APOD: M51: The Whirlpool Galaxy in Dust... (2013 Feb 24)

[APOD Robot]

M51: The Whirlpool Galaxy in Dust and Stars

Explanation: The Whirlpool Galaxy is a classic spiral galaxy. At only 30 million light years distant and fully 60 thousand light years across, M51, also known as NGC 5194, is one of the brightest and most picturesque galaxies on the sky. The above image is a digital combination of a ground-based image from the 0.9-meter telescope at Kitt Peak National Observatory and a space-based image from the Hubble Space Telescope highlighting sharp features normally too red to be seen. Anyone with a good pair of binoculars, however, can see this Whirlpool toward the constellation of the Hunting Dogs (Canes Venatici. M51 is a spiral galaxy of type Sc and is the dominant member of a whole group of galaxies. Astronomers speculate that M51's spiral structure is primarily due to its gravitational interaction with a smaller galaxy just off the top of the image.

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[/b]

[Beyond]

Looks like The Whirlpool could use a visit from The Hoover.

[Ann]

This is a classic image of what is arguably the most classic of all the spiral galaxies in the sky (from our point of view, of course!).

I like the hint of a dust lane across the nucleus. It looks like a tiny, tiny bar. In fact, there is not just one, but two dust lanes crossing the nucleus! Here is a Hubble image of the two dust lanes crossing the nucleus and the central black hole of M51 - "X" marks the spot!

APOD Robot wrote:
Astronomers speculate that M51's spiral structure is primarily due to its gravitational interaction with a smaller galaxy just off the top of the image.

M51 and NGC 5195.
Photo: Philip Ammar.

Fascinatingly, I once read that M51 may have been a spiral galaxy with much shorter arms, before it started interacting so much with NGC 5195. In Philip Ammar's picture, you can see how the inner parts of the spiral arms - the parts that you can see in today's APOD - are strikingly regular and semi-circular, while the outer parts are "drawn-out" and full of kinks. The source I read claimed that the inner parts of the arms are "original", while the outer parts are a product of the galactic interaction.

I don't remember the name of the source that made that claim, so of course I can't vouch for its veracity in any way at all. But I've always thought that the suggestion was interesting. It makes me wonder where, if the claim is true, the original arms end and the "extensions" start. Well, Philip Ammar's picture demonstrates that the old yellow population of M51 extends a long way along one of the arms, past the most intensely blue elongated "string" of star formation.

It's always nice to get a reason to muse over this beautiful, classic galaxy!

Ann

[ErnieM]

The January 25, 1997 APOD says M51 is 15 million light years distant. Here is the link : http://apod.nasa.gov/apod/ap970125.html
Today;s APOD says twice as far at 30 million light years. Has space expanded this much in 16 years?

[Night eyes]

What a stunningly beautiful image. Thanks to all of you for the tidbits of information to further explore.

[orin stepanek]

This link

light years

doesnt work. All i get is a white screen!

[Psnarf]

All i get is a white screen

That's a visual representation of what you'd see if you were traveling at light speed. Check back next year to see what's at the end of one light year.

One light-year is equal to 9.5 x 10¹⁵(that's 9,5000,000,000,000,000!) meters. -[from the aforementioned URI at Lansing State]

[bystander]

This link

light years

doesnt work. All i get is a white screen!

Works for me

What is a light year?

(Lansing State Journal, Jan. 22, 1992)

---

The light-year is probably the most misused scientific term in the popular literature. If you watch old science-fiction films carefully, you may hear the characters using the light-year as a unit of time - which it is not! The light-year is actually a unit of distance commonly used in astronomy. Astronomy is the scientific study of the universe beyond the Earth: planets, stars, galaxies and solar systems. Because of the size of these objects and the distances between them, measurements and calculations often require working with very large numbers. Specialized units - such as the light-year - make these calculations much less cumbersome.

A light-year is defined as the distance light travels during one year. Light from the sun travels with a speed of about 300,000,000 meters per second. By multiplying the speed of light by the number of seconds in one year, we find that one light-year is equal to 9.5 x 10¹⁵ (that's 9,5000,000,000,000,000!) meters. To give you an idea of how large a distance this is, the average separation of the Earth and the Sun is about 1.5 x 10¹¹ meters. This means that, in order to travel a distance of one light-year, one would have to make 32,000 round trips between the Sun and the Earth! Use of the light-year allows astronomers to write, for example, the distance between the Earth and the nearest stars beyond the Sun as 4 light-years, instead of 38,000,000,000,000,000 meters. The light-year is just one of a number of specialized units which have been defined by scientists in order to make measurements and calculations involving very large (and very small) distances more convenient.

