Sagittarius A*

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https://en.wikipedia.org/wiki/Sagittarius_A* 

 

Sagittarius A*

Sgr A* (center) and two light echoes from a recent explosion (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Sagittarius
Right ascension	17h 45m 40.0409s
Declination	−29° 0′ 28.118″
Details
Mass	(4.154±0.014)×106  M☉
Astrometry
Distance	8178±13 pc
Database references
SIMBAD	data

Sagittarius A* (pronounced "Sagittarius A-Star", abbreviated Sgr A*) is a bright and very compact astronomical radio source at the Galactic Center of the Milky Way, near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic. It is the location of a supermassive black hole, similar to those at the centers of most, if not all, spiral galaxies and elliptical galaxies.

Observations of several stars orbiting Sagittarius A*, particularly star S2, have been used to determine the mass and upper limits on the radius of the object. Based on mass and increasingly precise radius limits, astronomers have concluded that Sagittarius A* is the Milky Way's central supermassive black hole.

Observation and description

ALMA observations of molecular-hydrogen

-rich gas clouds.

Astronomers have been unable to observe Sgr A* in the optical spectrum because of the effect of 25 magnitudes of extinction by dust and gas between the source and Earth. Several teams of researchers have attempted to image Sgr A* in the radio spectrum using very-long-baseline interferometry (VLBI). The current highest-resolution (approximately 30 μas) measurement, made at a wavelength of 1.3 mm, indicated an overall angular size for the source of 50 μas. At a distance of 26,000 light-years, this yields a diameter of 60 million kilometres. For comparison, Earth is 150 million kilometres from the Sun, and Mercury is 46 million kilometres from the Sun at perihelion. The proper motion of Sgr A* is approximately −2.70 mas per year for the right ascension and −5.6 mas per year for the declination.

In 2017, direct radio images were taken of Sagittarius A* and M87* by the Event Horizon Telescope. The Event Horizon Telescope uses interferometry to combine images taken from widely spaced observatories at different places on Earth in order to gain a higher picture resolution. It is hoped the measurements will test Einstein's theory of relativity more rigorously than has previously been done. If discrepancies between the theory of relativity and observations are found, scientists may have identified physical circumstances under which the theory breaks down.

In 2019, measurements made with the High-resolution Airborne Wideband Camera-Plus (HAWC+) revealed that magnetic fields cause the surrounding ring of gas and dust, temperatures of which range from −280 °F (−173.3 °C) to 17,500 °F (9,700 °C), to flow into an orbit around Sagittarius A*, keeping black hole emissions low.

History

Karl Jansky, considered a father of radio astronomy, discovered in August 1931 that a radio signal was coming from a location at the center of the Milky Way, in the direction of the constellation of Sagittarius; the radio source later became known as Sagittarius A. Later observations showed that Sagittarius A actually consists of several overlapping sub-components; a bright and very compact component Sgr A* was discovered on February 13 and 15, 1974, by astronomers Bruce Balick and Robert Brown using the baseline interferometer of the National Radio Astronomy Observatory. The name Sgr A* was coined by Brown in a 1982 paper because the radio source was "exciting", and excited states of atoms are denoted with asterisks.

Detection of an unusually bright X-ray flare from Sgr A*

On October 16, 2002, an international team led by Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics reported the observation of the motion of the star S2 near Sagittarius A* throughout a period of ten years. According to the team's analysis, the data ruled out the possibility that Sgr A* contains a cluster of dark stellar objects or a mass of degenerate fermions, strengthening the evidence for a massive black hole. The observations of S2 used near-infrared (NIR) interferometry (in the K-band, i.e. 2.2 μm) because of reduced interstellar extinction in this band. SiO masers were used to align NIR images with radio observations, as they can be observed in both NIR and radio bands. The rapid motion of S2 (and other nearby stars) easily stood out against slower-moving stars along the line-of-sight so these could be subtracted from the images.

Dusty cloud G2 passes the supermassive black hole at the center of the Milky Way

The VLBI radio observations of Sagittarius A* could also be aligned centrally with the NIR images, so the focus of S2's elliptical orbit was found to coincide with the position of Sagittarius A*. From examining the Keplerian orbit of S2, they determined the mass of Sagittarius A* to be 2.6±0.2 million solar masses, confined in a volume with a radius no more than 17 light-hours (120 AU). Later observations of the star S14 showed the mass of the object to be about 4.1 million solar masses within a volume with radius no larger than 6.25 light-hours (45 AU) or about 6.7 billion kilometres. S175 passed within a similar distance. For comparison, the Schwarzschild radius is 0.08 AU. They also determined the distance from Earth to the Galactic Center (the rotational center of the Milky Way), which is important in calibrating astronomical distance scales, as (8.0±0.6)×10³ parsecs. In November 2004 a team of astronomers reported the discovery of a potential intermediate-mass black hole, referred to as GCIRS 13E, orbiting 3 light-years from Sagittarius A*. This black hole of 1,300 solar masses is within a cluster of seven stars. This observation may add support to the idea that supermassive black holes grow by absorbing nearby smaller black holes and stars.

After monitoring stellar orbits around Sagittarius A* for 16 years, Gillessen et al. estimated the object's mass at 4.31±0.38 million solar masses. The result was announced in 2008 and published in The Astrophysical Journal in 2009. Reinhard Genzel, team leader of the research, said the study has delivered "what is now considered to be the best empirical evidence that supermassive black holes do really exist. The stellar orbits in the Galactic Center show that the central mass concentration of four million solar masses must be a black hole, beyond any reasonable doubt."

On January 5, 2015, NASA reported observing an X-ray flare 400 times brighter than usual, a record-breaker, from Sgr A*. The unusual event may have been caused by the breaking apart of an asteroid falling into the black hole or by the entanglement of magnetic field lines within gas flowing into Sgr A*, according to astronomers.

On 13 May 2019, astronomers using the Keck Observatory witnessed a sudden brightening of Sgr A*, which became 75 times brighter than usual, suggesting that the supermassive black hole may have encountered another object.

Supernova remnant ejecta producing planet-forming material

Central black hole

NuSTAR has captured these first, focused views of the supermassive black hole at the heart of the Milky Way in high-energy X-rays

 

A computer simulation of how central black hole might appear to the Event Horizon Telescope

In a paper published on October 31, 2018, the discovery of conclusive evidence that Sagittarius A* is a black hole was announced. Using the GRAVITY interferometer and the four telescopes of the Very Large Telescope (VLT) to create a virtual telescope 130 metres in diameter, astronomers detected clumps of gas moving at about 30% of the speed of light. Emission from highly energetic electrons very close to the black hole was visible as three prominent bright flares. These exactly match theoretical predictions for hot spots orbiting close to a black hole of four million solar masses. The flares are thought to originate from magnetic interactions in the very hot gas orbiting very close to Sagittarius A*.

