# Planet Formation in Orion

The Spitzer Space Telescope has peered into the Orion nebula with striking results: nearly 2300 planet-forming disks in the overall Orion cloud complex, a star-forming region some 1450 light years from Earth. This is where infrared truly shines, for such disks are too small to be seen with visible-light telescopes. But Spitzer is made to order for picking up the infrared signature of warm dust, giving us an unprecedented look at solar system formation in the aggregate. The image below gives a glimpse, but be sure to click to enlarge the photograph for a bit more detail.

Thomas Megeath (University of Toledo, OH) likens the research to a census of potential solar systems, saying “…we want to know how many are born in the cities, how many in small towns, and how many out in the countryside.” Megeath and colleagues discovered that 60 percent of the disk-bearing stars in the Orion cloud complex are found in clusters of hundreds of stars, while 15 percent exist in much smaller groupings, with a surprisingly high 25 percent in relative isolation. That may force an adjustment to earlier theories that most young stars would be found in relatively crowded locales.

Image: A Spitzer Space Telescope view of the Orion nebula, our closest massive star-making factory. The nebula is close enough to appear to the naked eye as a fuzzy star in the sword of the popular hunter constellation. Credit: NASA/JPL-Caltech/ T. Megeath (University of Toledo).

Another key issue: If 60 to 70 percent of the stars in the Orion complex have disks, what constraints keep the other stars from developing them? Understanding how disks form in these environments may tell us much about how planets come to be, and perhaps help us examine our own Sun’s birth. Did Sol come from a crowded city of stars or a relatively sparse stellar environment? Because stars drift away from their place of origin, answering that question can be tricky, but this Spitzer study gives us plenty of new material to work with.

Centauri Dreams‘ take: Stepping back from the details, what stands out here is the sheer fecundity of planetary formation. 2300 budding solar systems in this study alone — we seem to live in a universe that will make planets whenever and wherever it can. The implications for astrobiology are both obvious and heartening.

Comments on this entry are closed.

• logtar August 17, 2006, 17:59

Looks gorgeous!

• ljk January 16, 2008, 11:18

Dust in the disk winds from young stars as a source of the circumstellar extinction

Authors: L.V. Tambovtseva, V.P. Grinin

(Submitted on 15 Jan 2008)

Abstract: We examine a problem of the dust grains survival in the disk wind in T Tauri stars (TTSs). For consideration we choose the disk wind model described by Garcia et al. (2001), where a gas component of the wind is heated by an ambipolar diffusion up to the temperature of the order of 10$^4$ K. It is shown that the dust grains heating due to collisions with the gas atoms and electrons is inefficient in comparison with heating by the stellar radiation, and thus, dust survives even in the hot wind component. Owing to this, the disk wind may be opaque for the ultraviolet and optical radiation of the star and is capable to absorb its noticeable fraction. Calculations show that at the accretion rate $\dot{M_a} = 10^{-8}-10^{-6} M_\odot$ per year this fraction for TTSs may range from 20% to 40% of a total luminosity of the star correspondingly. This means that the disk wind in TTSs can play the same role as the puffed inner rim considered in the modern models of accretion disks. In Herbig Ae stars (HAEs) inner regions of the disk winds ($r \le 0.5$ AU) are free of dust since there dust grains sublimate under the effect of the radiation of the star. Therefore, in this case a fraction of the absorbed radiation by the disk wind is significantly less, and may be compared with the effect of the “puffed-up inner rim” only at $\dot{M_a} \geq 10^{-6} M_\odot$ yr$^{-1}$. Due to the structural inhomogeneity of the disk wind its optical depth towards an observer may be variable resulting in the photometric activity of the young stars. For the same reason, one can observe moving shadows from the gas and dust streams with the spiral-like structure on the highly resolved circumstellar disk images.

Comments: 12 pages, 5 figures. accepted by Astronomy Letters

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0801.2236v1 [astro-ph]

Submission history

[v1] Tue, 15 Jan 2008 09:26:21 GMT (231kb)

http://arxiv.org/abs/0801.2236

• ljk April 9, 2008, 9:28

Integral field spectroscopy of protoplanetary disks in Orion with VLT FLAMES
Authors: Y. G. Tsamis (1), J. R. Walsh (2), D. Péquignot (3) ((1) UCL, (2) ESO, (3) Meudon)

(Submitted on 7 Apr 2008)

Abstract: We discuss integral field spectroscopy of proplyds in M42 using the FLAMES Argus unit and report the first detection of recombination lines of C II and O II from the archetypical Laques-Vidal-2 object. These lines can provide important new diagnostics of the physical conditions in proplyds. We also draw attention to the future capabilities of the MUSE spectrograph in relation to similar studies.

Comments: 5 pages; 3 figs; To appear in proceedings of “Science with the VLT in the ELT era” (ESO Garching, Oct. 2007)

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0804.1100v1 [astro-ph]

Submission history

From: Yiannis Tsamis [view email]

[v1] Mon, 7 Apr 2008 18:12:14 GMT (73kb)

http://arxiv.org/abs/0804.1100

• ljk July 10, 2008, 12:03

Sun-like Stars May Have Low Probability of Forming Planets

Written by Nancy Atkinson

The Orion Nebula shines brilliantly, as it is packed with over 1,000 young stars in a region just a few light-years wide. With all those stars, there’s probably the potential for thousands of planets to one day form from the dust and gas surrounding these stars, right?

Actually, according to a new study, fewer than 10 percent of stars in the Orion Nebula have enough surrounding dust to make a planet the size of Jupiter. And that doesn’t bode well for the planet-forming abilities of most stars, at least in forming planets the size of Jupiter or larger.

“We think that most stars in the galaxy are formed in dense, Orion-like regions, so this implies that systems like ours may be the exception rather than the rule,” said Joshua Eisner lead author of the study from the University of California Berkeley.

This finding is also consistent with the results of current planet searches, which are finding that only about 6 percent of stars surveyed have planets the size of Jupiter or larger.

In the observations of Orion’s central region of more than 250 known stars, the findings showed that only about 10 percent emit the wavelength radiation typically emitted by a warm disk of dust, (1.3-millimeter). Even fewer – less than 8 percent of stars surveyed – were found to have dust disks with masses greater than one-hundredth the mass of the sun, which is thought to be the lower mass limit for the formation of Jupiter-sized planets. The average mass of a protoplanetary disk in the region was only one-thousandth of a solar mass, the researchers calculated.