach my eye and the telescope’s lens. That’s how the photo below was taken (Photo 2).
The Iris Nebula lies at the northern edge of a vast molecular cloud, which remains virtually invisible in optical wavelengths. Its glow comes from the bright star SAO 19158, hidden behind dense layers of gas and dust. The star’s blue light reflects off tiny dust particles, giving the nebula its distinctive hue. Additionally, the Iris Nebula emits large amounts of infrared radiation, produced by the microscopic dust grains suspended within it.
Parametry fotografii 2:
- Total exposure time: 90 minutes (stack of 360 RAW frames at 15s each)
- DWARF3
- Lens: f=150mm (aperture: 35mm)
- Mount: photographic tripod
Further readings:
- Pasachoff J.M., Atlas of the Sky, Peterson Field Guides, New York, 2000, p. 578
- Caldwell-Moore P., Firefly Atlas of the Universe, Firefly Books Limited, 2003
- O’Meara S.J., The Caldwell Objects, Cambridge University Press, Cambridge, 2016, pp. 30-33
- König M., Binnewies S., Bildatlas der Sternhaufen & Nebel, Kosmos, Stuttgart, 2023, p. 75
Marek Ples