In July 2018, it was reported that S2 orbiting Sgr A* had been recorded at 7,650 km/s, or 2.55% the speed of light, leading up to the pericenter approach, in May 2018, at about 120 AU (approximately 1,400 Schwarzschild radii) from Sgr A*. At that close distance to the black hole, Einstein's theory of general relativity (GR) predicts that S2 would show a discernible gravitational redshift in addition to the usual velocity redshift; the gravitational redshift was detected, in agreement with the GR prediction within the 10 percent measurement precision.

Assuming that general relativity is still a valid description of gravity near the event horizon, the Sagittarius A* radio emissions are not centered on the black hole, but arise from a bright spot in the region around the black hole, close to the event horizon, possibly in the accretion disc, or a relativistic jet of material ejected from the disc. If the apparent position of Sagittarius A* were exactly centered on the black hole, it would be possible to see it magnified beyond its size, because of gravitational lensing of the black hole. According to general relativity, this would result in a ring-like structure, which has a diameter about 5.2 times the black hole's Schwarzschild radius. For a black hole of around 4 million solar masses, this corresponds to a size of approximately 52 μas, which is consistent with the observed overall size of about 50 μas.

Recent lower resolution observations revealed that the radio source of Sagittarius A* is symmetrical. Simulations of alternative theories of gravity depict results that may be difficult to distinguish from GR. However, a 2018 paper predicts an image of Sagittarius A* that is in agreement with recent observations; in particular, it explains the small angular size and the symmetrical morphology of the source.

The mass of Sagittarius A* has been estimated in two different ways:

1. Two groups—in Germany and the U.S.—monitored the orbits of individual stars very near to the black hole and used Kepler's laws to infer the enclosed mass. The German group found a mass of 4.31±0.38 million solar masses, whereas the American group found 3.7±0.2 million solar masses. Given that this mass is confined inside a 44-million-kilometre-diameter sphere, this yields a density ten times higher than previous estimates.
2. More recently, measurement of the proper motions of a sample of several thousand stars within approximately one parsec from the black hole, combined with a statistical technique, has yielded both an estimate of the black hole's mass at 3.6+0.2
   −0.4×10⁶ M_☉, plus a distributed mass in the central parsec amounting to (1±0.5)×10⁶ M_☉. The latter is thought to be composed of stars and stellar remnants.

The comparatively small mass of this supermassive black hole, along with the low luminosity of the radio and infrared emission lines, imply that the Milky Way is not a Seyfert galaxy.

Ultimately, what is seen is not the black hole itself, but observations that are consistent only if there is a black hole present near Sgr A*. In the case of such a black hole, the observed radio and infrared energy emanates from gas and dust heated to millions of degrees while falling into the black hole. The black hole itself is thought to emit only Hawking radiation at a negligible temperature, on the order of 10⁻¹⁴ kelvin.

Magnetar — SGR J1745-2900
Magnetar found very close to the supermassive black hole, Sagittarius A*, at the center of the Milky Way galaxy

The European Space Agency's gamma-ray observatory INTEGRAL observed gamma rays interacting with the nearby giant molecular cloud Sagittarius B2, causing X-ray emission from the cloud. The total luminosity from this outburst (L≈1,5×10³⁹ erg/s) is estimated to be a million times stronger than the current output from Sgr A* and is comparable with a typical active galactic nucleus. In 2011 this conclusion was supported by Japanese astronomers observing the Milky Way's center with the Suzaku satellite.

In July 2019, astronomers reported finding a star, S5-HVS1, traveling 1,755 km/s (3,930,000 mph). The star is in the Grus (or Crane) constellation in the southern sky, and about 29,000 light-years from Earth, and may have been propelled out of the Milky Way galaxy after interacting with Sagittarius A*, the supermassive black hole at the center of the galaxy.

Orbiting stars

Inferred orbits of 6 stars around supermassive black hole candidate Sagittarius A* at the Milky Way's center

Inferred orbits of stars around supermassive black hole candidate Sagittarius A* at the Milky Way's center according to Gillessen et al. 2017, with the exception of S2 which is from GRAVITY 2019, S62 which is from Peißker et al. Jan 2020, and S4711 up to S4715, which are also from Peißker et al, Aug 2020.

Here id1 is the star's name in the Gillessen catalog and id2 in the catalog of the University of California, Los Angeles. a, e, i, Ω and ω are standard orbital elements, with a measured in arcseconds. Tp is the epoch of pericenter passage, P is the orbital period in years and Kmag is the K-band apparent magnitude of the star. q and v are the pericenter distance in AU and pericenter speed in percent of the speed of light, and Δ indicates the standard deviation of the associated quantities.

Until August 11, 2020, S62 was the record holder for the closest approach to Sagittarius A*, approaching to a distance of only 16 astronomical units (2400 million km), (this is less than the average distance between Uranus and the Sun). The star therefore passes only about 215 times the Schwarzschild radius of SgrA* (the Schwarzschild radius of SgrA* is approximately 0.08 AU, or 12 million km). At this point it reaches about 21,000 km/s, or ~7% the speed of light, making it the fastest known star. With an orbital period of 9.9 years it also has the smallest orbit of the stars orbiting SgrA*.

In August 2020, S4714 took the record for closest approach to Sgr A*. It has an extreme orbital eccentricity of 0.985 and the closest approach to Sgr A* is just 1900 million km. It then moves with a speed of 24,000 km per second (~8% the speed of light). However its orbital period lasts about 12 years, and its farthest distance to the galactic center is ~250 billion km.

S4711 is a blue B-type star ~150 million years old. Its closest approach to SgrA* is 21500 million kilometres, but its mean distance is shorter than that of S4714. Its orbital period is just 7.6 years.

