APOD: The Rosette Nebula (2012 Feb 14)

[APOD Robot]

The Rosette Nebula

Explanation: The Rosette Nebula is not the only cosmic cloud of gas and dust to evoke the imagery of flowers -- but it is the most famous. At the edge of a large molecular cloud in Monoceros, some 5,000 light years away, the petals of this rose are actually a stellar nursery whose lovely, symmetric shape is sculpted by the winds and radiation from its central cluster of hot young stars. The stars in the energetic cluster, cataloged as NGC 2244, are only a few million years old, while the central cavity in the Rosette Nebula, cataloged as NGC 2237, is about 50 light-years in diameter. The nebula can be seen firsthand with a small telescope toward the constellation of the Unicorn (Monoceros).

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[Sandstone]

A cosmic rose for Valentine's Day... how appropriate!

[Beyond]

And with sparkles too!

[Flase]

A cosmic rose for Valentine's Day... how appropriate!

Horrible. Do they celebrate Christmas or Ramadan, or just the worship of money?

[owlice]

Ah, Flase, you haven't been looking at APOD for very long, have you?!

As Sandstone said, a very appropriate APOD! More roses and other celestial valentines can be seen in today's Retrospective thread.

[Soonie Koo]

I dunno...I do not see roses. If this pic is rotated 90 deg to the right, I see a scary alien with a double face!

[Flase]

I'm the Valentine Scrooge. If people loved each other they would show it all year and not have to be forced by endless advertising razzmatazz to buy overpriced roses once a year. Such a love will wilt and die like the flowers.

[owlice]

I'm sure you're the expert. Nonetheless, you need to divert from your recent trend in posting.

[Boomer12k]

Just how I like 'em....young and hot....

Yeah, I know....my bad...


:---[===] *

[BillLee]

Warning: Newbie alert!

I am NOT an astonomer or anything! But I enjoy the fantastic images in the APOD. I have gathered a large number of them and use them for my screen background.

Question: How do you distinguish stars referenced in an image like the one today (Rosette Nebula) from foreground stars?

I.e.: the description says "...winds and radiation from its central cluster of hot young stars...". How can I tell which of the many stars in the central area of the image are those referenced and not some star in the foreground?

Thanks.

Regards,

Bill Lee

[temoore]

Is the APOD site also posting thumbnails? It seems I'm getting the same one every day since about 10 Feb. It could be the program I'm using (Pic-A-POD), I suppose...

[owlice]

There is a problem with the thumbnails; it will be fixed, but please be patient. Thanks!

[Ann]

Warning: Newbie alert!

I am NOT an astonomer or anything! But I enjoy the fantastic images in the APOD. I have gathered a large number of them and use them for my screen background.

Question: How do you distinguish stars referenced in an image like the one today (Rosette Nebula) from foreground stars?

I.e.: the description says "...winds and radiation from its central cluster of hot young stars...". How can I tell which of the many stars in the central area of the image are those referenced and not some star in the foreground?

Thanks.

Regards,

Bill Lee

I would be able to give you a better answer if I had access to my software as I'm writing this.

In the case of the Rosette Nebula, you can see that the nebula is quite symmetric and round. You can also see that there is what looks like a "hole" or a cavity in the middle. You can also see that there are some bright stars in or very near this cavity.

Young stars are born from a cloud of gas and dust. When they are born, they will illuminate what remains of their birth cloud with their own light. If the stars are hot enough, they will ionize the gas of the remaining cloud. That is, they will emit a lot of ultraviolet photons which will disturb the electrons of the atomic hydrogen in the gas, imparting energy to them. The electrons will then radiate this extra energy away as red light.

You can see that the Rosette Nebula is very red, because of all the ultraviolet light that is emitted by a few hot bright stars. The ultraviolet light is imparting extra energy to very many electrons, which re-radiate this energy as red light. You can see that a few bright stars appear to be more or less at the center of this red nebula. It is a good guess that the bright stars in the middle caused the gas to glow red.

Closer to the hot bright stars, the "wind" they emit will be so strong that they blow away any gas in their vicinity. You can see that there is what appears to be a "hole" in the middle of the nebula, and you can see that many of the bright stars appear to sit inside this "cavity". It is a good guess that many of these stars are responsible for blowing the central "hole" in the nebula.

