Proplyd

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Proplyds in the Orion Nebula Orion Nebula with proplyd highlights (captured by the Hubble Space Telescope).jpg
Proplyds in the Orion Nebula

A proplyd, short for ionized protoplanetary disk, is an externally illuminated photoevaporating protoplanetary disk around a young star. Nearly 180 proplyds have been discovered in the Orion Nebula. [1] Images of proplyds in other star-forming regions are rare, while Orion is the only region with a large known sample due to its relative proximity to Earth. [2]

Contents

History

In 1979 observations with the Lallemand electronic camera at the Pic-du-Midi Observatory showed six unresolved high-ionization sources near the Trapezium Cluster. These sources were not interpreted as proplyds, but as partly ionized globules (PIGs). The idea was that these objects are being ionized from the outside by M42. [3] Later observations with the Very Large Array showed solar-system-sized condensations associated with these sources. Here the idea appeared that these objects might be low-mass stars surrounded by an evaporating protostellar accretion disk. [4]

Proplyds were clearly resolved in 1993 using images of the Hubble Space Telescope Wide Field Camera and the term "proplyd" was used. [5]

Characteristics

Illustration of the dynamics of a proplyd, including an astrophysical jet Opo0113i.jpg
Illustration of the dynamics of a proplyd, including an astrophysical jet

In the Orion Nebula the proplyds observed are usually one of two types. Some proplyds glow around luminous stars, in cases where the disk is found close to the star, glowing from the star's luminosity. Other proplyds are found at a greater distance from the host star and instead show up as dark silhouettes due to the self-obscuration of cooler dust and gases from the disk itself. Some proplyds show signs of movement from solar irradiance shock waves pushing the proplyds. The Orion Nebula is approximately 1,500 light-years from the Sun with very active star formation. The Orion Nebula and the Sun are in the same spiral arm of the Milky Way galaxy. [6] [7] [8] [9]

A proplyd may form new planets and planetesimal systems. Current models show that the metallicity of the star and proplyd, along with the correct planetary system temperature and distance from the star, are keys to planet and planetesimal formation. To date, the Solar System, with 8 planets, 5 dwarf planets and 5 planetesimal systems, is the largest planetary system found. [10] [11] [12] Most proplyds develop into a system with no planetesimal systems, or into one very large planetesimal system. [13] [14] [15] [16] [17] [18]

Proplyds in other star-forming regions

Dusty proplyds pointing to HD 17505 in Westerhout 5 as seen by the Spitzer Space Telescope Devastated Stellar Neighborhood.jpg
Dusty proplyds pointing to HD 17505 in Westerhout 5 as seen by the Spitzer Space Telescope

Photoevaporating proplyds in other star forming regions were found with the Hubble Space Telescope. NGC 1977 currently represents the star-forming region with the largest number of proplyds outside of the Orion Nebula, with 7 confirmed proplyds. It was also the first instance where a B-type star, 42 Orionis is responsible for the photoevaporation. [19] In addition, 4 clear and 4 candidate proplyds were discovered in the very young region NGC 2024, two of which have been photoevaporated by a B star. [20] The NGC 2024 proplyds are significant because they imply that external photoevaporation of protoplanetary disks could compete even with very early planet formation (within the first half a million years).

Another type of photoevaporating proplyd was discovered with the Spitzer Space Telescope. These cometary tails represent dust being pulled away from the disks. [21] Westerhout 5 is a region with many dusty proplyds, especially around HD 17505. [22] These dusty proplyds are depleted of any gas in the outer regions of the disk, but the photoevaporation could leave an inner, more robust, and possibly gas-rich disk component of radius 5-10 astronomical units. [23]

The proplyds in the Orion Nebula and other star-forming regions represent proto-planetary disks around low-mass stars being externally photoevaporated. These low-mass proplyds are usually found within 0.3 parsec (60,000 astronomical units) of the massive OB star and the dusty proplyds have tails with a length of 0.1 to 0.2 parsec (20,000 to 40,000 au). [21] There is a proposed type of intermediate massive counterpart, called proplyd-like objects. Objects in NGC 3603 and later in Cygnus OB2 were proposed as intermediate massive versions of the bright proplyds found in the Orion Nebula. The proplyd-like objects in Cygnus OB2 for example are 6 to 14 parsec distant to a large collection of OB stars and have tail lengths of 0.11 to 0.55 parsec (24,000 to 113,000 au). [24] [25] The nature of proplyd-like objects as intermediate massive proplyds is partly supported by a spectrum for one object, which showed that the mass loss rate is higher than the mass accretion rate. Another object did not show any outflow, but accretion. [26]

List of star-forming regions with proplyds

List is sorted after distance.