Because they are so close to a supermassive black hole these stars are candidates for 'squeezars', stars squeezed by gravitational forces.

id1	id2	a	Δa	e	Δe	i (°)	Δi	Ω (°)	ΔΩ	ω (°)	Δω	Tp (yr)	ΔTp	P (yr)	ΔP	Kmag	q (AU)	Δq	v (%c)	Δv
S1	S0-1	0.5950	0.0240	0.5560	0.0180	119.14	0.21	342.04	0.32	122.30	1.40	2001.800	0.150	166.0	5.8	14.70	2160.7	6.7	0.55	0.03
S2	S0-2	0.1251	0.0001	0.8843	0.0001	133.91	0.05	228.07	0.04	66.25	0.04	2018.379	0.001	16.1	0.0	13.95	118.4	0.2	2.56	0.00
S4	S0-3	0.3570	0.0037	0.3905	0.0059	80.33	0.08	258.84	0.07	290.80	1.50	1957.400	1.200	77.0	1.0	14.40	1779.7	25.1	0.57	0.01
S6	S0-7	0.6574	0.0006	0.8400	0.0003	87.24	0.06	85.07	0.12	116.23	0.07	2108.610	0.030	192.0	0.2	15.40	860.3	4.4	0.94	0.00
S8	S0-4	0.4047	0.0014	0.8031	0.0075	74.37	0.30	315.43	0.19	346.70	0.41	1983.640	0.240	92.9	0.4	14.50	651.7	22.5	1.07	0.01
S9	S0-5	0.2724	0.0041	0.6440	0.0200	82.41	0.24	156.60	0.10	150.60	1.00	1976.710	0.920	51.3	0.7	15.10	793.2	36.9	0.93	0.02
S12	S0-19	0.2987	0.0018	0.8883	0.0017	33.56	0.49	230.10	1.80	317.90	1.50	1995.590	0.040	58.9	0.2	15.50	272.9	2.0	1.69	0.01
S13	S0-20	0.2641	0.0016	0.4250	0.0023	24.70	0.48	74.50	1.70	245.20	2.40	2004.860	0.040	49.0	0.1	15.80	1242.0	2.4	0.69	0.01
S14	S0-16	0.2863	0.0036	0.9761	0.0037	100.59	0.87	226.38	0.64	334.59	0.87	2000.120	0.060	55.3	0.5	15.70	56.0	3.8	3.83	0.06
S17		0.3559	0.0096	0.3970	0.0110	96.83	0.11	191.62	0.21	326.00	1.90	1991.190	0.410	76.6	1.0	15.30	1755.3	16.4	0.57	0.02
S18	S0-18	0.2379	0.0015	0.4710	0.0120	110.67	0.18	49.11	0.18	349.46	0.66	1993.860	0.160	41.9	0.2	16.70	1029.3	3.8	0.77	0.01
S19	S0-28	0.5200	0.0940	0.7500	0.0430	71.96	0.35	344.60	0.62	155.20	2.30	2005.390	0.160	135.0	14.0	16.00	1063.3	4.5	0.83	0.20
S21		0.2190	0.0017	0.7640	0.0140	58.80	1.00	259.64	0.62	166.40	1.10	2027.400	0.170	37.0	0.3	16.90	422.7	3.6	1.32	0.02
S22		1.3100	0.2800	0.4490	0.0880	105.76	0.95	291.70	1.40	95.00	20.00	1996.900	10.200	540.0	63.0	16.60	5903.7	9.7	0.32	0.10
S23		0.2530	0.0120	0.5600	0.1400	48.00	7.10	249.00	13.00	39.00	6.70	2024.700	3.700	45.8	1.6	17.80	910.5	1.6	0.85	0.06
S24	S0-26	0.9440	0.0480	0.8970	0.0049	103.67	0.42	7.93	0.37	290.00	15.00	2024.500	0.030	331.0	16.0	15.60	795.3	30.8	0.99	0.07
S29		0.4280	0.0190	0.7280	0.0520	105.80	1.70	161.96	0.80	346.50	5.90	2025.960	0.940	101.0	2.0	16.70	952.2	67.4	0.87	0.05
S31	S0-8	0.4490	0.0100	0.5497	0.0025	109.03	0.27	137.16	0.30	308.00	3.00	2018.070	0.140	108.0	1.2	15.70	1653.7	14.6	0.63	0.02
S33	S0-33	0.6570	0.0260	0.6080	0.0640	60.50	2.50	100.10	5.50	303.70	1.60	1928.000	12.000	192.0	5.2	16.00	2106.5	179.7	0.56	0.03
S38	S0-38	0.1416	0.0002	0.8201	0.0007	171.10	2.10	101.06	0.24	17.99	0.25	2003.190	0.010	19.2	0.0	17.00	208.4	1.5	1.91	0.01
S39		0.3700	0.0150	0.9236	0.0021	89.36	0.73	159.03	0.10	23.30	3.80	2000.060	0.060	81.1	1.5	16.80	231.2	3.3	1.86	0.09
S42		0.9500	0.1800	0.5670	0.0830	67.16	0.66	196.14	0.75	35.80	3.20	2008.240	0.750	335.0	58.0	17.50	3364.4	24.8	0.44	0.13
S54		1.2000	0.8700	0.8930	0.0780	62.20	1.40	288.35	0.70	140.80	2.30	2004.460	0.070	477.0	199.0	17.50	1050.2	1.9	0.86	0.78
S55	S0-102	0.1078	0.0010	0.7209	0.0077	150.10	2.20	325.50	4.00	331.50	3.90	2009.340	0.040	12.8	0.1	17.50	246.1	4.1	1.70	0.02
S60		0.3877	0.0070	0.7179	0.0051	126.87	0.30	170.54	0.85	29.37	0.29	2023.890	0.090	87.1	1.4	16.30	894.5	1.7	0.89	0.02
S62		0.0905	0.0001	0.9760	0.0020	72.76	4.58	122.61	0.57	42.62	0.40	2003.330	0.010	9.9	0.0	16.10	16.4	1.5	7.03	0.04
S66	S1-2	1.5020	0.0950	0.1280	0.0430	128.50	1.60	92.30	3.20	134.00	17.00	1771.000	38.000	664.0	37.0	14.80	10712.4	620.5	0.21	0.02
S67	S1-3	1.1260	0.0260	0.2930	0.0570	136.00	1.10	96.50	6.40	213.50	1.60	1705.000	22.000	431.0	10.0	12.10	6511.2	360.6	0.29	0.01
S71	S0-71	0.9730	0.0400	0.8990	0.0130	74.00	1.30	35.16	0.86	337.80	4.90	1695.000	21.000	346.0	11.0	16.10	803.8	1.4	0.99	0.06
S83	S0-15	1.4900	0.1900	0.3650	0.0750	127.20	1.40	87.70	1.20	203.60	6.00	2046.800	6.300	656.0	69.0	13.60	7738.6	22.5	0.27	0.05
S85		4.6000	3.3000	0.7800	0.1500	84.78	0.29	107.36	0.43	156.30	6.80	1930.200	9.800	3580.0	2550.0	15.60	8277.1	29.6	0.30	0.33
S87	S1-12	2.7400	0.1600	0.2240	0.0270	119.54	0.87	106.32	0.99	336.10	7.70	611.000	154.000	1640.0	105.0	13.60	17390.5	2572.9	0.17	0.02
S89		1.0810	0.0550	0.6390	0.0380	87.61	0.16	238.99	0.18	126.40	4.00	1783.000	26.000	406.0	27.0	15.30	3191.8	407.2	0.46	0.04
S91		1.9170	0.0890	0.3030	0.0340	114.49	0.32	105.35	0.74	356.40	1.60	1108.000	69.000	958.0	50.0	12.20	10928.4	74.5	0.22	0.02
S96	S0-96	1.4990	0.0570	0.1740	0.0220	126.36	0.96	115.66	0.59	233.60	2.40	1646.000	16.000	662.0	29.0	10.00	10127.0	530.0	0.22	0.02
S97	S1-16	2.3200	0.4600	0.3500	0.1100	113.00	1.30	113.20	1.40	28.00	14.00	2132.000	29.000	1270.0	309.0	10.30	12333.9	305.9	0.21	0.08
S145		1.1200	0.1800	0.5000	0.2500	83.70	1.60	263.92	0.94	185.00	16.00	1808.000	58.000	426.0	71.0	17.50	4580.2	1471.2	0.37	0.10
S175		0.4140	0.0390	0.9867	0.0018	88.53	0.60	326.83	0.78	68.52	0.40	2009.510	0.010	96.2	5.0	17.50	45.0	0.8	4.27	0.47
S4711														7.6
S4712
S4713
S4714														12.0					8.0
S4715
R34		1.8100	0.1500	0.6410	0.0980	136.00	8.30	330.00	19.00	57.00	8.00	1522.000	52.000	877.0	83.0	14.00	5314.6	856.3	0.36	0.05
R44		3.9000	1.4000	0.2700	0.2700	131.00	5.20	80.50	7.10	217.00	24.00	1963.000	85.000	2730.0	1350.0	14.00	23285.6	901.5	0.15	0.11

