Where can I find a visible star dataset?

Where can I find a visible star dataset?

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I'm trying to do a project for a databases class where I have a user enter their current location and I tell them what constellations/planets/etc are visible in their area. I've seen this data compiled into images, PDFs, and website entries, but I can't seem to find a csv for it. I get that this data is bound to be massive or extremely complex, but I feel like there should be something out there. Any clues?

If you are looking for stars that are visible to the unaided eye, the Yale Bright Star Catalog is a good source. It includes 9100 stars to approximately magnitude 7 and is available in ASCII and binary formats -- perfect for your database project. Based on the date, time, latitude and longitude, you can calculate which stars are above the horizon.

As someone pointed out, the planets move day-to-day, week-to-week, or month-to-month through the constellations. (The Moon moves much faster than that, going through the complete zodiac in about 27.3 days.) You would need to calculate the position of the planets in order to determine if they are visible or not. That might be beyond the scope of your "database" project.

You can probably extract the data from Stellarium. Also, does it need to be all sky, or not? What Wavelength? If you want an all sky visible catalogue, the United States Navy produced the NOMAD catalog by combining 2MASS, UCAC, and the USNO-B catalog. You could also use the APASS all sky catalog, meant for helping astronomers with photometric calibration.

If you don't care about whether the wavelength is in the visible, CalTech's IRSA has a bunch of infrared source catalogs (the smallest/shallowest one being the IRAS catalog). The deepest all sky infrared catalogs are the WISE sets.

Other good databases to dig in to include the Hipparcos set of parallaxes, or some part of the Gaia catalog.

Where can I find a visible star dataset? - Astronomy

We get quite a few requests here at Curious for help in finding stars that have been "purchased" by our readers. If you're still just thinking about buying a star please read Can I Buy a Star? for our opinions on the companies that offer this service and our suggestions for a much more personal approach. Included below are a few example questions and answers, and I'll start with some general tips.

To find a star, the easiest thing would be to figure out which constellation it is in and where it is in relation to brighter stars. Included with your 'bought star' I presume there is a finding chart which shows this information. Hopefully that includes the constellation it is in and nearby easily recognizable stars. Then you can use a service like or a smartophone app like SkyMap on Android or SkyView on iPhone, to figure out when that area of the sky will be visible for you and then locate the constellation and use that to find the star. Most stars which are 'sold' are very dim and hard to find, which is a shame for people who spend money hoping they will be able to find them.

Another option is to use something like Sky View which has a database of pictures of the whole sky. Pick the 'non-Astronomers' interface enter the RA and Dec in the "Sky Co-ordinates or Object" box and select the Optical survey. This will give you a small image of the sky in which "your" star will be at the center.

What follows are some examples of specific answers. Please try the above, and read-on to see if you can figure it out yourself before sending us specific requests to find your particular star.

I bought a star and a telescope for my boyfriend but we still can't figure out where it is the R.A is 273.21034167 (what does that mean?) DEC is -63.68550278 (don't know what that means either!) could you please help me find it. I need to know the basics of finding it on our own telescope or even just by the naked eye.

R.A. and Dec are abbreviations for Right Ascension and Declination, which are basically like latitude and longitude on the sky. They are explained further in our answer to What are RA and DEC?

The RA and Dec in the above question are listed in decimal degrees, Astronomers more typically use RA and DEC in hours and degrees, converted into that format the RA and Dec above are:M
R.A. = 18 hours, 12 minutes and 50 seconds
Dec = -63 degrees, 41 minutes, 8 seconds

From a given location on Earth you can only see stars at a certain range of declinations. The more negative the declination, the further south you need to be (you have to be further north for positive declinations). Stars at Dec=-63 degrees only just make it above the horizon for people south of latitude 27 degrees, and only comfortably if you are considerably south of that. I hope you live pretty far south, or you will never see this star and if that is the case my opinion of companies who sell stars has dropped even further.

I am a complete novice regarding the stars, although I love looking at them and am in awe. In this vain, I bought my daughter a star in the sky for her first Christmas. It is known as Cygnus RA20h11m42.76s D48deg48m5.66s. Other than identifying the seven sisters to the naked eye, I have no idea what I'm looking for in the sky. I understand that stars move and are only visible in certain areas at certain times of the year. We live in Spain in the Costa Blanca if that helps with timings. I would be very grateful if you could tell a layman how to find a certain star please. Is it visible or would it be too faint and we would need a telescope?

Cygnus is one of my favourite constellations. It makes the shape of a swan flying along the Milky Way (when it is dark enough to see the Milky Way). It's overhead in summer evenings, so a really pleasant constellation to look at, the star at its tail is one of the three brightest stars in the summer sky which make up the "Summer triangle". You can use a site like to make "whole sky charts" for your location and a given time, and with a bit of effort and practice should be able to match that to the stars in the sky.

As for the star you have "bought", it is likely to be too faint for you to see without a telescope. On the other hand Cygnus is a lovely constellation and there is no-one to stop you from "claiming" it for your daughter - it would certainly be a nice tradition for you to go out together as a family to see it every summer.

I'm an employee here at Cornell in the ILR School. For Christmas this year I had a star named after my dad. I have the location of the Star - but I would really like to be able to look at it and know exactly where in the constellation Ursa Major - that it is located. I know how to locate the "Big Dipper" by just looking in the sky - but I really really want to know exactly where in the constellation that his star is located. The chart that they sent me along with the info - does not give any specifics other than the Astronomical Position Star # USC3263172-83, Astronomical Position is Right Ascension 11H45M8.71S, Declination +29D52M39S, Magnitude 14.62. Would it be possible for you to tell me where in the constellation it is located and/or let me see if through the observatory telescope here on campus? Would it be possible to get a chart or photo that I could give to my father along with the location information?

One option you have is to find it in an online Astronomical database. A nice one is Sky View who have a special non-Astronomers interface. If you enter the co-ordinates of the star as 11 45 8.71 +29 52 39 and search the optical database you get a small optical picture of the star. You can pick the size of the image you want up to a few degrees across which allows you to see the star in relation to nearer brighter ones. SIMBAD is another such service, and lets you make a finder chart for objects within a certain radius of the position. You should check the epoch of the co-ordinates you have. I am assuming it is 2000 which is what I put into the search engines (and should be the default), but it is possible that it is 1950 which makes somewhat of a difference. There is also software you can download to do this. Some free ones is Carte du Ciel (which only works for Windows computers) and Stellarium which works on all major operating systems.

