APOD: Vista with NGC 2170 (2010 Oct 15)

[APOD Robot]

Vista with NGC 2170

Explanation: Drifting through the one-horned constellation Monoceros, these dusty streamers and new born stars are part of the active Monoceros R2 star-forming region, embedded in a giant molecular cloud. The cosmic scene was recorded by the VISTA survey telescope in near-infrared light. Visible light images show dusty NGC 2170, seen here just right of center, as a complex of bluish reflection nebulae. But this penetrating near-infrared view reveals telltale signs of ongoing star formation and massive young stars otherwise hidden by the dust. Energetic winds and radiation from the hot young stars reshape the natal interstellar clouds. Close on the sky to the star-forming Orion Nebula, the Monoceros R2 region is almost twice as far away, about 2700 light-years distant. At that distance, this vista spans about 80 light-years.

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[bystander]

http://asterisk.apod.com/vie ... 29&t=21417

Spectacular image wows UK scientists
VISTA Reveals the Secret of the Unicorn

[Ann]

Indeed, this is a good-looking infrared image.

Otto, the Apod Robot, wrote:

...this penetrating near-infrared view reveals telltale signs of ongoing star formation and massive young stars...

How massive is massive?

Personally I'm very interested in massive star formation, since it gives birth to my favorite stars, the B-type, or, better yet, the O-type stars.

What about the star formation here? How massive are the stars that have just been born here? Are they five times as massive as the Sun? Ten times as massive? Twenty times as massive? Surely they aren't forty times as massive as the Sun, like Theta 1C Orionis, which energizes the Orion Nebula?

Ann

[orin stepanek]

It's interesting how much is hidden with visible light compared with near infrared light.

[neufer]

...this penetrating near-infrared view reveals telltale signs of ongoing star formation and massive young stars...

How massive is massive?

Personally I'm very interested in massive star formation, since it gives birth to my favorite stars, the B-type, or, better yet, the O-type stars.

What about the star formation here? How massive are the stars that have just been born here? Are they five times as massive as the Sun? Ten times as massive? Twenty times as massive? Surely they aren't forty times as massive as the Sun, like Theta 1C Orionis, which energizes the Orion Nebula?

They could be that massive; there just can't be very many of them (and they won't live long).

Wan OB star for each knot of gas will quickly dissipate the dust leaving behind a typical stellar population of long lived dwarfs.

<<Once a giant molecular cloud begins to collapse, star formation proceeds via successive fragmentations of the cloud into smaller and smaller clumps, resulting eventually in the formation of up to several thousand stars. In our own galaxy, the formation rate of open clusters is estimated to be one every few thousand years. Once star formation has begun, the hottest and most massive stars (known as OB stars) will emit copious amounts of ultraviolet radiation. This radiation rapidly ionizes the surrounding gas of the giant molecular cloud, forming an H II region. Stellar winds from the massive stars and radiation pressure begin to drive away the gases; after a few million years the cluster will experience its first supernovae, which will also expel gas from the system. After a few tens of millions of years, the cluster will be stripped of gas and no further star formation will take place. Typically, less than 10% of the gas originally in the cluster will form into stars before it is dissipated.>>

[Ann]

Wan OB star for each knot of gas will quickly dissipate the dust leaving behind a typical stellar population of long lived dwarfs.

Wan OB star k(e)no(bi)[t] down, many hobbits to go?

http://photos.go-ghoti.com/BKGRND/Obi%2 ... Kenobi.bmp

Ann

[neufer]

Three-ton infrared camera in front of the VISTA telescope.

---

<<The VISTA (Visible and Infrared Survey Telescope for Astronomy) is a 4-metre class wide-field telescope at the Paranal Observatory in Chile. The objective to repeatedly image large areas of sky at seeing-limited resolution led to its unique optical design. The primary mirror is a concave hyperboloid with 4.1 m diameter and about f/1 focal ratio. The mirror has a meniscus shape of 17 cm thickness with a central 1.2 m hole to accommodate the camera at the Cassegrain focus. It is the largest mirror of this shape and of such short focal ratio; polishing it took 2 years, which was longer than anticipated.The mirror is supported by a number of actuators (81 on the back and 24 around the edge), which allow its shape to be controlled by computer.