Discovery of G2 gas cloud on an accretion course

First noticed as something unusual in images of the center of the Milky Way in 2002, the gas cloud G2, which has a mass about three times that of Earth, was confirmed to be likely on a course taking it into the accretion zone of Sgr A* in a paper published in Nature in 2012. Predictions of its orbit suggested it would make its closest approach to the black hole (a perinigricon) in early 2014, when the cloud was at a distance of just over 3,000 times the radius of the event horizon (or ≈260 AU, 36 light-hours) from the black hole. G2 has been observed to be disrupting since 2009, and was predicted by some to be completely destroyed by the encounter, which could have led to a significant brightening of X-ray and other emission from the black hole. Other astronomers suggested the gas cloud could be hiding a dim star, or a binary star merger product, which would hold it together against the tidal forces of Sgr A*, allowing the ensemble to pass by without any effect. In addition to the tidal effects on the cloud itself, it was proposed in May 2013 that, prior to its perinigricon, G2 might experience multiple close encounters with members of the black-hole and neutron-star populations thought to orbit near the Galactic Center, offering some insight to the region surrounding the supermassive black hole at the center of the Milky Way.

The average rate of accretion onto Sgr A* is unusually small for a black hole of its mass and is only detectable because it is so close to Earth. It was thought that the passage of G2 in 2013 might offer astronomers the chance to learn much more about how material accretes onto supermassive black holes. Several astronomical facilities observed this closest approach, with observations confirmed with Chandra, XMM, VLA, INTEGRAL, Swift, Fermi and requested at VLT and Keck.

Simulations of the passage were made before it happened by groups at ESO and Lawrence Livermore National Laboratory (LLNL).

As the cloud approached the black hole, Dr. Daryl Haggard said "It's exciting to have something that feels more like an experiment", and hoped that the interaction would produce effects that would provide new information and insights.

Nothing was observed during and after the closest approach of the cloud to the black hole, which was described as a lack of "fireworks" and a "flop". Astronomers from the UCLA Galactic Center Group published observations obtained on March 19 and 20, 2014, concluding that G2 was still intact (in contrast to predictions for a simple gas cloud hypothesis) and that the cloud was likely to have a central star.

An analysis published on July 21, 2014, based on observations by the ESO's Very Large Telescope in Chile, concluded alternatively that the cloud, rather than being isolated, might be a dense clump within a continuous but thinner stream of matter, and would act as a constant breeze on the disk of matter orbiting the black hole, rather than sudden gusts that would have caused high brightness as they hit, as originally expected. Supporting this hypothesis, G1, a cloud that passed near the black hole 13 years ago, had an orbit almost identical to G2, consistent with both clouds, and a gas tail thought to be trailing G2, all being denser clumps within a large single gas stream.

Professor Andrea Ghez et al. suggested in 2014 that G2 is not a gas cloud but rather a pair of binary stars that had been orbiting the black hole in tandem and merged into an extremely large star.

Sgr A* is monitored on a daily basis by the X-ray telescope of the Swift satellite.

Artist impression of the accretion of gas cloud G2 onto Sgr A*. Credit: ESO.

 

Play media

This simulation shows a gas cloud, discovered in 2011, as it passes close to the supermassive black hole at the center of the Milky Way

 

Play media

This video sequence shows the motion of the dusty cloud G2 as it closes in on, and then passes, the supermassive black hole at the center of the Milky Way

Desert greening

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Desert_greening 

 

A satellite image of the Sahara, the world's largest hot desert and third largest desert after Antarctica and the Arctic.

Desert greening is the process of man-made reclamation of deserts for ecological reasons (biodiversity), farming and forestry, but also for reclamation of natural water systems and other ecological systems that support life. The term "desert greening" is intended to apply to both cold and hot arid and semi-arid deserts (see Köppen climate classification system). It does not apply to ice capped or permafrost regions. Desert greening has the potential to help solve global water, energy, and food crises. It pertains to roughly 32 million square kilometres of land.

Methods

• Managed intensive rotational grazing
• Holistic management
• Landscaping methods to reduce evaporation, erosion, consolidation of topsoil, sandstorms, temperature and more
• Permaculture in general - harvesting runoff rainwater to grow plant communities polyculture, composting or multitrophic agriculture
• Planting trees (pioneer species) and salt-loving plants (halophytes), such as Salicornia
• Regeneration of salty, polluted, or degenerated soils
• Floodwater retention and infiltration (flood control)
• Greenhouse agriculture
• Seawater farming like done by the Seawater Foundation
• Inland mariculture 
• Prevention of overgrazing and firewood use
• Planting trees with dew and rain harvesting technology like the Groasis Waterboxx.
• Farmer-managed natural regeneration

Water

Lake Tuendae, an artificial pond at Zzyzx Desert Studies Center in the Mojave Desert

Desert greening is more or less a function of water availability. If sufficient water for irrigation is at hand, any hot, cold, sandy or rocky desert can be greened. Water can be made available through saving, reuse, rainwater harvesting, desalination, or direct use of seawater for salt-loving plants. These different paths have unique features, i.e.: conserving water is a cheap solution. Reuse of treated water and the closing of cycles is the most efficient because closed cycles stand for unlimited and sustainable supply - rainwater management is a decentralized solution and applicable for inland areas - desalination is very secure as long as the primary energy for the operation of the desalination plant is available - Direct use of seawater for seawater agriculture is the most potent, only limited by the need for pumping up the water from sea level.