The star this company has 'sold' you is a 14th magnitude star, which means it is so dim that it can only be seen with a telescope. The limiting brightness for stars seen with the naked eye is about magnitude 6.5, with binoculars you can see to magnitudes of about 10 (the bigger the number the fainter the star). A 14th magnitude star can only be seen by a fairly large amateur telescope on a dark site. I actually doubt that it is possible to see it using the refracting telescope on the Cornell campus even on a clear night because of the light pollution from north campus. The Cornell Astronomy Club hosts public observing nights most Fridays if you want to try, although they may not be keen to point at your specific star. The name you have for the star (USCetc) appears to be the companies personal ID for the star and is not recognized by any Astronomical catalogues.

It feels mean to tell you this right before you plan to give the present to your father, but actually the bad guys here are the company that sold you the star and continue to make money out of the general public's ignorance about astronomy. As mentioned in the posted article above, it could be nicer (and is just as official) to pick any star you can actually see and make your own certificate.

That's ok, I appreciate the openness. Yesterday another student emailed me and told me basically the same thing. I will probably ask the company for my money back - and see if I can go about it the way that you have suggested.

This page was last updated January 28, 2019.

  • Stars
  • Stargazing
  • Telescopes
  • Hoax
  • Naming
  • Observations
  • Brightness
  • Declination
  • Constellations
  • Right Ascension
  • Magnitude
  • Money

About the Author

Karen Masters

Karen was a graduate student at Cornell from 2000-2005. She went on to work as a researcher in galaxy redshift surveys at Harvard University, and is now on the Faculty at the University of Portsmouth back in her home country of the UK. Her research lately has focused on using the morphology of galaxies to give clues to their formation and evolution. She is the Project Scientist for the Galaxy Zoo project.

Astronomy Science data

Now I want more stars to get a better statistic. I also demand the objects to have an absolute radial velocity not equal to zero. The objects in the data base without a radial velocity looks to be other objects than stars or weird data.

  1. Parallax greater than 0.1 (0.05) arcsec
  2. Radial velocity higher than 0.001 or less than -0.001 km/s

This data purpose is to make a HR-diagram from the nearby stars to our Sun. A parallax of 0.1 arcsec is the same as a distance of 10 parsec or 32.4 Ly (Light years).

Gaia archive:

Below is the page / link to start from:

I setup the conditions like this, but as you see the radial speed is an AND demand, it must be an OR demand. I have to do the query direct in the query window. click "Show Query".

The two last lines you have the query about the radial velocity, that must be changed. I think these queries follow the SQL standard, I have not use that language very much, have to improvise.

I set the two last lines between two parentheses and changed the AND to OR.

I submit the query and got 84 objects (stars), too few, changed the parallax from 100 milli arcsec to 50 milli arcsec. That's a radius of 64 parsec around our Sun's barycenter. Now I got 703 objects in the list, that's ok, don't forget to increase the max numbers from 500 to 1000.

Open office (Excel) Hertzsprung-Russel diagram:

Now the fun starts, these first graphs will only be 2 dimensional and then I can do the calculation in Open Office Calc. Note: You can do data graphs in the Gaia page also, but for the moment I prefer to do it in my own spreadsheet, I get more control of what I do.

First diagram I calculate and plot is a Hertzsprung-Russel diagram. Above the mainstream you find the giants, below the mainstream you find the white dwarfs. If all stars that I selected has the same origin as our Sun you can follow their development in the diagram. Stars born to the bottom right, then follow the mainstream up to right, later up to the giants at right, end as white dwarf at bottom. But which of the stars has the same origin as our Sun ? Hard to say, our Sun is 5 billion years old and has done about 20 revolutions around the galaxy, a lot has happened to the orbits of the stars during this time. The yellow ring symbolize where our Sun belong in the HR-diagram. It took our Sun 5 billion years to reach this point, half its lifetime is spent.

More information about Hertzsprung-Russel diagram at Wikipedia:

To draw a diagram like this you need, the stars effective temperature, the distance in parsec, and the absolute magnitude. All these data you can get from the Gaia data we selected, but needs some recalculations.

  1. The effective temperature is already in the Gaia data
  2. The distance in parsec you get from the parallax, parsec = 1000 / parallax in milli arcsec (mas)
  3. The absolute magnitude = apparent magnitude - 5*log (distance in parsec) + 5
  4. The relative luminosity rel Sun = 10 (abs mag1 - abs mag2)

Note that the magnitude in the Gaia data is not exactly the visual magnitude, it's more the sum of the blue and red filter data and called green mag.

Even more data can be displayed in the HR diagram, the stars radius. We can calculate the radius from the luminosity and temperature. Now it's very clear which stars are the giants. A small star must be much hotter to have the same luminosity as a big star, from that we can calculate the diameter of the stars.

To draw a diagram like this you need, the stars effective temperature, the distance in parsec, and the absolute magnitude. All these data you can get from the data we selected, but some needs further calculations.

  1. The relation luminosity relation between the stars / Sun we already calculated above
  2. The effective temperature we got already in Gaia data direct
  3. From the equation: L = 4 * pi * R 2 * a * T 4 we get R/RS = +/- (L/LS) 1/2 * (TS/T) 2

The a is Boltzman's const. and the S index relate to Sun.

In the software Open Office Calc I use this diagram, it is called bubble diagram. It takes a lot of power from the computer to calculate it like this with shaded diameters.

More information about Absolute magnitude at Wikipedia:


My plan is to use something like Matlab when I want to do more complicated math. Matlab I used at the University but it's very expensive to own as a private person. Octave is a similar math tool and it's free. You can download it from here:

More information about Octave:

Setup a equation in Octave is a bit different compare to Excel. This is an example of the equation I used in Excel to calculate the needed data for a HM-Diagram. It's a macro written in the internal editor, but you can use Notepad as well. In this case the Excel or Open Office is better to use.

After run the macro in the command window we get this result. Data we can use to draw a HM-Diagram.

Some useful links with information:

One limitation in Gaia data is that no bright stars are included. Gaia is optimized to detect weak stars and all star visible to the naked eye over saturate the CCD sensor and not usable.

This work has made use of data from the European Space Agency (ESA) mission Gaia ( gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, web/ gaia/ dpac/ consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

Gaia Collaboration et al. (2016): Description of the Gaia mission (spacecraft, instruments, survey and measurement principles, and operations).
Gaia Collaboration et al. (2018b): Summary of the contents and survey properties.

Page best viewed with screen set to 1024x768 or higher. The pictures that are labeled Lars Karlsson, text and web page designs are © Copyright 2002 - 2019 by Lars Karlsson. All rights reserved. They may not be reproduced, published, copied or transmitted in any form, including electronically on the Internet or World Wide Web, without written permission of the author.