---

[Chris Peterson]

The January 25, 1997 APOD says M51 is 15 million light years distant. Here is the link : http://apod.nasa.gov/apod/ap970125.html
Today;s APOD says twice as far at 30 million light years. Has space expanded this much in 16 years?

The distance between us and M51 has not changed measurably in 16 years. We simply don't know how far away it is, beyond "more than 15 million ly" and "less than 35 million ly".

Measuring distance in our Universe is one of the most challenging things astronomers do, and in many cases the uncertainty on those measurements is large- particularly as different methods sometimes yield very different results.

[Ann]

I appreciate being told these numbers. I have sometimes tried converting light-years to kilometers, and I have always failed. So it's 38 trillion kilometers, then. How do you say the other number - nine point five trillion kilometers? I tried to say it in Swedish, where a "trillion" is of course a "biljon", but in any case it sounded wrong. I found myself reading 9,5000,000,000,000,000 as "ninety-five trillion" and then getting confused at the obvious thirty-eight trillion (38,000,000,000,000,000) which seemed to small to be four times 9,5000,000,000,000,000. Maths and I are not good friends!

The distance is certainly impossible to imagine, in any case. When I made a model of the inner solar system, I found that I couldn't even really imagine the distance between the Earth and the Sun. I tried to picture myself sitting in a fantastically heat- and radiation-proof spaceship traveling to the Sun, and I tried to imagine the actual distance the spaceship would have to travel to reach the Sun. I couldn't find a way to make this distance understandable in terms that I am the least familiar with.

Ann

[bystander]

nine point five trillion kilometers

That's meters not kilometers.

I have sometimes tried converting light-years to kilometers

60 * 60 * 24 * 365.25 * 299,792,458 / 1,000 = 9.46 * 10¹² km

[Chris Peterson]

The distance is certainly impossible to imagine, in any case. When I made a model of the inner solar system, I found that I couldn't even really imagine the distance between the Earth and the Sun. I tried to picture myself sitting in a fantastically heat- and radiation-proof spaceship traveling to the Sun, and I tried to imagine the actual distance the spaceship would have to travel to reach the Sun. I couldn't find a way to make this distance understandable in terms that I am the least familiar with.

I've been driving the same car for 20 years. In that time, I've traveled the distance to the Moon, and am now about 20% of the way back to the Earth.

From Kim Stanley Robinson's book 2312, set in a heavily colonized Solar System, a passage about the plan to send one of the moons of Pluto out on a 1000 year journey to the stars:

Sorry, but it's true. It has to be said: the stars exist beyond human time, beyond human reach. We live in the little pearl of warmth surrounding our star; outside it lies a vastness beyond comprehension. The solar system is our one and only home. Even to reach the nearest star at our best speed would take a human lifetime or more. We say "four light-years" and those words "four" and "years" fool us; we have little grasp of how far light travels in a year. Step back and think about 299,792,458 meters per second, or 186,282 miles per second - whichever you think you can grasp better. Think of that speed as traversing 671 million miles in every hour. Think about it traversing 173 astronomical units a day; an astronomical unit is the distance from the Earth to the Sun, thus 93 million miles - crossed 173 times in a day. Then think about four years of days like that. That gets light to the nearest star. But we can propel ourselves to only a few percent of the speed of light; so at 2 percent of the speed of light (ten million miles an hour!) it will take about two hundred years to go those four light-years. And the first stars with Earthlike planets are more like twenty light-years away.

It takes a hundred thousand years for light to cross the Milky Way. At 2 percent of that speed - our speed, let us say - five million years.

The light from the Andromeda Galaxy took 2.5 million years to cross the gap to our galaxy. And in the universe at large, Andromeda is a very nearby galaxy. It resides in the little sphere that is our sector of the cosmos, a neighbor galaxy to ours.

So. Our little pearl of warmth, our spinning orrery of lives, our island, our beloved solar system, our hearth and home, tight and burnished in the warmth of the sun - and then - these starships we are making out of Nix. We will send them to the stars, they will be like dandelion seeds, floating away on a breeze. Very beautiful. We will never see them again.

[orin stepanek]

This link

light years

doesnt work. All i get is a white screen!

Works for me

What is a light year?

