Standard-candles astronomy

This is a Hubble Space Telescope Image of NGC 4414. Credit: Hubble Heritage Team (AURA/STScI/NASA).

Standard-candles astronomy is the astronomical effort to find, study and develop standard-candle candidates for use as standard candles.

Astronomy

"In 1995, the majestic spiral galaxy NGC 4414 was imaged by the Hubble Space Telescope as part of the HST Key Project on the Extragalactic Distance Scale. [The galaxy was] "observed ... on 13 different occasions over the course of two months."[1]

"Images were obtained with Hubble's Wide Field Planetary Camera 2 (WFPC2) through three different color filters."[1]

"Based on [...] careful brightness measurements of variable stars in NGC 4414, [...] an accurate determination of the distance to the galaxy [was made]."[1]

"The resulting distance to NGC 4414, 19.1 megaparsecs or about 60 million light-years, along with similarly determined distances to other nearby galaxies, contributes to astronomers' overall knowledge of the rate of expansion of the universe. The Hubble constant (H0) is the ratio of how fast galaxies are moving away from us to their distance from us. This astronomical value is used to determine distances, sizes, and the intrinsic luminosities for many objects in our universe, and the age of the universe itself."[1]

"Due to the large size of the galaxy compared to the WFPC2 detectors, only half of the galaxy observed was visible in the datasets collected by the Key Project astronomers in 1995. In 1999, the Hubble Heritage Team revisited NGC 4414 and completed its portrait by observing the other half with the same filters as were used in 1995. The end result is a stunning full-color look at the entire dusty spiral galaxy. The new Hubble picture shows that the central regions of this galaxy, as is typical of most spirals, contain primarily older, yellow and red stars. The outer spiral arms are considerably bluer due to ongoing formation of young, blue stars, the brightest of which can be seen individually at the high resolution provided by the Hubble camera. The arms are also very rich in clouds of interstellar dust, seen as dark patches and streaks silhouetted against the starlight."[1]

Betelgeuse

The star Betelgeuse may still be too far away for visual trigonometric parallax. Standard candles have probably been used to estimate its distance from the Sun. Estimates from visual trigonometric parallax may be available to evaluate the historical accuracy of standard stellar candles.

In 1977 the first direct angular-diameter observations of 119 Tauri were made.[2]

As a spectral type M2.2 Iab information is inferred about Betelgeuse (a type M2.2 Iab) from the occultation measurements of 119 Tauri.[2] The occultations were on January 31, and April 23, 1977.

The spectral type of 119 Tau has been constant since 1940.[2]

In 1977, 119 Tauri (CE Tau) was a spectral type M2.2 Iab, with a spectral range of M2.0-M2.4 Iab-Ib.[2]

In 1977, Betelgeuse was a spectral type M2.0 Iab-, with a range of M1.3-M2.8 Iab-Ib.[2]

For α Sco in 1980 it was M1.1 Iab with a range of M0.7-M1.5 Iab-Ib

As of 2014, 119 Tauri is an M2Iab according to SIMBAD.

As of 2014, Betelgeuse (alf Ori) is an M2Iab according to SIMBAD.

"The spectral type of α Ori varies roughly with the 5.8 yr period and epoch [...] for brightness, radial velocity, and possible angular-diameter variations. Recently, α Ori has shown the latest spectral type between 1973 and 1975 and again in 1980 January-February with a spectral type of M2.8 Iab-. Its spectral type was about M1.5 around 1969-1971 and again around 1977-1978. By 1982 or 1983, α Ori should again have a spectral type of about M1.5."[2]

In 1977, apparently α Scorpii (Antares) was an M2.2 Iab, but in 2014 it is an M1.5Iab-b.

The standard candle being used in 1977 for spectral region K5-M4 is the CN (cyanide) index from the CN absorption in selected bands.[2]

The apparent magnitude needed for calculating an object's distance in pc is obtained using a photospheric magnitude received for the 1.04 µm flux peak, I(104) in early-M stars.[2]

Near-infrared "photometry on the narrow-band eight-color system [...] has been obtained for these stars. The mean [CN] indices and spectral types derived from photometry of the three supergiants are"[2]

  1. 119 Tau, CN index = 18 ± 2, I(104) mag = +0.84 ± 0.03, MV = -5.2 (-4.8 to -5.6), distance = 417 pc,
  2. α Ori, CN index = 18 ± 3, I(104) mag = -2.68 ± 0.03, MV = -5.2, (-4.5 to -5.8), distance = 96 pc, and
  3. α Sco, CN index = 19 ± 3, I(104) mag = -2.28 ± 0.02, MV = -5.5, (-4.5 to -5.9), distance = 107 pc.