Edwin Hubble: Expanding the Universe

The son of a Missouri insurance agent, Edwin Hubble (Figure 2) graduated from high school at age 16. He excelled in sports, winning letters in track and basketball at the University of Chicago, where he studied both science and languages. Both his father and grandfather wanted him to study law, however, and he gave in to family pressure. He received a prestigious Rhodes scholarship to Oxford University in England, where he studied law with only middling enthusiasm. Returning to be the United States, he spent a year teaching high school physics and Spanish as well as coaching basketball, while trying to determine his life’s direction.

Figure 2: Edwin Hubble (1889–1953). Edwin Hubble established some of the most important ideas in the study of galaxies.

The pull of astronomy eventually proved too strong to resist, and so Hubble went back to the University of Chicago for graduate work. Just as he was about to finish his degree and accept an offer to work at the soon-to be completed 2.5-meter telescope, the United States entered World War I, and Hubble enlisted as an officer. Although the war had ended by the time he arrived in Europe, he received more officer’s training abroad and enjoyed a brief time of further astronomical study at Cambridge before being sent home.

In 1919, at age 30, he joined the staff at Mount Wilson and began working with the world’s largest telescope. Ripened by experience, energetic, disciplined, and a skillful observer, Hubble soon established some of the most important ideas in modern astronomy. He showed that other galaxies existed, classified them on the basis of their shapes, found a pattern to their motion (and thus put the notion of an expanding universe on a firm observational footing), and began a lifelong program to study the distribution of galaxies in the universe. Although a few others had glimpsed pieces of the puzzle, it was Hubble who put it all together and showed that an understanding of the large-scale structure of the universe was feasible.

His work brought Hubble much renown and many medals, awards, and honorary degrees. As he became better known (he was the first astronomer to appear on the cover of Time magazine), he and his wife enjoyed and cultivated friendships with movie stars and writers in Southern California. Hubble was instrumental (if you’ll pardon the pun) in the planning and building of the 2.5-meter telescope on Palomar Mountain, and he had begun to use it for studying galaxies when he passed away from a stroke in 1953.

When astronomers built a space telescope that would allow them to extend Hubble’s work to distances he could only dream about, it seemed natural to name it in his honor. It was fitting that observations with the Hubble Space Telescope (and his foundational work on expansion of the universe) contributed to the 2011 Nobel Prize in Physics, given for the discovery that the expansion of the universe is accelerating (a topic we will expand upon in the chapter on The Big Bang).

Key concepts and summary

Faint star clusters, clouds of glowing gas, and galaxies all appeared as faint patches of light (or nebulae) in the telescopes available at the beginning of the twentieth century. It was only when Hubble measured the distance to the Andromeda galaxy using cepheid variables with the giant 2.5-meter reflector on Mount Wilson in 1924 that the existence of other galaxies similar to the Milky Way in size and content was established.

June 2021 guide to the bright planets

In late May and early June 2021, watch for the waning moon to pass to the south of the giant gas planets, Saturn and Jupiter. It’ll pass them again during the last week of June. Read more. The young waxing crescent moon sweeps to the north the blazing planet Venus and then the much fainter red planet Mars, before and during mid-June. Read more. During the last week of June 2021, watch for the moon to again sweep by the gas giants Saturn and Jupiter. Read more.

‘Ring of fire’ solar eclipse June 10

Venus and Mars

The brightest planet Venus and red planet Mars remain fixtures of the early evening sky throughout June 2021. Although Mars looms higher up in the western sky after sunset – and stays out longer after dark – than Venus does, Mars will be the harder planet to spot. After all, Venus – the brightest of all planets – outshines Mars by more than a hundredfold.

Your best bet is to first spot dazzling Venus, as it pops out at dusk, way before any other bright star. You’ll likely find Venus blazing away quite low in your western sky some 40 to 45 minutes (or sooner) after sunset. Use this bright beacon to find your way to Mars, which comes out as evening twilight gives way to nightfall. Early in the month, you might not see Mars until after Venus sets. To find out Venus’ setting time, go to TimeandDate or Old Farmer’s Almanac.

Mars is fairly easy to see in a dark sky. But it’s best to seek out modestly-bright Mars at early evening, when it’s still relatively high above your western horizon. We give you fair warning! The red planet is only going to get fainter as this year progresses. In the months ahead, Mars will surely dim as – day by day – it lags farther behind Earth in the great race of the planets, and sinks closer to the setting sun.

At mid-northern latitudes, Mars sets about one hour after nightfall (end of astronomical twilight) in early June, and around nightfall by the month’s end.

At temperate latitudes in the Southern Hemisphere, Mars sets about 1 1/2 hours (90 minutes) after nightfall in early June, and about one hour after nightfall by the month’s end.

Find out both the sunset time and the time of nightfall (end of astronomical twilight) via

While Mars is sinking toward the setting sun by the day, Venus is climbing upward, away from the sunset. Next month, these two worlds will meet up for a close-knit conjunction on July 13, 2021. After that, Venus will supplant Mars as the higher evening planet.

Mars, though nominally an evening planet until October 2021, will likely be out of sight and out of mind by August 2021. By that time, expect Mars to succumb to the glow of evening twilight.

On the other hand, Venus boldly shines in the evening sky for the rest of this year, to reach its greatest elongation from the sun on October 29, 2021 (see diagram below), and to attain its greatest brilliance as the evening “star” around the time of the new moon on December 4, 2021. Circle this date on your calendar, and see if it’s true that Venus can cast a shadow on a dark night!

In this view, Venus and all the planets travel counterclockwise around the sun. Venus, being an inferior planet, shows phases just like the moon. It has swept to the far side of the sun (at superior conjunction) on March 26, 2021, to exit the morning sky and to enter the evening sky. Venus will reach its greatest eastern (evening) elongation from the sun (half Venus) on October 29, 2021. Then on January 9, 2022, Venus will go between the Earth and sun, at inferior conjunction, to exit the evening sky and to enter the morning sky. Image via UCLA.

Jupiter and Saturn

You can find giant planet Jupiter and ringed Saturn in June 2021 late at night and in the hours before sunrise. If you’re a night owl, you might catch these two planets low in your southeast sky before bedtime. The early bird still has the advantage, though, as these two worlds appear much higher up in the sky during the predawn hours.

Saturn rises first. At mid-northern latitudes, Saturn comes up around local midnight at the beginning of the month, and around mid-evening by the month’s end. (By midnight, we mean midway between sunset and sunrise.) Jupiter follows Saturn into the sky about an hour later.