(Lansing State Journal, Jan. 22, 1992)

---

The light-year is probably the most misused scientific term in the popular literature. If you watch old science-fiction films carefully, you may hear the characters using the light-year as a unit of time - which it is not! The light-year is actually a unit of distance commonly used in astronomy. Astronomy is the scientific study of the universe beyond the Earth: planets, stars, galaxies and solar systems. Because of the size of these objects and the distances between them, measurements and calculations often require working with very large numbers. Specialized units - such as the light-year - make these calculations much less cumbersome.

A light-year is defined as the distance light travels during one year. Light from the sun travels with a speed of about 300,000,000 meters per second. By multiplying the speed of light by the number of seconds in one year, we find that one light-year is equal to 9.5 x 10¹⁵ (that's 9,5000,000,000,000,000!) meters. To give you an idea of how large a distance this is, the average separation of the Earth and the Sun is about 1.5 x 10¹¹ meters. This means that, in order to travel a distance of one light-year, one would have to make 32,000 round trips between the Sun and the Earth! Use of the light-year allows astronomers to write, for example, the distance between the Earth and the nearest stars beyond the Sun as 4 light-years, instead of 38,000,000,000,000,000 meters. The light-year is just one of a number of specialized units which have been defined by scientists in order to make measurements and calculations involving very large (and very small) distances more convenient.

---

Ah; me! I find that it works if I use Firefox. Doesn't work on explorer for me!

[Robin Kaminski]

This is the first picture I've been able to see how the spiral looks in 3D. Does anyone else see this?

[neufer]

The January 25, 1997 APOD says M51 is 15 million light years distant. Here is the link : http://apod.nasa.gov/apod/ap970125.html
Today's APOD says twice as far at 30 million light years. Has space expanded this much in 16 years?

• For one, Type II supernova SN 2005cs happened in those intervening 16 years:

[b][color=#0000FF]Hubble Telescope: M51 before & after SN 2005cs[/color][/b]

---

Sky and Telescope: Supernova in M51
by Alan M. MacRobert, August 24, 2005

<<A 14th-magnitude supernova has appeared in a spiral arm of the Whirlpool Galaxy, M51 in Canes Venatici, high overhead these evenings. Although the supernova is probably too faint for most visual observers, it's well within reach of astro-imagers.

Supernova 2005cs was discovered on June 28th by amateur supernova hunter Wolfgang Kloehr of Schweinfurt, Germany, in a CCD image that he took with an 8-inch reflector. A spectrum obtained on June 30th by Robert Hutchins with the Whipple Observatory 1.5-meter telescope in Arizona showed it to be a Type II supernova: the hydrogen-rich explosion of a giant star whose massive core collapsed to become a neutron star or black hole. Prediscovery images show the supernova at 16th magnitude just a few days before it was spotted. It remained at about magnitude 14.1 as of July 8th. [Update August 24th: The supernova has still hardly changed; it's at about magnitude 14.3.] It's located 78 arcseconds south of the galaxy's nucleus.>>

<<With the recent SN 2005cs derived estimate of 23 ± 4 Mly distance, and an angular diameter of roughly 11.2′, it can be inferred that M51's bright circular disk has a radius of about 43,000 light-years. Its mass is estimated to be 160 billion solar masses.>>

[stephen63]

I didn't think Type II SN were of use for measuring distances, but I was wrong!
http://www.universetoday.com/73365/type ... rd-candle/

[BillBixby]

Ann, don’t try saying or naming the numbers. Just stay with the numbers themselves, as the numbers don’t get confusing while the names do. Convention beyond nine-hundred-ninety-nine million has not been reached by all countries. In the United States, and a lot of countries, one thousand million makes a billion, and one thousand billion makes a trillion. In a lot of other countries it takes a million-million to make a billion, and a billion-billion to make a trillion. Both logics make sense, neither logic has been agreed upon. Our system in the US makes 1,000,000,000 one billion. Elsewhere; 1,000,000,000 is one thousand million.

As a side note, imagine you were in a country that did not use the convention used in the USA. You read about the United States trillion dollar budgets and the size of our deficits and you would be horrified. I am horrified at those numbers, much less the words, just using our US naming system.

Bill

[jchris]

the wikipedia page on canes venact. says the galaxy is 37 million years distant

[ta152h0]

I like driving cars to the moon and back. My 63 Plymout did that. My 73 Charger didn't quite get there ( I got tired of changing the electronic sparky maker. Getting closer with my 2004 Powerstroke.
M51 was the reason NASA went off script and created a great mission to fix the Hubble, only possible with humans. That was a fine human endeavor.