However, not all of the bright stars "in the middle" are actually part of the cluster that ionizes the nebula and makes it glow red. The apparently brightest star, a yellowish star at four o'clock, is a foreground star. How can you know that just by looking at the picture?

You can't. You have to measure the parallax of the star and compare it with the parallax of the other bright stars in the middle of the nebula. Measuring the parallax of a star means that you use triangulation to see how far away it is. Basically, a more nearby star will be seen to move relative to the stars that are farther away, as the Earth follows its orbit around the Sun. However, this effect is never visible to the naked eye.

You can also carefully measure how the stars appear to move across the sky over the course of several years. The stars that belong to a cluster will all move in more or less the same direction at more or less the same speed. A star that does not belong to the cluster will move in a different direction and at a different speed. Again you need astronomical instruments to measure this effect.

You can also examine the spectra of the stars. The spectrum of a star will always be strongly affected by the temperature of the star. However, you can usually also tell from the spectrum of a star if the star is small, big or very big.

Let's consider the bright yellowish star again. Its parallax is not the same as the parallax of the bright blue stars in the middle of the nebula. The yellow star is seen to move more than the blue stars in response to the Earth's motion around the Sun. Therefore the yellow star is closer to us than the blue stars. Also the yellow star isn't moving in the same direction or at the same speed as the blue stars. Also, the spectrum of the yellow star says that although this star is big, it is not as big as it would have to be if it was at the same distance from us as the blue stars.

Therefore, the yellow star is a foreground star.

Ann

[orin stepanek]

Today's APOD shows a very beautiful Rosette for Valentines day! Very nice.

[Chris Peterson]

Question: How do you distinguish stars referenced in an image like the one today (Rosette Nebula) from foreground stars?

Mostly, you can't just by looking at an image like this. In an image of another galaxy, virtually every star in the image is a foreground object. But when looking at nearby objects like this nebula, there may be more background stars than foreground ones, and without additional information from other instruments, there is usually no way to tell for sure which are which.

However, when you have an emission nebula like this, something energetic needs to be driving it, and that is often a small cluster of hot, bright stars. The fact that you can see just that in this image- at the center of the nebula (blue tells us they are hot, the diffraction spikes mark them as relatively bright and probably close), with a zone around them free of dust and gas- should provide a strong hint that these stars are inside the nebula. And indeed, they are. Other bright stars (those with diffraction spikes) are probably foreground stars, but not necessarily. The majority of dimmer stars are probably in the background, but again, not necessarily.

[jinger]

looking at this image, with its young blue stars nestled amid plumes of cosmic ether, I am reminded of a tibetan mantra: hail to the jewel in the lotus

[neufer]

Click to play embedded YouTube video.

[b][color=#0000FF]18th century painting of the China Rose (月季)[/color][/b]

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<<It is believed that roses were grown in all the early civilisations of temperate latitudes from at least 5000 years ago. They are known to have been grown in ancient Babylon. Paintings of roses have been discovered in Egyptian pyramid tombs from the 14th century BC. Records exist of them being grown in Chinese gardens and Greek gardens from at least 500 BC. Most of the plants grown in these early gardens are likely to have been either species collected from the wild, or selections from them.

The significant breeding of modern times started slowly in Europe, from about the seventeenth century. This was encouraged by the introduction of new species, and especially by the introduction of the China rose in the nineteenth century. An enormous range of roses has been bred since then. A major contributor in the early 19th century was Empress Josephine of France who patronized the development of rose breeding at her gardens at Malmaison. As long ago as 1840 a collection numbering over one thousand different cultivars, varieties and species was possible when a rosarium was planted by Loddiges nursery for Abney Park Cemetery, an early Victorian garden cemetery and arboretum in England.

Rose perfumes are made from attar of roses or rose oil, which is a mixture of volatile essential oils obtained by steam distilling the crushed petals of roses. An associated product is rose water which is used for cooking, cosmetics, medicine and in religious practices. The production technique originated in Persia then spread through Arabia and India, and more recently into eastern Europe. In Bulgaria, Iran and Germany, damask roses (Rosa damascena 'Trigintipetala') are used. In other parts of the world Rosa centifolia is commonly used. The oil is transparent pale yellow or yellow-grey in colour. 'Rose Absolute' is solvent-extracted with hexane and produces a darker oil, dark yellow to orange in colour. The weight of oil extracted is about one three-thousandth to one six-thousandth of the weight of the flowers; for example, about two thousand flowers are required to produce one gram of oil.