At temperate latitudes in the Southern Hemisphere, Saturn rises around mid-to-late evening in early June, and by the month’s end, comes up at early-to-mid evening evening. Jupiter follows Saturn into the sky around 1 1/2 hours later.

For more specific information on when Jupiter and Saturn rise into your sky, consult either The Old Farmer’s Almanac (U.S. and Canada) or (worldwide).

Use the moon to help guide you to Jupiter and Saturn in late May and early June 2021, and then again late in the month, from about June 27 to 29.


Mercury – the innermost planet – isn’t easily visible in June 2021. This planet is low in the west after sunset when the month begins. It’ll exit the evening sky and enter the morning sky when it passes between the Earth and sun (at inferior conjunction) on June 11, 2021. Alert sky watchers have a chance to catch Mercury in the morning sky – in the east before sunrise – by the last week of June. By early July, Mercury will appear more easily visible in the east before the sun. The waning moon will point to it, and pass near it, on July 5, 6, 7 and 8. Read more about Mercury in early July.

Not to scale. Mercury’s mean distance from the sun is about 0.39 times Earth’s distance from the sun. We’re looking down from the north side of the solar system plane. In this view, Mercury and Earth circle the sun in a counterclockwise direction. Earth and Mercury also rotate on their axes counterclockwise as seen from the north side of the solar system. At its greatest eastern elongation, Mercury is seen in the west after sunset and at its greatest western elongation, Mercury is seen in the east before sunrise.

What do we mean by bright planet?

By bright planet, we mean any solar system planet that is easily visible without an optical aid and that has been watched by our ancestors since time immemorial. In their outward order from the sun, the five bright planets are Mercury, Venus, Mars, Jupiter and Saturn. These planets actually do appear bright in our sky. They are typically as bright as – or brighter than – the brightest stars. Plus, these relatively nearby worlds tend to shine with a steadier light than the distant, twinkling stars. You can spot them, and come to know them as faithful friends, if you try.

Bottom line: All you need to know about how to find the bright planets of the solar system during the month of June.

Galaxy Morphological Classification using Machine Learning

The Galaxy Zoo (GZ) and Galaxy Zoo 2 (GZ2)projects run by the Zooniverse citizen science initiative was set up to assist in the morphological classification of large datasets of galaxy images (Wikipedia 2019 Kuminski et al 2014). Whilst this project has been shown to be very effective at classifying galaxies, this approach is not going to scale up to the demands of modern digital sky surveys powered by robotic telescopes (Kuminski et al 2014). However, the data sets produced by the GZ & GZ2 projects may prove crucial into the development of an automated galaxy classification system (Kuminski et al 2014).

One example of how this data might be used is the experimental work carried out by Kuminski et al (2014) which has shown that the GZ2 dataset can be used to train a machine learning algorithm, which can then be used to automatically classify various aspects of galaxy morphology.

An important aspect of the GZ and GZ 2 data is that each image is classified multiple times by multiple users, for some galaxies where the morphological features are ambiguous there can be a high degree of variance in the classifications (Kuminski et al 2014). To provide the machine learning algorithm with the cleanest possible training data, images with a high degree of agreement on classification are required, however there is a trade-off to be made here as this will reduce the number of images available for training the model, and depending on how high you set the agreement threshold some classes of galaxy can end up being completely excluded from the training set (Kuminski et al 2014). Additionally, this can lead to an unbalanced data set which can introduce bias, to balance the dataset the number of samples in each galaxy class is reduced to match the that of the smallest class (Kuminski et al 2014).

Due to the complicated and heterogeneous nature of galaxy images a wide range of measures from different aspects of the image need to be analysed, and in this particular instance, the Wndchrm schema was chosen (Kuminski et al 2014). Wndchrm is an open source utility which was originally developed for biological image analysis however, it has been previously been used for classification of galaxy morphology in the past (Kuminski et al 2014).

The Wndchrm schema extracts over 2,000 descriptive features from each image, these features are drawn from various aspects of the image such as texture, pixel intensity, contrast and polynomial representations (Kuminski et al 2014 Shamir et al 2008). Several transforms are stacked on top of each other to extract further features which can be informative in some cases (Kuminski et al 2014 Shamir et al 2008). For Detailed description of the algorithms used by the Wndchrm utility refer to Orlov, N et al (2008) & Shamir et al (2008)

The Wndchrm schema was originally designed for analysing medical images, as such only a limited number of the features produced by this process are going to be sufficiently informative, additionally some of these features will be representative of noise in the imagery, retaining these features can impact negatively on the classification accuracy (Kuminski et al 2014 Shamir et al 2008). To address this issue Fisher discriminant scores are calculated for each feature and based on these scores only the top 5% of features are kept (Kuminski et al 2014 Shamir et al 2008). A Weighted Nearest Neighbors algorithm is then trained where the Fisher discriminant scores are used as weights against the features (Kuminski et al 2014).

The resulting model was able to achieve an accuracy of 85% on 8 out of 10 morphological classifications, however for some classifications, the high agreement threshold resulted in there being very little or no samples for training, for these galaxies automatic classification was not possible (Kuminski et al 2014).

Brightest Stars in Canis Major

The 10 brightest stars in the constellation Canis Major by magnitude.

    1. Star
    2. Magnitude
    3. Spectral class
    1. (&alpha Cma)
  • -1.46
  • A0m
    1. (&epsilon Cma)
  • 1.5
  • B2II
    1. (&delta Cma)
  • 1.83
  • F8Ia
    1. (&beta Cma)
  • 1.98
  • B1II/III
    1. (&eta Cma)
  • 2.45
  • B5Ia
    1. (&zeta Cma)
  • 3.02
  • B2.5V
    1. (&omicron 2 Cma)
  • 3.02
  • B3Ia
    1. (&sigma Cma)
  • 3.49
  • K4III
    1. (&kappa Cma)
  • 3.5
  • B1.5IVne
    1. (&omicron 1 Cma)
  • 3.89
  • K3Iab

Questions About Stargazing

The Ask an Astronomer team's favorite links about Stargazing:

  • Heavens Above. This free site allows you to enter your location and creates customized star charts for you. It also shows information on how you can see the ISS and other artificial satellites.
  • Sky at a Glance: Find out what stars, planets and other objects are visible in the night sky from Sky and Telescope Magazine.
  • Telescope review web site: A detailed review of over 100 telescopes for amateurs.
  • Sky View: An on-line virtual observatory with a special non-astronomer interface. View pictures of objects in the night sky in many wavelenghts.
  • U.S. Naval Observatory Data Services: Easy to use web forms which provide data on the positions of the sun, moon and other celestial objects.