[MargaritaMc]

Chris wrote From Kim Stanley Robinson's book 2312, set in a heavily colonized Solar System, a passage about the plan to send one of the moons of Pluto out on a 1000 year journey to the stars:

"So. Our little pearl of warmth, our spinning orrery of lives, our island, our beloved solar system, our hearth and home, tight and burnished in the warmth of the sun - and then - these starships we are making out of Nix. We will send them to the stars, they will be like dandelion seeds, floating away on a breeze. Very beautiful. We will never see them again."

That was a fantastic quote from Robinson, Chris - I've gone straight to Amazon to get a copy of the book on my Kindle.

Do we have a Book Thread anywhere?

Margarita

[Boomer12k]

WOW!!! Always a crowd pleaser. I can't wait for better, warmer weather, and get out my scope and take some images, and use the post imaging techniques I learned at the end of last Summer. They ought to be pretty good.

Just AWESOME the details in this photo. The dust swirls, the star formation, the strands and strings of stars. Like a serpent coiling on itself.

:---[===] *

[Boomer12k]

I appreciate being told these numbers. I have sometimes tried converting light-years to kilometers, and I have always failed. So it's 38 trillion kilometers, then. How do you say the other number - nine point five trillion kilometers? I tried to say it in Swedish, where a "trillion" is of course a "biljon", but in any case it sounded wrong. I found myself reading 9,5000,000,000,000,000 as "ninety-five trillion" and then getting confused at the obvious thirty-eight trillion (38,000,000,000,000,000) which seemed to small to be four times 9,5000,000,000,000,000. Maths and I are not good friends!

The distance is certainly impossible to imagine, in any case. When I made a model of the inner solar system, I found that I couldn't even really imagine the distance between the Earth and the Sun. I tried to picture myself sitting in a fantastically heat- and radiation-proof spaceship traveling to the Sun, and I tried to imagine the actual distance the spaceship would have to travel to reach the Sun. I couldn't find a way to make this distance understandable in terms that I am the least familiar with.

Ann

Ann, what is so hard to understand about 93 million miles? But then I have trouble with A.U. and Parsecs. If I drove my Z to the Moon and back, I would be just barely on my way back, in terms of MILEAGE on my Z. 268,800 miles. Not bad for a 40 year old car.

AND, the word you are looking for is, QUADRILLION....95 quadrillion. At least in American Counting.

9,5000,000,000,000,000....plus the original quote is in error. It has a 5000 where only 3 decimals should be....it should be written:
95,000,000,000,000,000

That would be.....95,.....000......000.....000.....000.......000
quads, trills, bills, mills, thous, hundreds.

Same with the 38....38 Quadrillion. Much easier than 38 thousand million million.

Quadrillion may mean either of the two numbers, 1,000,000,000,000,000 (one thousand million million)...in the American System, this is 1 quadrillion. And other version of this number is what we would call a SEPTILLION. The SEVENTH place. 1,000,000,000,000,000,000,000,000 but it can be called a Quadrillion in other countries....

Here is a good article to explain large numbers.
http://en.wikipedia.org/wiki/Names_of_large_numbers

:---[===] *

[stephen63]

Here is a fun link. The universe in a nutshell.
http://htwins.net/scale2/

[Anthony Barreiro]

... . Maths and I are not good friends!

The distance is certainly impossible to imagine, in any case. When I made a model of the inner solar system, I found that I couldn't even really imagine the distance between the Earth and the Sun. I tried to picture myself sitting in a fantastically heat- and radiation-proof spaceship traveling to the Sun, and I tried to imagine the actual distance the spaceship would have to travel to reach the Sun. I couldn't find a way to make this distance understandable in terms that I am the least familiar with.

Ann

I find it easier and more intelligible to do it the other way around, to use the speed of light as my constant basis of comparison. The Moon is one and half light seconds away. The Sun is eight light minutes away. Jupiter, 40 light minutes, plus or minus 8 light minutes depending on where Earth is in our orbit relative to Jupiter. Neptune, four light hours away. (Whistling distractedly through the Kuiper Belt and Oort Cloud ... .) Alpha Centauri, four light years ... .

[ta152h0]

I got a 33 foot long roll of vellum and placed the sun in one end and Pluto ( still a planet in my book ) on the other end , and filled in the planets according to scale. Then I took it to my wife's class and rolled the thing out. The kids were amazed and so was I Prox Centauri would be a really long walk away. Whirlpool galaxy.......I need an ice cold one.