The main constituents of attar of roses are the fragrant alcohols geraniol and l-citronellol; and rose camphor, an odourless paraffin. β-Damascenone is also a significant contributor to the scent. Rose water, made as a byproduct of rose oil production, is widely used in Asian and Middle Eastern cuisine. In France there is much use of rose syrup, most commonly made from an extract of rose petals. In the United States, this French rose syrup is used to make rose scones and marshmallows.>>

[Beyond]

Marshmallows I don't remember any marshmallows ever tasting or smelling anything like roses.

[neufer]

Marshmallows I don't remember any marshmallows ever tasting or smelling anything like roses.

<<The marshmallow probably first came into being as a medicinal substance, since the mucilaginous extracts comes from the root of the marshmallow plant, Althaea officinalis, which were used as a remedy for sore throats.

Concoctions of other parts of the marshmallow plant had medical uses as well. The root has been used since Egyptian antiquity in a honey-sweetened confection useful in the treatment of sore throat. The later French version of the recipe, called pâte de guimauve, included an egg white meringue and was often flavored with rose water. Pâte de guimauve more closely resembles contemporary commercially available marshmallows, which no longer contain any marshmallow plant.

The use of marshmallow to make a candy dates back to ancient Egypt, where the recipe called for extracting sap from the plant and mixing it with nuts and honey. Another pre-modern recipe uses the pith of the marshmallow plant, rather than the sap. The stem was peeled back to reveal the soft and spongy pith, which was boiled in sugar syrup and dried to produce a soft, chewy confection. Candymakers in early 19th century France made the innovation of whipping up the marshmallow sap and sweetening it, to make a confection similar to modern marshmallow. The confection was made locally, however, by the owners of small candy stores. They would extract the sap from the mallow plant's root, and whip it themselves. The candy was very popular, but its manufacture was labor-intensive. In the late 19th century, French manufacturers devised a way to get around this by using egg whites or gelatin, combined with modified corn starch, to create the chewy base. This avoided the laborious extraction process, but it did require industrial methods to combine the gelatin and corn starch in the right way. Also related are the German confectionery called Schaumkuss.

Another milestone in the development of the modern marshmallow was the extrusion process by the American Alex Doumak in 1948. This invention allowed marshmallows to be manufactured in a fully automated way. The method produced the cylindrical shape that are now associated with marshmallows. The process involves running the ingredients through tubes and then extruding the finished product as a soft cylinder, which is then cut into sections and rolled in a mixture of finely powdered cornstarch and confectioner's sugar. Doumak founded the Doumak company in 1961 on the strength of his patent on this process.

Marshmallows, like most candies, are sweetened with sucrose. They are currently prepared by aeration of mixtures of sucrose and proteins to a final density of about 0.5 g/mL. The viscosity of the mixture, owing to the proteins, gelatin or egg albumin, prevents collapse of the air-filled cells. Marshmallows are popular in Asia, particularly in the previous colonies of the UK. One of the largest suppliers in Asia is Erko Foods, based in China. The company exports to 56 countries. Erko is also the market leader in the Middle East, where their Halal marshmallow is sold.>>

[Ann]

Question: How do you distinguish stars referenced in an image like the one today (Rosette Nebula) from foreground stars?

Mostly, you can't just by looking at an image like this. In an image of another galaxy, virtually every star in the image is a foreground object. But when looking at nearby objects like this nebula, there may be more background stars than foreground ones, and without additional information from other instruments, there is usually no way to tell for sure which are which.

However, when you have an emission nebula like this, something energetic needs to be driving it, and that is often a small cluster of hot, bright stars. The fact that you can see just that in this image- at the center of the nebula (blue tells us they are hot, the diffraction spikes mark them as relatively bright and probably close), with a zone around them free of dust and gas- should provide a strong hint that these stars are inside the nebula. And indeed, they are. Other bright stars (those with diffraction spikes) are probably foreground stars, but not necessarily. The majority of dimmer stars are probably in the background, but again, not necessarily.

