Is this really a spiral galaxy?
The uncertainty of science: The picture to the right, cropped, reduced, and sharpened to post here, was taken by the Hubble Space Telescope and released on March 4, 2024 by the PR department of the European Space Agency (ESA) as part of its Hubble Picture of the Week program. It shows what the press release claims is a spiral galaxy about 55 million light years away, seen edge on.
In this image NGC 4423 appears to have quite an irregular, tubular form, so it might be surprising to find out that it is in fact a spiral galaxy. Knowing this, we can make out the denser central bulge of the galaxy, and the less crowded surrounding disc (the part that comprises the spiral arms).
If NGC 4423 were viewed face-on it would resemble the shape that we most associate with spiral galaxies: the spectacular curving arms sweeping out from a bright centre, interspersed with dimmer, darker, less populated regions. But when observing the skies we are constrained by the relative alignments between Earth and the objects that we are observing: we cannot simply reposition Earth so that we can get a better face-on view of NGC 4423!
This picture provides a great example of the amount of assumptions that are often contained in astronomical observations. Though the data strongly suggests this is spiral, we must remember this is merely an educated guess, based on that central bulge and the dust lanes visible along the galaxy’s profile. There is actually no guarantee that this is so. As the press release also notes, astronomers are constrained by our viewpoint, and cannot change that viewpoint to get a better view to confirm this guess. For all we know, a face on veiw of this flat galaxy would reveal it has no spiral arms, but instead is mottled and chaotic, a rare type that does exist.
Astronomers do the best they can, but it is important that they (and we) always recognize the limitations.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
The uncertainty of science: The picture to the right, cropped, reduced, and sharpened to post here, was taken by the Hubble Space Telescope and released on March 4, 2024 by the PR department of the European Space Agency (ESA) as part of its Hubble Picture of the Week program. It shows what the press release claims is a spiral galaxy about 55 million light years away, seen edge on.
In this image NGC 4423 appears to have quite an irregular, tubular form, so it might be surprising to find out that it is in fact a spiral galaxy. Knowing this, we can make out the denser central bulge of the galaxy, and the less crowded surrounding disc (the part that comprises the spiral arms).
If NGC 4423 were viewed face-on it would resemble the shape that we most associate with spiral galaxies: the spectacular curving arms sweeping out from a bright centre, interspersed with dimmer, darker, less populated regions. But when observing the skies we are constrained by the relative alignments between Earth and the objects that we are observing: we cannot simply reposition Earth so that we can get a better face-on view of NGC 4423!
This picture provides a great example of the amount of assumptions that are often contained in astronomical observations. Though the data strongly suggests this is spiral, we must remember this is merely an educated guess, based on that central bulge and the dust lanes visible along the galaxy’s profile. There is actually no guarantee that this is so. As the press release also notes, astronomers are constrained by our viewpoint, and cannot change that viewpoint to get a better view to confirm this guess. For all we know, a face on veiw of this flat galaxy would reveal it has no spiral arms, but instead is mottled and chaotic, a rare type that does exist.
Astronomers do the best they can, but it is important that they (and we) always recognize the limitations.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Yet another beautiful, interesting image.
Check out the teeny-tiny image of a spiral galaxy in the lower left-hand corner…this one seen face-on.
A timeless and critically important point, Bob! What you cite constitutes the basis for determining how we are to determine the difference between what we claim to know and choose to believe! In the more philosophical aspects of life, a difference of potential consequences that is truly profound!
I can see why they think it is a two armed spiral galaxy, with a little warp up on the left. But i do see the hints of a bent arm on each side.