The secondary mirror is a convex hyperboloid of 1.24 m diameter. The combination of the two hyperbolic mirrors makes this a quasi-Ritchey-Chrétien design. The combined focal ratio is about f/3, but the image quality of the two mirrors alone would be poor. The secondary mirror is mounted on a hexapod support so that its position, tip, and tilt are also computer-controlled.

The infrared camera is the world's largest at 2.9 tonnes. For an infrared camera, it is vital to block heat radiation from the telescope and dome. This is accomplished by a sequence of cooled baffles in front of the field corrector lenses. Also, the secondary mirror is undersized to avoid edge detectors viewing warm structure outside the edge of the primary; this means the aperture seen by any point in the image plane is 3.7 m. This design requires the camera's vacuum cryostat – which cools the detectors as well as the baffles – to be more than 2 m long. A filter wheel just in front of the detectors allows the selection of a particular infrared wavelength range. The image plane of the camera also has wave front detectors used to control the shape of the primary mirror and the position and tip/tilt of the secondary mirror (active optics). This compensates for flexure and ensures a focussed image at all altitudes.>>

http://asterisk.apod.com/viewtopic.php? ... 57#p129457
http://asterisk.apod.com/viewtopic.php? ... 03#p119903
http://asterisk.apod.com/viewtopic.php? ... 55#p115755

<<In telescopes, the coma (aka comatic aberration) in an optical system refers to aberration which results in off-axis point sources such as stars appearing distorted. Coma is an inherent property of telescopes using parabolic mirrors. Light from a point source (such as a star) in the center of the field is perfectly focused at the focal point of the mirror. However, when the light source is off-center (off-axis), the different parts of the mirror do not reflect the light to the same point. This results in a point of light that is not in the center of the field looking wedge-shaped. The further off-axis, the worse this effect is. This causes stars to appear to have a cometary coma, hence the name. Schemes to reduce spherical aberration without introducing coma include Schmidt, Maksutov and Ritchey-Chrétien optical systems.>>

<<The Ritchey–Chrétien telescope or RCT is a specialized Cassegrain telescope designed to eliminate coma, thus providing a large field of view compared to a more conventional configuration. An RCT has a hyperbolic primary and a hyperbolic secondary mirror. It was invented in the early 1910s by American astronomer George Willis Ritchey (1864–1945) and French astronomer Henri Chrétien (1879–1956). Ritchey constructed the first successful RCT in 1927 (e.g. Ritchey 24-inch reflector). The second RCT was a 40 in instrument constructed by Ritchey for the United States Naval Observatory; that telescope is still in operation at the Naval Observatory Flagstaff Station.

The Ritchey–Chrétien design is free of third-order coma and spherical aberration, although it does suffer from fifth-order coma, severe large-angle astigmatism, and comparatively severe field curvature. When focused midway between the sagittal and tangential focusing planes, stars are imaged as circles, making the RCT well suited for wide field and photographic observations. As with the other Cassegrain-configuration reflectors, the RCT has a very short optical tube assembly and compact design for a given focal length. The RCT offers good off-axis optical performance, but examples are relatively rare due to the high cost of hyperbolic primary mirror fabrication; Ritchey–Chrétien configurations are most commonly found on high-performance professional telescopes.>>

[emc]

http://www.eso.org/public/teles-instr/vlt.html "Did you know? The skies over the ESO sites in Chile are so dark that on a clear moonless night it is possible to see your shadow cast by the light of the Milky Way alone."

Reckon that makes for quite an old shadow.

[mexhunter]

Hi Art:
Thank you very much for sharing that photo of the infrared camera.
I had never seen one.
Many greetings
César

[astralos]

Having received a certain inspiration from the excellent depiction of nebula NGC 2170 in today's (15 Oct.) APOD, I suggest dubbing the formation the "Fireworks Nebula" - a fun, catchy name (so thinks I, anyway)!

[mpharo]

Vista with NGC 2170

October 15, 2010

I like the picture of the star R2 forming within it's home nebulae. The picture sort of resembles a comet cruising downward through space.