"The distance to α Ori is about half the value, 200 pc, that is almost universally used in the literature."[2]

"The direct evidence for a distance of 200 pc [to Betelgeuse] is a trigonometric parallax of 0.005, which is 10 times smaller than the expected error of measurement [0.005 ± 0.05 mas]."[2]

In 1977 using the absorption spectrum of cyanide believed to be applicable for the spectral region K5-M4 to produce a CN index and the relationship between apparent magnitude and absolute magnitude, a distance of 96 pc was estimated for Betelgeuse. Parallax measurements at that time estimated a distance of 200 pc, but the error was 10 times greater than the value derived.[2]

A parallax measurement by the satellite Hipparcos indicated a distance of 197 ± 45 pc published in 2008.

While post 1980 adjustments were made to increase the estimated distance of Betelgeuse, the initial discrepancy is quite large, at least a factor of 2 using a standard candle.

In 1977, the distance to Betelgeuse estimated by various standard candles suggested 200 pc, "almost universally used in the literature."[2]

Research

Hypothesis:

  1. Many of the standard candles have such a wide range of sizes that distance estimates are at best only good to an order of magnitude.

Control groups

This is an image of a Lewis rat. Credit: Charles River Laboratories.

The findings demonstrate a statistically systematic change from the status quo or the control group.

“In the design of experiments, treatments [or special properties or characteristics] are applied to [or observed in] experimental units in the treatment group(s).[3] In comparative experiments, members of the complementary group, the control group, receive either no treatment or a standard treatment.[4]"[5]

Proof of concept

Def. a “short and/or incomplete realization of a certain method or idea to demonstrate its feasibility"[6] is called a proof of concept.

Def. evidence that demonstrates that a concept is possible is called proof of concept.

The proof-of-concept structure consists of

  1. background,
  2. procedures,
  3. findings, and
  4. interpretation.[7]

See also

References

  1. 1 2 3 4 5 Wendy Freedman (1999). "MAGNIFICENT DETAILS IN A DUSTY SPIRAL GALAXY". Greenbelt, Maryland USA: NASA Goddard Space Flight Center. Retrieved 2014-10-28.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 Nathaniel M. White (December 1, 1980). "The Occultation of 119 Tauri and the Effective Temperatures of Three M Supergiants". The Astrophysical Journal 242 (12): 646-56. doi:10.1086/158501. http://articles.adsabs.harvard.edu/full/1980ApJ...242..646W. Retrieved 2014-03-26.
  3. ↑ Klaus Hinkelmann, Oscar Kempthorne (2008). Design and Analysis of Experiments, Volume I: Introduction to Experimental Design (2nd ed.). Wiley. ISBN 978-0-471-72756-9. http://books.google.com/?id=T3wWj2kVYZgC&printsec=frontcover.
  4. ↑ R. A. Bailey (2008). Design of comparative experiments. Cambridge University Press. ISBN 978-0-521-68357-9. http://www.cambridge.org/uk/catalogue/catalogue.asp?isbn=9780521683579.
  5. ↑ "Treatment and control groups, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. May 18, 2012. Retrieved 2012-05-31.
  6. ↑ "proof of concept, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. November 10, 2012. Retrieved 2013-01-13.
  7. ↑ Ginger Lehrman and Ian B Hogue, Sarah Palmer, Cheryl Jennings, Celsa A Spina, Ann Wiegand, Alan L Landay, Robert W Coombs, Douglas D Richman, John W Mellors, John M Coffin, Ronald J Bosch, David M Margolis (August 13, 2005). "Depletion of latent HIV-1 infection in vivo: a proof-of-concept study". Lancet 366 (9485): 549-55. doi:10.1016/S0140-6736(05)67098-5. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1894952/. Retrieved 2012-05-09.

External links

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