A novel type of desalination is done with the Sahara Forest Project. This project uses solar stills for the generation of the freshwater. Another novel technique is cloud seeding, either by artificial means or through the action of cloud-seeding bacteria that live on vegetation (e.g. Pseudomonas syringae). Another, "atmospheric water generation" or air to water, uses dehumidification and is used by the military for potable water generation. However this technology uses 200 times more energy than desalination, making it unsuitable for large scale desert greening.

Water distribution

Once the fresh water or seawater has been attained in centralized systems it must be distributed. This can be done using dug canals or in some instances aqueducts (which are both the least attractive option since they allow much water to be evaporated), troughs (as used in the Keita Project), earthenware piping (semi-open or closed) or even underground systems i.e. qanāt.

Depending on the method of distribution of the water, it can then be provided on different methods to the plants. A costly solution (used only on pipes) is drip irrigation. Other methods are the use of wadis (basically V-shaped ponds dug in the earth) or by simply planting the trees in holes inside/over the water pipe itself. The tree's roots can then suck the water straight from the water pipe (used in qanāt, hydroponics, ...) A similar technique can be done with semi-open pipes (i.e. dug throughs in the Keita Project).

Side effects

The use of water is, however, not always without problems. Desert greening by the Helmand and Arghandab Valley Authority irrigation scheme in Afghanistan significantly reduced the water flowing from the Helmand River into Lake Hamun and this, together with drought, was cited as a key reason for the severe damage to the ecology of Lake Hamun, much of which has degenerated since 1999 from a wetland of international importance into salt flats.

Trees

A main component of desert greening is the planting of trees. Trees store water, inhibit soil erosion through wind, raise water from underlying aquifers, reduce evaporation after a rain, attract animals (and thereby fertility through feces), and they can cause more rain to fall (by temperature reduction and other effects), if the planted area is large enough.

All of the effects beneficial for desert-greening which trees offer can also be provided by buildings. Shading by buildings is an example for a passive effect, the pumping up of water from aquifers an example for an active effect achieved with buildings technology. An example for a building designed to offer all of the beneficial effects of natural forests in the desert is the IBTS Greenhouse.

Example

The soil of the Thar Desert in India remains dry for much of the year and is prone to soil erosion. High speed winds blow soil from the desert, depositing some on neighboring fertile lands, and causing shifting sand dunes within the desert, which buries fences and blocks roads and railway tracks. A permanent solution to this problem of shifting sand dunes can be provided by planting appropriate species on the dunes to prevent further shifting and planting windbreaks and shelterbelts. These solutions also provide protection from hot or cold and desiccating winds and the invasion of sand. The Rajasthan Canal system in India is the major irrigation scheme of the Thar Desert and is intended to reclaim it and to check spreading of the desert to fertile areas.

Prevention of shifting sand dunes is accomplished through plantations of Acacia tortilis near Laxmangarh town. There are few local tree species suitable for planting in the desert region and these are slow growing. The introduction of exotic tree species in the desert for plantation has become necessary. Many species of Eucalyptus, Acacia, Cassia and other genera from Israel, Australia, US, Russia, Zimbabwe, Chile, Peru, and Sudan have been tried in the Thar Desert. Acacia tortilis has proved to be the most promising species for desert greening. The jojoba is another promising species of economic value which has been found suitable for planting in these areas.

Sundrop Farms launched a greenhouse in 2016 to produce 15,000 tonnes of tomatoes using only desert soil and desalinated water piped from Spencer Gulf.

Holistic management (agriculture)

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Holistic_management_(agriculture) 

Holistic Management (from ὅλος holos, a Greek word meaning all, whole, entire, total) in agriculture is an approach to managing resources that was originally developed by Allan Savory. Holistic Management is a registered trademark of Holistic Management International.

Definition

Holistic planned grazing is similar to rotational grazing but differs in that it more explicitly recognizes and provides a framework for adapting to the four basic ecosystem processes: the water cycle, the mineral cycle including the carbon cycle, energy flow, and community dynamics (the relationship between organisms in an ecosystem), giving equal importance to livestock production and social welfare. Holistic management has been likened to "a permaculture approach to rangeland management".

Framework

The Holistic Management decision-making framework uses six key steps to guide the management of resources:

1. Define in its entirety what you are managing. No area should be treated as a single-product system. By defining the whole, people are better able to manage. This includes identifying the available resources, including money, that the manager has at his disposal.
2. Define what you want now and for the future. Set the objectives, goals and actions needed to produce the quality of life sought, and what the life-nurturing environment must be like to sustain that quality of life far into the future.
3. Watch for the earliest indicators of ecosystem health. Identify the ecosystem services that have deep impacts for people in both urban and rural environments, and find a way to easily monitor them. One of the best examples of an early indicator of a poorly functioning environment is patches of bare ground. An indicator of a better functioning environment is newly sprouting diversity of plants and a return or increase of wildlife.
4. Don't limit the management tools you use. The eight tools for managing natural resources are money/labor, human creativity, grazing, animal impact, fire, rest, living organisms and science/technology. To be successful you need to use all these tools to the best of your ability.
5. Test your decisions with questions that are designed to help ensure all your decisions are socially, environmentally and financially sound for both the short and long term.
6. Monitor proactively, before your managed system becomes more imbalanced. This way the manager can take adaptive corrective action quickly, before the ecosystem services are lost. Always assume your plan is less than perfect and use a feedback loop that includes monitoring for the earliest signs of failure, adjusting and re-planning as needed. In other words use a "canary in a coal mine" approach.

Four principles

Savory stated four key principles of Holistic Management® planned grazing, which he intended to take advantage of the symbiotic relationship between large herds of grazing animals and the grasslands that support them:

1. Nature functions as a holistic community with a mutualistic relationship between people, animals and the land. If you remove or change the behavior of any keystone species like the large grazing herds, you have an unexpected and wide-ranging negative impact on other areas of the environment.
2. It is absolutely crucial that any agricultural planning system must be flexible enough to adapt to nature’s complexity, since all environments are different and have constantly changing local conditions.
3. Animal husbandry using domestic species can be used as a substitute for lost keystone species. Thus when managed properly in a way that mimics nature, agriculture can heal the land and even benefit wildlife, while at the same time benefiting people.
4. Time and timing is the most important factor when planning land use. Not only is it crucial to understand how long to use the land for agriculture and how long to rest, it is equally important to understand exactly when and where the land is ready for that use and rest.

