The icy blue wings of Hen 2-437

Hen 2-437

Credit: ESA/Hubble & NASA
Acknowledgement: Judy Schmidt (Geckzilla)

In this cosmic snapshot, the spectacularly symmetrical wings of Hen 2-437 show up in a magnificent icy blue hue. Hen 2-437 is a planetary nebula, one of around 3000 such objects known to reside within the Milky Way.

Located within the faint northern constellation of Vulpecula (The Fox), Hen 2-437 was first identified in 1946 by Rudolph Minkowski, who later also discovered the famous and equally beautiful M2-9 (otherwise known as the Twin Jet Nebula). Hen 2-437 was added to a catalogue of planetary nebula over two decades later by astronomer and NASA astronaut Karl Gordon Henize.

Planetary nebulae such as Hen 2-437 form when an aging low-mass star — such as the Sun — reaches the final stages of life. The star swells to become a red giant, before casting off its gaseous outer layers into space. The star itself then slowly shrinks to form a white dwarf, while the expelled gas is slowly compressed and pushed outwards by stellar winds. As shown by its remarkably beautiful appearance, Hen 2-437 is a bipolar nebula — the material ejected by the dying star has streamed out into space to create the two icy blue lobes pictured here.

Source: ESA/HUBBLE - Space Telescop/Images

NOAO: NGC 2346 - A Cosmic Butterfly’s Delicate Wings

Figure 1: The new image of NGC 2346 showing unprecedented resolution of the molecular hydrogen gas. The image is about 1 arc minute on a side: north is up, east is to the left. In contrast, the size of the full moon is 30 arc minutes.

Movie caption: Computer simulation showing how the nebula is expected to evolve over a period of about 9,000 years. Presently the nebula is just starting this process. The thumbnail above shows the process in nine, 1,000 year, steps. There is also a version of the movie that uses increments of 200 years.

NOAO scientists, using the Gemini Observatory 8-meter telescope in Chile, have obtained the highest resolution image ever obtained for the planetary nebula NGC 2346. Shaped like a butterfly, or an hourglass, but known scientifically as a bipolar planetary nebula, this object is at a distance of 2300 light years from our sun in the constellation Monoceros. 

The new observations of this gaseous nebula, shown in the first figure, resolve details comparable in size to our own solar system. The team detected previously unresolved knots and filaments of molecular hydrogen gas - details that no other telescope on the ground or in space, not even the Hubble Space Telescope, has been able to resolve. 

Molecular hydrogen in the bipolar lobes of NGC 2346 was detected almost 30 years ago, although previous observations suggested only a smooth torus. This filamentary structure observed by the team matches the mechanism they have proposed in which a hot bubble of gas surrounding the central star breaks out and fragments the shell of surrounding gas. The gaseous knots probably represent a common phenomenon that occurs whenever two fluids (or gasses) of different densities come in contact, and the lighter fluid is pushing on the heavier fluid. This is easily seen by anyone who has ever watched colored oil in a glass of water. 

The authors have constructed computer models to understand how the gasses are expected to interact: the accompanying movie shows how the gas will evolve in time. As first author Arturo Manchado said, “In this movie we show the model results in time steps up to 9000 yrs. The blue color corresponds with the emission of the molecular hydrogen gas. The model shows an initial toroid of cool gas at the equator. Once the swept-up shell is highly fragmented, the toroid is no longer visible and only the large clumps will be seen.”

NGC 2346 is a star caught in the final phases of its lifecycle. It began life as a double star system, each companion about twice as massive as the sun and both revolving around their common center of gravity. The more massive of the two stars burned through its fuel faster than its lower mass companion, expanded as a red giant, and has now shed its outer layers to become a white dwarf star, with a present mass between 0.3 and 0.7 solar masses. The bipolar nebula, or butterfly shape of this planetary, has probably been sculpted by the star pair, although this is still under study. With an orbital period of 16 days, the two stars are closer together than the sun and Mercury. Material spilling from the more massive star over the lifetime of the pair makes it difficult to calculate the initial mass of the star.

The observations were taken with the new near infra-red Adaptive Optics Imager system on the Gemini telescope during the initial testing phase of this instrument. Adaptive optics is a novel technique that allows for real time correction of distortions to an astronomical image caused by the earth’s atmosphere.

The paper will appear in the Astrophysical Journal (Authors Arturo Manchado, Letizia Stanghellini, Eva Villaver, Guillermo García-Segura, Richard A. Shaw and D. A. García-Hernández)

NOAO is operated by Association of Universities for Research in Astronomy Inc. (AURA) under a cooperative agreement with the National Science Foundation.

