~ Pulsating variable stars? ~ Cephei, Measuring the universe, The KELT & The RTC ~

This post has been made for the night mode of steemit ©. Eye Care

1 - NASA's Hubble Space Telescope - Cepheid Variable Star V1 in M31

The Pulsating variable stars are fundamental to understand the enormous distances that occur in the vast universe. Today we use the period-luminosity relationship as the rosetta stone of the "scale of distance" to calculate the distances of galaxies.

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Measuring the universe a small view of history…

In 1784 an amateur astronomer John Goodricke had discovered identical behavior in the Delta Cephei star of the constellation Cepheus. In his honor, this type of variable stars receives the name of Cepheids (although, the first Cepheid observed was not Delta Cephei, but the star Eta Aquilae, discovered a few months earlier by Edward Piggot.

Thus in 1912 Henrietta S. Leavitt managed to establish the distances between the stars and the Earth. Although the publication was signed by his boss, Edward C. Pickering.

Quote:
”A straight line can easily be drawn between each of the two series of points that correspond to the maximums and the minimums, thus showing that there is a simple relationship between the brightness of the variables and their periods.”
”Since the variables are probably almost the same distance from Earth, their periods are apparently associated with their actual light emission, as determined by their mass, density and surface brightness.”
Periods of 25 Variable Stars in the Small Magellanic Cloud, Harvard College Observatory Circular 173 (1912).

Despite being deafened by an illness after graduating. His work studying Small Magellanic Clouds ( Nubeculae Magellani)
was transcendental for Astronomy. And rarely in the history of science an article of just three pages has been so profitable for human knowledge…

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Cephei.

2 - Spitzer Space Telescope - Image credit: NASA/JPL-Caltech ©

This is one of the most important types of variable stars: yellow giants that experience pulsations with very regular periods. Their periods go from one day to several weeks. Cepheids are important because they serve as a standard. Its brightness is directly related to the period of variation, with a small dependence on its metallicity. The longer the period of pulsation, the brighter the star will be. Once this period-luminosity relation is calibrated, the brightness of a Cepheid whose period is known can be determined. The distance to which it is located can also be easily known from its apparent brightness. The observation of the Cepheid variables is very important to determine the distance of the Local Group galaxies and even more… Since a few years ago we have powerful tools that allow us to have much more precision among those found ...

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Kilodegree Extremely Little Telescope (KELT)

3 - The KELT-North survey telescope is located at Winer Observatory in Arizona

The KELT is composed of two robotic optical telescopes each in one hemisphere. The north is in Arizona USA and the south near Sutherland, SA. The north began to be used in the year 2005 and the South in the year 2009. The main objective of this telescope duo is to discover transit exoplanets orbiting stars of different magnitudes. As their name suggests these telescopes are very small they only have 4.2 centimeters of aperture.

Robotically Controlled Telescope

( RCT )

4 - The RCT Consortium (KPNO) ®

The RCT is a Robotic optical telescope
that belongs to consortium of three universities in the United States that operate the telescope from the south of the country located at Kitt Peak National Observatory (KPNO) in southern Arizona. This robotic telescope can be used in a fully automatic mode. This allows the members of the three universities to study the results while the RCT continues to carry out its work. This telescope is larger than the previous ones measuring 1.3 meters.

Period Variations for the Cepheid VZ Cyg.

Thanks to these tools, the Astrophysicists of the Lehigh University have been able to measure with great accuracy the Cepheid VZ Cyg period variations.

However, numerous Cepheids are known to undergo period variations. Monitoring, refining, and understanding these period variations allows us to better determine the parameters of the Cepheids themselves and of the instability strip in which they reside, and to test models of stellar evolution. VZ Cyg, a classical Cepheid pulsating at ∼4.864 days, has been observed for over 100 years.
This higher rate could be due to an apparent long-term (P ≈ 26.5 yr) cyclic period variation. The possible interpretations of this single Cepheid's complex period variations underscore both the need to regularly monitor pulsating variables, and the important benefits that photometric surveys such as KELT can have on the field.
arXiv:1711.03017 [astro-ph.SR]

Thanks to the technological improvements we have gone from the endless days of observation and calculation have given way to autonomous robotic Telescopes improving the accuracy and the verification of new measurements …

References.

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Biography
http://astrogea.org/surveys/Henrietta_Leavitt.htm

https://www.britannica.com/biography/Henrietta-Swan-Leavitt

Q1
http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1912HarCi.173....1L&link_type=ARTICLE&db_key=AST&high=

Q2
https://arxiv.org/pdf/1711.03017

1
https://www.nasa.gov/mission_pages/hubble/science/star-v1.html

2
https://www.nasa.gov/mission_pages/hubble/science/star-v1.html

3
http://www.astronomy.ohio-state.edu/keltnorth/Telescope.html

4
https://www1.villanova.edu/villanova/artsci/astronomy/facilities/rct.html

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~ L1 & SOHO ~

https://steemit.com/space/@teks/the-mysterious-regions-of-space-that-have-their-own-rules

~ Hypervelocity stars, Gaia mission & L2 ~

https://steemit.com/space/@teks/stars-through-the-galaxy-hypervelocity-stars-gaia-mission-and-l2

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Let's take care of the pale blue dot

Enjoy your day. Enjoy your life.

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Gift-thanks to @stellabelle