Star-Forming region (SFR)Distance

(light-years)

Age of SFR

(Myrs)

Ionizing starsspectral type of

ionizing stars

Number of proplydstype of proplydReferences
NGC 1977 13054 42 Orionis B1V7gaseous + dusty tails [27] [19]
Lambda Orionis Cluster 13056 Meissa O8IIIf+B0.5V2dusty tails [28]
Orion Nebula 13441 Theta1 Orionis C O6Vp+B0V178gaseous + dark disks [1] [27]
Flame Nebula 13500.2 to 0.5IRS1, IRS2bB0.5V, O8V4 or 8gaseous [20]
NGC 2264 26094 S Mon O7Ve1dusty tails [29]
IC 1396 27233 HD 206267 O6V1dusty tails [29]
NGC 6193 37835 HD 150136, CD-48 11071O3.5-4III(f*)+O6IV, B0V8 or 9dusty tails [30]
Cygnus OB2 45663-5Cluster of O-stars11large "proplyd-like" objects + dusty tails [31] [32]
NGC 2244 48924 HD 46150 O5V1dusty tails [29]
Trifid Nebula 54798HD 164492AO7.51gaseous [27] [33]
Pismis 24 55441Pis 24-1, Pis 24-2O3I, O5.5 V(f)5gaseous [34]
Lagoon Nebula 58715Herschel 36O7V1gaseous [27] [35]
Westerhout 5 75005HD 17505, HD 18326O6.5III((f))n+O8V, O7V4dusty tails [36] [22]
Carina Nebula (disputed) [37] 75013Cluster of O-stars"dozens"large "proplyd-like" objects + dark disks [38]
NGC 3603 195691Cluster of O-stars3large "proplyd-like" objects [27] [39]
Sgr A* 26673unknownMultiple O- and WR-stars 34gaseous [40]

See also

Related Research Articles

<span class="mw-page-title-main">Orion Nebula</span> Diffuse nebula in the constellation Orion

The Orion Nebula is a diffuse nebula situated in the Milky Way, being south of Orion's Belt in the constellation of Orion,[b] and is known as the middle "star" in the "sword" of Orion. It is one of the brightest nebulae and is visible to the naked eye in the night sky with an apparent magnitude of 4.0. It is 1,344 ± 20 light-years (412.1 ± 6.1 pc) away and is the closest region of massive star formation to Earth. The M42 nebula is estimated to be 24 light-years across. It has a mass of about 2,000 times that of the Sun. Older texts frequently refer to the Orion Nebula as the Great Nebula in Orion or the Great Orion Nebula.

<span class="mw-page-title-main">H II region</span> Large, low-density interstellar cloud of partially ionized gas

An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds of light years, and density from a few to about a million particles per cubic centimetre. The Orion Nebula, now known to be an H II region, was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered.

<span class="mw-page-title-main">Nebular hypothesis</span> Astronomical theory about the Solar System

The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System. It suggests the Solar System is formed from gas and dust orbiting the Sun which clumped up together to form the planets. The theory was developed by Immanuel Kant and published in his Universal Natural History and Theory of the Heavens (1755) and then modified in 1796 by Pierre Laplace. Originally applied to the Solar System, the process of planetary system formation is now thought to be at work throughout the universe. The widely accepted modern variant of the nebular theory is the solar nebular disk model (SNDM) or solar nebular model. It offered explanations for a variety of properties of the Solar System, including the nearly circular and coplanar orbits of the planets, and their motion in the same direction as the Sun's rotation. Some elements of the original nebular theory are echoed in modern theories of planetary formation, but most elements have been superseded.

<span class="mw-page-title-main">Protoplanetary disk</span> Gas and dust surrounding a newly formed star

A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may not be considered an accretion disk, while the two are similar. While they are similar, an accretion disk is hotter, and spins much faster. It is also found on black holes, not stars. This process should not be confused with the accretion process thought to build up the planets themselves. Externally illuminated photo-evaporating protoplanetary disks are called proplyds.