How to ask a question?

If you have a question about another area of astronomy, find the topic you're interested in from the archive on the side bar or search using the below search form. If you still can't find what you are looking for, submit your question here.


Ancient Near East Edit

From their existing records, it is known that the ancient Egyptians recorded the names of only a few identifiable constellations and a list of thirty-six decans that were used as a star clock. [1] The Egyptians called the circumpolar star "the star that cannot perish" and, although they made no known formal star catalogues, they nonetheless created extensive star charts of the night sky which adorn the coffins and ceilings of tomb chambers. [2]

Although the ancient Sumerians were the first to record the names of constellations on clay tablets, [3] the earliest known star catalogues were compiled by the ancient Babylonians of Mesopotamia in the late 2nd millennium BC, during the Kassite Period (c. 1531 BC to c. 1155 BC). They are better known by their Assyrian-era name 'Three Stars Each'. These star catalogues, written on clay tablets, listed thirty-six stars: twelve for "Anu" along the celestial equator, twelve for "Ea" south of that, and twelve for "Enlil" to the north. [4] The Mul.Apin lists, dated to sometime before the Neo-Babylonian Empire (626–539 BC), [5] are direct textual descendants of the "Three Stars Each" lists and their constellation patterns show similarities to those of later Greek civilization. [6]

Hellenistic world and Roman Empire Edit

In Ancient Greece, the astronomer and mathematician Eudoxus laid down a full set of the classical constellations around 370 BC. [7] His catalogue Phaenomena, rewritten by Aratus of Soli between 275 and 250 BC as a didactic poem, became one of the most consulted astronomical texts in antiquity and beyond. [7] It contained descriptions of the positions of the stars and the shapes of the constellations, and provided information on their relative times of rising and setting. [7]

Approximately in the 3rd century BC, the Greek astronomers Timocharis of Alexandria and Aristillus created another star catalogue. Hipparchus (c. 190 – c. 120 BC) completed his star catalogue in 129 BC, [8] which he compared to Timocharis' and discovered that the longitude of the stars had changed over time. This led him to determine the first value of the precession of the equinoxes. [9] In the 2nd century, Ptolemy (c. 90 – c. 186 AD) of Roman Egypt published a star catalogue as part of his Almagest, which listed 1,022 stars visible from Alexandria. [10] Ptolemy's catalogue was based almost entirely on an earlier one by Hipparchus. [11] It remained the standard star catalogue in the Western and Arab worlds for over eight centuries. The Islamic astronomer al-Sufi updated it in 964, and the star positions were redetermined by Ulugh Beg in 1437, [12] but it was not fully superseded until the appearance of the thousand-star catalogue of Tycho Brahe in 1598. [13]

The ancient Vedic and other scriptures of India were very well aware of the astronomical positions and constellations. Both Mahabharata and Ramayana provide references to various events in terms of the planetary positions and constellations of that time. The Planetary positions at the time of Mahabharata war has been given comprehensively. A very interesting and exhaustive discussion about the planetary positions along with specific name of constellations appears in a paper by R N Iyengar in the scientific journal of 'Indian journal of History of Science' [14]

Ancient China Edit

The earliest known inscriptions for Chinese star names were written on oracle bones and date to the Shang Dynasty (c. 1600 – c. 1050 BC). [15] Sources dating from the Zhou Dynasty (c. 1050 – 256 BC) which provide star names include the Zuo Zhuan, the Shi Jing, and the "Canon of Yao" (堯典) in the Book of Documents. [16] The Lüshi Chunqiu written by the Qin statesman Lü Buwei (d. 235 BC) provides most of the names for the twenty-eight mansions (i.e. asterisms across the ecliptic belt of the celestial sphere used for constructing the calendar). An earlier lacquerware chest found in the Tomb of Marquis Yi of Zeng (interred in 433 BC) contains a complete list of the names of the twenty-eight mansions. [17] Star catalogues are traditionally attributed to Shi Shen and Gan De, two rather obscure Chinese astronomers who may have been active in the 4th century BC of the Warring States period (403–221 BC). [18] The Shi Shen astronomy (石申天文, Shi Shen tienwen) is attributed to Shi Shen, and the Astronomic star observation (天文星占, Tianwen xingzhan) to Gan De. [19]

It was not until the Han Dynasty (202 BC – 220 AD) that astronomers started to observe and record names for all the stars that were apparent (to the naked eye) in the night sky, not just those around the ecliptic. [20] A star catalogue is featured in one of the chapters of the late 2nd-century-BC history work Records of the Grand Historian by Sima Qian (145–86 BC) and contains the "schools" of Shi Shen and Gan De's work (i.e. the different constellations they allegedly focused on for astrological purposes). [21] Sima's catalogue—the Book of Celestial Offices (天官書 Tianguan shu)—includes some 90 constellations, the stars therein named after temples, ideas in philosophy, locations such as markets and shops, and different people such as farmers and soldiers. [22] For his Spiritual Constitution of the Universe (靈憲, Ling Xian) of 120 AD, the astronomer Zhang Heng (78–139 AD) compiled a star catalogue comprising 124 constellations. [23] Chinese constellation names were later adopted by the Koreans and Japanese. [24]

Islamic world Edit

A large number of star catalogues were published by Muslim astronomers in the medieval Islamic world. These were mainly Zij treatises, including Arzachel's Tables of Toledo (1087), the Maragheh observatory's Zij-i Ilkhani (1272) and Ulugh Beg's Zij-i-Sultani (1437). Other famous Arabic star catalogues include Alfraganus' A compendium of the science of stars (850) which corrected Ptolemy's Almagest [25] and al-Sufi's Book of Fixed Stars (964) which described observations of the stars, their positions, magnitudes, brightness and colour, drawings for each constellation, and the first known description of the Andromeda Galaxy. [26] Many stars are still known by their Arabic names (see List of Arabic star names).

Pre-Columbian Americas Edit

The Motul Dictionary, compiled in the 16th century by an anonymous author (although attributed to Fray Antonio de Ciudad Real), contains a list of stars originally observed by the ancient Mayas. The Maya Paris Codex also contain symbols for different constellations which were represented by mythological beings. [27]

Bayer and Flamsteed catalogues Edit

Two systems introduced in historical catalogues remain in use to the present day. The first system comes from the German astronomer Johann Bayer's Uranometria, published in 1603 and regarding bright stars. These are given a Greek letter followed by the genitive case of the constellation in which they are located examples are Alpha Centauri or Gamma Cygni. The major problem with Bayer's naming system was the number of letters in the Greek alphabet (24). It was easy to run out of letters before running out of stars needing names, particularly for large constellations such as Argo Navis. Bayer extended his lists up to 67 stars by using lower-case Roman letters ("a" through "z") then upper-case ones ("A" through "Q"). Few of those designations have survived. It is worth mentioning, however, as it served as the starting point for variable star designations, which start with "R" through "Z", then "RR", "RS", "RT". "RZ", "SS", "ST". "ZZ" and beyond.