Michael Pharo

[biddie67]

...... For an infrared camera, it is vital to block heat radiation from the telescope and dome. This is accomplished by a sequence of cooled baffles in front of the field corrector lenses. Also, the secondary mirror is undersized to avoid edge detectors viewing warm structure outside the edge of the primary; this means the aperture seen by any point in the image plane is 3.7 m. This design requires the camera's vacuum cryostat – which cools the detectors as well as the baffles – to be more than 2 m long.......

I have been wondering why it was of such critical concern about the life-expectancy of the coolant in the infrared camera satellites where they are out in orbit in the cold - at least I thought it was pretty cold already.

This article made me realize that the infrared sensors are so sensitive that any minute source of heat in the camera itself would distort the images ...

[Chris Peterson]

I have been wondering why it was of such critical concern about the life-expectancy of the coolant in the infrared camera satellites where they are out in orbit in the cold - at least I thought it was pretty cold already.

It isn't cold in orbit. A big design problem with satellites (and with spacesuits) is getting rid of heat. And if you are in sunlight at all (which is difficult to avoid), that is even more heat you need to get rid of.

This article made me realize that the infrared sensors are so sensitive that any minute source of heat in the camera itself would distort the images ...

It isn't a question of distortion, but of the fact that you can't have your sensor radiating photons of the same wavelength you are trying to measure. Imagine what ordinary camera images would look like if the CCD was glowing in visible light. The sensor would expose itself, before you ever opened the shutter.

[biddie67]

..... It isn't cold in orbit. A big design problem with satellites (and with spacesuits) is getting rid of heat. And if you are in sunlight at all (which is difficult to avoid), that is even more heat you need to get rid of.

Chris - I can understand how heat could slowly collect when in sunlight, but I don't understand what is generating the heat when there is no sunlight present like when behind the moon or earth from the sun.

I didn't know that spacesuits had to provide for ridding of extra heat in addition to their other functions.

[neufer]

I can understand how heat could slowly collect when in sunlight, but I don't understand what is generating the heat when there is no sunlight present like when behind the moon or earth from the sun.

Next to the Sun, the Earth & Moon are the main sources of contaminating heat radiation;
one should get as far away from Earth & Moon as possible and then shield from their radiation.

<<The James Webb Space Telescope's primary scientific mission has four main components:

• * to search for light from the first stars and galaxies which formed in the Universe after the Big Bang,
  * to study the formation and evolution of galaxies,
  * to understand the formation of stars and planetary systems, and
  * to study planetary systems and the origins of life.

Due to a combination of redshift, dust obscuration, and the intrinsically low temperatures of many of the sources to be studied, the JWST must operate at infrared wavelengths, spanning the wavelength range from 0.6 to 28 micrometres. In order to ensure that the observations are not hampered by infrared emission from the telescope and instruments themselves, the entire observatory must be cold. JWST must be well-shielded from the Sun so that it can radiatively cool to roughly 40 K. To this end, JWST will incorporate a large metalized fan-fold sunshield, which will unfurl to block infrared radiation from the Sun, Earth and Moon. The telescope's location at the Sun-Earth L2 Lagrange point ensures that the Earth and Sun occupy roughly the same relative position in the telescope's view, and thus make the operation of this shield possible.>>

<<Wide-field Infrared Survey Explorer (WISE) is a NASA-funded infrared-wavelength astronomical space telescope launched on 14 December 2009. The 320 million USD mission launched an Earth-orbiting satellite with a 40 cm diameter infrared telescope, which performed an all-sky astronomical survey with images in the 3 to 25 μm wavelength range, over 10 months. The initial mission length is limited by its hydrogen coolant. In October 2010 WISE hydrogen coolant and original NASA funding ran out. The proposed WISE warm mission, using remaining functionality, was not approved by NASA.