Beginnings

The idea of holistic planned grazing was developed in the 1960s by Allan Savory, a wildlife biologist in his native Southern Rhodesia. Setting out to understand desertification in the context of the larger environmental movement, and influenced by the work of André Voisin, he hypothesized that the spread of deserts, the loss of wildlife, and the resulting human impoverishment were related to the reduction of the natural herds of large grazing animals and, even more, the changed behavior of the few remaining herds. Savory hypothesized further that livestock could be substituted for natural herds to provide important ecosystem services like nutrient cycling. However, while livestock managers had found that rotational grazing systems can work for livestock management purposes, scientific experiments demonstrated it does not necessarily improve ecological issues such as desertification. As Savory saw it, a more comprehensive framework for the management of grassland systems — an adaptive, holistic management plan — was needed. For that reason Holistic Management has been used as a Whole Farm/Ranch Planning tool In 1984, he founded the Center for Holistic Resource Management which became Holistic Management International. 

Development

In many regions, pastoralism and communal land use are blamed for environmental degradation caused by overgrazing. After years of research and experience, Savory came to understand this assertion was often wrong, and that sometimes removing animals actually made matters worse. This concept is a variation of the trophic cascade, where humans are seen as the top level predator and the cascade follows from there.

Savory developed a management system that he claimed would improve grazing systems. Holistic planned grazing is one of a number of newer grazing management systems that aim to more closely simulate the behavior of natural herds of wildlife and have been shown to improve riparian habitats and water quality over systems that often led to land degradation, and be an effective tool to improve range condition for both livestock and wildlife.

Uses

While originally developed as a tool for range land use and restoring desertified land, the Holistic Management system can be applied to other areas with multiple complex socioeconomic and environmental factors. One such example is integrated water resources management, which promotes sector integration in development and management of water resources to ensure that water is allocated fairly between different users, maximizing economic and social welfare without compromising the sustainability of vital ecosystems. Another example is mine reclamation. A fourth use of Holistic Management® is in certain forms of no till crop production, intercropping, and permaculture. Holistic management has been acknowledged by the United States Department of Agriculture. The most comprehensive use of Holistic Management is as a Whole Farm/Ranch Planning tool which has been used successfully by farmers and ranchers. For that reason, the USDA invested six years of Beginning Farmer/Rancher Development funding to use it to train beginning women farmers and ranchers. 

Criticism

There are several claims that evidence for Holistic Management is not based in science. A paper by Richard Teague et al. claims that the different criticisms had examined rotational systems in general and not holistic planned grazing.

In 2013 the Savory Institute published a response to some of their critics. The same month Savory was a guest speaker with TED and gave a presentation titled "How to Fight Desertification and Reverse Climate Change". RealClimate.org published a piece saying that Savory's claims that his technique can bring atmospheric carbon "back to pre-industrial levels" are "simply not reasonable."

In his Ted Talk, Savory has claimed that holistic grazing could reduce carbon dioxide levels to pre-industrial levels in a span of 40 years, solving the problems caused by climate change. According to Skeptical science, "it is not possible to increase productivity, increase numbers of cattle and store carbon using any grazing strategy, never-mind Holistic Management [...] Long term studies on the effect of grazing on soil carbon storage have been done before, and the results are not promising.[...] Because of the complex nature of carbon storage in soils, increasing global temperature, risk of desertification and methane emissions from livestock, it is unlikely that Holistic Management, or any management technique, can reverse climate change."

According to a 2016 study published by the University of Uppsala, the actual rate at which improved grazing management could contribute to carbon sequestration is seven times lower than the claims made by Savory. The study concludes that holistic management cannot reverse climate change. A study by the Food and Climate Research Network in 2017 has concluded that Savory's claims about carbon sequestration are "unrealistic" and very different from those issued by peer-reviewed studies.

Awards

Savory received the 2003 Banksia International Award and in 2010 the Africa Centre for Holistic Management in Zimbabwe, Operation Hope (a "proof of concept" project using holistic management) was named the winner of the 2010 Buckminster Fuller Challenge for "recognizing initiatives which take a comprehensive, anticipatory, design approach to radically advance human well being and the health of our planet's ecosystems". In addition, numerous Holistic Management practitioners have received awards for their environmental stewardship through using Holistic Management practices. 

Religious views on the self

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Religious_views_on_the_self 

Religious views on the self vary widely. The self is a complex and core subject in many forms of spirituality. In Western psychology, the concept of self comes from Sigmund Freud, Carl Jung, and Carl Rogers where the self is the inner critic.

Some Eastern philosophies reject the self as a delusion. In Buddhist psychology, the attachment to self is an illusion that serves as the main cause of suffering and unhappiness.

Discussion

Human beings have a self—that is, they are able to look back on themselves as both subjects and objects in the universe. Ultimately, this brings questions about who we are and the nature of our own importance.

Christianity sees the self negatively, distorted through sin: 'The heart is deceitful above all things, and desperately wicked; who can know it?' (Jeremiah 17:9) Alternately, each human self or spirit is a unique creation by God. The "desperately wicked self" is the sinful self that has chosen to be "curved back upon itself", but ever with the potential of changing and (by God's grace) turning toward "'new life', opened out to love of God and neighbor".

According to psychologist James Marcia, identity comes from both political and religious views. Marcia also identified exploration and commitment as interactive parts of identity formation, which includes religious identity. Erik Erikson compared faith with doubt and found that healthy adults take heed to their spiritual side.

One description of spirituality is the self's search for "ultimate meaning" through an independent comprehension of the sacred. Spiritual identity appears when the symbolic religious and spiritual of a culture is found by individuals in the setting of their own life. There can be different types of spiritual self because it is determined on one's life and experiences. Another definition of spiritual identity is " a persistent sense of self that addresses ultimate questions about the nature, purpose, and meaning of life, resulting in behaviors that are consonant with the individual’s core values."  Another description of mind, body, soul, and spirit is a holism of one inner self being of one whole. It all combines together as one whole instead of different parts. Individuals one thoughts, one feeling, one breathing is all completed and occurs as one whole.

Bandura

Albert Bandura believed in "self-efficacy, which refers to a person's learned expectations of success." This theory states that people are bound to complete a task more effectively if they think they will succeed. If a person is more negative about their abilities the chances of them completing the task accordingly are less.

Winnicott

D. W. Winnicott was of the opinion that psychopathology was in large part generated by an overvaluation of the false self, at the expense of the true self which was linked to the individual's own creativity.

Rogers on self and self-concept

Carl Rogers' theory is that "people use the term self concept to refer to all the information and beliefs you have as an individual regarding your own nature, unique qualities, and typical behaviors."  Rogers thought that people develop through relationships with others and also in relation to themselves. An encouraging environment helps people towards this development.