The second system comes from the English astronomer John Flamsteed's Historia coelestis Britannica (1725). It kept the genitive-of-the-constellation rule for the back end of his catalogue names, but used numbers instead of the Greek alphabet for the front half. Examples include 61 Cygni and 47 Ursae Majoris.

Bayer and Flamsteed covered only a few thousand stars between them. In theory, full-sky catalogues try to list every star in the sky. There are, however, billions of stars resolvable by 21st century telescopes, so this is an impossible goal with this kind of catalog, an attempt is generally made to get every star brighter than a given magnitude.

LAL Edit

Jérôme Lalande published the Histoire Céleste Française in 1801, which contained an extensive star catalog, among other things. The observations made were made from the Paris Observatory and so it describes mostly northern stars. This catalogue contained the positions and magnitudes of 47,390 stars, out to magnitude 9, and was the most complete catalogue up to that time. A significant reworking of this catalogue by followers of Lalande in 1846 added reference numbers to the stars that are used to refer to some of these stars to this day. The decent accuracy of this catalogue kept it in common use as a reference by observatories around the world throughout the 19th century.


The Bonner Durchmusterung (German: Bonn sampling) and follow-ups were the most complete of the pre-photographic star catalogues.

The Bonner Durchmusterung itself was published by Friedrich Wilhelm Argelander, Adalbert Krüger, and Eduard Schönfeld between 1852 and 1859. It covered 320,000 stars in epoch 1855.0.

As it covered only the northern sky and some of the south (being compiled from the Bonn observatory), this was then supplemented by the Südliche Durchmusterung (SD), which covers stars between declinations −1 and −23 degrees (1886, 120,000 stars). It was further supplemented by the Cordoba Durchmusterung (580,000 stars), which began to be compiled at Córdoba, Argentina in 1892 under the initiative of John M. Thome and covers declinations −22 to −90. Lastly, the Cape Photographic Durchmusterung (450,000 stars, 1896), compiled at the Cape, South Africa, covers declinations −18 to −90.

Astronomers preferentially use the HD designation (see next entry) of a star, as that catalogue also gives spectroscopic information, but as the Durchmusterungs cover more stars they occasionally fall back on the older designations when dealing with one not found in Draper. Unfortunately, a lot of catalogues cross-reference the Durchmusterungs without specifying which one is used in the zones of overlap, so some confusion often remains.

Star names from these catalogues include the initials of which of the four catalogues they are from (though the Southern follows the example of the Bonner and uses BD CPD is often shortened to CP), followed by the angle of declination of the star (rounded towards zero, and thus ranging from +00 to +89 and −00 to −89), followed by an arbitrary number as there are always thousands of stars at each angle. Examples include BD+50°1725 or CD−45°13677.


The Henry Draper Catalogue was published in the period 1918–1924. It covers the whole sky down to about ninth or tenth magnitude, and is notable as the first large-scale attempt to catalogue spectral types of stars. The catalogue was compiled by Annie Jump Cannon and her co-workers at Harvard College Observatory under the supervision of Edward Charles Pickering, and was named in honour of Henry Draper, whose widow donated the money required to finance it.

HD numbers are widely used today for stars which have no Bayer or Flamsteed designation. Stars numbered 1–225300 are from the original catalogue and are numbered in order of right ascension for the 1900.0 epoch. Stars in the range 225301–359083 are from the 1949 extension of the catalogue. The notation HDE can be used for stars in this extension, but they are usually denoted HD as the numbering ensures that there can be no ambiguity.

AC Edit

The Catalogue astrographique (Astrographic Catalogue) was part of the international Carte du Ciel programme designed to photograph and measure the positions of all stars brighter than magnitude 11.0. In total, over 4.6 million stars were observed, many as faint as 13th magnitude. This project was started in the late 19th century. The observations were made between 1891 and 1950. To observe the entire celestial sphere without burdening too many institutions, the sky was divided among 20 observatories, by declination zones. Each observatory exposed and measured the plates of its zone, using a standardized telescope (a "normal astrograph") so each plate photographed had a similar scale of approximately 60 arcsecs/mm. The U.S. Naval Observatory took over custody of the catalogue, now in its 2000.2 edition.

BS, BSC, HR Edit

First published in 1930 as the Yale Catalog of Bright Stars, this catalogue contained information on all stars brighter than visual magnitude 6.5 in the Harvard Revised Photometry Catalogue. The list was revised in 1983 with the publication of a supplement that listed additional stars down to magnitude 7.1. The catalogue detailed each star's coordinates, proper motions, photometric data, spectral types, and other useful information.

The last printed version of the Bright Star Catalogue was the 4th revised edition, released in 1982. The 5th edition is in electronic form and is available online. [28]

SAO Edit

The Smithsonian Astrophysical Observatory catalogue was compiled in 1966 from various previous astrometric catalogues, and contains only the stars to about ninth magnitude for which accurate proper motions were known. There is considerable overlap with the Henry Draper catalogue, but any star lacking motion data at that time is omitted. The epoch for the position measurements in the latest edition is J2000.0. The SAO catalogue contains this major piece of information not in Draper, the proper motion of the stars, so it is often used when that fact is of importance. The cross-references with the Draper and Durchmusterung catalogue numbers in the latest edition are also useful.

Names in the SAO catalogue start with the letters SAO, followed by a number. The numbers are assigned following 18 ten-degree bands in the sky, with stars sorted by right ascension within each band.

USNO-B1.0 Edit

USNO-B1.0 [29] is an all-sky catalogue created by research and operations astrophysicists at the U.S. Naval Observatory (as developed at the United States Naval Observatory Flagstaff Station), that presents positions, proper motions, magnitudes in various optical passbands, and star/galaxy estimators for 1,042,618,261 objects derived from 3,643,201,733 separate observations. The data was obtained from scans of 7,435 Schmidt plates taken for the various sky surveys during the last 50 years. USNO-B1.0 is believed to provide all-sky coverage, completeness down to V = 21, 0.2 arcsecond astrometric accuracy at J2000.0, 0.3 magnitude photometric accuracy in up to five colors, and 85% accuracy for distinguishing stars from non-stellar objects. USNO-B is now followed by NOMAD [30] both can be found on the Naval Observatory server. [31] The Naval Observatory is currently working on B2 and C variants of the USNO catalogue series.