<<The Spitzer Space Telescope (SST) is an infrared space observatory launched in 2003. It follows a rather unusual heliocentric orbit trailing and drifting away from Earth's orbit at approximately 0.1 astronomical unit per year. The primary mirror is 85 centimetres in diameter, f/12 and made of beryllium and was cooled to 5.5 K. The satellite contains three instruments that allowed it to perform imaging and photometry from 3 to 180 micrometers, spectroscopy from 5 to 40 micrometers, and spectrophotometry from 5 to 100 micrometers. Without liquid helium to cool the telescope to the very cold temperatures needed to operate, most instruments are no longer usable. However, the two shortest wavelength modules of the IRAC camera are still operable with the same sensitivity as before the cryogen was exhausted, and will continue to be used in the Spitzer Warm Mission.>>

<<The Herschel Space Observatory is a space observatory sensitive to the far infrared and submillimetre wavebands. It was carried into orbit in May 2009, reaching the second Lagrangian point (L2) of the Earth-Sun system, 1,500,000 kilometres from the Earth.

Herschel is charged with four primary areas of investigation:

• * Galaxy formation in the early universe and the evolution of galaxies;
  * Star formation and its interaction with the interstellar medium;
  * Chemical composition of atmospheres and surfaces of Solar System bodies, including planets, comets and moons;
  * Molecular chemistry across the universe.

The mission, formerly titled the Far Infrared and Sub-millimetre Telescope (FIRST), involves the first space observatory to cover the full far infrared and submillimetre waveband. At 3.5 meters wide, its telescope incorporates the largest mirror (made not from glass but from sintered silicon carbide) ever deployed in space. The light is focused onto three instruments with detectors kept at temperatures below 2 K. The instruments are cooled with liquid helium, boiling away in a near vacuum at a temperature of approximately 1.4 K. The 2,000-litre supply of helium on board the spacecraft will limit its operational lifetime, nonetheless it is expected to be operational for at least 3 years.>>

[Chris Peterson]

Chris - I can understand how heat could slowly collect when in sunlight, but I don't understand what is generating the heat when there is no sunlight present like when behind the moon or earth from the sun.

The shadowed portions of both the Earth and Moon radiate lots of heat. The Earth because the surface was absorbing heat from the Sun for half a day, and also because the atmosphere is warm, and the Moon because the surface was warmed for half a day as well. The amount of heat being radiated is high compared to the operating temperature of the IR camera.

I didn't know that spacesuits had to provide for ridding of extra heat in addition to their other functions.

Yes. An astronaut is pumping out around 100 watts. That turns into heat, and getting rid of heat in a vacuum is hard, because radiative dissipation is inefficient. It is much easier to dump heat convectively, but that requires an atmosphere.

[neufer]

Chris - I can understand how heat could slowly collect when in sunlight, but I don't understand what is generating the heat when there is no sunlight present like when behind the moon or earth from the sun.

The shadowed portions of both the Earth and Moon radiate lots of heat. The Earth because the surface was absorbing heat from the Sun for half a day, and also because the atmosphere is warm, and the Moon because the surface was warmed for half a day as well. The amount of heat being radiated is high compared to the operating temperature of the IR camera.

Nighttime lunar temperatures only average about 100 K so this isn't much of a problem per se.

However, at 390 K daytime lunar thermal radiation is ~6 times more intense than (an equivalent solid angle of) Earth nighttime thermal radiation;
hence, the L2 located Webb telescope receives about 20% of it's contaminating thermal radiation from the moon during half moon situations.

I didn't know that spacesuits had to provide for ridding of extra heat in addition to their other functions.

Yes. An astronaut is pumping out around 100 watts. That turns into heat, and getting rid of heat in a vacuum is hard, because radiative dissipation is inefficient. It is much easier to dump heat convectively, but that requires an atmosphere.

I find that dumping 'hot air' into the internet works just fine for me.

<<Recommended daily energy intake values for young adults and men are: 2500 kcal/day (121 watts) and 2000 kcal/day (97 watts) for women. Children and sedentary and older people require less energy, physically active people more. In addition to physical activity, increased mental activity has been linked with moderately increased brain energy consumption.

The human body uses the energy released by respiration for a wide range of purposes: about twenty percent of the energy (22 watts ) is used for brain metabolism, and much of the rest is used for the basal metabolic requirements of other organs and tissues. Among the diverse uses for energy, one is the production of mechanical energy by skeletal muscle in order to maintain posture and produce motion.