Commenting on his clients' search for a real self, Rogers quoted with approval Kierkegaard's statement that "the most common despair is to be in despair at not choosing, or willing, to be oneself; but that the deepest form of despair is to choose 'to be another than himself'. On the other hand, 'to will to be that self which one truly is, is indeed the opposite of despair'".

The observing self

The "Visible" self is mainly dependent on a subjective view, that is, as viewed from the specific self. For example: looking in the mirror, we perceive the reflection to be our true "self"....

The witnessing self

Ken Wilber describes the Witnessing (or Observing) Self in the following terms:

"This observing Self is usually called the Self with a capital S, or the Witness, or pure Presence, or pure Awareness, or Consciousness as such, and this Self as transparent Witness is a direct ray of the living Divine. The ultimate "I AM" is Christ, is Buddha, is Emptiness itself: such is the startling testimony of the world's great mystics and sages." 

He adds that the self is not an Emergent, but an aspect present from the start as the basic form of awareness, but which becomes increasingly obvious and self-aware "as growth and transcendence matures." As Depth increases, consciousness shines forth more noticeably, until:

"shed[ding] its lesser identification with both the body and the mind ... in each case from matter to body to mind to Spirit... consciousness or the observing Self sheds an exclusive identity with a lesser and shallower dimension, and opens up to deeper and higher and wider occasions, until it opens up to its own ultimate ground in Spirit itself. And the stages of transpersonal growth and development are basically the stages of following this Observing Self to its ultimate abode, which is pure Spirit or pure Emptiness, the ground, path and fruition of the entire display." 

In a similar vein, Evelyn Underhill states:

It is clear that under ordinary conditions, and save for sudden gusts of "Transcendental Feeling" induced by some saving madness such as Religion, Art, or Love, the superficial self knows nothing of the attitude of this silent watcher—this "Dweller in the Innermost"—towards the incoming messages of the external world: nor of the activities which they awake in it. Concentrated on the sense-world, and the messages she receives from it, she knows nothing of the relations which exist between this subject and the unattainable Object of all thought. But by a deliberate inattention to the messages of the senses, such as that which is induced by contemplation, the mystic can bring the ground of the soul, the seat of "Transcendental Feeling," within the area of consciousness: making it amenable to the activity of the will. Thus becoming unaware of his usual and largely fictitious "external world," another and more substantial set of perceptions, which never have their chance under normal conditions, rise to the surface. Sometimes these unite with the normal reasoning faculties. More often, they supersede them. Some such exchange, such "losing to find," appears to be necessary, if man's transcendental powers are to have their full chance.

Ātman (Buddhism)

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/%C4%80tman_(Buddhism)

Ātman (/ˈɑːtmən/), attā or attan in Buddhism is the concept of self, and is found in Buddhist literature's discussion of the concept of non-self (Anatta).

Most Buddhist traditions and texts reject the premise of a permanent, unchanging atman (self, soul).  However, some Buddhist schools, sutras and tantras present the notion of an atman or permanent "Self", although mostly referring to an Absolute and not to a personal self.

Etymology

Cognates (Sanskrit: आत्मन्) ātman, (Pāli) atta, Old English æthm, German Atem, and Greek atmo- derive from the Indo-European root *ēt-men (breath). The word means "essence, breath, soul."

Ātman and atta refer to a person's "true self", a person's permanent self, absolute within, the "thinker of thoughts, feeler of sensations" separate from and beyond the changing phenomenal world. The term Ātman is synonymous with Tuma, Atuma and Attan in early Buddhist literature, state Rhys David and William Stede, all in the sense of "self, soul". The Atman and Atta are related, in Buddhist canons, to terms such as Niratta (Nir+attan, soulless) and Attaniya (belonging to the soul, having a soul, of the nature of soul).

Early Buddhism

"Atman" in early Buddhism appears as "all dhammas are not-Self (an-atta)", where atta (atman) refers to a metaphysical Self, states Peter Harvey, that is a "permanent, substantial, autonomous self or I". This concept refers to the pre-Buddhist Upanishads of Hinduism, where a person is viewed as having a lower self (impermanent body, personality) and a Higher or Greater Self (real permanent Self, soul, atman, atta). The early Buddhist literature explores the validity of the Upanishadic concepts of self and Self, then asserts that every living being has an impermanent self but there is no real Higher Self. The Nikaya texts of Buddhism deny that there is anything called Ātman that is the substantial absolute or essence of a living being, an idea that distinguishes Buddhism from the Brahmanical (proto-Hindu) traditions.

The Buddha argued that no permanent, unchanging "self" can be found. In Buddha's view, states Wayman, "eso me atta, or this is my self, is to be in the grip of wrong view". All conditioned phenomena are subject to change, and therefore can't be taken to be an unchanging "self". Instead, the Buddha explains the perceived continuity of the human personality by describing it as composed of five skandhas, without a permanent entity (Self, soul).

Pudgalavada

Of the early Indian Buddhist schools, only the Pudgalavada-school diverged from this basic teaching. The Pudgalavādins asserted that, while there is no ātman, there is a pudgala or "person", which is neither the same as nor different from the skandhas.

Buddha-nature

Buddha-nature is a central notion of east-Asian (Chinese) Mahayana thought. It refers to several related terms, most notably Tathāgatagarbha and Buddha-dhātu. Tathāgatagarbha means "the womb of the thus-gone" (c.f. enlightened one), while Buddha-dhātu literally means "Buddha-realm" or "Buddha-substrate". Several key texts refer to the tathāgatagarbha or Buddha-dhātu as "atman", self or essence, though those texts also contain warnings against a literal interpretation. Several scholars have noted similarities between tathāgatagarbha texts and the substantial monism found in the atman/Brahman tradition.

The Tathagatagarbha doctrine, at its earliest, probably appeared about the later part of the 3rd century CE, and is verifiable in Chinese translations of 1st millennium CE.

Mahāyāna Mahāparinirvāṇa Sūtra

In contrast to the madhyamika-tradition, the Mahāparinirvāṇa Sūtra uses "positive language" to denote "absolute reality". According to Paul Williams, the Mahāyāna Mahāparinirvāṇa Sūtra teaches an underlying essence, "Self", or "atman". This "true Self" is the Buddha-nature (Tathagatagarbha), which is present in all sentient beings, and realized by the awakened ones. Most scholars consider the Tathagatagarbha doctrine in Mahāparinirvāṇa Sūtra asserting an 'essential nature' in every living being is equivalent to 'Self', and it contradicts the Anatta doctrines in a vast majority of Buddhist texts, leading scholars to posit that the Tathagatagarbha Sutras were written to promote Buddhism to non-Buddhists.