<span class="mw-page-title-main">Rogue planet</span> Planets not gravitationally bound to a star

A rogue planet, also termed a free-floating planet (FFP) or an isolated planetary-mass object (iPMO), is an interstellar object of planetary mass which is not gravitationally bound to any star or brown dwarf.

Photoevaporation is the process where energetic radiation ionises gas and causes it to disperse away from the ionising source. The term is typically used in an astrophysical context where ultraviolet radiation from hot stars acts on clouds of material such as molecular clouds, protoplanetary disks, or planetary atmospheres.

<span class="mw-page-title-main">Orion molecular cloud complex</span> Star-forming region in the constellation Orion

The Orion molecular cloud complex is a star-forming region with stellar ages ranging up to 12 Myr. Two giant molecular clouds are a part of it, Orion A and Orion B. The stars currently forming within the complex are located within these clouds. A number of other somewhat older stars no longer associated with the molecular gas are also part of the complex, most notably the Orion's Belt, as well as the dispersed population north of it. Near the head of Orion there is also a population of young stars that is centered on Meissa. The complex is between 1 000 and 1 400 light-years away, and hundreds of light-years across.

<span class="mw-page-title-main">Sh 2-279</span> Emission nebula in the constellation Orion

Sh 2-279 is an HII region and bright nebulae that includes a reflection nebula located in the constellation Orion. It is the northernmost part of the asterism known as Orion's Sword, lying 0.6° north of the Orion Nebula. The reflection nebula embedded in Sh 2-279 is popularly known as the Running Man Nebula.

<span class="mw-page-title-main">NGC 2547</span> Open cluster in the constellation Vela

NGC 2547 is a southern open cluster in Vela, discovered by Nicolas Louis de Lacaille in 1751 from South Africa. The star cluster is young with an age of 20-30 million years.

<span class="mw-page-title-main">Flame Nebula</span> Emission nebula in the constellation Orion

The Flame Nebula, designated as NGC 2024 and Sh2-277, is an emission nebula in the constellation Orion. It is about 1350 light-years away. At that distance, the Flame Nebula lies within the Orion B cloud of the larger Orion Molecular Cloud Complex.

<span class="mw-page-title-main">Debris disk</span> Disk of dust and debris in orbit around a star

A debris disk, or debris disc, is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris disks are found around stars with mature planetary systems, including at least one debris disk in orbit around an evolved neutron star. Debris disks can also be produced and maintained as the remnants of collisions between planetesimals, otherwise known as asteroids and comets.

<span class="mw-page-title-main">NGC 2244</span> Open cluster within the Rosette nebula, in the constellation Monoceros

NGC 2244 is an open cluster in the Rosette Nebula, which is located in the constellation Monoceros. This cluster has several O-type stars, super hot stars that generate large amounts of radiation and stellar wind.

<span class="mw-page-title-main">AB Aurigae</span> Star in the constellation Auriga

AB Aurigae is a young Herbig Ae star in the Auriga constellation. It is located at a distance of approximately 531 light years from the Sun based on stellar parallax. This pre-main-sequence star has a stellar classification of A0Ve, matching an A-type main-sequence star with emission lines in the spectrum. It has 2.4 times the mass of the Sun and is radiating 38 times the Sun's luminosity from its photosphere at an effective temperature of 9,772 K. The radio emission from the system suggests the presence of a thermal jet originating from the star with a velocity of 300 km s−1. This is causing an estimated mass loss of 1.7×10−8 M☉ yr−1.

<span class="mw-page-title-main">Lambda Orionis Cluster</span>

The Lambda Orionis Cluster is an open star cluster located north-west of the star Betelgeuse in the constellation of Orion. It is about five million years old and roughly 1,300 ly (400 pc) away from the Sun. Included within the cluster is a double star named Meissa. With the rest of Orion, it is visible from the middle of August in the morning sky, to late April before Orion becomes too close to the Sun to be seen well. It can be seen from both the northern hemisphere and the southern hemisphere.

