M31-V1 Hubble's variable star (Jesper Sørensen)

M31-V1 Hubble's variable star

M31-V1

In 1908 Henrietta Swan Laevitt discovered that there was a relationship between the period and the luminosity of Cepheid variable stars. Thus knowing a Cepheid's true luminosity from the period, and it's apparent luminosity from observing it, makes it possible to estimate it's distance.

In 1923 Edwin Hubble used the Hooker telescope, which was the largest telescope in the world at the time, to discover Cepheid variables in M31. Before then it had not been known whether "spiral nebulae" were part of the Milky Way galaxy or if they were separate galaxies outside the Milky Way. It was not known whether the Milky way was the whole universe og if there was more. Hubble's discovery of Cepheid variables in M31 allowed him to approximate it's distance, and he understood that was much to far away to be part of the Milky Way. Suddenly the universe became much, much bigger.

The Hooker telescope has a main mirror with a diameter of 250 centimeters. My telescope has a main mirror with a diameter of 20 centimeters. It only goes to show how much better todays cameras are that the same star can be imaged with such a small telescope. M31-V1 was the first Cepheid Hubble found in M31 on October 6, 1923.

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Distribution of astrophotographers

This table shows the number of distinct astrophotographers who have been assigned and IOTD/TP award compared to the total number of images awarded.
	Distinct awarded users	Total awarded images
Image of the day
Top picks
Top pick nominations

Distribution of subject types

This table shows the distribution of awards per subject type, compared to the popularity of images of that subject type.
	Image of the day	Top pick	Top pick nominations	Total submitted
Deep sky
Solar system
Extremely wide field
Star trails
Northern lights
Noctilucent clouds
Landscape

Distribution of data sources

This table shows the distribution of awards per data source, compared to the popularity of images acquired from that data source.
	Image of the day	Top pick	Top pick nominations	Total submitted
Backyard
Traveller
Own remote observatory
Amateur hosting facility
Public amaeteur data
Professional, scientific grade data
Mix of multiple sources
Other
Unknown

The “AstroBin Image of the Day and Top Picks”, or IOTD/TP, is a long-running system to promote beautiful, interesting, peculiar, or otherwise amazing astrophotographs, with a focus on technical excellence. Learn more.

Submitted The date and time when you submitted this image for IOTD/TP consideration.	...
Views by Submitters (available since September 19th, 2023) Every image is assigned to 50% of available Submitters. In the event that at least 80% of them don't view the image before its time in the IOTD/TP process expires, it's assigned to the other 50% of Submitters and the process begins anew.
Promotions by Submitters When 3 distinct Submitters promote the image, it moves on to the next stage of the process: evaluation for Top Pick status. This requirement, in addition to anonymization of images and distribution to only a subset of them, prevents biases and ensures that the best images are selected.
Promotions by Reviewers When 3 distinct Reviewers promote the image, it moves on to the next stage of the process: evaluation for IOTD status.
Early dismissal Staff members have a lot of images to inspect on a daily basis, and they can dismiss images if they believe they don't meet the requirements for IOTD/TP selection. If an image is dismissed 5 times, it's removed from the process. This streamlines the process and ensures that any bias present in promotions could be overruled by other staff members.

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