Astronomy Picture of the Day 10-04-02

NASA ^ | 10-04-02 | Robert Nemiroff and Jerry Bonnell

[petuniasevan]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2002 October 4

Facing NGC 6946
Credit & Copyright: Robert Gendler

Explanation: From our vantage point in the Milky Way Galaxy, we see NGC 6946 face on. The big beautiful spiral galaxy is located just 10 million light-years away, behind a veil of foreground stars in the high and far-off constellation of Cepheus. Looking from the bright core outward along the loose, fragmented spiral arms, the galaxy's colors show a striking change from the yellowish light of old stars in the galaxy's center to young blue star clusters and reddish star forming regions. NGC 6946 is also bright in infrared light and rich in gas and dust, exhibiting a high star birth and death rate. In fact, during the 20th century, at least six supernovae, the death explosions of massive stars, were discovered in NGC 6946. In this sharp composite color digital image, a small barred structure is just visible at the gorgeous galaxy's core.

[petuniasevan]

Astronomy Fun Fact:

12.5" RC F9, ST10XME, LRGB = 270:20:20:30m is the cryptic notation under this image's original location. 12.5" is of course the telescope's aperture. RC stands for Ritchey-Chretien, a type of Cassegrain telescope. F9 is the focal length of the 'scope. ST10XME is the model number of the CCD camera used. LRGB refers to Luminance Layering technique used on RGB filtered images. RGB itself is Red Green Blue. 270:20:20:30m refers to the times in minutes for each exposure. The Luminance Layering technique combines a high-res unfiltered image with the RGB images to color-correct for a CCD camera's tendency to overexpose in the infrared.

I priced the CCD camera used. JUST the camera is $7000! Nice images though!

[petuniasevan]

[glock rocks]

that is a beautiful photo. thanks.

[BradyLS]

I've always wondered this: How do they account or correct for flaws, if any, in the imaging instruments? I seem to remember, for example, that a radio telescope crew had a delish time accounting for inexplicable noises they were receiving until someone figured out that birds were nesting in the receiving cone. (And I doubt I have the correct terminology for the parts I'm referencing. The kind of scope I'm refering to looks like a GIANT gramaphone speaker, but is used to capture rather than dispense sound.)

[Savage Beast]

NGC 6946 is an absolute hotbed of supernova explosion. And it's practically in our backyard. It's enough to make you crawl back under the bed.

[Molly Pitcher]

This is awesome!! I understand there is a line-up of the sun,moon and earth early Sun. , a 4 year event in its proximity to earth.

Think I've got that right.

[William McKinley]

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[mikrofon]

Seeing that gorgeous galaxy pic and reading your post re: the radio 'scope brought this ditty to mind for some reason... ;^)

[BossyRoofer]

This picture is one of the best yet! Keep up the great work! APOD the place to be!

[petuniasevan]

I'm not sure about how it's done now. I wonder if RadioAstronomer can answer your interesting question.

[BradyLS]

LOL! That DOES look like the cartoon sprial galaxy image that they used to open the show!

[BradyLS]

It was on some NOVA program about radio astronomy and how one of the oldest arrays was still in use. The crew would come in at night and noticed they were receiving steady, regular signals/sound that they couldn't account for. The signals were unique to one set and received the signals no matter which direction it pointed. Like the old Trek episode where they find the missing crewman, they figured out it was like listening to a heartbeat(s) and then when snooping inside the cone and found the nest.