GSC Edit

The Guide Star Catalog is an online catalogue of stars produced for the purpose of accurately positioning and identifying stars satisfactory for use as guide stars by the Hubble Space Telescope program. The first version of the catalogue was produced in the late 1980s by digitizing photographic plates and contained about 20 million stars, out to about magnitude 15. The latest version of this catalogue contains information for 945,592,683 stars, out to magnitude 21. The latest version continues to be used to accurately position the Hubble Space Telescope.

PPM Edit

The PPM Star Catalogue (1991) is one of the best, [ according to whom? ] both in the proper motion and star position till 1999. Not as precise as the Hipparcos catalogue but with many more stars. The PPM was built from BD, SAO, HD and more, with sophisticated algorithm and is an extension for the Fifth Fundamental Catalogue, "Catalogues of Fundamental Stars".

HIP Edit

The Hipparcos catalogue was compiled from the data gathered by the European Space Agency's astrometric satellite Hipparcos, which was operational from 1989 to 1993. The catalogue was published in June 1997 and contains 118,218 stars an updated version with re-processed data was published in 2007. It is particularly notable for its parallax measurements, which are considerably more accurate than those produced by ground-based observations.

Gaia Catalogue Edit

The Gaia catalogue is released in stages that will contain increasing amounts of information the early releases also miss some stars, especially fainter stars located in dense star fields. [32] Data from every data release can be accessed at the Gaia archive. [33] Gaia DR1, the first data release of the spacecraft Gaia mission, based on 14 months of observations made through September 2015, took place on 13 September 2016. [34] [35] The data release includes positions and magnitudes in a single photometric band for 1.1 billion stars using only Gaia data, positions, parallaxes and proper motions for more than 2 million stars based on a combination of Gaia and Tycho-2 data for those objects in both catalogues, light curves and characteristics for about 3000 variable stars, and positions and magnitudes for more than 2000 extragalactic sources used to define the celestial reference frame. [36] [37] The second data release (DR2), which occurred on 25 April 2018, [38] [39] is based on 22 months of observations made between 25 July 2014 and 23 May 2016. It includes positions, parallaxes and proper motions for about 1.3 billion stars and positions of an additional 300 million stars, red and blue photometric data for about 1.1 billion stars and single colour photometry for an additional 400 million stars, and median radial velocities for about 7 million stars between magnitude 4 and 13. It also contains data for over 14,000 selected Solar System objects. [40] [41] The first part of the third data release, EDR3 (Early Data Release 3) was released on 3 December 2020. It is based on 34 months of observations and consists of improved positions, parallaxes and proper motions of over 1.8 billion objects [42] The full DR3, expected in Early 2022, will include the EDR3 data plus Solar System data variability information results for non-single stars, for quasars, and for extended objects astrophysical parameters and a special data set, the Gaia Andromeda Photometric Survey (GAPS). [43] The release date of the full Gaia catalogue is to be determined. [44]

Specialized catalogues make no effort to list all the stars in the sky, working instead to highlight a particular type of star, such as variables or nearby stars.

ADS Edit

Aitken's double star catalogue (1932) lists 17,180 double stars north of declination −30 degrees.

Carbon stars Edit

Gl, GJ, Wo Edit

The Gliese (later Gliese-Jahreiß) catalogue attempts to list all star systems within 20 parsecs (65 ly) of Earth ordered by right ascension (see the List of nearest stars). Later editions expanded the coverage to 25 parsecs (82 ly). Numbers in the range 1.0–915.0 (Gl numbers) are from the second edition, which was

Catalogue of Nearby Stars (1969, W. Gliese).

The integers up to 915 represent systems which were in the first edition. Numbers with a decimal point were used to insert new star systems for the second edition without destroying the desired order (by right ascension). This catalogue is referred to as CNS2, although this name is never used in catalogue numbers.

Numbers in the range 9001–9850 (Wo numbers) are from the supplement

Extension of the Gliese catalogue (1970, R. Woolley, E. A. Epps, M. J. Penston and S. B. Pocock).

Numbers in the ranges 1000–1294 and 2001–2159 (GJ numbers) are from the supplement

Nearby Star Data Published 1969–1978 (1979, W. Gliese and H. Jahreiß).

The range 1000–1294 represents nearby stars, while 2001–2159 represents suspected nearby stars. In the literature, the GJ numbers are sometimes retroactively extended to the Gl numbers (since there is no overlap). For example, Gliese 436 can be interchangeably referred to as either Gl 436 or GJ 436.

Numbers in the range 3001–4388 are from

Preliminary Version of the Third Catalogue of Nearby Stars (1991, W. Gliese and H. Jahreiß).

Although this version of the catalogue was termed "preliminary", it is still the current one as of March 2006 [update] , and is referred to as CNS3. It lists a total of 3,803 stars. Most of these stars already had GJ numbers, but there were also 1,388 which were not numbered. The need to give these 1,388 some name has resulted in them being numbered 3001–4388 (NN numbers, for "no name"), and data files of this catalogue now usually include these numbers. An example of a star which is often referred to by one of these unofficial GJ numbers is GJ 3021.


The General Catalogue of Trigonometric Parallaxes, first published in 1952 and later superseded by the New GCTP (now in its fourth edition), covers nearly 9,000 stars. Unlike the Gliese, it does not cut off at a given distance from the Sun rather it attempts to catalogue all known measured parallaxes. It gives the co-ordinates in 1900 epoch, the secular variation, the proper motion, the weighted average absolute parallax and its standard error, the number of parallax observations, quality of interagreement of the different values, the visual magnitude and various cross-identifications with other catalogues. Auxiliary information, including UBV photometry, MK spectral types, data on the variability and binary nature of the stars, orbits when available, and miscellaneous information to aid in determining the reliability of the data are also listed.