Media Contact:

Dr. Katy Garmany
Deputy Press Officer
National Optical Astronomy Observatory
950 N Cherry Ave
Tucson AZ 85719 USA
+1 520-318-8526
E-mail: kgarmany@noao.edu


Science Contact

Dr. Letizia Stanghellini 
NOAO 
E-mail: lstanghellini@noao.eu

Source: National Optical Astronomy Observatory (NOAO)

Bizarre Alignment of Planetary Nebulae

PR Image eso1338a

Bipolar planetary nebula NGC 6537

PR Image eso1338b

A gallery of bipolar planetary nebulae

PR Image eso1338c

Bipolar planetary nebula Hubble 12

Astronomers have used ESO's New Technology Telescope and the NASA/ESA Hubble Space Telescope to explore more than 100 planetary nebulae in the central bulge of our galaxy. They have found that butterfly-shaped members of this cosmic family tend to be mysteriously aligned — a surprising result given their different histories and varied properties.

The final stages of life for a star like our Sun result in the star blowing its outer layers out into the surrounding space, forming objects known as planetary nebulae in a wide range of beautiful and striking shapes. One type of such nebulae, known as bipolar planetary nebulae, create ghostly hourglass or butterfly shapes around their parent stars.

All these nebulae formed in different places and have different characteristics. And neither the individual nebulae, nor the stars that formed them, would have interacted with other planetary nebulae. However, a new study by astronomers from the University of Manchester, UK, now shows surprising similarities between some of these nebulae: many of them line up in the sky in the same way [1].

"This really is a surprising find and, if it holds true, a very important one," explains Bryan Rees of the University of Manchester, one of the paper's two authors. "Many of these ghostly butterflies appear to have their long axes aligned along the plane of our galaxy. By using images from both Hubble and the NTT we could get a really good view of these objects, so we could study them in great detail."

The astronomers looked at 130 planetary nebulae in the Milky Way's central bulge. They identified three different types [2], and peered closely at their characteristics and appearance.

"While two of these populations were completely randomly aligned in the sky, as expected, we found that the third — the bipolar nebulae — showed a surprising preference for a particular alignment," says the paper's second author Albert Zijlstra, also of the University of Manchester. "While any alignment at all is a surprise, to have it in the crowded central region of the galaxy is even more unexpected."

Planetary nebulae are thought to be sculpted by the rotation of the star system from which they form. This is dependent on the properties of this system — for example, whether it is a binary [3], or has a number of planets orbiting it, both of which may greatly influence the form of the blown bubble. The shapes of bipolar nebulae are some of the most extreme, and are probably caused by jets blowing mass from the binary system perpendicular to the orbit.

"The alignment we're seeing for these bipolar nebulae indicates something bizarre about star systems within the central bulge," explains Rees. "For them to line up in the way we see, the star systems that formed these nebulae would have to be rotating perpendicular to the interstellar clouds from which they formed, which is very strange."

While the properties of their progenitor stars do shape these nebulae, this new finding hints at another more mysterious factor. Along with these complex stellar characteristics are those of our Milky Way; the whole central bulge rotates around the galactic centre. This bulge may have a greater influence than previously thought over our entire galaxy — via its magnetic fields. The astronomers suggest that the orderly behaviour of the planetary nebulae could have been caused by the presence of strong magnetic fields as the bulge formed.

As such nebulae closer to home do not line up in the same orderly way, these fields would have to have been many times stronger than they are in our present-day neighbourhood [4].

"We can learn a lot from studying these objects," concludes Zijlstra. "If they really behave in this unexpected way, it has consequences for not just the past of individual stars, but for the past of our whole galaxy."

Notes

[1] The "long axis" of a bipolar planetary nebula slices through the wings of the butterfly, whilst the "short axis" slices through the body.

[2] The shapes of the planetary nebula images were classified into three types, following conventions: elliptical, either with or without an aligned internal structure, and bipolar.

[3] A binary system consists of two stars rotating around their common centre of gravity.

[4] Very little is known about the origin and characteristics of the magnetic fields that were present in our galaxy when it was young, so it is unclear whether they have grown stronger over time, or decayed.

More information

The research is presented in a paper entitled "Alignment of the Angular Momentum Vectors of Planetary Nebulae in the Galactic Bulge", to appear in the Monthly Notices of the Royal Astronomical Society.

The team is composed of B. Rees (University of Manchester, UK), and A. A. Zijlstra (University of Manchester, UK). Bryan Rees came late to research astronomy — he decided to do a PhD after his early retirement and this work formed part of his thesis work.

ESO is the foremost intergovernmental astronomy organisation in Europe and the world's most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world's largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Links

• Research paper
• ESA/Hubble release
• Photos of the NTT

Contacts

Albert Zijlstra
University of Manchester
Manchester, UK
Tel: +44 1613 063925
Email: a.zijlstra@manchester.ac.uk

Bryan Rees
University of Manchester
Manchester, UK
Tel: +44 1612 754145
Email: bryan.rees@manchester.ac.uk

Richard Hook
ESO, Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org