protostar – Behind The Black

Webb takes false-color infrared image of bi-polar protostar nebula

July 2, 2024 10:02 am Robert Zimmerman

Click for original image.

Scientists using the Webb Space Telescope have now produced a new false-color infrared image of the bi-polar hour-glass-shaped protostar nebula dubbed L1527.

That image is to the left, created from data from Webb’s MIRI (Mid-Infrared Instrument) and cropped, reduced, and sharpened to post here. While it is not quite a pretty as a prevous Webb infrared image taken in 2022 by its NIRCam (Near-Infrared Camera), it provides new information about the make-up of materials within this nebula. From the caption:

The areas colored here in blue, which encompass most of the hourglass, show mostly carbonaceous molecules known as polycyclic aromatic hydrocarbons. The protostar itself and the dense blanket of dust and a mixture of gases that surround it are represented in red. (The sparkler-like red extensions are an artifact of the telescopes’s optics). In between, MIRI reveals a white region directly above and below the protostar, which doesn’t show as strongly in the NIRCam view. This region is a mixture of hydrocarbons, ionized neon, and thick dust, which shows that the protostar propels this matter quite far away from it as it messily consumes material from its disk.

Previous to Webb, this object had mostly been studied in 2012 using radio and submillimeter wavelengths (see the papers here and here), but those papers determined this is possibly the youngest known protostar, less than 100,000 years old.

The tangled view of astronomers

March 25, 2024 11:06 am Robert Zimmerman

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The uncertainty of science: The picture to the right, cropped, reduced, and sharpened to post here, was taken by the Hubble Space Telescope as part of a survey of young stars surrounded by an edge-on dust disk. From the caption:

FS Tau is a multi-star system made up of FS Tau A, the bright star-like object near the middle of the image, and FS Tau B (Haro 6-5B), the bright object to the far right that is partially obscured by a dark, vertical lane of dust. The young objects are surrounded by softly illuminated gas and dust of this stellar nursery. The system is only about 2.8 million years old, very young for a star system. Our Sun, by contrast, is about 4.6 billion years old.

The blue lines on either side of that vertical dust lane are jets moving out from FS Tau B. The caption says their asymetrical lengths are likely due to ” mass is being expelled from the object at different rates,” but it just as easily be caused by the angle in which we see this object, making the nearer jet seem longer than the one behind.

That astronomers cannot move around such an object and see it from many angles explains the headline of this post. We can only see astronomical objects from one angle, and when they are complex objects such as this one, a large part of the research problem is disentangling the shapes we see into a coherent picture. Spectroscopy helps a lot, as it provides information about the speed and direction of different parts of the object, but even this can be enormously complicated and difficult to interpret.

Remember these facts when you read news reports about astronomical research. No matter how certain the press release sounds, its certainty is always tempered by many unknowns, some very pedestrian but fundamental.

Optical image of accretion disk around baby star, taken by ground-based VLT

July 26, 2023 10:59 am Robert Zimmerman

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Scientists today released an optical image of the accretion disk that surrounds a baby star about 5,000 light years away, taken by ground-based Very Large Telescope (VLT) in Chile and enhanced by data from the Atacama Large Millimeter/submillimeter Array (ALMA), also in Chile.

That image, reduced to post here, is to the right. The bright blue spot in the center is the main star, with the smaller dot to the lower left a companion star. From the press release:

The VLT observations probe the surface of the dusty material around the star, while ALMA can peer deeper into its structure. “With ALMA, it became apparent that the spiral arms are undergoing fragmentation, resulting in the formation of clumps with masses akin to those of planets,” says Zurlo.

Astronomers believe that giant planets form either by ‘core accretion’, when dust grains come together, or by ‘gravitational instability’, when large fragments of the material around a star contract and collapse. While researchers have previously found evidence for the first of these scenarios, support for the latter has been scant.

This data suggests that the latter is being observed, the first time gravitational instability has been identified as it is happening. You can read the scientist’s research paper here [pdf].

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Astronomers discover complex molecules in protostar accretion disk

June 29, 2017 10:18 am Robert Zimmerman

Astronomers have discovered several complex molecules in the accretion disk surrounding a very young baby star about 1300 light years away in the constellation Orion.

The research team’s ALMA observations have clearly detected an atmosphere of complex organic molecules above and below the disk. These include methanol (CH3OH), deuterated methanol (CH2DOH), methanethiol (CH3SH), and formamide (NH2CHO). These molecules have been proposed to be the precursors for producing biomolecules such as amino acids and sugars. “They are likely formed on icy grains in the disk and then released into the gas phase because of heating from stellar radiation or some other means, such as shocks,” says co-author Zhi-Yun Li of the University of Virginia.

What is even most interesting about this discovery is that these complex molecules are not scattered throughout the disk, but are concentrated in regions above and below its central plane, what the astronomers are labeling “an atmosphere.” This suggests that differentiation — the same process that separates the heavier molecules from lighter ones both in centrifuges and in the cores of planets — occurs quickly in accretion disks as well.

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