Let's take a closer look at some of the stars. The blue stars in the middle of the nebula have typical parallaxes of about 0.5 milliarcseconds, which is very little and marks them as far away. Their proper motion is around -2 milliarseconds per year in right ascension and -1 milliarcsecond per year in declination. The bright yellow star close to them, however, has a parallax of about 6 milliarcseconds per year. It whooshes by fast in right ascension, about -37 milliarcseconds per year.

Let's look at some other stars! The bright white star with diffraction spikes at about two o'clock is a foreground star of spectral class K0. The blue star near the upper right corner, however, is a distant star, possibly as far away as the stars of the stars at the center of the Rosette Nebula. It appears to be intrinsically somewhat cooler and fainter than the stars of the Rosette, so it could be a little nearer. Its proper motion is a little faster than the proper motion of the Rosettes, but not very much so.

At lower right you can see two blue stars with diffraction spikes. Both have tiny parallaxes and proper motions that mark them as almost certain members of the Rosette Nebula cluster.

At six o'clock you have a blue star that might be a member of the Rosette Nebula cluster, but its parallax and proper motion have not been well measured. To the upper left of that blue star is a strikingly orange star, which, like the blue one, may or may not be a member of the Rosette Nebula cluster. Continue in the same direction until you come to another yellow-orange star. This one is probably a foreground object. From that yellow star, go to the lower left to a bright whitish star. This one is most definitely a foreground object! Its parallax is about 29 milliarcseconds, and its proper motion is about 112 milliarcseconds per year in right ascension and 97 milliarsceconds in declination. It is a star of spectral class K1IV, about 114 light-years away and 70% as bright as the Sun!

Finally, in the lower left corner there is another white star with diffraction spikes. That one, too, is a foreground star, though almost certainly farther away than the K1IV star and probably a few times brighter than the Sun.

Ann

[Chris Peterson]

The blue stars in the middle of the nebula have typical parallaxes of about 0.5 milliarcseconds, which is very little and marks them as far away.

I'd argue that any star with a detectable parallax is, in fact, very near! <g> Such an elegant method... it's a shame we can only use it for the tiniest fraction of objects we are able to observe.

[neufer]

The blue stars in the middle of the nebula have typical parallaxes of about 0.5 milliarcseconds, which is very little and marks them as far away.

I'd argue that any star with a detectable parallax is, in fact, very near!
Such an elegant method... it's a shame we can only use it for the tiniest fraction of objects we are able to observe.

Such an elegant method... with improved technology there is almost no limit in the number of galactic objects we will be able to observe in the future:

<<Hipparcos (an acronym for "High precision parallax collecting satellite") was a scientific mission of the European Space Agency (ESA), launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky. This permits the accurate determination of proper motions and parallaxes of stars, allowing a determination of their distance and tangential velocity. When combined with radial velocity measurements from spectroscopy, this fixes all six quantities needed to determine the motion of the star. The Hipparcos Catalogue, a high-precision catalogue of more than 100,000 stars, was published in 1997. Observationally, the objective was to provide the positions, parallaxes, and annual proper motions for some 100,000 stars with an unprecedented accuracy of 2 milliarcseconds, a target in practice eventually surpassed by a factor of two. >>

The Astrophysical Journal, 571:906-917, 2002 June 1
© 2002. The American Astronomical Society. All rights reserved. Printed in U.S.A.
Very Long Baseline Array Measurement of Nine Pulsar Parallaxes
Walter F. Brisken , John M. Benson , and W. M. Goss and S. E. Thorsett