According to Sallie B. King, the Mahāyāna Mahāparinirvāṇa Sūtra does not represent a major innovation. Its most important innovation is the linking of the term buddhadhatu with tathagatagarbha. According to King, the sutra is rather unsystematic, which made it "a fruitful one for later students and commentators, who were obliged to create their own order and bring it to the text". The sutra speaks about Buddha-nature in so many different ways, that Chinese scholars created a list of types of Buddha-nature that could be found in the text. One of those statements is:

Even though he has said that all phenomena [dharmas] are devoid of the Self, it is not that they are completely/ truly devoid of the Self. What is this Self ? Any phenomenon [dharma] that is true [satya], real [tattva], eternal [nitya], sovereign/ autonomous/ self-governing [aisvarya], and whose ground/ foundation is unchanging [asraya-aviparinama], is termed ’the Self ’ [atman].

In the Mahāparinirvāṇa Sūtra the Buddha also speaks of the "affirmative attributes" of nirvana, "the Eternal, Bliss, the Self and the Pure." The Mahāyāna Mahāparinirvāṇa Sūtra explains:

The Self ’ signifies the Buddha; ’the Eternal’ signifies the Dharmakaya; ’Bliss’ signifies Nirvana, and ’the Pure’ signifies Dharma.

Edward Conze connotatively links the term tathagata itself (the designation which the Buddha applied to himself) with the notion of a real, true self:

Just as tathata designates true reality in general, so the word which developed into Tathagata designated the true self, the true reality within man.

It is possible, states Johannes Bronkhorst, that "original Buddhism did not deny the existence of the soul [Ātman, Attan]", even though a firm Buddhist tradition has maintained that the Buddha avoided talking about the soul or even denied it existence. While there may be ambivalence on the existence or non-existence of self in early Buddhist literature, adds Bronkhorst, it is clear from these texts that seeking self-knowledge is not the Buddhist path for liberation, and turning away from self-knowledge is. This is a reverse position to the Vedic traditions which recognized the knowledge of the self as "the principal means to achieving liberation".

"Self" as a teaching method

According to Paul Wiliams, the Mahaparinirvana Sutra uses the term "Self" in order to win over non-Buddhist ascetics. He quotes from the sutra:

The Buddha-nature is in fact not the self. For the sake of [guiding] sentient beings, I describe it as the self.

In the later Lankāvatāra Sūtra it is said that the tathāgatagarbha might be mistaken for a self, which it is not.

Ratnagotravibhāga

The Ratnagotravibhāga (also known as Uttaratantra), another text composed in the first half of 1st millennium CE and translated into Chinese in 511 CE, points out that the teaching of the Tathagatagarbha doctrine is intended to win sentient beings over to abandoning "self-love" (atma-sneha) – considered to be a moral defect in Buddhism. The 6th-century Chinese Tathagatagarbha translation states that "Buddha has shiwo (True Self) which is beyond being and nonbeing". However, the Ratnagotravibhāga asserts that the "Self" implied in Tathagatagarbha doctrine is actually "not-Self".

Current disputes

The dispute about "self" and "not-self" doctrines has continued throughout the history of Buddhism. According to Johannes Bronkhorst, it is possible that "original Buddhism did not deny the existence of the soul", even though a firm Buddhist tradition has maintained that the Buddha avoided talking about the soul or even denied its existence. French religion writer André Migot also states that original Buddhism may not have taught a complete absence of self, pointing to evidence presented by Buddhist and Pali scholars Jean Przyluski and Caroline Rhys Davids that early Buddhism generally believed in a self, making Buddhist schools that admit an existence of a "self" not heretical, but conservative, adhering to ancient beliefs. While there may be ambivalence on the existence or non-existence of self in early Buddhist literature, Bronkhorst suggests that these texts clearly indicate that the Buddhist path of liberation consists not in seeking self-knowledge, but in turning away from what might erroneously be regarded as the self. This is a reverse position to the Vedic traditions which recognized the knowledge of the self as "the principal means to achieving liberation."

In Thai Theravada Buddhism, for example, states Paul Williams, some modern era Buddhist scholars have claimed that "nirvana is indeed the true Self", while other Thai Buddhists disagree. For instance, the Dhammakaya Movement in Thailand teaches that it is erroneous to subsume nirvana under the rubric of anatta (non-self); instead, nirvana is taught to be the "true self" or dhammakaya. The Dhammakaya Movement teaching that nirvana is atta, or true self, was criticized as heretical in Buddhism in 1994 by Ven. Payutto, a well-known scholar monk, who stated that 'Buddha taught nibbana as being non-self". The abbot of one major temple in the Dhammakaya Movement, Luang Por Sermchai of Wat Luang Por Sodh Dhammakayaram, argues that it tends to be scholars who hold the view of absolute non-self, rather than Buddhist meditation practitioners. He points to the experiences of prominent forest hermit monks such as Luang Pu Sodh and Ajahn Mun to support the notion of a "true self". Similar interpretations on the "true self" were put forth earlier by the 12th Supreme Patriarch of Thailand in 1939. According to Williams, the Supreme Patriarch's interpretation echoes the tathāgatagarbha sutras.

Several notable teachers of the Thai Forest Tradition have also described ideas in contrast to absolute non-self. Ajahn Maha Bua, a well known meditation master, described the citta (mind) as being an indestructible reality that does not fall under anattā. He has stated that not-self is merely a perception that is used to pry one away from infatuation with the concept of a self, and that once this infatuation is gone the idea of not-self must be dropped as well. American monk Thanissaro Bhikkhu of the Thai Forest Tradition describes the Buddha's statements on non-self as a path to awakening rather than a universal truth. Thanissaro Bhikkhu states that the Buddha intentionally set the question of whether or not there is a self aside as a useless question, and that clinging to the idea that there is no self at all would actually prevent enlightenment. Bhikkhu Bodhi authored a rejoinder to Thanissaro, claiming that "The reason the teaching of anatta can serve as a strategy of liberation is precisely because it serves to rectify a misconception about the nature of being, hence an ontological error."

Buddhist scholars Richard Gombrich and Alexander Wynne argue that the Buddha's descriptions of non-self in early Buddhist texts do not deny that there is a self. Gethin claims that anatta is often mistranslated as meaning "not having a self", but in reality meant "not the self". Wynne claims early Buddhist texts such as the Anattalakkhana Sutta do not deny that there is a self, stating that the five aggregates that are described as not self are not descriptions of a human being but descriptions of the human experience. Wynne and Gombrich both argue that the Buddha's statements on anattā were originally a "not-self" teaching that developed into a "no-self" teaching in later Buddhist thought. Thanissaro Bhikkhu points to the Ananda Sutta (SN 44.10), where the Buddha stays silent when asked whether there is a 'self' or not, as a major cause of the dispute.