<span class="mw-page-title-main">Cometary knot</span> Structure in some planetary nebulae

Cometary knots, also referred as globules, are structures observed in several nearby planetary nebulae (PNe), including the Helix Nebula, the Ring Nebula, the Dumbbell Nebula, the Eskimo Nebula, and the Retina Nebula. They are believed to be a common feature of the evolution of planetary nebulae, but can only be resolved in the nearest examples. They are generally larger than the size of the Solar System, with masses of around 0.00001 times the mass of the Sun, which is comparable to the mass of the Earth. There are about 40,000 cometary knots in the Helix Nebula.

<span class="mw-page-title-main">NGC 3862</span> Galaxy in the constellation Leo

NGC 3862 is an elliptical galaxy located 300 million light-years away in the constellation Leo. Discovered by astronomer William Herschel on April 27, 1785, NGC 3862 is an outlying member of the Leo Cluster.

<span class="mw-page-title-main">NGC 4299</span> Spiral galaxy in the constellation Virgo

NGC 4299 is a featureless spiral galaxy located about 55 million light-years away in the constellation Virgo. It was discovered by astronomer William Herschel on March 15, 1784 and is a member of the Virgo Cluster.

<span class="mw-page-title-main">HH 1/2</span> Herbig-Haro object in the constellation Orion

The Herbig-Haro objects HH 1/2 are the first such objects to be recognized as Herbig-Haro objects and were discovered by George Herbig and Guillermo Haro. They are located at a distance of about 1343 light-years in the constellation Orion near NGC 1999. HH 1/2 are among the brightest Herbig-Haro objects in the sky and consist of a pair of oppositely oriented bow shocks, separated by 2.5 arcminutes. The HH 1/2 pair were the first Herbig-Haro objects with detected proper motion and HH 2 was the first Herbig-Haro object to be detected in x-rays. Some of the structures in the Herbig-Haro Objects move with a speed of 400 km/s.

References

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  37. ↑ Sahai, R.; Güsten, R.; Morris, M. R. (2012-12-01). "Are Large, Cometary-shaped Proplyds Really (Free-floating) Evaporating Gas Globules?". The Astrophysical Journal. 761 (2): L21. arXiv: 1211.0345 . Bibcode:2012ApJ...761L..21S. doi:10.1088/2041-8205/761/2/L21. ISSN   0004-637X.
  38. ↑ Smith, Nathan; Bally, John; Morse, Jon A. (2003-04-01). "Numerous Proplyd Candidates in the Harsh Environment of the Carina Nebula". The Astrophysical Journal. 587 (2): L105–L108. Bibcode:2003ApJ...587L.105S. doi:10.1086/375312. ISSN   0004-637X.
  39. ↑ Brandner, Wolfgang; Grebel, Eva K.; Chu, You-Hua; Dottori, Horacio; Brandl, Bernhard; Richling, Sabine; Yorke, Harold W.; Points, Sean D.; Zinnecker, Hans (2000-01-01). "HST/WFPC2 and VLT/ISAAC Observations of Proplyds in the Giant H II Region NGC 3603". The Astronomical Journal. 119 (1): 292–301. arXiv: astro-ph/9910074 . Bibcode:2000AJ....119..292B. doi: 10.1086/301192 . ISSN   0004-6256.
  40. ↑ Yusef-Zadeh, F.; Roberts, D. A.; Wardle, M.; Cotton, W.; Schödel, R.; Royster, M. J. (2015-03-01). "Radio Continuum Observations of the Galactic Center: Photoevaporative Proplyd-like Objects Near Sgr A*". The Astrophysical Journal. 801 (2): L26. arXiv: 1502.03109 . Bibcode:2015ApJ...801L..26Y. doi:10.1088/2041-8205/801/2/L26. ISSN   0004-637X.
  41. ↑ Kirwan, A.; Manara, C. F.; Whelan, E. T.; Robberto, M.; McLeod, A. F.; Facchini, S.; Beccari, G.; Miotello, A.; Schneider, P. C.; Murphy, A.; Vicente, S. (2023-03-01). "A spectacular jet from the bright 244-440 Orion proplyd: the MUSE NFM view". Astronomy and Astrophysics. 673: A166. arXiv: 2303.13205 . Bibcode:2023A&A...673A.166K. doi:10.1051/0004-6361/202245428.
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