ABSTRACT: <<We determined the distances to nine pulsars by parallax measurements using the NRAO Very Long Baseline Array, doubling the number of pulsars with accurate distance measurements. Broadband phase modeling was used to calibrate the varying dispersive effects of the ionosphere and remove the resulting phase errors from the phase-referenced VLBI data. The resulting parallaxes have a typical accuracy of [0.1 milliarcseconds] or better, yielding distance measurements as accurate as 2%. We also report new proper motion measurements of these pulsars, accurate to [0.4 milliarcseconds] yr-1 or better.>>

http://www.astro.cornell.edu/~shami/psr ... allax.html

<<Gaia (or Global Astrometric Interferometer for Astrophysics) is a European Space Agency (ESA) space mission in astrometry and a successor to ESA's Hipparcos mission. It is part of the ESA Horizon 2000 Plus long-term scientific program and expected to launch in March 2013. Gaia will compile a catalogue of approximately 1 billion stars in our galaxy to magnitude 20. Its objectives comprise:

• astrometric (or positional) measurements, determining the positions, distances, and annual proper motions of stars with an accuracy of about 0.02 milliarcseconds at 15 mag, and 0.2 milliarcseconds at 20 mag
  
  spectrophotometric measurements, providing multi-epoch observations of each detected object
  
  radial velocity measurements.

Gaia will create an extremely precise three-dimensional map of stars throughout our Milky Way galaxy and beyond, and map their motions which encode the origin and subsequent evolution of the Milky Way. The spectrophotometric measurements will provide the detailed physical properties of each star observed, characterising their luminosity, effective temperature, gravity and elemental composition. This massive stellar census will provide the basic observational data to tackle a wide range of important problems related to the origin, structure, and evolutionary history of our Galaxy. Large numbers of quasars, galaxies, extrasolar planets and solar system bodies will be measured at the same time.

Gaia will also be capable of discovering asteroids with orbits that lie between Earth and the Sun, a region that is difficult for Earth-based telescopes to monitor since this region is only in the sky during or near the daytime.

Gaia will be launched on a Soyuz-FG rocket in August 2013 and will fly to the Lagrange point L2 located approximately 1.5 million kilometers from Earth. The L2 point will provide the spacecraft with a very stable thermal environment. There it will describe a Lissajous orbit which will avoid eclipses of the Sun by the Earth, which would otherwise limit the amount of solar energy the satellite can retrieve through its solar panels and also disturb the thermal equilibrium.

Similarly to its predecessor Hipparcos, Gaia consists of two telescopes providing two observing directions with a fixed, wide angle between them. The spacecraft rotates continuously around an axis perpendicular to the two telescopes' lines of sight (LOS). The spin axis in turn has a slight precession across the sky, while maintaining the same angle to the Sun. By precisely measuring the relative positions of objects from both observing directions, a rigid system of reference is obtained.

Despite its name, Gaia does not actually use interferometry to determine the positions of stars. At the time of the original design, interferometry seemed the best way to achieve the target resolution, but the design later evolved into an imaging telescope.

Each celestial object will be observed on average about 70 times during the mission, which is expected to last 5 years. These measurements will help determine the astrometric parameters of stars: 2 corresponding to the angular position of a given star on the sky, 2 for the derivatives of the star's position over time (motion) and lastly, the star's parallax. The radial velocity of the star is measured using the Doppler Effect by a spectrometer, which is integrated into the Gaia telescope system.>>

<<Spektr-R[2] (or Radioastron) is a Russian orbital radio telescope, and currently the largest space telescope in orbit.. It is funded by the Russian Astro Space Center, and was launched into Earth orbit on 18 July 2011,.\ with a perigee of 10,000 kilometers (6,200 mi) and an apogee of 390,000 kilometers (240,000 mi), about 700 times the orbital height of the Hubble Space Telescope.. The main scientific goal of the mission is the study of astronomical objects with an angular resolution up to a few millionths of an arcsecond. This is accomplished by using the satellite in conjunction with ground-based observatories and interferometry techniques.>>

[Ann]

A rose marshmallow, a work of Art.












Ann

[Chris Peterson]

Such an elegant method... with improved technology there is almost no limit in the number of galactic objects we will be able to observe in the future

Right. As I said, just the tiniest fraction of objects we are able to observe.

[Anthony Barreiro]

Thank you Ann for the enlightening explanation of parallax and proper motion, as well as spectra and brightnesses. I sorta knew this stuff, but to have it presented in relation to a beautiful image of the nebula surrounding a cluster I've seen through my little telescope in the backyard really brings it home. I very much appreciate how kindly and patiently you share your knowledge with those of us who are here mostly for the pretty pictures.