In general, the efficiency of muscles is rather low: only 18 to 26 percent of the energy (25 watts) available from respiration is converted into mechanical energy. This low efficiency is the result of about 40% efficiency of generating ATP from food energy, losses in converting energy from ATP into mechanical work inside the muscle, and mechanical losses inside the body. For an overall efficiency of 20 percent. It can take up to 20 hours of little physical output (e.g. walking) to "burn off" 4000 kcal (235 watts) more than a body would otherwise have.>>

<<Watt was Samuel Beckett's second published novel in English, largely written on the run in the south of France during the Second World War and published in 1953.

Narrated in four parts, it describes Watt's journey to (and within) Mr Knott's house; here he becomes the reclusive owner's manservant, replacing Arsene, who delivers a long valedictory monologue. In section two Watt struggles to make sense of life at Mr Knott's house, experiencing deep anxiety at the visit of the piano tuning Galls, father & son, and a mysteriously language-resistant pot. In section three Watt is in confinement, his language garbled almost beyond recognition. The fourth section shows Watt arriving at the railway station from which, in the novel's skewed chronology, he sets out on a journey to the institution he has already reached in section three. The novel concludes with a series of Addenda, whose incorporation into the text 'only fatigue and disgust' have prevented.

Watt is characterised by an almost hypnotic use of repetition, extreme deadpan philosophical humour, deliberately unidiomatic English such as Watt's 'facultative' tram stop, and visual exempla such as a frogs' chorus. The novel's final words are 'no symbols where none intended'. Described as "the white whale of Beckett studies, a mass of documentation that defies attempts to make sense of it.">>

[biddie67]

(( laughing )) Watt whaaaaaa??? neufer, you do make such unexpected tangential turns off into your own orbit - I suspect that you are working your way to locating that mythical Lagrange 11 ....

I was so carefully reading through the various paragraphs above, trying so very hard to assimilate the different trials and tribulations of the several infrared space telescopes when I hit the wall, er, that is the Watt .....

But seriously, I do appreciate both of you for taking the time to come back to this day-old APOD and adding your comments and references. I really wish that I had stumbled upon this field of study when I was just out of high school ....

[Chris Peterson]

Nighttime lunar temperatures only average about 100 K so this isn't much of a problem per se.

Actually, it is. 100 K surfaces emit a lot of radiation, when you consider that you're trying to keep your sensor at just a fraction of a Kelvin (with the liquid helium cooled cameras). Even the 3 K background in deep interstellar space would be an issue.

[neufer]

Nighttime lunar temperatures only average about 100 K so this isn't much of a problem per se.

Actually, it is. 100 K surfaces emit a lot of radiation, when you consider that you're trying to keep your sensor at just a fraction of a Kelvin (with the liquid helium cooled cameras). Even the 3 K background in deep interstellar space would be an issue.

It might be an issue for an infrared telescope on or near to the moon but no one has proposed such a telescope as yet.

100 K is 60 times colder than the Sun! Hence, since the Sun keeps the Earth at an ambient (radiative) temperature of 250 K then a new moon alone would only be able to keep the Earth at an ambient temperature of ~4 K (liquid helium/Spitzer temperature and not much above the 3 K background).

A full moon alone would be able to keep the Earth at an ambient temperature of ~16 K (liquid hydrogen/WISE temperature)

[Chris Peterson]

It might be an issue for an infrared telescope on or near to the moon but no one has proposed such a telescope as yet.

I beg to differ. Biddie67 proposed just that earlier in this discussion, and it was that case I was responding to.

[neufer]

It might be an issue for an infrared telescope on or near to the moon but no one has proposed such a telescope as yet.

I beg to differ. Biddie67 proposed just that earlier in this discussion, and it was that case I was responding to.

Let me be VERY clear about what I am saying:

• Space infrared telescopes MUST be concerned with 3 things FIRST & FOREMOST:
  
  • 1) Radiation from the Sun
    2) Radiation from the Earth and
    3) Radiation from the warm side of the Moon.

Radiation from the dark side of the Moon, other planets & stars, the Milky Way, and the CBR
while NOT unimportant are, at least, TWO ORDERS of magnitude LESS important than ANY of the above three.

These MINOR radiation sources are ONLY important in so far as
maintaining VERY COLD liquid helium temperatures for a long period of time.