Proper motion catalogues Edit

A common way of detecting nearby stars is to look for relatively high proper motions. Several catalogues exist, of which we'll mention a few. The Ross and Wolf catalogues pioneered the domain:

Ross, Frank Elmore, New Proper Motion Stars, eight successive lists, The Astronomical Journal, Vol. 36 to 48, 1925–1939 [47] Wolf, Max, "Katalog von 1053 stärker bewegten Fixsternen", Veröff. d. Badischen Sternwarte zu Heidelberg (Königstuhl), Bd. 7, No. 10, 1919 and numerous lists in Astronomische Nachrichten, 209 to 236, 1919–1929 [48]

Willem Jacob Luyten later produced a series of catalogues:

L – Luyten, Proper motion stars and White dwarfs

Luyten, W. J., Proper Motion Survey with the forty-eight inch Schmidt Telescope, University of Minnesota, 1941 (General Catalogue of the Bruce Proper-Motion Survey)

LFT – Luyten Five-Tenths catalogue

Luyten, W. J., A Catalog of 1849 Stars with Proper Motion exceeding 0.5" annually, Lund Press, Minneapolis (Mn), 1955 ([1])

LHS – Luyten Half-Second catalogue

Luyten, W. J., Catalogue of stars with proper motions exceeding 0"5 annually, University of Minnesota, 1979 ([2])

LTT – Luyten Two-Tenths catalogue

Luyten, W. J. Luyten's Two Tenths. A catalogue of 9867 stars in the Southern Hemisphere with proper motions exceeding 0".2 annually, Minneapolis, 1957 A catalogue of 7127 stars in the Northern Hemisphere with proper motions exceeding 0".2 annually``, Minneapolis, 1961 also supplements 1961–1962. ([3][4][5][6])

NLTT – New Luyten Two-Tenths catalogue

Luyten, W. J., New Luyten Catalogue of stars with proper motions larger than two tenths of an arcsecond (NLTT), Univ. of Minnesota, 1979, supplement 1980 ([7][8])

LPM – Luyten Proper-Motion catalogue

Luyten, W. J., Proper Motion Survey with the 48 inch Schmidt Telescope, University of Minnesota, 1963–1981 LP numbers: L in zones −45 to −89 deg. LP in zones +89 to −44 deg.

Around the same time period, Henry Lee Giclas worked on a similar series of catalogues:

Giclas, H. L., et al., Lowell Proper Motion Survey, Lowell Observatory Bulletin, 1971–1979 ([9])

Struve Double Star Catalog Edit

Friedrich Georg Wilhelm von Struve discovered a very large number of double stars and in 1827 published his double star catalogue Catalogus novus stellarum duplicium. [49] For example, binary star 61 Cygni is designated "Struve 2758" or "STF 2758". Stars of his catalogue are sometimes indicated by the Greek letter sigma, Σ. Thus, 61 Cygni is also designated as Σ2758. [50]

Uvby98 Edit

The ubvyβ Photoelectric Photometric Catalogue is a compilation of previously published photometric data. Published in 1998, the catalogue includes 63,316 stars surveyed through 1996. [51]

ZC catalogue Edit

The Robertson's Zodiacal Catalogue, collected by the astronomer James Robertson, is a catalogue of 3539 zodiacal stars brighter than 9th magnitude. It is mainly used for Star Occultations by the Moon.

Successors to USNO-A, etc Edit

Stars evolve and move over time, making catalogues evolving, impermanent databases at even the most rigorous levels of production. The USNO catalogues are the most current and widely used astrometric catalogues available at present, and include USNO products such as USNO-B (the successor to USNO-A), NOMAD, UCAC and others in production or narrowly released. Some users may see specialized catalogues (more recent versions of the above), tailored catalogues, interferometrically-produced cataloges, dynamic catalogues, and those with updated positions, motions, colors, and improved errors. Catalogue data is continually collected at the Naval Observatory dark-sky facility, NOFS and the latest refined, updated catalogues are reduced and produced by NOFS and the USNO. See the USNO Catalog and Image Servers for more information and access. [31] [52]

Big universe, big data, astronomical opportunity

Astronomical data is and has always been “big data”. Once that was only true metaphorically, now it is true in all senses. We acquire it far more rapidly than the rate at which we can process, analyse and exploit it. This means we are creating a vast global repository that may already hold answers to some of the fundamental questions of the Universe we are seeking.

Does this mean we should cancel our up-coming missions and telescopes – after all why continue to order food when the table is replete? Of course not. What it means is that, while we continue our inevitable yet budget limited advancement into the future, so we must also simultaneously do justice to the data we have already acquired.

In a small way we already doing this. Consider citizen science, where public participation in the analysis of archived data increases the possibility of real scientific discovery. It’s a natural evolution, giving those with spare time on their hands the chance to advance scientific knowledge.

However, soon this will not be sufficient. What we need is a new breed of professional astronomy data-miners eager to get their hands dirty with “old” data, with the capacity to exploit more readily the results and findings.

Thus far, human ingenuity, and current technology have ensured that data storage capabilities have kept pace with the massive output of the electronic stargazers. The real struggle is now figuring out how to search and synthesize that output.

The greatest challenges for tackling large astronomical data sets are:

  • Visualisation of astronomical datasets
  • Creation and utilisation of efficient algorithms for processing large datasets.
  • The efficient development of, and interaction with, large databases.
  • The use of “machine learning” methodologies

The challenges unique to astronomical data are borne out of the characteristics of big data. The three Vs: volume – amount of data, variety – complexity of data and the sources that it is gathered from and velocity – rate of data and information flow. It is a problem that is getting worse.

In 2004, the data I used for my Masters had been acquired in the mid-1990s by the United Kingdom Infra-Red Telescope (UKIRT), Hawaii. In total it amounted a few 10s of Gigabytes.

Moving onward just a matter of months to my PhD, I was studying data taken from one the most successful ground based surveys in the history of astronomy, the Sloan Digital Sky Survey (SDSS). The volume of data I was having to cope with was orders of magnitude more.

SDSS entered routine operations in 2000. At the time of Data Release 12 (DR12) in July 2014 the total volume of that release was 116TB. Even this pales next to the Large Synoptic Survey Telescope (LSST). Planned to enter operation in 2022, it is aiming to gather 30TB a night.

To make progress with this massive data set, astronomy must embrace a new era of data-mining techniques and technologies. These include the application of artificial intelligence, machine learning, statistics, and database systems, to extract information from a data set and transform it into an understandable structure for further use.

Now while many scientists find themselves focused on solving these issues, let’s just pull back a moment and ask the tough questions. For what purpose are we gathering all this new data? What value do we gain from just collecting it? For that matter, have we learned all that we can from the data that we have?

It seems that the original science of data, astronomy, has a lot to learn from the new kid on the block, data science. Think about it. What if, as we strive to acquire and process more photons from across the farther reaches of the universe, from ever more exotic sources with even more complex instrumentation, that somewhere in a dusty server on Earth, the answers are already here, if we would just only pick up that dataset and look at it … possibly for the first time.

Dr Maya Dillon is the community manager for Pivigo. The company supports analytical PhDs making the transition into the world of Data Science and also runs S2DS: Europe’s largest data science boot-camp.


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